1 //===- ScalarEvolution.cpp - Scalar Evolution Analysis ----------*- C++ -*-===//
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 #define DEBUG_TYPE "scalar-evolution"
62 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
63 #include "llvm/Constants.h"
64 #include "llvm/DerivedTypes.h"
65 #include "llvm/GlobalVariable.h"
66 #include "llvm/GlobalAlias.h"
67 #include "llvm/Instructions.h"
68 #include "llvm/LLVMContext.h"
69 #include "llvm/Operator.h"
70 #include "llvm/Analysis/ConstantFolding.h"
71 #include "llvm/Analysis/Dominators.h"
72 #include "llvm/Analysis/LoopInfo.h"
73 #include "llvm/Analysis/ValueTracking.h"
74 #include "llvm/Assembly/Writer.h"
75 #include "llvm/Target/TargetData.h"
76 #include "llvm/Support/CommandLine.h"
77 #include "llvm/Support/ConstantRange.h"
78 #include "llvm/Support/Debug.h"
79 #include "llvm/Support/ErrorHandling.h"
80 #include "llvm/Support/GetElementPtrTypeIterator.h"
81 #include "llvm/Support/InstIterator.h"
82 #include "llvm/Support/MathExtras.h"
83 #include "llvm/Support/raw_ostream.h"
84 #include "llvm/ADT/Statistic.h"
85 #include "llvm/ADT/STLExtras.h"
86 #include "llvm/ADT/SmallPtrSet.h"
90 STATISTIC(NumArrayLenItCounts,
91 "Number of trip counts computed with array length");
92 STATISTIC(NumTripCountsComputed,
93 "Number of loops with predictable loop counts");
94 STATISTIC(NumTripCountsNotComputed,
95 "Number of loops without predictable loop counts");
96 STATISTIC(NumBruteForceTripCountsComputed,
97 "Number of loops with trip counts computed by force");
99 static cl::opt<unsigned>
100 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
101 cl::desc("Maximum number of iterations SCEV will "
102 "symbolically execute a constant "
106 static RegisterPass<ScalarEvolution>
107 R("scalar-evolution", "Scalar Evolution Analysis", false, true);
108 char ScalarEvolution::ID = 0;
110 //===----------------------------------------------------------------------===//
111 // SCEV class definitions
112 //===----------------------------------------------------------------------===//
114 //===----------------------------------------------------------------------===//
115 // Implementation of the SCEV class.
120 void SCEV::dump() const {
125 bool SCEV::isZero() const {
126 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
127 return SC->getValue()->isZero();
131 bool SCEV::isOne() const {
132 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
133 return SC->getValue()->isOne();
137 bool SCEV::isAllOnesValue() const {
138 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
139 return SC->getValue()->isAllOnesValue();
143 SCEVCouldNotCompute::SCEVCouldNotCompute() :
144 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
146 bool SCEVCouldNotCompute::isLoopInvariant(const Loop *L) const {
147 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
151 const Type *SCEVCouldNotCompute::getType() const {
152 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
156 bool SCEVCouldNotCompute::hasComputableLoopEvolution(const Loop *L) const {
157 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
161 bool SCEVCouldNotCompute::hasOperand(const SCEV *) const {
162 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
166 void SCEVCouldNotCompute::print(raw_ostream &OS) const {
167 OS << "***COULDNOTCOMPUTE***";
170 bool SCEVCouldNotCompute::classof(const SCEV *S) {
171 return S->getSCEVType() == scCouldNotCompute;
174 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
176 ID.AddInteger(scConstant);
179 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
180 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
181 UniqueSCEVs.InsertNode(S, IP);
185 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
186 return getConstant(ConstantInt::get(getContext(), Val));
190 ScalarEvolution::getConstant(const Type *Ty, uint64_t V, bool isSigned) {
191 const IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
192 return getConstant(ConstantInt::get(ITy, V, isSigned));
195 const Type *SCEVConstant::getType() const { return V->getType(); }
197 void SCEVConstant::print(raw_ostream &OS) const {
198 WriteAsOperand(OS, V, false);
201 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
202 unsigned SCEVTy, const SCEV *op, const Type *ty)
203 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
205 bool SCEVCastExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
206 return Op->dominates(BB, DT);
209 bool SCEVCastExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
210 return Op->properlyDominates(BB, DT);
213 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
214 const SCEV *op, const Type *ty)
215 : SCEVCastExpr(ID, scTruncate, op, ty) {
216 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
217 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
218 "Cannot truncate non-integer value!");
221 void SCEVTruncateExpr::print(raw_ostream &OS) const {
222 OS << "(trunc " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
225 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
226 const SCEV *op, const Type *ty)
227 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
228 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
229 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
230 "Cannot zero extend non-integer value!");
233 void SCEVZeroExtendExpr::print(raw_ostream &OS) const {
234 OS << "(zext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
237 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
238 const SCEV *op, const Type *ty)
239 : SCEVCastExpr(ID, scSignExtend, op, ty) {
240 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
241 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
242 "Cannot sign extend non-integer value!");
245 void SCEVSignExtendExpr::print(raw_ostream &OS) const {
246 OS << "(sext " << *Op->getType() << " " << *Op << " to " << *Ty << ")";
249 void SCEVCommutativeExpr::print(raw_ostream &OS) const {
250 const char *OpStr = getOperationStr();
252 for (op_iterator I = op_begin(), E = op_end(); I != E; ++I) {
260 bool SCEVNAryExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
261 for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
262 if (!getOperand(i)->dominates(BB, DT))
268 bool SCEVNAryExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
269 for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
270 if (!getOperand(i)->properlyDominates(BB, DT))
276 bool SCEVUDivExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
277 return LHS->dominates(BB, DT) && RHS->dominates(BB, DT);
280 bool SCEVUDivExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
281 return LHS->properlyDominates(BB, DT) && RHS->properlyDominates(BB, DT);
284 void SCEVUDivExpr::print(raw_ostream &OS) const {
285 OS << "(" << *LHS << " /u " << *RHS << ")";
288 const Type *SCEVUDivExpr::getType() const {
289 // In most cases the types of LHS and RHS will be the same, but in some
290 // crazy cases one or the other may be a pointer. ScalarEvolution doesn't
291 // depend on the type for correctness, but handling types carefully can
292 // avoid extra casts in the SCEVExpander. The LHS is more likely to be
293 // a pointer type than the RHS, so use the RHS' type here.
294 return RHS->getType();
297 bool SCEVAddRecExpr::isLoopInvariant(const Loop *QueryLoop) const {
298 // Add recurrences are never invariant in the function-body (null loop).
302 // This recurrence is variant w.r.t. QueryLoop if QueryLoop contains L.
303 if (QueryLoop->contains(L))
306 // This recurrence is variant w.r.t. QueryLoop if any of its operands
308 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
309 if (!getOperand(i)->isLoopInvariant(QueryLoop))
312 // Otherwise it's loop-invariant.
317 SCEVAddRecExpr::dominates(BasicBlock *BB, DominatorTree *DT) const {
318 return DT->dominates(L->getHeader(), BB) &&
319 SCEVNAryExpr::dominates(BB, DT);
323 SCEVAddRecExpr::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
324 // This uses a "dominates" query instead of "properly dominates" query because
325 // the instruction which produces the addrec's value is a PHI, and a PHI
326 // effectively properly dominates its entire containing block.
327 return DT->dominates(L->getHeader(), BB) &&
328 SCEVNAryExpr::properlyDominates(BB, DT);
331 void SCEVAddRecExpr::print(raw_ostream &OS) const {
332 OS << "{" << *Operands[0];
333 for (unsigned i = 1, e = NumOperands; i != e; ++i)
334 OS << ",+," << *Operands[i];
336 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
340 bool SCEVUnknown::isLoopInvariant(const Loop *L) const {
341 // All non-instruction values are loop invariant. All instructions are loop
342 // invariant if they are not contained in the specified loop.
343 // Instructions are never considered invariant in the function body
344 // (null loop) because they are defined within the "loop".
345 if (Instruction *I = dyn_cast<Instruction>(V))
346 return L && !L->contains(I);
350 bool SCEVUnknown::dominates(BasicBlock *BB, DominatorTree *DT) const {
351 if (Instruction *I = dyn_cast<Instruction>(getValue()))
352 return DT->dominates(I->getParent(), BB);
356 bool SCEVUnknown::properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
357 if (Instruction *I = dyn_cast<Instruction>(getValue()))
358 return DT->properlyDominates(I->getParent(), BB);
362 const Type *SCEVUnknown::getType() const {
366 bool SCEVUnknown::isSizeOf(const Type *&AllocTy) const {
367 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
368 if (VCE->getOpcode() == Instruction::PtrToInt)
369 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
370 if (CE->getOpcode() == Instruction::GetElementPtr &&
371 CE->getOperand(0)->isNullValue() &&
372 CE->getNumOperands() == 2)
373 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
375 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
383 bool SCEVUnknown::isAlignOf(const Type *&AllocTy) const {
384 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
385 if (VCE->getOpcode() == Instruction::PtrToInt)
386 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
387 if (CE->getOpcode() == Instruction::GetElementPtr &&
388 CE->getOperand(0)->isNullValue()) {
390 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
391 if (const StructType *STy = dyn_cast<StructType>(Ty))
392 if (!STy->isPacked() &&
393 CE->getNumOperands() == 3 &&
394 CE->getOperand(1)->isNullValue()) {
395 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
397 STy->getNumElements() == 2 &&
398 STy->getElementType(0)->isIntegerTy(1)) {
399 AllocTy = STy->getElementType(1);
408 bool SCEVUnknown::isOffsetOf(const Type *&CTy, Constant *&FieldNo) const {
409 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(V))
410 if (VCE->getOpcode() == Instruction::PtrToInt)
411 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
412 if (CE->getOpcode() == Instruction::GetElementPtr &&
413 CE->getNumOperands() == 3 &&
414 CE->getOperand(0)->isNullValue() &&
415 CE->getOperand(1)->isNullValue()) {
417 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
418 // Ignore vector types here so that ScalarEvolutionExpander doesn't
419 // emit getelementptrs that index into vectors.
420 if (Ty->isStructTy() || Ty->isArrayTy()) {
422 FieldNo = CE->getOperand(2);
430 void SCEVUnknown::print(raw_ostream &OS) const {
432 if (isSizeOf(AllocTy)) {
433 OS << "sizeof(" << *AllocTy << ")";
436 if (isAlignOf(AllocTy)) {
437 OS << "alignof(" << *AllocTy << ")";
443 if (isOffsetOf(CTy, FieldNo)) {
444 OS << "offsetof(" << *CTy << ", ";
445 WriteAsOperand(OS, FieldNo, false);
450 // Otherwise just print it normally.
451 WriteAsOperand(OS, V, false);
454 //===----------------------------------------------------------------------===//
456 //===----------------------------------------------------------------------===//
458 static bool CompareTypes(const Type *A, const Type *B) {
459 if (A->getTypeID() != B->getTypeID())
460 return A->getTypeID() < B->getTypeID();
461 if (const IntegerType *AI = dyn_cast<IntegerType>(A)) {
462 const IntegerType *BI = cast<IntegerType>(B);
463 return AI->getBitWidth() < BI->getBitWidth();
465 if (const PointerType *AI = dyn_cast<PointerType>(A)) {
466 const PointerType *BI = cast<PointerType>(B);
467 return CompareTypes(AI->getElementType(), BI->getElementType());
469 if (const ArrayType *AI = dyn_cast<ArrayType>(A)) {
470 const ArrayType *BI = cast<ArrayType>(B);
471 if (AI->getNumElements() != BI->getNumElements())
472 return AI->getNumElements() < BI->getNumElements();
473 return CompareTypes(AI->getElementType(), BI->getElementType());
475 if (const VectorType *AI = dyn_cast<VectorType>(A)) {
476 const VectorType *BI = cast<VectorType>(B);
477 if (AI->getNumElements() != BI->getNumElements())
478 return AI->getNumElements() < BI->getNumElements();
479 return CompareTypes(AI->getElementType(), BI->getElementType());
481 if (const StructType *AI = dyn_cast<StructType>(A)) {
482 const StructType *BI = cast<StructType>(B);
483 if (AI->getNumElements() != BI->getNumElements())
484 return AI->getNumElements() < BI->getNumElements();
485 for (unsigned i = 0, e = AI->getNumElements(); i != e; ++i)
486 if (CompareTypes(AI->getElementType(i), BI->getElementType(i)) ||
487 CompareTypes(BI->getElementType(i), AI->getElementType(i)))
488 return CompareTypes(AI->getElementType(i), BI->getElementType(i));
494 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
495 /// than the complexity of the RHS. This comparator is used to canonicalize
497 class SCEVComplexityCompare {
500 explicit SCEVComplexityCompare(LoopInfo *li) : LI(li) {}
502 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
503 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
507 // Primarily, sort the SCEVs by their getSCEVType().
508 if (LHS->getSCEVType() != RHS->getSCEVType())
509 return LHS->getSCEVType() < RHS->getSCEVType();
511 // Aside from the getSCEVType() ordering, the particular ordering
512 // isn't very important except that it's beneficial to be consistent,
513 // so that (a + b) and (b + a) don't end up as different expressions.
515 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
516 // not as complete as it could be.
517 if (const SCEVUnknown *LU = dyn_cast<SCEVUnknown>(LHS)) {
518 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
520 // Order pointer values after integer values. This helps SCEVExpander
522 if (LU->getType()->isPointerTy() && !RU->getType()->isPointerTy())
524 if (RU->getType()->isPointerTy() && !LU->getType()->isPointerTy())
527 // Compare getValueID values.
528 if (LU->getValue()->getValueID() != RU->getValue()->getValueID())
529 return LU->getValue()->getValueID() < RU->getValue()->getValueID();
531 // Sort arguments by their position.
532 if (const Argument *LA = dyn_cast<Argument>(LU->getValue())) {
533 const Argument *RA = cast<Argument>(RU->getValue());
534 return LA->getArgNo() < RA->getArgNo();
537 // For instructions, compare their loop depth, and their opcode.
538 // This is pretty loose.
539 if (Instruction *LV = dyn_cast<Instruction>(LU->getValue())) {
540 Instruction *RV = cast<Instruction>(RU->getValue());
542 // Compare loop depths.
543 if (LI->getLoopDepth(LV->getParent()) !=
544 LI->getLoopDepth(RV->getParent()))
545 return LI->getLoopDepth(LV->getParent()) <
546 LI->getLoopDepth(RV->getParent());
549 if (LV->getOpcode() != RV->getOpcode())
550 return LV->getOpcode() < RV->getOpcode();
552 // Compare the number of operands.
553 if (LV->getNumOperands() != RV->getNumOperands())
554 return LV->getNumOperands() < RV->getNumOperands();
560 // Compare constant values.
561 if (const SCEVConstant *LC = dyn_cast<SCEVConstant>(LHS)) {
562 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
563 if (LC->getValue()->getBitWidth() != RC->getValue()->getBitWidth())
564 return LC->getValue()->getBitWidth() < RC->getValue()->getBitWidth();
565 return LC->getValue()->getValue().ult(RC->getValue()->getValue());
568 // Compare addrec loop depths.
569 if (const SCEVAddRecExpr *LA = dyn_cast<SCEVAddRecExpr>(LHS)) {
570 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
571 if (LA->getLoop()->getLoopDepth() != RA->getLoop()->getLoopDepth())
572 return LA->getLoop()->getLoopDepth() < RA->getLoop()->getLoopDepth();
575 // Lexicographically compare n-ary expressions.
576 if (const SCEVNAryExpr *LC = dyn_cast<SCEVNAryExpr>(LHS)) {
577 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
578 for (unsigned i = 0, e = LC->getNumOperands(); i != e; ++i) {
579 if (i >= RC->getNumOperands())
581 if (operator()(LC->getOperand(i), RC->getOperand(i)))
583 if (operator()(RC->getOperand(i), LC->getOperand(i)))
586 return LC->getNumOperands() < RC->getNumOperands();
589 // Lexicographically compare udiv expressions.
590 if (const SCEVUDivExpr *LC = dyn_cast<SCEVUDivExpr>(LHS)) {
591 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
592 if (operator()(LC->getLHS(), RC->getLHS()))
594 if (operator()(RC->getLHS(), LC->getLHS()))
596 if (operator()(LC->getRHS(), RC->getRHS()))
598 if (operator()(RC->getRHS(), LC->getRHS()))
603 // Compare cast expressions by operand.
604 if (const SCEVCastExpr *LC = dyn_cast<SCEVCastExpr>(LHS)) {
605 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
606 return operator()(LC->getOperand(), RC->getOperand());
609 llvm_unreachable("Unknown SCEV kind!");
615 /// GroupByComplexity - Given a list of SCEV objects, order them by their
616 /// complexity, and group objects of the same complexity together by value.
617 /// When this routine is finished, we know that any duplicates in the vector are
618 /// consecutive and that complexity is monotonically increasing.
620 /// Note that we go take special precautions to ensure that we get deterministic
621 /// results from this routine. In other words, we don't want the results of
622 /// this to depend on where the addresses of various SCEV objects happened to
625 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
627 if (Ops.size() < 2) return; // Noop
628 if (Ops.size() == 2) {
629 // This is the common case, which also happens to be trivially simple.
631 if (SCEVComplexityCompare(LI)(Ops[1], Ops[0]))
632 std::swap(Ops[0], Ops[1]);
636 // Do the rough sort by complexity.
637 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
639 // Now that we are sorted by complexity, group elements of the same
640 // complexity. Note that this is, at worst, N^2, but the vector is likely to
641 // be extremely short in practice. Note that we take this approach because we
642 // do not want to depend on the addresses of the objects we are grouping.
643 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
644 const SCEV *S = Ops[i];
645 unsigned Complexity = S->getSCEVType();
647 // If there are any objects of the same complexity and same value as this
649 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
650 if (Ops[j] == S) { // Found a duplicate.
651 // Move it to immediately after i'th element.
652 std::swap(Ops[i+1], Ops[j]);
653 ++i; // no need to rescan it.
654 if (i == e-2) return; // Done!
662 //===----------------------------------------------------------------------===//
663 // Simple SCEV method implementations
664 //===----------------------------------------------------------------------===//
666 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
668 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
670 const Type* ResultTy) {
671 // Handle the simplest case efficiently.
673 return SE.getTruncateOrZeroExtend(It, ResultTy);
675 // We are using the following formula for BC(It, K):
677 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
679 // Suppose, W is the bitwidth of the return value. We must be prepared for
680 // overflow. Hence, we must assure that the result of our computation is
681 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
682 // safe in modular arithmetic.
684 // However, this code doesn't use exactly that formula; the formula it uses
685 // is something like the following, where T is the number of factors of 2 in
686 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
689 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
691 // This formula is trivially equivalent to the previous formula. However,
692 // this formula can be implemented much more efficiently. The trick is that
693 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
694 // arithmetic. To do exact division in modular arithmetic, all we have
695 // to do is multiply by the inverse. Therefore, this step can be done at
698 // The next issue is how to safely do the division by 2^T. The way this
699 // is done is by doing the multiplication step at a width of at least W + T
700 // bits. This way, the bottom W+T bits of the product are accurate. Then,
701 // when we perform the division by 2^T (which is equivalent to a right shift
702 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
703 // truncated out after the division by 2^T.
705 // In comparison to just directly using the first formula, this technique
706 // is much more efficient; using the first formula requires W * K bits,
707 // but this formula less than W + K bits. Also, the first formula requires
708 // a division step, whereas this formula only requires multiplies and shifts.
710 // It doesn't matter whether the subtraction step is done in the calculation
711 // width or the input iteration count's width; if the subtraction overflows,
712 // the result must be zero anyway. We prefer here to do it in the width of
713 // the induction variable because it helps a lot for certain cases; CodeGen
714 // isn't smart enough to ignore the overflow, which leads to much less
715 // efficient code if the width of the subtraction is wider than the native
718 // (It's possible to not widen at all by pulling out factors of 2 before
719 // the multiplication; for example, K=2 can be calculated as
720 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
721 // extra arithmetic, so it's not an obvious win, and it gets
722 // much more complicated for K > 3.)
724 // Protection from insane SCEVs; this bound is conservative,
725 // but it probably doesn't matter.
727 return SE.getCouldNotCompute();
729 unsigned W = SE.getTypeSizeInBits(ResultTy);
731 // Calculate K! / 2^T and T; we divide out the factors of two before
732 // multiplying for calculating K! / 2^T to avoid overflow.
733 // Other overflow doesn't matter because we only care about the bottom
734 // W bits of the result.
735 APInt OddFactorial(W, 1);
737 for (unsigned i = 3; i <= K; ++i) {
739 unsigned TwoFactors = Mult.countTrailingZeros();
741 Mult = Mult.lshr(TwoFactors);
742 OddFactorial *= Mult;
745 // We need at least W + T bits for the multiplication step
746 unsigned CalculationBits = W + T;
748 // Calculate 2^T, at width T+W.
749 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
751 // Calculate the multiplicative inverse of K! / 2^T;
752 // this multiplication factor will perform the exact division by
754 APInt Mod = APInt::getSignedMinValue(W+1);
755 APInt MultiplyFactor = OddFactorial.zext(W+1);
756 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
757 MultiplyFactor = MultiplyFactor.trunc(W);
759 // Calculate the product, at width T+W
760 const IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
762 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
763 for (unsigned i = 1; i != K; ++i) {
764 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
765 Dividend = SE.getMulExpr(Dividend,
766 SE.getTruncateOrZeroExtend(S, CalculationTy));
770 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
772 // Truncate the result, and divide by K! / 2^T.
774 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
775 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
778 /// evaluateAtIteration - Return the value of this chain of recurrences at
779 /// the specified iteration number. We can evaluate this recurrence by
780 /// multiplying each element in the chain by the binomial coefficient
781 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
783 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
785 /// where BC(It, k) stands for binomial coefficient.
787 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
788 ScalarEvolution &SE) const {
789 const SCEV *Result = getStart();
790 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
791 // The computation is correct in the face of overflow provided that the
792 // multiplication is performed _after_ the evaluation of the binomial
794 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
795 if (isa<SCEVCouldNotCompute>(Coeff))
798 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
803 //===----------------------------------------------------------------------===//
804 // SCEV Expression folder implementations
805 //===----------------------------------------------------------------------===//
807 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
809 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
810 "This is not a truncating conversion!");
811 assert(isSCEVable(Ty) &&
812 "This is not a conversion to a SCEVable type!");
813 Ty = getEffectiveSCEVType(Ty);
816 ID.AddInteger(scTruncate);
820 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
822 // Fold if the operand is constant.
823 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
825 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
826 getEffectiveSCEVType(Ty))));
828 // trunc(trunc(x)) --> trunc(x)
829 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
830 return getTruncateExpr(ST->getOperand(), Ty);
832 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
833 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
834 return getTruncateOrSignExtend(SS->getOperand(), Ty);
836 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
837 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
838 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
840 // If the input value is a chrec scev, truncate the chrec's operands.
841 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
842 SmallVector<const SCEV *, 4> Operands;
843 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
844 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
845 return getAddRecExpr(Operands, AddRec->getLoop());
848 // The cast wasn't folded; create an explicit cast node. We can reuse
849 // the existing insert position since if we get here, we won't have
850 // made any changes which would invalidate it.
851 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
853 UniqueSCEVs.InsertNode(S, IP);
857 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
859 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
860 "This is not an extending conversion!");
861 assert(isSCEVable(Ty) &&
862 "This is not a conversion to a SCEVable type!");
863 Ty = getEffectiveSCEVType(Ty);
865 // Fold if the operand is constant.
866 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
868 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
869 getEffectiveSCEVType(Ty))));
871 // zext(zext(x)) --> zext(x)
872 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
873 return getZeroExtendExpr(SZ->getOperand(), Ty);
875 // Before doing any expensive analysis, check to see if we've already
876 // computed a SCEV for this Op and Ty.
878 ID.AddInteger(scZeroExtend);
882 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
884 // If the input value is a chrec scev, and we can prove that the value
885 // did not overflow the old, smaller, value, we can zero extend all of the
886 // operands (often constants). This allows analysis of something like
887 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
888 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
889 if (AR->isAffine()) {
890 const SCEV *Start = AR->getStart();
891 const SCEV *Step = AR->getStepRecurrence(*this);
892 unsigned BitWidth = getTypeSizeInBits(AR->getType());
893 const Loop *L = AR->getLoop();
895 // If we have special knowledge that this addrec won't overflow,
896 // we don't need to do any further analysis.
897 if (AR->hasNoUnsignedWrap())
898 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
899 getZeroExtendExpr(Step, Ty),
902 // Check whether the backedge-taken count is SCEVCouldNotCompute.
903 // Note that this serves two purposes: It filters out loops that are
904 // simply not analyzable, and it covers the case where this code is
905 // being called from within backedge-taken count analysis, such that
906 // attempting to ask for the backedge-taken count would likely result
907 // in infinite recursion. In the later case, the analysis code will
908 // cope with a conservative value, and it will take care to purge
909 // that value once it has finished.
910 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
911 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
912 // Manually compute the final value for AR, checking for
915 // Check whether the backedge-taken count can be losslessly casted to
916 // the addrec's type. The count is always unsigned.
917 const SCEV *CastedMaxBECount =
918 getTruncateOrZeroExtend(MaxBECount, Start->getType());
919 const SCEV *RecastedMaxBECount =
920 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
921 if (MaxBECount == RecastedMaxBECount) {
922 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
923 // Check whether Start+Step*MaxBECount has no unsigned overflow.
924 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
925 const SCEV *Add = getAddExpr(Start, ZMul);
926 const SCEV *OperandExtendedAdd =
927 getAddExpr(getZeroExtendExpr(Start, WideTy),
928 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
929 getZeroExtendExpr(Step, WideTy)));
930 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
931 // Return the expression with the addrec on the outside.
932 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
933 getZeroExtendExpr(Step, Ty),
936 // Similar to above, only this time treat the step value as signed.
937 // This covers loops that count down.
938 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
939 Add = getAddExpr(Start, SMul);
941 getAddExpr(getZeroExtendExpr(Start, WideTy),
942 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
943 getSignExtendExpr(Step, WideTy)));
944 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
945 // Return the expression with the addrec on the outside.
946 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
947 getSignExtendExpr(Step, Ty),
951 // If the backedge is guarded by a comparison with the pre-inc value
952 // the addrec is safe. Also, if the entry is guarded by a comparison
953 // with the start value and the backedge is guarded by a comparison
954 // with the post-inc value, the addrec is safe.
955 if (isKnownPositive(Step)) {
956 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
957 getUnsignedRange(Step).getUnsignedMax());
958 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
959 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
960 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
961 AR->getPostIncExpr(*this), N)))
962 // Return the expression with the addrec on the outside.
963 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
964 getZeroExtendExpr(Step, Ty),
966 } else if (isKnownNegative(Step)) {
967 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
968 getSignedRange(Step).getSignedMin());
969 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
970 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
971 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
972 AR->getPostIncExpr(*this), N)))
973 // Return the expression with the addrec on the outside.
974 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
975 getSignExtendExpr(Step, Ty),
981 // The cast wasn't folded; create an explicit cast node.
982 // Recompute the insert position, as it may have been invalidated.
983 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
984 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
986 UniqueSCEVs.InsertNode(S, IP);
990 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
992 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
993 "This is not an extending conversion!");
994 assert(isSCEVable(Ty) &&
995 "This is not a conversion to a SCEVable type!");
996 Ty = getEffectiveSCEVType(Ty);
998 // Fold if the operand is constant.
999 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1001 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1002 getEffectiveSCEVType(Ty))));
1004 // sext(sext(x)) --> sext(x)
1005 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1006 return getSignExtendExpr(SS->getOperand(), Ty);
1008 // Before doing any expensive analysis, check to see if we've already
1009 // computed a SCEV for this Op and Ty.
1010 FoldingSetNodeID ID;
1011 ID.AddInteger(scSignExtend);
1015 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1017 // If the input value is a chrec scev, and we can prove that the value
1018 // did not overflow the old, smaller, value, we can sign extend all of the
1019 // operands (often constants). This allows analysis of something like
1020 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1021 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1022 if (AR->isAffine()) {
1023 const SCEV *Start = AR->getStart();
1024 const SCEV *Step = AR->getStepRecurrence(*this);
1025 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1026 const Loop *L = AR->getLoop();
1028 // If we have special knowledge that this addrec won't overflow,
1029 // we don't need to do any further analysis.
1030 if (AR->hasNoSignedWrap())
1031 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1032 getSignExtendExpr(Step, Ty),
1035 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1036 // Note that this serves two purposes: It filters out loops that are
1037 // simply not analyzable, and it covers the case where this code is
1038 // being called from within backedge-taken count analysis, such that
1039 // attempting to ask for the backedge-taken count would likely result
1040 // in infinite recursion. In the later case, the analysis code will
1041 // cope with a conservative value, and it will take care to purge
1042 // that value once it has finished.
1043 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1044 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1045 // Manually compute the final value for AR, checking for
1048 // Check whether the backedge-taken count can be losslessly casted to
1049 // the addrec's type. The count is always unsigned.
1050 const SCEV *CastedMaxBECount =
1051 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1052 const SCEV *RecastedMaxBECount =
1053 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1054 if (MaxBECount == RecastedMaxBECount) {
1055 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1056 // Check whether Start+Step*MaxBECount has no signed overflow.
1057 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1058 const SCEV *Add = getAddExpr(Start, SMul);
1059 const SCEV *OperandExtendedAdd =
1060 getAddExpr(getSignExtendExpr(Start, WideTy),
1061 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1062 getSignExtendExpr(Step, WideTy)));
1063 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1064 // Return the expression with the addrec on the outside.
1065 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1066 getSignExtendExpr(Step, Ty),
1069 // Similar to above, only this time treat the step value as unsigned.
1070 // This covers loops that count up with an unsigned step.
1071 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1072 Add = getAddExpr(Start, UMul);
1073 OperandExtendedAdd =
1074 getAddExpr(getSignExtendExpr(Start, WideTy),
1075 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1076 getZeroExtendExpr(Step, WideTy)));
1077 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1078 // Return the expression with the addrec on the outside.
1079 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1080 getZeroExtendExpr(Step, Ty),
1084 // If the backedge is guarded by a comparison with the pre-inc value
1085 // the addrec is safe. Also, if the entry is guarded by a comparison
1086 // with the start value and the backedge is guarded by a comparison
1087 // with the post-inc value, the addrec is safe.
1088 if (isKnownPositive(Step)) {
1089 const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
1090 getSignedRange(Step).getSignedMax());
1091 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
1092 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
1093 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
1094 AR->getPostIncExpr(*this), N)))
1095 // Return the expression with the addrec on the outside.
1096 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1097 getSignExtendExpr(Step, Ty),
1099 } else if (isKnownNegative(Step)) {
1100 const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
1101 getSignedRange(Step).getSignedMin());
1102 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
1103 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
1104 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
1105 AR->getPostIncExpr(*this), N)))
1106 // Return the expression with the addrec on the outside.
1107 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1108 getSignExtendExpr(Step, Ty),
1114 // The cast wasn't folded; create an explicit cast node.
1115 // Recompute the insert position, as it may have been invalidated.
1116 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1117 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1119 UniqueSCEVs.InsertNode(S, IP);
1123 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1124 /// unspecified bits out to the given type.
1126 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1128 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1129 "This is not an extending conversion!");
1130 assert(isSCEVable(Ty) &&
1131 "This is not a conversion to a SCEVable type!");
1132 Ty = getEffectiveSCEVType(Ty);
1134 // Sign-extend negative constants.
1135 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1136 if (SC->getValue()->getValue().isNegative())
1137 return getSignExtendExpr(Op, Ty);
1139 // Peel off a truncate cast.
1140 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1141 const SCEV *NewOp = T->getOperand();
1142 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1143 return getAnyExtendExpr(NewOp, Ty);
1144 return getTruncateOrNoop(NewOp, Ty);
1147 // Next try a zext cast. If the cast is folded, use it.
1148 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1149 if (!isa<SCEVZeroExtendExpr>(ZExt))
1152 // Next try a sext cast. If the cast is folded, use it.
1153 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1154 if (!isa<SCEVSignExtendExpr>(SExt))
1157 // Force the cast to be folded into the operands of an addrec.
1158 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1159 SmallVector<const SCEV *, 4> Ops;
1160 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1162 Ops.push_back(getAnyExtendExpr(*I, Ty));
1163 return getAddRecExpr(Ops, AR->getLoop());
1166 // If the expression is obviously signed, use the sext cast value.
1167 if (isa<SCEVSMaxExpr>(Op))
1170 // Absent any other information, use the zext cast value.
1174 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1175 /// a list of operands to be added under the given scale, update the given
1176 /// map. This is a helper function for getAddRecExpr. As an example of
1177 /// what it does, given a sequence of operands that would form an add
1178 /// expression like this:
1180 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1182 /// where A and B are constants, update the map with these values:
1184 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1186 /// and add 13 + A*B*29 to AccumulatedConstant.
1187 /// This will allow getAddRecExpr to produce this:
1189 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1191 /// This form often exposes folding opportunities that are hidden in
1192 /// the original operand list.
1194 /// Return true iff it appears that any interesting folding opportunities
1195 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1196 /// the common case where no interesting opportunities are present, and
1197 /// is also used as a check to avoid infinite recursion.
1200 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1201 SmallVector<const SCEV *, 8> &NewOps,
1202 APInt &AccumulatedConstant,
1203 const SCEV *const *Ops, size_t NumOperands,
1205 ScalarEvolution &SE) {
1206 bool Interesting = false;
1208 // Iterate over the add operands. They are sorted, with constants first.
1210 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1212 // Pull a buried constant out to the outside.
1213 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1215 AccumulatedConstant += Scale * C->getValue()->getValue();
1218 // Next comes everything else. We're especially interested in multiplies
1219 // here, but they're in the middle, so just visit the rest with one loop.
1220 for (; i != NumOperands; ++i) {
1221 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1222 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1224 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1225 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1226 // A multiplication of a constant with another add; recurse.
1227 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1229 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1230 Add->op_begin(), Add->getNumOperands(),
1233 // A multiplication of a constant with some other value. Update
1235 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1236 const SCEV *Key = SE.getMulExpr(MulOps);
1237 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1238 M.insert(std::make_pair(Key, NewScale));
1240 NewOps.push_back(Pair.first->first);
1242 Pair.first->second += NewScale;
1243 // The map already had an entry for this value, which may indicate
1244 // a folding opportunity.
1249 // An ordinary operand. Update the map.
1250 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1251 M.insert(std::make_pair(Ops[i], Scale));
1253 NewOps.push_back(Pair.first->first);
1255 Pair.first->second += Scale;
1256 // The map already had an entry for this value, which may indicate
1257 // a folding opportunity.
1267 struct APIntCompare {
1268 bool operator()(const APInt &LHS, const APInt &RHS) const {
1269 return LHS.ult(RHS);
1274 /// getAddExpr - Get a canonical add expression, or something simpler if
1276 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1277 bool HasNUW, bool HasNSW) {
1278 assert(!Ops.empty() && "Cannot get empty add!");
1279 if (Ops.size() == 1) return Ops[0];
1281 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1282 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1283 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1284 "SCEVAddExpr operand types don't match!");
1287 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1288 if (!HasNUW && HasNSW) {
1290 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1291 if (!isKnownNonNegative(Ops[i])) {
1295 if (All) HasNUW = true;
1298 // Sort by complexity, this groups all similar expression types together.
1299 GroupByComplexity(Ops, LI);
1301 // If there are any constants, fold them together.
1303 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1305 assert(Idx < Ops.size());
1306 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1307 // We found two constants, fold them together!
1308 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1309 RHSC->getValue()->getValue());
1310 if (Ops.size() == 2) return Ops[0];
1311 Ops.erase(Ops.begin()+1); // Erase the folded element
1312 LHSC = cast<SCEVConstant>(Ops[0]);
1315 // If we are left with a constant zero being added, strip it off.
1316 if (LHSC->getValue()->isZero()) {
1317 Ops.erase(Ops.begin());
1321 if (Ops.size() == 1) return Ops[0];
1324 // Okay, check to see if the same value occurs in the operand list twice. If
1325 // so, merge them together into an multiply expression. Since we sorted the
1326 // list, these values are required to be adjacent.
1327 const Type *Ty = Ops[0]->getType();
1328 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
1329 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1330 // Found a match, merge the two values into a multiply, and add any
1331 // remaining values to the result.
1332 const SCEV *Two = getConstant(Ty, 2);
1333 const SCEV *Mul = getMulExpr(Ops[i], Two);
1334 if (Ops.size() == 2)
1336 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1338 return getAddExpr(Ops, HasNUW, HasNSW);
1341 // Check for truncates. If all the operands are truncated from the same
1342 // type, see if factoring out the truncate would permit the result to be
1343 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1344 // if the contents of the resulting outer trunc fold to something simple.
1345 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1346 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1347 const Type *DstType = Trunc->getType();
1348 const Type *SrcType = Trunc->getOperand()->getType();
1349 SmallVector<const SCEV *, 8> LargeOps;
1351 // Check all the operands to see if they can be represented in the
1352 // source type of the truncate.
1353 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1354 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1355 if (T->getOperand()->getType() != SrcType) {
1359 LargeOps.push_back(T->getOperand());
1360 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1361 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1362 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1363 SmallVector<const SCEV *, 8> LargeMulOps;
1364 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1365 if (const SCEVTruncateExpr *T =
1366 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1367 if (T->getOperand()->getType() != SrcType) {
1371 LargeMulOps.push_back(T->getOperand());
1372 } else if (const SCEVConstant *C =
1373 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1374 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1381 LargeOps.push_back(getMulExpr(LargeMulOps));
1388 // Evaluate the expression in the larger type.
1389 const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
1390 // If it folds to something simple, use it. Otherwise, don't.
1391 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1392 return getTruncateExpr(Fold, DstType);
1396 // Skip past any other cast SCEVs.
1397 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1400 // If there are add operands they would be next.
1401 if (Idx < Ops.size()) {
1402 bool DeletedAdd = false;
1403 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1404 // If we have an add, expand the add operands onto the end of the operands
1406 Ops.erase(Ops.begin()+Idx);
1407 Ops.append(Add->op_begin(), Add->op_end());
1411 // If we deleted at least one add, we added operands to the end of the list,
1412 // and they are not necessarily sorted. Recurse to resort and resimplify
1413 // any operands we just acquired.
1415 return getAddExpr(Ops);
1418 // Skip over the add expression until we get to a multiply.
1419 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1422 // Check to see if there are any folding opportunities present with
1423 // operands multiplied by constant values.
1424 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1425 uint64_t BitWidth = getTypeSizeInBits(Ty);
1426 DenseMap<const SCEV *, APInt> M;
1427 SmallVector<const SCEV *, 8> NewOps;
1428 APInt AccumulatedConstant(BitWidth, 0);
1429 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1430 Ops.data(), Ops.size(),
1431 APInt(BitWidth, 1), *this)) {
1432 // Some interesting folding opportunity is present, so its worthwhile to
1433 // re-generate the operands list. Group the operands by constant scale,
1434 // to avoid multiplying by the same constant scale multiple times.
1435 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1436 for (SmallVector<const SCEV *, 8>::iterator I = NewOps.begin(),
1437 E = NewOps.end(); I != E; ++I)
1438 MulOpLists[M.find(*I)->second].push_back(*I);
1439 // Re-generate the operands list.
1441 if (AccumulatedConstant != 0)
1442 Ops.push_back(getConstant(AccumulatedConstant));
1443 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1444 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1446 Ops.push_back(getMulExpr(getConstant(I->first),
1447 getAddExpr(I->second)));
1449 return getConstant(Ty, 0);
1450 if (Ops.size() == 1)
1452 return getAddExpr(Ops);
1456 // If we are adding something to a multiply expression, make sure the
1457 // something is not already an operand of the multiply. If so, merge it into
1459 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1460 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1461 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1462 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1463 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1464 if (MulOpSCEV == Ops[AddOp] && !isa<SCEVConstant>(Ops[AddOp])) {
1465 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1466 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1467 if (Mul->getNumOperands() != 2) {
1468 // If the multiply has more than two operands, we must get the
1470 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(), Mul->op_end());
1471 MulOps.erase(MulOps.begin()+MulOp);
1472 InnerMul = getMulExpr(MulOps);
1474 const SCEV *One = getConstant(Ty, 1);
1475 const SCEV *AddOne = getAddExpr(InnerMul, One);
1476 const SCEV *OuterMul = getMulExpr(AddOne, Ops[AddOp]);
1477 if (Ops.size() == 2) return OuterMul;
1479 Ops.erase(Ops.begin()+AddOp);
1480 Ops.erase(Ops.begin()+Idx-1);
1482 Ops.erase(Ops.begin()+Idx);
1483 Ops.erase(Ops.begin()+AddOp-1);
1485 Ops.push_back(OuterMul);
1486 return getAddExpr(Ops);
1489 // Check this multiply against other multiplies being added together.
1490 for (unsigned OtherMulIdx = Idx+1;
1491 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1493 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1494 // If MulOp occurs in OtherMul, we can fold the two multiplies
1496 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1497 OMulOp != e; ++OMulOp)
1498 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1499 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1500 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1501 if (Mul->getNumOperands() != 2) {
1502 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1504 MulOps.erase(MulOps.begin()+MulOp);
1505 InnerMul1 = getMulExpr(MulOps);
1507 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1508 if (OtherMul->getNumOperands() != 2) {
1509 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1510 OtherMul->op_end());
1511 MulOps.erase(MulOps.begin()+OMulOp);
1512 InnerMul2 = getMulExpr(MulOps);
1514 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1515 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1516 if (Ops.size() == 2) return OuterMul;
1517 Ops.erase(Ops.begin()+Idx);
1518 Ops.erase(Ops.begin()+OtherMulIdx-1);
1519 Ops.push_back(OuterMul);
1520 return getAddExpr(Ops);
1526 // If there are any add recurrences in the operands list, see if any other
1527 // added values are loop invariant. If so, we can fold them into the
1529 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1532 // Scan over all recurrences, trying to fold loop invariants into them.
1533 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1534 // Scan all of the other operands to this add and add them to the vector if
1535 // they are loop invariant w.r.t. the recurrence.
1536 SmallVector<const SCEV *, 8> LIOps;
1537 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1538 const Loop *AddRecLoop = AddRec->getLoop();
1539 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1540 if (Ops[i]->isLoopInvariant(AddRecLoop)) {
1541 LIOps.push_back(Ops[i]);
1542 Ops.erase(Ops.begin()+i);
1546 // If we found some loop invariants, fold them into the recurrence.
1547 if (!LIOps.empty()) {
1548 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1549 LIOps.push_back(AddRec->getStart());
1551 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1553 AddRecOps[0] = getAddExpr(LIOps);
1555 // It's tempting to propagate NUW/NSW flags here, but nuw/nsw addition
1556 // is not associative so this isn't necessarily safe.
1557 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop);
1559 // If all of the other operands were loop invariant, we are done.
1560 if (Ops.size() == 1) return NewRec;
1562 // Otherwise, add the folded AddRec by the non-liv parts.
1563 for (unsigned i = 0;; ++i)
1564 if (Ops[i] == AddRec) {
1568 return getAddExpr(Ops);
1571 // Okay, if there weren't any loop invariants to be folded, check to see if
1572 // there are multiple AddRec's with the same loop induction variable being
1573 // added together. If so, we can fold them.
1574 for (unsigned OtherIdx = Idx+1;
1575 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
1576 if (OtherIdx != Idx) {
1577 const SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
1578 if (AddRecLoop == OtherAddRec->getLoop()) {
1579 // Other + {A,+,B} + {C,+,D} --> Other + {A+C,+,B+D}
1580 SmallVector<const SCEV *, 4> NewOps(AddRec->op_begin(),
1582 for (unsigned i = 0, e = OtherAddRec->getNumOperands(); i != e; ++i) {
1583 if (i >= NewOps.size()) {
1584 NewOps.append(OtherAddRec->op_begin()+i,
1585 OtherAddRec->op_end());
1588 NewOps[i] = getAddExpr(NewOps[i], OtherAddRec->getOperand(i));
1590 const SCEV *NewAddRec = getAddRecExpr(NewOps, AddRecLoop);
1592 if (Ops.size() == 2) return NewAddRec;
1594 Ops.erase(Ops.begin()+Idx);
1595 Ops.erase(Ops.begin()+OtherIdx-1);
1596 Ops.push_back(NewAddRec);
1597 return getAddExpr(Ops);
1601 // Otherwise couldn't fold anything into this recurrence. Move onto the
1605 // Okay, it looks like we really DO need an add expr. Check to see if we
1606 // already have one, otherwise create a new one.
1607 FoldingSetNodeID ID;
1608 ID.AddInteger(scAddExpr);
1609 ID.AddInteger(Ops.size());
1610 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1611 ID.AddPointer(Ops[i]);
1614 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1616 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1617 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1618 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1620 UniqueSCEVs.InsertNode(S, IP);
1622 if (HasNUW) S->setHasNoUnsignedWrap(true);
1623 if (HasNSW) S->setHasNoSignedWrap(true);
1627 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1629 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1630 bool HasNUW, bool HasNSW) {
1631 assert(!Ops.empty() && "Cannot get empty mul!");
1632 if (Ops.size() == 1) return Ops[0];
1634 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1635 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
1636 getEffectiveSCEVType(Ops[0]->getType()) &&
1637 "SCEVMulExpr operand types don't match!");
1640 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1641 if (!HasNUW && HasNSW) {
1643 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1644 if (!isKnownNonNegative(Ops[i])) {
1648 if (All) HasNUW = true;
1651 // Sort by complexity, this groups all similar expression types together.
1652 GroupByComplexity(Ops, LI);
1654 // If there are any constants, fold them together.
1656 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1658 // C1*(C2+V) -> C1*C2 + C1*V
1659 if (Ops.size() == 2)
1660 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1661 if (Add->getNumOperands() == 2 &&
1662 isa<SCEVConstant>(Add->getOperand(0)))
1663 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1664 getMulExpr(LHSC, Add->getOperand(1)));
1667 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1668 // We found two constants, fold them together!
1669 ConstantInt *Fold = ConstantInt::get(getContext(),
1670 LHSC->getValue()->getValue() *
1671 RHSC->getValue()->getValue());
1672 Ops[0] = getConstant(Fold);
1673 Ops.erase(Ops.begin()+1); // Erase the folded element
1674 if (Ops.size() == 1) return Ops[0];
1675 LHSC = cast<SCEVConstant>(Ops[0]);
1678 // If we are left with a constant one being multiplied, strip it off.
1679 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1680 Ops.erase(Ops.begin());
1682 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1683 // If we have a multiply of zero, it will always be zero.
1685 } else if (Ops[0]->isAllOnesValue()) {
1686 // If we have a mul by -1 of an add, try distributing the -1 among the
1688 if (Ops.size() == 2)
1689 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1690 SmallVector<const SCEV *, 4> NewOps;
1691 bool AnyFolded = false;
1692 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1694 const SCEV *Mul = getMulExpr(Ops[0], *I);
1695 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1696 NewOps.push_back(Mul);
1699 return getAddExpr(NewOps);
1703 if (Ops.size() == 1)
1707 // Skip over the add expression until we get to a multiply.
1708 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1711 // If there are mul operands inline them all into this expression.
1712 if (Idx < Ops.size()) {
1713 bool DeletedMul = false;
1714 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1715 // If we have an mul, expand the mul operands onto the end of the operands
1717 Ops.erase(Ops.begin()+Idx);
1718 Ops.append(Mul->op_begin(), Mul->op_end());
1722 // If we deleted at least one mul, we added operands to the end of the list,
1723 // and they are not necessarily sorted. Recurse to resort and resimplify
1724 // any operands we just acquired.
1726 return getMulExpr(Ops);
1729 // If there are any add recurrences in the operands list, see if any other
1730 // added values are loop invariant. If so, we can fold them into the
1732 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1735 // Scan over all recurrences, trying to fold loop invariants into them.
1736 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1737 // Scan all of the other operands to this mul and add them to the vector if
1738 // they are loop invariant w.r.t. the recurrence.
1739 SmallVector<const SCEV *, 8> LIOps;
1740 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1741 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1742 if (Ops[i]->isLoopInvariant(AddRec->getLoop())) {
1743 LIOps.push_back(Ops[i]);
1744 Ops.erase(Ops.begin()+i);
1748 // If we found some loop invariants, fold them into the recurrence.
1749 if (!LIOps.empty()) {
1750 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1751 SmallVector<const SCEV *, 4> NewOps;
1752 NewOps.reserve(AddRec->getNumOperands());
1753 const SCEV *Scale = getMulExpr(LIOps);
1754 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1755 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1757 // It's tempting to propagate the NSW flag here, but nsw multiplication
1758 // is not associative so this isn't necessarily safe.
1759 const SCEV *NewRec = getAddRecExpr(NewOps, AddRec->getLoop(),
1760 HasNUW && AddRec->hasNoUnsignedWrap(),
1763 // If all of the other operands were loop invariant, we are done.
1764 if (Ops.size() == 1) return NewRec;
1766 // Otherwise, multiply the folded AddRec by the non-liv parts.
1767 for (unsigned i = 0;; ++i)
1768 if (Ops[i] == AddRec) {
1772 return getMulExpr(Ops);
1775 // Okay, if there weren't any loop invariants to be folded, check to see if
1776 // there are multiple AddRec's with the same loop induction variable being
1777 // multiplied together. If so, we can fold them.
1778 for (unsigned OtherIdx = Idx+1;
1779 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);++OtherIdx)
1780 if (OtherIdx != Idx) {
1781 const SCEVAddRecExpr *OtherAddRec = cast<SCEVAddRecExpr>(Ops[OtherIdx]);
1782 if (AddRec->getLoop() == OtherAddRec->getLoop()) {
1783 // F * G --> {A,+,B} * {C,+,D} --> {A*C,+,F*D + G*B + B*D}
1784 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1785 const SCEV *NewStart = getMulExpr(F->getStart(),
1787 const SCEV *B = F->getStepRecurrence(*this);
1788 const SCEV *D = G->getStepRecurrence(*this);
1789 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1792 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1794 if (Ops.size() == 2) return NewAddRec;
1796 Ops.erase(Ops.begin()+Idx);
1797 Ops.erase(Ops.begin()+OtherIdx-1);
1798 Ops.push_back(NewAddRec);
1799 return getMulExpr(Ops);
1803 // Otherwise couldn't fold anything into this recurrence. Move onto the
1807 // Okay, it looks like we really DO need an mul expr. Check to see if we
1808 // already have one, otherwise create a new one.
1809 FoldingSetNodeID ID;
1810 ID.AddInteger(scMulExpr);
1811 ID.AddInteger(Ops.size());
1812 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1813 ID.AddPointer(Ops[i]);
1816 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1818 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1819 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1820 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
1822 UniqueSCEVs.InsertNode(S, IP);
1824 if (HasNUW) S->setHasNoUnsignedWrap(true);
1825 if (HasNSW) S->setHasNoSignedWrap(true);
1829 /// getUDivExpr - Get a canonical unsigned division expression, or something
1830 /// simpler if possible.
1831 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
1833 assert(getEffectiveSCEVType(LHS->getType()) ==
1834 getEffectiveSCEVType(RHS->getType()) &&
1835 "SCEVUDivExpr operand types don't match!");
1837 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
1838 if (RHSC->getValue()->equalsInt(1))
1839 return LHS; // X udiv 1 --> x
1840 // If the denominator is zero, the result of the udiv is undefined. Don't
1841 // try to analyze it, because the resolution chosen here may differ from
1842 // the resolution chosen in other parts of the compiler.
1843 if (!RHSC->getValue()->isZero()) {
1844 // Determine if the division can be folded into the operands of
1846 // TODO: Generalize this to non-constants by using known-bits information.
1847 const Type *Ty = LHS->getType();
1848 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
1849 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ;
1850 // For non-power-of-two values, effectively round the value up to the
1851 // nearest power of two.
1852 if (!RHSC->getValue()->getValue().isPowerOf2())
1854 const IntegerType *ExtTy =
1855 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
1856 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
1857 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
1858 if (const SCEVConstant *Step =
1859 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
1860 if (!Step->getValue()->getValue()
1861 .urem(RHSC->getValue()->getValue()) &&
1862 getZeroExtendExpr(AR, ExtTy) ==
1863 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
1864 getZeroExtendExpr(Step, ExtTy),
1866 SmallVector<const SCEV *, 4> Operands;
1867 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
1868 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
1869 return getAddRecExpr(Operands, AR->getLoop());
1871 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
1872 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
1873 SmallVector<const SCEV *, 4> Operands;
1874 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
1875 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
1876 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
1877 // Find an operand that's safely divisible.
1878 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
1879 const SCEV *Op = M->getOperand(i);
1880 const SCEV *Div = getUDivExpr(Op, RHSC);
1881 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
1882 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
1885 return getMulExpr(Operands);
1889 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
1890 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
1891 SmallVector<const SCEV *, 4> Operands;
1892 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
1893 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
1894 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
1896 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
1897 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
1898 if (isa<SCEVUDivExpr>(Op) ||
1899 getMulExpr(Op, RHS) != A->getOperand(i))
1901 Operands.push_back(Op);
1903 if (Operands.size() == A->getNumOperands())
1904 return getAddExpr(Operands);
1908 // Fold if both operands are constant.
1909 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
1910 Constant *LHSCV = LHSC->getValue();
1911 Constant *RHSCV = RHSC->getValue();
1912 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
1918 FoldingSetNodeID ID;
1919 ID.AddInteger(scUDivExpr);
1923 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1924 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
1926 UniqueSCEVs.InsertNode(S, IP);
1931 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
1932 /// Simplify the expression as much as possible.
1933 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
1934 const SCEV *Step, const Loop *L,
1935 bool HasNUW, bool HasNSW) {
1936 SmallVector<const SCEV *, 4> Operands;
1937 Operands.push_back(Start);
1938 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
1939 if (StepChrec->getLoop() == L) {
1940 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
1941 return getAddRecExpr(Operands, L);
1944 Operands.push_back(Step);
1945 return getAddRecExpr(Operands, L, HasNUW, HasNSW);
1948 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
1949 /// Simplify the expression as much as possible.
1951 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
1953 bool HasNUW, bool HasNSW) {
1954 if (Operands.size() == 1) return Operands[0];
1956 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
1957 assert(getEffectiveSCEVType(Operands[i]->getType()) ==
1958 getEffectiveSCEVType(Operands[0]->getType()) &&
1959 "SCEVAddRecExpr operand types don't match!");
1962 if (Operands.back()->isZero()) {
1963 Operands.pop_back();
1964 return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0} --> X
1967 // It's tempting to want to call getMaxBackedgeTakenCount count here and
1968 // use that information to infer NUW and NSW flags. However, computing a
1969 // BE count requires calling getAddRecExpr, so we may not yet have a
1970 // meaningful BE count at this point (and if we don't, we'd be stuck
1971 // with a SCEVCouldNotCompute as the cached BE count).
1973 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1974 if (!HasNUW && HasNSW) {
1976 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
1977 if (!isKnownNonNegative(Operands[i])) {
1981 if (All) HasNUW = true;
1984 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
1985 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
1986 const Loop *NestedLoop = NestedAR->getLoop();
1987 if (L->contains(NestedLoop->getHeader()) ?
1988 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
1989 (!NestedLoop->contains(L->getHeader()) &&
1990 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
1991 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
1992 NestedAR->op_end());
1993 Operands[0] = NestedAR->getStart();
1994 // AddRecs require their operands be loop-invariant with respect to their
1995 // loops. Don't perform this transformation if it would break this
1997 bool AllInvariant = true;
1998 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
1999 if (!Operands[i]->isLoopInvariant(L)) {
2000 AllInvariant = false;
2004 NestedOperands[0] = getAddRecExpr(Operands, L);
2005 AllInvariant = true;
2006 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2007 if (!NestedOperands[i]->isLoopInvariant(NestedLoop)) {
2008 AllInvariant = false;
2012 // Ok, both add recurrences are valid after the transformation.
2013 return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
2015 // Reset Operands to its original state.
2016 Operands[0] = NestedAR;
2020 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2021 // already have one, otherwise create a new one.
2022 FoldingSetNodeID ID;
2023 ID.AddInteger(scAddRecExpr);
2024 ID.AddInteger(Operands.size());
2025 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2026 ID.AddPointer(Operands[i]);
2030 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2032 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2033 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2034 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2035 O, Operands.size(), L);
2036 UniqueSCEVs.InsertNode(S, IP);
2038 if (HasNUW) S->setHasNoUnsignedWrap(true);
2039 if (HasNSW) S->setHasNoSignedWrap(true);
2043 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2045 SmallVector<const SCEV *, 2> Ops;
2048 return getSMaxExpr(Ops);
2052 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2053 assert(!Ops.empty() && "Cannot get empty smax!");
2054 if (Ops.size() == 1) return Ops[0];
2056 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2057 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
2058 getEffectiveSCEVType(Ops[0]->getType()) &&
2059 "SCEVSMaxExpr operand types don't match!");
2062 // Sort by complexity, this groups all similar expression types together.
2063 GroupByComplexity(Ops, LI);
2065 // If there are any constants, fold them together.
2067 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2069 assert(Idx < Ops.size());
2070 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2071 // We found two constants, fold them together!
2072 ConstantInt *Fold = ConstantInt::get(getContext(),
2073 APIntOps::smax(LHSC->getValue()->getValue(),
2074 RHSC->getValue()->getValue()));
2075 Ops[0] = getConstant(Fold);
2076 Ops.erase(Ops.begin()+1); // Erase the folded element
2077 if (Ops.size() == 1) return Ops[0];
2078 LHSC = cast<SCEVConstant>(Ops[0]);
2081 // If we are left with a constant minimum-int, strip it off.
2082 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2083 Ops.erase(Ops.begin());
2085 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2086 // If we have an smax with a constant maximum-int, it will always be
2091 if (Ops.size() == 1) return Ops[0];
2094 // Find the first SMax
2095 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2098 // Check to see if one of the operands is an SMax. If so, expand its operands
2099 // onto our operand list, and recurse to simplify.
2100 if (Idx < Ops.size()) {
2101 bool DeletedSMax = false;
2102 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2103 Ops.erase(Ops.begin()+Idx);
2104 Ops.append(SMax->op_begin(), SMax->op_end());
2109 return getSMaxExpr(Ops);
2112 // Okay, check to see if the same value occurs in the operand list twice. If
2113 // so, delete one. Since we sorted the list, these values are required to
2115 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2116 // X smax Y smax Y --> X smax Y
2117 // X smax Y --> X, if X is always greater than Y
2118 if (Ops[i] == Ops[i+1] ||
2119 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2120 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2122 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2123 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2127 if (Ops.size() == 1) return Ops[0];
2129 assert(!Ops.empty() && "Reduced smax down to nothing!");
2131 // Okay, it looks like we really DO need an smax expr. Check to see if we
2132 // already have one, otherwise create a new one.
2133 FoldingSetNodeID ID;
2134 ID.AddInteger(scSMaxExpr);
2135 ID.AddInteger(Ops.size());
2136 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2137 ID.AddPointer(Ops[i]);
2139 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2140 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2141 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2142 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2144 UniqueSCEVs.InsertNode(S, IP);
2148 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2150 SmallVector<const SCEV *, 2> Ops;
2153 return getUMaxExpr(Ops);
2157 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2158 assert(!Ops.empty() && "Cannot get empty umax!");
2159 if (Ops.size() == 1) return Ops[0];
2161 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2162 assert(getEffectiveSCEVType(Ops[i]->getType()) ==
2163 getEffectiveSCEVType(Ops[0]->getType()) &&
2164 "SCEVUMaxExpr operand types don't match!");
2167 // Sort by complexity, this groups all similar expression types together.
2168 GroupByComplexity(Ops, LI);
2170 // If there are any constants, fold them together.
2172 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2174 assert(Idx < Ops.size());
2175 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2176 // We found two constants, fold them together!
2177 ConstantInt *Fold = ConstantInt::get(getContext(),
2178 APIntOps::umax(LHSC->getValue()->getValue(),
2179 RHSC->getValue()->getValue()));
2180 Ops[0] = getConstant(Fold);
2181 Ops.erase(Ops.begin()+1); // Erase the folded element
2182 if (Ops.size() == 1) return Ops[0];
2183 LHSC = cast<SCEVConstant>(Ops[0]);
2186 // If we are left with a constant minimum-int, strip it off.
2187 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2188 Ops.erase(Ops.begin());
2190 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2191 // If we have an umax with a constant maximum-int, it will always be
2196 if (Ops.size() == 1) return Ops[0];
2199 // Find the first UMax
2200 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2203 // Check to see if one of the operands is a UMax. If so, expand its operands
2204 // onto our operand list, and recurse to simplify.
2205 if (Idx < Ops.size()) {
2206 bool DeletedUMax = false;
2207 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2208 Ops.erase(Ops.begin()+Idx);
2209 Ops.append(UMax->op_begin(), UMax->op_end());
2214 return getUMaxExpr(Ops);
2217 // Okay, check to see if the same value occurs in the operand list twice. If
2218 // so, delete one. Since we sorted the list, these values are required to
2220 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2221 // X umax Y umax Y --> X umax Y
2222 // X umax Y --> X, if X is always greater than Y
2223 if (Ops[i] == Ops[i+1] ||
2224 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2225 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2227 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2228 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2232 if (Ops.size() == 1) return Ops[0];
2234 assert(!Ops.empty() && "Reduced umax down to nothing!");
2236 // Okay, it looks like we really DO need a umax expr. Check to see if we
2237 // already have one, otherwise create a new one.
2238 FoldingSetNodeID ID;
2239 ID.AddInteger(scUMaxExpr);
2240 ID.AddInteger(Ops.size());
2241 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2242 ID.AddPointer(Ops[i]);
2244 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2245 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2246 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2247 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2249 UniqueSCEVs.InsertNode(S, IP);
2253 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2255 // ~smax(~x, ~y) == smin(x, y).
2256 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2259 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2261 // ~umax(~x, ~y) == umin(x, y)
2262 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2265 const SCEV *ScalarEvolution::getSizeOfExpr(const Type *AllocTy) {
2266 // If we have TargetData, we can bypass creating a target-independent
2267 // constant expression and then folding it back into a ConstantInt.
2268 // This is just a compile-time optimization.
2270 return getConstant(TD->getIntPtrType(getContext()),
2271 TD->getTypeAllocSize(AllocTy));
2273 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2274 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2275 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2277 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2278 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2281 const SCEV *ScalarEvolution::getAlignOfExpr(const Type *AllocTy) {
2282 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2283 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2284 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2286 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2287 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2290 const SCEV *ScalarEvolution::getOffsetOfExpr(const StructType *STy,
2292 // If we have TargetData, we can bypass creating a target-independent
2293 // constant expression and then folding it back into a ConstantInt.
2294 // This is just a compile-time optimization.
2296 return getConstant(TD->getIntPtrType(getContext()),
2297 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2299 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2300 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2301 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2303 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2304 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2307 const SCEV *ScalarEvolution::getOffsetOfExpr(const Type *CTy,
2308 Constant *FieldNo) {
2309 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2310 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2311 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2313 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2314 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2317 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2318 // Don't attempt to do anything other than create a SCEVUnknown object
2319 // here. createSCEV only calls getUnknown after checking for all other
2320 // interesting possibilities, and any other code that calls getUnknown
2321 // is doing so in order to hide a value from SCEV canonicalization.
2323 FoldingSetNodeID ID;
2324 ID.AddInteger(scUnknown);
2327 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2328 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V);
2329 UniqueSCEVs.InsertNode(S, IP);
2333 //===----------------------------------------------------------------------===//
2334 // Basic SCEV Analysis and PHI Idiom Recognition Code
2337 /// isSCEVable - Test if values of the given type are analyzable within
2338 /// the SCEV framework. This primarily includes integer types, and it
2339 /// can optionally include pointer types if the ScalarEvolution class
2340 /// has access to target-specific information.
2341 bool ScalarEvolution::isSCEVable(const Type *Ty) const {
2342 // Integers and pointers are always SCEVable.
2343 return Ty->isIntegerTy() || Ty->isPointerTy();
2346 /// getTypeSizeInBits - Return the size in bits of the specified type,
2347 /// for which isSCEVable must return true.
2348 uint64_t ScalarEvolution::getTypeSizeInBits(const Type *Ty) const {
2349 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2351 // If we have a TargetData, use it!
2353 return TD->getTypeSizeInBits(Ty);
2355 // Integer types have fixed sizes.
2356 if (Ty->isIntegerTy())
2357 return Ty->getPrimitiveSizeInBits();
2359 // The only other support type is pointer. Without TargetData, conservatively
2360 // assume pointers are 64-bit.
2361 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2365 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2366 /// the given type and which represents how SCEV will treat the given
2367 /// type, for which isSCEVable must return true. For pointer types,
2368 /// this is the pointer-sized integer type.
2369 const Type *ScalarEvolution::getEffectiveSCEVType(const Type *Ty) const {
2370 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2372 if (Ty->isIntegerTy())
2375 // The only other support type is pointer.
2376 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2377 if (TD) return TD->getIntPtrType(getContext());
2379 // Without TargetData, conservatively assume pointers are 64-bit.
2380 return Type::getInt64Ty(getContext());
2383 const SCEV *ScalarEvolution::getCouldNotCompute() {
2384 return &CouldNotCompute;
2387 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2388 /// expression and create a new one.
2389 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2390 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2392 std::map<SCEVCallbackVH, const SCEV *>::iterator I = Scalars.find(V);
2393 if (I != Scalars.end()) return I->second;
2394 const SCEV *S = createSCEV(V);
2395 Scalars.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2399 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2401 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2402 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2404 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2406 const Type *Ty = V->getType();
2407 Ty = getEffectiveSCEVType(Ty);
2408 return getMulExpr(V,
2409 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2412 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2413 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2414 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2416 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2418 const Type *Ty = V->getType();
2419 Ty = getEffectiveSCEVType(Ty);
2420 const SCEV *AllOnes =
2421 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2422 return getMinusSCEV(AllOnes, V);
2425 /// getMinusSCEV - Return a SCEV corresponding to LHS - RHS.
2427 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
2430 return getAddExpr(LHS, getNegativeSCEV(RHS));
2433 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2434 /// input value to the specified type. If the type must be extended, it is zero
2437 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V,
2439 const Type *SrcTy = V->getType();
2440 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2441 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2442 "Cannot truncate or zero extend with non-integer arguments!");
2443 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2444 return V; // No conversion
2445 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2446 return getTruncateExpr(V, Ty);
2447 return getZeroExtendExpr(V, Ty);
2450 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2451 /// input value to the specified type. If the type must be extended, it is sign
2454 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2456 const Type *SrcTy = V->getType();
2457 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2458 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2459 "Cannot truncate or zero extend with non-integer arguments!");
2460 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2461 return V; // No conversion
2462 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2463 return getTruncateExpr(V, Ty);
2464 return getSignExtendExpr(V, Ty);
2467 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2468 /// input value to the specified type. If the type must be extended, it is zero
2469 /// extended. The conversion must not be narrowing.
2471 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, const Type *Ty) {
2472 const Type *SrcTy = V->getType();
2473 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2474 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2475 "Cannot noop or zero extend with non-integer arguments!");
2476 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2477 "getNoopOrZeroExtend cannot truncate!");
2478 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2479 return V; // No conversion
2480 return getZeroExtendExpr(V, Ty);
2483 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2484 /// input value to the specified type. If the type must be extended, it is sign
2485 /// extended. The conversion must not be narrowing.
2487 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, const Type *Ty) {
2488 const Type *SrcTy = V->getType();
2489 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2490 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2491 "Cannot noop or sign extend with non-integer arguments!");
2492 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2493 "getNoopOrSignExtend cannot truncate!");
2494 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2495 return V; // No conversion
2496 return getSignExtendExpr(V, Ty);
2499 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2500 /// the input value to the specified type. If the type must be extended,
2501 /// it is extended with unspecified bits. The conversion must not be
2504 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, const Type *Ty) {
2505 const Type *SrcTy = V->getType();
2506 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2507 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2508 "Cannot noop or any extend with non-integer arguments!");
2509 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2510 "getNoopOrAnyExtend cannot truncate!");
2511 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2512 return V; // No conversion
2513 return getAnyExtendExpr(V, Ty);
2516 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2517 /// input value to the specified type. The conversion must not be widening.
2519 ScalarEvolution::getTruncateOrNoop(const SCEV *V, const Type *Ty) {
2520 const Type *SrcTy = V->getType();
2521 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2522 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2523 "Cannot truncate or noop with non-integer arguments!");
2524 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2525 "getTruncateOrNoop cannot extend!");
2526 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2527 return V; // No conversion
2528 return getTruncateExpr(V, Ty);
2531 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2532 /// the types using zero-extension, and then perform a umax operation
2534 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2536 const SCEV *PromotedLHS = LHS;
2537 const SCEV *PromotedRHS = RHS;
2539 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2540 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2542 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2544 return getUMaxExpr(PromotedLHS, PromotedRHS);
2547 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2548 /// the types using zero-extension, and then perform a umin operation
2550 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2552 const SCEV *PromotedLHS = LHS;
2553 const SCEV *PromotedRHS = RHS;
2555 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2556 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2558 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2560 return getUMinExpr(PromotedLHS, PromotedRHS);
2563 /// PushDefUseChildren - Push users of the given Instruction
2564 /// onto the given Worklist.
2566 PushDefUseChildren(Instruction *I,
2567 SmallVectorImpl<Instruction *> &Worklist) {
2568 // Push the def-use children onto the Worklist stack.
2569 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2571 Worklist.push_back(cast<Instruction>(UI));
2574 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2575 /// instructions that depend on the given instruction and removes them from
2576 /// the Scalars map if they reference SymName. This is used during PHI
2579 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2580 SmallVector<Instruction *, 16> Worklist;
2581 PushDefUseChildren(PN, Worklist);
2583 SmallPtrSet<Instruction *, 8> Visited;
2585 while (!Worklist.empty()) {
2586 Instruction *I = Worklist.pop_back_val();
2587 if (!Visited.insert(I)) continue;
2589 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
2590 Scalars.find(static_cast<Value *>(I));
2591 if (It != Scalars.end()) {
2592 // Short-circuit the def-use traversal if the symbolic name
2593 // ceases to appear in expressions.
2594 if (It->second != SymName && !It->second->hasOperand(SymName))
2597 // SCEVUnknown for a PHI either means that it has an unrecognized
2598 // structure, it's a PHI that's in the progress of being computed
2599 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2600 // additional loop trip count information isn't going to change anything.
2601 // In the second case, createNodeForPHI will perform the necessary
2602 // updates on its own when it gets to that point. In the third, we do
2603 // want to forget the SCEVUnknown.
2604 if (!isa<PHINode>(I) ||
2605 !isa<SCEVUnknown>(It->second) ||
2606 (I != PN && It->second == SymName)) {
2607 ValuesAtScopes.erase(It->second);
2612 PushDefUseChildren(I, Worklist);
2616 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2617 /// a loop header, making it a potential recurrence, or it doesn't.
2619 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2620 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2621 if (L->getHeader() == PN->getParent()) {
2622 // The loop may have multiple entrances or multiple exits; we can analyze
2623 // this phi as an addrec if it has a unique entry value and a unique
2625 Value *BEValueV = 0, *StartValueV = 0;
2626 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2627 Value *V = PN->getIncomingValue(i);
2628 if (L->contains(PN->getIncomingBlock(i))) {
2631 } else if (BEValueV != V) {
2635 } else if (!StartValueV) {
2637 } else if (StartValueV != V) {
2642 if (BEValueV && StartValueV) {
2643 // While we are analyzing this PHI node, handle its value symbolically.
2644 const SCEV *SymbolicName = getUnknown(PN);
2645 assert(Scalars.find(PN) == Scalars.end() &&
2646 "PHI node already processed?");
2647 Scalars.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2649 // Using this symbolic name for the PHI, analyze the value coming around
2651 const SCEV *BEValue = getSCEV(BEValueV);
2653 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2654 // has a special value for the first iteration of the loop.
2656 // If the value coming around the backedge is an add with the symbolic
2657 // value we just inserted, then we found a simple induction variable!
2658 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2659 // If there is a single occurrence of the symbolic value, replace it
2660 // with a recurrence.
2661 unsigned FoundIndex = Add->getNumOperands();
2662 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2663 if (Add->getOperand(i) == SymbolicName)
2664 if (FoundIndex == e) {
2669 if (FoundIndex != Add->getNumOperands()) {
2670 // Create an add with everything but the specified operand.
2671 SmallVector<const SCEV *, 8> Ops;
2672 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2673 if (i != FoundIndex)
2674 Ops.push_back(Add->getOperand(i));
2675 const SCEV *Accum = getAddExpr(Ops);
2677 // This is not a valid addrec if the step amount is varying each
2678 // loop iteration, but is not itself an addrec in this loop.
2679 if (Accum->isLoopInvariant(L) ||
2680 (isa<SCEVAddRecExpr>(Accum) &&
2681 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2682 bool HasNUW = false;
2683 bool HasNSW = false;
2685 // If the increment doesn't overflow, then neither the addrec nor
2686 // the post-increment will overflow.
2687 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2688 if (OBO->hasNoUnsignedWrap())
2690 if (OBO->hasNoSignedWrap())
2694 const SCEV *StartVal = getSCEV(StartValueV);
2695 const SCEV *PHISCEV =
2696 getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
2698 // Since the no-wrap flags are on the increment, they apply to the
2699 // post-incremented value as well.
2700 if (Accum->isLoopInvariant(L))
2701 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2702 Accum, L, HasNUW, HasNSW);
2704 // Okay, for the entire analysis of this edge we assumed the PHI
2705 // to be symbolic. We now need to go back and purge all of the
2706 // entries for the scalars that use the symbolic expression.
2707 ForgetSymbolicName(PN, SymbolicName);
2708 Scalars[SCEVCallbackVH(PN, this)] = PHISCEV;
2712 } else if (const SCEVAddRecExpr *AddRec =
2713 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2714 // Otherwise, this could be a loop like this:
2715 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2716 // In this case, j = {1,+,1} and BEValue is j.
2717 // Because the other in-value of i (0) fits the evolution of BEValue
2718 // i really is an addrec evolution.
2719 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2720 const SCEV *StartVal = getSCEV(StartValueV);
2722 // If StartVal = j.start - j.stride, we can use StartVal as the
2723 // initial step of the addrec evolution.
2724 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2725 AddRec->getOperand(1))) {
2726 const SCEV *PHISCEV =
2727 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
2729 // Okay, for the entire analysis of this edge we assumed the PHI
2730 // to be symbolic. We now need to go back and purge all of the
2731 // entries for the scalars that use the symbolic expression.
2732 ForgetSymbolicName(PN, SymbolicName);
2733 Scalars[SCEVCallbackVH(PN, this)] = PHISCEV;
2741 // If the PHI has a single incoming value, follow that value, unless the
2742 // PHI's incoming blocks are in a different loop, in which case doing so
2743 // risks breaking LCSSA form. Instcombine would normally zap these, but
2744 // it doesn't have DominatorTree information, so it may miss cases.
2745 if (Value *V = PN->hasConstantValue(DT)) {
2746 bool AllSameLoop = true;
2747 Loop *PNLoop = LI->getLoopFor(PN->getParent());
2748 for (size_t i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
2749 if (LI->getLoopFor(PN->getIncomingBlock(i)) != PNLoop) {
2750 AllSameLoop = false;
2757 // If it's not a loop phi, we can't handle it yet.
2758 return getUnknown(PN);
2761 /// createNodeForGEP - Expand GEP instructions into add and multiply
2762 /// operations. This allows them to be analyzed by regular SCEV code.
2764 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
2766 bool InBounds = GEP->isInBounds();
2767 const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
2768 Value *Base = GEP->getOperand(0);
2769 // Don't attempt to analyze GEPs over unsized objects.
2770 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
2771 return getUnknown(GEP);
2772 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
2773 gep_type_iterator GTI = gep_type_begin(GEP);
2774 for (GetElementPtrInst::op_iterator I = next(GEP->op_begin()),
2778 // Compute the (potentially symbolic) offset in bytes for this index.
2779 if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
2780 // For a struct, add the member offset.
2781 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
2782 TotalOffset = getAddExpr(TotalOffset,
2783 getOffsetOfExpr(STy, FieldNo),
2784 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2786 // For an array, add the element offset, explicitly scaled.
2787 const SCEV *LocalOffset = getSCEV(Index);
2788 // Getelementptr indices are signed.
2789 LocalOffset = getTruncateOrSignExtend(LocalOffset, IntPtrTy);
2790 // Lower "inbounds" GEPs to NSW arithmetic.
2791 LocalOffset = getMulExpr(LocalOffset, getSizeOfExpr(*GTI),
2792 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2793 TotalOffset = getAddExpr(TotalOffset, LocalOffset,
2794 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2797 return getAddExpr(getSCEV(Base), TotalOffset,
2798 /*HasNUW=*/false, /*HasNSW=*/InBounds);
2801 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
2802 /// guaranteed to end in (at every loop iteration). It is, at the same time,
2803 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
2804 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
2806 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
2807 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2808 return C->getValue()->getValue().countTrailingZeros();
2810 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
2811 return std::min(GetMinTrailingZeros(T->getOperand()),
2812 (uint32_t)getTypeSizeInBits(T->getType()));
2814 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
2815 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2816 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2817 getTypeSizeInBits(E->getType()) : OpRes;
2820 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
2821 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2822 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2823 getTypeSizeInBits(E->getType()) : OpRes;
2826 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
2827 // The result is the min of all operands results.
2828 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2829 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2830 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2834 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
2835 // The result is the sum of all operands results.
2836 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
2837 uint32_t BitWidth = getTypeSizeInBits(M->getType());
2838 for (unsigned i = 1, e = M->getNumOperands();
2839 SumOpRes != BitWidth && i != e; ++i)
2840 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
2845 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
2846 // The result is the min of all operands results.
2847 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2848 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2849 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2853 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
2854 // The result is the min of all operands results.
2855 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2856 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2857 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2861 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
2862 // The result is the min of all operands results.
2863 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2864 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2865 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2869 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2870 // For a SCEVUnknown, ask ValueTracking.
2871 unsigned BitWidth = getTypeSizeInBits(U->getType());
2872 APInt Mask = APInt::getAllOnesValue(BitWidth);
2873 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
2874 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
2875 return Zeros.countTrailingOnes();
2882 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
2885 ScalarEvolution::getUnsignedRange(const SCEV *S) {
2887 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2888 return ConstantRange(C->getValue()->getValue());
2890 unsigned BitWidth = getTypeSizeInBits(S->getType());
2891 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
2893 // If the value has known zeros, the maximum unsigned value will have those
2894 // known zeros as well.
2895 uint32_t TZ = GetMinTrailingZeros(S);
2897 ConservativeResult =
2898 ConstantRange(APInt::getMinValue(BitWidth),
2899 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
2901 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2902 ConstantRange X = getUnsignedRange(Add->getOperand(0));
2903 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
2904 X = X.add(getUnsignedRange(Add->getOperand(i)));
2905 return ConservativeResult.intersectWith(X);
2908 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2909 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
2910 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
2911 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
2912 return ConservativeResult.intersectWith(X);
2915 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
2916 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
2917 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
2918 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
2919 return ConservativeResult.intersectWith(X);
2922 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
2923 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
2924 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
2925 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
2926 return ConservativeResult.intersectWith(X);
2929 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
2930 ConstantRange X = getUnsignedRange(UDiv->getLHS());
2931 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
2932 return ConservativeResult.intersectWith(X.udiv(Y));
2935 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
2936 ConstantRange X = getUnsignedRange(ZExt->getOperand());
2937 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
2940 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
2941 ConstantRange X = getUnsignedRange(SExt->getOperand());
2942 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
2945 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
2946 ConstantRange X = getUnsignedRange(Trunc->getOperand());
2947 return ConservativeResult.intersectWith(X.truncate(BitWidth));
2950 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
2951 // If there's no unsigned wrap, the value will never be less than its
2953 if (AddRec->hasNoUnsignedWrap())
2954 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
2955 if (!C->getValue()->isZero())
2956 ConservativeResult =
2957 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0));
2959 // TODO: non-affine addrec
2960 if (AddRec->isAffine()) {
2961 const Type *Ty = AddRec->getType();
2962 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
2963 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
2964 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
2965 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
2967 const SCEV *Start = AddRec->getStart();
2968 const SCEV *Step = AddRec->getStepRecurrence(*this);
2970 ConstantRange StartRange = getUnsignedRange(Start);
2971 ConstantRange StepRange = getSignedRange(Step);
2972 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
2973 ConstantRange EndRange =
2974 StartRange.add(MaxBECountRange.multiply(StepRange));
2976 // Check for overflow. This must be done with ConstantRange arithmetic
2977 // because we could be called from within the ScalarEvolution overflow
2979 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
2980 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
2981 ConstantRange ExtMaxBECountRange =
2982 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
2983 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
2984 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
2986 return ConservativeResult;
2988 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
2989 EndRange.getUnsignedMin());
2990 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
2991 EndRange.getUnsignedMax());
2992 if (Min.isMinValue() && Max.isMaxValue())
2993 return ConservativeResult;
2994 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
2998 return ConservativeResult;
3001 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3002 // For a SCEVUnknown, ask ValueTracking.
3003 APInt Mask = APInt::getAllOnesValue(BitWidth);
3004 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3005 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3006 if (Ones == ~Zeros + 1)
3007 return ConservativeResult;
3008 return ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
3011 return ConservativeResult;
3014 /// getSignedRange - Determine the signed range for a particular SCEV.
3017 ScalarEvolution::getSignedRange(const SCEV *S) {
3019 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3020 return ConstantRange(C->getValue()->getValue());
3022 unsigned BitWidth = getTypeSizeInBits(S->getType());
3023 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3025 // If the value has known zeros, the maximum signed value will have those
3026 // known zeros as well.
3027 uint32_t TZ = GetMinTrailingZeros(S);
3029 ConservativeResult =
3030 ConstantRange(APInt::getSignedMinValue(BitWidth),
3031 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3033 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3034 ConstantRange X = getSignedRange(Add->getOperand(0));
3035 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3036 X = X.add(getSignedRange(Add->getOperand(i)));
3037 return ConservativeResult.intersectWith(X);
3040 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3041 ConstantRange X = getSignedRange(Mul->getOperand(0));
3042 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3043 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3044 return ConservativeResult.intersectWith(X);
3047 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3048 ConstantRange X = getSignedRange(SMax->getOperand(0));
3049 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3050 X = X.smax(getSignedRange(SMax->getOperand(i)));
3051 return ConservativeResult.intersectWith(X);
3054 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3055 ConstantRange X = getSignedRange(UMax->getOperand(0));
3056 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3057 X = X.umax(getSignedRange(UMax->getOperand(i)));
3058 return ConservativeResult.intersectWith(X);
3061 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3062 ConstantRange X = getSignedRange(UDiv->getLHS());
3063 ConstantRange Y = getSignedRange(UDiv->getRHS());
3064 return ConservativeResult.intersectWith(X.udiv(Y));
3067 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3068 ConstantRange X = getSignedRange(ZExt->getOperand());
3069 return ConservativeResult.intersectWith(X.zeroExtend(BitWidth));
3072 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3073 ConstantRange X = getSignedRange(SExt->getOperand());
3074 return ConservativeResult.intersectWith(X.signExtend(BitWidth));
3077 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3078 ConstantRange X = getSignedRange(Trunc->getOperand());
3079 return ConservativeResult.intersectWith(X.truncate(BitWidth));
3082 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3083 // If there's no signed wrap, and all the operands have the same sign or
3084 // zero, the value won't ever change sign.
3085 if (AddRec->hasNoSignedWrap()) {
3086 bool AllNonNeg = true;
3087 bool AllNonPos = true;
3088 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3089 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3090 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3093 ConservativeResult = ConservativeResult.intersectWith(
3094 ConstantRange(APInt(BitWidth, 0),
3095 APInt::getSignedMinValue(BitWidth)));
3097 ConservativeResult = ConservativeResult.intersectWith(
3098 ConstantRange(APInt::getSignedMinValue(BitWidth),
3099 APInt(BitWidth, 1)));
3102 // TODO: non-affine addrec
3103 if (AddRec->isAffine()) {
3104 const Type *Ty = AddRec->getType();
3105 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3106 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3107 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3108 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3110 const SCEV *Start = AddRec->getStart();
3111 const SCEV *Step = AddRec->getStepRecurrence(*this);
3113 ConstantRange StartRange = getSignedRange(Start);
3114 ConstantRange StepRange = getSignedRange(Step);
3115 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3116 ConstantRange EndRange =
3117 StartRange.add(MaxBECountRange.multiply(StepRange));
3119 // Check for overflow. This must be done with ConstantRange arithmetic
3120 // because we could be called from within the ScalarEvolution overflow
3122 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3123 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3124 ConstantRange ExtMaxBECountRange =
3125 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3126 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3127 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3129 return ConservativeResult;
3131 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3132 EndRange.getSignedMin());
3133 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3134 EndRange.getSignedMax());
3135 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3136 return ConservativeResult;
3137 return ConservativeResult.intersectWith(ConstantRange(Min, Max+1));
3141 return ConservativeResult;
3144 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3145 // For a SCEVUnknown, ask ValueTracking.
3146 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3147 return ConservativeResult;
3148 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3150 return ConservativeResult;
3151 return ConservativeResult.intersectWith(
3152 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3153 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1));
3156 return ConservativeResult;
3159 /// createSCEV - We know that there is no SCEV for the specified value.
3160 /// Analyze the expression.
3162 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3163 if (!isSCEVable(V->getType()))
3164 return getUnknown(V);
3166 unsigned Opcode = Instruction::UserOp1;
3167 if (Instruction *I = dyn_cast<Instruction>(V)) {
3168 Opcode = I->getOpcode();
3170 // Don't attempt to analyze instructions in blocks that aren't
3171 // reachable. Such instructions don't matter, and they aren't required
3172 // to obey basic rules for definitions dominating uses which this
3173 // analysis depends on.
3174 if (!DT->isReachableFromEntry(I->getParent()))
3175 return getUnknown(V);
3176 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3177 Opcode = CE->getOpcode();
3178 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3179 return getConstant(CI);
3180 else if (isa<ConstantPointerNull>(V))
3181 return getConstant(V->getType(), 0);
3182 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3183 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3185 return getUnknown(V);
3187 Operator *U = cast<Operator>(V);
3189 case Instruction::Add:
3190 // Don't transfer the NSW and NUW bits from the Add instruction to the
3191 // Add expression, because the Instruction may be guarded by control
3192 // flow and the no-overflow bits may not be valid for the expression in
3194 return getAddExpr(getSCEV(U->getOperand(0)),
3195 getSCEV(U->getOperand(1)));
3196 case Instruction::Mul:
3197 // Don't transfer the NSW and NUW bits from the Mul instruction to the
3198 // Mul expression, as with Add.
3199 return getMulExpr(getSCEV(U->getOperand(0)),
3200 getSCEV(U->getOperand(1)));
3201 case Instruction::UDiv:
3202 return getUDivExpr(getSCEV(U->getOperand(0)),
3203 getSCEV(U->getOperand(1)));
3204 case Instruction::Sub:
3205 return getMinusSCEV(getSCEV(U->getOperand(0)),
3206 getSCEV(U->getOperand(1)));
3207 case Instruction::And:
3208 // For an expression like x&255 that merely masks off the high bits,
3209 // use zext(trunc(x)) as the SCEV expression.
3210 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3211 if (CI->isNullValue())
3212 return getSCEV(U->getOperand(1));
3213 if (CI->isAllOnesValue())
3214 return getSCEV(U->getOperand(0));
3215 const APInt &A = CI->getValue();
3217 // Instcombine's ShrinkDemandedConstant may strip bits out of
3218 // constants, obscuring what would otherwise be a low-bits mask.
3219 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3220 // knew about to reconstruct a low-bits mask value.
3221 unsigned LZ = A.countLeadingZeros();
3222 unsigned BitWidth = A.getBitWidth();
3223 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3224 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3225 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3227 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3229 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3231 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3232 IntegerType::get(getContext(), BitWidth - LZ)),
3237 case Instruction::Or:
3238 // If the RHS of the Or is a constant, we may have something like:
3239 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3240 // optimizations will transparently handle this case.
3242 // In order for this transformation to be safe, the LHS must be of the
3243 // form X*(2^n) and the Or constant must be less than 2^n.
3244 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3245 const SCEV *LHS = getSCEV(U->getOperand(0));
3246 const APInt &CIVal = CI->getValue();
3247 if (GetMinTrailingZeros(LHS) >=
3248 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3249 // Build a plain add SCEV.
3250 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3251 // If the LHS of the add was an addrec and it has no-wrap flags,
3252 // transfer the no-wrap flags, since an or won't introduce a wrap.
3253 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3254 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3255 if (OldAR->hasNoUnsignedWrap())
3256 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoUnsignedWrap(true);
3257 if (OldAR->hasNoSignedWrap())
3258 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoSignedWrap(true);
3264 case Instruction::Xor:
3265 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3266 // If the RHS of the xor is a signbit, then this is just an add.
3267 // Instcombine turns add of signbit into xor as a strength reduction step.
3268 if (CI->getValue().isSignBit())
3269 return getAddExpr(getSCEV(U->getOperand(0)),
3270 getSCEV(U->getOperand(1)));
3272 // If the RHS of xor is -1, then this is a not operation.
3273 if (CI->isAllOnesValue())
3274 return getNotSCEV(getSCEV(U->getOperand(0)));
3276 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3277 // This is a variant of the check for xor with -1, and it handles
3278 // the case where instcombine has trimmed non-demanded bits out
3279 // of an xor with -1.
3280 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3281 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3282 if (BO->getOpcode() == Instruction::And &&
3283 LCI->getValue() == CI->getValue())
3284 if (const SCEVZeroExtendExpr *Z =
3285 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3286 const Type *UTy = U->getType();
3287 const SCEV *Z0 = Z->getOperand();
3288 const Type *Z0Ty = Z0->getType();
3289 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3291 // If C is a low-bits mask, the zero extend is serving to
3292 // mask off the high bits. Complement the operand and
3293 // re-apply the zext.
3294 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3295 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3297 // If C is a single bit, it may be in the sign-bit position
3298 // before the zero-extend. In this case, represent the xor
3299 // using an add, which is equivalent, and re-apply the zext.
3300 APInt Trunc = APInt(CI->getValue()).trunc(Z0TySize);
3301 if (APInt(Trunc).zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3303 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3309 case Instruction::Shl:
3310 // Turn shift left of a constant amount into a multiply.
3311 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3312 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3314 // If the shift count is not less than the bitwidth, the result of
3315 // the shift is undefined. Don't try to analyze it, because the
3316 // resolution chosen here may differ from the resolution chosen in
3317 // other parts of the compiler.
3318 if (SA->getValue().uge(BitWidth))
3321 Constant *X = ConstantInt::get(getContext(),
3322 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3323 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3327 case Instruction::LShr:
3328 // Turn logical shift right of a constant into a unsigned divide.
3329 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3330 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3332 // If the shift count is not less than the bitwidth, the result of
3333 // the shift is undefined. Don't try to analyze it, because the
3334 // resolution chosen here may differ from the resolution chosen in
3335 // other parts of the compiler.
3336 if (SA->getValue().uge(BitWidth))
3339 Constant *X = ConstantInt::get(getContext(),
3340 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3341 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3345 case Instruction::AShr:
3346 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3347 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3348 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3349 if (L->getOpcode() == Instruction::Shl &&
3350 L->getOperand(1) == U->getOperand(1)) {
3351 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3353 // If the shift count is not less than the bitwidth, the result of
3354 // the shift is undefined. Don't try to analyze it, because the
3355 // resolution chosen here may differ from the resolution chosen in
3356 // other parts of the compiler.
3357 if (CI->getValue().uge(BitWidth))
3360 uint64_t Amt = BitWidth - CI->getZExtValue();
3361 if (Amt == BitWidth)
3362 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3364 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3365 IntegerType::get(getContext(),
3371 case Instruction::Trunc:
3372 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3374 case Instruction::ZExt:
3375 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3377 case Instruction::SExt:
3378 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3380 case Instruction::BitCast:
3381 // BitCasts are no-op casts so we just eliminate the cast.
3382 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3383 return getSCEV(U->getOperand(0));
3386 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3387 // lead to pointer expressions which cannot safely be expanded to GEPs,
3388 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3389 // simplifying integer expressions.
3391 case Instruction::GetElementPtr:
3392 return createNodeForGEP(cast<GEPOperator>(U));
3394 case Instruction::PHI:
3395 return createNodeForPHI(cast<PHINode>(U));
3397 case Instruction::Select:
3398 // This could be a smax or umax that was lowered earlier.
3399 // Try to recover it.
3400 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3401 Value *LHS = ICI->getOperand(0);
3402 Value *RHS = ICI->getOperand(1);
3403 switch (ICI->getPredicate()) {
3404 case ICmpInst::ICMP_SLT:
3405 case ICmpInst::ICMP_SLE:
3406 std::swap(LHS, RHS);
3408 case ICmpInst::ICMP_SGT:
3409 case ICmpInst::ICMP_SGE:
3410 // a >s b ? a+x : b+x -> smax(a, b)+x
3411 // a >s b ? b+x : a+x -> smin(a, b)+x
3412 if (LHS->getType() == U->getType()) {
3413 const SCEV *LS = getSCEV(LHS);
3414 const SCEV *RS = getSCEV(RHS);
3415 const SCEV *LA = getSCEV(U->getOperand(1));
3416 const SCEV *RA = getSCEV(U->getOperand(2));
3417 const SCEV *LDiff = getMinusSCEV(LA, LS);
3418 const SCEV *RDiff = getMinusSCEV(RA, RS);
3420 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3421 LDiff = getMinusSCEV(LA, RS);
3422 RDiff = getMinusSCEV(RA, LS);
3424 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3427 case ICmpInst::ICMP_ULT:
3428 case ICmpInst::ICMP_ULE:
3429 std::swap(LHS, RHS);
3431 case ICmpInst::ICMP_UGT:
3432 case ICmpInst::ICMP_UGE:
3433 // a >u b ? a+x : b+x -> umax(a, b)+x
3434 // a >u b ? b+x : a+x -> umin(a, b)+x
3435 if (LHS->getType() == U->getType()) {
3436 const SCEV *LS = getSCEV(LHS);
3437 const SCEV *RS = getSCEV(RHS);
3438 const SCEV *LA = getSCEV(U->getOperand(1));
3439 const SCEV *RA = getSCEV(U->getOperand(2));
3440 const SCEV *LDiff = getMinusSCEV(LA, LS);
3441 const SCEV *RDiff = getMinusSCEV(RA, RS);
3443 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3444 LDiff = getMinusSCEV(LA, RS);
3445 RDiff = getMinusSCEV(RA, LS);
3447 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3450 case ICmpInst::ICMP_NE:
3451 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3452 if (LHS->getType() == U->getType() &&
3453 isa<ConstantInt>(RHS) &&
3454 cast<ConstantInt>(RHS)->isZero()) {
3455 const SCEV *One = getConstant(LHS->getType(), 1);
3456 const SCEV *LS = getSCEV(LHS);
3457 const SCEV *LA = getSCEV(U->getOperand(1));
3458 const SCEV *RA = getSCEV(U->getOperand(2));
3459 const SCEV *LDiff = getMinusSCEV(LA, LS);
3460 const SCEV *RDiff = getMinusSCEV(RA, One);
3462 return getAddExpr(getUMaxExpr(LS, One), LDiff);
3465 case ICmpInst::ICMP_EQ:
3466 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3467 if (LHS->getType() == U->getType() &&
3468 isa<ConstantInt>(RHS) &&
3469 cast<ConstantInt>(RHS)->isZero()) {
3470 const SCEV *One = getConstant(LHS->getType(), 1);
3471 const SCEV *LS = getSCEV(LHS);
3472 const SCEV *LA = getSCEV(U->getOperand(1));
3473 const SCEV *RA = getSCEV(U->getOperand(2));
3474 const SCEV *LDiff = getMinusSCEV(LA, One);
3475 const SCEV *RDiff = getMinusSCEV(RA, LS);
3477 return getAddExpr(getUMaxExpr(LS, One), LDiff);
3485 default: // We cannot analyze this expression.
3489 return getUnknown(V);
3494 //===----------------------------------------------------------------------===//
3495 // Iteration Count Computation Code
3498 /// getBackedgeTakenCount - If the specified loop has a predictable
3499 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3500 /// object. The backedge-taken count is the number of times the loop header
3501 /// will be branched to from within the loop. This is one less than the
3502 /// trip count of the loop, since it doesn't count the first iteration,
3503 /// when the header is branched to from outside the loop.
3505 /// Note that it is not valid to call this method on a loop without a
3506 /// loop-invariant backedge-taken count (see
3507 /// hasLoopInvariantBackedgeTakenCount).
3509 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3510 return getBackedgeTakenInfo(L).Exact;
3513 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3514 /// return the least SCEV value that is known never to be less than the
3515 /// actual backedge taken count.
3516 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3517 return getBackedgeTakenInfo(L).Max;
3520 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3521 /// onto the given Worklist.
3523 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3524 BasicBlock *Header = L->getHeader();
3526 // Push all Loop-header PHIs onto the Worklist stack.
3527 for (BasicBlock::iterator I = Header->begin();
3528 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3529 Worklist.push_back(PN);
3532 const ScalarEvolution::BackedgeTakenInfo &
3533 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3534 // Initially insert a CouldNotCompute for this loop. If the insertion
3535 // succeeds, proceed to actually compute a backedge-taken count and
3536 // update the value. The temporary CouldNotCompute value tells SCEV
3537 // code elsewhere that it shouldn't attempt to request a new
3538 // backedge-taken count, which could result in infinite recursion.
3539 std::pair<std::map<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3540 BackedgeTakenCounts.insert(std::make_pair(L, getCouldNotCompute()));
3542 BackedgeTakenInfo BECount = ComputeBackedgeTakenCount(L);
3543 if (BECount.Exact != getCouldNotCompute()) {
3544 assert(BECount.Exact->isLoopInvariant(L) &&
3545 BECount.Max->isLoopInvariant(L) &&
3546 "Computed backedge-taken count isn't loop invariant for loop!");
3547 ++NumTripCountsComputed;
3549 // Update the value in the map.
3550 Pair.first->second = BECount;
3552 if (BECount.Max != getCouldNotCompute())
3553 // Update the value in the map.
3554 Pair.first->second = BECount;
3555 if (isa<PHINode>(L->getHeader()->begin()))
3556 // Only count loops that have phi nodes as not being computable.
3557 ++NumTripCountsNotComputed;
3560 // Now that we know more about the trip count for this loop, forget any
3561 // existing SCEV values for PHI nodes in this loop since they are only
3562 // conservative estimates made without the benefit of trip count
3563 // information. This is similar to the code in forgetLoop, except that
3564 // it handles SCEVUnknown PHI nodes specially.
3565 if (BECount.hasAnyInfo()) {
3566 SmallVector<Instruction *, 16> Worklist;
3567 PushLoopPHIs(L, Worklist);
3569 SmallPtrSet<Instruction *, 8> Visited;
3570 while (!Worklist.empty()) {
3571 Instruction *I = Worklist.pop_back_val();
3572 if (!Visited.insert(I)) continue;
3574 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3575 Scalars.find(static_cast<Value *>(I));
3576 if (It != Scalars.end()) {
3577 // SCEVUnknown for a PHI either means that it has an unrecognized
3578 // structure, or it's a PHI that's in the progress of being computed
3579 // by createNodeForPHI. In the former case, additional loop trip
3580 // count information isn't going to change anything. In the later
3581 // case, createNodeForPHI will perform the necessary updates on its
3582 // own when it gets to that point.
3583 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(It->second)) {
3584 ValuesAtScopes.erase(It->second);
3587 if (PHINode *PN = dyn_cast<PHINode>(I))
3588 ConstantEvolutionLoopExitValue.erase(PN);
3591 PushDefUseChildren(I, Worklist);
3595 return Pair.first->second;
3598 /// forgetLoop - This method should be called by the client when it has
3599 /// changed a loop in a way that may effect ScalarEvolution's ability to
3600 /// compute a trip count, or if the loop is deleted.
3601 void ScalarEvolution::forgetLoop(const Loop *L) {
3602 // Drop any stored trip count value.
3603 BackedgeTakenCounts.erase(L);
3605 // Drop information about expressions based on loop-header PHIs.
3606 SmallVector<Instruction *, 16> Worklist;
3607 PushLoopPHIs(L, Worklist);
3609 SmallPtrSet<Instruction *, 8> Visited;
3610 while (!Worklist.empty()) {
3611 Instruction *I = Worklist.pop_back_val();
3612 if (!Visited.insert(I)) continue;
3614 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3615 Scalars.find(static_cast<Value *>(I));
3616 if (It != Scalars.end()) {
3617 ValuesAtScopes.erase(It->second);
3619 if (PHINode *PN = dyn_cast<PHINode>(I))
3620 ConstantEvolutionLoopExitValue.erase(PN);
3623 PushDefUseChildren(I, Worklist);
3627 /// forgetValue - This method should be called by the client when it has
3628 /// changed a value in a way that may effect its value, or which may
3629 /// disconnect it from a def-use chain linking it to a loop.
3630 void ScalarEvolution::forgetValue(Value *V) {
3631 Instruction *I = dyn_cast<Instruction>(V);
3634 // Drop information about expressions based on loop-header PHIs.
3635 SmallVector<Instruction *, 16> Worklist;
3636 Worklist.push_back(I);
3638 SmallPtrSet<Instruction *, 8> Visited;
3639 while (!Worklist.empty()) {
3640 I = Worklist.pop_back_val();
3641 if (!Visited.insert(I)) continue;
3643 std::map<SCEVCallbackVH, const SCEV *>::iterator It =
3644 Scalars.find(static_cast<Value *>(I));
3645 if (It != Scalars.end()) {
3646 ValuesAtScopes.erase(It->second);
3648 if (PHINode *PN = dyn_cast<PHINode>(I))
3649 ConstantEvolutionLoopExitValue.erase(PN);
3652 PushDefUseChildren(I, Worklist);
3656 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
3657 /// of the specified loop will execute.
3658 ScalarEvolution::BackedgeTakenInfo
3659 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
3660 SmallVector<BasicBlock *, 8> ExitingBlocks;
3661 L->getExitingBlocks(ExitingBlocks);
3663 // Examine all exits and pick the most conservative values.
3664 const SCEV *BECount = getCouldNotCompute();
3665 const SCEV *MaxBECount = getCouldNotCompute();
3666 bool CouldNotComputeBECount = false;
3667 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
3668 BackedgeTakenInfo NewBTI =
3669 ComputeBackedgeTakenCountFromExit(L, ExitingBlocks[i]);
3671 if (NewBTI.Exact == getCouldNotCompute()) {
3672 // We couldn't compute an exact value for this exit, so
3673 // we won't be able to compute an exact value for the loop.
3674 CouldNotComputeBECount = true;
3675 BECount = getCouldNotCompute();
3676 } else if (!CouldNotComputeBECount) {
3677 if (BECount == getCouldNotCompute())
3678 BECount = NewBTI.Exact;
3680 BECount = getUMinFromMismatchedTypes(BECount, NewBTI.Exact);
3682 if (MaxBECount == getCouldNotCompute())
3683 MaxBECount = NewBTI.Max;
3684 else if (NewBTI.Max != getCouldNotCompute())
3685 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, NewBTI.Max);
3688 return BackedgeTakenInfo(BECount, MaxBECount);
3691 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the backedge
3692 /// of the specified loop will execute if it exits via the specified block.
3693 ScalarEvolution::BackedgeTakenInfo
3694 ScalarEvolution::ComputeBackedgeTakenCountFromExit(const Loop *L,
3695 BasicBlock *ExitingBlock) {
3697 // Okay, we've chosen an exiting block. See what condition causes us to
3698 // exit at this block.
3700 // FIXME: we should be able to handle switch instructions (with a single exit)
3701 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
3702 if (ExitBr == 0) return getCouldNotCompute();
3703 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
3705 // At this point, we know we have a conditional branch that determines whether
3706 // the loop is exited. However, we don't know if the branch is executed each
3707 // time through the loop. If not, then the execution count of the branch will
3708 // not be equal to the trip count of the loop.
3710 // Currently we check for this by checking to see if the Exit branch goes to
3711 // the loop header. If so, we know it will always execute the same number of
3712 // times as the loop. We also handle the case where the exit block *is* the
3713 // loop header. This is common for un-rotated loops.
3715 // If both of those tests fail, walk up the unique predecessor chain to the
3716 // header, stopping if there is an edge that doesn't exit the loop. If the
3717 // header is reached, the execution count of the branch will be equal to the
3718 // trip count of the loop.
3720 // More extensive analysis could be done to handle more cases here.
3722 if (ExitBr->getSuccessor(0) != L->getHeader() &&
3723 ExitBr->getSuccessor(1) != L->getHeader() &&
3724 ExitBr->getParent() != L->getHeader()) {
3725 // The simple checks failed, try climbing the unique predecessor chain
3726 // up to the header.
3728 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
3729 BasicBlock *Pred = BB->getUniquePredecessor();
3731 return getCouldNotCompute();
3732 TerminatorInst *PredTerm = Pred->getTerminator();
3733 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
3734 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
3737 // If the predecessor has a successor that isn't BB and isn't
3738 // outside the loop, assume the worst.
3739 if (L->contains(PredSucc))
3740 return getCouldNotCompute();
3742 if (Pred == L->getHeader()) {
3749 return getCouldNotCompute();
3752 // Proceed to the next level to examine the exit condition expression.
3753 return ComputeBackedgeTakenCountFromExitCond(L, ExitBr->getCondition(),
3754 ExitBr->getSuccessor(0),
3755 ExitBr->getSuccessor(1));
3758 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
3759 /// backedge of the specified loop will execute if its exit condition
3760 /// were a conditional branch of ExitCond, TBB, and FBB.
3761 ScalarEvolution::BackedgeTakenInfo
3762 ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
3766 // Check if the controlling expression for this loop is an And or Or.
3767 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
3768 if (BO->getOpcode() == Instruction::And) {
3769 // Recurse on the operands of the and.
3770 BackedgeTakenInfo BTI0 =
3771 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3772 BackedgeTakenInfo BTI1 =
3773 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3774 const SCEV *BECount = getCouldNotCompute();
3775 const SCEV *MaxBECount = getCouldNotCompute();
3776 if (L->contains(TBB)) {
3777 // Both conditions must be true for the loop to continue executing.
3778 // Choose the less conservative count.
3779 if (BTI0.Exact == getCouldNotCompute() ||
3780 BTI1.Exact == getCouldNotCompute())
3781 BECount = getCouldNotCompute();
3783 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3784 if (BTI0.Max == getCouldNotCompute())
3785 MaxBECount = BTI1.Max;
3786 else if (BTI1.Max == getCouldNotCompute())
3787 MaxBECount = BTI0.Max;
3789 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3791 // Both conditions must be true for the loop to exit.
3792 assert(L->contains(FBB) && "Loop block has no successor in loop!");
3793 if (BTI0.Exact != getCouldNotCompute() &&
3794 BTI1.Exact != getCouldNotCompute())
3795 BECount = getUMaxFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3796 if (BTI0.Max != getCouldNotCompute() &&
3797 BTI1.Max != getCouldNotCompute())
3798 MaxBECount = getUMaxFromMismatchedTypes(BTI0.Max, BTI1.Max);
3801 return BackedgeTakenInfo(BECount, MaxBECount);
3803 if (BO->getOpcode() == Instruction::Or) {
3804 // Recurse on the operands of the or.
3805 BackedgeTakenInfo BTI0 =
3806 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3807 BackedgeTakenInfo BTI1 =
3808 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3809 const SCEV *BECount = getCouldNotCompute();
3810 const SCEV *MaxBECount = getCouldNotCompute();
3811 if (L->contains(FBB)) {
3812 // Both conditions must be false for the loop to continue executing.
3813 // Choose the less conservative count.
3814 if (BTI0.Exact == getCouldNotCompute() ||
3815 BTI1.Exact == getCouldNotCompute())
3816 BECount = getCouldNotCompute();
3818 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3819 if (BTI0.Max == getCouldNotCompute())
3820 MaxBECount = BTI1.Max;
3821 else if (BTI1.Max == getCouldNotCompute())
3822 MaxBECount = BTI0.Max;
3824 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3826 // Both conditions must be false for the loop to exit.
3827 assert(L->contains(TBB) && "Loop block has no successor in loop!");
3828 if (BTI0.Exact != getCouldNotCompute() &&
3829 BTI1.Exact != getCouldNotCompute())
3830 BECount = getUMaxFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3831 if (BTI0.Max != getCouldNotCompute() &&
3832 BTI1.Max != getCouldNotCompute())
3833 MaxBECount = getUMaxFromMismatchedTypes(BTI0.Max, BTI1.Max);
3836 return BackedgeTakenInfo(BECount, MaxBECount);
3840 // With an icmp, it may be feasible to compute an exact backedge-taken count.
3841 // Proceed to the next level to examine the icmp.
3842 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
3843 return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
3845 // Check for a constant condition. These are normally stripped out by
3846 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
3847 // preserve the CFG and is temporarily leaving constant conditions
3849 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
3850 if (L->contains(FBB) == !CI->getZExtValue())
3851 // The backedge is always taken.
3852 return getCouldNotCompute();
3854 // The backedge is never taken.
3855 return getConstant(CI->getType(), 0);
3858 // If it's not an integer or pointer comparison then compute it the hard way.
3859 return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
3862 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of times the
3863 /// backedge of the specified loop will execute if its exit condition
3864 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
3865 ScalarEvolution::BackedgeTakenInfo
3866 ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
3871 // If the condition was exit on true, convert the condition to exit on false
3872 ICmpInst::Predicate Cond;
3873 if (!L->contains(FBB))
3874 Cond = ExitCond->getPredicate();
3876 Cond = ExitCond->getInversePredicate();
3878 // Handle common loops like: for (X = "string"; *X; ++X)
3879 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
3880 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
3881 BackedgeTakenInfo ItCnt =
3882 ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
3883 if (ItCnt.hasAnyInfo())
3887 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
3888 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
3890 // Try to evaluate any dependencies out of the loop.
3891 LHS = getSCEVAtScope(LHS, L);
3892 RHS = getSCEVAtScope(RHS, L);
3894 // At this point, we would like to compute how many iterations of the
3895 // loop the predicate will return true for these inputs.
3896 if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) {
3897 // If there is a loop-invariant, force it into the RHS.
3898 std::swap(LHS, RHS);
3899 Cond = ICmpInst::getSwappedPredicate(Cond);
3902 // Simplify the operands before analyzing them.
3903 (void)SimplifyICmpOperands(Cond, LHS, RHS);
3905 // If we have a comparison of a chrec against a constant, try to use value
3906 // ranges to answer this query.
3907 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
3908 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
3909 if (AddRec->getLoop() == L) {
3910 // Form the constant range.
3911 ConstantRange CompRange(
3912 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
3914 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
3915 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
3919 case ICmpInst::ICMP_NE: { // while (X != Y)
3920 // Convert to: while (X-Y != 0)
3921 BackedgeTakenInfo BTI = HowFarToZero(getMinusSCEV(LHS, RHS), L);
3922 if (BTI.hasAnyInfo()) return BTI;
3925 case ICmpInst::ICMP_EQ: { // while (X == Y)
3926 // Convert to: while (X-Y == 0)
3927 BackedgeTakenInfo BTI = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
3928 if (BTI.hasAnyInfo()) return BTI;
3931 case ICmpInst::ICMP_SLT: {
3932 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, true);
3933 if (BTI.hasAnyInfo()) return BTI;
3936 case ICmpInst::ICMP_SGT: {
3937 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
3938 getNotSCEV(RHS), L, true);
3939 if (BTI.hasAnyInfo()) return BTI;
3942 case ICmpInst::ICMP_ULT: {
3943 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, false);
3944 if (BTI.hasAnyInfo()) return BTI;
3947 case ICmpInst::ICMP_UGT: {
3948 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
3949 getNotSCEV(RHS), L, false);
3950 if (BTI.hasAnyInfo()) return BTI;
3955 dbgs() << "ComputeBackedgeTakenCount ";
3956 if (ExitCond->getOperand(0)->getType()->isUnsigned())
3957 dbgs() << "[unsigned] ";
3958 dbgs() << *LHS << " "
3959 << Instruction::getOpcodeName(Instruction::ICmp)
3960 << " " << *RHS << "\n";
3965 ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
3968 static ConstantInt *
3969 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
3970 ScalarEvolution &SE) {
3971 const SCEV *InVal = SE.getConstant(C);
3972 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
3973 assert(isa<SCEVConstant>(Val) &&
3974 "Evaluation of SCEV at constant didn't fold correctly?");
3975 return cast<SCEVConstant>(Val)->getValue();
3978 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
3979 /// and a GEP expression (missing the pointer index) indexing into it, return
3980 /// the addressed element of the initializer or null if the index expression is
3983 GetAddressedElementFromGlobal(GlobalVariable *GV,
3984 const std::vector<ConstantInt*> &Indices) {
3985 Constant *Init = GV->getInitializer();
3986 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
3987 uint64_t Idx = Indices[i]->getZExtValue();
3988 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
3989 assert(Idx < CS->getNumOperands() && "Bad struct index!");
3990 Init = cast<Constant>(CS->getOperand(Idx));
3991 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
3992 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
3993 Init = cast<Constant>(CA->getOperand(Idx));
3994 } else if (isa<ConstantAggregateZero>(Init)) {
3995 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
3996 assert(Idx < STy->getNumElements() && "Bad struct index!");
3997 Init = Constant::getNullValue(STy->getElementType(Idx));
3998 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
3999 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4000 Init = Constant::getNullValue(ATy->getElementType());
4002 llvm_unreachable("Unknown constant aggregate type!");
4006 return 0; // Unknown initializer type
4012 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
4013 /// 'icmp op load X, cst', try to see if we can compute the backedge
4014 /// execution count.
4015 ScalarEvolution::BackedgeTakenInfo
4016 ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
4020 ICmpInst::Predicate predicate) {
4021 if (LI->isVolatile()) return getCouldNotCompute();
4023 // Check to see if the loaded pointer is a getelementptr of a global.
4024 // TODO: Use SCEV instead of manually grubbing with GEPs.
4025 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4026 if (!GEP) return getCouldNotCompute();
4028 // Make sure that it is really a constant global we are gepping, with an
4029 // initializer, and make sure the first IDX is really 0.
4030 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4031 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4032 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4033 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4034 return getCouldNotCompute();
4036 // Okay, we allow one non-constant index into the GEP instruction.
4038 std::vector<ConstantInt*> Indexes;
4039 unsigned VarIdxNum = 0;
4040 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4041 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4042 Indexes.push_back(CI);
4043 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4044 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4045 VarIdx = GEP->getOperand(i);
4047 Indexes.push_back(0);
4050 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4051 // Check to see if X is a loop variant variable value now.
4052 const SCEV *Idx = getSCEV(VarIdx);
4053 Idx = getSCEVAtScope(Idx, L);
4055 // We can only recognize very limited forms of loop index expressions, in
4056 // particular, only affine AddRec's like {C1,+,C2}.
4057 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4058 if (!IdxExpr || !IdxExpr->isAffine() || IdxExpr->isLoopInvariant(L) ||
4059 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4060 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4061 return getCouldNotCompute();
4063 unsigned MaxSteps = MaxBruteForceIterations;
4064 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4065 ConstantInt *ItCst = ConstantInt::get(
4066 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4067 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4069 // Form the GEP offset.
4070 Indexes[VarIdxNum] = Val;
4072 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4073 if (Result == 0) break; // Cannot compute!
4075 // Evaluate the condition for this iteration.
4076 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4077 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4078 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4080 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4081 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4084 ++NumArrayLenItCounts;
4085 return getConstant(ItCst); // Found terminating iteration!
4088 return getCouldNotCompute();
4092 /// CanConstantFold - Return true if we can constant fold an instruction of the
4093 /// specified type, assuming that all operands were constants.
4094 static bool CanConstantFold(const Instruction *I) {
4095 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4096 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
4099 if (const CallInst *CI = dyn_cast<CallInst>(I))
4100 if (const Function *F = CI->getCalledFunction())
4101 return canConstantFoldCallTo(F);
4105 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4106 /// in the loop that V is derived from. We allow arbitrary operations along the
4107 /// way, but the operands of an operation must either be constants or a value
4108 /// derived from a constant PHI. If this expression does not fit with these
4109 /// constraints, return null.
4110 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4111 // If this is not an instruction, or if this is an instruction outside of the
4112 // loop, it can't be derived from a loop PHI.
4113 Instruction *I = dyn_cast<Instruction>(V);
4114 if (I == 0 || !L->contains(I)) return 0;
4116 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4117 if (L->getHeader() == I->getParent())
4120 // We don't currently keep track of the control flow needed to evaluate
4121 // PHIs, so we cannot handle PHIs inside of loops.
4125 // If we won't be able to constant fold this expression even if the operands
4126 // are constants, return early.
4127 if (!CanConstantFold(I)) return 0;
4129 // Otherwise, we can evaluate this instruction if all of its operands are
4130 // constant or derived from a PHI node themselves.
4132 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4133 if (!isa<Constant>(I->getOperand(Op))) {
4134 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4135 if (P == 0) return 0; // Not evolving from PHI
4139 return 0; // Evolving from multiple different PHIs.
4142 // This is a expression evolving from a constant PHI!
4146 /// EvaluateExpression - Given an expression that passes the
4147 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4148 /// in the loop has the value PHIVal. If we can't fold this expression for some
4149 /// reason, return null.
4150 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4151 const TargetData *TD) {
4152 if (isa<PHINode>(V)) return PHIVal;
4153 if (Constant *C = dyn_cast<Constant>(V)) return C;
4154 Instruction *I = cast<Instruction>(V);
4156 std::vector<Constant*> Operands(I->getNumOperands());
4158 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4159 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4160 if (Operands[i] == 0) return 0;
4163 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4164 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4166 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4167 &Operands[0], Operands.size(), TD);
4170 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4171 /// in the header of its containing loop, we know the loop executes a
4172 /// constant number of times, and the PHI node is just a recurrence
4173 /// involving constants, fold it.
4175 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4178 std::map<PHINode*, Constant*>::iterator I =
4179 ConstantEvolutionLoopExitValue.find(PN);
4180 if (I != ConstantEvolutionLoopExitValue.end())
4183 if (BEs.ugt(MaxBruteForceIterations))
4184 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4186 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4188 // Since the loop is canonicalized, the PHI node must have two entries. One
4189 // entry must be a constant (coming in from outside of the loop), and the
4190 // second must be derived from the same PHI.
4191 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4192 Constant *StartCST =
4193 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4195 return RetVal = 0; // Must be a constant.
4197 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4198 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4199 !isa<Constant>(BEValue))
4200 return RetVal = 0; // Not derived from same PHI.
4202 // Execute the loop symbolically to determine the exit value.
4203 if (BEs.getActiveBits() >= 32)
4204 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4206 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4207 unsigned IterationNum = 0;
4208 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4209 if (IterationNum == NumIterations)
4210 return RetVal = PHIVal; // Got exit value!
4212 // Compute the value of the PHI node for the next iteration.
4213 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4214 if (NextPHI == PHIVal)
4215 return RetVal = NextPHI; // Stopped evolving!
4217 return 0; // Couldn't evaluate!
4222 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute a
4223 /// constant number of times (the condition evolves only from constants),
4224 /// try to evaluate a few iterations of the loop until we get the exit
4225 /// condition gets a value of ExitWhen (true or false). If we cannot
4226 /// evaluate the trip count of the loop, return getCouldNotCompute().
4228 ScalarEvolution::ComputeBackedgeTakenCountExhaustively(const Loop *L,
4231 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4232 if (PN == 0) return getCouldNotCompute();
4234 // If the loop is canonicalized, the PHI will have exactly two entries.
4235 // That's the only form we support here.
4236 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4238 // One entry must be a constant (coming in from outside of the loop), and the
4239 // second must be derived from the same PHI.
4240 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4241 Constant *StartCST =
4242 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4243 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4245 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4246 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4247 !isa<Constant>(BEValue))
4248 return getCouldNotCompute(); // Not derived from same PHI.
4250 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4251 // the loop symbolically to determine when the condition gets a value of
4253 unsigned IterationNum = 0;
4254 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4255 for (Constant *PHIVal = StartCST;
4256 IterationNum != MaxIterations; ++IterationNum) {
4257 ConstantInt *CondVal =
4258 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4260 // Couldn't symbolically evaluate.
4261 if (!CondVal) return getCouldNotCompute();
4263 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4264 ++NumBruteForceTripCountsComputed;
4265 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4268 // Compute the value of the PHI node for the next iteration.
4269 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4270 if (NextPHI == 0 || NextPHI == PHIVal)
4271 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4275 // Too many iterations were needed to evaluate.
4276 return getCouldNotCompute();
4279 /// getSCEVAtScope - Return a SCEV expression for the specified value
4280 /// at the specified scope in the program. The L value specifies a loop
4281 /// nest to evaluate the expression at, where null is the top-level or a
4282 /// specified loop is immediately inside of the loop.
4284 /// This method can be used to compute the exit value for a variable defined
4285 /// in a loop by querying what the value will hold in the parent loop.
4287 /// In the case that a relevant loop exit value cannot be computed, the
4288 /// original value V is returned.
4289 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4290 // Check to see if we've folded this expression at this loop before.
4291 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4292 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4293 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4295 return Pair.first->second ? Pair.first->second : V;
4297 // Otherwise compute it.
4298 const SCEV *C = computeSCEVAtScope(V, L);
4299 ValuesAtScopes[V][L] = C;
4303 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4304 if (isa<SCEVConstant>(V)) return V;
4306 // If this instruction is evolved from a constant-evolving PHI, compute the
4307 // exit value from the loop without using SCEVs.
4308 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4309 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4310 const Loop *LI = (*this->LI)[I->getParent()];
4311 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4312 if (PHINode *PN = dyn_cast<PHINode>(I))
4313 if (PN->getParent() == LI->getHeader()) {
4314 // Okay, there is no closed form solution for the PHI node. Check
4315 // to see if the loop that contains it has a known backedge-taken
4316 // count. If so, we may be able to force computation of the exit
4318 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4319 if (const SCEVConstant *BTCC =
4320 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4321 // Okay, we know how many times the containing loop executes. If
4322 // this is a constant evolving PHI node, get the final value at
4323 // the specified iteration number.
4324 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4325 BTCC->getValue()->getValue(),
4327 if (RV) return getSCEV(RV);
4331 // Okay, this is an expression that we cannot symbolically evaluate
4332 // into a SCEV. Check to see if it's possible to symbolically evaluate
4333 // the arguments into constants, and if so, try to constant propagate the
4334 // result. This is particularly useful for computing loop exit values.
4335 if (CanConstantFold(I)) {
4336 std::vector<Constant*> Operands;
4337 Operands.reserve(I->getNumOperands());
4338 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4339 Value *Op = I->getOperand(i);
4340 if (Constant *C = dyn_cast<Constant>(Op)) {
4341 Operands.push_back(C);
4343 // If any of the operands is non-constant and if they are
4344 // non-integer and non-pointer, don't even try to analyze them
4345 // with scev techniques.
4346 if (!isSCEVable(Op->getType()))
4349 const SCEV *OpV = getSCEVAtScope(Op, L);
4350 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV)) {
4351 Constant *C = SC->getValue();
4352 if (C->getType() != Op->getType())
4353 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4357 Operands.push_back(C);
4358 } else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV)) {
4359 if (Constant *C = dyn_cast<Constant>(SU->getValue())) {
4360 if (C->getType() != Op->getType())
4362 ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4366 Operands.push_back(C);
4376 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4377 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4378 Operands[0], Operands[1], TD);
4380 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4381 &Operands[0], Operands.size(), TD);
4387 // This is some other type of SCEVUnknown, just return it.
4391 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4392 // Avoid performing the look-up in the common case where the specified
4393 // expression has no loop-variant portions.
4394 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4395 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4396 if (OpAtScope != Comm->getOperand(i)) {
4397 // Okay, at least one of these operands is loop variant but might be
4398 // foldable. Build a new instance of the folded commutative expression.
4399 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4400 Comm->op_begin()+i);
4401 NewOps.push_back(OpAtScope);
4403 for (++i; i != e; ++i) {
4404 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4405 NewOps.push_back(OpAtScope);
4407 if (isa<SCEVAddExpr>(Comm))
4408 return getAddExpr(NewOps);
4409 if (isa<SCEVMulExpr>(Comm))
4410 return getMulExpr(NewOps);
4411 if (isa<SCEVSMaxExpr>(Comm))
4412 return getSMaxExpr(NewOps);
4413 if (isa<SCEVUMaxExpr>(Comm))
4414 return getUMaxExpr(NewOps);
4415 llvm_unreachable("Unknown commutative SCEV type!");
4418 // If we got here, all operands are loop invariant.
4422 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4423 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4424 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4425 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4426 return Div; // must be loop invariant
4427 return getUDivExpr(LHS, RHS);
4430 // If this is a loop recurrence for a loop that does not contain L, then we
4431 // are dealing with the final value computed by the loop.
4432 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4433 if (!L || !AddRec->getLoop()->contains(L)) {
4434 // To evaluate this recurrence, we need to know how many times the AddRec
4435 // loop iterates. Compute this now.
4436 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4437 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4439 // Then, evaluate the AddRec.
4440 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4445 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4446 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4447 if (Op == Cast->getOperand())
4448 return Cast; // must be loop invariant
4449 return getZeroExtendExpr(Op, Cast->getType());
4452 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4453 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4454 if (Op == Cast->getOperand())
4455 return Cast; // must be loop invariant
4456 return getSignExtendExpr(Op, Cast->getType());
4459 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4460 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4461 if (Op == Cast->getOperand())
4462 return Cast; // must be loop invariant
4463 return getTruncateExpr(Op, Cast->getType());
4466 llvm_unreachable("Unknown SCEV type!");
4470 /// getSCEVAtScope - This is a convenience function which does
4471 /// getSCEVAtScope(getSCEV(V), L).
4472 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4473 return getSCEVAtScope(getSCEV(V), L);
4476 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4477 /// following equation:
4479 /// A * X = B (mod N)
4481 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4482 /// A and B isn't important.
4484 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
4485 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4486 ScalarEvolution &SE) {
4487 uint32_t BW = A.getBitWidth();
4488 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4489 assert(A != 0 && "A must be non-zero.");
4493 // The gcd of A and N may have only one prime factor: 2. The number of
4494 // trailing zeros in A is its multiplicity
4495 uint32_t Mult2 = A.countTrailingZeros();
4498 // 2. Check if B is divisible by D.
4500 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4501 // is not less than multiplicity of this prime factor for D.
4502 if (B.countTrailingZeros() < Mult2)
4503 return SE.getCouldNotCompute();
4505 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4508 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4509 // bit width during computations.
4510 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4511 APInt Mod(BW + 1, 0);
4512 Mod.set(BW - Mult2); // Mod = N / D
4513 APInt I = AD.multiplicativeInverse(Mod);
4515 // 4. Compute the minimum unsigned root of the equation:
4516 // I * (B / D) mod (N / D)
4517 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4519 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4521 return SE.getConstant(Result.trunc(BW));
4524 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4525 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4526 /// might be the same) or two SCEVCouldNotCompute objects.
4528 static std::pair<const SCEV *,const SCEV *>
4529 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4530 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4531 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4532 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4533 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4535 // We currently can only solve this if the coefficients are constants.
4536 if (!LC || !MC || !NC) {
4537 const SCEV *CNC = SE.getCouldNotCompute();
4538 return std::make_pair(CNC, CNC);
4541 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4542 const APInt &L = LC->getValue()->getValue();
4543 const APInt &M = MC->getValue()->getValue();
4544 const APInt &N = NC->getValue()->getValue();
4545 APInt Two(BitWidth, 2);
4546 APInt Four(BitWidth, 4);
4549 using namespace APIntOps;
4551 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4552 // The B coefficient is M-N/2
4556 // The A coefficient is N/2
4557 APInt A(N.sdiv(Two));
4559 // Compute the B^2-4ac term.
4562 SqrtTerm -= Four * (A * C);
4564 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4565 // integer value or else APInt::sqrt() will assert.
4566 APInt SqrtVal(SqrtTerm.sqrt());
4568 // Compute the two solutions for the quadratic formula.
4569 // The divisions must be performed as signed divisions.
4571 APInt TwoA( A << 1 );
4572 if (TwoA.isMinValue()) {
4573 const SCEV *CNC = SE.getCouldNotCompute();
4574 return std::make_pair(CNC, CNC);
4577 LLVMContext &Context = SE.getContext();
4579 ConstantInt *Solution1 =
4580 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
4581 ConstantInt *Solution2 =
4582 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
4584 return std::make_pair(SE.getConstant(Solution1),
4585 SE.getConstant(Solution2));
4586 } // end APIntOps namespace
4589 /// HowFarToZero - Return the number of times a backedge comparing the specified
4590 /// value to zero will execute. If not computable, return CouldNotCompute.
4591 ScalarEvolution::BackedgeTakenInfo
4592 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
4593 // If the value is a constant
4594 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4595 // If the value is already zero, the branch will execute zero times.
4596 if (C->getValue()->isZero()) return C;
4597 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4600 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
4601 if (!AddRec || AddRec->getLoop() != L)
4602 return getCouldNotCompute();
4604 if (AddRec->isAffine()) {
4605 // If this is an affine expression, the execution count of this branch is
4606 // the minimum unsigned root of the following equation:
4608 // Start + Step*N = 0 (mod 2^BW)
4612 // Step*N = -Start (mod 2^BW)
4614 // where BW is the common bit width of Start and Step.
4616 // Get the initial value for the loop.
4617 const SCEV *Start = getSCEVAtScope(AddRec->getStart(),
4618 L->getParentLoop());
4619 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1),
4620 L->getParentLoop());
4622 if (const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step)) {
4623 // For now we handle only constant steps.
4625 // First, handle unitary steps.
4626 if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
4627 return getNegativeSCEV(Start); // N = -Start (as unsigned)
4628 if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
4629 return Start; // N = Start (as unsigned)
4631 // Then, try to solve the above equation provided that Start is constant.
4632 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
4633 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
4634 -StartC->getValue()->getValue(),
4637 } else if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
4638 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
4639 // the quadratic equation to solve it.
4640 std::pair<const SCEV *,const SCEV *> Roots = SolveQuadraticEquation(AddRec,
4642 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
4643 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
4646 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
4647 << " sol#2: " << *R2 << "\n";
4649 // Pick the smallest positive root value.
4650 if (ConstantInt *CB =
4651 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
4652 R1->getValue(), R2->getValue()))) {
4653 if (CB->getZExtValue() == false)
4654 std::swap(R1, R2); // R1 is the minimum root now.
4656 // We can only use this value if the chrec ends up with an exact zero
4657 // value at this index. When solving for "X*X != 5", for example, we
4658 // should not accept a root of 2.
4659 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
4661 return R1; // We found a quadratic root!
4666 return getCouldNotCompute();
4669 /// HowFarToNonZero - Return the number of times a backedge checking the
4670 /// specified value for nonzero will execute. If not computable, return
4672 ScalarEvolution::BackedgeTakenInfo
4673 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
4674 // Loops that look like: while (X == 0) are very strange indeed. We don't
4675 // handle them yet except for the trivial case. This could be expanded in the
4676 // future as needed.
4678 // If the value is a constant, check to see if it is known to be non-zero
4679 // already. If so, the backedge will execute zero times.
4680 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4681 if (!C->getValue()->isNullValue())
4682 return getConstant(C->getType(), 0);
4683 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4686 // We could implement others, but I really doubt anyone writes loops like
4687 // this, and if they did, they would already be constant folded.
4688 return getCouldNotCompute();
4691 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
4692 /// (which may not be an immediate predecessor) which has exactly one
4693 /// successor from which BB is reachable, or null if no such block is
4696 std::pair<BasicBlock *, BasicBlock *>
4697 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
4698 // If the block has a unique predecessor, then there is no path from the
4699 // predecessor to the block that does not go through the direct edge
4700 // from the predecessor to the block.
4701 if (BasicBlock *Pred = BB->getSinglePredecessor())
4702 return std::make_pair(Pred, BB);
4704 // A loop's header is defined to be a block that dominates the loop.
4705 // If the header has a unique predecessor outside the loop, it must be
4706 // a block that has exactly one successor that can reach the loop.
4707 if (Loop *L = LI->getLoopFor(BB))
4708 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
4710 return std::pair<BasicBlock *, BasicBlock *>();
4713 /// HasSameValue - SCEV structural equivalence is usually sufficient for
4714 /// testing whether two expressions are equal, however for the purposes of
4715 /// looking for a condition guarding a loop, it can be useful to be a little
4716 /// more general, since a front-end may have replicated the controlling
4719 static bool HasSameValue(const SCEV *A, const SCEV *B) {
4720 // Quick check to see if they are the same SCEV.
4721 if (A == B) return true;
4723 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
4724 // two different instructions with the same value. Check for this case.
4725 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
4726 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
4727 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
4728 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
4729 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
4732 // Otherwise assume they may have a different value.
4736 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
4737 /// predicate Pred. Return true iff any changes were made.
4739 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
4740 const SCEV *&LHS, const SCEV *&RHS) {
4741 bool Changed = false;
4743 // Canonicalize a constant to the right side.
4744 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
4745 // Check for both operands constant.
4746 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
4747 if (ConstantExpr::getICmp(Pred,
4749 RHSC->getValue())->isNullValue())
4750 goto trivially_false;
4752 goto trivially_true;
4754 // Otherwise swap the operands to put the constant on the right.
4755 std::swap(LHS, RHS);
4756 Pred = ICmpInst::getSwappedPredicate(Pred);
4760 // If we're comparing an addrec with a value which is loop-invariant in the
4761 // addrec's loop, put the addrec on the left. Also make a dominance check,
4762 // as both operands could be addrecs loop-invariant in each other's loop.
4763 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
4764 const Loop *L = AR->getLoop();
4765 if (LHS->isLoopInvariant(L) && LHS->properlyDominates(L->getHeader(), DT)) {
4766 std::swap(LHS, RHS);
4767 Pred = ICmpInst::getSwappedPredicate(Pred);
4772 // If there's a constant operand, canonicalize comparisons with boundary
4773 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
4774 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
4775 const APInt &RA = RC->getValue()->getValue();
4777 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
4778 case ICmpInst::ICMP_EQ:
4779 case ICmpInst::ICMP_NE:
4781 case ICmpInst::ICMP_UGE:
4782 if ((RA - 1).isMinValue()) {
4783 Pred = ICmpInst::ICMP_NE;
4784 RHS = getConstant(RA - 1);
4788 if (RA.isMaxValue()) {
4789 Pred = ICmpInst::ICMP_EQ;
4793 if (RA.isMinValue()) goto trivially_true;
4795 Pred = ICmpInst::ICMP_UGT;
4796 RHS = getConstant(RA - 1);
4799 case ICmpInst::ICMP_ULE:
4800 if ((RA + 1).isMaxValue()) {
4801 Pred = ICmpInst::ICMP_NE;
4802 RHS = getConstant(RA + 1);
4806 if (RA.isMinValue()) {
4807 Pred = ICmpInst::ICMP_EQ;
4811 if (RA.isMaxValue()) goto trivially_true;
4813 Pred = ICmpInst::ICMP_ULT;
4814 RHS = getConstant(RA + 1);
4817 case ICmpInst::ICMP_SGE:
4818 if ((RA - 1).isMinSignedValue()) {
4819 Pred = ICmpInst::ICMP_NE;
4820 RHS = getConstant(RA - 1);
4824 if (RA.isMaxSignedValue()) {
4825 Pred = ICmpInst::ICMP_EQ;
4829 if (RA.isMinSignedValue()) goto trivially_true;
4831 Pred = ICmpInst::ICMP_SGT;
4832 RHS = getConstant(RA - 1);
4835 case ICmpInst::ICMP_SLE:
4836 if ((RA + 1).isMaxSignedValue()) {
4837 Pred = ICmpInst::ICMP_NE;
4838 RHS = getConstant(RA + 1);
4842 if (RA.isMinSignedValue()) {
4843 Pred = ICmpInst::ICMP_EQ;
4847 if (RA.isMaxSignedValue()) goto trivially_true;
4849 Pred = ICmpInst::ICMP_SLT;
4850 RHS = getConstant(RA + 1);
4853 case ICmpInst::ICMP_UGT:
4854 if (RA.isMinValue()) {
4855 Pred = ICmpInst::ICMP_NE;
4859 if ((RA + 1).isMaxValue()) {
4860 Pred = ICmpInst::ICMP_EQ;
4861 RHS = getConstant(RA + 1);
4865 if (RA.isMaxValue()) goto trivially_false;
4867 case ICmpInst::ICMP_ULT:
4868 if (RA.isMaxValue()) {
4869 Pred = ICmpInst::ICMP_NE;
4873 if ((RA - 1).isMinValue()) {
4874 Pred = ICmpInst::ICMP_EQ;
4875 RHS = getConstant(RA - 1);
4879 if (RA.isMinValue()) goto trivially_false;
4881 case ICmpInst::ICMP_SGT:
4882 if (RA.isMinSignedValue()) {
4883 Pred = ICmpInst::ICMP_NE;
4887 if ((RA + 1).isMaxSignedValue()) {
4888 Pred = ICmpInst::ICMP_EQ;
4889 RHS = getConstant(RA + 1);
4893 if (RA.isMaxSignedValue()) goto trivially_false;
4895 case ICmpInst::ICMP_SLT:
4896 if (RA.isMaxSignedValue()) {
4897 Pred = ICmpInst::ICMP_NE;
4901 if ((RA - 1).isMinSignedValue()) {
4902 Pred = ICmpInst::ICMP_EQ;
4903 RHS = getConstant(RA - 1);
4907 if (RA.isMinSignedValue()) goto trivially_false;
4912 // Check for obvious equality.
4913 if (HasSameValue(LHS, RHS)) {
4914 if (ICmpInst::isTrueWhenEqual(Pred))
4915 goto trivially_true;
4916 if (ICmpInst::isFalseWhenEqual(Pred))
4917 goto trivially_false;
4920 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
4921 // adding or subtracting 1 from one of the operands.
4923 case ICmpInst::ICMP_SLE:
4924 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
4925 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
4926 /*HasNUW=*/false, /*HasNSW=*/true);
4927 Pred = ICmpInst::ICMP_SLT;
4929 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
4930 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
4931 /*HasNUW=*/false, /*HasNSW=*/true);
4932 Pred = ICmpInst::ICMP_SLT;
4936 case ICmpInst::ICMP_SGE:
4937 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
4938 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
4939 /*HasNUW=*/false, /*HasNSW=*/true);
4940 Pred = ICmpInst::ICMP_SGT;
4942 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
4943 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
4944 /*HasNUW=*/false, /*HasNSW=*/true);
4945 Pred = ICmpInst::ICMP_SGT;
4949 case ICmpInst::ICMP_ULE:
4950 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
4951 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
4952 /*HasNUW=*/true, /*HasNSW=*/false);
4953 Pred = ICmpInst::ICMP_ULT;
4955 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
4956 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
4957 /*HasNUW=*/true, /*HasNSW=*/false);
4958 Pred = ICmpInst::ICMP_ULT;
4962 case ICmpInst::ICMP_UGE:
4963 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
4964 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
4965 /*HasNUW=*/true, /*HasNSW=*/false);
4966 Pred = ICmpInst::ICMP_UGT;
4968 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
4969 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
4970 /*HasNUW=*/true, /*HasNSW=*/false);
4971 Pred = ICmpInst::ICMP_UGT;
4979 // TODO: More simplifications are possible here.
4985 LHS = RHS = getConstant(Type::getInt1Ty(getContext()), 0);
4986 Pred = ICmpInst::ICMP_EQ;
4991 LHS = RHS = getConstant(Type::getInt1Ty(getContext()), 0);
4992 Pred = ICmpInst::ICMP_NE;
4996 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
4997 return getSignedRange(S).getSignedMax().isNegative();
5000 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5001 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5004 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5005 return !getSignedRange(S).getSignedMin().isNegative();
5008 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5009 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5012 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5013 return isKnownNegative(S) || isKnownPositive(S);
5016 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5017 const SCEV *LHS, const SCEV *RHS) {
5018 // Canonicalize the inputs first.
5019 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5021 // If LHS or RHS is an addrec, check to see if the condition is true in
5022 // every iteration of the loop.
5023 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5024 if (isLoopEntryGuardedByCond(
5025 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5026 isLoopBackedgeGuardedByCond(
5027 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5029 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5030 if (isLoopEntryGuardedByCond(
5031 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5032 isLoopBackedgeGuardedByCond(
5033 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5036 // Otherwise see what can be done with known constant ranges.
5037 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5041 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5042 const SCEV *LHS, const SCEV *RHS) {
5043 if (HasSameValue(LHS, RHS))
5044 return ICmpInst::isTrueWhenEqual(Pred);
5046 // This code is split out from isKnownPredicate because it is called from
5047 // within isLoopEntryGuardedByCond.
5050 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5052 case ICmpInst::ICMP_SGT:
5053 Pred = ICmpInst::ICMP_SLT;
5054 std::swap(LHS, RHS);
5055 case ICmpInst::ICMP_SLT: {
5056 ConstantRange LHSRange = getSignedRange(LHS);
5057 ConstantRange RHSRange = getSignedRange(RHS);
5058 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5060 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5064 case ICmpInst::ICMP_SGE:
5065 Pred = ICmpInst::ICMP_SLE;
5066 std::swap(LHS, RHS);
5067 case ICmpInst::ICMP_SLE: {
5068 ConstantRange LHSRange = getSignedRange(LHS);
5069 ConstantRange RHSRange = getSignedRange(RHS);
5070 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5072 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5076 case ICmpInst::ICMP_UGT:
5077 Pred = ICmpInst::ICMP_ULT;
5078 std::swap(LHS, RHS);
5079 case ICmpInst::ICMP_ULT: {
5080 ConstantRange LHSRange = getUnsignedRange(LHS);
5081 ConstantRange RHSRange = getUnsignedRange(RHS);
5082 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5084 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5088 case ICmpInst::ICMP_UGE:
5089 Pred = ICmpInst::ICMP_ULE;
5090 std::swap(LHS, RHS);
5091 case ICmpInst::ICMP_ULE: {
5092 ConstantRange LHSRange = getUnsignedRange(LHS);
5093 ConstantRange RHSRange = getUnsignedRange(RHS);
5094 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5096 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5100 case ICmpInst::ICMP_NE: {
5101 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5103 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5106 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5107 if (isKnownNonZero(Diff))
5111 case ICmpInst::ICMP_EQ:
5112 // The check at the top of the function catches the case where
5113 // the values are known to be equal.
5119 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5120 /// protected by a conditional between LHS and RHS. This is used to
5121 /// to eliminate casts.
5123 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5124 ICmpInst::Predicate Pred,
5125 const SCEV *LHS, const SCEV *RHS) {
5126 // Interpret a null as meaning no loop, where there is obviously no guard
5127 // (interprocedural conditions notwithstanding).
5128 if (!L) return true;
5130 BasicBlock *Latch = L->getLoopLatch();
5134 BranchInst *LoopContinuePredicate =
5135 dyn_cast<BranchInst>(Latch->getTerminator());
5136 if (!LoopContinuePredicate ||
5137 LoopContinuePredicate->isUnconditional())
5140 return isImpliedCond(LoopContinuePredicate->getCondition(), Pred, LHS, RHS,
5141 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
5144 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
5145 /// by a conditional between LHS and RHS. This is used to help avoid max
5146 /// expressions in loop trip counts, and to eliminate casts.
5148 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
5149 ICmpInst::Predicate Pred,
5150 const SCEV *LHS, const SCEV *RHS) {
5151 // Interpret a null as meaning no loop, where there is obviously no guard
5152 // (interprocedural conditions notwithstanding).
5153 if (!L) return false;
5155 // Starting at the loop predecessor, climb up the predecessor chain, as long
5156 // as there are predecessors that can be found that have unique successors
5157 // leading to the original header.
5158 for (std::pair<BasicBlock *, BasicBlock *>
5159 Pair(L->getLoopPredecessor(), L->getHeader());
5161 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
5163 BranchInst *LoopEntryPredicate =
5164 dyn_cast<BranchInst>(Pair.first->getTerminator());
5165 if (!LoopEntryPredicate ||
5166 LoopEntryPredicate->isUnconditional())
5169 if (isImpliedCond(LoopEntryPredicate->getCondition(), Pred, LHS, RHS,
5170 LoopEntryPredicate->getSuccessor(0) != Pair.second))
5177 /// isImpliedCond - Test whether the condition described by Pred, LHS,
5178 /// and RHS is true whenever the given Cond value evaluates to true.
5179 bool ScalarEvolution::isImpliedCond(Value *CondValue,
5180 ICmpInst::Predicate Pred,
5181 const SCEV *LHS, const SCEV *RHS,
5183 // Recursively handle And and Or conditions.
5184 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CondValue)) {
5185 if (BO->getOpcode() == Instruction::And) {
5187 return isImpliedCond(BO->getOperand(0), Pred, LHS, RHS, Inverse) ||
5188 isImpliedCond(BO->getOperand(1), Pred, LHS, RHS, Inverse);
5189 } else if (BO->getOpcode() == Instruction::Or) {
5191 return isImpliedCond(BO->getOperand(0), Pred, LHS, RHS, Inverse) ||
5192 isImpliedCond(BO->getOperand(1), Pred, LHS, RHS, Inverse);
5196 ICmpInst *ICI = dyn_cast<ICmpInst>(CondValue);
5197 if (!ICI) return false;
5199 // Bail if the ICmp's operands' types are wider than the needed type
5200 // before attempting to call getSCEV on them. This avoids infinite
5201 // recursion, since the analysis of widening casts can require loop
5202 // exit condition information for overflow checking, which would
5204 if (getTypeSizeInBits(LHS->getType()) <
5205 getTypeSizeInBits(ICI->getOperand(0)->getType()))
5208 // Now that we found a conditional branch that dominates the loop, check to
5209 // see if it is the comparison we are looking for.
5210 ICmpInst::Predicate FoundPred;
5212 FoundPred = ICI->getInversePredicate();
5214 FoundPred = ICI->getPredicate();
5216 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
5217 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
5219 // Balance the types. The case where FoundLHS' type is wider than
5220 // LHS' type is checked for above.
5221 if (getTypeSizeInBits(LHS->getType()) >
5222 getTypeSizeInBits(FoundLHS->getType())) {
5223 if (CmpInst::isSigned(Pred)) {
5224 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
5225 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
5227 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
5228 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
5232 // Canonicalize the query to match the way instcombine will have
5233 // canonicalized the comparison.
5234 if (SimplifyICmpOperands(Pred, LHS, RHS))
5236 return CmpInst::isTrueWhenEqual(Pred);
5237 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
5238 if (FoundLHS == FoundRHS)
5239 return CmpInst::isFalseWhenEqual(Pred);
5241 // Check to see if we can make the LHS or RHS match.
5242 if (LHS == FoundRHS || RHS == FoundLHS) {
5243 if (isa<SCEVConstant>(RHS)) {
5244 std::swap(FoundLHS, FoundRHS);
5245 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
5247 std::swap(LHS, RHS);
5248 Pred = ICmpInst::getSwappedPredicate(Pred);
5252 // Check whether the found predicate is the same as the desired predicate.
5253 if (FoundPred == Pred)
5254 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
5256 // Check whether swapping the found predicate makes it the same as the
5257 // desired predicate.
5258 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
5259 if (isa<SCEVConstant>(RHS))
5260 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
5262 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
5263 RHS, LHS, FoundLHS, FoundRHS);
5266 // Check whether the actual condition is beyond sufficient.
5267 if (FoundPred == ICmpInst::ICMP_EQ)
5268 if (ICmpInst::isTrueWhenEqual(Pred))
5269 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
5271 if (Pred == ICmpInst::ICMP_NE)
5272 if (!ICmpInst::isTrueWhenEqual(FoundPred))
5273 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
5276 // Otherwise assume the worst.
5280 /// isImpliedCondOperands - Test whether the condition described by Pred,
5281 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
5282 /// and FoundRHS is true.
5283 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
5284 const SCEV *LHS, const SCEV *RHS,
5285 const SCEV *FoundLHS,
5286 const SCEV *FoundRHS) {
5287 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
5288 FoundLHS, FoundRHS) ||
5289 // ~x < ~y --> x > y
5290 isImpliedCondOperandsHelper(Pred, LHS, RHS,
5291 getNotSCEV(FoundRHS),
5292 getNotSCEV(FoundLHS));
5295 /// isImpliedCondOperandsHelper - Test whether the condition described by
5296 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
5297 /// FoundLHS, and FoundRHS is true.
5299 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
5300 const SCEV *LHS, const SCEV *RHS,
5301 const SCEV *FoundLHS,
5302 const SCEV *FoundRHS) {
5304 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5305 case ICmpInst::ICMP_EQ:
5306 case ICmpInst::ICMP_NE:
5307 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5310 case ICmpInst::ICMP_SLT:
5311 case ICmpInst::ICMP_SLE:
5312 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5313 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5316 case ICmpInst::ICMP_SGT:
5317 case ICmpInst::ICMP_SGE:
5318 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5319 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5322 case ICmpInst::ICMP_ULT:
5323 case ICmpInst::ICMP_ULE:
5324 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5325 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5328 case ICmpInst::ICMP_UGT:
5329 case ICmpInst::ICMP_UGE:
5330 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5331 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5339 /// getBECount - Subtract the end and start values and divide by the step,
5340 /// rounding up, to get the number of times the backedge is executed. Return
5341 /// CouldNotCompute if an intermediate computation overflows.
5342 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5346 assert(!isKnownNegative(Step) &&
5347 "This code doesn't handle negative strides yet!");
5349 const Type *Ty = Start->getType();
5350 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
5351 const SCEV *Diff = getMinusSCEV(End, Start);
5352 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5354 // Add an adjustment to the difference between End and Start so that
5355 // the division will effectively round up.
5356 const SCEV *Add = getAddExpr(Diff, RoundUp);
5359 // Check Add for unsigned overflow.
5360 // TODO: More sophisticated things could be done here.
5361 const Type *WideTy = IntegerType::get(getContext(),
5362 getTypeSizeInBits(Ty) + 1);
5363 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5364 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5365 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5366 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5367 return getCouldNotCompute();
5370 return getUDivExpr(Add, Step);
5373 /// HowManyLessThans - Return the number of times a backedge containing the
5374 /// specified less-than comparison will execute. If not computable, return
5375 /// CouldNotCompute.
5376 ScalarEvolution::BackedgeTakenInfo
5377 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5378 const Loop *L, bool isSigned) {
5379 // Only handle: "ADDREC < LoopInvariant".
5380 if (!RHS->isLoopInvariant(L)) return getCouldNotCompute();
5382 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5383 if (!AddRec || AddRec->getLoop() != L)
5384 return getCouldNotCompute();
5386 // Check to see if we have a flag which makes analysis easy.
5387 bool NoWrap = isSigned ? AddRec->hasNoSignedWrap() :
5388 AddRec->hasNoUnsignedWrap();
5390 if (AddRec->isAffine()) {
5391 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5392 const SCEV *Step = AddRec->getStepRecurrence(*this);
5395 return getCouldNotCompute();
5396 if (Step->isOne()) {
5397 // With unit stride, the iteration never steps past the limit value.
5398 } else if (isKnownPositive(Step)) {
5399 // Test whether a positive iteration can step past the limit
5400 // value and past the maximum value for its type in a single step.
5401 // Note that it's not sufficient to check NoWrap here, because even
5402 // though the value after a wrap is undefined, it's not undefined
5403 // behavior, so if wrap does occur, the loop could either terminate or
5404 // loop infinitely, but in either case, the loop is guaranteed to
5405 // iterate at least until the iteration where the wrapping occurs.
5406 const SCEV *One = getConstant(Step->getType(), 1);
5408 APInt Max = APInt::getSignedMaxValue(BitWidth);
5409 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5410 .slt(getSignedRange(RHS).getSignedMax()))
5411 return getCouldNotCompute();
5413 APInt Max = APInt::getMaxValue(BitWidth);
5414 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5415 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5416 return getCouldNotCompute();
5419 // TODO: Handle negative strides here and below.
5420 return getCouldNotCompute();
5422 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5423 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5424 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5425 // treat m-n as signed nor unsigned due to overflow possibility.
5427 // First, we get the value of the LHS in the first iteration: n
5428 const SCEV *Start = AddRec->getOperand(0);
5430 // Determine the minimum constant start value.
5431 const SCEV *MinStart = getConstant(isSigned ?
5432 getSignedRange(Start).getSignedMin() :
5433 getUnsignedRange(Start).getUnsignedMin());
5435 // If we know that the condition is true in order to enter the loop,
5436 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5437 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5438 // the division must round up.
5439 const SCEV *End = RHS;
5440 if (!isLoopEntryGuardedByCond(L,
5441 isSigned ? ICmpInst::ICMP_SLT :
5443 getMinusSCEV(Start, Step), RHS))
5444 End = isSigned ? getSMaxExpr(RHS, Start)
5445 : getUMaxExpr(RHS, Start);
5447 // Determine the maximum constant end value.
5448 const SCEV *MaxEnd = getConstant(isSigned ?
5449 getSignedRange(End).getSignedMax() :
5450 getUnsignedRange(End).getUnsignedMax());
5452 // If MaxEnd is within a step of the maximum integer value in its type,
5453 // adjust it down to the minimum value which would produce the same effect.
5454 // This allows the subsequent ceiling division of (N+(step-1))/step to
5455 // compute the correct value.
5456 const SCEV *StepMinusOne = getMinusSCEV(Step,
5457 getConstant(Step->getType(), 1));
5460 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5463 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5466 // Finally, we subtract these two values and divide, rounding up, to get
5467 // the number of times the backedge is executed.
5468 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5470 // The maximum backedge count is similar, except using the minimum start
5471 // value and the maximum end value.
5472 const SCEV *MaxBECount = getBECount(MinStart, MaxEnd, Step, NoWrap);
5474 return BackedgeTakenInfo(BECount, MaxBECount);
5477 return getCouldNotCompute();
5480 /// getNumIterationsInRange - Return the number of iterations of this loop that
5481 /// produce values in the specified constant range. Another way of looking at
5482 /// this is that it returns the first iteration number where the value is not in
5483 /// the condition, thus computing the exit count. If the iteration count can't
5484 /// be computed, an instance of SCEVCouldNotCompute is returned.
5485 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5486 ScalarEvolution &SE) const {
5487 if (Range.isFullSet()) // Infinite loop.
5488 return SE.getCouldNotCompute();
5490 // If the start is a non-zero constant, shift the range to simplify things.
5491 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5492 if (!SC->getValue()->isZero()) {
5493 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5494 Operands[0] = SE.getConstant(SC->getType(), 0);
5495 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop());
5496 if (const SCEVAddRecExpr *ShiftedAddRec =
5497 dyn_cast<SCEVAddRecExpr>(Shifted))
5498 return ShiftedAddRec->getNumIterationsInRange(
5499 Range.subtract(SC->getValue()->getValue()), SE);
5500 // This is strange and shouldn't happen.
5501 return SE.getCouldNotCompute();
5504 // The only time we can solve this is when we have all constant indices.
5505 // Otherwise, we cannot determine the overflow conditions.
5506 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5507 if (!isa<SCEVConstant>(getOperand(i)))
5508 return SE.getCouldNotCompute();
5511 // Okay at this point we know that all elements of the chrec are constants and
5512 // that the start element is zero.
5514 // First check to see if the range contains zero. If not, the first
5516 unsigned BitWidth = SE.getTypeSizeInBits(getType());
5517 if (!Range.contains(APInt(BitWidth, 0)))
5518 return SE.getConstant(getType(), 0);
5521 // If this is an affine expression then we have this situation:
5522 // Solve {0,+,A} in Range === Ax in Range
5524 // We know that zero is in the range. If A is positive then we know that
5525 // the upper value of the range must be the first possible exit value.
5526 // If A is negative then the lower of the range is the last possible loop
5527 // value. Also note that we already checked for a full range.
5528 APInt One(BitWidth,1);
5529 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
5530 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
5532 // The exit value should be (End+A)/A.
5533 APInt ExitVal = (End + A).udiv(A);
5534 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
5536 // Evaluate at the exit value. If we really did fall out of the valid
5537 // range, then we computed our trip count, otherwise wrap around or other
5538 // things must have happened.
5539 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
5540 if (Range.contains(Val->getValue()))
5541 return SE.getCouldNotCompute(); // Something strange happened
5543 // Ensure that the previous value is in the range. This is a sanity check.
5544 assert(Range.contains(
5545 EvaluateConstantChrecAtConstant(this,
5546 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
5547 "Linear scev computation is off in a bad way!");
5548 return SE.getConstant(ExitValue);
5549 } else if (isQuadratic()) {
5550 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
5551 // quadratic equation to solve it. To do this, we must frame our problem in
5552 // terms of figuring out when zero is crossed, instead of when
5553 // Range.getUpper() is crossed.
5554 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
5555 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
5556 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
5558 // Next, solve the constructed addrec
5559 std::pair<const SCEV *,const SCEV *> Roots =
5560 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
5561 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5562 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5564 // Pick the smallest positive root value.
5565 if (ConstantInt *CB =
5566 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
5567 R1->getValue(), R2->getValue()))) {
5568 if (CB->getZExtValue() == false)
5569 std::swap(R1, R2); // R1 is the minimum root now.
5571 // Make sure the root is not off by one. The returned iteration should
5572 // not be in the range, but the previous one should be. When solving
5573 // for "X*X < 5", for example, we should not return a root of 2.
5574 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
5577 if (Range.contains(R1Val->getValue())) {
5578 // The next iteration must be out of the range...
5579 ConstantInt *NextVal =
5580 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
5582 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5583 if (!Range.contains(R1Val->getValue()))
5584 return SE.getConstant(NextVal);
5585 return SE.getCouldNotCompute(); // Something strange happened
5588 // If R1 was not in the range, then it is a good return value. Make
5589 // sure that R1-1 WAS in the range though, just in case.
5590 ConstantInt *NextVal =
5591 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
5592 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5593 if (Range.contains(R1Val->getValue()))
5595 return SE.getCouldNotCompute(); // Something strange happened
5600 return SE.getCouldNotCompute();
5605 //===----------------------------------------------------------------------===//
5606 // SCEVCallbackVH Class Implementation
5607 //===----------------------------------------------------------------------===//
5609 void ScalarEvolution::SCEVCallbackVH::deleted() {
5610 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5611 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
5612 SE->ConstantEvolutionLoopExitValue.erase(PN);
5613 SE->Scalars.erase(getValPtr());
5614 // this now dangles!
5617 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *) {
5618 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5620 // Forget all the expressions associated with users of the old value,
5621 // so that future queries will recompute the expressions using the new
5623 SmallVector<User *, 16> Worklist;
5624 SmallPtrSet<User *, 8> Visited;
5625 Value *Old = getValPtr();
5626 bool DeleteOld = false;
5627 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
5629 Worklist.push_back(*UI);
5630 while (!Worklist.empty()) {
5631 User *U = Worklist.pop_back_val();
5632 // Deleting the Old value will cause this to dangle. Postpone
5633 // that until everything else is done.
5638 if (!Visited.insert(U))
5640 if (PHINode *PN = dyn_cast<PHINode>(U))
5641 SE->ConstantEvolutionLoopExitValue.erase(PN);
5642 SE->Scalars.erase(U);
5643 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
5645 Worklist.push_back(*UI);
5647 // Delete the Old value if it (indirectly) references itself.
5649 if (PHINode *PN = dyn_cast<PHINode>(Old))
5650 SE->ConstantEvolutionLoopExitValue.erase(PN);
5651 SE->Scalars.erase(Old);
5652 // this now dangles!
5657 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
5658 : CallbackVH(V), SE(se) {}
5660 //===----------------------------------------------------------------------===//
5661 // ScalarEvolution Class Implementation
5662 //===----------------------------------------------------------------------===//
5664 ScalarEvolution::ScalarEvolution()
5665 : FunctionPass(&ID) {
5668 bool ScalarEvolution::runOnFunction(Function &F) {
5670 LI = &getAnalysis<LoopInfo>();
5671 TD = getAnalysisIfAvailable<TargetData>();
5672 DT = &getAnalysis<DominatorTree>();
5676 void ScalarEvolution::releaseMemory() {
5678 BackedgeTakenCounts.clear();
5679 ConstantEvolutionLoopExitValue.clear();
5680 ValuesAtScopes.clear();
5681 UniqueSCEVs.clear();
5682 SCEVAllocator.Reset();
5685 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
5686 AU.setPreservesAll();
5687 AU.addRequiredTransitive<LoopInfo>();
5688 AU.addRequiredTransitive<DominatorTree>();
5691 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
5692 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
5695 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
5697 // Print all inner loops first
5698 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
5699 PrintLoopInfo(OS, SE, *I);
5702 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5705 SmallVector<BasicBlock *, 8> ExitBlocks;
5706 L->getExitBlocks(ExitBlocks);
5707 if (ExitBlocks.size() != 1)
5708 OS << "<multiple exits> ";
5710 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
5711 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
5713 OS << "Unpredictable backedge-taken count. ";
5718 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5721 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
5722 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
5724 OS << "Unpredictable max backedge-taken count. ";
5730 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
5731 // ScalarEvolution's implementation of the print method is to print
5732 // out SCEV values of all instructions that are interesting. Doing
5733 // this potentially causes it to create new SCEV objects though,
5734 // which technically conflicts with the const qualifier. This isn't
5735 // observable from outside the class though, so casting away the
5736 // const isn't dangerous.
5737 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
5739 OS << "Classifying expressions for: ";
5740 WriteAsOperand(OS, F, /*PrintType=*/false);
5742 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
5743 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
5746 const SCEV *SV = SE.getSCEV(&*I);
5749 const Loop *L = LI->getLoopFor((*I).getParent());
5751 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
5758 OS << "\t\t" "Exits: ";
5759 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
5760 if (!ExitValue->isLoopInvariant(L)) {
5761 OS << "<<Unknown>>";
5770 OS << "Determining loop execution counts for: ";
5771 WriteAsOperand(OS, F, /*PrintType=*/false);
5773 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
5774 PrintLoopInfo(OS, &SE, *I);