1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the implementation of the scalar evolution analysis
11 // engine, which is used primarily to analyze expressions involving induction
12 // variables in loops.
14 // There are several aspects to this library. First is the representation of
15 // scalar expressions, which are represented as subclasses of the SCEV class.
16 // These classes are used to represent certain types of subexpressions that we
17 // can handle. We only create one SCEV of a particular shape, so
18 // pointer-comparisons for equality are legal.
20 // One important aspect of the SCEV objects is that they are never cyclic, even
21 // if there is a cycle in the dataflow for an expression (ie, a PHI node). If
22 // the PHI node is one of the idioms that we can represent (e.g., a polynomial
23 // recurrence) then we represent it directly as a recurrence node, otherwise we
24 // represent it as a SCEVUnknown node.
26 // In addition to being able to represent expressions of various types, we also
27 // have folders that are used to build the *canonical* representation for a
28 // particular expression. These folders are capable of using a variety of
29 // rewrite rules to simplify the expressions.
31 // Once the folders are defined, we can implement the more interesting
32 // higher-level code, such as the code that recognizes PHI nodes of various
33 // types, computes the execution count of a loop, etc.
35 // TODO: We should use these routines and value representations to implement
36 // dependence analysis!
38 //===----------------------------------------------------------------------===//
40 // There are several good references for the techniques used in this analysis.
42 // Chains of recurrences -- a method to expedite the evaluation
43 // of closed-form functions
44 // Olaf Bachmann, Paul S. Wang, Eugene V. Zima
46 // On computational properties of chains of recurrences
49 // Symbolic Evaluation of Chains of Recurrences for Loop Optimization
50 // Robert A. van Engelen
52 // Efficient Symbolic Analysis for Optimizing Compilers
53 // Robert A. van Engelen
55 // Using the chains of recurrences algebra for data dependence testing and
56 // induction variable substitution
57 // MS Thesis, Johnie Birch
59 //===----------------------------------------------------------------------===//
61 #include "llvm/Analysis/ScalarEvolution.h"
62 #include "llvm/ADT/Optional.h"
63 #include "llvm/ADT/STLExtras.h"
64 #include "llvm/ADT/SmallPtrSet.h"
65 #include "llvm/ADT/Statistic.h"
66 #include "llvm/Analysis/AssumptionTracker.h"
67 #include "llvm/Analysis/ConstantFolding.h"
68 #include "llvm/Analysis/InstructionSimplify.h"
69 #include "llvm/Analysis/LoopInfo.h"
70 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
71 #include "llvm/Analysis/ValueTracking.h"
72 #include "llvm/IR/ConstantRange.h"
73 #include "llvm/IR/Constants.h"
74 #include "llvm/IR/DataLayout.h"
75 #include "llvm/IR/DerivedTypes.h"
76 #include "llvm/IR/Dominators.h"
77 #include "llvm/IR/GetElementPtrTypeIterator.h"
78 #include "llvm/IR/GlobalAlias.h"
79 #include "llvm/IR/GlobalVariable.h"
80 #include "llvm/IR/InstIterator.h"
81 #include "llvm/IR/Instructions.h"
82 #include "llvm/IR/LLVMContext.h"
83 #include "llvm/IR/Metadata.h"
84 #include "llvm/IR/Operator.h"
85 #include "llvm/Support/CommandLine.h"
86 #include "llvm/Support/Debug.h"
87 #include "llvm/Support/ErrorHandling.h"
88 #include "llvm/Support/MathExtras.h"
89 #include "llvm/Support/raw_ostream.h"
90 #include "llvm/Target/TargetLibraryInfo.h"
94 #define DEBUG_TYPE "scalar-evolution"
96 STATISTIC(NumArrayLenItCounts,
97 "Number of trip counts computed with array length");
98 STATISTIC(NumTripCountsComputed,
99 "Number of loops with predictable loop counts");
100 STATISTIC(NumTripCountsNotComputed,
101 "Number of loops without predictable loop counts");
102 STATISTIC(NumBruteForceTripCountsComputed,
103 "Number of loops with trip counts computed by force");
105 static cl::opt<unsigned>
106 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
107 cl::desc("Maximum number of iterations SCEV will "
108 "symbolically execute a constant "
112 // FIXME: Enable this with XDEBUG when the test suite is clean.
114 VerifySCEV("verify-scev",
115 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
117 INITIALIZE_PASS_BEGIN(ScalarEvolution, "scalar-evolution",
118 "Scalar Evolution Analysis", false, true)
119 INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
120 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
121 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
122 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
123 INITIALIZE_PASS_END(ScalarEvolution, "scalar-evolution",
124 "Scalar Evolution Analysis", false, true)
125 char ScalarEvolution::ID = 0;
127 //===----------------------------------------------------------------------===//
128 // SCEV class definitions
129 //===----------------------------------------------------------------------===//
131 //===----------------------------------------------------------------------===//
132 // Implementation of the SCEV class.
135 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
136 void SCEV::dump() const {
142 void SCEV::print(raw_ostream &OS) const {
143 switch (static_cast<SCEVTypes>(getSCEVType())) {
145 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
148 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
149 const SCEV *Op = Trunc->getOperand();
150 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
151 << *Trunc->getType() << ")";
155 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
156 const SCEV *Op = ZExt->getOperand();
157 OS << "(zext " << *Op->getType() << " " << *Op << " to "
158 << *ZExt->getType() << ")";
162 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
163 const SCEV *Op = SExt->getOperand();
164 OS << "(sext " << *Op->getType() << " " << *Op << " to "
165 << *SExt->getType() << ")";
169 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
170 OS << "{" << *AR->getOperand(0);
171 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
172 OS << ",+," << *AR->getOperand(i);
174 if (AR->getNoWrapFlags(FlagNUW))
176 if (AR->getNoWrapFlags(FlagNSW))
178 if (AR->getNoWrapFlags(FlagNW) &&
179 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
181 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
189 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
190 const char *OpStr = nullptr;
191 switch (NAry->getSCEVType()) {
192 case scAddExpr: OpStr = " + "; break;
193 case scMulExpr: OpStr = " * "; break;
194 case scUMaxExpr: OpStr = " umax "; break;
195 case scSMaxExpr: OpStr = " smax "; break;
198 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
201 if (std::next(I) != E)
205 switch (NAry->getSCEVType()) {
208 if (NAry->getNoWrapFlags(FlagNUW))
210 if (NAry->getNoWrapFlags(FlagNSW))
216 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
217 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
221 const SCEVUnknown *U = cast<SCEVUnknown>(this);
223 if (U->isSizeOf(AllocTy)) {
224 OS << "sizeof(" << *AllocTy << ")";
227 if (U->isAlignOf(AllocTy)) {
228 OS << "alignof(" << *AllocTy << ")";
234 if (U->isOffsetOf(CTy, FieldNo)) {
235 OS << "offsetof(" << *CTy << ", ";
236 FieldNo->printAsOperand(OS, false);
241 // Otherwise just print it normally.
242 U->getValue()->printAsOperand(OS, false);
245 case scCouldNotCompute:
246 OS << "***COULDNOTCOMPUTE***";
249 llvm_unreachable("Unknown SCEV kind!");
252 Type *SCEV::getType() const {
253 switch (static_cast<SCEVTypes>(getSCEVType())) {
255 return cast<SCEVConstant>(this)->getType();
259 return cast<SCEVCastExpr>(this)->getType();
264 return cast<SCEVNAryExpr>(this)->getType();
266 return cast<SCEVAddExpr>(this)->getType();
268 return cast<SCEVUDivExpr>(this)->getType();
270 return cast<SCEVUnknown>(this)->getType();
271 case scCouldNotCompute:
272 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
274 llvm_unreachable("Unknown SCEV kind!");
277 bool SCEV::isZero() const {
278 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
279 return SC->getValue()->isZero();
283 bool SCEV::isOne() const {
284 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
285 return SC->getValue()->isOne();
289 bool SCEV::isAllOnesValue() const {
290 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
291 return SC->getValue()->isAllOnesValue();
295 /// isNonConstantNegative - Return true if the specified scev is negated, but
297 bool SCEV::isNonConstantNegative() const {
298 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
299 if (!Mul) return false;
301 // If there is a constant factor, it will be first.
302 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
303 if (!SC) return false;
305 // Return true if the value is negative, this matches things like (-42 * V).
306 return SC->getValue()->getValue().isNegative();
309 SCEVCouldNotCompute::SCEVCouldNotCompute() :
310 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
312 bool SCEVCouldNotCompute::classof(const SCEV *S) {
313 return S->getSCEVType() == scCouldNotCompute;
316 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
318 ID.AddInteger(scConstant);
321 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
322 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
323 UniqueSCEVs.InsertNode(S, IP);
327 const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
328 return getConstant(ConstantInt::get(getContext(), Val));
332 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
333 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
334 return getConstant(ConstantInt::get(ITy, V, isSigned));
337 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
338 unsigned SCEVTy, const SCEV *op, Type *ty)
339 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
341 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
342 const SCEV *op, Type *ty)
343 : SCEVCastExpr(ID, scTruncate, op, ty) {
344 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
345 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
346 "Cannot truncate non-integer value!");
349 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
350 const SCEV *op, Type *ty)
351 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
352 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
353 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
354 "Cannot zero extend non-integer value!");
357 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
358 const SCEV *op, Type *ty)
359 : SCEVCastExpr(ID, scSignExtend, op, ty) {
360 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
361 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
362 "Cannot sign extend non-integer value!");
365 void SCEVUnknown::deleted() {
366 // Clear this SCEVUnknown from various maps.
367 SE->forgetMemoizedResults(this);
369 // Remove this SCEVUnknown from the uniquing map.
370 SE->UniqueSCEVs.RemoveNode(this);
372 // Release the value.
376 void SCEVUnknown::allUsesReplacedWith(Value *New) {
377 // Clear this SCEVUnknown from various maps.
378 SE->forgetMemoizedResults(this);
380 // Remove this SCEVUnknown from the uniquing map.
381 SE->UniqueSCEVs.RemoveNode(this);
383 // Update this SCEVUnknown to point to the new value. This is needed
384 // because there may still be outstanding SCEVs which still point to
389 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
390 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
391 if (VCE->getOpcode() == Instruction::PtrToInt)
392 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
393 if (CE->getOpcode() == Instruction::GetElementPtr &&
394 CE->getOperand(0)->isNullValue() &&
395 CE->getNumOperands() == 2)
396 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
398 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
406 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
407 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
408 if (VCE->getOpcode() == Instruction::PtrToInt)
409 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
410 if (CE->getOpcode() == Instruction::GetElementPtr &&
411 CE->getOperand(0)->isNullValue()) {
413 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
414 if (StructType *STy = dyn_cast<StructType>(Ty))
415 if (!STy->isPacked() &&
416 CE->getNumOperands() == 3 &&
417 CE->getOperand(1)->isNullValue()) {
418 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
420 STy->getNumElements() == 2 &&
421 STy->getElementType(0)->isIntegerTy(1)) {
422 AllocTy = STy->getElementType(1);
431 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
432 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
433 if (VCE->getOpcode() == Instruction::PtrToInt)
434 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
435 if (CE->getOpcode() == Instruction::GetElementPtr &&
436 CE->getNumOperands() == 3 &&
437 CE->getOperand(0)->isNullValue() &&
438 CE->getOperand(1)->isNullValue()) {
440 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
441 // Ignore vector types here so that ScalarEvolutionExpander doesn't
442 // emit getelementptrs that index into vectors.
443 if (Ty->isStructTy() || Ty->isArrayTy()) {
445 FieldNo = CE->getOperand(2);
453 //===----------------------------------------------------------------------===//
455 //===----------------------------------------------------------------------===//
458 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
459 /// than the complexity of the RHS. This comparator is used to canonicalize
461 class SCEVComplexityCompare {
462 const LoopInfo *const LI;
464 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
466 // Return true or false if LHS is less than, or at least RHS, respectively.
467 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
468 return compare(LHS, RHS) < 0;
471 // Return negative, zero, or positive, if LHS is less than, equal to, or
472 // greater than RHS, respectively. A three-way result allows recursive
473 // comparisons to be more efficient.
474 int compare(const SCEV *LHS, const SCEV *RHS) const {
475 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
479 // Primarily, sort the SCEVs by their getSCEVType().
480 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
482 return (int)LType - (int)RType;
484 // Aside from the getSCEVType() ordering, the particular ordering
485 // isn't very important except that it's beneficial to be consistent,
486 // so that (a + b) and (b + a) don't end up as different expressions.
487 switch (static_cast<SCEVTypes>(LType)) {
489 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
490 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
492 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
493 // not as complete as it could be.
494 const Value *LV = LU->getValue(), *RV = RU->getValue();
496 // Order pointer values after integer values. This helps SCEVExpander
498 bool LIsPointer = LV->getType()->isPointerTy(),
499 RIsPointer = RV->getType()->isPointerTy();
500 if (LIsPointer != RIsPointer)
501 return (int)LIsPointer - (int)RIsPointer;
503 // Compare getValueID values.
504 unsigned LID = LV->getValueID(),
505 RID = RV->getValueID();
507 return (int)LID - (int)RID;
509 // Sort arguments by their position.
510 if (const Argument *LA = dyn_cast<Argument>(LV)) {
511 const Argument *RA = cast<Argument>(RV);
512 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
513 return (int)LArgNo - (int)RArgNo;
516 // For instructions, compare their loop depth, and their operand
517 // count. This is pretty loose.
518 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
519 const Instruction *RInst = cast<Instruction>(RV);
521 // Compare loop depths.
522 const BasicBlock *LParent = LInst->getParent(),
523 *RParent = RInst->getParent();
524 if (LParent != RParent) {
525 unsigned LDepth = LI->getLoopDepth(LParent),
526 RDepth = LI->getLoopDepth(RParent);
527 if (LDepth != RDepth)
528 return (int)LDepth - (int)RDepth;
531 // Compare the number of operands.
532 unsigned LNumOps = LInst->getNumOperands(),
533 RNumOps = RInst->getNumOperands();
534 return (int)LNumOps - (int)RNumOps;
541 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
542 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
544 // Compare constant values.
545 const APInt &LA = LC->getValue()->getValue();
546 const APInt &RA = RC->getValue()->getValue();
547 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
548 if (LBitWidth != RBitWidth)
549 return (int)LBitWidth - (int)RBitWidth;
550 return LA.ult(RA) ? -1 : 1;
554 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
555 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
557 // Compare addrec loop depths.
558 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
559 if (LLoop != RLoop) {
560 unsigned LDepth = LLoop->getLoopDepth(),
561 RDepth = RLoop->getLoopDepth();
562 if (LDepth != RDepth)
563 return (int)LDepth - (int)RDepth;
566 // Addrec complexity grows with operand count.
567 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
568 if (LNumOps != RNumOps)
569 return (int)LNumOps - (int)RNumOps;
571 // Lexicographically compare.
572 for (unsigned i = 0; i != LNumOps; ++i) {
573 long X = compare(LA->getOperand(i), RA->getOperand(i));
585 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
586 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
588 // Lexicographically compare n-ary expressions.
589 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
590 if (LNumOps != RNumOps)
591 return (int)LNumOps - (int)RNumOps;
593 for (unsigned i = 0; i != LNumOps; ++i) {
596 long X = compare(LC->getOperand(i), RC->getOperand(i));
600 return (int)LNumOps - (int)RNumOps;
604 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
605 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
607 // Lexicographically compare udiv expressions.
608 long X = compare(LC->getLHS(), RC->getLHS());
611 return compare(LC->getRHS(), RC->getRHS());
617 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
618 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
620 // Compare cast expressions by operand.
621 return compare(LC->getOperand(), RC->getOperand());
624 case scCouldNotCompute:
625 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
627 llvm_unreachable("Unknown SCEV kind!");
632 /// GroupByComplexity - Given a list of SCEV objects, order them by their
633 /// complexity, and group objects of the same complexity together by value.
634 /// When this routine is finished, we know that any duplicates in the vector are
635 /// consecutive and that complexity is monotonically increasing.
637 /// Note that we go take special precautions to ensure that we get deterministic
638 /// results from this routine. In other words, we don't want the results of
639 /// this to depend on where the addresses of various SCEV objects happened to
642 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
644 if (Ops.size() < 2) return; // Noop
645 if (Ops.size() == 2) {
646 // This is the common case, which also happens to be trivially simple.
648 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
649 if (SCEVComplexityCompare(LI)(RHS, LHS))
654 // Do the rough sort by complexity.
655 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
657 // Now that we are sorted by complexity, group elements of the same
658 // complexity. Note that this is, at worst, N^2, but the vector is likely to
659 // be extremely short in practice. Note that we take this approach because we
660 // do not want to depend on the addresses of the objects we are grouping.
661 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
662 const SCEV *S = Ops[i];
663 unsigned Complexity = S->getSCEVType();
665 // If there are any objects of the same complexity and same value as this
667 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
668 if (Ops[j] == S) { // Found a duplicate.
669 // Move it to immediately after i'th element.
670 std::swap(Ops[i+1], Ops[j]);
671 ++i; // no need to rescan it.
672 if (i == e-2) return; // Done!
678 static const APInt srem(const SCEVConstant *C1, const SCEVConstant *C2) {
679 APInt A = C1->getValue()->getValue();
680 APInt B = C2->getValue()->getValue();
681 uint32_t ABW = A.getBitWidth();
682 uint32_t BBW = B.getBitWidth();
689 return APIntOps::srem(A, B);
692 static const APInt sdiv(const SCEVConstant *C1, const SCEVConstant *C2) {
693 APInt A = C1->getValue()->getValue();
694 APInt B = C2->getValue()->getValue();
695 uint32_t ABW = A.getBitWidth();
696 uint32_t BBW = B.getBitWidth();
703 return APIntOps::sdiv(A, B);
706 static const APInt urem(const SCEVConstant *C1, const SCEVConstant *C2) {
707 APInt A = C1->getValue()->getValue();
708 APInt B = C2->getValue()->getValue();
709 uint32_t ABW = A.getBitWidth();
710 uint32_t BBW = B.getBitWidth();
717 return APIntOps::urem(A, B);
720 static const APInt udiv(const SCEVConstant *C1, const SCEVConstant *C2) {
721 APInt A = C1->getValue()->getValue();
722 APInt B = C2->getValue()->getValue();
723 uint32_t ABW = A.getBitWidth();
724 uint32_t BBW = B.getBitWidth();
731 return APIntOps::udiv(A, B);
735 struct FindSCEVSize {
737 FindSCEVSize() : Size(0) {}
739 bool follow(const SCEV *S) {
741 // Keep looking at all operands of S.
744 bool isDone() const {
750 // Returns the size of the SCEV S.
751 static inline int sizeOfSCEV(const SCEV *S) {
753 SCEVTraversal<FindSCEVSize> ST(F);
760 template <typename Derived>
761 struct SCEVDivision : public SCEVVisitor<Derived, void> {
763 // Computes the Quotient and Remainder of the division of Numerator by
765 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
766 const SCEV *Denominator, const SCEV **Quotient,
767 const SCEV **Remainder) {
768 assert(Numerator && Denominator && "Uninitialized SCEV");
770 SCEVDivision<Derived> D(SE, Numerator, Denominator);
772 // Check for the trivial case here to avoid having to check for it in the
774 if (Numerator == Denominator) {
780 if (Numerator->isZero()) {
786 // Split the Denominator when it is a product.
787 if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
789 *Quotient = Numerator;
790 for (const SCEV *Op : T->operands()) {
791 divide(SE, *Quotient, Op, &Q, &R);
794 // Bail out when the Numerator is not divisible by one of the terms of
798 *Remainder = Numerator;
807 *Quotient = D.Quotient;
808 *Remainder = D.Remainder;
811 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator, const SCEV *Denominator)
812 : SE(S), Denominator(Denominator) {
813 Zero = SE.getConstant(Denominator->getType(), 0);
814 One = SE.getConstant(Denominator->getType(), 1);
816 // By default, we don't know how to divide Expr by Denominator.
817 // Providing the default here simplifies the rest of the code.
819 Remainder = Numerator;
822 // Except in the trivial case described above, we do not know how to divide
823 // Expr by Denominator for the following functions with empty implementation.
824 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
825 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
826 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
827 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
828 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
829 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
830 void visitUnknown(const SCEVUnknown *Numerator) {}
831 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
833 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
834 const SCEV *StartQ, *StartR, *StepQ, *StepR;
835 assert(Numerator->isAffine() && "Numerator should be affine");
836 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
837 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
838 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
839 Numerator->getNoWrapFlags());
840 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
841 Numerator->getNoWrapFlags());
844 void visitAddExpr(const SCEVAddExpr *Numerator) {
845 SmallVector<const SCEV *, 2> Qs, Rs;
846 Type *Ty = Denominator->getType();
848 for (const SCEV *Op : Numerator->operands()) {
850 divide(SE, Op, Denominator, &Q, &R);
852 // Bail out if types do not match.
853 if (Ty != Q->getType() || Ty != R->getType()) {
855 Remainder = Numerator;
863 if (Qs.size() == 1) {
869 Quotient = SE.getAddExpr(Qs);
870 Remainder = SE.getAddExpr(Rs);
873 void visitMulExpr(const SCEVMulExpr *Numerator) {
874 SmallVector<const SCEV *, 2> Qs;
875 Type *Ty = Denominator->getType();
877 bool FoundDenominatorTerm = false;
878 for (const SCEV *Op : Numerator->operands()) {
879 // Bail out if types do not match.
880 if (Ty != Op->getType()) {
882 Remainder = Numerator;
886 if (FoundDenominatorTerm) {
891 // Check whether Denominator divides one of the product operands.
893 divide(SE, Op, Denominator, &Q, &R);
899 // Bail out if types do not match.
900 if (Ty != Q->getType()) {
902 Remainder = Numerator;
906 FoundDenominatorTerm = true;
910 if (FoundDenominatorTerm) {
915 Quotient = SE.getMulExpr(Qs);
919 if (!isa<SCEVUnknown>(Denominator)) {
921 Remainder = Numerator;
925 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
926 ValueToValueMap RewriteMap;
927 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
928 cast<SCEVConstant>(Zero)->getValue();
929 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
931 if (Remainder->isZero()) {
932 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
933 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
934 cast<SCEVConstant>(One)->getValue();
936 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
940 // Quotient is (Numerator - Remainder) divided by Denominator.
942 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
943 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator)) {
944 // This SCEV does not seem to simplify: fail the division here.
946 Remainder = Numerator;
949 divide(SE, Diff, Denominator, &Q, &R);
951 "(Numerator - Remainder) should evenly divide Denominator");
957 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
959 friend struct SCEVSDivision;
960 friend struct SCEVUDivision;
963 struct SCEVSDivision : public SCEVDivision<SCEVSDivision> {
964 void visitConstant(const SCEVConstant *Numerator) {
965 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
966 Quotient = SE.getConstant(sdiv(Numerator, D));
967 Remainder = SE.getConstant(srem(Numerator, D));
973 struct SCEVUDivision : public SCEVDivision<SCEVUDivision> {
974 void visitConstant(const SCEVConstant *Numerator) {
975 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
976 Quotient = SE.getConstant(udiv(Numerator, D));
977 Remainder = SE.getConstant(urem(Numerator, D));
985 //===----------------------------------------------------------------------===//
986 // Simple SCEV method implementations
987 //===----------------------------------------------------------------------===//
989 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
991 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
994 // Handle the simplest case efficiently.
996 return SE.getTruncateOrZeroExtend(It, ResultTy);
998 // We are using the following formula for BC(It, K):
1000 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
1002 // Suppose, W is the bitwidth of the return value. We must be prepared for
1003 // overflow. Hence, we must assure that the result of our computation is
1004 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
1005 // safe in modular arithmetic.
1007 // However, this code doesn't use exactly that formula; the formula it uses
1008 // is something like the following, where T is the number of factors of 2 in
1009 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
1012 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
1014 // This formula is trivially equivalent to the previous formula. However,
1015 // this formula can be implemented much more efficiently. The trick is that
1016 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
1017 // arithmetic. To do exact division in modular arithmetic, all we have
1018 // to do is multiply by the inverse. Therefore, this step can be done at
1021 // The next issue is how to safely do the division by 2^T. The way this
1022 // is done is by doing the multiplication step at a width of at least W + T
1023 // bits. This way, the bottom W+T bits of the product are accurate. Then,
1024 // when we perform the division by 2^T (which is equivalent to a right shift
1025 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
1026 // truncated out after the division by 2^T.
1028 // In comparison to just directly using the first formula, this technique
1029 // is much more efficient; using the first formula requires W * K bits,
1030 // but this formula less than W + K bits. Also, the first formula requires
1031 // a division step, whereas this formula only requires multiplies and shifts.
1033 // It doesn't matter whether the subtraction step is done in the calculation
1034 // width or the input iteration count's width; if the subtraction overflows,
1035 // the result must be zero anyway. We prefer here to do it in the width of
1036 // the induction variable because it helps a lot for certain cases; CodeGen
1037 // isn't smart enough to ignore the overflow, which leads to much less
1038 // efficient code if the width of the subtraction is wider than the native
1041 // (It's possible to not widen at all by pulling out factors of 2 before
1042 // the multiplication; for example, K=2 can be calculated as
1043 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
1044 // extra arithmetic, so it's not an obvious win, and it gets
1045 // much more complicated for K > 3.)
1047 // Protection from insane SCEVs; this bound is conservative,
1048 // but it probably doesn't matter.
1050 return SE.getCouldNotCompute();
1052 unsigned W = SE.getTypeSizeInBits(ResultTy);
1054 // Calculate K! / 2^T and T; we divide out the factors of two before
1055 // multiplying for calculating K! / 2^T to avoid overflow.
1056 // Other overflow doesn't matter because we only care about the bottom
1057 // W bits of the result.
1058 APInt OddFactorial(W, 1);
1060 for (unsigned i = 3; i <= K; ++i) {
1062 unsigned TwoFactors = Mult.countTrailingZeros();
1064 Mult = Mult.lshr(TwoFactors);
1065 OddFactorial *= Mult;
1068 // We need at least W + T bits for the multiplication step
1069 unsigned CalculationBits = W + T;
1071 // Calculate 2^T, at width T+W.
1072 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1074 // Calculate the multiplicative inverse of K! / 2^T;
1075 // this multiplication factor will perform the exact division by
1077 APInt Mod = APInt::getSignedMinValue(W+1);
1078 APInt MultiplyFactor = OddFactorial.zext(W+1);
1079 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1080 MultiplyFactor = MultiplyFactor.trunc(W);
1082 // Calculate the product, at width T+W
1083 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1085 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1086 for (unsigned i = 1; i != K; ++i) {
1087 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1088 Dividend = SE.getMulExpr(Dividend,
1089 SE.getTruncateOrZeroExtend(S, CalculationTy));
1093 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1095 // Truncate the result, and divide by K! / 2^T.
1097 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1098 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1101 /// evaluateAtIteration - Return the value of this chain of recurrences at
1102 /// the specified iteration number. We can evaluate this recurrence by
1103 /// multiplying each element in the chain by the binomial coefficient
1104 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
1106 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1108 /// where BC(It, k) stands for binomial coefficient.
1110 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1111 ScalarEvolution &SE) const {
1112 const SCEV *Result = getStart();
1113 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1114 // The computation is correct in the face of overflow provided that the
1115 // multiplication is performed _after_ the evaluation of the binomial
1117 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1118 if (isa<SCEVCouldNotCompute>(Coeff))
1121 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1126 //===----------------------------------------------------------------------===//
1127 // SCEV Expression folder implementations
1128 //===----------------------------------------------------------------------===//
1130 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1132 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
1133 "This is not a truncating conversion!");
1134 assert(isSCEVable(Ty) &&
1135 "This is not a conversion to a SCEVable type!");
1136 Ty = getEffectiveSCEVType(Ty);
1138 FoldingSetNodeID ID;
1139 ID.AddInteger(scTruncate);
1143 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1145 // Fold if the operand is constant.
1146 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1148 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1150 // trunc(trunc(x)) --> trunc(x)
1151 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1152 return getTruncateExpr(ST->getOperand(), Ty);
1154 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1155 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1156 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1158 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1159 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1160 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1162 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1163 // eliminate all the truncates.
1164 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1165 SmallVector<const SCEV *, 4> Operands;
1166 bool hasTrunc = false;
1167 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1168 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1169 hasTrunc = isa<SCEVTruncateExpr>(S);
1170 Operands.push_back(S);
1173 return getAddExpr(Operands);
1174 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1177 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1178 // eliminate all the truncates.
1179 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1180 SmallVector<const SCEV *, 4> Operands;
1181 bool hasTrunc = false;
1182 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1183 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1184 hasTrunc = isa<SCEVTruncateExpr>(S);
1185 Operands.push_back(S);
1188 return getMulExpr(Operands);
1189 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1192 // If the input value is a chrec scev, truncate the chrec's operands.
1193 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1194 SmallVector<const SCEV *, 4> Operands;
1195 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1196 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
1197 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1200 // The cast wasn't folded; create an explicit cast node. We can reuse
1201 // the existing insert position since if we get here, we won't have
1202 // made any changes which would invalidate it.
1203 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1205 UniqueSCEVs.InsertNode(S, IP);
1209 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
1211 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1212 "This is not an extending conversion!");
1213 assert(isSCEVable(Ty) &&
1214 "This is not a conversion to a SCEVable type!");
1215 Ty = getEffectiveSCEVType(Ty);
1217 // Fold if the operand is constant.
1218 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1220 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1222 // zext(zext(x)) --> zext(x)
1223 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1224 return getZeroExtendExpr(SZ->getOperand(), Ty);
1226 // Before doing any expensive analysis, check to see if we've already
1227 // computed a SCEV for this Op and Ty.
1228 FoldingSetNodeID ID;
1229 ID.AddInteger(scZeroExtend);
1233 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1235 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1236 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1237 // It's possible the bits taken off by the truncate were all zero bits. If
1238 // so, we should be able to simplify this further.
1239 const SCEV *X = ST->getOperand();
1240 ConstantRange CR = getUnsignedRange(X);
1241 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1242 unsigned NewBits = getTypeSizeInBits(Ty);
1243 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1244 CR.zextOrTrunc(NewBits)))
1245 return getTruncateOrZeroExtend(X, Ty);
1248 // If the input value is a chrec scev, and we can prove that the value
1249 // did not overflow the old, smaller, value, we can zero extend all of the
1250 // operands (often constants). This allows analysis of something like
1251 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1252 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1253 if (AR->isAffine()) {
1254 const SCEV *Start = AR->getStart();
1255 const SCEV *Step = AR->getStepRecurrence(*this);
1256 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1257 const Loop *L = AR->getLoop();
1259 // If we have special knowledge that this addrec won't overflow,
1260 // we don't need to do any further analysis.
1261 if (AR->getNoWrapFlags(SCEV::FlagNUW))
1262 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1263 getZeroExtendExpr(Step, Ty),
1264 L, AR->getNoWrapFlags());
1266 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1267 // Note that this serves two purposes: It filters out loops that are
1268 // simply not analyzable, and it covers the case where this code is
1269 // being called from within backedge-taken count analysis, such that
1270 // attempting to ask for the backedge-taken count would likely result
1271 // in infinite recursion. In the later case, the analysis code will
1272 // cope with a conservative value, and it will take care to purge
1273 // that value once it has finished.
1274 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1275 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1276 // Manually compute the final value for AR, checking for
1279 // Check whether the backedge-taken count can be losslessly casted to
1280 // the addrec's type. The count is always unsigned.
1281 const SCEV *CastedMaxBECount =
1282 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1283 const SCEV *RecastedMaxBECount =
1284 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1285 if (MaxBECount == RecastedMaxBECount) {
1286 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1287 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1288 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1289 const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul), WideTy);
1290 const SCEV *WideStart = getZeroExtendExpr(Start, WideTy);
1291 const SCEV *WideMaxBECount =
1292 getZeroExtendExpr(CastedMaxBECount, WideTy);
1293 const SCEV *OperandExtendedAdd =
1294 getAddExpr(WideStart,
1295 getMulExpr(WideMaxBECount,
1296 getZeroExtendExpr(Step, WideTy)));
1297 if (ZAdd == OperandExtendedAdd) {
1298 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1299 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1300 // Return the expression with the addrec on the outside.
1301 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1302 getZeroExtendExpr(Step, Ty),
1303 L, AR->getNoWrapFlags());
1305 // Similar to above, only this time treat the step value as signed.
1306 // This covers loops that count down.
1307 OperandExtendedAdd =
1308 getAddExpr(WideStart,
1309 getMulExpr(WideMaxBECount,
1310 getSignExtendExpr(Step, WideTy)));
1311 if (ZAdd == OperandExtendedAdd) {
1312 // Cache knowledge of AR NW, which is propagated to this AddRec.
1313 // Negative step causes unsigned wrap, but it still can't self-wrap.
1314 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1315 // Return the expression with the addrec on the outside.
1316 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1317 getSignExtendExpr(Step, Ty),
1318 L, AR->getNoWrapFlags());
1322 // If the backedge is guarded by a comparison with the pre-inc value
1323 // the addrec is safe. Also, if the entry is guarded by a comparison
1324 // with the start value and the backedge is guarded by a comparison
1325 // with the post-inc value, the addrec is safe.
1326 if (isKnownPositive(Step)) {
1327 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1328 getUnsignedRange(Step).getUnsignedMax());
1329 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1330 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1331 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1332 AR->getPostIncExpr(*this), N))) {
1333 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1334 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1335 // Return the expression with the addrec on the outside.
1336 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1337 getZeroExtendExpr(Step, Ty),
1338 L, AR->getNoWrapFlags());
1340 } else if (isKnownNegative(Step)) {
1341 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1342 getSignedRange(Step).getSignedMin());
1343 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1344 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1345 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1346 AR->getPostIncExpr(*this), N))) {
1347 // Cache knowledge of AR NW, which is propagated to this AddRec.
1348 // Negative step causes unsigned wrap, but it still can't self-wrap.
1349 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1350 // Return the expression with the addrec on the outside.
1351 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1352 getSignExtendExpr(Step, Ty),
1353 L, AR->getNoWrapFlags());
1359 // The cast wasn't folded; create an explicit cast node.
1360 // Recompute the insert position, as it may have been invalidated.
1361 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1362 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1364 UniqueSCEVs.InsertNode(S, IP);
1368 // Get the limit of a recurrence such that incrementing by Step cannot cause
1369 // signed overflow as long as the value of the recurrence within the loop does
1370 // not exceed this limit before incrementing.
1371 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1372 ICmpInst::Predicate *Pred,
1373 ScalarEvolution *SE) {
1374 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1375 if (SE->isKnownPositive(Step)) {
1376 *Pred = ICmpInst::ICMP_SLT;
1377 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1378 SE->getSignedRange(Step).getSignedMax());
1380 if (SE->isKnownNegative(Step)) {
1381 *Pred = ICmpInst::ICMP_SGT;
1382 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1383 SE->getSignedRange(Step).getSignedMin());
1388 // The recurrence AR has been shown to have no signed wrap. Typically, if we can
1389 // prove NSW for AR, then we can just as easily prove NSW for its preincrement
1390 // or postincrement sibling. This allows normalizing a sign extended AddRec as
1391 // such: {sext(Step + Start),+,Step} => {(Step + sext(Start),+,Step} As a
1392 // result, the expression "Step + sext(PreIncAR)" is congruent with
1393 // "sext(PostIncAR)"
1394 static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR,
1396 ScalarEvolution *SE) {
1397 const Loop *L = AR->getLoop();
1398 const SCEV *Start = AR->getStart();
1399 const SCEV *Step = AR->getStepRecurrence(*SE);
1401 // Check for a simple looking step prior to loop entry.
1402 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1406 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1407 // subtraction is expensive. For this purpose, perform a quick and dirty
1408 // difference, by checking for Step in the operand list.
1409 SmallVector<const SCEV *, 4> DiffOps;
1410 for (const SCEV *Op : SA->operands())
1412 DiffOps.push_back(Op);
1414 if (DiffOps.size() == SA->getNumOperands())
1417 // This is a postinc AR. Check for overflow on the preinc recurrence using the
1418 // same three conditions that getSignExtendedExpr checks.
1420 // 1. NSW flags on the step increment.
1421 const SCEV *PreStart = SE->getAddExpr(DiffOps, SA->getNoWrapFlags());
1422 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1423 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1425 if (PreAR && PreAR->getNoWrapFlags(SCEV::FlagNSW))
1428 // 2. Direct overflow check on the step operation's expression.
1429 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1430 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1431 const SCEV *OperandExtendedStart =
1432 SE->getAddExpr(SE->getSignExtendExpr(PreStart, WideTy),
1433 SE->getSignExtendExpr(Step, WideTy));
1434 if (SE->getSignExtendExpr(Start, WideTy) == OperandExtendedStart) {
1435 // Cache knowledge of PreAR NSW.
1437 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(SCEV::FlagNSW);
1438 // FIXME: this optimization needs a unit test
1439 DEBUG(dbgs() << "SCEV: untested prestart overflow check\n");
1443 // 3. Loop precondition.
1444 ICmpInst::Predicate Pred;
1445 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, SE);
1447 if (OverflowLimit &&
1448 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) {
1454 // Get the normalized sign-extended expression for this AddRec's Start.
1455 static const SCEV *getSignExtendAddRecStart(const SCEVAddRecExpr *AR,
1457 ScalarEvolution *SE) {
1458 const SCEV *PreStart = getPreStartForSignExtend(AR, Ty, SE);
1460 return SE->getSignExtendExpr(AR->getStart(), Ty);
1462 return SE->getAddExpr(SE->getSignExtendExpr(AR->getStepRecurrence(*SE), Ty),
1463 SE->getSignExtendExpr(PreStart, Ty));
1466 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1468 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1469 "This is not an extending conversion!");
1470 assert(isSCEVable(Ty) &&
1471 "This is not a conversion to a SCEVable type!");
1472 Ty = getEffectiveSCEVType(Ty);
1474 // Fold if the operand is constant.
1475 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1477 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1479 // sext(sext(x)) --> sext(x)
1480 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1481 return getSignExtendExpr(SS->getOperand(), Ty);
1483 // sext(zext(x)) --> zext(x)
1484 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1485 return getZeroExtendExpr(SZ->getOperand(), Ty);
1487 // Before doing any expensive analysis, check to see if we've already
1488 // computed a SCEV for this Op and Ty.
1489 FoldingSetNodeID ID;
1490 ID.AddInteger(scSignExtend);
1494 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1496 // If the input value is provably positive, build a zext instead.
1497 if (isKnownNonNegative(Op))
1498 return getZeroExtendExpr(Op, Ty);
1500 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1501 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1502 // It's possible the bits taken off by the truncate were all sign bits. If
1503 // so, we should be able to simplify this further.
1504 const SCEV *X = ST->getOperand();
1505 ConstantRange CR = getSignedRange(X);
1506 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1507 unsigned NewBits = getTypeSizeInBits(Ty);
1508 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1509 CR.sextOrTrunc(NewBits)))
1510 return getTruncateOrSignExtend(X, Ty);
1513 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1514 if (auto SA = dyn_cast<SCEVAddExpr>(Op)) {
1515 if (SA->getNumOperands() == 2) {
1516 auto SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1517 auto SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1519 if (auto SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1520 const APInt &C1 = SC1->getValue()->getValue();
1521 const APInt &C2 = SC2->getValue()->getValue();
1522 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1523 C2.ugt(C1) && C2.isPowerOf2())
1524 return getAddExpr(getSignExtendExpr(SC1, Ty),
1525 getSignExtendExpr(SMul, Ty));
1530 // If the input value is a chrec scev, and we can prove that the value
1531 // did not overflow the old, smaller, value, we can sign extend all of the
1532 // operands (often constants). This allows analysis of something like
1533 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1534 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1535 if (AR->isAffine()) {
1536 const SCEV *Start = AR->getStart();
1537 const SCEV *Step = AR->getStepRecurrence(*this);
1538 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1539 const Loop *L = AR->getLoop();
1541 // If we have special knowledge that this addrec won't overflow,
1542 // we don't need to do any further analysis.
1543 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1544 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1545 getSignExtendExpr(Step, Ty),
1548 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1549 // Note that this serves two purposes: It filters out loops that are
1550 // simply not analyzable, and it covers the case where this code is
1551 // being called from within backedge-taken count analysis, such that
1552 // attempting to ask for the backedge-taken count would likely result
1553 // in infinite recursion. In the later case, the analysis code will
1554 // cope with a conservative value, and it will take care to purge
1555 // that value once it has finished.
1556 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1557 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1558 // Manually compute the final value for AR, checking for
1561 // Check whether the backedge-taken count can be losslessly casted to
1562 // the addrec's type. The count is always unsigned.
1563 const SCEV *CastedMaxBECount =
1564 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1565 const SCEV *RecastedMaxBECount =
1566 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1567 if (MaxBECount == RecastedMaxBECount) {
1568 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1569 // Check whether Start+Step*MaxBECount has no signed overflow.
1570 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1571 const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul), WideTy);
1572 const SCEV *WideStart = getSignExtendExpr(Start, WideTy);
1573 const SCEV *WideMaxBECount =
1574 getZeroExtendExpr(CastedMaxBECount, WideTy);
1575 const SCEV *OperandExtendedAdd =
1576 getAddExpr(WideStart,
1577 getMulExpr(WideMaxBECount,
1578 getSignExtendExpr(Step, WideTy)));
1579 if (SAdd == OperandExtendedAdd) {
1580 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1581 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1582 // Return the expression with the addrec on the outside.
1583 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1584 getSignExtendExpr(Step, Ty),
1585 L, AR->getNoWrapFlags());
1587 // Similar to above, only this time treat the step value as unsigned.
1588 // This covers loops that count up with an unsigned step.
1589 OperandExtendedAdd =
1590 getAddExpr(WideStart,
1591 getMulExpr(WideMaxBECount,
1592 getZeroExtendExpr(Step, WideTy)));
1593 if (SAdd == OperandExtendedAdd) {
1594 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1595 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1596 // Return the expression with the addrec on the outside.
1597 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1598 getZeroExtendExpr(Step, Ty),
1599 L, AR->getNoWrapFlags());
1603 // If the backedge is guarded by a comparison with the pre-inc value
1604 // the addrec is safe. Also, if the entry is guarded by a comparison
1605 // with the start value and the backedge is guarded by a comparison
1606 // with the post-inc value, the addrec is safe.
1607 ICmpInst::Predicate Pred;
1608 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, this);
1609 if (OverflowLimit &&
1610 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1611 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1612 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1614 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1615 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1616 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1617 getSignExtendExpr(Step, Ty),
1618 L, AR->getNoWrapFlags());
1621 // If Start and Step are constants, check if we can apply this
1623 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1624 auto SC1 = dyn_cast<SCEVConstant>(Start);
1625 auto SC2 = dyn_cast<SCEVConstant>(Step);
1627 const APInt &C1 = SC1->getValue()->getValue();
1628 const APInt &C2 = SC2->getValue()->getValue();
1629 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1631 Start = getSignExtendExpr(Start, Ty);
1632 const SCEV *NewAR = getAddRecExpr(getConstant(AR->getType(), 0), Step,
1633 L, AR->getNoWrapFlags());
1634 return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
1639 // The cast wasn't folded; create an explicit cast node.
1640 // Recompute the insert position, as it may have been invalidated.
1641 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1642 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1644 UniqueSCEVs.InsertNode(S, IP);
1648 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1649 /// unspecified bits out to the given type.
1651 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1653 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1654 "This is not an extending conversion!");
1655 assert(isSCEVable(Ty) &&
1656 "This is not a conversion to a SCEVable type!");
1657 Ty = getEffectiveSCEVType(Ty);
1659 // Sign-extend negative constants.
1660 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1661 if (SC->getValue()->getValue().isNegative())
1662 return getSignExtendExpr(Op, Ty);
1664 // Peel off a truncate cast.
1665 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1666 const SCEV *NewOp = T->getOperand();
1667 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1668 return getAnyExtendExpr(NewOp, Ty);
1669 return getTruncateOrNoop(NewOp, Ty);
1672 // Next try a zext cast. If the cast is folded, use it.
1673 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1674 if (!isa<SCEVZeroExtendExpr>(ZExt))
1677 // Next try a sext cast. If the cast is folded, use it.
1678 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1679 if (!isa<SCEVSignExtendExpr>(SExt))
1682 // Force the cast to be folded into the operands of an addrec.
1683 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1684 SmallVector<const SCEV *, 4> Ops;
1685 for (const SCEV *Op : AR->operands())
1686 Ops.push_back(getAnyExtendExpr(Op, Ty));
1687 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1690 // If the expression is obviously signed, use the sext cast value.
1691 if (isa<SCEVSMaxExpr>(Op))
1694 // Absent any other information, use the zext cast value.
1698 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1699 /// a list of operands to be added under the given scale, update the given
1700 /// map. This is a helper function for getAddRecExpr. As an example of
1701 /// what it does, given a sequence of operands that would form an add
1702 /// expression like this:
1704 /// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
1706 /// where A and B are constants, update the map with these values:
1708 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1710 /// and add 13 + A*B*29 to AccumulatedConstant.
1711 /// This will allow getAddRecExpr to produce this:
1713 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1715 /// This form often exposes folding opportunities that are hidden in
1716 /// the original operand list.
1718 /// Return true iff it appears that any interesting folding opportunities
1719 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1720 /// the common case where no interesting opportunities are present, and
1721 /// is also used as a check to avoid infinite recursion.
1724 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1725 SmallVectorImpl<const SCEV *> &NewOps,
1726 APInt &AccumulatedConstant,
1727 const SCEV *const *Ops, size_t NumOperands,
1729 ScalarEvolution &SE) {
1730 bool Interesting = false;
1732 // Iterate over the add operands. They are sorted, with constants first.
1734 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1736 // Pull a buried constant out to the outside.
1737 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1739 AccumulatedConstant += Scale * C->getValue()->getValue();
1742 // Next comes everything else. We're especially interested in multiplies
1743 // here, but they're in the middle, so just visit the rest with one loop.
1744 for (; i != NumOperands; ++i) {
1745 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1746 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1748 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1749 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1750 // A multiplication of a constant with another add; recurse.
1751 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1753 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1754 Add->op_begin(), Add->getNumOperands(),
1757 // A multiplication of a constant with some other value. Update
1759 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1760 const SCEV *Key = SE.getMulExpr(MulOps);
1761 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1762 M.insert(std::make_pair(Key, NewScale));
1764 NewOps.push_back(Pair.first->first);
1766 Pair.first->second += NewScale;
1767 // The map already had an entry for this value, which may indicate
1768 // a folding opportunity.
1773 // An ordinary operand. Update the map.
1774 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1775 M.insert(std::make_pair(Ops[i], Scale));
1777 NewOps.push_back(Pair.first->first);
1779 Pair.first->second += Scale;
1780 // The map already had an entry for this value, which may indicate
1781 // a folding opportunity.
1791 struct APIntCompare {
1792 bool operator()(const APInt &LHS, const APInt &RHS) const {
1793 return LHS.ult(RHS);
1798 /// getAddExpr - Get a canonical add expression, or something simpler if
1800 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1801 SCEV::NoWrapFlags Flags) {
1802 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
1803 "only nuw or nsw allowed");
1804 assert(!Ops.empty() && "Cannot get empty add!");
1805 if (Ops.size() == 1) return Ops[0];
1807 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1808 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1809 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1810 "SCEVAddExpr operand types don't match!");
1813 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1815 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1816 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1817 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1819 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1820 E = Ops.end(); I != E; ++I)
1821 if (!isKnownNonNegative(*I)) {
1825 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1828 // Sort by complexity, this groups all similar expression types together.
1829 GroupByComplexity(Ops, LI);
1831 // If there are any constants, fold them together.
1833 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1835 assert(Idx < Ops.size());
1836 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1837 // We found two constants, fold them together!
1838 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1839 RHSC->getValue()->getValue());
1840 if (Ops.size() == 2) return Ops[0];
1841 Ops.erase(Ops.begin()+1); // Erase the folded element
1842 LHSC = cast<SCEVConstant>(Ops[0]);
1845 // If we are left with a constant zero being added, strip it off.
1846 if (LHSC->getValue()->isZero()) {
1847 Ops.erase(Ops.begin());
1851 if (Ops.size() == 1) return Ops[0];
1854 // Okay, check to see if the same value occurs in the operand list more than
1855 // once. If so, merge them together into an multiply expression. Since we
1856 // sorted the list, these values are required to be adjacent.
1857 Type *Ty = Ops[0]->getType();
1858 bool FoundMatch = false;
1859 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1860 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1861 // Scan ahead to count how many equal operands there are.
1863 while (i+Count != e && Ops[i+Count] == Ops[i])
1865 // Merge the values into a multiply.
1866 const SCEV *Scale = getConstant(Ty, Count);
1867 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1868 if (Ops.size() == Count)
1871 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1872 --i; e -= Count - 1;
1876 return getAddExpr(Ops, Flags);
1878 // Check for truncates. If all the operands are truncated from the same
1879 // type, see if factoring out the truncate would permit the result to be
1880 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1881 // if the contents of the resulting outer trunc fold to something simple.
1882 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1883 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1884 Type *DstType = Trunc->getType();
1885 Type *SrcType = Trunc->getOperand()->getType();
1886 SmallVector<const SCEV *, 8> LargeOps;
1888 // Check all the operands to see if they can be represented in the
1889 // source type of the truncate.
1890 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1891 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1892 if (T->getOperand()->getType() != SrcType) {
1896 LargeOps.push_back(T->getOperand());
1897 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1898 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1899 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1900 SmallVector<const SCEV *, 8> LargeMulOps;
1901 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1902 if (const SCEVTruncateExpr *T =
1903 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1904 if (T->getOperand()->getType() != SrcType) {
1908 LargeMulOps.push_back(T->getOperand());
1909 } else if (const SCEVConstant *C =
1910 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1911 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1918 LargeOps.push_back(getMulExpr(LargeMulOps));
1925 // Evaluate the expression in the larger type.
1926 const SCEV *Fold = getAddExpr(LargeOps, Flags);
1927 // If it folds to something simple, use it. Otherwise, don't.
1928 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1929 return getTruncateExpr(Fold, DstType);
1933 // Skip past any other cast SCEVs.
1934 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1937 // If there are add operands they would be next.
1938 if (Idx < Ops.size()) {
1939 bool DeletedAdd = false;
1940 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1941 // If we have an add, expand the add operands onto the end of the operands
1943 Ops.erase(Ops.begin()+Idx);
1944 Ops.append(Add->op_begin(), Add->op_end());
1948 // If we deleted at least one add, we added operands to the end of the list,
1949 // and they are not necessarily sorted. Recurse to resort and resimplify
1950 // any operands we just acquired.
1952 return getAddExpr(Ops);
1955 // Skip over the add expression until we get to a multiply.
1956 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1959 // Check to see if there are any folding opportunities present with
1960 // operands multiplied by constant values.
1961 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1962 uint64_t BitWidth = getTypeSizeInBits(Ty);
1963 DenseMap<const SCEV *, APInt> M;
1964 SmallVector<const SCEV *, 8> NewOps;
1965 APInt AccumulatedConstant(BitWidth, 0);
1966 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1967 Ops.data(), Ops.size(),
1968 APInt(BitWidth, 1), *this)) {
1969 // Some interesting folding opportunity is present, so its worthwhile to
1970 // re-generate the operands list. Group the operands by constant scale,
1971 // to avoid multiplying by the same constant scale multiple times.
1972 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1973 for (SmallVectorImpl<const SCEV *>::const_iterator I = NewOps.begin(),
1974 E = NewOps.end(); I != E; ++I)
1975 MulOpLists[M.find(*I)->second].push_back(*I);
1976 // Re-generate the operands list.
1978 if (AccumulatedConstant != 0)
1979 Ops.push_back(getConstant(AccumulatedConstant));
1980 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1981 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1983 Ops.push_back(getMulExpr(getConstant(I->first),
1984 getAddExpr(I->second)));
1986 return getConstant(Ty, 0);
1987 if (Ops.size() == 1)
1989 return getAddExpr(Ops);
1993 // If we are adding something to a multiply expression, make sure the
1994 // something is not already an operand of the multiply. If so, merge it into
1996 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1997 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1998 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1999 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
2000 if (isa<SCEVConstant>(MulOpSCEV))
2002 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
2003 if (MulOpSCEV == Ops[AddOp]) {
2004 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
2005 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
2006 if (Mul->getNumOperands() != 2) {
2007 // If the multiply has more than two operands, we must get the
2009 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2010 Mul->op_begin()+MulOp);
2011 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2012 InnerMul = getMulExpr(MulOps);
2014 const SCEV *One = getConstant(Ty, 1);
2015 const SCEV *AddOne = getAddExpr(One, InnerMul);
2016 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
2017 if (Ops.size() == 2) return OuterMul;
2019 Ops.erase(Ops.begin()+AddOp);
2020 Ops.erase(Ops.begin()+Idx-1);
2022 Ops.erase(Ops.begin()+Idx);
2023 Ops.erase(Ops.begin()+AddOp-1);
2025 Ops.push_back(OuterMul);
2026 return getAddExpr(Ops);
2029 // Check this multiply against other multiplies being added together.
2030 for (unsigned OtherMulIdx = Idx+1;
2031 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
2033 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
2034 // If MulOp occurs in OtherMul, we can fold the two multiplies
2036 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
2037 OMulOp != e; ++OMulOp)
2038 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
2039 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
2040 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
2041 if (Mul->getNumOperands() != 2) {
2042 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2043 Mul->op_begin()+MulOp);
2044 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2045 InnerMul1 = getMulExpr(MulOps);
2047 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2048 if (OtherMul->getNumOperands() != 2) {
2049 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2050 OtherMul->op_begin()+OMulOp);
2051 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2052 InnerMul2 = getMulExpr(MulOps);
2054 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
2055 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2056 if (Ops.size() == 2) return OuterMul;
2057 Ops.erase(Ops.begin()+Idx);
2058 Ops.erase(Ops.begin()+OtherMulIdx-1);
2059 Ops.push_back(OuterMul);
2060 return getAddExpr(Ops);
2066 // If there are any add recurrences in the operands list, see if any other
2067 // added values are loop invariant. If so, we can fold them into the
2069 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2072 // Scan over all recurrences, trying to fold loop invariants into them.
2073 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2074 // Scan all of the other operands to this add and add them to the vector if
2075 // they are loop invariant w.r.t. the recurrence.
2076 SmallVector<const SCEV *, 8> LIOps;
2077 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2078 const Loop *AddRecLoop = AddRec->getLoop();
2079 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2080 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2081 LIOps.push_back(Ops[i]);
2082 Ops.erase(Ops.begin()+i);
2086 // If we found some loop invariants, fold them into the recurrence.
2087 if (!LIOps.empty()) {
2088 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2089 LIOps.push_back(AddRec->getStart());
2091 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2093 AddRecOps[0] = getAddExpr(LIOps);
2095 // Build the new addrec. Propagate the NUW and NSW flags if both the
2096 // outer add and the inner addrec are guaranteed to have no overflow.
2097 // Always propagate NW.
2098 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2099 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2101 // If all of the other operands were loop invariant, we are done.
2102 if (Ops.size() == 1) return NewRec;
2104 // Otherwise, add the folded AddRec by the non-invariant parts.
2105 for (unsigned i = 0;; ++i)
2106 if (Ops[i] == AddRec) {
2110 return getAddExpr(Ops);
2113 // Okay, if there weren't any loop invariants to be folded, check to see if
2114 // there are multiple AddRec's with the same loop induction variable being
2115 // added together. If so, we can fold them.
2116 for (unsigned OtherIdx = Idx+1;
2117 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2119 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2120 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2121 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2123 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2125 if (const SCEVAddRecExpr *OtherAddRec =
2126 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2127 if (OtherAddRec->getLoop() == AddRecLoop) {
2128 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2130 if (i >= AddRecOps.size()) {
2131 AddRecOps.append(OtherAddRec->op_begin()+i,
2132 OtherAddRec->op_end());
2135 AddRecOps[i] = getAddExpr(AddRecOps[i],
2136 OtherAddRec->getOperand(i));
2138 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2140 // Step size has changed, so we cannot guarantee no self-wraparound.
2141 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2142 return getAddExpr(Ops);
2145 // Otherwise couldn't fold anything into this recurrence. Move onto the
2149 // Okay, it looks like we really DO need an add expr. Check to see if we
2150 // already have one, otherwise create a new one.
2151 FoldingSetNodeID ID;
2152 ID.AddInteger(scAddExpr);
2153 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2154 ID.AddPointer(Ops[i]);
2157 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2159 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2160 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2161 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
2163 UniqueSCEVs.InsertNode(S, IP);
2165 S->setNoWrapFlags(Flags);
2169 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2171 if (j > 1 && k / j != i) Overflow = true;
2175 /// Compute the result of "n choose k", the binomial coefficient. If an
2176 /// intermediate computation overflows, Overflow will be set and the return will
2177 /// be garbage. Overflow is not cleared on absence of overflow.
2178 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2179 // We use the multiplicative formula:
2180 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2181 // At each iteration, we take the n-th term of the numeral and divide by the
2182 // (k-n)th term of the denominator. This division will always produce an
2183 // integral result, and helps reduce the chance of overflow in the
2184 // intermediate computations. However, we can still overflow even when the
2185 // final result would fit.
2187 if (n == 0 || n == k) return 1;
2188 if (k > n) return 0;
2194 for (uint64_t i = 1; i <= k; ++i) {
2195 r = umul_ov(r, n-(i-1), Overflow);
2201 /// getMulExpr - Get a canonical multiply expression, or something simpler if
2203 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2204 SCEV::NoWrapFlags Flags) {
2205 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
2206 "only nuw or nsw allowed");
2207 assert(!Ops.empty() && "Cannot get empty mul!");
2208 if (Ops.size() == 1) return Ops[0];
2210 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2211 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2212 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2213 "SCEVMulExpr operand types don't match!");
2216 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2218 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2219 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2220 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2222 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
2223 E = Ops.end(); I != E; ++I)
2224 if (!isKnownNonNegative(*I)) {
2228 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2231 // Sort by complexity, this groups all similar expression types together.
2232 GroupByComplexity(Ops, LI);
2234 // If there are any constants, fold them together.
2236 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2238 // C1*(C2+V) -> C1*C2 + C1*V
2239 if (Ops.size() == 2)
2240 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2241 if (Add->getNumOperands() == 2 &&
2242 isa<SCEVConstant>(Add->getOperand(0)))
2243 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2244 getMulExpr(LHSC, Add->getOperand(1)));
2247 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2248 // We found two constants, fold them together!
2249 ConstantInt *Fold = ConstantInt::get(getContext(),
2250 LHSC->getValue()->getValue() *
2251 RHSC->getValue()->getValue());
2252 Ops[0] = getConstant(Fold);
2253 Ops.erase(Ops.begin()+1); // Erase the folded element
2254 if (Ops.size() == 1) return Ops[0];
2255 LHSC = cast<SCEVConstant>(Ops[0]);
2258 // If we are left with a constant one being multiplied, strip it off.
2259 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2260 Ops.erase(Ops.begin());
2262 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2263 // If we have a multiply of zero, it will always be zero.
2265 } else if (Ops[0]->isAllOnesValue()) {
2266 // If we have a mul by -1 of an add, try distributing the -1 among the
2268 if (Ops.size() == 2) {
2269 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2270 SmallVector<const SCEV *, 4> NewOps;
2271 bool AnyFolded = false;
2272 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
2273 E = Add->op_end(); I != E; ++I) {
2274 const SCEV *Mul = getMulExpr(Ops[0], *I);
2275 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2276 NewOps.push_back(Mul);
2279 return getAddExpr(NewOps);
2281 else if (const SCEVAddRecExpr *
2282 AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2283 // Negation preserves a recurrence's no self-wrap property.
2284 SmallVector<const SCEV *, 4> Operands;
2285 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
2286 E = AddRec->op_end(); I != E; ++I) {
2287 Operands.push_back(getMulExpr(Ops[0], *I));
2289 return getAddRecExpr(Operands, AddRec->getLoop(),
2290 AddRec->getNoWrapFlags(SCEV::FlagNW));
2295 if (Ops.size() == 1)
2299 // Skip over the add expression until we get to a multiply.
2300 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2303 // If there are mul operands inline them all into this expression.
2304 if (Idx < Ops.size()) {
2305 bool DeletedMul = false;
2306 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2307 // If we have an mul, expand the mul operands onto the end of the operands
2309 Ops.erase(Ops.begin()+Idx);
2310 Ops.append(Mul->op_begin(), Mul->op_end());
2314 // If we deleted at least one mul, we added operands to the end of the list,
2315 // and they are not necessarily sorted. Recurse to resort and resimplify
2316 // any operands we just acquired.
2318 return getMulExpr(Ops);
2321 // If there are any add recurrences in the operands list, see if any other
2322 // added values are loop invariant. If so, we can fold them into the
2324 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2327 // Scan over all recurrences, trying to fold loop invariants into them.
2328 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2329 // Scan all of the other operands to this mul and add them to the vector if
2330 // they are loop invariant w.r.t. the recurrence.
2331 SmallVector<const SCEV *, 8> LIOps;
2332 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2333 const Loop *AddRecLoop = AddRec->getLoop();
2334 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2335 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2336 LIOps.push_back(Ops[i]);
2337 Ops.erase(Ops.begin()+i);
2341 // If we found some loop invariants, fold them into the recurrence.
2342 if (!LIOps.empty()) {
2343 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2344 SmallVector<const SCEV *, 4> NewOps;
2345 NewOps.reserve(AddRec->getNumOperands());
2346 const SCEV *Scale = getMulExpr(LIOps);
2347 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2348 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2350 // Build the new addrec. Propagate the NUW and NSW flags if both the
2351 // outer mul and the inner addrec are guaranteed to have no overflow.
2353 // No self-wrap cannot be guaranteed after changing the step size, but
2354 // will be inferred if either NUW or NSW is true.
2355 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2356 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2358 // If all of the other operands were loop invariant, we are done.
2359 if (Ops.size() == 1) return NewRec;
2361 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2362 for (unsigned i = 0;; ++i)
2363 if (Ops[i] == AddRec) {
2367 return getMulExpr(Ops);
2370 // Okay, if there weren't any loop invariants to be folded, check to see if
2371 // there are multiple AddRec's with the same loop induction variable being
2372 // multiplied together. If so, we can fold them.
2374 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2375 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2376 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2377 // ]]],+,...up to x=2n}.
2378 // Note that the arguments to choose() are always integers with values
2379 // known at compile time, never SCEV objects.
2381 // The implementation avoids pointless extra computations when the two
2382 // addrec's are of different length (mathematically, it's equivalent to
2383 // an infinite stream of zeros on the right).
2384 bool OpsModified = false;
2385 for (unsigned OtherIdx = Idx+1;
2386 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2388 const SCEVAddRecExpr *OtherAddRec =
2389 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2390 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2393 bool Overflow = false;
2394 Type *Ty = AddRec->getType();
2395 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2396 SmallVector<const SCEV*, 7> AddRecOps;
2397 for (int x = 0, xe = AddRec->getNumOperands() +
2398 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2399 const SCEV *Term = getConstant(Ty, 0);
2400 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2401 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2402 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2403 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2404 z < ze && !Overflow; ++z) {
2405 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2407 if (LargerThan64Bits)
2408 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2410 Coeff = Coeff1*Coeff2;
2411 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2412 const SCEV *Term1 = AddRec->getOperand(y-z);
2413 const SCEV *Term2 = OtherAddRec->getOperand(z);
2414 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2417 AddRecOps.push_back(Term);
2420 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2422 if (Ops.size() == 2) return NewAddRec;
2423 Ops[Idx] = NewAddRec;
2424 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2426 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2432 return getMulExpr(Ops);
2434 // Otherwise couldn't fold anything into this recurrence. Move onto the
2438 // Okay, it looks like we really DO need an mul expr. Check to see if we
2439 // already have one, otherwise create a new one.
2440 FoldingSetNodeID ID;
2441 ID.AddInteger(scMulExpr);
2442 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2443 ID.AddPointer(Ops[i]);
2446 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2448 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2449 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2450 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2452 UniqueSCEVs.InsertNode(S, IP);
2454 S->setNoWrapFlags(Flags);
2458 /// getUDivExpr - Get a canonical unsigned division expression, or something
2459 /// simpler if possible.
2460 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2462 assert(getEffectiveSCEVType(LHS->getType()) ==
2463 getEffectiveSCEVType(RHS->getType()) &&
2464 "SCEVUDivExpr operand types don't match!");
2466 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2467 if (RHSC->getValue()->equalsInt(1))
2468 return LHS; // X udiv 1 --> x
2469 // If the denominator is zero, the result of the udiv is undefined. Don't
2470 // try to analyze it, because the resolution chosen here may differ from
2471 // the resolution chosen in other parts of the compiler.
2472 if (!RHSC->getValue()->isZero()) {
2473 // Determine if the division can be folded into the operands of
2475 // TODO: Generalize this to non-constants by using known-bits information.
2476 Type *Ty = LHS->getType();
2477 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2478 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2479 // For non-power-of-two values, effectively round the value up to the
2480 // nearest power of two.
2481 if (!RHSC->getValue()->getValue().isPowerOf2())
2483 IntegerType *ExtTy =
2484 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2485 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2486 if (const SCEVConstant *Step =
2487 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2488 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2489 const APInt &StepInt = Step->getValue()->getValue();
2490 const APInt &DivInt = RHSC->getValue()->getValue();
2491 if (!StepInt.urem(DivInt) &&
2492 getZeroExtendExpr(AR, ExtTy) ==
2493 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2494 getZeroExtendExpr(Step, ExtTy),
2495 AR->getLoop(), SCEV::FlagAnyWrap)) {
2496 SmallVector<const SCEV *, 4> Operands;
2497 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
2498 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
2499 return getAddRecExpr(Operands, AR->getLoop(),
2502 /// Get a canonical UDivExpr for a recurrence.
2503 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2504 // We can currently only fold X%N if X is constant.
2505 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2506 if (StartC && !DivInt.urem(StepInt) &&
2507 getZeroExtendExpr(AR, ExtTy) ==
2508 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2509 getZeroExtendExpr(Step, ExtTy),
2510 AR->getLoop(), SCEV::FlagAnyWrap)) {
2511 const APInt &StartInt = StartC->getValue()->getValue();
2512 const APInt &StartRem = StartInt.urem(StepInt);
2514 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2515 AR->getLoop(), SCEV::FlagNW);
2518 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2519 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2520 SmallVector<const SCEV *, 4> Operands;
2521 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
2522 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
2523 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2524 // Find an operand that's safely divisible.
2525 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2526 const SCEV *Op = M->getOperand(i);
2527 const SCEV *Div = getUDivExpr(Op, RHSC);
2528 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2529 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2532 return getMulExpr(Operands);
2536 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2537 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2538 SmallVector<const SCEV *, 4> Operands;
2539 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
2540 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
2541 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2543 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2544 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2545 if (isa<SCEVUDivExpr>(Op) ||
2546 getMulExpr(Op, RHS) != A->getOperand(i))
2548 Operands.push_back(Op);
2550 if (Operands.size() == A->getNumOperands())
2551 return getAddExpr(Operands);
2555 // Fold if both operands are constant.
2556 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2557 Constant *LHSCV = LHSC->getValue();
2558 Constant *RHSCV = RHSC->getValue();
2559 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2565 FoldingSetNodeID ID;
2566 ID.AddInteger(scUDivExpr);
2570 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2571 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2573 UniqueSCEVs.InsertNode(S, IP);
2577 static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2578 APInt A = C1->getValue()->getValue().abs();
2579 APInt B = C2->getValue()->getValue().abs();
2580 uint32_t ABW = A.getBitWidth();
2581 uint32_t BBW = B.getBitWidth();
2588 return APIntOps::GreatestCommonDivisor(A, B);
2591 /// getUDivExactExpr - Get a canonical unsigned division expression, or
2592 /// something simpler if possible. There is no representation for an exact udiv
2593 /// in SCEV IR, but we can attempt to remove factors from the LHS and RHS.
2594 /// We can't do this when it's not exact because the udiv may be clearing bits.
2595 const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2597 // TODO: we could try to find factors in all sorts of things, but for now we
2598 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2599 // end of this file for inspiration.
2601 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2603 return getUDivExpr(LHS, RHS);
2605 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2606 // If the mulexpr multiplies by a constant, then that constant must be the
2607 // first element of the mulexpr.
2608 if (const SCEVConstant *LHSCst =
2609 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2610 if (LHSCst == RHSCst) {
2611 SmallVector<const SCEV *, 2> Operands;
2612 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2613 return getMulExpr(Operands);
2616 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
2617 // that there's a factor provided by one of the other terms. We need to
2619 APInt Factor = gcd(LHSCst, RHSCst);
2620 if (!Factor.isIntN(1)) {
2621 LHSCst = cast<SCEVConstant>(
2622 getConstant(LHSCst->getValue()->getValue().udiv(Factor)));
2623 RHSCst = cast<SCEVConstant>(
2624 getConstant(RHSCst->getValue()->getValue().udiv(Factor)));
2625 SmallVector<const SCEV *, 2> Operands;
2626 Operands.push_back(LHSCst);
2627 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2628 LHS = getMulExpr(Operands);
2630 Mul = dyn_cast<SCEVMulExpr>(LHS);
2632 return getUDivExactExpr(LHS, RHS);
2637 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
2638 if (Mul->getOperand(i) == RHS) {
2639 SmallVector<const SCEV *, 2> Operands;
2640 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
2641 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
2642 return getMulExpr(Operands);
2646 return getUDivExpr(LHS, RHS);
2649 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2650 /// Simplify the expression as much as possible.
2651 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2653 SCEV::NoWrapFlags Flags) {
2654 SmallVector<const SCEV *, 4> Operands;
2655 Operands.push_back(Start);
2656 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2657 if (StepChrec->getLoop() == L) {
2658 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2659 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2662 Operands.push_back(Step);
2663 return getAddRecExpr(Operands, L, Flags);
2666 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2667 /// Simplify the expression as much as possible.
2669 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2670 const Loop *L, SCEV::NoWrapFlags Flags) {
2671 if (Operands.size() == 1) return Operands[0];
2673 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2674 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2675 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2676 "SCEVAddRecExpr operand types don't match!");
2677 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2678 assert(isLoopInvariant(Operands[i], L) &&
2679 "SCEVAddRecExpr operand is not loop-invariant!");
2682 if (Operands.back()->isZero()) {
2683 Operands.pop_back();
2684 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2687 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2688 // use that information to infer NUW and NSW flags. However, computing a
2689 // BE count requires calling getAddRecExpr, so we may not yet have a
2690 // meaningful BE count at this point (and if we don't, we'd be stuck
2691 // with a SCEVCouldNotCompute as the cached BE count).
2693 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2695 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2696 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2697 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2699 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2700 E = Operands.end(); I != E; ++I)
2701 if (!isKnownNonNegative(*I)) {
2705 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2708 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2709 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2710 const Loop *NestedLoop = NestedAR->getLoop();
2711 if (L->contains(NestedLoop) ?
2712 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2713 (!NestedLoop->contains(L) &&
2714 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2715 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2716 NestedAR->op_end());
2717 Operands[0] = NestedAR->getStart();
2718 // AddRecs require their operands be loop-invariant with respect to their
2719 // loops. Don't perform this transformation if it would break this
2721 bool AllInvariant = true;
2722 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2723 if (!isLoopInvariant(Operands[i], L)) {
2724 AllInvariant = false;
2728 // Create a recurrence for the outer loop with the same step size.
2730 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2731 // inner recurrence has the same property.
2732 SCEV::NoWrapFlags OuterFlags =
2733 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2735 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2736 AllInvariant = true;
2737 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2738 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2739 AllInvariant = false;
2743 // Ok, both add recurrences are valid after the transformation.
2745 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2746 // the outer recurrence has the same property.
2747 SCEV::NoWrapFlags InnerFlags =
2748 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2749 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2752 // Reset Operands to its original state.
2753 Operands[0] = NestedAR;
2757 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2758 // already have one, otherwise create a new one.
2759 FoldingSetNodeID ID;
2760 ID.AddInteger(scAddRecExpr);
2761 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2762 ID.AddPointer(Operands[i]);
2766 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2768 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2769 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2770 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2771 O, Operands.size(), L);
2772 UniqueSCEVs.InsertNode(S, IP);
2774 S->setNoWrapFlags(Flags);
2778 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2780 SmallVector<const SCEV *, 2> Ops;
2783 return getSMaxExpr(Ops);
2787 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2788 assert(!Ops.empty() && "Cannot get empty smax!");
2789 if (Ops.size() == 1) return Ops[0];
2791 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2792 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2793 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2794 "SCEVSMaxExpr operand types don't match!");
2797 // Sort by complexity, this groups all similar expression types together.
2798 GroupByComplexity(Ops, LI);
2800 // If there are any constants, fold them together.
2802 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2804 assert(Idx < Ops.size());
2805 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2806 // We found two constants, fold them together!
2807 ConstantInt *Fold = ConstantInt::get(getContext(),
2808 APIntOps::smax(LHSC->getValue()->getValue(),
2809 RHSC->getValue()->getValue()));
2810 Ops[0] = getConstant(Fold);
2811 Ops.erase(Ops.begin()+1); // Erase the folded element
2812 if (Ops.size() == 1) return Ops[0];
2813 LHSC = cast<SCEVConstant>(Ops[0]);
2816 // If we are left with a constant minimum-int, strip it off.
2817 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2818 Ops.erase(Ops.begin());
2820 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2821 // If we have an smax with a constant maximum-int, it will always be
2826 if (Ops.size() == 1) return Ops[0];
2829 // Find the first SMax
2830 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2833 // Check to see if one of the operands is an SMax. If so, expand its operands
2834 // onto our operand list, and recurse to simplify.
2835 if (Idx < Ops.size()) {
2836 bool DeletedSMax = false;
2837 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2838 Ops.erase(Ops.begin()+Idx);
2839 Ops.append(SMax->op_begin(), SMax->op_end());
2844 return getSMaxExpr(Ops);
2847 // Okay, check to see if the same value occurs in the operand list twice. If
2848 // so, delete one. Since we sorted the list, these values are required to
2850 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2851 // X smax Y smax Y --> X smax Y
2852 // X smax Y --> X, if X is always greater than Y
2853 if (Ops[i] == Ops[i+1] ||
2854 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2855 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2857 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2858 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2862 if (Ops.size() == 1) return Ops[0];
2864 assert(!Ops.empty() && "Reduced smax down to nothing!");
2866 // Okay, it looks like we really DO need an smax expr. Check to see if we
2867 // already have one, otherwise create a new one.
2868 FoldingSetNodeID ID;
2869 ID.AddInteger(scSMaxExpr);
2870 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2871 ID.AddPointer(Ops[i]);
2873 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2874 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2875 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2876 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2878 UniqueSCEVs.InsertNode(S, IP);
2882 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2884 SmallVector<const SCEV *, 2> Ops;
2887 return getUMaxExpr(Ops);
2891 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2892 assert(!Ops.empty() && "Cannot get empty umax!");
2893 if (Ops.size() == 1) return Ops[0];
2895 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2896 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2897 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2898 "SCEVUMaxExpr operand types don't match!");
2901 // Sort by complexity, this groups all similar expression types together.
2902 GroupByComplexity(Ops, LI);
2904 // If there are any constants, fold them together.
2906 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2908 assert(Idx < Ops.size());
2909 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2910 // We found two constants, fold them together!
2911 ConstantInt *Fold = ConstantInt::get(getContext(),
2912 APIntOps::umax(LHSC->getValue()->getValue(),
2913 RHSC->getValue()->getValue()));
2914 Ops[0] = getConstant(Fold);
2915 Ops.erase(Ops.begin()+1); // Erase the folded element
2916 if (Ops.size() == 1) return Ops[0];
2917 LHSC = cast<SCEVConstant>(Ops[0]);
2920 // If we are left with a constant minimum-int, strip it off.
2921 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2922 Ops.erase(Ops.begin());
2924 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2925 // If we have an umax with a constant maximum-int, it will always be
2930 if (Ops.size() == 1) return Ops[0];
2933 // Find the first UMax
2934 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2937 // Check to see if one of the operands is a UMax. If so, expand its operands
2938 // onto our operand list, and recurse to simplify.
2939 if (Idx < Ops.size()) {
2940 bool DeletedUMax = false;
2941 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2942 Ops.erase(Ops.begin()+Idx);
2943 Ops.append(UMax->op_begin(), UMax->op_end());
2948 return getUMaxExpr(Ops);
2951 // Okay, check to see if the same value occurs in the operand list twice. If
2952 // so, delete one. Since we sorted the list, these values are required to
2954 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2955 // X umax Y umax Y --> X umax Y
2956 // X umax Y --> X, if X is always greater than Y
2957 if (Ops[i] == Ops[i+1] ||
2958 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2959 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2961 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2962 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2966 if (Ops.size() == 1) return Ops[0];
2968 assert(!Ops.empty() && "Reduced umax down to nothing!");
2970 // Okay, it looks like we really DO need a umax expr. Check to see if we
2971 // already have one, otherwise create a new one.
2972 FoldingSetNodeID ID;
2973 ID.AddInteger(scUMaxExpr);
2974 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2975 ID.AddPointer(Ops[i]);
2977 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2978 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2979 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2980 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2982 UniqueSCEVs.InsertNode(S, IP);
2986 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2988 // ~smax(~x, ~y) == smin(x, y).
2989 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2992 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2994 // ~umax(~x, ~y) == umin(x, y)
2995 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2998 const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
2999 // If we have DataLayout, we can bypass creating a target-independent
3000 // constant expression and then folding it back into a ConstantInt.
3001 // This is just a compile-time optimization.
3003 return getConstant(IntTy, DL->getTypeAllocSize(AllocTy));
3005 Constant *C = ConstantExpr::getSizeOf(AllocTy);
3006 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
3007 if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
3009 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
3010 assert(Ty == IntTy && "Effective SCEV type doesn't match");
3011 return getTruncateOrZeroExtend(getSCEV(C), Ty);
3014 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
3017 // If we have DataLayout, we can bypass creating a target-independent
3018 // constant expression and then folding it back into a ConstantInt.
3019 // This is just a compile-time optimization.
3021 return getConstant(IntTy,
3022 DL->getStructLayout(STy)->getElementOffset(FieldNo));
3025 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
3026 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
3027 if (Constant *Folded = ConstantFoldConstantExpression(CE, DL, TLI))
3030 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
3031 return getTruncateOrZeroExtend(getSCEV(C), Ty);
3034 const SCEV *ScalarEvolution::getUnknown(Value *V) {
3035 // Don't attempt to do anything other than create a SCEVUnknown object
3036 // here. createSCEV only calls getUnknown after checking for all other
3037 // interesting possibilities, and any other code that calls getUnknown
3038 // is doing so in order to hide a value from SCEV canonicalization.
3040 FoldingSetNodeID ID;
3041 ID.AddInteger(scUnknown);
3044 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3045 assert(cast<SCEVUnknown>(S)->getValue() == V &&
3046 "Stale SCEVUnknown in uniquing map!");
3049 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3051 FirstUnknown = cast<SCEVUnknown>(S);
3052 UniqueSCEVs.InsertNode(S, IP);
3056 //===----------------------------------------------------------------------===//
3057 // Basic SCEV Analysis and PHI Idiom Recognition Code
3060 /// isSCEVable - Test if values of the given type are analyzable within
3061 /// the SCEV framework. This primarily includes integer types, and it
3062 /// can optionally include pointer types if the ScalarEvolution class
3063 /// has access to target-specific information.
3064 bool ScalarEvolution::isSCEVable(Type *Ty) const {
3065 // Integers and pointers are always SCEVable.
3066 return Ty->isIntegerTy() || Ty->isPointerTy();
3069 /// getTypeSizeInBits - Return the size in bits of the specified type,
3070 /// for which isSCEVable must return true.
3071 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3072 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3074 // If we have a DataLayout, use it!
3076 return DL->getTypeSizeInBits(Ty);
3078 // Integer types have fixed sizes.
3079 if (Ty->isIntegerTy())
3080 return Ty->getPrimitiveSizeInBits();
3082 // The only other support type is pointer. Without DataLayout, conservatively
3083 // assume pointers are 64-bit.
3084 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
3088 /// getEffectiveSCEVType - Return a type with the same bitwidth as
3089 /// the given type and which represents how SCEV will treat the given
3090 /// type, for which isSCEVable must return true. For pointer types,
3091 /// this is the pointer-sized integer type.
3092 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3093 assert(isSCEVable(Ty) && "Type is not SCEVable!");
3095 if (Ty->isIntegerTy()) {
3099 // The only other support type is pointer.
3100 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
3103 return DL->getIntPtrType(Ty);
3105 // Without DataLayout, conservatively assume pointers are 64-bit.
3106 return Type::getInt64Ty(getContext());
3109 const SCEV *ScalarEvolution::getCouldNotCompute() {
3110 return &CouldNotCompute;
3114 // Helper class working with SCEVTraversal to figure out if a SCEV contains
3115 // a SCEVUnknown with null value-pointer. FindInvalidSCEVUnknown::FindOne
3116 // is set iff if find such SCEVUnknown.
3118 struct FindInvalidSCEVUnknown {
3120 FindInvalidSCEVUnknown() { FindOne = false; }
3121 bool follow(const SCEV *S) {
3122 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
3126 if (!cast<SCEVUnknown>(S)->getValue())
3133 bool isDone() const { return FindOne; }
3137 bool ScalarEvolution::checkValidity(const SCEV *S) const {
3138 FindInvalidSCEVUnknown F;
3139 SCEVTraversal<FindInvalidSCEVUnknown> ST(F);
3145 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
3146 /// expression and create a new one.
3147 const SCEV *ScalarEvolution::getSCEV(Value *V) {
3148 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
3150 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3151 if (I != ValueExprMap.end()) {
3152 const SCEV *S = I->second;
3153 if (checkValidity(S))
3156 ValueExprMap.erase(I);
3158 const SCEV *S = createSCEV(V);
3160 // The process of creating a SCEV for V may have caused other SCEVs
3161 // to have been created, so it's necessary to insert the new entry
3162 // from scratch, rather than trying to remember the insert position
3164 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
3168 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
3170 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
3171 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3173 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3175 Type *Ty = V->getType();
3176 Ty = getEffectiveSCEVType(Ty);
3177 return getMulExpr(V,
3178 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
3181 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
3182 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3183 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3185 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3187 Type *Ty = V->getType();
3188 Ty = getEffectiveSCEVType(Ty);
3189 const SCEV *AllOnes =
3190 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3191 return getMinusSCEV(AllOnes, V);
3194 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
3195 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3196 SCEV::NoWrapFlags Flags) {
3197 assert(!maskFlags(Flags, SCEV::FlagNUW) && "subtraction does not have NUW");
3199 // Fast path: X - X --> 0.
3201 return getConstant(LHS->getType(), 0);
3204 return getAddExpr(LHS, getNegativeSCEV(RHS), Flags);
3207 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
3208 /// input value to the specified type. If the type must be extended, it is zero
3211 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3212 Type *SrcTy = V->getType();
3213 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3214 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3215 "Cannot truncate or zero extend with non-integer arguments!");
3216 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3217 return V; // No conversion
3218 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3219 return getTruncateExpr(V, Ty);
3220 return getZeroExtendExpr(V, Ty);
3223 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
3224 /// input value to the specified type. If the type must be extended, it is sign
3227 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3229 Type *SrcTy = V->getType();
3230 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3231 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3232 "Cannot truncate or zero extend with non-integer arguments!");
3233 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3234 return V; // No conversion
3235 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3236 return getTruncateExpr(V, Ty);
3237 return getSignExtendExpr(V, Ty);
3240 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
3241 /// input value to the specified type. If the type must be extended, it is zero
3242 /// extended. The conversion must not be narrowing.
3244 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3245 Type *SrcTy = V->getType();
3246 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3247 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3248 "Cannot noop or zero extend with non-integer arguments!");
3249 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3250 "getNoopOrZeroExtend cannot truncate!");
3251 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3252 return V; // No conversion
3253 return getZeroExtendExpr(V, Ty);
3256 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
3257 /// input value to the specified type. If the type must be extended, it is sign
3258 /// extended. The conversion must not be narrowing.
3260 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3261 Type *SrcTy = V->getType();
3262 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3263 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3264 "Cannot noop or sign extend with non-integer arguments!");
3265 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3266 "getNoopOrSignExtend cannot truncate!");
3267 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3268 return V; // No conversion
3269 return getSignExtendExpr(V, Ty);
3272 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
3273 /// the input value to the specified type. If the type must be extended,
3274 /// it is extended with unspecified bits. The conversion must not be
3277 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3278 Type *SrcTy = V->getType();
3279 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3280 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3281 "Cannot noop or any extend with non-integer arguments!");
3282 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
3283 "getNoopOrAnyExtend cannot truncate!");
3284 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3285 return V; // No conversion
3286 return getAnyExtendExpr(V, Ty);
3289 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
3290 /// input value to the specified type. The conversion must not be widening.
3292 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3293 Type *SrcTy = V->getType();
3294 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
3295 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
3296 "Cannot truncate or noop with non-integer arguments!");
3297 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
3298 "getTruncateOrNoop cannot extend!");
3299 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3300 return V; // No conversion
3301 return getTruncateExpr(V, Ty);
3304 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
3305 /// the types using zero-extension, and then perform a umax operation
3307 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3309 const SCEV *PromotedLHS = LHS;
3310 const SCEV *PromotedRHS = RHS;
3312 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3313 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3315 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3317 return getUMaxExpr(PromotedLHS, PromotedRHS);
3320 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
3321 /// the types using zero-extension, and then perform a umin operation
3323 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3325 const SCEV *PromotedLHS = LHS;
3326 const SCEV *PromotedRHS = RHS;
3328 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3329 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3331 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3333 return getUMinExpr(PromotedLHS, PromotedRHS);
3336 /// getPointerBase - Transitively follow the chain of pointer-type operands
3337 /// until reaching a SCEV that does not have a single pointer operand. This
3338 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
3339 /// but corner cases do exist.
3340 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3341 // A pointer operand may evaluate to a nonpointer expression, such as null.
3342 if (!V->getType()->isPointerTy())
3345 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3346 return getPointerBase(Cast->getOperand());
3348 else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3349 const SCEV *PtrOp = nullptr;
3350 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
3352 if ((*I)->getType()->isPointerTy()) {
3353 // Cannot find the base of an expression with multiple pointer operands.
3361 return getPointerBase(PtrOp);
3366 /// PushDefUseChildren - Push users of the given Instruction
3367 /// onto the given Worklist.
3369 PushDefUseChildren(Instruction *I,
3370 SmallVectorImpl<Instruction *> &Worklist) {
3371 // Push the def-use children onto the Worklist stack.
3372 for (User *U : I->users())
3373 Worklist.push_back(cast<Instruction>(U));
3376 /// ForgetSymbolicValue - This looks up computed SCEV values for all
3377 /// instructions that depend on the given instruction and removes them from
3378 /// the ValueExprMapType map if they reference SymName. This is used during PHI
3381 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3382 SmallVector<Instruction *, 16> Worklist;
3383 PushDefUseChildren(PN, Worklist);
3385 SmallPtrSet<Instruction *, 8> Visited;
3387 while (!Worklist.empty()) {
3388 Instruction *I = Worklist.pop_back_val();
3389 if (!Visited.insert(I)) continue;
3391 ValueExprMapType::iterator It =
3392 ValueExprMap.find_as(static_cast<Value *>(I));
3393 if (It != ValueExprMap.end()) {
3394 const SCEV *Old = It->second;
3396 // Short-circuit the def-use traversal if the symbolic name
3397 // ceases to appear in expressions.
3398 if (Old != SymName && !hasOperand(Old, SymName))
3401 // SCEVUnknown for a PHI either means that it has an unrecognized
3402 // structure, it's a PHI that's in the progress of being computed
3403 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3404 // additional loop trip count information isn't going to change anything.
3405 // In the second case, createNodeForPHI will perform the necessary
3406 // updates on its own when it gets to that point. In the third, we do
3407 // want to forget the SCEVUnknown.
3408 if (!isa<PHINode>(I) ||
3409 !isa<SCEVUnknown>(Old) ||
3410 (I != PN && Old == SymName)) {
3411 forgetMemoizedResults(Old);
3412 ValueExprMap.erase(It);
3416 PushDefUseChildren(I, Worklist);
3420 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
3421 /// a loop header, making it a potential recurrence, or it doesn't.
3423 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
3424 if (const Loop *L = LI->getLoopFor(PN->getParent()))
3425 if (L->getHeader() == PN->getParent()) {
3426 // The loop may have multiple entrances or multiple exits; we can analyze
3427 // this phi as an addrec if it has a unique entry value and a unique
3429 Value *BEValueV = nullptr, *StartValueV = nullptr;
3430 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
3431 Value *V = PN->getIncomingValue(i);
3432 if (L->contains(PN->getIncomingBlock(i))) {
3435 } else if (BEValueV != V) {
3439 } else if (!StartValueV) {
3441 } else if (StartValueV != V) {
3442 StartValueV = nullptr;
3446 if (BEValueV && StartValueV) {
3447 // While we are analyzing this PHI node, handle its value symbolically.
3448 const SCEV *SymbolicName = getUnknown(PN);
3449 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&
3450 "PHI node already processed?");
3451 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
3453 // Using this symbolic name for the PHI, analyze the value coming around
3455 const SCEV *BEValue = getSCEV(BEValueV);
3457 // NOTE: If BEValue is loop invariant, we know that the PHI node just
3458 // has a special value for the first iteration of the loop.
3460 // If the value coming around the backedge is an add with the symbolic
3461 // value we just inserted, then we found a simple induction variable!
3462 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
3463 // If there is a single occurrence of the symbolic value, replace it
3464 // with a recurrence.
3465 unsigned FoundIndex = Add->getNumOperands();
3466 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3467 if (Add->getOperand(i) == SymbolicName)
3468 if (FoundIndex == e) {
3473 if (FoundIndex != Add->getNumOperands()) {
3474 // Create an add with everything but the specified operand.
3475 SmallVector<const SCEV *, 8> Ops;
3476 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3477 if (i != FoundIndex)
3478 Ops.push_back(Add->getOperand(i));
3479 const SCEV *Accum = getAddExpr(Ops);
3481 // This is not a valid addrec if the step amount is varying each
3482 // loop iteration, but is not itself an addrec in this loop.
3483 if (isLoopInvariant(Accum, L) ||
3484 (isa<SCEVAddRecExpr>(Accum) &&
3485 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
3486 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3488 // If the increment doesn't overflow, then neither the addrec nor
3489 // the post-increment will overflow.
3490 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
3491 if (OBO->hasNoUnsignedWrap())
3492 Flags = setFlags(Flags, SCEV::FlagNUW);
3493 if (OBO->hasNoSignedWrap())
3494 Flags = setFlags(Flags, SCEV::FlagNSW);
3495 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
3496 // If the increment is an inbounds GEP, then we know the address
3497 // space cannot be wrapped around. We cannot make any guarantee
3498 // about signed or unsigned overflow because pointers are
3499 // unsigned but we may have a negative index from the base
3500 // pointer. We can guarantee that no unsigned wrap occurs if the
3501 // indices form a positive value.
3502 if (GEP->isInBounds()) {
3503 Flags = setFlags(Flags, SCEV::FlagNW);
3505 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
3506 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
3507 Flags = setFlags(Flags, SCEV::FlagNUW);
3509 } else if (const SubOperator *OBO =
3510 dyn_cast<SubOperator>(BEValueV)) {
3511 if (OBO->hasNoUnsignedWrap())
3512 Flags = setFlags(Flags, SCEV::FlagNUW);
3513 if (OBO->hasNoSignedWrap())
3514 Flags = setFlags(Flags, SCEV::FlagNSW);
3517 const SCEV *StartVal = getSCEV(StartValueV);
3518 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
3520 // Since the no-wrap flags are on the increment, they apply to the
3521 // post-incremented value as well.
3522 if (isLoopInvariant(Accum, L))
3523 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
3526 // Okay, for the entire analysis of this edge we assumed the PHI
3527 // to be symbolic. We now need to go back and purge all of the
3528 // entries for the scalars that use the symbolic expression.
3529 ForgetSymbolicName(PN, SymbolicName);
3530 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3534 } else if (const SCEVAddRecExpr *AddRec =
3535 dyn_cast<SCEVAddRecExpr>(BEValue)) {
3536 // Otherwise, this could be a loop like this:
3537 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
3538 // In this case, j = {1,+,1} and BEValue is j.
3539 // Because the other in-value of i (0) fits the evolution of BEValue
3540 // i really is an addrec evolution.
3541 if (AddRec->getLoop() == L && AddRec->isAffine()) {
3542 const SCEV *StartVal = getSCEV(StartValueV);
3544 // If StartVal = j.start - j.stride, we can use StartVal as the
3545 // initial step of the addrec evolution.
3546 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
3547 AddRec->getOperand(1))) {
3548 // FIXME: For constant StartVal, we should be able to infer
3550 const SCEV *PHISCEV =
3551 getAddRecExpr(StartVal, AddRec->getOperand(1), L,
3554 // Okay, for the entire analysis of this edge we assumed the PHI
3555 // to be symbolic. We now need to go back and purge all of the
3556 // entries for the scalars that use the symbolic expression.
3557 ForgetSymbolicName(PN, SymbolicName);
3558 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3566 // If the PHI has a single incoming value, follow that value, unless the
3567 // PHI's incoming blocks are in a different loop, in which case doing so
3568 // risks breaking LCSSA form. Instcombine would normally zap these, but
3569 // it doesn't have DominatorTree information, so it may miss cases.
3570 if (Value *V = SimplifyInstruction(PN, DL, TLI, DT, AT))
3571 if (LI->replacementPreservesLCSSAForm(PN, V))
3574 // If it's not a loop phi, we can't handle it yet.
3575 return getUnknown(PN);
3578 /// createNodeForGEP - Expand GEP instructions into add and multiply
3579 /// operations. This allows them to be analyzed by regular SCEV code.
3581 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
3582 Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
3583 Value *Base = GEP->getOperand(0);
3584 // Don't attempt to analyze GEPs over unsized objects.
3585 if (!Base->getType()->getPointerElementType()->isSized())
3586 return getUnknown(GEP);
3588 // Don't blindly transfer the inbounds flag from the GEP instruction to the
3589 // Add expression, because the Instruction may be guarded by control flow
3590 // and the no-overflow bits may not be valid for the expression in any
3592 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3594 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
3595 gep_type_iterator GTI = gep_type_begin(GEP);
3596 for (GetElementPtrInst::op_iterator I = std::next(GEP->op_begin()),
3600 // Compute the (potentially symbolic) offset in bytes for this index.
3601 if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
3602 // For a struct, add the member offset.
3603 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
3604 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
3606 // Add the field offset to the running total offset.
3607 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3609 // For an array, add the element offset, explicitly scaled.
3610 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, *GTI);
3611 const SCEV *IndexS = getSCEV(Index);
3612 // Getelementptr indices are signed.
3613 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
3615 // Multiply the index by the element size to compute the element offset.
3616 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize, Wrap);
3618 // Add the element offset to the running total offset.
3619 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3623 // Get the SCEV for the GEP base.
3624 const SCEV *BaseS = getSCEV(Base);
3626 // Add the total offset from all the GEP indices to the base.
3627 return getAddExpr(BaseS, TotalOffset, Wrap);
3630 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
3631 /// guaranteed to end in (at every loop iteration). It is, at the same time,
3632 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
3633 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
3635 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
3636 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3637 return C->getValue()->getValue().countTrailingZeros();
3639 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
3640 return std::min(GetMinTrailingZeros(T->getOperand()),
3641 (uint32_t)getTypeSizeInBits(T->getType()));
3643 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
3644 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3645 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3646 getTypeSizeInBits(E->getType()) : OpRes;
3649 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
3650 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3651 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3652 getTypeSizeInBits(E->getType()) : OpRes;
3655 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
3656 // The result is the min of all operands results.
3657 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3658 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3659 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3663 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
3664 // The result is the sum of all operands results.
3665 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
3666 uint32_t BitWidth = getTypeSizeInBits(M->getType());
3667 for (unsigned i = 1, e = M->getNumOperands();
3668 SumOpRes != BitWidth && i != e; ++i)
3669 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
3674 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
3675 // The result is the min of all operands results.
3676 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3677 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3678 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3682 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
3683 // The result is the min of all operands results.
3684 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3685 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3686 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3690 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
3691 // The result is the min of all operands results.
3692 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3693 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3694 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3698 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3699 // For a SCEVUnknown, ask ValueTracking.
3700 unsigned BitWidth = getTypeSizeInBits(U->getType());
3701 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3702 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
3703 return Zeros.countTrailingOnes();
3710 /// GetRangeFromMetadata - Helper method to assign a range to V from
3711 /// metadata present in the IR.
3712 static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
3713 if (Instruction *I = dyn_cast<Instruction>(V)) {
3714 if (MDNode *MD = I->getMetadata(LLVMContext::MD_range)) {
3715 ConstantRange TotalRange(
3716 cast<IntegerType>(I->getType())->getBitWidth(), false);
3718 unsigned NumRanges = MD->getNumOperands() / 2;
3719 assert(NumRanges >= 1);
3721 for (unsigned i = 0; i < NumRanges; ++i) {
3722 ConstantInt *Lower = cast<ConstantInt>(MD->getOperand(2*i + 0));
3723 ConstantInt *Upper = cast<ConstantInt>(MD->getOperand(2*i + 1));
3724 ConstantRange Range(Lower->getValue(), Upper->getValue());
3725 TotalRange = TotalRange.unionWith(Range);
3735 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
3738 ScalarEvolution::getUnsignedRange(const SCEV *S) {
3739 // See if we've computed this range already.
3740 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
3741 if (I != UnsignedRanges.end())
3744 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3745 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
3747 unsigned BitWidth = getTypeSizeInBits(S->getType());
3748 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3750 // If the value has known zeros, the maximum unsigned value will have those
3751 // known zeros as well.
3752 uint32_t TZ = GetMinTrailingZeros(S);
3754 ConservativeResult =
3755 ConstantRange(APInt::getMinValue(BitWidth),
3756 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3758 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3759 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3760 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3761 X = X.add(getUnsignedRange(Add->getOperand(i)));
3762 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3765 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3766 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3767 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3768 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3769 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3772 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3773 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3774 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3775 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3776 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3779 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3780 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3781 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3782 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3783 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3786 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3787 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3788 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3789 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3792 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3793 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3794 return setUnsignedRange(ZExt,
3795 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3798 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3799 ConstantRange X = getUnsignedRange(SExt->getOperand());
3800 return setUnsignedRange(SExt,
3801 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3804 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3805 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3806 return setUnsignedRange(Trunc,
3807 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3810 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3811 // If there's no unsigned wrap, the value will never be less than its
3813 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
3814 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3815 if (!C->getValue()->isZero())
3816 ConservativeResult =
3817 ConservativeResult.intersectWith(
3818 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3820 // TODO: non-affine addrec
3821 if (AddRec->isAffine()) {
3822 Type *Ty = AddRec->getType();
3823 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3824 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3825 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3826 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3828 const SCEV *Start = AddRec->getStart();
3829 const SCEV *Step = AddRec->getStepRecurrence(*this);
3831 ConstantRange StartRange = getUnsignedRange(Start);
3832 ConstantRange StepRange = getSignedRange(Step);
3833 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3834 ConstantRange EndRange =
3835 StartRange.add(MaxBECountRange.multiply(StepRange));
3837 // Check for overflow. This must be done with ConstantRange arithmetic
3838 // because we could be called from within the ScalarEvolution overflow
3840 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3841 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3842 ConstantRange ExtMaxBECountRange =
3843 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3844 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3845 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3847 return setUnsignedRange(AddRec, ConservativeResult);
3849 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3850 EndRange.getUnsignedMin());
3851 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3852 EndRange.getUnsignedMax());
3853 if (Min.isMinValue() && Max.isMaxValue())
3854 return setUnsignedRange(AddRec, ConservativeResult);
3855 return setUnsignedRange(AddRec,
3856 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3860 return setUnsignedRange(AddRec, ConservativeResult);
3863 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3864 // Check if the IR explicitly contains !range metadata.
3865 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
3866 if (MDRange.hasValue())
3867 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
3869 // For a SCEVUnknown, ask ValueTracking.
3870 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3871 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, AT, nullptr, DT);
3872 if (Ones == ~Zeros + 1)
3873 return setUnsignedRange(U, ConservativeResult);
3874 return setUnsignedRange(U,
3875 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3878 return setUnsignedRange(S, ConservativeResult);
3881 /// getSignedRange - Determine the signed range for a particular SCEV.
3884 ScalarEvolution::getSignedRange(const SCEV *S) {
3885 // See if we've computed this range already.
3886 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3887 if (I != SignedRanges.end())
3890 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3891 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3893 unsigned BitWidth = getTypeSizeInBits(S->getType());
3894 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3896 // If the value has known zeros, the maximum signed value will have those
3897 // known zeros as well.
3898 uint32_t TZ = GetMinTrailingZeros(S);
3900 ConservativeResult =
3901 ConstantRange(APInt::getSignedMinValue(BitWidth),
3902 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3904 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3905 ConstantRange X = getSignedRange(Add->getOperand(0));
3906 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3907 X = X.add(getSignedRange(Add->getOperand(i)));
3908 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3911 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3912 ConstantRange X = getSignedRange(Mul->getOperand(0));
3913 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3914 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3915 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3918 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3919 ConstantRange X = getSignedRange(SMax->getOperand(0));
3920 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3921 X = X.smax(getSignedRange(SMax->getOperand(i)));
3922 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3925 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3926 ConstantRange X = getSignedRange(UMax->getOperand(0));
3927 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3928 X = X.umax(getSignedRange(UMax->getOperand(i)));
3929 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3932 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3933 ConstantRange X = getSignedRange(UDiv->getLHS());
3934 ConstantRange Y = getSignedRange(UDiv->getRHS());
3935 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3938 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3939 ConstantRange X = getSignedRange(ZExt->getOperand());
3940 return setSignedRange(ZExt,
3941 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3944 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3945 ConstantRange X = getSignedRange(SExt->getOperand());
3946 return setSignedRange(SExt,
3947 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3950 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3951 ConstantRange X = getSignedRange(Trunc->getOperand());
3952 return setSignedRange(Trunc,
3953 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3956 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3957 // If there's no signed wrap, and all the operands have the same sign or
3958 // zero, the value won't ever change sign.
3959 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
3960 bool AllNonNeg = true;
3961 bool AllNonPos = true;
3962 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3963 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3964 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3967 ConservativeResult = ConservativeResult.intersectWith(
3968 ConstantRange(APInt(BitWidth, 0),
3969 APInt::getSignedMinValue(BitWidth)));
3971 ConservativeResult = ConservativeResult.intersectWith(
3972 ConstantRange(APInt::getSignedMinValue(BitWidth),
3973 APInt(BitWidth, 1)));
3976 // TODO: non-affine addrec
3977 if (AddRec->isAffine()) {
3978 Type *Ty = AddRec->getType();
3979 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3980 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3981 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3982 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3984 const SCEV *Start = AddRec->getStart();
3985 const SCEV *Step = AddRec->getStepRecurrence(*this);
3987 ConstantRange StartRange = getSignedRange(Start);
3988 ConstantRange StepRange = getSignedRange(Step);
3989 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3990 ConstantRange EndRange =
3991 StartRange.add(MaxBECountRange.multiply(StepRange));
3993 // Check for overflow. This must be done with ConstantRange arithmetic
3994 // because we could be called from within the ScalarEvolution overflow
3996 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3997 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3998 ConstantRange ExtMaxBECountRange =
3999 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
4000 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
4001 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
4003 return setSignedRange(AddRec, ConservativeResult);
4005 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
4006 EndRange.getSignedMin());
4007 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
4008 EndRange.getSignedMax());
4009 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
4010 return setSignedRange(AddRec, ConservativeResult);
4011 return setSignedRange(AddRec,
4012 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
4016 return setSignedRange(AddRec, ConservativeResult);
4019 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4020 // Check if the IR explicitly contains !range metadata.
4021 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
4022 if (MDRange.hasValue())
4023 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
4025 // For a SCEVUnknown, ask ValueTracking.
4026 if (!U->getValue()->getType()->isIntegerTy() && !DL)
4027 return setSignedRange(U, ConservativeResult);
4028 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, AT, nullptr, DT);
4030 return setSignedRange(U, ConservativeResult);
4031 return setSignedRange(U, ConservativeResult.intersectWith(
4032 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
4033 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
4036 return setSignedRange(S, ConservativeResult);
4039 /// createSCEV - We know that there is no SCEV for the specified value.
4040 /// Analyze the expression.
4042 const SCEV *ScalarEvolution::createSCEV(Value *V) {
4043 if (!isSCEVable(V->getType()))
4044 return getUnknown(V);
4046 unsigned Opcode = Instruction::UserOp1;
4047 if (Instruction *I = dyn_cast<Instruction>(V)) {
4048 Opcode = I->getOpcode();
4050 // Don't attempt to analyze instructions in blocks that aren't
4051 // reachable. Such instructions don't matter, and they aren't required
4052 // to obey basic rules for definitions dominating uses which this
4053 // analysis depends on.
4054 if (!DT->isReachableFromEntry(I->getParent()))
4055 return getUnknown(V);
4056 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
4057 Opcode = CE->getOpcode();
4058 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
4059 return getConstant(CI);
4060 else if (isa<ConstantPointerNull>(V))
4061 return getConstant(V->getType(), 0);
4062 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
4063 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
4065 return getUnknown(V);
4067 Operator *U = cast<Operator>(V);
4069 case Instruction::Add: {
4070 // The simple thing to do would be to just call getSCEV on both operands
4071 // and call getAddExpr with the result. However if we're looking at a
4072 // bunch of things all added together, this can be quite inefficient,
4073 // because it leads to N-1 getAddExpr calls for N ultimate operands.
4074 // Instead, gather up all the operands and make a single getAddExpr call.
4075 // LLVM IR canonical form means we need only traverse the left operands.
4077 // Don't apply this instruction's NSW or NUW flags to the new
4078 // expression. The instruction may be guarded by control flow that the
4079 // no-wrap behavior depends on. Non-control-equivalent instructions can be
4080 // mapped to the same SCEV expression, and it would be incorrect to transfer
4081 // NSW/NUW semantics to those operations.
4082 SmallVector<const SCEV *, 4> AddOps;
4083 AddOps.push_back(getSCEV(U->getOperand(1)));
4084 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
4085 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
4086 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
4088 U = cast<Operator>(Op);
4089 const SCEV *Op1 = getSCEV(U->getOperand(1));
4090 if (Opcode == Instruction::Sub)
4091 AddOps.push_back(getNegativeSCEV(Op1));
4093 AddOps.push_back(Op1);
4095 AddOps.push_back(getSCEV(U->getOperand(0)));
4096 return getAddExpr(AddOps);
4098 case Instruction::Mul: {
4099 // Don't transfer NSW/NUW for the same reason as AddExpr.
4100 SmallVector<const SCEV *, 4> MulOps;
4101 MulOps.push_back(getSCEV(U->getOperand(1)));
4102 for (Value *Op = U->getOperand(0);
4103 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
4104 Op = U->getOperand(0)) {
4105 U = cast<Operator>(Op);
4106 MulOps.push_back(getSCEV(U->getOperand(1)));
4108 MulOps.push_back(getSCEV(U->getOperand(0)));
4109 return getMulExpr(MulOps);
4111 case Instruction::UDiv:
4112 return getUDivExpr(getSCEV(U->getOperand(0)),
4113 getSCEV(U->getOperand(1)));
4114 case Instruction::Sub:
4115 return getMinusSCEV(getSCEV(U->getOperand(0)),
4116 getSCEV(U->getOperand(1)));
4117 case Instruction::And:
4118 // For an expression like x&255 that merely masks off the high bits,
4119 // use zext(trunc(x)) as the SCEV expression.
4120 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4121 if (CI->isNullValue())
4122 return getSCEV(U->getOperand(1));
4123 if (CI->isAllOnesValue())
4124 return getSCEV(U->getOperand(0));
4125 const APInt &A = CI->getValue();
4127 // Instcombine's ShrinkDemandedConstant may strip bits out of
4128 // constants, obscuring what would otherwise be a low-bits mask.
4129 // Use computeKnownBits to compute what ShrinkDemandedConstant
4130 // knew about to reconstruct a low-bits mask value.
4131 unsigned LZ = A.countLeadingZeros();
4132 unsigned TZ = A.countTrailingZeros();
4133 unsigned BitWidth = A.getBitWidth();
4134 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4135 computeKnownBits(U->getOperand(0), KnownZero, KnownOne, DL,
4136 0, AT, nullptr, DT);
4138 APInt EffectiveMask =
4139 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
4140 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
4141 const SCEV *MulCount = getConstant(
4142 ConstantInt::get(getContext(), APInt::getOneBitSet(BitWidth, TZ)));
4146 getUDivExactExpr(getSCEV(U->getOperand(0)), MulCount),
4147 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
4154 case Instruction::Or:
4155 // If the RHS of the Or is a constant, we may have something like:
4156 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
4157 // optimizations will transparently handle this case.
4159 // In order for this transformation to be safe, the LHS must be of the
4160 // form X*(2^n) and the Or constant must be less than 2^n.
4161 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4162 const SCEV *LHS = getSCEV(U->getOperand(0));
4163 const APInt &CIVal = CI->getValue();
4164 if (GetMinTrailingZeros(LHS) >=
4165 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
4166 // Build a plain add SCEV.
4167 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
4168 // If the LHS of the add was an addrec and it has no-wrap flags,
4169 // transfer the no-wrap flags, since an or won't introduce a wrap.
4170 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
4171 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
4172 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
4173 OldAR->getNoWrapFlags());
4179 case Instruction::Xor:
4180 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
4181 // If the RHS of the xor is a signbit, then this is just an add.
4182 // Instcombine turns add of signbit into xor as a strength reduction step.
4183 if (CI->getValue().isSignBit())
4184 return getAddExpr(getSCEV(U->getOperand(0)),
4185 getSCEV(U->getOperand(1)));
4187 // If the RHS of xor is -1, then this is a not operation.
4188 if (CI->isAllOnesValue())
4189 return getNotSCEV(getSCEV(U->getOperand(0)));
4191 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
4192 // This is a variant of the check for xor with -1, and it handles
4193 // the case where instcombine has trimmed non-demanded bits out
4194 // of an xor with -1.
4195 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
4196 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
4197 if (BO->getOpcode() == Instruction::And &&
4198 LCI->getValue() == CI->getValue())
4199 if (const SCEVZeroExtendExpr *Z =
4200 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
4201 Type *UTy = U->getType();
4202 const SCEV *Z0 = Z->getOperand();
4203 Type *Z0Ty = Z0->getType();
4204 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
4206 // If C is a low-bits mask, the zero extend is serving to
4207 // mask off the high bits. Complement the operand and
4208 // re-apply the zext.
4209 if (APIntOps::isMask(Z0TySize, CI->getValue()))
4210 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
4212 // If C is a single bit, it may be in the sign-bit position
4213 // before the zero-extend. In this case, represent the xor
4214 // using an add, which is equivalent, and re-apply the zext.
4215 APInt Trunc = CI->getValue().trunc(Z0TySize);
4216 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
4218 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
4224 case Instruction::Shl:
4225 // Turn shift left of a constant amount into a multiply.
4226 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4227 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4229 // If the shift count is not less than the bitwidth, the result of
4230 // the shift is undefined. Don't try to analyze it, because the
4231 // resolution chosen here may differ from the resolution chosen in
4232 // other parts of the compiler.
4233 if (SA->getValue().uge(BitWidth))
4236 Constant *X = ConstantInt::get(getContext(),
4237 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4238 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4242 case Instruction::LShr:
4243 // Turn logical shift right of a constant into a unsigned divide.
4244 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
4245 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
4247 // If the shift count is not less than the bitwidth, the result of
4248 // the shift is undefined. Don't try to analyze it, because the
4249 // resolution chosen here may differ from the resolution chosen in
4250 // other parts of the compiler.
4251 if (SA->getValue().uge(BitWidth))
4254 Constant *X = ConstantInt::get(getContext(),
4255 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
4256 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
4260 case Instruction::AShr:
4261 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
4262 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
4263 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
4264 if (L->getOpcode() == Instruction::Shl &&
4265 L->getOperand(1) == U->getOperand(1)) {
4266 uint64_t BitWidth = getTypeSizeInBits(U->getType());
4268 // If the shift count is not less than the bitwidth, the result of
4269 // the shift is undefined. Don't try to analyze it, because the
4270 // resolution chosen here may differ from the resolution chosen in
4271 // other parts of the compiler.
4272 if (CI->getValue().uge(BitWidth))
4275 uint64_t Amt = BitWidth - CI->getZExtValue();
4276 if (Amt == BitWidth)
4277 return getSCEV(L->getOperand(0)); // shift by zero --> noop
4279 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
4280 IntegerType::get(getContext(),
4286 case Instruction::Trunc:
4287 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
4289 case Instruction::ZExt:
4290 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4292 case Instruction::SExt:
4293 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
4295 case Instruction::BitCast:
4296 // BitCasts are no-op casts so we just eliminate the cast.
4297 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
4298 return getSCEV(U->getOperand(0));
4301 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
4302 // lead to pointer expressions which cannot safely be expanded to GEPs,
4303 // because ScalarEvolution doesn't respect the GEP aliasing rules when
4304 // simplifying integer expressions.
4306 case Instruction::GetElementPtr:
4307 return createNodeForGEP(cast<GEPOperator>(U));
4309 case Instruction::PHI:
4310 return createNodeForPHI(cast<PHINode>(U));
4312 case Instruction::Select:
4313 // This could be a smax or umax that was lowered earlier.
4314 // Try to recover it.
4315 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
4316 Value *LHS = ICI->getOperand(0);
4317 Value *RHS = ICI->getOperand(1);
4318 switch (ICI->getPredicate()) {
4319 case ICmpInst::ICMP_SLT:
4320 case ICmpInst::ICMP_SLE:
4321 std::swap(LHS, RHS);
4323 case ICmpInst::ICMP_SGT:
4324 case ICmpInst::ICMP_SGE:
4325 // a >s b ? a+x : b+x -> smax(a, b)+x
4326 // a >s b ? b+x : a+x -> smin(a, b)+x
4327 if (LHS->getType() == U->getType()) {
4328 const SCEV *LS = getSCEV(LHS);
4329 const SCEV *RS = getSCEV(RHS);
4330 const SCEV *LA = getSCEV(U->getOperand(1));
4331 const SCEV *RA = getSCEV(U->getOperand(2));
4332 const SCEV *LDiff = getMinusSCEV(LA, LS);
4333 const SCEV *RDiff = getMinusSCEV(RA, RS);
4335 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
4336 LDiff = getMinusSCEV(LA, RS);
4337 RDiff = getMinusSCEV(RA, LS);
4339 return getAddExpr(getSMinExpr(LS, RS), LDiff);
4342 case ICmpInst::ICMP_ULT:
4343 case ICmpInst::ICMP_ULE:
4344 std::swap(LHS, RHS);
4346 case ICmpInst::ICMP_UGT:
4347 case ICmpInst::ICMP_UGE:
4348 // a >u b ? a+x : b+x -> umax(a, b)+x
4349 // a >u b ? b+x : a+x -> umin(a, b)+x
4350 if (LHS->getType() == U->getType()) {
4351 const SCEV *LS = getSCEV(LHS);
4352 const SCEV *RS = getSCEV(RHS);
4353 const SCEV *LA = getSCEV(U->getOperand(1));
4354 const SCEV *RA = getSCEV(U->getOperand(2));
4355 const SCEV *LDiff = getMinusSCEV(LA, LS);
4356 const SCEV *RDiff = getMinusSCEV(RA, RS);
4358 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
4359 LDiff = getMinusSCEV(LA, RS);
4360 RDiff = getMinusSCEV(RA, LS);
4362 return getAddExpr(getUMinExpr(LS, RS), LDiff);
4365 case ICmpInst::ICMP_NE:
4366 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
4367 if (LHS->getType() == U->getType() &&
4368 isa<ConstantInt>(RHS) &&
4369 cast<ConstantInt>(RHS)->isZero()) {
4370 const SCEV *One = getConstant(LHS->getType(), 1);
4371 const SCEV *LS = getSCEV(LHS);
4372 const SCEV *LA = getSCEV(U->getOperand(1));
4373 const SCEV *RA = getSCEV(U->getOperand(2));
4374 const SCEV *LDiff = getMinusSCEV(LA, LS);
4375 const SCEV *RDiff = getMinusSCEV(RA, One);
4377 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4380 case ICmpInst::ICMP_EQ:
4381 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4382 if (LHS->getType() == U->getType() &&
4383 isa<ConstantInt>(RHS) &&
4384 cast<ConstantInt>(RHS)->isZero()) {
4385 const SCEV *One = getConstant(LHS->getType(), 1);
4386 const SCEV *LS = getSCEV(LHS);
4387 const SCEV *LA = getSCEV(U->getOperand(1));
4388 const SCEV *RA = getSCEV(U->getOperand(2));
4389 const SCEV *LDiff = getMinusSCEV(LA, One);
4390 const SCEV *RDiff = getMinusSCEV(RA, LS);
4392 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4400 default: // We cannot analyze this expression.
4404 return getUnknown(V);
4409 //===----------------------------------------------------------------------===//
4410 // Iteration Count Computation Code
4413 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
4414 if (BasicBlock *ExitingBB = L->getExitingBlock())
4415 return getSmallConstantTripCount(L, ExitingBB);
4417 // No trip count information for multiple exits.
4421 /// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
4422 /// normal unsigned value. Returns 0 if the trip count is unknown or not
4423 /// constant. Will also return 0 if the maximum trip count is very large (>=
4426 /// This "trip count" assumes that control exits via ExitingBlock. More
4427 /// precisely, it is the number of times that control may reach ExitingBlock
4428 /// before taking the branch. For loops with multiple exits, it may not be the
4429 /// number times that the loop header executes because the loop may exit
4430 /// prematurely via another branch.
4431 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
4432 BasicBlock *ExitingBlock) {
4433 assert(ExitingBlock && "Must pass a non-null exiting block!");
4434 assert(L->isLoopExiting(ExitingBlock) &&
4435 "Exiting block must actually branch out of the loop!");
4436 const SCEVConstant *ExitCount =
4437 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
4441 ConstantInt *ExitConst = ExitCount->getValue();
4443 // Guard against huge trip counts.
4444 if (ExitConst->getValue().getActiveBits() > 32)
4447 // In case of integer overflow, this returns 0, which is correct.
4448 return ((unsigned)ExitConst->getZExtValue()) + 1;
4451 unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
4452 if (BasicBlock *ExitingBB = L->getExitingBlock())
4453 return getSmallConstantTripMultiple(L, ExitingBB);
4455 // No trip multiple information for multiple exits.
4459 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
4460 /// trip count of this loop as a normal unsigned value, if possible. This
4461 /// means that the actual trip count is always a multiple of the returned
4462 /// value (don't forget the trip count could very well be zero as well!).
4464 /// Returns 1 if the trip count is unknown or not guaranteed to be the
4465 /// multiple of a constant (which is also the case if the trip count is simply
4466 /// constant, use getSmallConstantTripCount for that case), Will also return 1
4467 /// if the trip count is very large (>= 2^32).
4469 /// As explained in the comments for getSmallConstantTripCount, this assumes
4470 /// that control exits the loop via ExitingBlock.
4472 ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
4473 BasicBlock *ExitingBlock) {
4474 assert(ExitingBlock && "Must pass a non-null exiting block!");
4475 assert(L->isLoopExiting(ExitingBlock) &&
4476 "Exiting block must actually branch out of the loop!");
4477 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
4478 if (ExitCount == getCouldNotCompute())
4481 // Get the trip count from the BE count by adding 1.
4482 const SCEV *TCMul = getAddExpr(ExitCount,
4483 getConstant(ExitCount->getType(), 1));
4484 // FIXME: SCEV distributes multiplication as V1*C1 + V2*C1. We could attempt
4485 // to factor simple cases.
4486 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(TCMul))
4487 TCMul = Mul->getOperand(0);
4489 const SCEVConstant *MulC = dyn_cast<SCEVConstant>(TCMul);
4493 ConstantInt *Result = MulC->getValue();
4495 // Guard against huge trip counts (this requires checking
4496 // for zero to handle the case where the trip count == -1 and the
4498 if (!Result || Result->getValue().getActiveBits() > 32 ||
4499 Result->getValue().getActiveBits() == 0)
4502 return (unsigned)Result->getZExtValue();
4505 // getExitCount - Get the expression for the number of loop iterations for which
4506 // this loop is guaranteed not to exit via ExitingBlock. Otherwise return
4507 // SCEVCouldNotCompute.
4508 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
4509 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
4512 /// getBackedgeTakenCount - If the specified loop has a predictable
4513 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
4514 /// object. The backedge-taken count is the number of times the loop header
4515 /// will be branched to from within the loop. This is one less than the
4516 /// trip count of the loop, since it doesn't count the first iteration,
4517 /// when the header is branched to from outside the loop.
4519 /// Note that it is not valid to call this method on a loop without a
4520 /// loop-invariant backedge-taken count (see
4521 /// hasLoopInvariantBackedgeTakenCount).
4523 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
4524 return getBackedgeTakenInfo(L).getExact(this);
4527 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
4528 /// return the least SCEV value that is known never to be less than the
4529 /// actual backedge taken count.
4530 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
4531 return getBackedgeTakenInfo(L).getMax(this);
4534 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
4535 /// onto the given Worklist.
4537 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
4538 BasicBlock *Header = L->getHeader();
4540 // Push all Loop-header PHIs onto the Worklist stack.
4541 for (BasicBlock::iterator I = Header->begin();
4542 PHINode *PN = dyn_cast<PHINode>(I); ++I)
4543 Worklist.push_back(PN);
4546 const ScalarEvolution::BackedgeTakenInfo &
4547 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
4548 // Initially insert an invalid entry for this loop. If the insertion
4549 // succeeds, proceed to actually compute a backedge-taken count and
4550 // update the value. The temporary CouldNotCompute value tells SCEV
4551 // code elsewhere that it shouldn't attempt to request a new
4552 // backedge-taken count, which could result in infinite recursion.
4553 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
4554 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
4556 return Pair.first->second;
4558 // ComputeBackedgeTakenCount may allocate memory for its result. Inserting it
4559 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
4560 // must be cleared in this scope.
4561 BackedgeTakenInfo Result = ComputeBackedgeTakenCount(L);
4563 if (Result.getExact(this) != getCouldNotCompute()) {
4564 assert(isLoopInvariant(Result.getExact(this), L) &&
4565 isLoopInvariant(Result.getMax(this), L) &&
4566 "Computed backedge-taken count isn't loop invariant for loop!");
4567 ++NumTripCountsComputed;
4569 else if (Result.getMax(this) == getCouldNotCompute() &&
4570 isa<PHINode>(L->getHeader()->begin())) {
4571 // Only count loops that have phi nodes as not being computable.
4572 ++NumTripCountsNotComputed;
4575 // Now that we know more about the trip count for this loop, forget any
4576 // existing SCEV values for PHI nodes in this loop since they are only
4577 // conservative estimates made without the benefit of trip count
4578 // information. This is similar to the code in forgetLoop, except that
4579 // it handles SCEVUnknown PHI nodes specially.
4580 if (Result.hasAnyInfo()) {
4581 SmallVector<Instruction *, 16> Worklist;
4582 PushLoopPHIs(L, Worklist);
4584 SmallPtrSet<Instruction *, 8> Visited;
4585 while (!Worklist.empty()) {
4586 Instruction *I = Worklist.pop_back_val();
4587 if (!Visited.insert(I)) continue;
4589 ValueExprMapType::iterator It =
4590 ValueExprMap.find_as(static_cast<Value *>(I));
4591 if (It != ValueExprMap.end()) {
4592 const SCEV *Old = It->second;
4594 // SCEVUnknown for a PHI either means that it has an unrecognized
4595 // structure, or it's a PHI that's in the progress of being computed
4596 // by createNodeForPHI. In the former case, additional loop trip
4597 // count information isn't going to change anything. In the later
4598 // case, createNodeForPHI will perform the necessary updates on its
4599 // own when it gets to that point.
4600 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
4601 forgetMemoizedResults(Old);
4602 ValueExprMap.erase(It);
4604 if (PHINode *PN = dyn_cast<PHINode>(I))
4605 ConstantEvolutionLoopExitValue.erase(PN);
4608 PushDefUseChildren(I, Worklist);
4612 // Re-lookup the insert position, since the call to
4613 // ComputeBackedgeTakenCount above could result in a
4614 // recusive call to getBackedgeTakenInfo (on a different
4615 // loop), which would invalidate the iterator computed
4617 return BackedgeTakenCounts.find(L)->second = Result;
4620 /// forgetLoop - This method should be called by the client when it has
4621 /// changed a loop in a way that may effect ScalarEvolution's ability to
4622 /// compute a trip count, or if the loop is deleted.
4623 void ScalarEvolution::forgetLoop(const Loop *L) {
4624 // Drop any stored trip count value.
4625 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
4626 BackedgeTakenCounts.find(L);
4627 if (BTCPos != BackedgeTakenCounts.end()) {
4628 BTCPos->second.clear();
4629 BackedgeTakenCounts.erase(BTCPos);
4632 // Drop information about expressions based on loop-header PHIs.
4633 SmallVector<Instruction *, 16> Worklist;
4634 PushLoopPHIs(L, Worklist);
4636 SmallPtrSet<Instruction *, 8> Visited;
4637 while (!Worklist.empty()) {
4638 Instruction *I = Worklist.pop_back_val();
4639 if (!Visited.insert(I)) continue;
4641 ValueExprMapType::iterator It =
4642 ValueExprMap.find_as(static_cast<Value *>(I));
4643 if (It != ValueExprMap.end()) {
4644 forgetMemoizedResults(It->second);
4645 ValueExprMap.erase(It);
4646 if (PHINode *PN = dyn_cast<PHINode>(I))
4647 ConstantEvolutionLoopExitValue.erase(PN);
4650 PushDefUseChildren(I, Worklist);
4653 // Forget all contained loops too, to avoid dangling entries in the
4654 // ValuesAtScopes map.
4655 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
4659 /// forgetValue - This method should be called by the client when it has
4660 /// changed a value in a way that may effect its value, or which may
4661 /// disconnect it from a def-use chain linking it to a loop.
4662 void ScalarEvolution::forgetValue(Value *V) {
4663 Instruction *I = dyn_cast<Instruction>(V);
4666 // Drop information about expressions based on loop-header PHIs.
4667 SmallVector<Instruction *, 16> Worklist;
4668 Worklist.push_back(I);
4670 SmallPtrSet<Instruction *, 8> Visited;
4671 while (!Worklist.empty()) {
4672 I = Worklist.pop_back_val();
4673 if (!Visited.insert(I)) continue;
4675 ValueExprMapType::iterator It =
4676 ValueExprMap.find_as(static_cast<Value *>(I));
4677 if (It != ValueExprMap.end()) {
4678 forgetMemoizedResults(It->second);
4679 ValueExprMap.erase(It);
4680 if (PHINode *PN = dyn_cast<PHINode>(I))
4681 ConstantEvolutionLoopExitValue.erase(PN);
4684 PushDefUseChildren(I, Worklist);
4688 /// getExact - Get the exact loop backedge taken count considering all loop
4689 /// exits. A computable result can only be return for loops with a single exit.
4690 /// Returning the minimum taken count among all exits is incorrect because one
4691 /// of the loop's exit limit's may have been skipped. HowFarToZero assumes that
4692 /// the limit of each loop test is never skipped. This is a valid assumption as
4693 /// long as the loop exits via that test. For precise results, it is the
4694 /// caller's responsibility to specify the relevant loop exit using
4695 /// getExact(ExitingBlock, SE).
4697 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
4698 // If any exits were not computable, the loop is not computable.
4699 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
4701 // We need exactly one computable exit.
4702 if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
4703 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
4705 const SCEV *BECount = nullptr;
4706 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4707 ENT != nullptr; ENT = ENT->getNextExit()) {
4709 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
4712 BECount = ENT->ExactNotTaken;
4713 else if (BECount != ENT->ExactNotTaken)
4714 return SE->getCouldNotCompute();
4716 assert(BECount && "Invalid not taken count for loop exit");
4720 /// getExact - Get the exact not taken count for this loop exit.
4722 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
4723 ScalarEvolution *SE) const {
4724 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4725 ENT != nullptr; ENT = ENT->getNextExit()) {
4727 if (ENT->ExitingBlock == ExitingBlock)
4728 return ENT->ExactNotTaken;
4730 return SE->getCouldNotCompute();
4733 /// getMax - Get the max backedge taken count for the loop.
4735 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
4736 return Max ? Max : SE->getCouldNotCompute();
4739 bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
4740 ScalarEvolution *SE) const {
4741 if (Max && Max != SE->getCouldNotCompute() && SE->hasOperand(Max, S))
4744 if (!ExitNotTaken.ExitingBlock)
4747 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4748 ENT != nullptr; ENT = ENT->getNextExit()) {
4750 if (ENT->ExactNotTaken != SE->getCouldNotCompute()
4751 && SE->hasOperand(ENT->ExactNotTaken, S)) {
4758 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
4759 /// computable exit into a persistent ExitNotTakenInfo array.
4760 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
4761 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
4762 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
4765 ExitNotTaken.setIncomplete();
4767 unsigned NumExits = ExitCounts.size();
4768 if (NumExits == 0) return;
4770 ExitNotTaken.ExitingBlock = ExitCounts[0].first;
4771 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
4772 if (NumExits == 1) return;
4774 // Handle the rare case of multiple computable exits.
4775 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
4777 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
4778 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
4779 PrevENT->setNextExit(ENT);
4780 ENT->ExitingBlock = ExitCounts[i].first;
4781 ENT->ExactNotTaken = ExitCounts[i].second;
4785 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
4786 void ScalarEvolution::BackedgeTakenInfo::clear() {
4787 ExitNotTaken.ExitingBlock = nullptr;
4788 ExitNotTaken.ExactNotTaken = nullptr;
4789 delete[] ExitNotTaken.getNextExit();
4792 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
4793 /// of the specified loop will execute.
4794 ScalarEvolution::BackedgeTakenInfo
4795 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
4796 SmallVector<BasicBlock *, 8> ExitingBlocks;
4797 L->getExitingBlocks(ExitingBlocks);
4799 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
4800 bool CouldComputeBECount = true;
4801 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
4802 const SCEV *MustExitMaxBECount = nullptr;
4803 const SCEV *MayExitMaxBECount = nullptr;
4805 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
4806 // and compute maxBECount.
4807 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
4808 BasicBlock *ExitBB = ExitingBlocks[i];
4809 ExitLimit EL = ComputeExitLimit(L, ExitBB);
4811 // 1. For each exit that can be computed, add an entry to ExitCounts.
4812 // CouldComputeBECount is true only if all exits can be computed.
4813 if (EL.Exact == getCouldNotCompute())
4814 // We couldn't compute an exact value for this exit, so
4815 // we won't be able to compute an exact value for the loop.
4816 CouldComputeBECount = false;
4818 ExitCounts.push_back(std::make_pair(ExitBB, EL.Exact));
4820 // 2. Derive the loop's MaxBECount from each exit's max number of
4821 // non-exiting iterations. Partition the loop exits into two kinds:
4822 // LoopMustExits and LoopMayExits.
4824 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
4825 // is a LoopMayExit. If any computable LoopMustExit is found, then
4826 // MaxBECount is the minimum EL.Max of computable LoopMustExits. Otherwise,
4827 // MaxBECount is conservatively the maximum EL.Max, where CouldNotCompute is
4828 // considered greater than any computable EL.Max.
4829 if (EL.Max != getCouldNotCompute() && Latch &&
4830 DT->dominates(ExitBB, Latch)) {
4831 if (!MustExitMaxBECount)
4832 MustExitMaxBECount = EL.Max;
4834 MustExitMaxBECount =
4835 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.Max);
4837 } else if (MayExitMaxBECount != getCouldNotCompute()) {
4838 if (!MayExitMaxBECount || EL.Max == getCouldNotCompute())
4839 MayExitMaxBECount = EL.Max;
4842 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.Max);
4846 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
4847 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
4848 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
4851 /// ComputeExitLimit - Compute the number of times the backedge of the specified
4852 /// loop will execute if it exits via the specified block.
4853 ScalarEvolution::ExitLimit
4854 ScalarEvolution::ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
4856 // Okay, we've chosen an exiting block. See what condition causes us to
4857 // exit at this block and remember the exit block and whether all other targets
4858 // lead to the loop header.
4859 bool MustExecuteLoopHeader = true;
4860 BasicBlock *Exit = nullptr;
4861 for (succ_iterator SI = succ_begin(ExitingBlock), SE = succ_end(ExitingBlock);
4863 if (!L->contains(*SI)) {
4864 if (Exit) // Multiple exit successors.
4865 return getCouldNotCompute();
4867 } else if (*SI != L->getHeader()) {
4868 MustExecuteLoopHeader = false;
4871 // At this point, we know we have a conditional branch that determines whether
4872 // the loop is exited. However, we don't know if the branch is executed each
4873 // time through the loop. If not, then the execution count of the branch will
4874 // not be equal to the trip count of the loop.
4876 // Currently we check for this by checking to see if the Exit branch goes to
4877 // the loop header. If so, we know it will always execute the same number of
4878 // times as the loop. We also handle the case where the exit block *is* the
4879 // loop header. This is common for un-rotated loops.
4881 // If both of those tests fail, walk up the unique predecessor chain to the
4882 // header, stopping if there is an edge that doesn't exit the loop. If the
4883 // header is reached, the execution count of the branch will be equal to the
4884 // trip count of the loop.
4886 // More extensive analysis could be done to handle more cases here.
4888 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
4889 // The simple checks failed, try climbing the unique predecessor chain
4890 // up to the header.
4892 for (BasicBlock *BB = ExitingBlock; BB; ) {
4893 BasicBlock *Pred = BB->getUniquePredecessor();
4895 return getCouldNotCompute();
4896 TerminatorInst *PredTerm = Pred->getTerminator();
4897 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
4898 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
4901 // If the predecessor has a successor that isn't BB and isn't
4902 // outside the loop, assume the worst.
4903 if (L->contains(PredSucc))
4904 return getCouldNotCompute();
4906 if (Pred == L->getHeader()) {
4913 return getCouldNotCompute();
4916 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
4917 TerminatorInst *Term = ExitingBlock->getTerminator();
4918 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
4919 assert(BI->isConditional() && "If unconditional, it can't be in loop!");
4920 // Proceed to the next level to examine the exit condition expression.
4921 return ComputeExitLimitFromCond(L, BI->getCondition(), BI->getSuccessor(0),
4922 BI->getSuccessor(1),
4923 /*ControlsExit=*/IsOnlyExit);
4926 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
4927 return ComputeExitLimitFromSingleExitSwitch(L, SI, Exit,
4928 /*ControlsExit=*/IsOnlyExit);
4930 return getCouldNotCompute();
4933 /// ComputeExitLimitFromCond - Compute the number of times the
4934 /// backedge of the specified loop will execute if its exit condition
4935 /// were a conditional branch of ExitCond, TBB, and FBB.
4937 /// @param ControlsExit is true if ExitCond directly controls the exit
4938 /// branch. In this case, we can assume that the loop exits only if the
4939 /// condition is true and can infer that failing to meet the condition prior to
4940 /// integer wraparound results in undefined behavior.
4941 ScalarEvolution::ExitLimit
4942 ScalarEvolution::ComputeExitLimitFromCond(const Loop *L,
4946 bool ControlsExit) {
4947 // Check if the controlling expression for this loop is an And or Or.
4948 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
4949 if (BO->getOpcode() == Instruction::And) {
4950 // Recurse on the operands of the and.
4951 bool EitherMayExit = L->contains(TBB);
4952 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
4953 ControlsExit && !EitherMayExit);
4954 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
4955 ControlsExit && !EitherMayExit);
4956 const SCEV *BECount = getCouldNotCompute();
4957 const SCEV *MaxBECount = getCouldNotCompute();
4958 if (EitherMayExit) {
4959 // Both conditions must be true for the loop to continue executing.
4960 // Choose the less conservative count.
4961 if (EL0.Exact == getCouldNotCompute() ||
4962 EL1.Exact == getCouldNotCompute())
4963 BECount = getCouldNotCompute();
4965 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4966 if (EL0.Max == getCouldNotCompute())
4967 MaxBECount = EL1.Max;
4968 else if (EL1.Max == getCouldNotCompute())
4969 MaxBECount = EL0.Max;
4971 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4973 // Both conditions must be true at the same time for the loop to exit.
4974 // For now, be conservative.
4975 assert(L->contains(FBB) && "Loop block has no successor in loop!");
4976 if (EL0.Max == EL1.Max)
4977 MaxBECount = EL0.Max;
4978 if (EL0.Exact == EL1.Exact)
4979 BECount = EL0.Exact;
4982 return ExitLimit(BECount, MaxBECount);
4984 if (BO->getOpcode() == Instruction::Or) {
4985 // Recurse on the operands of the or.
4986 bool EitherMayExit = L->contains(FBB);
4987 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
4988 ControlsExit && !EitherMayExit);
4989 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
4990 ControlsExit && !EitherMayExit);
4991 const SCEV *BECount = getCouldNotCompute();
4992 const SCEV *MaxBECount = getCouldNotCompute();
4993 if (EitherMayExit) {
4994 // Both conditions must be false for the loop to continue executing.
4995 // Choose the less conservative count.
4996 if (EL0.Exact == getCouldNotCompute() ||
4997 EL1.Exact == getCouldNotCompute())
4998 BECount = getCouldNotCompute();
5000 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
5001 if (EL0.Max == getCouldNotCompute())
5002 MaxBECount = EL1.Max;
5003 else if (EL1.Max == getCouldNotCompute())
5004 MaxBECount = EL0.Max;
5006 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
5008 // Both conditions must be false at the same time for the loop to exit.
5009 // For now, be conservative.
5010 assert(L->contains(TBB) && "Loop block has no successor in loop!");
5011 if (EL0.Max == EL1.Max)
5012 MaxBECount = EL0.Max;
5013 if (EL0.Exact == EL1.Exact)
5014 BECount = EL0.Exact;
5017 return ExitLimit(BECount, MaxBECount);
5021 // With an icmp, it may be feasible to compute an exact backedge-taken count.
5022 // Proceed to the next level to examine the icmp.
5023 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
5024 return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
5026 // Check for a constant condition. These are normally stripped out by
5027 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
5028 // preserve the CFG and is temporarily leaving constant conditions
5030 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
5031 if (L->contains(FBB) == !CI->getZExtValue())
5032 // The backedge is always taken.
5033 return getCouldNotCompute();
5035 // The backedge is never taken.
5036 return getConstant(CI->getType(), 0);
5039 // If it's not an integer or pointer comparison then compute it the hard way.
5040 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5043 /// ComputeExitLimitFromICmp - Compute the number of times the
5044 /// backedge of the specified loop will execute if its exit condition
5045 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
5046 ScalarEvolution::ExitLimit
5047 ScalarEvolution::ComputeExitLimitFromICmp(const Loop *L,
5051 bool ControlsExit) {
5053 // If the condition was exit on true, convert the condition to exit on false
5054 ICmpInst::Predicate Cond;
5055 if (!L->contains(FBB))
5056 Cond = ExitCond->getPredicate();
5058 Cond = ExitCond->getInversePredicate();
5060 // Handle common loops like: for (X = "string"; *X; ++X)
5061 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
5062 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
5064 ComputeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
5065 if (ItCnt.hasAnyInfo())
5069 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
5070 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
5072 // Try to evaluate any dependencies out of the loop.
5073 LHS = getSCEVAtScope(LHS, L);
5074 RHS = getSCEVAtScope(RHS, L);
5076 // At this point, we would like to compute how many iterations of the
5077 // loop the predicate will return true for these inputs.
5078 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
5079 // If there is a loop-invariant, force it into the RHS.
5080 std::swap(LHS, RHS);
5081 Cond = ICmpInst::getSwappedPredicate(Cond);
5084 // Simplify the operands before analyzing them.
5085 (void)SimplifyICmpOperands(Cond, LHS, RHS);
5087 // If we have a comparison of a chrec against a constant, try to use value
5088 // ranges to answer this query.
5089 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
5090 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
5091 if (AddRec->getLoop() == L) {
5092 // Form the constant range.
5093 ConstantRange CompRange(
5094 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
5096 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
5097 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
5101 case ICmpInst::ICMP_NE: { // while (X != Y)
5102 // Convert to: while (X-Y != 0)
5103 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5104 if (EL.hasAnyInfo()) return EL;
5107 case ICmpInst::ICMP_EQ: { // while (X == Y)
5108 // Convert to: while (X-Y == 0)
5109 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
5110 if (EL.hasAnyInfo()) return EL;
5113 case ICmpInst::ICMP_SLT:
5114 case ICmpInst::ICMP_ULT: { // while (X < Y)
5115 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
5116 ExitLimit EL = HowManyLessThans(LHS, RHS, L, IsSigned, ControlsExit);
5117 if (EL.hasAnyInfo()) return EL;
5120 case ICmpInst::ICMP_SGT:
5121 case ICmpInst::ICMP_UGT: { // while (X > Y)
5122 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
5123 ExitLimit EL = HowManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit);
5124 if (EL.hasAnyInfo()) return EL;
5129 dbgs() << "ComputeBackedgeTakenCount ";
5130 if (ExitCond->getOperand(0)->getType()->isUnsigned())
5131 dbgs() << "[unsigned] ";
5132 dbgs() << *LHS << " "
5133 << Instruction::getOpcodeName(Instruction::ICmp)
5134 << " " << *RHS << "\n";
5138 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
5141 ScalarEvolution::ExitLimit
5142 ScalarEvolution::ComputeExitLimitFromSingleExitSwitch(const Loop *L,
5144 BasicBlock *ExitingBlock,
5145 bool ControlsExit) {
5146 assert(!L->contains(ExitingBlock) && "Not an exiting block!");
5148 // Give up if the exit is the default dest of a switch.
5149 if (Switch->getDefaultDest() == ExitingBlock)
5150 return getCouldNotCompute();
5152 assert(L->contains(Switch->getDefaultDest()) &&
5153 "Default case must not exit the loop!");
5154 const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
5155 const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
5157 // while (X != Y) --> while (X-Y != 0)
5158 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
5159 if (EL.hasAnyInfo())
5162 return getCouldNotCompute();
5165 static ConstantInt *
5166 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
5167 ScalarEvolution &SE) {
5168 const SCEV *InVal = SE.getConstant(C);
5169 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
5170 assert(isa<SCEVConstant>(Val) &&
5171 "Evaluation of SCEV at constant didn't fold correctly?");
5172 return cast<SCEVConstant>(Val)->getValue();
5175 /// ComputeLoadConstantCompareExitLimit - Given an exit condition of
5176 /// 'icmp op load X, cst', try to see if we can compute the backedge
5177 /// execution count.
5178 ScalarEvolution::ExitLimit
5179 ScalarEvolution::ComputeLoadConstantCompareExitLimit(
5183 ICmpInst::Predicate predicate) {
5185 if (LI->isVolatile()) return getCouldNotCompute();
5187 // Check to see if the loaded pointer is a getelementptr of a global.
5188 // TODO: Use SCEV instead of manually grubbing with GEPs.
5189 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
5190 if (!GEP) return getCouldNotCompute();
5192 // Make sure that it is really a constant global we are gepping, with an
5193 // initializer, and make sure the first IDX is really 0.
5194 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
5195 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
5196 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
5197 !cast<Constant>(GEP->getOperand(1))->isNullValue())
5198 return getCouldNotCompute();
5200 // Okay, we allow one non-constant index into the GEP instruction.
5201 Value *VarIdx = nullptr;
5202 std::vector<Constant*> Indexes;
5203 unsigned VarIdxNum = 0;
5204 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
5205 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
5206 Indexes.push_back(CI);
5207 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
5208 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
5209 VarIdx = GEP->getOperand(i);
5211 Indexes.push_back(nullptr);
5214 // Loop-invariant loads may be a byproduct of loop optimization. Skip them.
5216 return getCouldNotCompute();
5218 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
5219 // Check to see if X is a loop variant variable value now.
5220 const SCEV *Idx = getSCEV(VarIdx);
5221 Idx = getSCEVAtScope(Idx, L);
5223 // We can only recognize very limited forms of loop index expressions, in
5224 // particular, only affine AddRec's like {C1,+,C2}.
5225 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
5226 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
5227 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
5228 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
5229 return getCouldNotCompute();
5231 unsigned MaxSteps = MaxBruteForceIterations;
5232 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
5233 ConstantInt *ItCst = ConstantInt::get(
5234 cast<IntegerType>(IdxExpr->getType()), IterationNum);
5235 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
5237 // Form the GEP offset.
5238 Indexes[VarIdxNum] = Val;
5240 Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
5242 if (!Result) break; // Cannot compute!
5244 // Evaluate the condition for this iteration.
5245 Result = ConstantExpr::getICmp(predicate, Result, RHS);
5246 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
5247 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
5249 dbgs() << "\n***\n*** Computed loop count " << *ItCst
5250 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
5253 ++NumArrayLenItCounts;
5254 return getConstant(ItCst); // Found terminating iteration!
5257 return getCouldNotCompute();
5261 /// CanConstantFold - Return true if we can constant fold an instruction of the
5262 /// specified type, assuming that all operands were constants.
5263 static bool CanConstantFold(const Instruction *I) {
5264 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
5265 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
5269 if (const CallInst *CI = dyn_cast<CallInst>(I))
5270 if (const Function *F = CI->getCalledFunction())
5271 return canConstantFoldCallTo(F);
5275 /// Determine whether this instruction can constant evolve within this loop
5276 /// assuming its operands can all constant evolve.
5277 static bool canConstantEvolve(Instruction *I, const Loop *L) {
5278 // An instruction outside of the loop can't be derived from a loop PHI.
5279 if (!L->contains(I)) return false;
5281 if (isa<PHINode>(I)) {
5282 if (L->getHeader() == I->getParent())
5285 // We don't currently keep track of the control flow needed to evaluate
5286 // PHIs, so we cannot handle PHIs inside of loops.
5290 // If we won't be able to constant fold this expression even if the operands
5291 // are constants, bail early.
5292 return CanConstantFold(I);
5295 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
5296 /// recursing through each instruction operand until reaching a loop header phi.
5298 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
5299 DenseMap<Instruction *, PHINode *> &PHIMap) {
5301 // Otherwise, we can evaluate this instruction if all of its operands are
5302 // constant or derived from a PHI node themselves.
5303 PHINode *PHI = nullptr;
5304 for (Instruction::op_iterator OpI = UseInst->op_begin(),
5305 OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
5307 if (isa<Constant>(*OpI)) continue;
5309 Instruction *OpInst = dyn_cast<Instruction>(*OpI);
5310 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
5312 PHINode *P = dyn_cast<PHINode>(OpInst);
5314 // If this operand is already visited, reuse the prior result.
5315 // We may have P != PHI if this is the deepest point at which the
5316 // inconsistent paths meet.
5317 P = PHIMap.lookup(OpInst);
5319 // Recurse and memoize the results, whether a phi is found or not.
5320 // This recursive call invalidates pointers into PHIMap.
5321 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
5325 return nullptr; // Not evolving from PHI
5326 if (PHI && PHI != P)
5327 return nullptr; // Evolving from multiple different PHIs.
5330 // This is a expression evolving from a constant PHI!
5334 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
5335 /// in the loop that V is derived from. We allow arbitrary operations along the
5336 /// way, but the operands of an operation must either be constants or a value
5337 /// derived from a constant PHI. If this expression does not fit with these
5338 /// constraints, return null.
5339 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
5340 Instruction *I = dyn_cast<Instruction>(V);
5341 if (!I || !canConstantEvolve(I, L)) return nullptr;
5343 if (PHINode *PN = dyn_cast<PHINode>(I)) {
5347 // Record non-constant instructions contained by the loop.
5348 DenseMap<Instruction *, PHINode *> PHIMap;
5349 return getConstantEvolvingPHIOperands(I, L, PHIMap);
5352 /// EvaluateExpression - Given an expression that passes the
5353 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
5354 /// in the loop has the value PHIVal. If we can't fold this expression for some
5355 /// reason, return null.
5356 static Constant *EvaluateExpression(Value *V, const Loop *L,
5357 DenseMap<Instruction *, Constant *> &Vals,
5358 const DataLayout *DL,
5359 const TargetLibraryInfo *TLI) {
5360 // Convenient constant check, but redundant for recursive calls.
5361 if (Constant *C = dyn_cast<Constant>(V)) return C;
5362 Instruction *I = dyn_cast<Instruction>(V);
5363 if (!I) return nullptr;
5365 if (Constant *C = Vals.lookup(I)) return C;
5367 // An instruction inside the loop depends on a value outside the loop that we
5368 // weren't given a mapping for, or a value such as a call inside the loop.
5369 if (!canConstantEvolve(I, L)) return nullptr;
5371 // An unmapped PHI can be due to a branch or another loop inside this loop,
5372 // or due to this not being the initial iteration through a loop where we
5373 // couldn't compute the evolution of this particular PHI last time.
5374 if (isa<PHINode>(I)) return nullptr;
5376 std::vector<Constant*> Operands(I->getNumOperands());
5378 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5379 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
5381 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
5382 if (!Operands[i]) return nullptr;
5385 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
5387 if (!C) return nullptr;
5391 if (CmpInst *CI = dyn_cast<CmpInst>(I))
5392 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
5393 Operands[1], DL, TLI);
5394 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
5395 if (!LI->isVolatile())
5396 return ConstantFoldLoadFromConstPtr(Operands[0], DL);
5398 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, DL,
5402 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
5403 /// in the header of its containing loop, we know the loop executes a
5404 /// constant number of times, and the PHI node is just a recurrence
5405 /// involving constants, fold it.
5407 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
5410 DenseMap<PHINode*, Constant*>::const_iterator I =
5411 ConstantEvolutionLoopExitValue.find(PN);
5412 if (I != ConstantEvolutionLoopExitValue.end())
5415 if (BEs.ugt(MaxBruteForceIterations))
5416 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
5418 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
5420 DenseMap<Instruction *, Constant *> CurrentIterVals;
5421 BasicBlock *Header = L->getHeader();
5422 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5424 // Since the loop is canonicalized, the PHI node must have two entries. One
5425 // entry must be a constant (coming in from outside of the loop), and the
5426 // second must be derived from the same PHI.
5427 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
5428 PHINode *PHI = nullptr;
5429 for (BasicBlock::iterator I = Header->begin();
5430 (PHI = dyn_cast<PHINode>(I)); ++I) {
5431 Constant *StartCST =
5432 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
5433 if (!StartCST) continue;
5434 CurrentIterVals[PHI] = StartCST;
5436 if (!CurrentIterVals.count(PN))
5437 return RetVal = nullptr;
5439 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
5441 // Execute the loop symbolically to determine the exit value.
5442 if (BEs.getActiveBits() >= 32)
5443 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
5445 unsigned NumIterations = BEs.getZExtValue(); // must be in range
5446 unsigned IterationNum = 0;
5447 for (; ; ++IterationNum) {
5448 if (IterationNum == NumIterations)
5449 return RetVal = CurrentIterVals[PN]; // Got exit value!
5451 // Compute the value of the PHIs for the next iteration.
5452 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
5453 DenseMap<Instruction *, Constant *> NextIterVals;
5454 Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL,
5457 return nullptr; // Couldn't evaluate!
5458 NextIterVals[PN] = NextPHI;
5460 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
5462 // Also evaluate the other PHI nodes. However, we don't get to stop if we
5463 // cease to be able to evaluate one of them or if they stop evolving,
5464 // because that doesn't necessarily prevent us from computing PN.
5465 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
5466 for (DenseMap<Instruction *, Constant *>::const_iterator
5467 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
5468 PHINode *PHI = dyn_cast<PHINode>(I->first);
5469 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
5470 PHIsToCompute.push_back(std::make_pair(PHI, I->second));
5472 // We use two distinct loops because EvaluateExpression may invalidate any
5473 // iterators into CurrentIterVals.
5474 for (SmallVectorImpl<std::pair<PHINode *, Constant*> >::const_iterator
5475 I = PHIsToCompute.begin(), E = PHIsToCompute.end(); I != E; ++I) {
5476 PHINode *PHI = I->first;
5477 Constant *&NextPHI = NextIterVals[PHI];
5478 if (!NextPHI) { // Not already computed.
5479 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
5480 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
5482 if (NextPHI != I->second)
5483 StoppedEvolving = false;
5486 // If all entries in CurrentIterVals == NextIterVals then we can stop
5487 // iterating, the loop can't continue to change.
5488 if (StoppedEvolving)
5489 return RetVal = CurrentIterVals[PN];
5491 CurrentIterVals.swap(NextIterVals);
5495 /// ComputeExitCountExhaustively - If the loop is known to execute a
5496 /// constant number of times (the condition evolves only from constants),
5497 /// try to evaluate a few iterations of the loop until we get the exit
5498 /// condition gets a value of ExitWhen (true or false). If we cannot
5499 /// evaluate the trip count of the loop, return getCouldNotCompute().
5500 const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
5503 PHINode *PN = getConstantEvolvingPHI(Cond, L);
5504 if (!PN) return getCouldNotCompute();
5506 // If the loop is canonicalized, the PHI will have exactly two entries.
5507 // That's the only form we support here.
5508 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
5510 DenseMap<Instruction *, Constant *> CurrentIterVals;
5511 BasicBlock *Header = L->getHeader();
5512 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
5514 // One entry must be a constant (coming in from outside of the loop), and the
5515 // second must be derived from the same PHI.
5516 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
5517 PHINode *PHI = nullptr;
5518 for (BasicBlock::iterator I = Header->begin();
5519 (PHI = dyn_cast<PHINode>(I)); ++I) {
5520 Constant *StartCST =
5521 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
5522 if (!StartCST) continue;
5523 CurrentIterVals[PHI] = StartCST;
5525 if (!CurrentIterVals.count(PN))
5526 return getCouldNotCompute();
5528 // Okay, we find a PHI node that defines the trip count of this loop. Execute
5529 // the loop symbolically to determine when the condition gets a value of
5532 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
5533 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
5534 ConstantInt *CondVal =
5535 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L, CurrentIterVals,
5538 // Couldn't symbolically evaluate.
5539 if (!CondVal) return getCouldNotCompute();
5541 if (CondVal->getValue() == uint64_t(ExitWhen)) {
5542 ++NumBruteForceTripCountsComputed;
5543 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
5546 // Update all the PHI nodes for the next iteration.
5547 DenseMap<Instruction *, Constant *> NextIterVals;
5549 // Create a list of which PHIs we need to compute. We want to do this before
5550 // calling EvaluateExpression on them because that may invalidate iterators
5551 // into CurrentIterVals.
5552 SmallVector<PHINode *, 8> PHIsToCompute;
5553 for (DenseMap<Instruction *, Constant *>::const_iterator
5554 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
5555 PHINode *PHI = dyn_cast<PHINode>(I->first);
5556 if (!PHI || PHI->getParent() != Header) continue;
5557 PHIsToCompute.push_back(PHI);
5559 for (SmallVectorImpl<PHINode *>::const_iterator I = PHIsToCompute.begin(),
5560 E = PHIsToCompute.end(); I != E; ++I) {
5562 Constant *&NextPHI = NextIterVals[PHI];
5563 if (NextPHI) continue; // Already computed!
5565 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
5566 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, TLI);
5568 CurrentIterVals.swap(NextIterVals);
5571 // Too many iterations were needed to evaluate.
5572 return getCouldNotCompute();
5575 /// getSCEVAtScope - Return a SCEV expression for the specified value
5576 /// at the specified scope in the program. The L value specifies a loop
5577 /// nest to evaluate the expression at, where null is the top-level or a
5578 /// specified loop is immediately inside of the loop.
5580 /// This method can be used to compute the exit value for a variable defined
5581 /// in a loop by querying what the value will hold in the parent loop.
5583 /// In the case that a relevant loop exit value cannot be computed, the
5584 /// original value V is returned.
5585 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
5586 // Check to see if we've folded this expression at this loop before.
5587 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values = ValuesAtScopes[V];
5588 for (unsigned u = 0; u < Values.size(); u++) {
5589 if (Values[u].first == L)
5590 return Values[u].second ? Values[u].second : V;
5592 Values.push_back(std::make_pair(L, static_cast<const SCEV *>(nullptr)));
5593 // Otherwise compute it.
5594 const SCEV *C = computeSCEVAtScope(V, L);
5595 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values2 = ValuesAtScopes[V];
5596 for (unsigned u = Values2.size(); u > 0; u--) {
5597 if (Values2[u - 1].first == L) {
5598 Values2[u - 1].second = C;
5605 /// This builds up a Constant using the ConstantExpr interface. That way, we
5606 /// will return Constants for objects which aren't represented by a
5607 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
5608 /// Returns NULL if the SCEV isn't representable as a Constant.
5609 static Constant *BuildConstantFromSCEV(const SCEV *V) {
5610 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
5611 case scCouldNotCompute:
5615 return cast<SCEVConstant>(V)->getValue();
5617 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
5618 case scSignExtend: {
5619 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
5620 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
5621 return ConstantExpr::getSExt(CastOp, SS->getType());
5624 case scZeroExtend: {
5625 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
5626 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
5627 return ConstantExpr::getZExt(CastOp, SZ->getType());
5631 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
5632 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
5633 return ConstantExpr::getTrunc(CastOp, ST->getType());
5637 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
5638 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
5639 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
5640 unsigned AS = PTy->getAddressSpace();
5641 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5642 C = ConstantExpr::getBitCast(C, DestPtrTy);
5644 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
5645 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
5646 if (!C2) return nullptr;
5649 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
5650 unsigned AS = C2->getType()->getPointerAddressSpace();
5652 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
5653 // The offsets have been converted to bytes. We can add bytes to an
5654 // i8* by GEP with the byte count in the first index.
5655 C = ConstantExpr::getBitCast(C, DestPtrTy);
5658 // Don't bother trying to sum two pointers. We probably can't
5659 // statically compute a load that results from it anyway.
5660 if (C2->getType()->isPointerTy())
5663 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
5664 if (PTy->getElementType()->isStructTy())
5665 C2 = ConstantExpr::getIntegerCast(
5666 C2, Type::getInt32Ty(C->getContext()), true);
5667 C = ConstantExpr::getGetElementPtr(C, C2);
5669 C = ConstantExpr::getAdd(C, C2);
5676 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
5677 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
5678 // Don't bother with pointers at all.
5679 if (C->getType()->isPointerTy()) return nullptr;
5680 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
5681 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
5682 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
5683 C = ConstantExpr::getMul(C, C2);
5690 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
5691 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
5692 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
5693 if (LHS->getType() == RHS->getType())
5694 return ConstantExpr::getUDiv(LHS, RHS);
5699 break; // TODO: smax, umax.
5704 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
5705 if (isa<SCEVConstant>(V)) return V;
5707 // If this instruction is evolved from a constant-evolving PHI, compute the
5708 // exit value from the loop without using SCEVs.
5709 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
5710 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
5711 const Loop *LI = (*this->LI)[I->getParent()];
5712 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
5713 if (PHINode *PN = dyn_cast<PHINode>(I))
5714 if (PN->getParent() == LI->getHeader()) {
5715 // Okay, there is no closed form solution for the PHI node. Check
5716 // to see if the loop that contains it has a known backedge-taken
5717 // count. If so, we may be able to force computation of the exit
5719 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
5720 if (const SCEVConstant *BTCC =
5721 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
5722 // Okay, we know how many times the containing loop executes. If
5723 // this is a constant evolving PHI node, get the final value at
5724 // the specified iteration number.
5725 Constant *RV = getConstantEvolutionLoopExitValue(PN,
5726 BTCC->getValue()->getValue(),
5728 if (RV) return getSCEV(RV);
5732 // Okay, this is an expression that we cannot symbolically evaluate
5733 // into a SCEV. Check to see if it's possible to symbolically evaluate
5734 // the arguments into constants, and if so, try to constant propagate the
5735 // result. This is particularly useful for computing loop exit values.
5736 if (CanConstantFold(I)) {
5737 SmallVector<Constant *, 4> Operands;
5738 bool MadeImprovement = false;
5739 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5740 Value *Op = I->getOperand(i);
5741 if (Constant *C = dyn_cast<Constant>(Op)) {
5742 Operands.push_back(C);
5746 // If any of the operands is non-constant and if they are
5747 // non-integer and non-pointer, don't even try to analyze them
5748 // with scev techniques.
5749 if (!isSCEVable(Op->getType()))
5752 const SCEV *OrigV = getSCEV(Op);
5753 const SCEV *OpV = getSCEVAtScope(OrigV, L);
5754 MadeImprovement |= OrigV != OpV;
5756 Constant *C = BuildConstantFromSCEV(OpV);
5758 if (C->getType() != Op->getType())
5759 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5763 Operands.push_back(C);
5766 // Check to see if getSCEVAtScope actually made an improvement.
5767 if (MadeImprovement) {
5768 Constant *C = nullptr;
5769 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
5770 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
5771 Operands[0], Operands[1], DL,
5773 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
5774 if (!LI->isVolatile())
5775 C = ConstantFoldLoadFromConstPtr(Operands[0], DL);
5777 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
5785 // This is some other type of SCEVUnknown, just return it.
5789 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
5790 // Avoid performing the look-up in the common case where the specified
5791 // expression has no loop-variant portions.
5792 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
5793 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5794 if (OpAtScope != Comm->getOperand(i)) {
5795 // Okay, at least one of these operands is loop variant but might be
5796 // foldable. Build a new instance of the folded commutative expression.
5797 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
5798 Comm->op_begin()+i);
5799 NewOps.push_back(OpAtScope);
5801 for (++i; i != e; ++i) {
5802 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5803 NewOps.push_back(OpAtScope);
5805 if (isa<SCEVAddExpr>(Comm))
5806 return getAddExpr(NewOps);
5807 if (isa<SCEVMulExpr>(Comm))
5808 return getMulExpr(NewOps);
5809 if (isa<SCEVSMaxExpr>(Comm))
5810 return getSMaxExpr(NewOps);
5811 if (isa<SCEVUMaxExpr>(Comm))
5812 return getUMaxExpr(NewOps);
5813 llvm_unreachable("Unknown commutative SCEV type!");
5816 // If we got here, all operands are loop invariant.
5820 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
5821 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
5822 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
5823 if (LHS == Div->getLHS() && RHS == Div->getRHS())
5824 return Div; // must be loop invariant
5825 return getUDivExpr(LHS, RHS);
5828 // If this is a loop recurrence for a loop that does not contain L, then we
5829 // are dealing with the final value computed by the loop.
5830 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
5831 // First, attempt to evaluate each operand.
5832 // Avoid performing the look-up in the common case where the specified
5833 // expression has no loop-variant portions.
5834 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
5835 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
5836 if (OpAtScope == AddRec->getOperand(i))
5839 // Okay, at least one of these operands is loop variant but might be
5840 // foldable. Build a new instance of the folded commutative expression.
5841 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
5842 AddRec->op_begin()+i);
5843 NewOps.push_back(OpAtScope);
5844 for (++i; i != e; ++i)
5845 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
5847 const SCEV *FoldedRec =
5848 getAddRecExpr(NewOps, AddRec->getLoop(),
5849 AddRec->getNoWrapFlags(SCEV::FlagNW));
5850 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
5851 // The addrec may be folded to a nonrecurrence, for example, if the
5852 // induction variable is multiplied by zero after constant folding. Go
5853 // ahead and return the folded value.
5859 // If the scope is outside the addrec's loop, evaluate it by using the
5860 // loop exit value of the addrec.
5861 if (!AddRec->getLoop()->contains(L)) {
5862 // To evaluate this recurrence, we need to know how many times the AddRec
5863 // loop iterates. Compute this now.
5864 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
5865 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
5867 // Then, evaluate the AddRec.
5868 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
5874 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
5875 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5876 if (Op == Cast->getOperand())
5877 return Cast; // must be loop invariant
5878 return getZeroExtendExpr(Op, Cast->getType());
5881 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
5882 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5883 if (Op == Cast->getOperand())
5884 return Cast; // must be loop invariant
5885 return getSignExtendExpr(Op, Cast->getType());
5888 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
5889 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5890 if (Op == Cast->getOperand())
5891 return Cast; // must be loop invariant
5892 return getTruncateExpr(Op, Cast->getType());
5895 llvm_unreachable("Unknown SCEV type!");
5898 /// getSCEVAtScope - This is a convenience function which does
5899 /// getSCEVAtScope(getSCEV(V), L).
5900 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
5901 return getSCEVAtScope(getSCEV(V), L);
5904 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
5905 /// following equation:
5907 /// A * X = B (mod N)
5909 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
5910 /// A and B isn't important.
5912 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
5913 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
5914 ScalarEvolution &SE) {
5915 uint32_t BW = A.getBitWidth();
5916 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
5917 assert(A != 0 && "A must be non-zero.");
5921 // The gcd of A and N may have only one prime factor: 2. The number of
5922 // trailing zeros in A is its multiplicity
5923 uint32_t Mult2 = A.countTrailingZeros();
5926 // 2. Check if B is divisible by D.
5928 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
5929 // is not less than multiplicity of this prime factor for D.
5930 if (B.countTrailingZeros() < Mult2)
5931 return SE.getCouldNotCompute();
5933 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
5936 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
5937 // bit width during computations.
5938 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
5939 APInt Mod(BW + 1, 0);
5940 Mod.setBit(BW - Mult2); // Mod = N / D
5941 APInt I = AD.multiplicativeInverse(Mod);
5943 // 4. Compute the minimum unsigned root of the equation:
5944 // I * (B / D) mod (N / D)
5945 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
5947 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
5949 return SE.getConstant(Result.trunc(BW));
5952 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
5953 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
5954 /// might be the same) or two SCEVCouldNotCompute objects.
5956 static std::pair<const SCEV *,const SCEV *>
5957 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
5958 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
5959 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
5960 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
5961 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
5963 // We currently can only solve this if the coefficients are constants.
5964 if (!LC || !MC || !NC) {
5965 const SCEV *CNC = SE.getCouldNotCompute();
5966 return std::make_pair(CNC, CNC);
5969 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
5970 const APInt &L = LC->getValue()->getValue();
5971 const APInt &M = MC->getValue()->getValue();
5972 const APInt &N = NC->getValue()->getValue();
5973 APInt Two(BitWidth, 2);
5974 APInt Four(BitWidth, 4);
5977 using namespace APIntOps;
5979 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
5980 // The B coefficient is M-N/2
5984 // The A coefficient is N/2
5985 APInt A(N.sdiv(Two));
5987 // Compute the B^2-4ac term.
5990 SqrtTerm -= Four * (A * C);
5992 if (SqrtTerm.isNegative()) {
5993 // The loop is provably infinite.
5994 const SCEV *CNC = SE.getCouldNotCompute();
5995 return std::make_pair(CNC, CNC);
5998 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
5999 // integer value or else APInt::sqrt() will assert.
6000 APInt SqrtVal(SqrtTerm.sqrt());
6002 // Compute the two solutions for the quadratic formula.
6003 // The divisions must be performed as signed divisions.
6006 if (TwoA.isMinValue()) {
6007 const SCEV *CNC = SE.getCouldNotCompute();
6008 return std::make_pair(CNC, CNC);
6011 LLVMContext &Context = SE.getContext();
6013 ConstantInt *Solution1 =
6014 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
6015 ConstantInt *Solution2 =
6016 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
6018 return std::make_pair(SE.getConstant(Solution1),
6019 SE.getConstant(Solution2));
6020 } // end APIntOps namespace
6023 /// HowFarToZero - Return the number of times a backedge comparing the specified
6024 /// value to zero will execute. If not computable, return CouldNotCompute.
6026 /// This is only used for loops with a "x != y" exit test. The exit condition is
6027 /// now expressed as a single expression, V = x-y. So the exit test is
6028 /// effectively V != 0. We know and take advantage of the fact that this
6029 /// expression only being used in a comparison by zero context.
6030 ScalarEvolution::ExitLimit
6031 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L, bool ControlsExit) {
6032 // If the value is a constant
6033 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6034 // If the value is already zero, the branch will execute zero times.
6035 if (C->getValue()->isZero()) return C;
6036 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6039 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
6040 if (!AddRec || AddRec->getLoop() != L)
6041 return getCouldNotCompute();
6043 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
6044 // the quadratic equation to solve it.
6045 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
6046 std::pair<const SCEV *,const SCEV *> Roots =
6047 SolveQuadraticEquation(AddRec, *this);
6048 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
6049 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
6052 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
6053 << " sol#2: " << *R2 << "\n";
6055 // Pick the smallest positive root value.
6056 if (ConstantInt *CB =
6057 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
6060 if (CB->getZExtValue() == false)
6061 std::swap(R1, R2); // R1 is the minimum root now.
6063 // We can only use this value if the chrec ends up with an exact zero
6064 // value at this index. When solving for "X*X != 5", for example, we
6065 // should not accept a root of 2.
6066 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
6068 return R1; // We found a quadratic root!
6071 return getCouldNotCompute();
6074 // Otherwise we can only handle this if it is affine.
6075 if (!AddRec->isAffine())
6076 return getCouldNotCompute();
6078 // If this is an affine expression, the execution count of this branch is
6079 // the minimum unsigned root of the following equation:
6081 // Start + Step*N = 0 (mod 2^BW)
6085 // Step*N = -Start (mod 2^BW)
6087 // where BW is the common bit width of Start and Step.
6089 // Get the initial value for the loop.
6090 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
6091 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
6093 // For now we handle only constant steps.
6095 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
6096 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
6097 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
6098 // We have not yet seen any such cases.
6099 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
6100 if (!StepC || StepC->getValue()->equalsInt(0))
6101 return getCouldNotCompute();
6103 // For positive steps (counting up until unsigned overflow):
6104 // N = -Start/Step (as unsigned)
6105 // For negative steps (counting down to zero):
6107 // First compute the unsigned distance from zero in the direction of Step.
6108 bool CountDown = StepC->getValue()->getValue().isNegative();
6109 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
6111 // Handle unitary steps, which cannot wraparound.
6112 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
6113 // N = Distance (as unsigned)
6114 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
6115 ConstantRange CR = getUnsignedRange(Start);
6116 const SCEV *MaxBECount;
6117 if (!CountDown && CR.getUnsignedMin().isMinValue())
6118 // When counting up, the worst starting value is 1, not 0.
6119 MaxBECount = CR.getUnsignedMax().isMinValue()
6120 ? getConstant(APInt::getMinValue(CR.getBitWidth()))
6121 : getConstant(APInt::getMaxValue(CR.getBitWidth()));
6123 MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
6124 : -CR.getUnsignedMin());
6125 return ExitLimit(Distance, MaxBECount);
6128 // If the step exactly divides the distance then unsigned divide computes the
6131 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6132 SCEVUDivision::divide(SE, Distance, Step, &Q, &R);
6135 getUDivExactExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6136 return ExitLimit(Exact, Exact);
6139 // If the condition controls loop exit (the loop exits only if the expression
6140 // is true) and the addition is no-wrap we can use unsigned divide to
6141 // compute the backedge count. In this case, the step may not divide the
6142 // distance, but we don't care because if the condition is "missed" the loop
6143 // will have undefined behavior due to wrapping.
6144 if (ControlsExit && AddRec->getNoWrapFlags(SCEV::FlagNW)) {
6146 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
6147 return ExitLimit(Exact, Exact);
6150 // Then, try to solve the above equation provided that Start is constant.
6151 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
6152 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
6153 -StartC->getValue()->getValue(),
6155 return getCouldNotCompute();
6158 /// HowFarToNonZero - Return the number of times a backedge checking the
6159 /// specified value for nonzero will execute. If not computable, return
6161 ScalarEvolution::ExitLimit
6162 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
6163 // Loops that look like: while (X == 0) are very strange indeed. We don't
6164 // handle them yet except for the trivial case. This could be expanded in the
6165 // future as needed.
6167 // If the value is a constant, check to see if it is known to be non-zero
6168 // already. If so, the backedge will execute zero times.
6169 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
6170 if (!C->getValue()->isNullValue())
6171 return getConstant(C->getType(), 0);
6172 return getCouldNotCompute(); // Otherwise it will loop infinitely.
6175 // We could implement others, but I really doubt anyone writes loops like
6176 // this, and if they did, they would already be constant folded.
6177 return getCouldNotCompute();
6180 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
6181 /// (which may not be an immediate predecessor) which has exactly one
6182 /// successor from which BB is reachable, or null if no such block is
6185 std::pair<BasicBlock *, BasicBlock *>
6186 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
6187 // If the block has a unique predecessor, then there is no path from the
6188 // predecessor to the block that does not go through the direct edge
6189 // from the predecessor to the block.
6190 if (BasicBlock *Pred = BB->getSinglePredecessor())
6191 return std::make_pair(Pred, BB);
6193 // A loop's header is defined to be a block that dominates the loop.
6194 // If the header has a unique predecessor outside the loop, it must be
6195 // a block that has exactly one successor that can reach the loop.
6196 if (Loop *L = LI->getLoopFor(BB))
6197 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
6199 return std::pair<BasicBlock *, BasicBlock *>();
6202 /// HasSameValue - SCEV structural equivalence is usually sufficient for
6203 /// testing whether two expressions are equal, however for the purposes of
6204 /// looking for a condition guarding a loop, it can be useful to be a little
6205 /// more general, since a front-end may have replicated the controlling
6208 static bool HasSameValue(const SCEV *A, const SCEV *B) {
6209 // Quick check to see if they are the same SCEV.
6210 if (A == B) return true;
6212 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
6213 // two different instructions with the same value. Check for this case.
6214 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
6215 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
6216 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
6217 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
6218 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
6221 // Otherwise assume they may have a different value.
6225 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
6226 /// predicate Pred. Return true iff any changes were made.
6228 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
6229 const SCEV *&LHS, const SCEV *&RHS,
6231 bool Changed = false;
6233 // If we hit the max recursion limit bail out.
6237 // Canonicalize a constant to the right side.
6238 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
6239 // Check for both operands constant.
6240 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
6241 if (ConstantExpr::getICmp(Pred,
6243 RHSC->getValue())->isNullValue())
6244 goto trivially_false;
6246 goto trivially_true;
6248 // Otherwise swap the operands to put the constant on the right.
6249 std::swap(LHS, RHS);
6250 Pred = ICmpInst::getSwappedPredicate(Pred);
6254 // If we're comparing an addrec with a value which is loop-invariant in the
6255 // addrec's loop, put the addrec on the left. Also make a dominance check,
6256 // as both operands could be addrecs loop-invariant in each other's loop.
6257 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
6258 const Loop *L = AR->getLoop();
6259 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
6260 std::swap(LHS, RHS);
6261 Pred = ICmpInst::getSwappedPredicate(Pred);
6266 // If there's a constant operand, canonicalize comparisons with boundary
6267 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
6268 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
6269 const APInt &RA = RC->getValue()->getValue();
6271 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6272 case ICmpInst::ICMP_EQ:
6273 case ICmpInst::ICMP_NE:
6274 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
6276 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
6277 if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
6278 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
6279 ME->getOperand(0)->isAllOnesValue()) {
6280 RHS = AE->getOperand(1);
6281 LHS = ME->getOperand(1);
6285 case ICmpInst::ICMP_UGE:
6286 if ((RA - 1).isMinValue()) {
6287 Pred = ICmpInst::ICMP_NE;
6288 RHS = getConstant(RA - 1);
6292 if (RA.isMaxValue()) {
6293 Pred = ICmpInst::ICMP_EQ;
6297 if (RA.isMinValue()) goto trivially_true;
6299 Pred = ICmpInst::ICMP_UGT;
6300 RHS = getConstant(RA - 1);
6303 case ICmpInst::ICMP_ULE:
6304 if ((RA + 1).isMaxValue()) {
6305 Pred = ICmpInst::ICMP_NE;
6306 RHS = getConstant(RA + 1);
6310 if (RA.isMinValue()) {
6311 Pred = ICmpInst::ICMP_EQ;
6315 if (RA.isMaxValue()) goto trivially_true;
6317 Pred = ICmpInst::ICMP_ULT;
6318 RHS = getConstant(RA + 1);
6321 case ICmpInst::ICMP_SGE:
6322 if ((RA - 1).isMinSignedValue()) {
6323 Pred = ICmpInst::ICMP_NE;
6324 RHS = getConstant(RA - 1);
6328 if (RA.isMaxSignedValue()) {
6329 Pred = ICmpInst::ICMP_EQ;
6333 if (RA.isMinSignedValue()) goto trivially_true;
6335 Pred = ICmpInst::ICMP_SGT;
6336 RHS = getConstant(RA - 1);
6339 case ICmpInst::ICMP_SLE:
6340 if ((RA + 1).isMaxSignedValue()) {
6341 Pred = ICmpInst::ICMP_NE;
6342 RHS = getConstant(RA + 1);
6346 if (RA.isMinSignedValue()) {
6347 Pred = ICmpInst::ICMP_EQ;
6351 if (RA.isMaxSignedValue()) goto trivially_true;
6353 Pred = ICmpInst::ICMP_SLT;
6354 RHS = getConstant(RA + 1);
6357 case ICmpInst::ICMP_UGT:
6358 if (RA.isMinValue()) {
6359 Pred = ICmpInst::ICMP_NE;
6363 if ((RA + 1).isMaxValue()) {
6364 Pred = ICmpInst::ICMP_EQ;
6365 RHS = getConstant(RA + 1);
6369 if (RA.isMaxValue()) goto trivially_false;
6371 case ICmpInst::ICMP_ULT:
6372 if (RA.isMaxValue()) {
6373 Pred = ICmpInst::ICMP_NE;
6377 if ((RA - 1).isMinValue()) {
6378 Pred = ICmpInst::ICMP_EQ;
6379 RHS = getConstant(RA - 1);
6383 if (RA.isMinValue()) goto trivially_false;
6385 case ICmpInst::ICMP_SGT:
6386 if (RA.isMinSignedValue()) {
6387 Pred = ICmpInst::ICMP_NE;
6391 if ((RA + 1).isMaxSignedValue()) {
6392 Pred = ICmpInst::ICMP_EQ;
6393 RHS = getConstant(RA + 1);
6397 if (RA.isMaxSignedValue()) goto trivially_false;
6399 case ICmpInst::ICMP_SLT:
6400 if (RA.isMaxSignedValue()) {
6401 Pred = ICmpInst::ICMP_NE;
6405 if ((RA - 1).isMinSignedValue()) {
6406 Pred = ICmpInst::ICMP_EQ;
6407 RHS = getConstant(RA - 1);
6411 if (RA.isMinSignedValue()) goto trivially_false;
6416 // Check for obvious equality.
6417 if (HasSameValue(LHS, RHS)) {
6418 if (ICmpInst::isTrueWhenEqual(Pred))
6419 goto trivially_true;
6420 if (ICmpInst::isFalseWhenEqual(Pred))
6421 goto trivially_false;
6424 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
6425 // adding or subtracting 1 from one of the operands.
6427 case ICmpInst::ICMP_SLE:
6428 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
6429 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6431 Pred = ICmpInst::ICMP_SLT;
6433 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
6434 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6436 Pred = ICmpInst::ICMP_SLT;
6440 case ICmpInst::ICMP_SGE:
6441 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
6442 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6444 Pred = ICmpInst::ICMP_SGT;
6446 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
6447 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6449 Pred = ICmpInst::ICMP_SGT;
6453 case ICmpInst::ICMP_ULE:
6454 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
6455 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
6457 Pred = ICmpInst::ICMP_ULT;
6459 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
6460 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
6462 Pred = ICmpInst::ICMP_ULT;
6466 case ICmpInst::ICMP_UGE:
6467 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
6468 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
6470 Pred = ICmpInst::ICMP_UGT;
6472 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
6473 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
6475 Pred = ICmpInst::ICMP_UGT;
6483 // TODO: More simplifications are possible here.
6485 // Recursively simplify until we either hit a recursion limit or nothing
6488 return SimplifyICmpOperands(Pred, LHS, RHS, Depth+1);
6494 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6495 Pred = ICmpInst::ICMP_EQ;
6500 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
6501 Pred = ICmpInst::ICMP_NE;
6505 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
6506 return getSignedRange(S).getSignedMax().isNegative();
6509 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
6510 return getSignedRange(S).getSignedMin().isStrictlyPositive();
6513 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
6514 return !getSignedRange(S).getSignedMin().isNegative();
6517 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
6518 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
6521 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
6522 return isKnownNegative(S) || isKnownPositive(S);
6525 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
6526 const SCEV *LHS, const SCEV *RHS) {
6527 // Canonicalize the inputs first.
6528 (void)SimplifyICmpOperands(Pred, LHS, RHS);
6530 // If LHS or RHS is an addrec, check to see if the condition is true in
6531 // every iteration of the loop.
6532 // If LHS and RHS are both addrec, both conditions must be true in
6533 // every iteration of the loop.
6534 const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
6535 const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
6536 bool LeftGuarded = false;
6537 bool RightGuarded = false;
6539 const Loop *L = LAR->getLoop();
6540 if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
6541 isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
6542 if (!RAR) return true;
6547 const Loop *L = RAR->getLoop();
6548 if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
6549 isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
6550 if (!LAR) return true;
6551 RightGuarded = true;
6554 if (LeftGuarded && RightGuarded)
6557 // Otherwise see what can be done with known constant ranges.
6558 return isKnownPredicateWithRanges(Pred, LHS, RHS);
6562 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
6563 const SCEV *LHS, const SCEV *RHS) {
6564 if (HasSameValue(LHS, RHS))
6565 return ICmpInst::isTrueWhenEqual(Pred);
6567 // This code is split out from isKnownPredicate because it is called from
6568 // within isLoopEntryGuardedByCond.
6571 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6572 case ICmpInst::ICMP_SGT:
6573 std::swap(LHS, RHS);
6574 case ICmpInst::ICMP_SLT: {
6575 ConstantRange LHSRange = getSignedRange(LHS);
6576 ConstantRange RHSRange = getSignedRange(RHS);
6577 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
6579 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
6583 case ICmpInst::ICMP_SGE:
6584 std::swap(LHS, RHS);
6585 case ICmpInst::ICMP_SLE: {
6586 ConstantRange LHSRange = getSignedRange(LHS);
6587 ConstantRange RHSRange = getSignedRange(RHS);
6588 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
6590 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
6594 case ICmpInst::ICMP_UGT:
6595 std::swap(LHS, RHS);
6596 case ICmpInst::ICMP_ULT: {
6597 ConstantRange LHSRange = getUnsignedRange(LHS);
6598 ConstantRange RHSRange = getUnsignedRange(RHS);
6599 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
6601 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
6605 case ICmpInst::ICMP_UGE:
6606 std::swap(LHS, RHS);
6607 case ICmpInst::ICMP_ULE: {
6608 ConstantRange LHSRange = getUnsignedRange(LHS);
6609 ConstantRange RHSRange = getUnsignedRange(RHS);
6610 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
6612 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
6616 case ICmpInst::ICMP_NE: {
6617 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
6619 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
6622 const SCEV *Diff = getMinusSCEV(LHS, RHS);
6623 if (isKnownNonZero(Diff))
6627 case ICmpInst::ICMP_EQ:
6628 // The check at the top of the function catches the case where
6629 // the values are known to be equal.
6635 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
6636 /// protected by a conditional between LHS and RHS. This is used to
6637 /// to eliminate casts.
6639 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
6640 ICmpInst::Predicate Pred,
6641 const SCEV *LHS, const SCEV *RHS) {
6642 // Interpret a null as meaning no loop, where there is obviously no guard
6643 // (interprocedural conditions notwithstanding).
6644 if (!L) return true;
6646 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
6648 BasicBlock *Latch = L->getLoopLatch();
6652 BranchInst *LoopContinuePredicate =
6653 dyn_cast<BranchInst>(Latch->getTerminator());
6654 if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
6655 isImpliedCond(Pred, LHS, RHS,
6656 LoopContinuePredicate->getCondition(),
6657 LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
6660 // Check conditions due to any @llvm.assume intrinsics.
6661 for (auto &CI : AT->assumptions(F)) {
6662 if (!DT->dominates(CI, Latch->getTerminator()))
6665 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
6672 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
6673 /// by a conditional between LHS and RHS. This is used to help avoid max
6674 /// expressions in loop trip counts, and to eliminate casts.
6676 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
6677 ICmpInst::Predicate Pred,
6678 const SCEV *LHS, const SCEV *RHS) {
6679 // Interpret a null as meaning no loop, where there is obviously no guard
6680 // (interprocedural conditions notwithstanding).
6681 if (!L) return false;
6683 if (isKnownPredicateWithRanges(Pred, LHS, RHS)) return true;
6685 // Starting at the loop predecessor, climb up the predecessor chain, as long
6686 // as there are predecessors that can be found that have unique successors
6687 // leading to the original header.
6688 for (std::pair<BasicBlock *, BasicBlock *>
6689 Pair(L->getLoopPredecessor(), L->getHeader());
6691 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
6693 BranchInst *LoopEntryPredicate =
6694 dyn_cast<BranchInst>(Pair.first->getTerminator());
6695 if (!LoopEntryPredicate ||
6696 LoopEntryPredicate->isUnconditional())
6699 if (isImpliedCond(Pred, LHS, RHS,
6700 LoopEntryPredicate->getCondition(),
6701 LoopEntryPredicate->getSuccessor(0) != Pair.second))
6705 // Check conditions due to any @llvm.assume intrinsics.
6706 for (auto &CI : AT->assumptions(F)) {
6707 if (!DT->dominates(CI, L->getHeader()))
6710 if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
6717 /// RAII wrapper to prevent recursive application of isImpliedCond.
6718 /// ScalarEvolution's PendingLoopPredicates set must be empty unless we are
6719 /// currently evaluating isImpliedCond.
6720 struct MarkPendingLoopPredicate {
6722 DenseSet<Value*> &LoopPreds;
6725 MarkPendingLoopPredicate(Value *C, DenseSet<Value*> &LP)
6726 : Cond(C), LoopPreds(LP) {
6727 Pending = !LoopPreds.insert(Cond).second;
6729 ~MarkPendingLoopPredicate() {
6731 LoopPreds.erase(Cond);
6735 /// isImpliedCond - Test whether the condition described by Pred, LHS,
6736 /// and RHS is true whenever the given Cond value evaluates to true.
6737 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
6738 const SCEV *LHS, const SCEV *RHS,
6739 Value *FoundCondValue,
6741 MarkPendingLoopPredicate Mark(FoundCondValue, PendingLoopPredicates);
6745 // Recursively handle And and Or conditions.
6746 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
6747 if (BO->getOpcode() == Instruction::And) {
6749 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6750 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6751 } else if (BO->getOpcode() == Instruction::Or) {
6753 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6754 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6758 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
6759 if (!ICI) return false;
6761 // Bail if the ICmp's operands' types are wider than the needed type
6762 // before attempting to call getSCEV on them. This avoids infinite
6763 // recursion, since the analysis of widening casts can require loop
6764 // exit condition information for overflow checking, which would
6766 if (getTypeSizeInBits(LHS->getType()) <
6767 getTypeSizeInBits(ICI->getOperand(0)->getType()))
6770 // Now that we found a conditional branch that dominates the loop or controls
6771 // the loop latch. Check to see if it is the comparison we are looking for.
6772 ICmpInst::Predicate FoundPred;
6774 FoundPred = ICI->getInversePredicate();
6776 FoundPred = ICI->getPredicate();
6778 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
6779 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
6781 // Balance the types. The case where FoundLHS' type is wider than
6782 // LHS' type is checked for above.
6783 if (getTypeSizeInBits(LHS->getType()) >
6784 getTypeSizeInBits(FoundLHS->getType())) {
6785 if (CmpInst::isSigned(FoundPred)) {
6786 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
6787 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
6789 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
6790 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
6794 // Canonicalize the query to match the way instcombine will have
6795 // canonicalized the comparison.
6796 if (SimplifyICmpOperands(Pred, LHS, RHS))
6798 return CmpInst::isTrueWhenEqual(Pred);
6799 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
6800 if (FoundLHS == FoundRHS)
6801 return CmpInst::isFalseWhenEqual(FoundPred);
6803 // Check to see if we can make the LHS or RHS match.
6804 if (LHS == FoundRHS || RHS == FoundLHS) {
6805 if (isa<SCEVConstant>(RHS)) {
6806 std::swap(FoundLHS, FoundRHS);
6807 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
6809 std::swap(LHS, RHS);
6810 Pred = ICmpInst::getSwappedPredicate(Pred);
6814 // Check whether the found predicate is the same as the desired predicate.
6815 if (FoundPred == Pred)
6816 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
6818 // Check whether swapping the found predicate makes it the same as the
6819 // desired predicate.
6820 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
6821 if (isa<SCEVConstant>(RHS))
6822 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
6824 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
6825 RHS, LHS, FoundLHS, FoundRHS);
6828 // Check if we can make progress by sharpening ranges.
6829 if (FoundPred == ICmpInst::ICMP_NE &&
6830 (isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
6832 const SCEVConstant *C = nullptr;
6833 const SCEV *V = nullptr;
6835 if (isa<SCEVConstant>(FoundLHS)) {
6836 C = cast<SCEVConstant>(FoundLHS);
6839 C = cast<SCEVConstant>(FoundRHS);
6843 // The guarding predicate tells us that C != V. If the known range
6844 // of V is [C, t), we can sharpen the range to [C + 1, t). The
6845 // range we consider has to correspond to same signedness as the
6846 // predicate we're interested in folding.
6848 APInt Min = ICmpInst::isSigned(Pred) ?
6849 getSignedRange(V).getSignedMin() : getUnsignedRange(V).getUnsignedMin();
6851 if (Min == C->getValue()->getValue()) {
6852 // Given (V >= Min && V != Min) we conclude V >= (Min + 1).
6853 // This is true even if (Min + 1) wraps around -- in case of
6854 // wraparound, (Min + 1) < Min, so (V >= Min => V >= (Min + 1)).
6856 APInt SharperMin = Min + 1;
6859 case ICmpInst::ICMP_SGE:
6860 case ICmpInst::ICMP_UGE:
6861 // We know V `Pred` SharperMin. If this implies LHS `Pred`
6863 if (isImpliedCondOperands(Pred, LHS, RHS, V,
6864 getConstant(SharperMin)))
6867 case ICmpInst::ICMP_SGT:
6868 case ICmpInst::ICMP_UGT:
6869 // We know from the range information that (V `Pred` Min ||
6870 // V == Min). We know from the guarding condition that !(V
6871 // == Min). This gives us
6873 // V `Pred` Min || V == Min && !(V == Min)
6876 // If V `Pred` Min implies LHS `Pred` RHS, we're done.
6878 if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
6888 // Check whether the actual condition is beyond sufficient.
6889 if (FoundPred == ICmpInst::ICMP_EQ)
6890 if (ICmpInst::isTrueWhenEqual(Pred))
6891 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
6893 if (Pred == ICmpInst::ICMP_NE)
6894 if (!ICmpInst::isTrueWhenEqual(FoundPred))
6895 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
6898 // Otherwise assume the worst.
6902 /// isImpliedCondOperands - Test whether the condition described by Pred,
6903 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
6904 /// and FoundRHS is true.
6905 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
6906 const SCEV *LHS, const SCEV *RHS,
6907 const SCEV *FoundLHS,
6908 const SCEV *FoundRHS) {
6909 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
6910 FoundLHS, FoundRHS) ||
6911 // ~x < ~y --> x > y
6912 isImpliedCondOperandsHelper(Pred, LHS, RHS,
6913 getNotSCEV(FoundRHS),
6914 getNotSCEV(FoundLHS));
6917 /// isImpliedCondOperandsHelper - Test whether the condition described by
6918 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
6919 /// FoundLHS, and FoundRHS is true.
6921 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
6922 const SCEV *LHS, const SCEV *RHS,
6923 const SCEV *FoundLHS,
6924 const SCEV *FoundRHS) {
6926 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6927 case ICmpInst::ICMP_EQ:
6928 case ICmpInst::ICMP_NE:
6929 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
6932 case ICmpInst::ICMP_SLT:
6933 case ICmpInst::ICMP_SLE:
6934 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
6935 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
6938 case ICmpInst::ICMP_SGT:
6939 case ICmpInst::ICMP_SGE:
6940 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
6941 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
6944 case ICmpInst::ICMP_ULT:
6945 case ICmpInst::ICMP_ULE:
6946 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
6947 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
6950 case ICmpInst::ICMP_UGT:
6951 case ICmpInst::ICMP_UGE:
6952 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
6953 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
6961 // Verify if an linear IV with positive stride can overflow when in a
6962 // less-than comparison, knowing the invariant term of the comparison, the
6963 // stride and the knowledge of NSW/NUW flags on the recurrence.
6964 bool ScalarEvolution::doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride,
6965 bool IsSigned, bool NoWrap) {
6966 if (NoWrap) return false;
6968 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6969 const SCEV *One = getConstant(Stride->getType(), 1);
6972 APInt MaxRHS = getSignedRange(RHS).getSignedMax();
6973 APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
6974 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
6977 // SMaxRHS + SMaxStrideMinusOne > SMaxValue => overflow!
6978 return (MaxValue - MaxStrideMinusOne).slt(MaxRHS);
6981 APInt MaxRHS = getUnsignedRange(RHS).getUnsignedMax();
6982 APInt MaxValue = APInt::getMaxValue(BitWidth);
6983 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
6986 // UMaxRHS + UMaxStrideMinusOne > UMaxValue => overflow!
6987 return (MaxValue - MaxStrideMinusOne).ult(MaxRHS);
6990 // Verify if an linear IV with negative stride can overflow when in a
6991 // greater-than comparison, knowing the invariant term of the comparison,
6992 // the stride and the knowledge of NSW/NUW flags on the recurrence.
6993 bool ScalarEvolution::doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride,
6994 bool IsSigned, bool NoWrap) {
6995 if (NoWrap) return false;
6997 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6998 const SCEV *One = getConstant(Stride->getType(), 1);
7001 APInt MinRHS = getSignedRange(RHS).getSignedMin();
7002 APInt MinValue = APInt::getSignedMinValue(BitWidth);
7003 APInt MaxStrideMinusOne = getSignedRange(getMinusSCEV(Stride, One))
7006 // SMinRHS - SMaxStrideMinusOne < SMinValue => overflow!
7007 return (MinValue + MaxStrideMinusOne).sgt(MinRHS);
7010 APInt MinRHS = getUnsignedRange(RHS).getUnsignedMin();
7011 APInt MinValue = APInt::getMinValue(BitWidth);
7012 APInt MaxStrideMinusOne = getUnsignedRange(getMinusSCEV(Stride, One))
7015 // UMinRHS - UMaxStrideMinusOne < UMinValue => overflow!
7016 return (MinValue + MaxStrideMinusOne).ugt(MinRHS);
7019 // Compute the backedge taken count knowing the interval difference, the
7020 // stride and presence of the equality in the comparison.
7021 const SCEV *ScalarEvolution::computeBECount(const SCEV *Delta, const SCEV *Step,
7023 const SCEV *One = getConstant(Step->getType(), 1);
7024 Delta = Equality ? getAddExpr(Delta, Step)
7025 : getAddExpr(Delta, getMinusSCEV(Step, One));
7026 return getUDivExpr(Delta, Step);
7029 /// HowManyLessThans - Return the number of times a backedge containing the
7030 /// specified less-than comparison will execute. If not computable, return
7031 /// CouldNotCompute.
7033 /// @param ControlsExit is true when the LHS < RHS condition directly controls
7034 /// the branch (loops exits only if condition is true). In this case, we can use
7035 /// NoWrapFlags to skip overflow checks.
7036 ScalarEvolution::ExitLimit
7037 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
7038 const Loop *L, bool IsSigned,
7039 bool ControlsExit) {
7040 // We handle only IV < Invariant
7041 if (!isLoopInvariant(RHS, L))
7042 return getCouldNotCompute();
7044 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
7046 // Avoid weird loops
7047 if (!IV || IV->getLoop() != L || !IV->isAffine())
7048 return getCouldNotCompute();
7050 bool NoWrap = ControlsExit &&
7051 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
7053 const SCEV *Stride = IV->getStepRecurrence(*this);
7055 // Avoid negative or zero stride values
7056 if (!isKnownPositive(Stride))
7057 return getCouldNotCompute();
7059 // Avoid proven overflow cases: this will ensure that the backedge taken count
7060 // will not generate any unsigned overflow. Relaxed no-overflow conditions
7061 // exploit NoWrapFlags, allowing to optimize in presence of undefined
7062 // behaviors like the case of C language.
7063 if (!Stride->isOne() && doesIVOverflowOnLT(RHS, Stride, IsSigned, NoWrap))
7064 return getCouldNotCompute();
7066 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SLT
7067 : ICmpInst::ICMP_ULT;
7068 const SCEV *Start = IV->getStart();
7069 const SCEV *End = RHS;
7070 if (!isLoopEntryGuardedByCond(L, Cond, getMinusSCEV(Start, Stride), RHS)) {
7071 const SCEV *Diff = getMinusSCEV(RHS, Start);
7072 // If we have NoWrap set, then we can assume that the increment won't
7073 // overflow, in which case if RHS - Start is a constant, we don't need to
7074 // do a max operation since we can just figure it out statically
7075 if (NoWrap && isa<SCEVConstant>(Diff)) {
7076 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
7080 End = IsSigned ? getSMaxExpr(RHS, Start)
7081 : getUMaxExpr(RHS, Start);
7084 const SCEV *BECount = computeBECount(getMinusSCEV(End, Start), Stride, false);
7086 APInt MinStart = IsSigned ? getSignedRange(Start).getSignedMin()
7087 : getUnsignedRange(Start).getUnsignedMin();
7089 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
7090 : getUnsignedRange(Stride).getUnsignedMin();
7092 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
7093 APInt Limit = IsSigned ? APInt::getSignedMaxValue(BitWidth) - (MinStride - 1)
7094 : APInt::getMaxValue(BitWidth) - (MinStride - 1);
7096 // Although End can be a MAX expression we estimate MaxEnd considering only
7097 // the case End = RHS. This is safe because in the other case (End - Start)
7098 // is zero, leading to a zero maximum backedge taken count.
7100 IsSigned ? APIntOps::smin(getSignedRange(RHS).getSignedMax(), Limit)
7101 : APIntOps::umin(getUnsignedRange(RHS).getUnsignedMax(), Limit);
7103 const SCEV *MaxBECount;
7104 if (isa<SCEVConstant>(BECount))
7105 MaxBECount = BECount;
7107 MaxBECount = computeBECount(getConstant(MaxEnd - MinStart),
7108 getConstant(MinStride), false);
7110 if (isa<SCEVCouldNotCompute>(MaxBECount))
7111 MaxBECount = BECount;
7113 return ExitLimit(BECount, MaxBECount);
7116 ScalarEvolution::ExitLimit
7117 ScalarEvolution::HowManyGreaterThans(const SCEV *LHS, const SCEV *RHS,
7118 const Loop *L, bool IsSigned,
7119 bool ControlsExit) {
7120 // We handle only IV > Invariant
7121 if (!isLoopInvariant(RHS, L))
7122 return getCouldNotCompute();
7124 const SCEVAddRecExpr *IV = dyn_cast<SCEVAddRecExpr>(LHS);
7126 // Avoid weird loops
7127 if (!IV || IV->getLoop() != L || !IV->isAffine())
7128 return getCouldNotCompute();
7130 bool NoWrap = ControlsExit &&
7131 IV->getNoWrapFlags(IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW);
7133 const SCEV *Stride = getNegativeSCEV(IV->getStepRecurrence(*this));
7135 // Avoid negative or zero stride values
7136 if (!isKnownPositive(Stride))
7137 return getCouldNotCompute();
7139 // Avoid proven overflow cases: this will ensure that the backedge taken count
7140 // will not generate any unsigned overflow. Relaxed no-overflow conditions
7141 // exploit NoWrapFlags, allowing to optimize in presence of undefined
7142 // behaviors like the case of C language.
7143 if (!Stride->isOne() && doesIVOverflowOnGT(RHS, Stride, IsSigned, NoWrap))
7144 return getCouldNotCompute();
7146 ICmpInst::Predicate Cond = IsSigned ? ICmpInst::ICMP_SGT
7147 : ICmpInst::ICMP_UGT;
7149 const SCEV *Start = IV->getStart();
7150 const SCEV *End = RHS;
7151 if (!isLoopEntryGuardedByCond(L, Cond, getAddExpr(Start, Stride), RHS)) {
7152 const SCEV *Diff = getMinusSCEV(RHS, Start);
7153 // If we have NoWrap set, then we can assume that the increment won't
7154 // overflow, in which case if RHS - Start is a constant, we don't need to
7155 // do a max operation since we can just figure it out statically
7156 if (NoWrap && isa<SCEVConstant>(Diff)) {
7157 APInt D = dyn_cast<const SCEVConstant>(Diff)->getValue()->getValue();
7158 if (!D.isNegative())
7161 End = IsSigned ? getSMinExpr(RHS, Start)
7162 : getUMinExpr(RHS, Start);
7165 const SCEV *BECount = computeBECount(getMinusSCEV(Start, End), Stride, false);
7167 APInt MaxStart = IsSigned ? getSignedRange(Start).getSignedMax()
7168 : getUnsignedRange(Start).getUnsignedMax();
7170 APInt MinStride = IsSigned ? getSignedRange(Stride).getSignedMin()
7171 : getUnsignedRange(Stride).getUnsignedMin();
7173 unsigned BitWidth = getTypeSizeInBits(LHS->getType());
7174 APInt Limit = IsSigned ? APInt::getSignedMinValue(BitWidth) + (MinStride - 1)
7175 : APInt::getMinValue(BitWidth) + (MinStride - 1);
7177 // Although End can be a MIN expression we estimate MinEnd considering only
7178 // the case End = RHS. This is safe because in the other case (Start - End)
7179 // is zero, leading to a zero maximum backedge taken count.
7181 IsSigned ? APIntOps::smax(getSignedRange(RHS).getSignedMin(), Limit)
7182 : APIntOps::umax(getUnsignedRange(RHS).getUnsignedMin(), Limit);
7185 const SCEV *MaxBECount = getCouldNotCompute();
7186 if (isa<SCEVConstant>(BECount))
7187 MaxBECount = BECount;
7189 MaxBECount = computeBECount(getConstant(MaxStart - MinEnd),
7190 getConstant(MinStride), false);
7192 if (isa<SCEVCouldNotCompute>(MaxBECount))
7193 MaxBECount = BECount;
7195 return ExitLimit(BECount, MaxBECount);
7198 /// getNumIterationsInRange - Return the number of iterations of this loop that
7199 /// produce values in the specified constant range. Another way of looking at
7200 /// this is that it returns the first iteration number where the value is not in
7201 /// the condition, thus computing the exit count. If the iteration count can't
7202 /// be computed, an instance of SCEVCouldNotCompute is returned.
7203 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
7204 ScalarEvolution &SE) const {
7205 if (Range.isFullSet()) // Infinite loop.
7206 return SE.getCouldNotCompute();
7208 // If the start is a non-zero constant, shift the range to simplify things.
7209 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
7210 if (!SC->getValue()->isZero()) {
7211 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
7212 Operands[0] = SE.getConstant(SC->getType(), 0);
7213 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
7214 getNoWrapFlags(FlagNW));
7215 if (const SCEVAddRecExpr *ShiftedAddRec =
7216 dyn_cast<SCEVAddRecExpr>(Shifted))
7217 return ShiftedAddRec->getNumIterationsInRange(
7218 Range.subtract(SC->getValue()->getValue()), SE);
7219 // This is strange and shouldn't happen.
7220 return SE.getCouldNotCompute();
7223 // The only time we can solve this is when we have all constant indices.
7224 // Otherwise, we cannot determine the overflow conditions.
7225 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
7226 if (!isa<SCEVConstant>(getOperand(i)))
7227 return SE.getCouldNotCompute();
7230 // Okay at this point we know that all elements of the chrec are constants and
7231 // that the start element is zero.
7233 // First check to see if the range contains zero. If not, the first
7235 unsigned BitWidth = SE.getTypeSizeInBits(getType());
7236 if (!Range.contains(APInt(BitWidth, 0)))
7237 return SE.getConstant(getType(), 0);
7240 // If this is an affine expression then we have this situation:
7241 // Solve {0,+,A} in Range === Ax in Range
7243 // We know that zero is in the range. If A is positive then we know that
7244 // the upper value of the range must be the first possible exit value.
7245 // If A is negative then the lower of the range is the last possible loop
7246 // value. Also note that we already checked for a full range.
7247 APInt One(BitWidth,1);
7248 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
7249 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
7251 // The exit value should be (End+A)/A.
7252 APInt ExitVal = (End + A).udiv(A);
7253 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
7255 // Evaluate at the exit value. If we really did fall out of the valid
7256 // range, then we computed our trip count, otherwise wrap around or other
7257 // things must have happened.
7258 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
7259 if (Range.contains(Val->getValue()))
7260 return SE.getCouldNotCompute(); // Something strange happened
7262 // Ensure that the previous value is in the range. This is a sanity check.
7263 assert(Range.contains(
7264 EvaluateConstantChrecAtConstant(this,
7265 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
7266 "Linear scev computation is off in a bad way!");
7267 return SE.getConstant(ExitValue);
7268 } else if (isQuadratic()) {
7269 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
7270 // quadratic equation to solve it. To do this, we must frame our problem in
7271 // terms of figuring out when zero is crossed, instead of when
7272 // Range.getUpper() is crossed.
7273 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
7274 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
7275 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
7276 // getNoWrapFlags(FlagNW)
7279 // Next, solve the constructed addrec
7280 std::pair<const SCEV *,const SCEV *> Roots =
7281 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
7282 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
7283 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
7285 // Pick the smallest positive root value.
7286 if (ConstantInt *CB =
7287 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
7288 R1->getValue(), R2->getValue()))) {
7289 if (CB->getZExtValue() == false)
7290 std::swap(R1, R2); // R1 is the minimum root now.
7292 // Make sure the root is not off by one. The returned iteration should
7293 // not be in the range, but the previous one should be. When solving
7294 // for "X*X < 5", for example, we should not return a root of 2.
7295 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
7298 if (Range.contains(R1Val->getValue())) {
7299 // The next iteration must be out of the range...
7300 ConstantInt *NextVal =
7301 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
7303 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
7304 if (!Range.contains(R1Val->getValue()))
7305 return SE.getConstant(NextVal);
7306 return SE.getCouldNotCompute(); // Something strange happened
7309 // If R1 was not in the range, then it is a good return value. Make
7310 // sure that R1-1 WAS in the range though, just in case.
7311 ConstantInt *NextVal =
7312 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
7313 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
7314 if (Range.contains(R1Val->getValue()))
7316 return SE.getCouldNotCompute(); // Something strange happened
7321 return SE.getCouldNotCompute();
7327 FindUndefs() : Found(false) {}
7329 bool follow(const SCEV *S) {
7330 if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
7331 if (isa<UndefValue>(C->getValue()))
7333 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
7334 if (isa<UndefValue>(C->getValue()))
7338 // Keep looking if we haven't found it yet.
7341 bool isDone() const {
7342 // Stop recursion if we have found an undef.
7348 // Return true when S contains at least an undef value.
7350 containsUndefs(const SCEV *S) {
7352 SCEVTraversal<FindUndefs> ST(F);
7359 // Collect all steps of SCEV expressions.
7360 struct SCEVCollectStrides {
7361 ScalarEvolution &SE;
7362 SmallVectorImpl<const SCEV *> &Strides;
7364 SCEVCollectStrides(ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &S)
7365 : SE(SE), Strides(S) {}
7367 bool follow(const SCEV *S) {
7368 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
7369 Strides.push_back(AR->getStepRecurrence(SE));
7372 bool isDone() const { return false; }
7375 // Collect all SCEVUnknown and SCEVMulExpr expressions.
7376 struct SCEVCollectTerms {
7377 SmallVectorImpl<const SCEV *> &Terms;
7379 SCEVCollectTerms(SmallVectorImpl<const SCEV *> &T)
7382 bool follow(const SCEV *S) {
7383 if (isa<SCEVUnknown>(S) || isa<SCEVMulExpr>(S)) {
7384 if (!containsUndefs(S))
7387 // Stop recursion: once we collected a term, do not walk its operands.
7394 bool isDone() const { return false; }
7398 /// Find parametric terms in this SCEVAddRecExpr.
7399 void SCEVAddRecExpr::collectParametricTerms(
7400 ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Terms) const {
7401 SmallVector<const SCEV *, 4> Strides;
7402 SCEVCollectStrides StrideCollector(SE, Strides);
7403 visitAll(this, StrideCollector);
7406 dbgs() << "Strides:\n";
7407 for (const SCEV *S : Strides)
7408 dbgs() << *S << "\n";
7411 for (const SCEV *S : Strides) {
7412 SCEVCollectTerms TermCollector(Terms);
7413 visitAll(S, TermCollector);
7417 dbgs() << "Terms:\n";
7418 for (const SCEV *T : Terms)
7419 dbgs() << *T << "\n";
7423 static bool findArrayDimensionsRec(ScalarEvolution &SE,
7424 SmallVectorImpl<const SCEV *> &Terms,
7425 SmallVectorImpl<const SCEV *> &Sizes) {
7426 int Last = Terms.size() - 1;
7427 const SCEV *Step = Terms[Last];
7429 // End of recursion.
7431 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Step)) {
7432 SmallVector<const SCEV *, 2> Qs;
7433 for (const SCEV *Op : M->operands())
7434 if (!isa<SCEVConstant>(Op))
7437 Step = SE.getMulExpr(Qs);
7440 Sizes.push_back(Step);
7444 for (const SCEV *&Term : Terms) {
7445 // Normalize the terms before the next call to findArrayDimensionsRec.
7447 SCEVSDivision::divide(SE, Term, Step, &Q, &R);
7449 // Bail out when GCD does not evenly divide one of the terms.
7456 // Remove all SCEVConstants.
7457 Terms.erase(std::remove_if(Terms.begin(), Terms.end(), [](const SCEV *E) {
7458 return isa<SCEVConstant>(E);
7462 if (Terms.size() > 0)
7463 if (!findArrayDimensionsRec(SE, Terms, Sizes))
7466 Sizes.push_back(Step);
7471 struct FindParameter {
7472 bool FoundParameter;
7473 FindParameter() : FoundParameter(false) {}
7475 bool follow(const SCEV *S) {
7476 if (isa<SCEVUnknown>(S)) {
7477 FoundParameter = true;
7478 // Stop recursion: we found a parameter.
7484 bool isDone() const {
7485 // Stop recursion if we have found a parameter.
7486 return FoundParameter;
7491 // Returns true when S contains at least a SCEVUnknown parameter.
7493 containsParameters(const SCEV *S) {
7495 SCEVTraversal<FindParameter> ST(F);
7498 return F.FoundParameter;
7501 // Returns true when one of the SCEVs of Terms contains a SCEVUnknown parameter.
7503 containsParameters(SmallVectorImpl<const SCEV *> &Terms) {
7504 for (const SCEV *T : Terms)
7505 if (containsParameters(T))
7510 // Return the number of product terms in S.
7511 static inline int numberOfTerms(const SCEV *S) {
7512 if (const SCEVMulExpr *Expr = dyn_cast<SCEVMulExpr>(S))
7513 return Expr->getNumOperands();
7517 static const SCEV *removeConstantFactors(ScalarEvolution &SE, const SCEV *T) {
7518 if (isa<SCEVConstant>(T))
7521 if (isa<SCEVUnknown>(T))
7524 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(T)) {
7525 SmallVector<const SCEV *, 2> Factors;
7526 for (const SCEV *Op : M->operands())
7527 if (!isa<SCEVConstant>(Op))
7528 Factors.push_back(Op);
7530 return SE.getMulExpr(Factors);
7536 /// Return the size of an element read or written by Inst.
7537 const SCEV *ScalarEvolution::getElementSize(Instruction *Inst) {
7539 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
7540 Ty = Store->getValueOperand()->getType();
7541 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
7542 Ty = Load->getType();
7546 Type *ETy = getEffectiveSCEVType(PointerType::getUnqual(Ty));
7547 return getSizeOfExpr(ETy, Ty);
7550 /// Second step of delinearization: compute the array dimensions Sizes from the
7551 /// set of Terms extracted from the memory access function of this SCEVAddRec.
7552 void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
7553 SmallVectorImpl<const SCEV *> &Sizes,
7554 const SCEV *ElementSize) const {
7556 if (Terms.size() < 1 || !ElementSize)
7559 // Early return when Terms do not contain parameters: we do not delinearize
7560 // non parametric SCEVs.
7561 if (!containsParameters(Terms))
7565 dbgs() << "Terms:\n";
7566 for (const SCEV *T : Terms)
7567 dbgs() << *T << "\n";
7570 // Remove duplicates.
7571 std::sort(Terms.begin(), Terms.end());
7572 Terms.erase(std::unique(Terms.begin(), Terms.end()), Terms.end());
7574 // Put larger terms first.
7575 std::sort(Terms.begin(), Terms.end(), [](const SCEV *LHS, const SCEV *RHS) {
7576 return numberOfTerms(LHS) > numberOfTerms(RHS);
7579 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
7581 // Divide all terms by the element size.
7582 for (const SCEV *&Term : Terms) {
7584 SCEVSDivision::divide(SE, Term, ElementSize, &Q, &R);
7588 SmallVector<const SCEV *, 4> NewTerms;
7590 // Remove constant factors.
7591 for (const SCEV *T : Terms)
7592 if (const SCEV *NewT = removeConstantFactors(SE, T))
7593 NewTerms.push_back(NewT);
7596 dbgs() << "Terms after sorting:\n";
7597 for (const SCEV *T : NewTerms)
7598 dbgs() << *T << "\n";
7601 if (NewTerms.empty() ||
7602 !findArrayDimensionsRec(SE, NewTerms, Sizes)) {
7607 // The last element to be pushed into Sizes is the size of an element.
7608 Sizes.push_back(ElementSize);
7611 dbgs() << "Sizes:\n";
7612 for (const SCEV *S : Sizes)
7613 dbgs() << *S << "\n";
7617 /// Third step of delinearization: compute the access functions for the
7618 /// Subscripts based on the dimensions in Sizes.
7619 void SCEVAddRecExpr::computeAccessFunctions(
7620 ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Subscripts,
7621 SmallVectorImpl<const SCEV *> &Sizes) const {
7623 // Early exit in case this SCEV is not an affine multivariate function.
7624 if (Sizes.empty() || !this->isAffine())
7627 const SCEV *Res = this;
7628 int Last = Sizes.size() - 1;
7629 for (int i = Last; i >= 0; i--) {
7631 SCEVSDivision::divide(SE, Res, Sizes[i], &Q, &R);
7634 dbgs() << "Res: " << *Res << "\n";
7635 dbgs() << "Sizes[i]: " << *Sizes[i] << "\n";
7636 dbgs() << "Res divided by Sizes[i]:\n";
7637 dbgs() << "Quotient: " << *Q << "\n";
7638 dbgs() << "Remainder: " << *R << "\n";
7643 // Do not record the last subscript corresponding to the size of elements in
7647 // Bail out if the remainder is too complex.
7648 if (isa<SCEVAddRecExpr>(R)) {
7657 // Record the access function for the current subscript.
7658 Subscripts.push_back(R);
7661 // Also push in last position the remainder of the last division: it will be
7662 // the access function of the innermost dimension.
7663 Subscripts.push_back(Res);
7665 std::reverse(Subscripts.begin(), Subscripts.end());
7668 dbgs() << "Subscripts:\n";
7669 for (const SCEV *S : Subscripts)
7670 dbgs() << *S << "\n";
7674 /// Splits the SCEV into two vectors of SCEVs representing the subscripts and
7675 /// sizes of an array access. Returns the remainder of the delinearization that
7676 /// is the offset start of the array. The SCEV->delinearize algorithm computes
7677 /// the multiples of SCEV coefficients: that is a pattern matching of sub
7678 /// expressions in the stride and base of a SCEV corresponding to the
7679 /// computation of a GCD (greatest common divisor) of base and stride. When
7680 /// SCEV->delinearize fails, it returns the SCEV unchanged.
7682 /// For example: when analyzing the memory access A[i][j][k] in this loop nest
7684 /// void foo(long n, long m, long o, double A[n][m][o]) {
7686 /// for (long i = 0; i < n; i++)
7687 /// for (long j = 0; j < m; j++)
7688 /// for (long k = 0; k < o; k++)
7689 /// A[i][j][k] = 1.0;
7692 /// the delinearization input is the following AddRec SCEV:
7694 /// AddRec: {{{%A,+,(8 * %m * %o)}<%for.i>,+,(8 * %o)}<%for.j>,+,8}<%for.k>
7696 /// From this SCEV, we are able to say that the base offset of the access is %A
7697 /// because it appears as an offset that does not divide any of the strides in
7700 /// CHECK: Base offset: %A
7702 /// and then SCEV->delinearize determines the size of some of the dimensions of
7703 /// the array as these are the multiples by which the strides are happening:
7705 /// CHECK: ArrayDecl[UnknownSize][%m][%o] with elements of sizeof(double) bytes.
7707 /// Note that the outermost dimension remains of UnknownSize because there are
7708 /// no strides that would help identifying the size of the last dimension: when
7709 /// the array has been statically allocated, one could compute the size of that
7710 /// dimension by dividing the overall size of the array by the size of the known
7711 /// dimensions: %m * %o * 8.
7713 /// Finally delinearize provides the access functions for the array reference
7714 /// that does correspond to A[i][j][k] of the above C testcase:
7716 /// CHECK: ArrayRef[{0,+,1}<%for.i>][{0,+,1}<%for.j>][{0,+,1}<%for.k>]
7718 /// The testcases are checking the output of a function pass:
7719 /// DelinearizationPass that walks through all loads and stores of a function
7720 /// asking for the SCEV of the memory access with respect to all enclosing
7721 /// loops, calling SCEV->delinearize on that and printing the results.
7723 void SCEVAddRecExpr::delinearize(ScalarEvolution &SE,
7724 SmallVectorImpl<const SCEV *> &Subscripts,
7725 SmallVectorImpl<const SCEV *> &Sizes,
7726 const SCEV *ElementSize) const {
7727 // First step: collect parametric terms.
7728 SmallVector<const SCEV *, 4> Terms;
7729 collectParametricTerms(SE, Terms);
7734 // Second step: find subscript sizes.
7735 SE.findArrayDimensions(Terms, Sizes, ElementSize);
7740 // Third step: compute the access functions for each subscript.
7741 computeAccessFunctions(SE, Subscripts, Sizes);
7743 if (Subscripts.empty())
7747 dbgs() << "succeeded to delinearize " << *this << "\n";
7748 dbgs() << "ArrayDecl[UnknownSize]";
7749 for (const SCEV *S : Sizes)
7750 dbgs() << "[" << *S << "]";
7752 dbgs() << "\nArrayRef";
7753 for (const SCEV *S : Subscripts)
7754 dbgs() << "[" << *S << "]";
7759 //===----------------------------------------------------------------------===//
7760 // SCEVCallbackVH Class Implementation
7761 //===----------------------------------------------------------------------===//
7763 void ScalarEvolution::SCEVCallbackVH::deleted() {
7764 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
7765 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
7766 SE->ConstantEvolutionLoopExitValue.erase(PN);
7767 SE->ValueExprMap.erase(getValPtr());
7768 // this now dangles!
7771 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
7772 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
7774 // Forget all the expressions associated with users of the old value,
7775 // so that future queries will recompute the expressions using the new
7777 Value *Old = getValPtr();
7778 SmallVector<User *, 16> Worklist(Old->user_begin(), Old->user_end());
7779 SmallPtrSet<User *, 8> Visited;
7780 while (!Worklist.empty()) {
7781 User *U = Worklist.pop_back_val();
7782 // Deleting the Old value will cause this to dangle. Postpone
7783 // that until everything else is done.
7786 if (!Visited.insert(U))
7788 if (PHINode *PN = dyn_cast<PHINode>(U))
7789 SE->ConstantEvolutionLoopExitValue.erase(PN);
7790 SE->ValueExprMap.erase(U);
7791 Worklist.insert(Worklist.end(), U->user_begin(), U->user_end());
7793 // Delete the Old value.
7794 if (PHINode *PN = dyn_cast<PHINode>(Old))
7795 SE->ConstantEvolutionLoopExitValue.erase(PN);
7796 SE->ValueExprMap.erase(Old);
7797 // this now dangles!
7800 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
7801 : CallbackVH(V), SE(se) {}
7803 //===----------------------------------------------------------------------===//
7804 // ScalarEvolution Class Implementation
7805 //===----------------------------------------------------------------------===//
7807 ScalarEvolution::ScalarEvolution()
7808 : FunctionPass(ID), ValuesAtScopes(64), LoopDispositions(64),
7809 BlockDispositions(64), FirstUnknown(nullptr) {
7810 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
7813 bool ScalarEvolution::runOnFunction(Function &F) {
7815 AT = &getAnalysis<AssumptionTracker>();
7816 LI = &getAnalysis<LoopInfo>();
7817 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
7818 DL = DLP ? &DLP->getDataLayout() : nullptr;
7819 TLI = &getAnalysis<TargetLibraryInfo>();
7820 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
7824 void ScalarEvolution::releaseMemory() {
7825 // Iterate through all the SCEVUnknown instances and call their
7826 // destructors, so that they release their references to their values.
7827 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
7829 FirstUnknown = nullptr;
7831 ValueExprMap.clear();
7833 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
7834 // that a loop had multiple computable exits.
7835 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
7836 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end();
7841 assert(PendingLoopPredicates.empty() && "isImpliedCond garbage");
7843 BackedgeTakenCounts.clear();
7844 ConstantEvolutionLoopExitValue.clear();
7845 ValuesAtScopes.clear();
7846 LoopDispositions.clear();
7847 BlockDispositions.clear();
7848 UnsignedRanges.clear();
7849 SignedRanges.clear();
7850 UniqueSCEVs.clear();
7851 SCEVAllocator.Reset();
7854 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
7855 AU.setPreservesAll();
7856 AU.addRequired<AssumptionTracker>();
7857 AU.addRequiredTransitive<LoopInfo>();
7858 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
7859 AU.addRequired<TargetLibraryInfo>();
7862 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
7863 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
7866 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
7868 // Print all inner loops first
7869 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
7870 PrintLoopInfo(OS, SE, *I);
7873 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
7876 SmallVector<BasicBlock *, 8> ExitBlocks;
7877 L->getExitBlocks(ExitBlocks);
7878 if (ExitBlocks.size() != 1)
7879 OS << "<multiple exits> ";
7881 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
7882 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
7884 OS << "Unpredictable backedge-taken count. ";
7889 L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
7892 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
7893 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
7895 OS << "Unpredictable max backedge-taken count. ";
7901 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
7902 // ScalarEvolution's implementation of the print method is to print
7903 // out SCEV values of all instructions that are interesting. Doing
7904 // this potentially causes it to create new SCEV objects though,
7905 // which technically conflicts with the const qualifier. This isn't
7906 // observable from outside the class though, so casting away the
7907 // const isn't dangerous.
7908 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
7910 OS << "Classifying expressions for: ";
7911 F->printAsOperand(OS, /*PrintType=*/false);
7913 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
7914 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
7917 const SCEV *SV = SE.getSCEV(&*I);
7920 const Loop *L = LI->getLoopFor((*I).getParent());
7922 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
7929 OS << "\t\t" "Exits: ";
7930 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
7931 if (!SE.isLoopInvariant(ExitValue, L)) {
7932 OS << "<<Unknown>>";
7941 OS << "Determining loop execution counts for: ";
7942 F->printAsOperand(OS, /*PrintType=*/false);
7944 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
7945 PrintLoopInfo(OS, &SE, *I);
7948 ScalarEvolution::LoopDisposition
7949 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
7950 SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values = LoopDispositions[S];
7951 for (unsigned u = 0; u < Values.size(); u++) {
7952 if (Values[u].first == L)
7953 return Values[u].second;
7955 Values.push_back(std::make_pair(L, LoopVariant));
7956 LoopDisposition D = computeLoopDisposition(S, L);
7957 SmallVector<std::pair<const Loop *, LoopDisposition>, 2> &Values2 = LoopDispositions[S];
7958 for (unsigned u = Values2.size(); u > 0; u--) {
7959 if (Values2[u - 1].first == L) {
7960 Values2[u - 1].second = D;
7967 ScalarEvolution::LoopDisposition
7968 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
7969 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
7971 return LoopInvariant;
7975 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
7976 case scAddRecExpr: {
7977 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
7979 // If L is the addrec's loop, it's computable.
7980 if (AR->getLoop() == L)
7981 return LoopComputable;
7983 // Add recurrences are never invariant in the function-body (null loop).
7987 // This recurrence is variant w.r.t. L if L contains AR's loop.
7988 if (L->contains(AR->getLoop()))
7991 // This recurrence is invariant w.r.t. L if AR's loop contains L.
7992 if (AR->getLoop()->contains(L))
7993 return LoopInvariant;
7995 // This recurrence is variant w.r.t. L if any of its operands
7997 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
7999 if (!isLoopInvariant(*I, L))
8002 // Otherwise it's loop-invariant.
8003 return LoopInvariant;
8009 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
8010 bool HasVarying = false;
8011 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
8013 LoopDisposition D = getLoopDisposition(*I, L);
8014 if (D == LoopVariant)
8016 if (D == LoopComputable)
8019 return HasVarying ? LoopComputable : LoopInvariant;
8022 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
8023 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
8024 if (LD == LoopVariant)
8026 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
8027 if (RD == LoopVariant)
8029 return (LD == LoopInvariant && RD == LoopInvariant) ?
8030 LoopInvariant : LoopComputable;
8033 // All non-instruction values are loop invariant. All instructions are loop
8034 // invariant if they are not contained in the specified loop.
8035 // Instructions are never considered invariant in the function body
8036 // (null loop) because they are defined within the "loop".
8037 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
8038 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
8039 return LoopInvariant;
8040 case scCouldNotCompute:
8041 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
8043 llvm_unreachable("Unknown SCEV kind!");
8046 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
8047 return getLoopDisposition(S, L) == LoopInvariant;
8050 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
8051 return getLoopDisposition(S, L) == LoopComputable;
8054 ScalarEvolution::BlockDisposition
8055 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
8056 SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values = BlockDispositions[S];
8057 for (unsigned u = 0; u < Values.size(); u++) {
8058 if (Values[u].first == BB)
8059 return Values[u].second;
8061 Values.push_back(std::make_pair(BB, DoesNotDominateBlock));
8062 BlockDisposition D = computeBlockDisposition(S, BB);
8063 SmallVector<std::pair<const BasicBlock *, BlockDisposition>, 2> &Values2 = BlockDispositions[S];
8064 for (unsigned u = Values2.size(); u > 0; u--) {
8065 if (Values2[u - 1].first == BB) {
8066 Values2[u - 1].second = D;
8073 ScalarEvolution::BlockDisposition
8074 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
8075 switch (static_cast<SCEVTypes>(S->getSCEVType())) {
8077 return ProperlyDominatesBlock;
8081 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
8082 case scAddRecExpr: {
8083 // This uses a "dominates" query instead of "properly dominates" query
8084 // to test for proper dominance too, because the instruction which
8085 // produces the addrec's value is a PHI, and a PHI effectively properly
8086 // dominates its entire containing block.
8087 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
8088 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
8089 return DoesNotDominateBlock;
8091 // FALL THROUGH into SCEVNAryExpr handling.
8096 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
8098 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
8100 BlockDisposition D = getBlockDisposition(*I, BB);
8101 if (D == DoesNotDominateBlock)
8102 return DoesNotDominateBlock;
8103 if (D == DominatesBlock)
8106 return Proper ? ProperlyDominatesBlock : DominatesBlock;
8109 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
8110 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
8111 BlockDisposition LD = getBlockDisposition(LHS, BB);
8112 if (LD == DoesNotDominateBlock)
8113 return DoesNotDominateBlock;
8114 BlockDisposition RD = getBlockDisposition(RHS, BB);
8115 if (RD == DoesNotDominateBlock)
8116 return DoesNotDominateBlock;
8117 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
8118 ProperlyDominatesBlock : DominatesBlock;
8121 if (Instruction *I =
8122 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
8123 if (I->getParent() == BB)
8124 return DominatesBlock;
8125 if (DT->properlyDominates(I->getParent(), BB))
8126 return ProperlyDominatesBlock;
8127 return DoesNotDominateBlock;
8129 return ProperlyDominatesBlock;
8130 case scCouldNotCompute:
8131 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
8133 llvm_unreachable("Unknown SCEV kind!");
8136 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
8137 return getBlockDisposition(S, BB) >= DominatesBlock;
8140 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
8141 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
8145 // Search for a SCEV expression node within an expression tree.
8146 // Implements SCEVTraversal::Visitor.
8151 SCEVSearch(const SCEV *N): Node(N), IsFound(false) {}
8153 bool follow(const SCEV *S) {
8154 IsFound |= (S == Node);
8157 bool isDone() const { return IsFound; }
8161 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
8162 SCEVSearch Search(Op);
8163 visitAll(S, Search);
8164 return Search.IsFound;
8167 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
8168 ValuesAtScopes.erase(S);
8169 LoopDispositions.erase(S);
8170 BlockDispositions.erase(S);
8171 UnsignedRanges.erase(S);
8172 SignedRanges.erase(S);
8174 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
8175 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end(); I != E; ) {
8176 BackedgeTakenInfo &BEInfo = I->second;
8177 if (BEInfo.hasOperand(S, this)) {
8179 BackedgeTakenCounts.erase(I++);
8186 typedef DenseMap<const Loop *, std::string> VerifyMap;
8188 /// replaceSubString - Replaces all occurrences of From in Str with To.
8189 static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
8191 while ((Pos = Str.find(From, Pos)) != std::string::npos) {
8192 Str.replace(Pos, From.size(), To.data(), To.size());
8197 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
8199 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
8200 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) {
8201 getLoopBackedgeTakenCounts(*I, Map, SE); // recurse.
8203 std::string &S = Map[L];
8205 raw_string_ostream OS(S);
8206 SE.getBackedgeTakenCount(L)->print(OS);
8208 // false and 0 are semantically equivalent. This can happen in dead loops.
8209 replaceSubString(OS.str(), "false", "0");
8210 // Remove wrap flags, their use in SCEV is highly fragile.
8211 // FIXME: Remove this when SCEV gets smarter about them.
8212 replaceSubString(OS.str(), "<nw>", "");
8213 replaceSubString(OS.str(), "<nsw>", "");
8214 replaceSubString(OS.str(), "<nuw>", "");
8219 void ScalarEvolution::verifyAnalysis() const {
8223 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
8225 // Gather stringified backedge taken counts for all loops using SCEV's caches.
8226 // FIXME: It would be much better to store actual values instead of strings,
8227 // but SCEV pointers will change if we drop the caches.
8228 VerifyMap BackedgeDumpsOld, BackedgeDumpsNew;
8229 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
8230 getLoopBackedgeTakenCounts(*I, BackedgeDumpsOld, SE);
8232 // Gather stringified backedge taken counts for all loops without using
8235 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
8236 getLoopBackedgeTakenCounts(*I, BackedgeDumpsNew, SE);
8238 // Now compare whether they're the same with and without caches. This allows
8239 // verifying that no pass changed the cache.
8240 assert(BackedgeDumpsOld.size() == BackedgeDumpsNew.size() &&
8241 "New loops suddenly appeared!");
8243 for (VerifyMap::iterator OldI = BackedgeDumpsOld.begin(),
8244 OldE = BackedgeDumpsOld.end(),
8245 NewI = BackedgeDumpsNew.begin();
8246 OldI != OldE; ++OldI, ++NewI) {
8247 assert(OldI->first == NewI->first && "Loop order changed!");
8249 // Compare the stringified SCEVs. We don't care if undef backedgetaken count
8251 // FIXME: We currently ignore SCEV changes from/to CouldNotCompute. This
8252 // means that a pass is buggy or SCEV has to learn a new pattern but is
8253 // usually not harmful.
8254 if (OldI->second != NewI->second &&
8255 OldI->second.find("undef") == std::string::npos &&
8256 NewI->second.find("undef") == std::string::npos &&
8257 OldI->second != "***COULDNOTCOMPUTE***" &&
8258 NewI->second != "***COULDNOTCOMPUTE***") {
8259 dbgs() << "SCEVValidator: SCEV for loop '"
8260 << OldI->first->getHeader()->getName()
8261 << "' changed from '" << OldI->second
8262 << "' to '" << NewI->second << "'!\n";
8267 // TODO: Verify more things.