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/InstructionSimplify.h"
73 #include "llvm/Analysis/LoopInfo.h"
74 #include "llvm/Analysis/ValueTracking.h"
75 #include "llvm/Assembly/Writer.h"
76 #include "llvm/Target/TargetData.h"
77 #include "llvm/Support/CommandLine.h"
78 #include "llvm/Support/ConstantRange.h"
79 #include "llvm/Support/Debug.h"
80 #include "llvm/Support/ErrorHandling.h"
81 #include "llvm/Support/GetElementPtrTypeIterator.h"
82 #include "llvm/Support/InstIterator.h"
83 #include "llvm/Support/MathExtras.h"
84 #include "llvm/Support/raw_ostream.h"
85 #include "llvm/ADT/Statistic.h"
86 #include "llvm/ADT/STLExtras.h"
87 #include "llvm/ADT/SmallPtrSet.h"
91 STATISTIC(NumArrayLenItCounts,
92 "Number of trip counts computed with array length");
93 STATISTIC(NumTripCountsComputed,
94 "Number of loops with predictable loop counts");
95 STATISTIC(NumTripCountsNotComputed,
96 "Number of loops without predictable loop counts");
97 STATISTIC(NumBruteForceTripCountsComputed,
98 "Number of loops with trip counts computed by force");
100 static cl::opt<unsigned>
101 MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
102 cl::desc("Maximum number of iterations SCEV will "
103 "symbolically execute a constant "
107 INITIALIZE_PASS_BEGIN(ScalarEvolution, "scalar-evolution",
108 "Scalar Evolution Analysis", false, true)
109 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
110 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
111 INITIALIZE_PASS_END(ScalarEvolution, "scalar-evolution",
112 "Scalar Evolution Analysis", false, true)
113 char ScalarEvolution::ID = 0;
115 //===----------------------------------------------------------------------===//
116 // SCEV class definitions
117 //===----------------------------------------------------------------------===//
119 //===----------------------------------------------------------------------===//
120 // Implementation of the SCEV class.
123 void SCEV::dump() const {
128 void SCEV::print(raw_ostream &OS) const {
129 switch (getSCEVType()) {
131 WriteAsOperand(OS, cast<SCEVConstant>(this)->getValue(), false);
134 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
135 const SCEV *Op = Trunc->getOperand();
136 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
137 << *Trunc->getType() << ")";
141 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
142 const SCEV *Op = ZExt->getOperand();
143 OS << "(zext " << *Op->getType() << " " << *Op << " to "
144 << *ZExt->getType() << ")";
148 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
149 const SCEV *Op = SExt->getOperand();
150 OS << "(sext " << *Op->getType() << " " << *Op << " to "
151 << *SExt->getType() << ")";
155 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
156 OS << "{" << *AR->getOperand(0);
157 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
158 OS << ",+," << *AR->getOperand(i);
160 if (AR->hasNoUnsignedWrap())
162 if (AR->hasNoSignedWrap())
164 WriteAsOperand(OS, AR->getLoop()->getHeader(), /*PrintType=*/false);
172 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
173 const char *OpStr = 0;
174 switch (NAry->getSCEVType()) {
175 case scAddExpr: OpStr = " + "; break;
176 case scMulExpr: OpStr = " * "; break;
177 case scUMaxExpr: OpStr = " umax "; break;
178 case scSMaxExpr: OpStr = " smax "; break;
181 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
184 if (llvm::next(I) != E)
191 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
192 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
196 const SCEVUnknown *U = cast<SCEVUnknown>(this);
198 if (U->isSizeOf(AllocTy)) {
199 OS << "sizeof(" << *AllocTy << ")";
202 if (U->isAlignOf(AllocTy)) {
203 OS << "alignof(" << *AllocTy << ")";
209 if (U->isOffsetOf(CTy, FieldNo)) {
210 OS << "offsetof(" << *CTy << ", ";
211 WriteAsOperand(OS, FieldNo, false);
216 // Otherwise just print it normally.
217 WriteAsOperand(OS, U->getValue(), false);
220 case scCouldNotCompute:
221 OS << "***COULDNOTCOMPUTE***";
225 llvm_unreachable("Unknown SCEV kind!");
228 const Type *SCEV::getType() const {
229 switch (getSCEVType()) {
231 return cast<SCEVConstant>(this)->getType();
235 return cast<SCEVCastExpr>(this)->getType();
240 return cast<SCEVNAryExpr>(this)->getType();
242 return cast<SCEVAddExpr>(this)->getType();
244 return cast<SCEVUDivExpr>(this)->getType();
246 return cast<SCEVUnknown>(this)->getType();
247 case scCouldNotCompute:
248 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
252 llvm_unreachable("Unknown SCEV kind!");
256 bool SCEV::isZero() const {
257 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
258 return SC->getValue()->isZero();
262 bool SCEV::isOne() const {
263 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
264 return SC->getValue()->isOne();
268 bool SCEV::isAllOnesValue() const {
269 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
270 return SC->getValue()->isAllOnesValue();
274 SCEVCouldNotCompute::SCEVCouldNotCompute() :
275 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
277 bool SCEVCouldNotCompute::classof(const SCEV *S) {
278 return S->getSCEVType() == scCouldNotCompute;
281 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
283 ID.AddInteger(scConstant);
286 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
287 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
288 UniqueSCEVs.InsertNode(S, IP);
292 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
293 return getConstant(ConstantInt::get(getContext(), Val));
297 ScalarEvolution::getConstant(const Type *Ty, uint64_t V, bool isSigned) {
298 const IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
299 return getConstant(ConstantInt::get(ITy, V, isSigned));
302 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
303 unsigned SCEVTy, const SCEV *op, const Type *ty)
304 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
306 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
307 const SCEV *op, const Type *ty)
308 : SCEVCastExpr(ID, scTruncate, op, ty) {
309 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
310 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
311 "Cannot truncate non-integer value!");
314 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
315 const SCEV *op, const Type *ty)
316 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
317 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
318 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
319 "Cannot zero extend non-integer value!");
322 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
323 const SCEV *op, const Type *ty)
324 : SCEVCastExpr(ID, scSignExtend, op, ty) {
325 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
326 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
327 "Cannot sign extend non-integer value!");
330 void SCEVUnknown::deleted() {
331 // Clear this SCEVUnknown from various maps.
332 SE->forgetMemoizedResults(this);
334 // Remove this SCEVUnknown from the uniquing map.
335 SE->UniqueSCEVs.RemoveNode(this);
337 // Release the value.
341 void SCEVUnknown::allUsesReplacedWith(Value *New) {
342 // Clear this SCEVUnknown from various maps.
343 SE->forgetMemoizedResults(this);
345 // Remove this SCEVUnknown from the uniquing map.
346 SE->UniqueSCEVs.RemoveNode(this);
348 // Update this SCEVUnknown to point to the new value. This is needed
349 // because there may still be outstanding SCEVs which still point to
354 bool SCEVUnknown::isSizeOf(const Type *&AllocTy) const {
355 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
356 if (VCE->getOpcode() == Instruction::PtrToInt)
357 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
358 if (CE->getOpcode() == Instruction::GetElementPtr &&
359 CE->getOperand(0)->isNullValue() &&
360 CE->getNumOperands() == 2)
361 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
363 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
371 bool SCEVUnknown::isAlignOf(const Type *&AllocTy) const {
372 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
373 if (VCE->getOpcode() == Instruction::PtrToInt)
374 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
375 if (CE->getOpcode() == Instruction::GetElementPtr &&
376 CE->getOperand(0)->isNullValue()) {
378 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
379 if (const StructType *STy = dyn_cast<StructType>(Ty))
380 if (!STy->isPacked() &&
381 CE->getNumOperands() == 3 &&
382 CE->getOperand(1)->isNullValue()) {
383 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
385 STy->getNumElements() == 2 &&
386 STy->getElementType(0)->isIntegerTy(1)) {
387 AllocTy = STy->getElementType(1);
396 bool SCEVUnknown::isOffsetOf(const Type *&CTy, Constant *&FieldNo) const {
397 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
398 if (VCE->getOpcode() == Instruction::PtrToInt)
399 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
400 if (CE->getOpcode() == Instruction::GetElementPtr &&
401 CE->getNumOperands() == 3 &&
402 CE->getOperand(0)->isNullValue() &&
403 CE->getOperand(1)->isNullValue()) {
405 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
406 // Ignore vector types here so that ScalarEvolutionExpander doesn't
407 // emit getelementptrs that index into vectors.
408 if (Ty->isStructTy() || Ty->isArrayTy()) {
410 FieldNo = CE->getOperand(2);
418 //===----------------------------------------------------------------------===//
420 //===----------------------------------------------------------------------===//
423 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
424 /// than the complexity of the RHS. This comparator is used to canonicalize
426 class SCEVComplexityCompare {
427 const LoopInfo *const LI;
429 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
431 // Return true or false if LHS is less than, or at least RHS, respectively.
432 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
433 return compare(LHS, RHS) < 0;
436 // Return negative, zero, or positive, if LHS is less than, equal to, or
437 // greater than RHS, respectively. A three-way result allows recursive
438 // comparisons to be more efficient.
439 int compare(const SCEV *LHS, const SCEV *RHS) const {
440 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
444 // Primarily, sort the SCEVs by their getSCEVType().
445 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
447 return (int)LType - (int)RType;
449 // Aside from the getSCEVType() ordering, the particular ordering
450 // isn't very important except that it's beneficial to be consistent,
451 // so that (a + b) and (b + a) don't end up as different expressions.
454 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
455 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
457 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
458 // not as complete as it could be.
459 const Value *LV = LU->getValue(), *RV = RU->getValue();
461 // Order pointer values after integer values. This helps SCEVExpander
463 bool LIsPointer = LV->getType()->isPointerTy(),
464 RIsPointer = RV->getType()->isPointerTy();
465 if (LIsPointer != RIsPointer)
466 return (int)LIsPointer - (int)RIsPointer;
468 // Compare getValueID values.
469 unsigned LID = LV->getValueID(),
470 RID = RV->getValueID();
472 return (int)LID - (int)RID;
474 // Sort arguments by their position.
475 if (const Argument *LA = dyn_cast<Argument>(LV)) {
476 const Argument *RA = cast<Argument>(RV);
477 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
478 return (int)LArgNo - (int)RArgNo;
481 // For instructions, compare their loop depth, and their operand
482 // count. This is pretty loose.
483 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
484 const Instruction *RInst = cast<Instruction>(RV);
486 // Compare loop depths.
487 const BasicBlock *LParent = LInst->getParent(),
488 *RParent = RInst->getParent();
489 if (LParent != RParent) {
490 unsigned LDepth = LI->getLoopDepth(LParent),
491 RDepth = LI->getLoopDepth(RParent);
492 if (LDepth != RDepth)
493 return (int)LDepth - (int)RDepth;
496 // Compare the number of operands.
497 unsigned LNumOps = LInst->getNumOperands(),
498 RNumOps = RInst->getNumOperands();
499 return (int)LNumOps - (int)RNumOps;
506 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
507 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
509 // Compare constant values.
510 const APInt &LA = LC->getValue()->getValue();
511 const APInt &RA = RC->getValue()->getValue();
512 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
513 if (LBitWidth != RBitWidth)
514 return (int)LBitWidth - (int)RBitWidth;
515 return LA.ult(RA) ? -1 : 1;
519 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
520 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
522 // Compare addrec loop depths.
523 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
524 if (LLoop != RLoop) {
525 unsigned LDepth = LLoop->getLoopDepth(),
526 RDepth = RLoop->getLoopDepth();
527 if (LDepth != RDepth)
528 return (int)LDepth - (int)RDepth;
531 // Addrec complexity grows with operand count.
532 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
533 if (LNumOps != RNumOps)
534 return (int)LNumOps - (int)RNumOps;
536 // Lexicographically compare.
537 for (unsigned i = 0; i != LNumOps; ++i) {
538 long X = compare(LA->getOperand(i), RA->getOperand(i));
550 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
551 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
553 // Lexicographically compare n-ary expressions.
554 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
555 for (unsigned i = 0; i != LNumOps; ++i) {
558 long X = compare(LC->getOperand(i), RC->getOperand(i));
562 return (int)LNumOps - (int)RNumOps;
566 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
567 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
569 // Lexicographically compare udiv expressions.
570 long X = compare(LC->getLHS(), RC->getLHS());
573 return compare(LC->getRHS(), RC->getRHS());
579 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
580 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
582 // Compare cast expressions by operand.
583 return compare(LC->getOperand(), RC->getOperand());
590 llvm_unreachable("Unknown SCEV kind!");
596 /// GroupByComplexity - Given a list of SCEV objects, order them by their
597 /// complexity, and group objects of the same complexity together by value.
598 /// When this routine is finished, we know that any duplicates in the vector are
599 /// consecutive and that complexity is monotonically increasing.
601 /// Note that we go take special precautions to ensure that we get deterministic
602 /// results from this routine. In other words, we don't want the results of
603 /// this to depend on where the addresses of various SCEV objects happened to
606 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
608 if (Ops.size() < 2) return; // Noop
609 if (Ops.size() == 2) {
610 // This is the common case, which also happens to be trivially simple.
612 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
613 if (SCEVComplexityCompare(LI)(RHS, LHS))
618 // Do the rough sort by complexity.
619 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
621 // Now that we are sorted by complexity, group elements of the same
622 // complexity. Note that this is, at worst, N^2, but the vector is likely to
623 // be extremely short in practice. Note that we take this approach because we
624 // do not want to depend on the addresses of the objects we are grouping.
625 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
626 const SCEV *S = Ops[i];
627 unsigned Complexity = S->getSCEVType();
629 // If there are any objects of the same complexity and same value as this
631 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
632 if (Ops[j] == S) { // Found a duplicate.
633 // Move it to immediately after i'th element.
634 std::swap(Ops[i+1], Ops[j]);
635 ++i; // no need to rescan it.
636 if (i == e-2) return; // Done!
644 //===----------------------------------------------------------------------===//
645 // Simple SCEV method implementations
646 //===----------------------------------------------------------------------===//
648 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
650 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
652 const Type* ResultTy) {
653 // Handle the simplest case efficiently.
655 return SE.getTruncateOrZeroExtend(It, ResultTy);
657 // We are using the following formula for BC(It, K):
659 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
661 // Suppose, W is the bitwidth of the return value. We must be prepared for
662 // overflow. Hence, we must assure that the result of our computation is
663 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
664 // safe in modular arithmetic.
666 // However, this code doesn't use exactly that formula; the formula it uses
667 // is something like the following, where T is the number of factors of 2 in
668 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
671 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
673 // This formula is trivially equivalent to the previous formula. However,
674 // this formula can be implemented much more efficiently. The trick is that
675 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
676 // arithmetic. To do exact division in modular arithmetic, all we have
677 // to do is multiply by the inverse. Therefore, this step can be done at
680 // The next issue is how to safely do the division by 2^T. The way this
681 // is done is by doing the multiplication step at a width of at least W + T
682 // bits. This way, the bottom W+T bits of the product are accurate. Then,
683 // when we perform the division by 2^T (which is equivalent to a right shift
684 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
685 // truncated out after the division by 2^T.
687 // In comparison to just directly using the first formula, this technique
688 // is much more efficient; using the first formula requires W * K bits,
689 // but this formula less than W + K bits. Also, the first formula requires
690 // a division step, whereas this formula only requires multiplies and shifts.
692 // It doesn't matter whether the subtraction step is done in the calculation
693 // width or the input iteration count's width; if the subtraction overflows,
694 // the result must be zero anyway. We prefer here to do it in the width of
695 // the induction variable because it helps a lot for certain cases; CodeGen
696 // isn't smart enough to ignore the overflow, which leads to much less
697 // efficient code if the width of the subtraction is wider than the native
700 // (It's possible to not widen at all by pulling out factors of 2 before
701 // the multiplication; for example, K=2 can be calculated as
702 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
703 // extra arithmetic, so it's not an obvious win, and it gets
704 // much more complicated for K > 3.)
706 // Protection from insane SCEVs; this bound is conservative,
707 // but it probably doesn't matter.
709 return SE.getCouldNotCompute();
711 unsigned W = SE.getTypeSizeInBits(ResultTy);
713 // Calculate K! / 2^T and T; we divide out the factors of two before
714 // multiplying for calculating K! / 2^T to avoid overflow.
715 // Other overflow doesn't matter because we only care about the bottom
716 // W bits of the result.
717 APInt OddFactorial(W, 1);
719 for (unsigned i = 3; i <= K; ++i) {
721 unsigned TwoFactors = Mult.countTrailingZeros();
723 Mult = Mult.lshr(TwoFactors);
724 OddFactorial *= Mult;
727 // We need at least W + T bits for the multiplication step
728 unsigned CalculationBits = W + T;
730 // Calculate 2^T, at width T+W.
731 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
733 // Calculate the multiplicative inverse of K! / 2^T;
734 // this multiplication factor will perform the exact division by
736 APInt Mod = APInt::getSignedMinValue(W+1);
737 APInt MultiplyFactor = OddFactorial.zext(W+1);
738 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
739 MultiplyFactor = MultiplyFactor.trunc(W);
741 // Calculate the product, at width T+W
742 const IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
744 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
745 for (unsigned i = 1; i != K; ++i) {
746 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
747 Dividend = SE.getMulExpr(Dividend,
748 SE.getTruncateOrZeroExtend(S, CalculationTy));
752 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
754 // Truncate the result, and divide by K! / 2^T.
756 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
757 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
760 /// evaluateAtIteration - Return the value of this chain of recurrences at
761 /// the specified iteration number. We can evaluate this recurrence by
762 /// multiplying each element in the chain by the binomial coefficient
763 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
765 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
767 /// where BC(It, k) stands for binomial coefficient.
769 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
770 ScalarEvolution &SE) const {
771 const SCEV *Result = getStart();
772 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
773 // The computation is correct in the face of overflow provided that the
774 // multiplication is performed _after_ the evaluation of the binomial
776 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
777 if (isa<SCEVCouldNotCompute>(Coeff))
780 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
785 //===----------------------------------------------------------------------===//
786 // SCEV Expression folder implementations
787 //===----------------------------------------------------------------------===//
789 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
791 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
792 "This is not a truncating conversion!");
793 assert(isSCEVable(Ty) &&
794 "This is not a conversion to a SCEVable type!");
795 Ty = getEffectiveSCEVType(Ty);
798 ID.AddInteger(scTruncate);
802 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
804 // Fold if the operand is constant.
805 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
807 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
808 getEffectiveSCEVType(Ty))));
810 // trunc(trunc(x)) --> trunc(x)
811 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
812 return getTruncateExpr(ST->getOperand(), Ty);
814 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
815 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
816 return getTruncateOrSignExtend(SS->getOperand(), Ty);
818 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
819 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
820 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
822 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
823 // eliminate all the truncates.
824 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
825 SmallVector<const SCEV *, 4> Operands;
826 bool hasTrunc = false;
827 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
828 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
829 hasTrunc = isa<SCEVTruncateExpr>(S);
830 Operands.push_back(S);
833 return getAddExpr(Operands, false, false);
834 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
837 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
838 // eliminate all the truncates.
839 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
840 SmallVector<const SCEV *, 4> Operands;
841 bool hasTrunc = false;
842 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
843 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
844 hasTrunc = isa<SCEVTruncateExpr>(S);
845 Operands.push_back(S);
848 return getMulExpr(Operands, false, false);
849 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
852 // If the input value is a chrec scev, truncate the chrec's operands.
853 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
854 SmallVector<const SCEV *, 4> Operands;
855 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
856 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
857 return getAddRecExpr(Operands, AddRec->getLoop());
860 // As a special case, fold trunc(undef) to undef. We don't want to
861 // know too much about SCEVUnknowns, but this special case is handy
863 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
864 if (isa<UndefValue>(U->getValue()))
865 return getSCEV(UndefValue::get(Ty));
867 // The cast wasn't folded; create an explicit cast node. We can reuse
868 // the existing insert position since if we get here, we won't have
869 // made any changes which would invalidate it.
870 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
872 UniqueSCEVs.InsertNode(S, IP);
876 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
878 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
879 "This is not an extending conversion!");
880 assert(isSCEVable(Ty) &&
881 "This is not a conversion to a SCEVable type!");
882 Ty = getEffectiveSCEVType(Ty);
884 // Fold if the operand is constant.
885 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
887 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
888 getEffectiveSCEVType(Ty))));
890 // zext(zext(x)) --> zext(x)
891 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
892 return getZeroExtendExpr(SZ->getOperand(), Ty);
894 // Before doing any expensive analysis, check to see if we've already
895 // computed a SCEV for this Op and Ty.
897 ID.AddInteger(scZeroExtend);
901 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
903 // zext(trunc(x)) --> zext(x) or x or trunc(x)
904 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
905 // It's possible the bits taken off by the truncate were all zero bits. If
906 // so, we should be able to simplify this further.
907 const SCEV *X = ST->getOperand();
908 ConstantRange CR = getUnsignedRange(X);
909 unsigned TruncBits = getTypeSizeInBits(ST->getType());
910 unsigned NewBits = getTypeSizeInBits(Ty);
911 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
912 CR.zextOrTrunc(NewBits)))
913 return getTruncateOrZeroExtend(X, Ty);
916 // If the input value is a chrec scev, and we can prove that the value
917 // did not overflow the old, smaller, value, we can zero extend all of the
918 // operands (often constants). This allows analysis of something like
919 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
920 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
921 if (AR->isAffine()) {
922 const SCEV *Start = AR->getStart();
923 const SCEV *Step = AR->getStepRecurrence(*this);
924 unsigned BitWidth = getTypeSizeInBits(AR->getType());
925 const Loop *L = AR->getLoop();
927 // If we have special knowledge that this addrec won't overflow,
928 // we don't need to do any further analysis.
929 if (AR->hasNoUnsignedWrap())
930 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
931 getZeroExtendExpr(Step, Ty),
934 // Check whether the backedge-taken count is SCEVCouldNotCompute.
935 // Note that this serves two purposes: It filters out loops that are
936 // simply not analyzable, and it covers the case where this code is
937 // being called from within backedge-taken count analysis, such that
938 // attempting to ask for the backedge-taken count would likely result
939 // in infinite recursion. In the later case, the analysis code will
940 // cope with a conservative value, and it will take care to purge
941 // that value once it has finished.
942 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
943 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
944 // Manually compute the final value for AR, checking for
947 // Check whether the backedge-taken count can be losslessly casted to
948 // the addrec's type. The count is always unsigned.
949 const SCEV *CastedMaxBECount =
950 getTruncateOrZeroExtend(MaxBECount, Start->getType());
951 const SCEV *RecastedMaxBECount =
952 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
953 if (MaxBECount == RecastedMaxBECount) {
954 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
955 // Check whether Start+Step*MaxBECount has no unsigned overflow.
956 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
957 const SCEV *Add = getAddExpr(Start, ZMul);
958 const SCEV *OperandExtendedAdd =
959 getAddExpr(getZeroExtendExpr(Start, WideTy),
960 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
961 getZeroExtendExpr(Step, WideTy)));
962 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
963 // Return the expression with the addrec on the outside.
964 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
965 getZeroExtendExpr(Step, Ty),
968 // Similar to above, only this time treat the step value as signed.
969 // This covers loops that count down.
970 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
971 Add = getAddExpr(Start, SMul);
973 getAddExpr(getZeroExtendExpr(Start, WideTy),
974 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
975 getSignExtendExpr(Step, WideTy)));
976 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
977 // Return the expression with the addrec on the outside.
978 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
979 getSignExtendExpr(Step, Ty),
983 // If the backedge is guarded by a comparison with the pre-inc value
984 // the addrec is safe. Also, if the entry is guarded by a comparison
985 // with the start value and the backedge is guarded by a comparison
986 // with the post-inc value, the addrec is safe.
987 if (isKnownPositive(Step)) {
988 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
989 getUnsignedRange(Step).getUnsignedMax());
990 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
991 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
992 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
993 AR->getPostIncExpr(*this), N)))
994 // Return the expression with the addrec on the outside.
995 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
996 getZeroExtendExpr(Step, Ty),
998 } else if (isKnownNegative(Step)) {
999 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1000 getSignedRange(Step).getSignedMin());
1001 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1002 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1003 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1004 AR->getPostIncExpr(*this), N)))
1005 // Return the expression with the addrec on the outside.
1006 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1007 getSignExtendExpr(Step, Ty),
1013 // The cast wasn't folded; create an explicit cast node.
1014 // Recompute the insert position, as it may have been invalidated.
1015 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1016 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1018 UniqueSCEVs.InsertNode(S, IP);
1022 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1024 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1025 "This is not an extending conversion!");
1026 assert(isSCEVable(Ty) &&
1027 "This is not a conversion to a SCEVable type!");
1028 Ty = getEffectiveSCEVType(Ty);
1030 // Fold if the operand is constant.
1031 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1033 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1034 getEffectiveSCEVType(Ty))));
1036 // sext(sext(x)) --> sext(x)
1037 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1038 return getSignExtendExpr(SS->getOperand(), Ty);
1040 // sext(zext(x)) --> zext(x)
1041 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1042 return getZeroExtendExpr(SZ->getOperand(), Ty);
1044 // Before doing any expensive analysis, check to see if we've already
1045 // computed a SCEV for this Op and Ty.
1046 FoldingSetNodeID ID;
1047 ID.AddInteger(scSignExtend);
1051 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1053 // If the input value is provably positive, build a zext instead.
1054 if (isKnownNonNegative(Op))
1055 return getZeroExtendExpr(Op, Ty);
1057 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1058 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1059 // It's possible the bits taken off by the truncate were all sign bits. If
1060 // so, we should be able to simplify this further.
1061 const SCEV *X = ST->getOperand();
1062 ConstantRange CR = getSignedRange(X);
1063 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1064 unsigned NewBits = getTypeSizeInBits(Ty);
1065 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1066 CR.sextOrTrunc(NewBits)))
1067 return getTruncateOrSignExtend(X, Ty);
1070 // If the input value is a chrec scev, and we can prove that the value
1071 // did not overflow the old, smaller, value, we can sign extend all of the
1072 // operands (often constants). This allows analysis of something like
1073 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1074 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1075 if (AR->isAffine()) {
1076 const SCEV *Start = AR->getStart();
1077 const SCEV *Step = AR->getStepRecurrence(*this);
1078 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1079 const Loop *L = AR->getLoop();
1081 // If we have special knowledge that this addrec won't overflow,
1082 // we don't need to do any further analysis.
1083 if (AR->hasNoSignedWrap())
1084 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1085 getSignExtendExpr(Step, Ty),
1088 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1089 // Note that this serves two purposes: It filters out loops that are
1090 // simply not analyzable, and it covers the case where this code is
1091 // being called from within backedge-taken count analysis, such that
1092 // attempting to ask for the backedge-taken count would likely result
1093 // in infinite recursion. In the later case, the analysis code will
1094 // cope with a conservative value, and it will take care to purge
1095 // that value once it has finished.
1096 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1097 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1098 // Manually compute the final value for AR, checking for
1101 // Check whether the backedge-taken count can be losslessly casted to
1102 // the addrec's type. The count is always unsigned.
1103 const SCEV *CastedMaxBECount =
1104 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1105 const SCEV *RecastedMaxBECount =
1106 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1107 if (MaxBECount == RecastedMaxBECount) {
1108 const Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1109 // Check whether Start+Step*MaxBECount has no signed overflow.
1110 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1111 const SCEV *Add = getAddExpr(Start, SMul);
1112 const SCEV *OperandExtendedAdd =
1113 getAddExpr(getSignExtendExpr(Start, WideTy),
1114 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1115 getSignExtendExpr(Step, WideTy)));
1116 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1117 // Return the expression with the addrec on the outside.
1118 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1119 getSignExtendExpr(Step, Ty),
1122 // Similar to above, only this time treat the step value as unsigned.
1123 // This covers loops that count up with an unsigned step.
1124 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1125 Add = getAddExpr(Start, UMul);
1126 OperandExtendedAdd =
1127 getAddExpr(getSignExtendExpr(Start, WideTy),
1128 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1129 getZeroExtendExpr(Step, WideTy)));
1130 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd)
1131 // Return the expression with the addrec on the outside.
1132 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1133 getZeroExtendExpr(Step, Ty),
1137 // If the backedge is guarded by a comparison with the pre-inc value
1138 // the addrec is safe. Also, if the entry is guarded by a comparison
1139 // with the start value and the backedge is guarded by a comparison
1140 // with the post-inc value, the addrec is safe.
1141 if (isKnownPositive(Step)) {
1142 const SCEV *N = getConstant(APInt::getSignedMinValue(BitWidth) -
1143 getSignedRange(Step).getSignedMax());
1144 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT, AR, N) ||
1145 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SLT, Start, N) &&
1146 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SLT,
1147 AR->getPostIncExpr(*this), N)))
1148 // Return the expression with the addrec on the outside.
1149 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1150 getSignExtendExpr(Step, Ty),
1152 } else if (isKnownNegative(Step)) {
1153 const SCEV *N = getConstant(APInt::getSignedMaxValue(BitWidth) -
1154 getSignedRange(Step).getSignedMin());
1155 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT, AR, N) ||
1156 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_SGT, Start, N) &&
1157 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_SGT,
1158 AR->getPostIncExpr(*this), N)))
1159 // Return the expression with the addrec on the outside.
1160 return getAddRecExpr(getSignExtendExpr(Start, Ty),
1161 getSignExtendExpr(Step, Ty),
1167 // The cast wasn't folded; create an explicit cast node.
1168 // Recompute the insert position, as it may have been invalidated.
1169 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1170 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1172 UniqueSCEVs.InsertNode(S, IP);
1176 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1177 /// unspecified bits out to the given type.
1179 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1181 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1182 "This is not an extending conversion!");
1183 assert(isSCEVable(Ty) &&
1184 "This is not a conversion to a SCEVable type!");
1185 Ty = getEffectiveSCEVType(Ty);
1187 // Sign-extend negative constants.
1188 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1189 if (SC->getValue()->getValue().isNegative())
1190 return getSignExtendExpr(Op, Ty);
1192 // Peel off a truncate cast.
1193 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1194 const SCEV *NewOp = T->getOperand();
1195 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1196 return getAnyExtendExpr(NewOp, Ty);
1197 return getTruncateOrNoop(NewOp, Ty);
1200 // Next try a zext cast. If the cast is folded, use it.
1201 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1202 if (!isa<SCEVZeroExtendExpr>(ZExt))
1205 // Next try a sext cast. If the cast is folded, use it.
1206 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1207 if (!isa<SCEVSignExtendExpr>(SExt))
1210 // Force the cast to be folded into the operands of an addrec.
1211 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1212 SmallVector<const SCEV *, 4> Ops;
1213 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1215 Ops.push_back(getAnyExtendExpr(*I, Ty));
1216 return getAddRecExpr(Ops, AR->getLoop());
1219 // As a special case, fold anyext(undef) to undef. We don't want to
1220 // know too much about SCEVUnknowns, but this special case is handy
1222 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
1223 if (isa<UndefValue>(U->getValue()))
1224 return getSCEV(UndefValue::get(Ty));
1226 // If the expression is obviously signed, use the sext cast value.
1227 if (isa<SCEVSMaxExpr>(Op))
1230 // Absent any other information, use the zext cast value.
1234 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1235 /// a list of operands to be added under the given scale, update the given
1236 /// map. This is a helper function for getAddRecExpr. As an example of
1237 /// what it does, given a sequence of operands that would form an add
1238 /// expression like this:
1240 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1242 /// where A and B are constants, update the map with these values:
1244 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1246 /// and add 13 + A*B*29 to AccumulatedConstant.
1247 /// This will allow getAddRecExpr to produce this:
1249 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1251 /// This form often exposes folding opportunities that are hidden in
1252 /// the original operand list.
1254 /// Return true iff it appears that any interesting folding opportunities
1255 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1256 /// the common case where no interesting opportunities are present, and
1257 /// is also used as a check to avoid infinite recursion.
1260 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1261 SmallVector<const SCEV *, 8> &NewOps,
1262 APInt &AccumulatedConstant,
1263 const SCEV *const *Ops, size_t NumOperands,
1265 ScalarEvolution &SE) {
1266 bool Interesting = false;
1268 // Iterate over the add operands. They are sorted, with constants first.
1270 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1272 // Pull a buried constant out to the outside.
1273 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1275 AccumulatedConstant += Scale * C->getValue()->getValue();
1278 // Next comes everything else. We're especially interested in multiplies
1279 // here, but they're in the middle, so just visit the rest with one loop.
1280 for (; i != NumOperands; ++i) {
1281 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1282 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1284 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1285 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1286 // A multiplication of a constant with another add; recurse.
1287 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1289 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1290 Add->op_begin(), Add->getNumOperands(),
1293 // A multiplication of a constant with some other value. Update
1295 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1296 const SCEV *Key = SE.getMulExpr(MulOps);
1297 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1298 M.insert(std::make_pair(Key, NewScale));
1300 NewOps.push_back(Pair.first->first);
1302 Pair.first->second += NewScale;
1303 // The map already had an entry for this value, which may indicate
1304 // a folding opportunity.
1309 // An ordinary operand. Update the map.
1310 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1311 M.insert(std::make_pair(Ops[i], Scale));
1313 NewOps.push_back(Pair.first->first);
1315 Pair.first->second += Scale;
1316 // The map already had an entry for this value, which may indicate
1317 // a folding opportunity.
1327 struct APIntCompare {
1328 bool operator()(const APInt &LHS, const APInt &RHS) const {
1329 return LHS.ult(RHS);
1334 /// getAddExpr - Get a canonical add expression, or something simpler if
1336 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1337 bool HasNUW, bool HasNSW) {
1338 assert(!Ops.empty() && "Cannot get empty add!");
1339 if (Ops.size() == 1) return Ops[0];
1341 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1342 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1343 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1344 "SCEVAddExpr operand types don't match!");
1347 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1348 if (!HasNUW && HasNSW) {
1350 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1351 E = Ops.end(); I != E; ++I)
1352 if (!isKnownNonNegative(*I)) {
1356 if (All) HasNUW = true;
1359 // Sort by complexity, this groups all similar expression types together.
1360 GroupByComplexity(Ops, LI);
1362 // If there are any constants, fold them together.
1364 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1366 assert(Idx < Ops.size());
1367 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1368 // We found two constants, fold them together!
1369 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1370 RHSC->getValue()->getValue());
1371 if (Ops.size() == 2) return Ops[0];
1372 Ops.erase(Ops.begin()+1); // Erase the folded element
1373 LHSC = cast<SCEVConstant>(Ops[0]);
1376 // If we are left with a constant zero being added, strip it off.
1377 if (LHSC->getValue()->isZero()) {
1378 Ops.erase(Ops.begin());
1382 if (Ops.size() == 1) return Ops[0];
1385 // Okay, check to see if the same value occurs in the operand list more than
1386 // once. If so, merge them together into an multiply expression. Since we
1387 // sorted the list, these values are required to be adjacent.
1388 const Type *Ty = Ops[0]->getType();
1389 bool FoundMatch = false;
1390 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1391 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1392 // Scan ahead to count how many equal operands there are.
1394 while (i+Count != e && Ops[i+Count] == Ops[i])
1396 // Merge the values into a multiply.
1397 const SCEV *Scale = getConstant(Ty, Count);
1398 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1399 if (Ops.size() == Count)
1402 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1403 --i; e -= Count - 1;
1407 return getAddExpr(Ops, HasNUW, HasNSW);
1409 // Check for truncates. If all the operands are truncated from the same
1410 // type, see if factoring out the truncate would permit the result to be
1411 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1412 // if the contents of the resulting outer trunc fold to something simple.
1413 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1414 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1415 const Type *DstType = Trunc->getType();
1416 const Type *SrcType = Trunc->getOperand()->getType();
1417 SmallVector<const SCEV *, 8> LargeOps;
1419 // Check all the operands to see if they can be represented in the
1420 // source type of the truncate.
1421 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1422 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1423 if (T->getOperand()->getType() != SrcType) {
1427 LargeOps.push_back(T->getOperand());
1428 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1429 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1430 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1431 SmallVector<const SCEV *, 8> LargeMulOps;
1432 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1433 if (const SCEVTruncateExpr *T =
1434 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1435 if (T->getOperand()->getType() != SrcType) {
1439 LargeMulOps.push_back(T->getOperand());
1440 } else if (const SCEVConstant *C =
1441 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1442 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1449 LargeOps.push_back(getMulExpr(LargeMulOps));
1456 // Evaluate the expression in the larger type.
1457 const SCEV *Fold = getAddExpr(LargeOps, HasNUW, HasNSW);
1458 // If it folds to something simple, use it. Otherwise, don't.
1459 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1460 return getTruncateExpr(Fold, DstType);
1464 // Skip past any other cast SCEVs.
1465 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1468 // If there are add operands they would be next.
1469 if (Idx < Ops.size()) {
1470 bool DeletedAdd = false;
1471 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1472 // If we have an add, expand the add operands onto the end of the operands
1474 Ops.erase(Ops.begin()+Idx);
1475 Ops.append(Add->op_begin(), Add->op_end());
1479 // If we deleted at least one add, we added operands to the end of the list,
1480 // and they are not necessarily sorted. Recurse to resort and resimplify
1481 // any operands we just acquired.
1483 return getAddExpr(Ops);
1486 // Skip over the add expression until we get to a multiply.
1487 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1490 // Check to see if there are any folding opportunities present with
1491 // operands multiplied by constant values.
1492 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1493 uint64_t BitWidth = getTypeSizeInBits(Ty);
1494 DenseMap<const SCEV *, APInt> M;
1495 SmallVector<const SCEV *, 8> NewOps;
1496 APInt AccumulatedConstant(BitWidth, 0);
1497 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1498 Ops.data(), Ops.size(),
1499 APInt(BitWidth, 1), *this)) {
1500 // Some interesting folding opportunity is present, so its worthwhile to
1501 // re-generate the operands list. Group the operands by constant scale,
1502 // to avoid multiplying by the same constant scale multiple times.
1503 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1504 for (SmallVector<const SCEV *, 8>::const_iterator I = NewOps.begin(),
1505 E = NewOps.end(); I != E; ++I)
1506 MulOpLists[M.find(*I)->second].push_back(*I);
1507 // Re-generate the operands list.
1509 if (AccumulatedConstant != 0)
1510 Ops.push_back(getConstant(AccumulatedConstant));
1511 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1512 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1514 Ops.push_back(getMulExpr(getConstant(I->first),
1515 getAddExpr(I->second)));
1517 return getConstant(Ty, 0);
1518 if (Ops.size() == 1)
1520 return getAddExpr(Ops);
1524 // If we are adding something to a multiply expression, make sure the
1525 // something is not already an operand of the multiply. If so, merge it into
1527 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1528 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1529 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1530 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1531 if (isa<SCEVConstant>(MulOpSCEV))
1533 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1534 if (MulOpSCEV == Ops[AddOp]) {
1535 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1536 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1537 if (Mul->getNumOperands() != 2) {
1538 // If the multiply has more than two operands, we must get the
1540 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1541 Mul->op_begin()+MulOp);
1542 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1543 InnerMul = getMulExpr(MulOps);
1545 const SCEV *One = getConstant(Ty, 1);
1546 const SCEV *AddOne = getAddExpr(One, InnerMul);
1547 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1548 if (Ops.size() == 2) return OuterMul;
1550 Ops.erase(Ops.begin()+AddOp);
1551 Ops.erase(Ops.begin()+Idx-1);
1553 Ops.erase(Ops.begin()+Idx);
1554 Ops.erase(Ops.begin()+AddOp-1);
1556 Ops.push_back(OuterMul);
1557 return getAddExpr(Ops);
1560 // Check this multiply against other multiplies being added together.
1561 for (unsigned OtherMulIdx = Idx+1;
1562 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1564 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1565 // If MulOp occurs in OtherMul, we can fold the two multiplies
1567 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1568 OMulOp != e; ++OMulOp)
1569 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1570 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1571 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1572 if (Mul->getNumOperands() != 2) {
1573 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1574 Mul->op_begin()+MulOp);
1575 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1576 InnerMul1 = getMulExpr(MulOps);
1578 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1579 if (OtherMul->getNumOperands() != 2) {
1580 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1581 OtherMul->op_begin()+OMulOp);
1582 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
1583 InnerMul2 = getMulExpr(MulOps);
1585 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1586 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1587 if (Ops.size() == 2) return OuterMul;
1588 Ops.erase(Ops.begin()+Idx);
1589 Ops.erase(Ops.begin()+OtherMulIdx-1);
1590 Ops.push_back(OuterMul);
1591 return getAddExpr(Ops);
1597 // If there are any add recurrences in the operands list, see if any other
1598 // added values are loop invariant. If so, we can fold them into the
1600 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1603 // Scan over all recurrences, trying to fold loop invariants into them.
1604 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1605 // Scan all of the other operands to this add and add them to the vector if
1606 // they are loop invariant w.r.t. the recurrence.
1607 SmallVector<const SCEV *, 8> LIOps;
1608 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1609 const Loop *AddRecLoop = AddRec->getLoop();
1610 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1611 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1612 LIOps.push_back(Ops[i]);
1613 Ops.erase(Ops.begin()+i);
1617 // If we found some loop invariants, fold them into the recurrence.
1618 if (!LIOps.empty()) {
1619 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1620 LIOps.push_back(AddRec->getStart());
1622 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1624 AddRecOps[0] = getAddExpr(LIOps);
1626 // Build the new addrec. Propagate the NUW and NSW flags if both the
1627 // outer add and the inner addrec are guaranteed to have no overflow.
1628 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
1629 HasNUW && AddRec->hasNoUnsignedWrap(),
1630 HasNSW && AddRec->hasNoSignedWrap());
1632 // If all of the other operands were loop invariant, we are done.
1633 if (Ops.size() == 1) return NewRec;
1635 // Otherwise, add the folded AddRec by the non-liv parts.
1636 for (unsigned i = 0;; ++i)
1637 if (Ops[i] == AddRec) {
1641 return getAddExpr(Ops);
1644 // Okay, if there weren't any loop invariants to be folded, check to see if
1645 // there are multiple AddRec's with the same loop induction variable being
1646 // added together. If so, we can fold them.
1647 for (unsigned OtherIdx = Idx+1;
1648 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1650 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1651 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
1652 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1654 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1656 if (const SCEVAddRecExpr *OtherAddRec =
1657 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1658 if (OtherAddRec->getLoop() == AddRecLoop) {
1659 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
1661 if (i >= AddRecOps.size()) {
1662 AddRecOps.append(OtherAddRec->op_begin()+i,
1663 OtherAddRec->op_end());
1666 AddRecOps[i] = getAddExpr(AddRecOps[i],
1667 OtherAddRec->getOperand(i));
1669 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1671 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop);
1672 return getAddExpr(Ops);
1675 // Otherwise couldn't fold anything into this recurrence. Move onto the
1679 // Okay, it looks like we really DO need an add expr. Check to see if we
1680 // already have one, otherwise create a new one.
1681 FoldingSetNodeID ID;
1682 ID.AddInteger(scAddExpr);
1683 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1684 ID.AddPointer(Ops[i]);
1687 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1689 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1690 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1691 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1693 UniqueSCEVs.InsertNode(S, IP);
1695 if (HasNUW) S->setHasNoUnsignedWrap(true);
1696 if (HasNSW) S->setHasNoSignedWrap(true);
1700 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1702 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1703 bool HasNUW, bool HasNSW) {
1704 assert(!Ops.empty() && "Cannot get empty mul!");
1705 if (Ops.size() == 1) return Ops[0];
1707 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1708 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1709 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1710 "SCEVMulExpr operand types don't match!");
1713 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
1714 if (!HasNUW && HasNSW) {
1716 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1717 E = Ops.end(); I != E; ++I)
1718 if (!isKnownNonNegative(*I)) {
1722 if (All) HasNUW = true;
1725 // Sort by complexity, this groups all similar expression types together.
1726 GroupByComplexity(Ops, LI);
1728 // If there are any constants, fold them together.
1730 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1732 // C1*(C2+V) -> C1*C2 + C1*V
1733 if (Ops.size() == 2)
1734 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1735 if (Add->getNumOperands() == 2 &&
1736 isa<SCEVConstant>(Add->getOperand(0)))
1737 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1738 getMulExpr(LHSC, Add->getOperand(1)));
1741 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1742 // We found two constants, fold them together!
1743 ConstantInt *Fold = ConstantInt::get(getContext(),
1744 LHSC->getValue()->getValue() *
1745 RHSC->getValue()->getValue());
1746 Ops[0] = getConstant(Fold);
1747 Ops.erase(Ops.begin()+1); // Erase the folded element
1748 if (Ops.size() == 1) return Ops[0];
1749 LHSC = cast<SCEVConstant>(Ops[0]);
1752 // If we are left with a constant one being multiplied, strip it off.
1753 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1754 Ops.erase(Ops.begin());
1756 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1757 // If we have a multiply of zero, it will always be zero.
1759 } else if (Ops[0]->isAllOnesValue()) {
1760 // If we have a mul by -1 of an add, try distributing the -1 among the
1762 if (Ops.size() == 2)
1763 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1764 SmallVector<const SCEV *, 4> NewOps;
1765 bool AnyFolded = false;
1766 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1768 const SCEV *Mul = getMulExpr(Ops[0], *I);
1769 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1770 NewOps.push_back(Mul);
1773 return getAddExpr(NewOps);
1777 if (Ops.size() == 1)
1781 // Skip over the add expression until we get to a multiply.
1782 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1785 // If there are mul operands inline them all into this expression.
1786 if (Idx < Ops.size()) {
1787 bool DeletedMul = false;
1788 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1789 // If we have an mul, expand the mul operands onto the end of the operands
1791 Ops.erase(Ops.begin()+Idx);
1792 Ops.append(Mul->op_begin(), Mul->op_end());
1796 // If we deleted at least one mul, we added operands to the end of the list,
1797 // and they are not necessarily sorted. Recurse to resort and resimplify
1798 // any operands we just acquired.
1800 return getMulExpr(Ops);
1803 // If there are any add recurrences in the operands list, see if any other
1804 // added values are loop invariant. If so, we can fold them into the
1806 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1809 // Scan over all recurrences, trying to fold loop invariants into them.
1810 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1811 // Scan all of the other operands to this mul and add them to the vector if
1812 // they are loop invariant w.r.t. the recurrence.
1813 SmallVector<const SCEV *, 8> LIOps;
1814 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1815 const Loop *AddRecLoop = AddRec->getLoop();
1816 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1817 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1818 LIOps.push_back(Ops[i]);
1819 Ops.erase(Ops.begin()+i);
1823 // If we found some loop invariants, fold them into the recurrence.
1824 if (!LIOps.empty()) {
1825 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1826 SmallVector<const SCEV *, 4> NewOps;
1827 NewOps.reserve(AddRec->getNumOperands());
1828 const SCEV *Scale = getMulExpr(LIOps);
1829 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1830 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1832 // Build the new addrec. Propagate the NUW and NSW flags if both the
1833 // outer mul and the inner addrec are guaranteed to have no overflow.
1834 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop,
1835 HasNUW && AddRec->hasNoUnsignedWrap(),
1836 HasNSW && AddRec->hasNoSignedWrap());
1838 // If all of the other operands were loop invariant, we are done.
1839 if (Ops.size() == 1) return NewRec;
1841 // Otherwise, multiply the folded AddRec by the non-liv parts.
1842 for (unsigned i = 0;; ++i)
1843 if (Ops[i] == AddRec) {
1847 return getMulExpr(Ops);
1850 // Okay, if there weren't any loop invariants to be folded, check to see if
1851 // there are multiple AddRec's with the same loop induction variable being
1852 // multiplied together. If so, we can fold them.
1853 for (unsigned OtherIdx = Idx+1;
1854 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1856 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1857 // F * G, where F = {A,+,B}<L> and G = {C,+,D}<L> -->
1858 // {A*C,+,F*D + G*B + B*D}<L>
1859 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1861 if (const SCEVAddRecExpr *OtherAddRec =
1862 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1863 if (OtherAddRec->getLoop() == AddRecLoop) {
1864 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1865 const SCEV *NewStart = getMulExpr(F->getStart(), G->getStart());
1866 const SCEV *B = F->getStepRecurrence(*this);
1867 const SCEV *D = G->getStepRecurrence(*this);
1868 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1871 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1873 if (Ops.size() == 2) return NewAddRec;
1874 Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
1875 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1877 return getMulExpr(Ops);
1880 // Otherwise couldn't fold anything into this recurrence. Move onto the
1884 // Okay, it looks like we really DO need an mul expr. Check to see if we
1885 // already have one, otherwise create a new one.
1886 FoldingSetNodeID ID;
1887 ID.AddInteger(scMulExpr);
1888 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1889 ID.AddPointer(Ops[i]);
1892 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1894 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1895 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1896 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
1898 UniqueSCEVs.InsertNode(S, IP);
1900 if (HasNUW) S->setHasNoUnsignedWrap(true);
1901 if (HasNSW) S->setHasNoSignedWrap(true);
1905 /// getUDivExpr - Get a canonical unsigned division expression, or something
1906 /// simpler if possible.
1907 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
1909 assert(getEffectiveSCEVType(LHS->getType()) ==
1910 getEffectiveSCEVType(RHS->getType()) &&
1911 "SCEVUDivExpr operand types don't match!");
1913 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
1914 if (RHSC->getValue()->equalsInt(1))
1915 return LHS; // X udiv 1 --> x
1916 // If the denominator is zero, the result of the udiv is undefined. Don't
1917 // try to analyze it, because the resolution chosen here may differ from
1918 // the resolution chosen in other parts of the compiler.
1919 if (!RHSC->getValue()->isZero()) {
1920 // Determine if the division can be folded into the operands of
1922 // TODO: Generalize this to non-constants by using known-bits information.
1923 const Type *Ty = LHS->getType();
1924 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
1925 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
1926 // For non-power-of-two values, effectively round the value up to the
1927 // nearest power of two.
1928 if (!RHSC->getValue()->getValue().isPowerOf2())
1930 const IntegerType *ExtTy =
1931 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
1932 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
1933 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
1934 if (const SCEVConstant *Step =
1935 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
1936 if (!Step->getValue()->getValue()
1937 .urem(RHSC->getValue()->getValue()) &&
1938 getZeroExtendExpr(AR, ExtTy) ==
1939 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
1940 getZeroExtendExpr(Step, ExtTy),
1942 SmallVector<const SCEV *, 4> Operands;
1943 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
1944 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
1945 return getAddRecExpr(Operands, AR->getLoop());
1947 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
1948 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
1949 SmallVector<const SCEV *, 4> Operands;
1950 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
1951 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
1952 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
1953 // Find an operand that's safely divisible.
1954 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
1955 const SCEV *Op = M->getOperand(i);
1956 const SCEV *Div = getUDivExpr(Op, RHSC);
1957 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
1958 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
1961 return getMulExpr(Operands);
1965 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
1966 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
1967 SmallVector<const SCEV *, 4> Operands;
1968 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
1969 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
1970 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
1972 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
1973 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
1974 if (isa<SCEVUDivExpr>(Op) ||
1975 getMulExpr(Op, RHS) != A->getOperand(i))
1977 Operands.push_back(Op);
1979 if (Operands.size() == A->getNumOperands())
1980 return getAddExpr(Operands);
1984 // Fold if both operands are constant.
1985 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
1986 Constant *LHSCV = LHSC->getValue();
1987 Constant *RHSCV = RHSC->getValue();
1988 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
1994 FoldingSetNodeID ID;
1995 ID.AddInteger(scUDivExpr);
1999 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2000 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2002 UniqueSCEVs.InsertNode(S, IP);
2007 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2008 /// Simplify the expression as much as possible.
2009 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start,
2010 const SCEV *Step, const Loop *L,
2011 bool HasNUW, bool HasNSW) {
2012 SmallVector<const SCEV *, 4> Operands;
2013 Operands.push_back(Start);
2014 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2015 if (StepChrec->getLoop() == L) {
2016 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2017 return getAddRecExpr(Operands, L);
2020 Operands.push_back(Step);
2021 return getAddRecExpr(Operands, L, HasNUW, HasNSW);
2024 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2025 /// Simplify the expression as much as possible.
2027 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2029 bool HasNUW, bool HasNSW) {
2030 if (Operands.size() == 1) return Operands[0];
2032 const Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2033 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2034 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2035 "SCEVAddRecExpr operand types don't match!");
2036 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2037 assert(isLoopInvariant(Operands[i], L) &&
2038 "SCEVAddRecExpr operand is not loop-invariant!");
2041 if (Operands.back()->isZero()) {
2042 Operands.pop_back();
2043 return getAddRecExpr(Operands, L, HasNUW, HasNSW); // {X,+,0} --> X
2046 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2047 // use that information to infer NUW and NSW flags. However, computing a
2048 // BE count requires calling getAddRecExpr, so we may not yet have a
2049 // meaningful BE count at this point (and if we don't, we'd be stuck
2050 // with a SCEVCouldNotCompute as the cached BE count).
2052 // If HasNSW is true and all the operands are non-negative, infer HasNUW.
2053 if (!HasNUW && HasNSW) {
2055 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2056 E = Operands.end(); I != E; ++I)
2057 if (!isKnownNonNegative(*I)) {
2061 if (All) HasNUW = true;
2064 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2065 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2066 const Loop *NestedLoop = NestedAR->getLoop();
2067 if (L->contains(NestedLoop) ?
2068 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2069 (!NestedLoop->contains(L) &&
2070 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2071 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2072 NestedAR->op_end());
2073 Operands[0] = NestedAR->getStart();
2074 // AddRecs require their operands be loop-invariant with respect to their
2075 // loops. Don't perform this transformation if it would break this
2077 bool AllInvariant = true;
2078 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2079 if (!isLoopInvariant(Operands[i], L)) {
2080 AllInvariant = false;
2084 NestedOperands[0] = getAddRecExpr(Operands, L);
2085 AllInvariant = true;
2086 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2087 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2088 AllInvariant = false;
2092 // Ok, both add recurrences are valid after the transformation.
2093 return getAddRecExpr(NestedOperands, NestedLoop, HasNUW, HasNSW);
2095 // Reset Operands to its original state.
2096 Operands[0] = NestedAR;
2100 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2101 // already have one, otherwise create a new one.
2102 FoldingSetNodeID ID;
2103 ID.AddInteger(scAddRecExpr);
2104 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2105 ID.AddPointer(Operands[i]);
2109 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2111 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2112 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2113 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2114 O, Operands.size(), L);
2115 UniqueSCEVs.InsertNode(S, IP);
2117 if (HasNUW) S->setHasNoUnsignedWrap(true);
2118 if (HasNSW) S->setHasNoSignedWrap(true);
2122 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2124 SmallVector<const SCEV *, 2> Ops;
2127 return getSMaxExpr(Ops);
2131 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2132 assert(!Ops.empty() && "Cannot get empty smax!");
2133 if (Ops.size() == 1) return Ops[0];
2135 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2136 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2137 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2138 "SCEVSMaxExpr operand types don't match!");
2141 // Sort by complexity, this groups all similar expression types together.
2142 GroupByComplexity(Ops, LI);
2144 // If there are any constants, fold them together.
2146 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2148 assert(Idx < Ops.size());
2149 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2150 // We found two constants, fold them together!
2151 ConstantInt *Fold = ConstantInt::get(getContext(),
2152 APIntOps::smax(LHSC->getValue()->getValue(),
2153 RHSC->getValue()->getValue()));
2154 Ops[0] = getConstant(Fold);
2155 Ops.erase(Ops.begin()+1); // Erase the folded element
2156 if (Ops.size() == 1) return Ops[0];
2157 LHSC = cast<SCEVConstant>(Ops[0]);
2160 // If we are left with a constant minimum-int, strip it off.
2161 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2162 Ops.erase(Ops.begin());
2164 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2165 // If we have an smax with a constant maximum-int, it will always be
2170 if (Ops.size() == 1) return Ops[0];
2173 // Find the first SMax
2174 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2177 // Check to see if one of the operands is an SMax. If so, expand its operands
2178 // onto our operand list, and recurse to simplify.
2179 if (Idx < Ops.size()) {
2180 bool DeletedSMax = false;
2181 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2182 Ops.erase(Ops.begin()+Idx);
2183 Ops.append(SMax->op_begin(), SMax->op_end());
2188 return getSMaxExpr(Ops);
2191 // Okay, check to see if the same value occurs in the operand list twice. If
2192 // so, delete one. Since we sorted the list, these values are required to
2194 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2195 // X smax Y smax Y --> X smax Y
2196 // X smax Y --> X, if X is always greater than Y
2197 if (Ops[i] == Ops[i+1] ||
2198 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2199 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2201 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2202 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2206 if (Ops.size() == 1) return Ops[0];
2208 assert(!Ops.empty() && "Reduced smax down to nothing!");
2210 // Okay, it looks like we really DO need an smax expr. Check to see if we
2211 // already have one, otherwise create a new one.
2212 FoldingSetNodeID ID;
2213 ID.AddInteger(scSMaxExpr);
2214 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2215 ID.AddPointer(Ops[i]);
2217 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2218 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2219 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2220 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2222 UniqueSCEVs.InsertNode(S, IP);
2226 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2228 SmallVector<const SCEV *, 2> Ops;
2231 return getUMaxExpr(Ops);
2235 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2236 assert(!Ops.empty() && "Cannot get empty umax!");
2237 if (Ops.size() == 1) return Ops[0];
2239 const Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2240 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2241 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2242 "SCEVUMaxExpr operand types don't match!");
2245 // Sort by complexity, this groups all similar expression types together.
2246 GroupByComplexity(Ops, LI);
2248 // If there are any constants, fold them together.
2250 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2252 assert(Idx < Ops.size());
2253 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2254 // We found two constants, fold them together!
2255 ConstantInt *Fold = ConstantInt::get(getContext(),
2256 APIntOps::umax(LHSC->getValue()->getValue(),
2257 RHSC->getValue()->getValue()));
2258 Ops[0] = getConstant(Fold);
2259 Ops.erase(Ops.begin()+1); // Erase the folded element
2260 if (Ops.size() == 1) return Ops[0];
2261 LHSC = cast<SCEVConstant>(Ops[0]);
2264 // If we are left with a constant minimum-int, strip it off.
2265 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2266 Ops.erase(Ops.begin());
2268 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2269 // If we have an umax with a constant maximum-int, it will always be
2274 if (Ops.size() == 1) return Ops[0];
2277 // Find the first UMax
2278 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2281 // Check to see if one of the operands is a UMax. If so, expand its operands
2282 // onto our operand list, and recurse to simplify.
2283 if (Idx < Ops.size()) {
2284 bool DeletedUMax = false;
2285 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2286 Ops.erase(Ops.begin()+Idx);
2287 Ops.append(UMax->op_begin(), UMax->op_end());
2292 return getUMaxExpr(Ops);
2295 // Okay, check to see if the same value occurs in the operand list twice. If
2296 // so, delete one. Since we sorted the list, these values are required to
2298 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2299 // X umax Y umax Y --> X umax Y
2300 // X umax Y --> X, if X is always greater than Y
2301 if (Ops[i] == Ops[i+1] ||
2302 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2303 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2305 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2306 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2310 if (Ops.size() == 1) return Ops[0];
2312 assert(!Ops.empty() && "Reduced umax down to nothing!");
2314 // Okay, it looks like we really DO need a umax expr. Check to see if we
2315 // already have one, otherwise create a new one.
2316 FoldingSetNodeID ID;
2317 ID.AddInteger(scUMaxExpr);
2318 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2319 ID.AddPointer(Ops[i]);
2321 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2322 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2323 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2324 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2326 UniqueSCEVs.InsertNode(S, IP);
2330 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2332 // ~smax(~x, ~y) == smin(x, y).
2333 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2336 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2338 // ~umax(~x, ~y) == umin(x, y)
2339 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2342 const SCEV *ScalarEvolution::getSizeOfExpr(const Type *AllocTy) {
2343 // If we have TargetData, we can bypass creating a target-independent
2344 // constant expression and then folding it back into a ConstantInt.
2345 // This is just a compile-time optimization.
2347 return getConstant(TD->getIntPtrType(getContext()),
2348 TD->getTypeAllocSize(AllocTy));
2350 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2351 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2352 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2354 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2355 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2358 const SCEV *ScalarEvolution::getAlignOfExpr(const Type *AllocTy) {
2359 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2360 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2361 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2363 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2364 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2367 const SCEV *ScalarEvolution::getOffsetOfExpr(const StructType *STy,
2369 // If we have TargetData, we can bypass creating a target-independent
2370 // constant expression and then folding it back into a ConstantInt.
2371 // This is just a compile-time optimization.
2373 return getConstant(TD->getIntPtrType(getContext()),
2374 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2376 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2377 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2378 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2380 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2381 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2384 const SCEV *ScalarEvolution::getOffsetOfExpr(const Type *CTy,
2385 Constant *FieldNo) {
2386 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2387 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2388 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2390 const Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2391 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2394 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2395 // Don't attempt to do anything other than create a SCEVUnknown object
2396 // here. createSCEV only calls getUnknown after checking for all other
2397 // interesting possibilities, and any other code that calls getUnknown
2398 // is doing so in order to hide a value from SCEV canonicalization.
2400 FoldingSetNodeID ID;
2401 ID.AddInteger(scUnknown);
2404 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
2405 assert(cast<SCEVUnknown>(S)->getValue() == V &&
2406 "Stale SCEVUnknown in uniquing map!");
2409 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
2411 FirstUnknown = cast<SCEVUnknown>(S);
2412 UniqueSCEVs.InsertNode(S, IP);
2416 //===----------------------------------------------------------------------===//
2417 // Basic SCEV Analysis and PHI Idiom Recognition Code
2420 /// isSCEVable - Test if values of the given type are analyzable within
2421 /// the SCEV framework. This primarily includes integer types, and it
2422 /// can optionally include pointer types if the ScalarEvolution class
2423 /// has access to target-specific information.
2424 bool ScalarEvolution::isSCEVable(const Type *Ty) const {
2425 // Integers and pointers are always SCEVable.
2426 return Ty->isIntegerTy() || Ty->isPointerTy();
2429 /// getTypeSizeInBits - Return the size in bits of the specified type,
2430 /// for which isSCEVable must return true.
2431 uint64_t ScalarEvolution::getTypeSizeInBits(const Type *Ty) const {
2432 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2434 // If we have a TargetData, use it!
2436 return TD->getTypeSizeInBits(Ty);
2438 // Integer types have fixed sizes.
2439 if (Ty->isIntegerTy())
2440 return Ty->getPrimitiveSizeInBits();
2442 // The only other support type is pointer. Without TargetData, conservatively
2443 // assume pointers are 64-bit.
2444 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2448 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2449 /// the given type and which represents how SCEV will treat the given
2450 /// type, for which isSCEVable must return true. For pointer types,
2451 /// this is the pointer-sized integer type.
2452 const Type *ScalarEvolution::getEffectiveSCEVType(const Type *Ty) const {
2453 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2455 if (Ty->isIntegerTy())
2458 // The only other support type is pointer.
2459 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2460 if (TD) return TD->getIntPtrType(getContext());
2462 // Without TargetData, conservatively assume pointers are 64-bit.
2463 return Type::getInt64Ty(getContext());
2466 const SCEV *ScalarEvolution::getCouldNotCompute() {
2467 return &CouldNotCompute;
2470 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2471 /// expression and create a new one.
2472 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2473 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2475 ValueExprMapType::const_iterator I = ValueExprMap.find(V);
2476 if (I != ValueExprMap.end()) return I->second;
2477 const SCEV *S = createSCEV(V);
2479 // The process of creating a SCEV for V may have caused other SCEVs
2480 // to have been created, so it's necessary to insert the new entry
2481 // from scratch, rather than trying to remember the insert position
2483 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2487 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2489 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2490 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2492 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2494 const Type *Ty = V->getType();
2495 Ty = getEffectiveSCEVType(Ty);
2496 return getMulExpr(V,
2497 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2500 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2501 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2502 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2504 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2506 const Type *Ty = V->getType();
2507 Ty = getEffectiveSCEVType(Ty);
2508 const SCEV *AllOnes =
2509 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2510 return getMinusSCEV(AllOnes, V);
2513 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1,
2514 /// and thus the HasNUW and HasNSW bits apply to the resultant add, not
2515 /// whether the sub would have overflowed.
2516 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
2517 bool HasNUW, bool HasNSW) {
2518 // Fast path: X - X --> 0.
2520 return getConstant(LHS->getType(), 0);
2523 return getAddExpr(LHS, getNegativeSCEV(RHS), HasNUW, HasNSW);
2526 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2527 /// input value to the specified type. If the type must be extended, it is zero
2530 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, const Type *Ty) {
2531 const Type *SrcTy = V->getType();
2532 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2533 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2534 "Cannot truncate or zero extend with non-integer arguments!");
2535 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2536 return V; // No conversion
2537 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2538 return getTruncateExpr(V, Ty);
2539 return getZeroExtendExpr(V, Ty);
2542 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2543 /// input value to the specified type. If the type must be extended, it is sign
2546 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2548 const Type *SrcTy = V->getType();
2549 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2550 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2551 "Cannot truncate or zero extend with non-integer arguments!");
2552 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2553 return V; // No conversion
2554 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2555 return getTruncateExpr(V, Ty);
2556 return getSignExtendExpr(V, Ty);
2559 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2560 /// input value to the specified type. If the type must be extended, it is zero
2561 /// extended. The conversion must not be narrowing.
2563 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, const Type *Ty) {
2564 const Type *SrcTy = V->getType();
2565 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2566 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2567 "Cannot noop or zero extend with non-integer arguments!");
2568 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2569 "getNoopOrZeroExtend cannot truncate!");
2570 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2571 return V; // No conversion
2572 return getZeroExtendExpr(V, Ty);
2575 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2576 /// input value to the specified type. If the type must be extended, it is sign
2577 /// extended. The conversion must not be narrowing.
2579 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, const Type *Ty) {
2580 const Type *SrcTy = V->getType();
2581 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2582 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2583 "Cannot noop or sign extend with non-integer arguments!");
2584 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2585 "getNoopOrSignExtend cannot truncate!");
2586 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2587 return V; // No conversion
2588 return getSignExtendExpr(V, Ty);
2591 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2592 /// the input value to the specified type. If the type must be extended,
2593 /// it is extended with unspecified bits. The conversion must not be
2596 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, const Type *Ty) {
2597 const Type *SrcTy = V->getType();
2598 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2599 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2600 "Cannot noop or any extend with non-integer arguments!");
2601 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2602 "getNoopOrAnyExtend cannot truncate!");
2603 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2604 return V; // No conversion
2605 return getAnyExtendExpr(V, Ty);
2608 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2609 /// input value to the specified type. The conversion must not be widening.
2611 ScalarEvolution::getTruncateOrNoop(const SCEV *V, const Type *Ty) {
2612 const Type *SrcTy = V->getType();
2613 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2614 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2615 "Cannot truncate or noop with non-integer arguments!");
2616 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2617 "getTruncateOrNoop cannot extend!");
2618 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2619 return V; // No conversion
2620 return getTruncateExpr(V, Ty);
2623 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2624 /// the types using zero-extension, and then perform a umax operation
2626 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2628 const SCEV *PromotedLHS = LHS;
2629 const SCEV *PromotedRHS = RHS;
2631 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2632 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2634 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2636 return getUMaxExpr(PromotedLHS, PromotedRHS);
2639 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2640 /// the types using zero-extension, and then perform a umin operation
2642 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2644 const SCEV *PromotedLHS = LHS;
2645 const SCEV *PromotedRHS = RHS;
2647 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2648 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2650 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2652 return getUMinExpr(PromotedLHS, PromotedRHS);
2655 /// PushDefUseChildren - Push users of the given Instruction
2656 /// onto the given Worklist.
2658 PushDefUseChildren(Instruction *I,
2659 SmallVectorImpl<Instruction *> &Worklist) {
2660 // Push the def-use children onto the Worklist stack.
2661 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2663 Worklist.push_back(cast<Instruction>(*UI));
2666 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2667 /// instructions that depend on the given instruction and removes them from
2668 /// the ValueExprMapType map if they reference SymName. This is used during PHI
2671 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2672 SmallVector<Instruction *, 16> Worklist;
2673 PushDefUseChildren(PN, Worklist);
2675 SmallPtrSet<Instruction *, 8> Visited;
2677 while (!Worklist.empty()) {
2678 Instruction *I = Worklist.pop_back_val();
2679 if (!Visited.insert(I)) continue;
2681 ValueExprMapType::iterator It =
2682 ValueExprMap.find(static_cast<Value *>(I));
2683 if (It != ValueExprMap.end()) {
2684 const SCEV *Old = It->second;
2686 // Short-circuit the def-use traversal if the symbolic name
2687 // ceases to appear in expressions.
2688 if (Old != SymName && !hasOperand(Old, SymName))
2691 // SCEVUnknown for a PHI either means that it has an unrecognized
2692 // structure, it's a PHI that's in the progress of being computed
2693 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2694 // additional loop trip count information isn't going to change anything.
2695 // In the second case, createNodeForPHI will perform the necessary
2696 // updates on its own when it gets to that point. In the third, we do
2697 // want to forget the SCEVUnknown.
2698 if (!isa<PHINode>(I) ||
2699 !isa<SCEVUnknown>(Old) ||
2700 (I != PN && Old == SymName)) {
2701 forgetMemoizedResults(Old);
2702 ValueExprMap.erase(It);
2706 PushDefUseChildren(I, Worklist);
2710 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2711 /// a loop header, making it a potential recurrence, or it doesn't.
2713 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2714 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2715 if (L->getHeader() == PN->getParent()) {
2716 // The loop may have multiple entrances or multiple exits; we can analyze
2717 // this phi as an addrec if it has a unique entry value and a unique
2719 Value *BEValueV = 0, *StartValueV = 0;
2720 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2721 Value *V = PN->getIncomingValue(i);
2722 if (L->contains(PN->getIncomingBlock(i))) {
2725 } else if (BEValueV != V) {
2729 } else if (!StartValueV) {
2731 } else if (StartValueV != V) {
2736 if (BEValueV && StartValueV) {
2737 // While we are analyzing this PHI node, handle its value symbolically.
2738 const SCEV *SymbolicName = getUnknown(PN);
2739 assert(ValueExprMap.find(PN) == ValueExprMap.end() &&
2740 "PHI node already processed?");
2741 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2743 // Using this symbolic name for the PHI, analyze the value coming around
2745 const SCEV *BEValue = getSCEV(BEValueV);
2747 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2748 // has a special value for the first iteration of the loop.
2750 // If the value coming around the backedge is an add with the symbolic
2751 // value we just inserted, then we found a simple induction variable!
2752 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2753 // If there is a single occurrence of the symbolic value, replace it
2754 // with a recurrence.
2755 unsigned FoundIndex = Add->getNumOperands();
2756 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2757 if (Add->getOperand(i) == SymbolicName)
2758 if (FoundIndex == e) {
2763 if (FoundIndex != Add->getNumOperands()) {
2764 // Create an add with everything but the specified operand.
2765 SmallVector<const SCEV *, 8> Ops;
2766 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2767 if (i != FoundIndex)
2768 Ops.push_back(Add->getOperand(i));
2769 const SCEV *Accum = getAddExpr(Ops);
2771 // This is not a valid addrec if the step amount is varying each
2772 // loop iteration, but is not itself an addrec in this loop.
2773 if (isLoopInvariant(Accum, L) ||
2774 (isa<SCEVAddRecExpr>(Accum) &&
2775 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2776 bool HasNUW = false;
2777 bool HasNSW = false;
2779 // If the increment doesn't overflow, then neither the addrec nor
2780 // the post-increment will overflow.
2781 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2782 if (OBO->hasNoUnsignedWrap())
2784 if (OBO->hasNoSignedWrap())
2786 } else if (const GEPOperator *GEP =
2787 dyn_cast<GEPOperator>(BEValueV)) {
2788 // If the increment is a GEP, then we know it won't perform an
2789 // unsigned overflow, because the address space cannot be
2791 HasNUW |= GEP->isInBounds();
2794 const SCEV *StartVal = getSCEV(StartValueV);
2795 const SCEV *PHISCEV =
2796 getAddRecExpr(StartVal, Accum, L, HasNUW, HasNSW);
2798 // Since the no-wrap flags are on the increment, they apply to the
2799 // post-incremented value as well.
2800 if (isLoopInvariant(Accum, L))
2801 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2802 Accum, L, HasNUW, HasNSW);
2804 // Okay, for the entire analysis of this edge we assumed the PHI
2805 // to be symbolic. We now need to go back and purge all of the
2806 // entries for the scalars that use the symbolic expression.
2807 ForgetSymbolicName(PN, SymbolicName);
2808 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2812 } else if (const SCEVAddRecExpr *AddRec =
2813 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2814 // Otherwise, this could be a loop like this:
2815 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2816 // In this case, j = {1,+,1} and BEValue is j.
2817 // Because the other in-value of i (0) fits the evolution of BEValue
2818 // i really is an addrec evolution.
2819 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2820 const SCEV *StartVal = getSCEV(StartValueV);
2822 // If StartVal = j.start - j.stride, we can use StartVal as the
2823 // initial step of the addrec evolution.
2824 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2825 AddRec->getOperand(1))) {
2826 const SCEV *PHISCEV =
2827 getAddRecExpr(StartVal, AddRec->getOperand(1), L);
2829 // Okay, for the entire analysis of this edge we assumed the PHI
2830 // to be symbolic. We now need to go back and purge all of the
2831 // entries for the scalars that use the symbolic expression.
2832 ForgetSymbolicName(PN, SymbolicName);
2833 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2841 // If the PHI has a single incoming value, follow that value, unless the
2842 // PHI's incoming blocks are in a different loop, in which case doing so
2843 // risks breaking LCSSA form. Instcombine would normally zap these, but
2844 // it doesn't have DominatorTree information, so it may miss cases.
2845 if (Value *V = SimplifyInstruction(PN, TD, DT))
2846 if (LI->replacementPreservesLCSSAForm(PN, V))
2849 // If it's not a loop phi, we can't handle it yet.
2850 return getUnknown(PN);
2853 /// createNodeForGEP - Expand GEP instructions into add and multiply
2854 /// operations. This allows them to be analyzed by regular SCEV code.
2856 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
2858 // Don't blindly transfer the inbounds flag from the GEP instruction to the
2859 // Add expression, because the Instruction may be guarded by control flow
2860 // and the no-overflow bits may not be valid for the expression in any
2863 const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
2864 Value *Base = GEP->getOperand(0);
2865 // Don't attempt to analyze GEPs over unsized objects.
2866 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
2867 return getUnknown(GEP);
2868 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
2869 gep_type_iterator GTI = gep_type_begin(GEP);
2870 for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
2874 // Compute the (potentially symbolic) offset in bytes for this index.
2875 if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
2876 // For a struct, add the member offset.
2877 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
2878 const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
2880 // Add the field offset to the running total offset.
2881 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
2883 // For an array, add the element offset, explicitly scaled.
2884 const SCEV *ElementSize = getSizeOfExpr(*GTI);
2885 const SCEV *IndexS = getSCEV(Index);
2886 // Getelementptr indices are signed.
2887 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
2889 // Multiply the index by the element size to compute the element offset.
2890 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize);
2892 // Add the element offset to the running total offset.
2893 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
2897 // Get the SCEV for the GEP base.
2898 const SCEV *BaseS = getSCEV(Base);
2900 // Add the total offset from all the GEP indices to the base.
2901 return getAddExpr(BaseS, TotalOffset);
2904 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
2905 /// guaranteed to end in (at every loop iteration). It is, at the same time,
2906 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
2907 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
2909 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
2910 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2911 return C->getValue()->getValue().countTrailingZeros();
2913 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
2914 return std::min(GetMinTrailingZeros(T->getOperand()),
2915 (uint32_t)getTypeSizeInBits(T->getType()));
2917 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
2918 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2919 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2920 getTypeSizeInBits(E->getType()) : OpRes;
2923 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
2924 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
2925 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
2926 getTypeSizeInBits(E->getType()) : OpRes;
2929 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
2930 // The result is the min of all operands results.
2931 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2932 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2933 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2937 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
2938 // The result is the sum of all operands results.
2939 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
2940 uint32_t BitWidth = getTypeSizeInBits(M->getType());
2941 for (unsigned i = 1, e = M->getNumOperands();
2942 SumOpRes != BitWidth && i != e; ++i)
2943 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
2948 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
2949 // The result is the min of all operands results.
2950 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
2951 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
2952 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
2956 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
2957 // The result is the min of all operands results.
2958 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2959 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2960 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2964 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
2965 // The result is the min of all operands results.
2966 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
2967 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
2968 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
2972 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2973 // For a SCEVUnknown, ask ValueTracking.
2974 unsigned BitWidth = getTypeSizeInBits(U->getType());
2975 APInt Mask = APInt::getAllOnesValue(BitWidth);
2976 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
2977 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
2978 return Zeros.countTrailingOnes();
2985 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
2988 ScalarEvolution::getUnsignedRange(const SCEV *S) {
2989 // See if we've computed this range already.
2990 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
2991 if (I != UnsignedRanges.end())
2994 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
2995 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
2997 unsigned BitWidth = getTypeSizeInBits(S->getType());
2998 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3000 // If the value has known zeros, the maximum unsigned value will have those
3001 // known zeros as well.
3002 uint32_t TZ = GetMinTrailingZeros(S);
3004 ConservativeResult =
3005 ConstantRange(APInt::getMinValue(BitWidth),
3006 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3008 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3009 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3010 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3011 X = X.add(getUnsignedRange(Add->getOperand(i)));
3012 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3015 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3016 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3017 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3018 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3019 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3022 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3023 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3024 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3025 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3026 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3029 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3030 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3031 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3032 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3033 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3036 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3037 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3038 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3039 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3042 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3043 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3044 return setUnsignedRange(ZExt,
3045 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3048 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3049 ConstantRange X = getUnsignedRange(SExt->getOperand());
3050 return setUnsignedRange(SExt,
3051 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3054 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3055 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3056 return setUnsignedRange(Trunc,
3057 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3060 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3061 // If there's no unsigned wrap, the value will never be less than its
3063 if (AddRec->hasNoUnsignedWrap())
3064 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3065 if (!C->getValue()->isZero())
3066 ConservativeResult =
3067 ConservativeResult.intersectWith(
3068 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3070 // TODO: non-affine addrec
3071 if (AddRec->isAffine()) {
3072 const Type *Ty = AddRec->getType();
3073 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3074 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3075 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3076 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3078 const SCEV *Start = AddRec->getStart();
3079 const SCEV *Step = AddRec->getStepRecurrence(*this);
3081 ConstantRange StartRange = getUnsignedRange(Start);
3082 ConstantRange StepRange = getSignedRange(Step);
3083 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3084 ConstantRange EndRange =
3085 StartRange.add(MaxBECountRange.multiply(StepRange));
3087 // Check for overflow. This must be done with ConstantRange arithmetic
3088 // because we could be called from within the ScalarEvolution overflow
3090 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3091 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3092 ConstantRange ExtMaxBECountRange =
3093 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3094 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3095 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3097 return setUnsignedRange(AddRec, ConservativeResult);
3099 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3100 EndRange.getUnsignedMin());
3101 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3102 EndRange.getUnsignedMax());
3103 if (Min.isMinValue() && Max.isMaxValue())
3104 return setUnsignedRange(AddRec, ConservativeResult);
3105 return setUnsignedRange(AddRec,
3106 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3110 return setUnsignedRange(AddRec, ConservativeResult);
3113 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3114 // For a SCEVUnknown, ask ValueTracking.
3115 APInt Mask = APInt::getAllOnesValue(BitWidth);
3116 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3117 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3118 if (Ones == ~Zeros + 1)
3119 return setUnsignedRange(U, ConservativeResult);
3120 return setUnsignedRange(U,
3121 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3124 return setUnsignedRange(S, ConservativeResult);
3127 /// getSignedRange - Determine the signed range for a particular SCEV.
3130 ScalarEvolution::getSignedRange(const SCEV *S) {
3131 // See if we've computed this range already.
3132 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3133 if (I != SignedRanges.end())
3136 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3137 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3139 unsigned BitWidth = getTypeSizeInBits(S->getType());
3140 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3142 // If the value has known zeros, the maximum signed value will have those
3143 // known zeros as well.
3144 uint32_t TZ = GetMinTrailingZeros(S);
3146 ConservativeResult =
3147 ConstantRange(APInt::getSignedMinValue(BitWidth),
3148 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3150 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3151 ConstantRange X = getSignedRange(Add->getOperand(0));
3152 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3153 X = X.add(getSignedRange(Add->getOperand(i)));
3154 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3157 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3158 ConstantRange X = getSignedRange(Mul->getOperand(0));
3159 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3160 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3161 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3164 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3165 ConstantRange X = getSignedRange(SMax->getOperand(0));
3166 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3167 X = X.smax(getSignedRange(SMax->getOperand(i)));
3168 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3171 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3172 ConstantRange X = getSignedRange(UMax->getOperand(0));
3173 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3174 X = X.umax(getSignedRange(UMax->getOperand(i)));
3175 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3178 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3179 ConstantRange X = getSignedRange(UDiv->getLHS());
3180 ConstantRange Y = getSignedRange(UDiv->getRHS());
3181 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3184 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3185 ConstantRange X = getSignedRange(ZExt->getOperand());
3186 return setSignedRange(ZExt,
3187 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3190 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3191 ConstantRange X = getSignedRange(SExt->getOperand());
3192 return setSignedRange(SExt,
3193 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3196 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3197 ConstantRange X = getSignedRange(Trunc->getOperand());
3198 return setSignedRange(Trunc,
3199 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3202 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3203 // If there's no signed wrap, and all the operands have the same sign or
3204 // zero, the value won't ever change sign.
3205 if (AddRec->hasNoSignedWrap()) {
3206 bool AllNonNeg = true;
3207 bool AllNonPos = true;
3208 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3209 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3210 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3213 ConservativeResult = ConservativeResult.intersectWith(
3214 ConstantRange(APInt(BitWidth, 0),
3215 APInt::getSignedMinValue(BitWidth)));
3217 ConservativeResult = ConservativeResult.intersectWith(
3218 ConstantRange(APInt::getSignedMinValue(BitWidth),
3219 APInt(BitWidth, 1)));
3222 // TODO: non-affine addrec
3223 if (AddRec->isAffine()) {
3224 const Type *Ty = AddRec->getType();
3225 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3226 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3227 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3228 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3230 const SCEV *Start = AddRec->getStart();
3231 const SCEV *Step = AddRec->getStepRecurrence(*this);
3233 ConstantRange StartRange = getSignedRange(Start);
3234 ConstantRange StepRange = getSignedRange(Step);
3235 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3236 ConstantRange EndRange =
3237 StartRange.add(MaxBECountRange.multiply(StepRange));
3239 // Check for overflow. This must be done with ConstantRange arithmetic
3240 // because we could be called from within the ScalarEvolution overflow
3242 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3243 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3244 ConstantRange ExtMaxBECountRange =
3245 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3246 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3247 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3249 return setSignedRange(AddRec, ConservativeResult);
3251 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3252 EndRange.getSignedMin());
3253 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3254 EndRange.getSignedMax());
3255 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3256 return setSignedRange(AddRec, ConservativeResult);
3257 return setSignedRange(AddRec,
3258 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3262 return setSignedRange(AddRec, ConservativeResult);
3265 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3266 // For a SCEVUnknown, ask ValueTracking.
3267 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3268 return setSignedRange(U, ConservativeResult);
3269 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3271 return setSignedRange(U, ConservativeResult);
3272 return setSignedRange(U, ConservativeResult.intersectWith(
3273 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3274 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
3277 return setSignedRange(S, ConservativeResult);
3280 /// createSCEV - We know that there is no SCEV for the specified value.
3281 /// Analyze the expression.
3283 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3284 if (!isSCEVable(V->getType()))
3285 return getUnknown(V);
3287 unsigned Opcode = Instruction::UserOp1;
3288 if (Instruction *I = dyn_cast<Instruction>(V)) {
3289 Opcode = I->getOpcode();
3291 // Don't attempt to analyze instructions in blocks that aren't
3292 // reachable. Such instructions don't matter, and they aren't required
3293 // to obey basic rules for definitions dominating uses which this
3294 // analysis depends on.
3295 if (!DT->isReachableFromEntry(I->getParent()))
3296 return getUnknown(V);
3297 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3298 Opcode = CE->getOpcode();
3299 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3300 return getConstant(CI);
3301 else if (isa<ConstantPointerNull>(V))
3302 return getConstant(V->getType(), 0);
3303 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3304 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3306 return getUnknown(V);
3308 Operator *U = cast<Operator>(V);
3310 case Instruction::Add: {
3311 // The simple thing to do would be to just call getSCEV on both operands
3312 // and call getAddExpr with the result. However if we're looking at a
3313 // bunch of things all added together, this can be quite inefficient,
3314 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3315 // Instead, gather up all the operands and make a single getAddExpr call.
3316 // LLVM IR canonical form means we need only traverse the left operands.
3317 SmallVector<const SCEV *, 4> AddOps;
3318 AddOps.push_back(getSCEV(U->getOperand(1)));
3319 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
3320 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
3321 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
3323 U = cast<Operator>(Op);
3324 const SCEV *Op1 = getSCEV(U->getOperand(1));
3325 if (Opcode == Instruction::Sub)
3326 AddOps.push_back(getNegativeSCEV(Op1));
3328 AddOps.push_back(Op1);
3330 AddOps.push_back(getSCEV(U->getOperand(0)));
3331 return getAddExpr(AddOps);
3333 case Instruction::Mul: {
3334 // See the Add code above.
3335 SmallVector<const SCEV *, 4> MulOps;
3336 MulOps.push_back(getSCEV(U->getOperand(1)));
3337 for (Value *Op = U->getOperand(0);
3338 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
3339 Op = U->getOperand(0)) {
3340 U = cast<Operator>(Op);
3341 MulOps.push_back(getSCEV(U->getOperand(1)));
3343 MulOps.push_back(getSCEV(U->getOperand(0)));
3344 return getMulExpr(MulOps);
3346 case Instruction::UDiv:
3347 return getUDivExpr(getSCEV(U->getOperand(0)),
3348 getSCEV(U->getOperand(1)));
3349 case Instruction::Sub:
3350 return getMinusSCEV(getSCEV(U->getOperand(0)),
3351 getSCEV(U->getOperand(1)));
3352 case Instruction::And:
3353 // For an expression like x&255 that merely masks off the high bits,
3354 // use zext(trunc(x)) as the SCEV expression.
3355 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3356 if (CI->isNullValue())
3357 return getSCEV(U->getOperand(1));
3358 if (CI->isAllOnesValue())
3359 return getSCEV(U->getOperand(0));
3360 const APInt &A = CI->getValue();
3362 // Instcombine's ShrinkDemandedConstant may strip bits out of
3363 // constants, obscuring what would otherwise be a low-bits mask.
3364 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3365 // knew about to reconstruct a low-bits mask value.
3366 unsigned LZ = A.countLeadingZeros();
3367 unsigned BitWidth = A.getBitWidth();
3368 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3369 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3370 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3372 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3374 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3376 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3377 IntegerType::get(getContext(), BitWidth - LZ)),
3382 case Instruction::Or:
3383 // If the RHS of the Or is a constant, we may have something like:
3384 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3385 // optimizations will transparently handle this case.
3387 // In order for this transformation to be safe, the LHS must be of the
3388 // form X*(2^n) and the Or constant must be less than 2^n.
3389 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3390 const SCEV *LHS = getSCEV(U->getOperand(0));
3391 const APInt &CIVal = CI->getValue();
3392 if (GetMinTrailingZeros(LHS) >=
3393 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3394 // Build a plain add SCEV.
3395 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3396 // If the LHS of the add was an addrec and it has no-wrap flags,
3397 // transfer the no-wrap flags, since an or won't introduce a wrap.
3398 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3399 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3400 if (OldAR->hasNoUnsignedWrap())
3401 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoUnsignedWrap(true);
3402 if (OldAR->hasNoSignedWrap())
3403 const_cast<SCEVAddRecExpr *>(NewAR)->setHasNoSignedWrap(true);
3409 case Instruction::Xor:
3410 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3411 // If the RHS of the xor is a signbit, then this is just an add.
3412 // Instcombine turns add of signbit into xor as a strength reduction step.
3413 if (CI->getValue().isSignBit())
3414 return getAddExpr(getSCEV(U->getOperand(0)),
3415 getSCEV(U->getOperand(1)));
3417 // If the RHS of xor is -1, then this is a not operation.
3418 if (CI->isAllOnesValue())
3419 return getNotSCEV(getSCEV(U->getOperand(0)));
3421 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3422 // This is a variant of the check for xor with -1, and it handles
3423 // the case where instcombine has trimmed non-demanded bits out
3424 // of an xor with -1.
3425 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3426 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3427 if (BO->getOpcode() == Instruction::And &&
3428 LCI->getValue() == CI->getValue())
3429 if (const SCEVZeroExtendExpr *Z =
3430 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3431 const Type *UTy = U->getType();
3432 const SCEV *Z0 = Z->getOperand();
3433 const Type *Z0Ty = Z0->getType();
3434 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3436 // If C is a low-bits mask, the zero extend is serving to
3437 // mask off the high bits. Complement the operand and
3438 // re-apply the zext.
3439 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3440 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3442 // If C is a single bit, it may be in the sign-bit position
3443 // before the zero-extend. In this case, represent the xor
3444 // using an add, which is equivalent, and re-apply the zext.
3445 APInt Trunc = CI->getValue().trunc(Z0TySize);
3446 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3448 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3454 case Instruction::Shl:
3455 // Turn shift left of a constant amount into a multiply.
3456 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3457 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3459 // If the shift count is not less than the bitwidth, the result of
3460 // the shift is undefined. Don't try to analyze it, because the
3461 // resolution chosen here may differ from the resolution chosen in
3462 // other parts of the compiler.
3463 if (SA->getValue().uge(BitWidth))
3466 Constant *X = ConstantInt::get(getContext(),
3467 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3468 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3472 case Instruction::LShr:
3473 // Turn logical shift right of a constant into a unsigned divide.
3474 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3475 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3477 // If the shift count is not less than the bitwidth, the result of
3478 // the shift is undefined. Don't try to analyze it, because the
3479 // resolution chosen here may differ from the resolution chosen in
3480 // other parts of the compiler.
3481 if (SA->getValue().uge(BitWidth))
3484 Constant *X = ConstantInt::get(getContext(),
3485 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3486 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3490 case Instruction::AShr:
3491 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3492 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3493 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3494 if (L->getOpcode() == Instruction::Shl &&
3495 L->getOperand(1) == U->getOperand(1)) {
3496 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3498 // If the shift count is not less than the bitwidth, the result of
3499 // the shift is undefined. Don't try to analyze it, because the
3500 // resolution chosen here may differ from the resolution chosen in
3501 // other parts of the compiler.
3502 if (CI->getValue().uge(BitWidth))
3505 uint64_t Amt = BitWidth - CI->getZExtValue();
3506 if (Amt == BitWidth)
3507 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3509 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3510 IntegerType::get(getContext(),
3516 case Instruction::Trunc:
3517 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3519 case Instruction::ZExt:
3520 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3522 case Instruction::SExt:
3523 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3525 case Instruction::BitCast:
3526 // BitCasts are no-op casts so we just eliminate the cast.
3527 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3528 return getSCEV(U->getOperand(0));
3531 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3532 // lead to pointer expressions which cannot safely be expanded to GEPs,
3533 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3534 // simplifying integer expressions.
3536 case Instruction::GetElementPtr:
3537 return createNodeForGEP(cast<GEPOperator>(U));
3539 case Instruction::PHI:
3540 return createNodeForPHI(cast<PHINode>(U));
3542 case Instruction::Select:
3543 // This could be a smax or umax that was lowered earlier.
3544 // Try to recover it.
3545 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3546 Value *LHS = ICI->getOperand(0);
3547 Value *RHS = ICI->getOperand(1);
3548 switch (ICI->getPredicate()) {
3549 case ICmpInst::ICMP_SLT:
3550 case ICmpInst::ICMP_SLE:
3551 std::swap(LHS, RHS);
3553 case ICmpInst::ICMP_SGT:
3554 case ICmpInst::ICMP_SGE:
3555 // a >s b ? a+x : b+x -> smax(a, b)+x
3556 // a >s b ? b+x : a+x -> smin(a, b)+x
3557 if (LHS->getType() == U->getType()) {
3558 const SCEV *LS = getSCEV(LHS);
3559 const SCEV *RS = getSCEV(RHS);
3560 const SCEV *LA = getSCEV(U->getOperand(1));
3561 const SCEV *RA = getSCEV(U->getOperand(2));
3562 const SCEV *LDiff = getMinusSCEV(LA, LS);
3563 const SCEV *RDiff = getMinusSCEV(RA, RS);
3565 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3566 LDiff = getMinusSCEV(LA, RS);
3567 RDiff = getMinusSCEV(RA, LS);
3569 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3572 case ICmpInst::ICMP_ULT:
3573 case ICmpInst::ICMP_ULE:
3574 std::swap(LHS, RHS);
3576 case ICmpInst::ICMP_UGT:
3577 case ICmpInst::ICMP_UGE:
3578 // a >u b ? a+x : b+x -> umax(a, b)+x
3579 // a >u b ? b+x : a+x -> umin(a, b)+x
3580 if (LHS->getType() == U->getType()) {
3581 const SCEV *LS = getSCEV(LHS);
3582 const SCEV *RS = getSCEV(RHS);
3583 const SCEV *LA = getSCEV(U->getOperand(1));
3584 const SCEV *RA = getSCEV(U->getOperand(2));
3585 const SCEV *LDiff = getMinusSCEV(LA, LS);
3586 const SCEV *RDiff = getMinusSCEV(RA, RS);
3588 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3589 LDiff = getMinusSCEV(LA, RS);
3590 RDiff = getMinusSCEV(RA, LS);
3592 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3595 case ICmpInst::ICMP_NE:
3596 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3597 if (LHS->getType() == U->getType() &&
3598 isa<ConstantInt>(RHS) &&
3599 cast<ConstantInt>(RHS)->isZero()) {
3600 const SCEV *One = getConstant(LHS->getType(), 1);
3601 const SCEV *LS = getSCEV(LHS);
3602 const SCEV *LA = getSCEV(U->getOperand(1));
3603 const SCEV *RA = getSCEV(U->getOperand(2));
3604 const SCEV *LDiff = getMinusSCEV(LA, LS);
3605 const SCEV *RDiff = getMinusSCEV(RA, One);
3607 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3610 case ICmpInst::ICMP_EQ:
3611 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3612 if (LHS->getType() == U->getType() &&
3613 isa<ConstantInt>(RHS) &&
3614 cast<ConstantInt>(RHS)->isZero()) {
3615 const SCEV *One = getConstant(LHS->getType(), 1);
3616 const SCEV *LS = getSCEV(LHS);
3617 const SCEV *LA = getSCEV(U->getOperand(1));
3618 const SCEV *RA = getSCEV(U->getOperand(2));
3619 const SCEV *LDiff = getMinusSCEV(LA, One);
3620 const SCEV *RDiff = getMinusSCEV(RA, LS);
3622 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3630 default: // We cannot analyze this expression.
3634 return getUnknown(V);
3639 //===----------------------------------------------------------------------===//
3640 // Iteration Count Computation Code
3643 /// getBackedgeTakenCount - If the specified loop has a predictable
3644 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3645 /// object. The backedge-taken count is the number of times the loop header
3646 /// will be branched to from within the loop. This is one less than the
3647 /// trip count of the loop, since it doesn't count the first iteration,
3648 /// when the header is branched to from outside the loop.
3650 /// Note that it is not valid to call this method on a loop without a
3651 /// loop-invariant backedge-taken count (see
3652 /// hasLoopInvariantBackedgeTakenCount).
3654 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3655 return getBackedgeTakenInfo(L).Exact;
3658 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3659 /// return the least SCEV value that is known never to be less than the
3660 /// actual backedge taken count.
3661 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3662 return getBackedgeTakenInfo(L).Max;
3665 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3666 /// onto the given Worklist.
3668 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3669 BasicBlock *Header = L->getHeader();
3671 // Push all Loop-header PHIs onto the Worklist stack.
3672 for (BasicBlock::iterator I = Header->begin();
3673 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3674 Worklist.push_back(PN);
3677 const ScalarEvolution::BackedgeTakenInfo &
3678 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3679 // Initially insert a CouldNotCompute for this loop. If the insertion
3680 // succeeds, proceed to actually compute a backedge-taken count and
3681 // update the value. The temporary CouldNotCompute value tells SCEV
3682 // code elsewhere that it shouldn't attempt to request a new
3683 // backedge-taken count, which could result in infinite recursion.
3684 std::pair<std::map<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3685 BackedgeTakenCounts.insert(std::make_pair(L, getCouldNotCompute()));
3687 return Pair.first->second;
3689 BackedgeTakenInfo BECount = ComputeBackedgeTakenCount(L);
3690 if (BECount.Exact != getCouldNotCompute()) {
3691 assert(isLoopInvariant(BECount.Exact, L) &&
3692 isLoopInvariant(BECount.Max, L) &&
3693 "Computed backedge-taken count isn't loop invariant for loop!");
3694 ++NumTripCountsComputed;
3696 // Update the value in the map.
3697 Pair.first->second = BECount;
3699 if (BECount.Max != getCouldNotCompute())
3700 // Update the value in the map.
3701 Pair.first->second = BECount;
3702 if (isa<PHINode>(L->getHeader()->begin()))
3703 // Only count loops that have phi nodes as not being computable.
3704 ++NumTripCountsNotComputed;
3707 // Now that we know more about the trip count for this loop, forget any
3708 // existing SCEV values for PHI nodes in this loop since they are only
3709 // conservative estimates made without the benefit of trip count
3710 // information. This is similar to the code in forgetLoop, except that
3711 // it handles SCEVUnknown PHI nodes specially.
3712 if (BECount.hasAnyInfo()) {
3713 SmallVector<Instruction *, 16> Worklist;
3714 PushLoopPHIs(L, Worklist);
3716 SmallPtrSet<Instruction *, 8> Visited;
3717 while (!Worklist.empty()) {
3718 Instruction *I = Worklist.pop_back_val();
3719 if (!Visited.insert(I)) continue;
3721 ValueExprMapType::iterator It =
3722 ValueExprMap.find(static_cast<Value *>(I));
3723 if (It != ValueExprMap.end()) {
3724 const SCEV *Old = It->second;
3726 // SCEVUnknown for a PHI either means that it has an unrecognized
3727 // structure, or it's a PHI that's in the progress of being computed
3728 // by createNodeForPHI. In the former case, additional loop trip
3729 // count information isn't going to change anything. In the later
3730 // case, createNodeForPHI will perform the necessary updates on its
3731 // own when it gets to that point.
3732 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
3733 forgetMemoizedResults(Old);
3734 ValueExprMap.erase(It);
3736 if (PHINode *PN = dyn_cast<PHINode>(I))
3737 ConstantEvolutionLoopExitValue.erase(PN);
3740 PushDefUseChildren(I, Worklist);
3743 return Pair.first->second;
3746 /// forgetLoop - This method should be called by the client when it has
3747 /// changed a loop in a way that may effect ScalarEvolution's ability to
3748 /// compute a trip count, or if the loop is deleted.
3749 void ScalarEvolution::forgetLoop(const Loop *L) {
3750 // Drop any stored trip count value.
3751 BackedgeTakenCounts.erase(L);
3753 // Drop information about expressions based on loop-header PHIs.
3754 SmallVector<Instruction *, 16> Worklist;
3755 PushLoopPHIs(L, Worklist);
3757 SmallPtrSet<Instruction *, 8> Visited;
3758 while (!Worklist.empty()) {
3759 Instruction *I = Worklist.pop_back_val();
3760 if (!Visited.insert(I)) continue;
3762 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3763 if (It != ValueExprMap.end()) {
3764 forgetMemoizedResults(It->second);
3765 ValueExprMap.erase(It);
3766 if (PHINode *PN = dyn_cast<PHINode>(I))
3767 ConstantEvolutionLoopExitValue.erase(PN);
3770 PushDefUseChildren(I, Worklist);
3773 // Forget all contained loops too, to avoid dangling entries in the
3774 // ValuesAtScopes map.
3775 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
3779 /// forgetValue - This method should be called by the client when it has
3780 /// changed a value in a way that may effect its value, or which may
3781 /// disconnect it from a def-use chain linking it to a loop.
3782 void ScalarEvolution::forgetValue(Value *V) {
3783 Instruction *I = dyn_cast<Instruction>(V);
3786 // Drop information about expressions based on loop-header PHIs.
3787 SmallVector<Instruction *, 16> Worklist;
3788 Worklist.push_back(I);
3790 SmallPtrSet<Instruction *, 8> Visited;
3791 while (!Worklist.empty()) {
3792 I = Worklist.pop_back_val();
3793 if (!Visited.insert(I)) continue;
3795 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3796 if (It != ValueExprMap.end()) {
3797 forgetMemoizedResults(It->second);
3798 ValueExprMap.erase(It);
3799 if (PHINode *PN = dyn_cast<PHINode>(I))
3800 ConstantEvolutionLoopExitValue.erase(PN);
3803 PushDefUseChildren(I, Worklist);
3807 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
3808 /// of the specified loop will execute.
3809 ScalarEvolution::BackedgeTakenInfo
3810 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
3811 SmallVector<BasicBlock *, 8> ExitingBlocks;
3812 L->getExitingBlocks(ExitingBlocks);
3814 // Examine all exits and pick the most conservative values.
3815 const SCEV *BECount = getCouldNotCompute();
3816 const SCEV *MaxBECount = getCouldNotCompute();
3817 bool CouldNotComputeBECount = false;
3818 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
3819 BackedgeTakenInfo NewBTI =
3820 ComputeBackedgeTakenCountFromExit(L, ExitingBlocks[i]);
3822 if (NewBTI.Exact == getCouldNotCompute()) {
3823 // We couldn't compute an exact value for this exit, so
3824 // we won't be able to compute an exact value for the loop.
3825 CouldNotComputeBECount = true;
3826 BECount = getCouldNotCompute();
3827 } else if (!CouldNotComputeBECount) {
3828 if (BECount == getCouldNotCompute())
3829 BECount = NewBTI.Exact;
3831 BECount = getUMinFromMismatchedTypes(BECount, NewBTI.Exact);
3833 if (MaxBECount == getCouldNotCompute())
3834 MaxBECount = NewBTI.Max;
3835 else if (NewBTI.Max != getCouldNotCompute())
3836 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, NewBTI.Max);
3839 return BackedgeTakenInfo(BECount, MaxBECount);
3842 /// ComputeBackedgeTakenCountFromExit - Compute the number of times the backedge
3843 /// of the specified loop will execute if it exits via the specified block.
3844 ScalarEvolution::BackedgeTakenInfo
3845 ScalarEvolution::ComputeBackedgeTakenCountFromExit(const Loop *L,
3846 BasicBlock *ExitingBlock) {
3848 // Okay, we've chosen an exiting block. See what condition causes us to
3849 // exit at this block.
3851 // FIXME: we should be able to handle switch instructions (with a single exit)
3852 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
3853 if (ExitBr == 0) return getCouldNotCompute();
3854 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
3856 // At this point, we know we have a conditional branch that determines whether
3857 // the loop is exited. However, we don't know if the branch is executed each
3858 // time through the loop. If not, then the execution count of the branch will
3859 // not be equal to the trip count of the loop.
3861 // Currently we check for this by checking to see if the Exit branch goes to
3862 // the loop header. If so, we know it will always execute the same number of
3863 // times as the loop. We also handle the case where the exit block *is* the
3864 // loop header. This is common for un-rotated loops.
3866 // If both of those tests fail, walk up the unique predecessor chain to the
3867 // header, stopping if there is an edge that doesn't exit the loop. If the
3868 // header is reached, the execution count of the branch will be equal to the
3869 // trip count of the loop.
3871 // More extensive analysis could be done to handle more cases here.
3873 if (ExitBr->getSuccessor(0) != L->getHeader() &&
3874 ExitBr->getSuccessor(1) != L->getHeader() &&
3875 ExitBr->getParent() != L->getHeader()) {
3876 // The simple checks failed, try climbing the unique predecessor chain
3877 // up to the header.
3879 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
3880 BasicBlock *Pred = BB->getUniquePredecessor();
3882 return getCouldNotCompute();
3883 TerminatorInst *PredTerm = Pred->getTerminator();
3884 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
3885 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
3888 // If the predecessor has a successor that isn't BB and isn't
3889 // outside the loop, assume the worst.
3890 if (L->contains(PredSucc))
3891 return getCouldNotCompute();
3893 if (Pred == L->getHeader()) {
3900 return getCouldNotCompute();
3903 // Proceed to the next level to examine the exit condition expression.
3904 return ComputeBackedgeTakenCountFromExitCond(L, ExitBr->getCondition(),
3905 ExitBr->getSuccessor(0),
3906 ExitBr->getSuccessor(1));
3909 /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
3910 /// backedge of the specified loop will execute if its exit condition
3911 /// were a conditional branch of ExitCond, TBB, and FBB.
3912 ScalarEvolution::BackedgeTakenInfo
3913 ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
3917 // Check if the controlling expression for this loop is an And or Or.
3918 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
3919 if (BO->getOpcode() == Instruction::And) {
3920 // Recurse on the operands of the and.
3921 BackedgeTakenInfo BTI0 =
3922 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3923 BackedgeTakenInfo BTI1 =
3924 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3925 const SCEV *BECount = getCouldNotCompute();
3926 const SCEV *MaxBECount = getCouldNotCompute();
3927 if (L->contains(TBB)) {
3928 // Both conditions must be true for the loop to continue executing.
3929 // Choose the less conservative count.
3930 if (BTI0.Exact == getCouldNotCompute() ||
3931 BTI1.Exact == getCouldNotCompute())
3932 BECount = getCouldNotCompute();
3934 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3935 if (BTI0.Max == getCouldNotCompute())
3936 MaxBECount = BTI1.Max;
3937 else if (BTI1.Max == getCouldNotCompute())
3938 MaxBECount = BTI0.Max;
3940 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3942 // Both conditions must be true at the same time for the loop to exit.
3943 // For now, be conservative.
3944 assert(L->contains(FBB) && "Loop block has no successor in loop!");
3945 if (BTI0.Max == BTI1.Max)
3946 MaxBECount = BTI0.Max;
3947 if (BTI0.Exact == BTI1.Exact)
3948 BECount = BTI0.Exact;
3951 return BackedgeTakenInfo(BECount, MaxBECount);
3953 if (BO->getOpcode() == Instruction::Or) {
3954 // Recurse on the operands of the or.
3955 BackedgeTakenInfo BTI0 =
3956 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(0), TBB, FBB);
3957 BackedgeTakenInfo BTI1 =
3958 ComputeBackedgeTakenCountFromExitCond(L, BO->getOperand(1), TBB, FBB);
3959 const SCEV *BECount = getCouldNotCompute();
3960 const SCEV *MaxBECount = getCouldNotCompute();
3961 if (L->contains(FBB)) {
3962 // Both conditions must be false for the loop to continue executing.
3963 // Choose the less conservative count.
3964 if (BTI0.Exact == getCouldNotCompute() ||
3965 BTI1.Exact == getCouldNotCompute())
3966 BECount = getCouldNotCompute();
3968 BECount = getUMinFromMismatchedTypes(BTI0.Exact, BTI1.Exact);
3969 if (BTI0.Max == getCouldNotCompute())
3970 MaxBECount = BTI1.Max;
3971 else if (BTI1.Max == getCouldNotCompute())
3972 MaxBECount = BTI0.Max;
3974 MaxBECount = getUMinFromMismatchedTypes(BTI0.Max, BTI1.Max);
3976 // Both conditions must be false at the same time for the loop to exit.
3977 // For now, be conservative.
3978 assert(L->contains(TBB) && "Loop block has no successor in loop!");
3979 if (BTI0.Max == BTI1.Max)
3980 MaxBECount = BTI0.Max;
3981 if (BTI0.Exact == BTI1.Exact)
3982 BECount = BTI0.Exact;
3985 return BackedgeTakenInfo(BECount, MaxBECount);
3989 // With an icmp, it may be feasible to compute an exact backedge-taken count.
3990 // Proceed to the next level to examine the icmp.
3991 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
3992 return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
3994 // Check for a constant condition. These are normally stripped out by
3995 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
3996 // preserve the CFG and is temporarily leaving constant conditions
3998 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
3999 if (L->contains(FBB) == !CI->getZExtValue())
4000 // The backedge is always taken.
4001 return getCouldNotCompute();
4003 // The backedge is never taken.
4004 return getConstant(CI->getType(), 0);
4007 // If it's not an integer or pointer comparison then compute it the hard way.
4008 return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4011 static const SCEVAddRecExpr *
4012 isSimpleUnwrappingAddRec(const SCEV *S, const Loop *L) {
4013 const SCEVAddRecExpr *SA = dyn_cast<SCEVAddRecExpr>(S);
4015 // The SCEV must be an addrec of this loop.
4016 if (!SA || SA->getLoop() != L || !SA->isAffine())
4019 // The SCEV must be known to not wrap in some way to be interesting.
4020 if (!SA->hasNoUnsignedWrap() && !SA->hasNoSignedWrap())
4023 // The stride must be a constant so that we know if it is striding up or down.
4024 if (!isa<SCEVConstant>(SA->getOperand(1)))
4029 /// getMinusSCEVForExitTest - When considering an exit test for a loop with a
4030 /// "x != y" exit test, we turn this into a computation that evaluates x-y != 0,
4031 /// and this function returns the expression to use for x-y. We know and take
4032 /// advantage of the fact that this subtraction is only being used in a
4033 /// comparison by zero context.
4035 static const SCEV *getMinusSCEVForExitTest(const SCEV *LHS, const SCEV *RHS,
4036 const Loop *L, ScalarEvolution &SE) {
4037 // If either LHS or RHS is an AddRec SCEV (of this loop) that is known to not
4038 // wrap (either NSW or NUW), then we know that the value will either become
4039 // the other one (and thus the loop terminates), that the loop will terminate
4040 // through some other exit condition first, or that the loop has undefined
4041 // behavior. This information is useful when the addrec has a stride that is
4042 // != 1 or -1, because it means we can't "miss" the exit value.
4044 // In any of these three cases, it is safe to turn the exit condition into a
4045 // "counting down" AddRec (to zero) by subtracting the two inputs as normal,
4046 // but since we know that the "end cannot be missed" we can force the
4047 // resulting AddRec to be a NUW addrec. Since it is counting down, this means
4048 // that the AddRec *cannot* pass zero.
4050 // See if LHS and RHS are addrec's we can handle.
4051 const SCEVAddRecExpr *LHSA = isSimpleUnwrappingAddRec(LHS, L);
4052 const SCEVAddRecExpr *RHSA = isSimpleUnwrappingAddRec(RHS, L);
4054 // If neither addrec is interesting, just return a minus.
4055 if (RHSA == 0 && LHSA == 0)
4056 return SE.getMinusSCEV(LHS, RHS);
4058 // If only one of LHS and RHS are an AddRec of this loop, make sure it is LHS.
4059 if (RHSA && LHSA == 0) {
4060 // Safe because a-b === b-a for comparisons against zero.
4061 std::swap(LHS, RHS);
4062 std::swap(LHSA, RHSA);
4065 // Handle the case when only one is advancing in a non-overflowing way.
4067 // If RHS is loop varying, then we can't predict when LHS will cross it.
4068 if (!SE.isLoopInvariant(RHS, L))
4069 return SE.getMinusSCEV(LHS, RHS);
4071 // If LHS has a positive stride, then we compute RHS-LHS, because the loop
4072 // is counting up until it crosses RHS (which must be larger than LHS). If
4073 // it is negative, we compute LHS-RHS because we're counting down to RHS.
4074 const ConstantInt *Stride =
4075 cast<SCEVConstant>(LHSA->getOperand(1))->getValue();
4076 if (Stride->getValue().isNegative())
4077 std::swap(LHS, RHS);
4079 return SE.getMinusSCEV(RHS, LHS, true /*HasNUW*/);
4082 // If both LHS and RHS are interesting, we have something like:
4084 const ConstantInt *LHSStride =
4085 cast<SCEVConstant>(LHSA->getOperand(1))->getValue();
4086 const ConstantInt *RHSStride =
4087 cast<SCEVConstant>(RHSA->getOperand(1))->getValue();
4089 // If the strides are equal, then this is just a (complex) loop invariant
4090 // comparison of a and b.
4091 if (LHSStride == RHSStride)
4092 return SE.getMinusSCEV(LHSA->getStart(), RHSA->getStart());
4094 // If the signs of the strides differ, then the negative stride is counting
4095 // down to the positive stride.
4096 if (LHSStride->getValue().isNegative() != RHSStride->getValue().isNegative()){
4097 if (RHSStride->getValue().isNegative())
4098 std::swap(LHS, RHS);
4100 // If LHS's stride is smaller than RHS's stride, then "b" must be less than
4101 // "a" and "b" is RHS is counting up (catching up) to LHS. This is true
4102 // whether the strides are positive or negative.
4103 if (RHSStride->getValue().slt(LHSStride->getValue()))
4104 std::swap(LHS, RHS);
4107 return SE.getMinusSCEV(LHS, RHS, true /*HasNUW*/);
4110 /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of times the
4111 /// backedge of the specified loop will execute if its exit condition
4112 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4113 ScalarEvolution::BackedgeTakenInfo
4114 ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
4119 // If the condition was exit on true, convert the condition to exit on false
4120 ICmpInst::Predicate Cond;
4121 if (!L->contains(FBB))
4122 Cond = ExitCond->getPredicate();
4124 Cond = ExitCond->getInversePredicate();
4126 // Handle common loops like: for (X = "string"; *X; ++X)
4127 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4128 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4129 BackedgeTakenInfo ItCnt =
4130 ComputeLoadConstantCompareBackedgeTakenCount(LI, RHS, L, Cond);
4131 if (ItCnt.hasAnyInfo())
4135 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4136 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4138 // Try to evaluate any dependencies out of the loop.
4139 LHS = getSCEVAtScope(LHS, L);
4140 RHS = getSCEVAtScope(RHS, L);
4142 // At this point, we would like to compute how many iterations of the
4143 // loop the predicate will return true for these inputs.
4144 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
4145 // If there is a loop-invariant, force it into the RHS.
4146 std::swap(LHS, RHS);
4147 Cond = ICmpInst::getSwappedPredicate(Cond);
4150 // Simplify the operands before analyzing them.
4151 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4153 // If we have a comparison of a chrec against a constant, try to use value
4154 // ranges to answer this query.
4155 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4156 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4157 if (AddRec->getLoop() == L) {
4158 // Form the constant range.
4159 ConstantRange CompRange(
4160 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4162 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4163 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4167 case ICmpInst::ICMP_NE: { // while (X != Y)
4168 // Convert to: while (X-Y != 0)
4169 BackedgeTakenInfo BTI = HowFarToZero(getMinusSCEVForExitTest(LHS, RHS, L,
4171 if (BTI.hasAnyInfo()) return BTI;
4174 case ICmpInst::ICMP_EQ: { // while (X == Y)
4175 // Convert to: while (X-Y == 0)
4176 BackedgeTakenInfo BTI = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
4177 if (BTI.hasAnyInfo()) return BTI;
4180 case ICmpInst::ICMP_SLT: {
4181 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, true);
4182 if (BTI.hasAnyInfo()) return BTI;
4185 case ICmpInst::ICMP_SGT: {
4186 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4187 getNotSCEV(RHS), L, true);
4188 if (BTI.hasAnyInfo()) return BTI;
4191 case ICmpInst::ICMP_ULT: {
4192 BackedgeTakenInfo BTI = HowManyLessThans(LHS, RHS, L, false);
4193 if (BTI.hasAnyInfo()) return BTI;
4196 case ICmpInst::ICMP_UGT: {
4197 BackedgeTakenInfo BTI = HowManyLessThans(getNotSCEV(LHS),
4198 getNotSCEV(RHS), L, false);
4199 if (BTI.hasAnyInfo()) return BTI;
4204 dbgs() << "ComputeBackedgeTakenCount ";
4205 if (ExitCond->getOperand(0)->getType()->isUnsigned())
4206 dbgs() << "[unsigned] ";
4207 dbgs() << *LHS << " "
4208 << Instruction::getOpcodeName(Instruction::ICmp)
4209 << " " << *RHS << "\n";
4214 ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
4217 static ConstantInt *
4218 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
4219 ScalarEvolution &SE) {
4220 const SCEV *InVal = SE.getConstant(C);
4221 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
4222 assert(isa<SCEVConstant>(Val) &&
4223 "Evaluation of SCEV at constant didn't fold correctly?");
4224 return cast<SCEVConstant>(Val)->getValue();
4227 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
4228 /// and a GEP expression (missing the pointer index) indexing into it, return
4229 /// the addressed element of the initializer or null if the index expression is
4232 GetAddressedElementFromGlobal(GlobalVariable *GV,
4233 const std::vector<ConstantInt*> &Indices) {
4234 Constant *Init = GV->getInitializer();
4235 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
4236 uint64_t Idx = Indices[i]->getZExtValue();
4237 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
4238 assert(Idx < CS->getNumOperands() && "Bad struct index!");
4239 Init = cast<Constant>(CS->getOperand(Idx));
4240 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
4241 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
4242 Init = cast<Constant>(CA->getOperand(Idx));
4243 } else if (isa<ConstantAggregateZero>(Init)) {
4244 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
4245 assert(Idx < STy->getNumElements() && "Bad struct index!");
4246 Init = Constant::getNullValue(STy->getElementType(Idx));
4247 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
4248 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4249 Init = Constant::getNullValue(ATy->getElementType());
4251 llvm_unreachable("Unknown constant aggregate type!");
4255 return 0; // Unknown initializer type
4261 /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition of
4262 /// 'icmp op load X, cst', try to see if we can compute the backedge
4263 /// execution count.
4264 ScalarEvolution::BackedgeTakenInfo
4265 ScalarEvolution::ComputeLoadConstantCompareBackedgeTakenCount(
4269 ICmpInst::Predicate predicate) {
4270 if (LI->isVolatile()) return getCouldNotCompute();
4272 // Check to see if the loaded pointer is a getelementptr of a global.
4273 // TODO: Use SCEV instead of manually grubbing with GEPs.
4274 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4275 if (!GEP) return getCouldNotCompute();
4277 // Make sure that it is really a constant global we are gepping, with an
4278 // initializer, and make sure the first IDX is really 0.
4279 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4280 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4281 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4282 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4283 return getCouldNotCompute();
4285 // Okay, we allow one non-constant index into the GEP instruction.
4287 std::vector<ConstantInt*> Indexes;
4288 unsigned VarIdxNum = 0;
4289 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4290 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4291 Indexes.push_back(CI);
4292 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4293 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4294 VarIdx = GEP->getOperand(i);
4296 Indexes.push_back(0);
4299 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4300 // Check to see if X is a loop variant variable value now.
4301 const SCEV *Idx = getSCEV(VarIdx);
4302 Idx = getSCEVAtScope(Idx, L);
4304 // We can only recognize very limited forms of loop index expressions, in
4305 // particular, only affine AddRec's like {C1,+,C2}.
4306 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4307 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
4308 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4309 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4310 return getCouldNotCompute();
4312 unsigned MaxSteps = MaxBruteForceIterations;
4313 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4314 ConstantInt *ItCst = ConstantInt::get(
4315 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4316 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4318 // Form the GEP offset.
4319 Indexes[VarIdxNum] = Val;
4321 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4322 if (Result == 0) break; // Cannot compute!
4324 // Evaluate the condition for this iteration.
4325 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4326 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4327 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4329 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4330 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4333 ++NumArrayLenItCounts;
4334 return getConstant(ItCst); // Found terminating iteration!
4337 return getCouldNotCompute();
4341 /// CanConstantFold - Return true if we can constant fold an instruction of the
4342 /// specified type, assuming that all operands were constants.
4343 static bool CanConstantFold(const Instruction *I) {
4344 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4345 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
4348 if (const CallInst *CI = dyn_cast<CallInst>(I))
4349 if (const Function *F = CI->getCalledFunction())
4350 return canConstantFoldCallTo(F);
4354 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4355 /// in the loop that V is derived from. We allow arbitrary operations along the
4356 /// way, but the operands of an operation must either be constants or a value
4357 /// derived from a constant PHI. If this expression does not fit with these
4358 /// constraints, return null.
4359 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4360 // If this is not an instruction, or if this is an instruction outside of the
4361 // loop, it can't be derived from a loop PHI.
4362 Instruction *I = dyn_cast<Instruction>(V);
4363 if (I == 0 || !L->contains(I)) return 0;
4365 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4366 if (L->getHeader() == I->getParent())
4369 // We don't currently keep track of the control flow needed to evaluate
4370 // PHIs, so we cannot handle PHIs inside of loops.
4374 // If we won't be able to constant fold this expression even if the operands
4375 // are constants, return early.
4376 if (!CanConstantFold(I)) return 0;
4378 // Otherwise, we can evaluate this instruction if all of its operands are
4379 // constant or derived from a PHI node themselves.
4381 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4382 if (!isa<Constant>(I->getOperand(Op))) {
4383 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4384 if (P == 0) return 0; // Not evolving from PHI
4388 return 0; // Evolving from multiple different PHIs.
4391 // This is a expression evolving from a constant PHI!
4395 /// EvaluateExpression - Given an expression that passes the
4396 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4397 /// in the loop has the value PHIVal. If we can't fold this expression for some
4398 /// reason, return null.
4399 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4400 const TargetData *TD) {
4401 if (isa<PHINode>(V)) return PHIVal;
4402 if (Constant *C = dyn_cast<Constant>(V)) return C;
4403 Instruction *I = cast<Instruction>(V);
4405 std::vector<Constant*> Operands(I->getNumOperands());
4407 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4408 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4409 if (Operands[i] == 0) return 0;
4412 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4413 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4415 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4416 &Operands[0], Operands.size(), TD);
4419 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4420 /// in the header of its containing loop, we know the loop executes a
4421 /// constant number of times, and the PHI node is just a recurrence
4422 /// involving constants, fold it.
4424 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4427 std::map<PHINode*, Constant*>::const_iterator I =
4428 ConstantEvolutionLoopExitValue.find(PN);
4429 if (I != ConstantEvolutionLoopExitValue.end())
4432 if (BEs.ugt(MaxBruteForceIterations))
4433 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4435 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4437 // Since the loop is canonicalized, the PHI node must have two entries. One
4438 // entry must be a constant (coming in from outside of the loop), and the
4439 // second must be derived from the same PHI.
4440 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4441 Constant *StartCST =
4442 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4444 return RetVal = 0; // Must be a constant.
4446 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4447 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4448 !isa<Constant>(BEValue))
4449 return RetVal = 0; // Not derived from same PHI.
4451 // Execute the loop symbolically to determine the exit value.
4452 if (BEs.getActiveBits() >= 32)
4453 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4455 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4456 unsigned IterationNum = 0;
4457 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4458 if (IterationNum == NumIterations)
4459 return RetVal = PHIVal; // Got exit value!
4461 // Compute the value of the PHI node for the next iteration.
4462 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4463 if (NextPHI == PHIVal)
4464 return RetVal = NextPHI; // Stopped evolving!
4466 return 0; // Couldn't evaluate!
4471 /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute a
4472 /// constant number of times (the condition evolves only from constants),
4473 /// try to evaluate a few iterations of the loop until we get the exit
4474 /// condition gets a value of ExitWhen (true or false). If we cannot
4475 /// evaluate the trip count of the loop, return getCouldNotCompute().
4477 ScalarEvolution::ComputeBackedgeTakenCountExhaustively(const Loop *L,
4480 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4481 if (PN == 0) return getCouldNotCompute();
4483 // If the loop is canonicalized, the PHI will have exactly two entries.
4484 // That's the only form we support here.
4485 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4487 // One entry must be a constant (coming in from outside of the loop), and the
4488 // second must be derived from the same PHI.
4489 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4490 Constant *StartCST =
4491 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4492 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4494 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4495 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4496 !isa<Constant>(BEValue))
4497 return getCouldNotCompute(); // Not derived from same PHI.
4499 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4500 // the loop symbolically to determine when the condition gets a value of
4502 unsigned IterationNum = 0;
4503 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4504 for (Constant *PHIVal = StartCST;
4505 IterationNum != MaxIterations; ++IterationNum) {
4506 ConstantInt *CondVal =
4507 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4509 // Couldn't symbolically evaluate.
4510 if (!CondVal) return getCouldNotCompute();
4512 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4513 ++NumBruteForceTripCountsComputed;
4514 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4517 // Compute the value of the PHI node for the next iteration.
4518 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4519 if (NextPHI == 0 || NextPHI == PHIVal)
4520 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4524 // Too many iterations were needed to evaluate.
4525 return getCouldNotCompute();
4528 /// getSCEVAtScope - Return a SCEV expression for the specified value
4529 /// at the specified scope in the program. The L value specifies a loop
4530 /// nest to evaluate the expression at, where null is the top-level or a
4531 /// specified loop is immediately inside of the loop.
4533 /// This method can be used to compute the exit value for a variable defined
4534 /// in a loop by querying what the value will hold in the parent loop.
4536 /// In the case that a relevant loop exit value cannot be computed, the
4537 /// original value V is returned.
4538 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4539 // Check to see if we've folded this expression at this loop before.
4540 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4541 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4542 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4544 return Pair.first->second ? Pair.first->second : V;
4546 // Otherwise compute it.
4547 const SCEV *C = computeSCEVAtScope(V, L);
4548 ValuesAtScopes[V][L] = C;
4552 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4553 if (isa<SCEVConstant>(V)) return V;
4555 // If this instruction is evolved from a constant-evolving PHI, compute the
4556 // exit value from the loop without using SCEVs.
4557 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4558 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4559 const Loop *LI = (*this->LI)[I->getParent()];
4560 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4561 if (PHINode *PN = dyn_cast<PHINode>(I))
4562 if (PN->getParent() == LI->getHeader()) {
4563 // Okay, there is no closed form solution for the PHI node. Check
4564 // to see if the loop that contains it has a known backedge-taken
4565 // count. If so, we may be able to force computation of the exit
4567 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4568 if (const SCEVConstant *BTCC =
4569 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4570 // Okay, we know how many times the containing loop executes. If
4571 // this is a constant evolving PHI node, get the final value at
4572 // the specified iteration number.
4573 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4574 BTCC->getValue()->getValue(),
4576 if (RV) return getSCEV(RV);
4580 // Okay, this is an expression that we cannot symbolically evaluate
4581 // into a SCEV. Check to see if it's possible to symbolically evaluate
4582 // the arguments into constants, and if so, try to constant propagate the
4583 // result. This is particularly useful for computing loop exit values.
4584 if (CanConstantFold(I)) {
4585 SmallVector<Constant *, 4> Operands;
4586 bool MadeImprovement = false;
4587 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4588 Value *Op = I->getOperand(i);
4589 if (Constant *C = dyn_cast<Constant>(Op)) {
4590 Operands.push_back(C);
4594 // If any of the operands is non-constant and if they are
4595 // non-integer and non-pointer, don't even try to analyze them
4596 // with scev techniques.
4597 if (!isSCEVable(Op->getType()))
4600 const SCEV *OrigV = getSCEV(Op);
4601 const SCEV *OpV = getSCEVAtScope(OrigV, L);
4602 MadeImprovement |= OrigV != OpV;
4605 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
4607 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
4608 C = dyn_cast<Constant>(SU->getValue());
4610 if (C->getType() != Op->getType())
4611 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4615 Operands.push_back(C);
4618 // Check to see if getSCEVAtScope actually made an improvement.
4619 if (MadeImprovement) {
4621 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4622 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4623 Operands[0], Operands[1], TD);
4625 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4626 &Operands[0], Operands.size(), TD);
4633 // This is some other type of SCEVUnknown, just return it.
4637 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4638 // Avoid performing the look-up in the common case where the specified
4639 // expression has no loop-variant portions.
4640 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4641 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4642 if (OpAtScope != Comm->getOperand(i)) {
4643 // Okay, at least one of these operands is loop variant but might be
4644 // foldable. Build a new instance of the folded commutative expression.
4645 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4646 Comm->op_begin()+i);
4647 NewOps.push_back(OpAtScope);
4649 for (++i; i != e; ++i) {
4650 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4651 NewOps.push_back(OpAtScope);
4653 if (isa<SCEVAddExpr>(Comm))
4654 return getAddExpr(NewOps);
4655 if (isa<SCEVMulExpr>(Comm))
4656 return getMulExpr(NewOps);
4657 if (isa<SCEVSMaxExpr>(Comm))
4658 return getSMaxExpr(NewOps);
4659 if (isa<SCEVUMaxExpr>(Comm))
4660 return getUMaxExpr(NewOps);
4661 llvm_unreachable("Unknown commutative SCEV type!");
4664 // If we got here, all operands are loop invariant.
4668 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4669 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4670 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4671 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4672 return Div; // must be loop invariant
4673 return getUDivExpr(LHS, RHS);
4676 // If this is a loop recurrence for a loop that does not contain L, then we
4677 // are dealing with the final value computed by the loop.
4678 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4679 // First, attempt to evaluate each operand.
4680 // Avoid performing the look-up in the common case where the specified
4681 // expression has no loop-variant portions.
4682 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4683 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
4684 if (OpAtScope == AddRec->getOperand(i))
4687 // Okay, at least one of these operands is loop variant but might be
4688 // foldable. Build a new instance of the folded commutative expression.
4689 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
4690 AddRec->op_begin()+i);
4691 NewOps.push_back(OpAtScope);
4692 for (++i; i != e; ++i)
4693 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
4695 AddRec = cast<SCEVAddRecExpr>(getAddRecExpr(NewOps, AddRec->getLoop()));
4699 // If the scope is outside the addrec's loop, evaluate it by using the
4700 // loop exit value of the addrec.
4701 if (!AddRec->getLoop()->contains(L)) {
4702 // To evaluate this recurrence, we need to know how many times the AddRec
4703 // loop iterates. Compute this now.
4704 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4705 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4707 // Then, evaluate the AddRec.
4708 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4714 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4715 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4716 if (Op == Cast->getOperand())
4717 return Cast; // must be loop invariant
4718 return getZeroExtendExpr(Op, Cast->getType());
4721 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4722 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4723 if (Op == Cast->getOperand())
4724 return Cast; // must be loop invariant
4725 return getSignExtendExpr(Op, Cast->getType());
4728 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4729 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4730 if (Op == Cast->getOperand())
4731 return Cast; // must be loop invariant
4732 return getTruncateExpr(Op, Cast->getType());
4735 llvm_unreachable("Unknown SCEV type!");
4739 /// getSCEVAtScope - This is a convenience function which does
4740 /// getSCEVAtScope(getSCEV(V), L).
4741 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4742 return getSCEVAtScope(getSCEV(V), L);
4745 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4746 /// following equation:
4748 /// A * X = B (mod N)
4750 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4751 /// A and B isn't important.
4753 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
4754 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4755 ScalarEvolution &SE) {
4756 uint32_t BW = A.getBitWidth();
4757 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4758 assert(A != 0 && "A must be non-zero.");
4762 // The gcd of A and N may have only one prime factor: 2. The number of
4763 // trailing zeros in A is its multiplicity
4764 uint32_t Mult2 = A.countTrailingZeros();
4767 // 2. Check if B is divisible by D.
4769 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4770 // is not less than multiplicity of this prime factor for D.
4771 if (B.countTrailingZeros() < Mult2)
4772 return SE.getCouldNotCompute();
4774 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4777 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4778 // bit width during computations.
4779 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4780 APInt Mod(BW + 1, 0);
4781 Mod.setBit(BW - Mult2); // Mod = N / D
4782 APInt I = AD.multiplicativeInverse(Mod);
4784 // 4. Compute the minimum unsigned root of the equation:
4785 // I * (B / D) mod (N / D)
4786 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4788 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4790 return SE.getConstant(Result.trunc(BW));
4793 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4794 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4795 /// might be the same) or two SCEVCouldNotCompute objects.
4797 static std::pair<const SCEV *,const SCEV *>
4798 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4799 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4800 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4801 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4802 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4804 // We currently can only solve this if the coefficients are constants.
4805 if (!LC || !MC || !NC) {
4806 const SCEV *CNC = SE.getCouldNotCompute();
4807 return std::make_pair(CNC, CNC);
4810 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4811 const APInt &L = LC->getValue()->getValue();
4812 const APInt &M = MC->getValue()->getValue();
4813 const APInt &N = NC->getValue()->getValue();
4814 APInt Two(BitWidth, 2);
4815 APInt Four(BitWidth, 4);
4818 using namespace APIntOps;
4820 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4821 // The B coefficient is M-N/2
4825 // The A coefficient is N/2
4826 APInt A(N.sdiv(Two));
4828 // Compute the B^2-4ac term.
4831 SqrtTerm -= Four * (A * C);
4833 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4834 // integer value or else APInt::sqrt() will assert.
4835 APInt SqrtVal(SqrtTerm.sqrt());
4837 // Compute the two solutions for the quadratic formula.
4838 // The divisions must be performed as signed divisions.
4840 APInt TwoA( A << 1 );
4841 if (TwoA.isMinValue()) {
4842 const SCEV *CNC = SE.getCouldNotCompute();
4843 return std::make_pair(CNC, CNC);
4846 LLVMContext &Context = SE.getContext();
4848 ConstantInt *Solution1 =
4849 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
4850 ConstantInt *Solution2 =
4851 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
4853 return std::make_pair(SE.getConstant(Solution1),
4854 SE.getConstant(Solution2));
4855 } // end APIntOps namespace
4858 /// HowFarToZero - Return the number of times a backedge comparing the specified
4859 /// value to zero will execute. If not computable, return CouldNotCompute.
4860 ScalarEvolution::BackedgeTakenInfo
4861 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
4862 // If the value is a constant
4863 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4864 // If the value is already zero, the branch will execute zero times.
4865 if (C->getValue()->isZero()) return C;
4866 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4869 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
4870 if (!AddRec || AddRec->getLoop() != L)
4871 return getCouldNotCompute();
4873 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
4874 // the quadratic equation to solve it.
4875 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
4876 std::pair<const SCEV *,const SCEV *> Roots =
4877 SolveQuadraticEquation(AddRec, *this);
4878 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
4879 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
4882 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
4883 << " sol#2: " << *R2 << "\n";
4885 // Pick the smallest positive root value.
4886 if (ConstantInt *CB =
4887 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
4890 if (CB->getZExtValue() == false)
4891 std::swap(R1, R2); // R1 is the minimum root now.
4893 // We can only use this value if the chrec ends up with an exact zero
4894 // value at this index. When solving for "X*X != 5", for example, we
4895 // should not accept a root of 2.
4896 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
4898 return R1; // We found a quadratic root!
4901 return getCouldNotCompute();
4904 // Otherwise we can only handle this if it is affine.
4905 if (!AddRec->isAffine())
4906 return getCouldNotCompute();
4908 // If this is an affine expression, the execution count of this branch is
4909 // the minimum unsigned root of the following equation:
4911 // Start + Step*N = 0 (mod 2^BW)
4915 // Step*N = -Start (mod 2^BW)
4917 // where BW is the common bit width of Start and Step.
4919 // Get the initial value for the loop.
4920 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
4921 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
4923 // If the AddRec is NUW, then (in an unsigned sense) it cannot be counting up
4924 // to wrap to 0, it must be counting down to equal 0. Also, while counting
4925 // down, it cannot "miss" 0 (which would cause it to wrap), regardless of what
4926 // the stride is. As such, NUW addrec's will always become zero in
4927 // "start / -stride" steps, and we know that the division is exact.
4928 if (AddRec->hasNoUnsignedWrap())
4929 // FIXME: We really want an "isexact" bit for udiv.
4930 return getUDivExpr(Start, getNegativeSCEV(Step));
4932 // For now we handle only constant steps.
4933 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
4935 return getCouldNotCompute();
4937 // First, handle unitary steps.
4938 if (StepC->getValue()->equalsInt(1)) // 1*N = -Start (mod 2^BW), so:
4939 return getNegativeSCEV(Start); // N = -Start (as unsigned)
4941 if (StepC->getValue()->isAllOnesValue()) // -1*N = -Start (mod 2^BW), so:
4942 return Start; // N = Start (as unsigned)
4944 // Then, try to solve the above equation provided that Start is constant.
4945 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
4946 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
4947 -StartC->getValue()->getValue(),
4949 return getCouldNotCompute();
4952 /// HowFarToNonZero - Return the number of times a backedge checking the
4953 /// specified value for nonzero will execute. If not computable, return
4955 ScalarEvolution::BackedgeTakenInfo
4956 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
4957 // Loops that look like: while (X == 0) are very strange indeed. We don't
4958 // handle them yet except for the trivial case. This could be expanded in the
4959 // future as needed.
4961 // If the value is a constant, check to see if it is known to be non-zero
4962 // already. If so, the backedge will execute zero times.
4963 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
4964 if (!C->getValue()->isNullValue())
4965 return getConstant(C->getType(), 0);
4966 return getCouldNotCompute(); // Otherwise it will loop infinitely.
4969 // We could implement others, but I really doubt anyone writes loops like
4970 // this, and if they did, they would already be constant folded.
4971 return getCouldNotCompute();
4974 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
4975 /// (which may not be an immediate predecessor) which has exactly one
4976 /// successor from which BB is reachable, or null if no such block is
4979 std::pair<BasicBlock *, BasicBlock *>
4980 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
4981 // If the block has a unique predecessor, then there is no path from the
4982 // predecessor to the block that does not go through the direct edge
4983 // from the predecessor to the block.
4984 if (BasicBlock *Pred = BB->getSinglePredecessor())
4985 return std::make_pair(Pred, BB);
4987 // A loop's header is defined to be a block that dominates the loop.
4988 // If the header has a unique predecessor outside the loop, it must be
4989 // a block that has exactly one successor that can reach the loop.
4990 if (Loop *L = LI->getLoopFor(BB))
4991 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
4993 return std::pair<BasicBlock *, BasicBlock *>();
4996 /// HasSameValue - SCEV structural equivalence is usually sufficient for
4997 /// testing whether two expressions are equal, however for the purposes of
4998 /// looking for a condition guarding a loop, it can be useful to be a little
4999 /// more general, since a front-end may have replicated the controlling
5002 static bool HasSameValue(const SCEV *A, const SCEV *B) {
5003 // Quick check to see if they are the same SCEV.
5004 if (A == B) return true;
5006 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
5007 // two different instructions with the same value. Check for this case.
5008 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
5009 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
5010 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
5011 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
5012 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
5015 // Otherwise assume they may have a different value.
5019 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
5020 /// predicate Pred. Return true iff any changes were made.
5022 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
5023 const SCEV *&LHS, const SCEV *&RHS) {
5024 bool Changed = false;
5026 // Canonicalize a constant to the right side.
5027 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
5028 // Check for both operands constant.
5029 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
5030 if (ConstantExpr::getICmp(Pred,
5032 RHSC->getValue())->isNullValue())
5033 goto trivially_false;
5035 goto trivially_true;
5037 // Otherwise swap the operands to put the constant on the right.
5038 std::swap(LHS, RHS);
5039 Pred = ICmpInst::getSwappedPredicate(Pred);
5043 // If we're comparing an addrec with a value which is loop-invariant in the
5044 // addrec's loop, put the addrec on the left. Also make a dominance check,
5045 // as both operands could be addrecs loop-invariant in each other's loop.
5046 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
5047 const Loop *L = AR->getLoop();
5048 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
5049 std::swap(LHS, RHS);
5050 Pred = ICmpInst::getSwappedPredicate(Pred);
5055 // If there's a constant operand, canonicalize comparisons with boundary
5056 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
5057 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
5058 const APInt &RA = RC->getValue()->getValue();
5060 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5061 case ICmpInst::ICMP_EQ:
5062 case ICmpInst::ICMP_NE:
5064 case ICmpInst::ICMP_UGE:
5065 if ((RA - 1).isMinValue()) {
5066 Pred = ICmpInst::ICMP_NE;
5067 RHS = getConstant(RA - 1);
5071 if (RA.isMaxValue()) {
5072 Pred = ICmpInst::ICMP_EQ;
5076 if (RA.isMinValue()) goto trivially_true;
5078 Pred = ICmpInst::ICMP_UGT;
5079 RHS = getConstant(RA - 1);
5082 case ICmpInst::ICMP_ULE:
5083 if ((RA + 1).isMaxValue()) {
5084 Pred = ICmpInst::ICMP_NE;
5085 RHS = getConstant(RA + 1);
5089 if (RA.isMinValue()) {
5090 Pred = ICmpInst::ICMP_EQ;
5094 if (RA.isMaxValue()) goto trivially_true;
5096 Pred = ICmpInst::ICMP_ULT;
5097 RHS = getConstant(RA + 1);
5100 case ICmpInst::ICMP_SGE:
5101 if ((RA - 1).isMinSignedValue()) {
5102 Pred = ICmpInst::ICMP_NE;
5103 RHS = getConstant(RA - 1);
5107 if (RA.isMaxSignedValue()) {
5108 Pred = ICmpInst::ICMP_EQ;
5112 if (RA.isMinSignedValue()) goto trivially_true;
5114 Pred = ICmpInst::ICMP_SGT;
5115 RHS = getConstant(RA - 1);
5118 case ICmpInst::ICMP_SLE:
5119 if ((RA + 1).isMaxSignedValue()) {
5120 Pred = ICmpInst::ICMP_NE;
5121 RHS = getConstant(RA + 1);
5125 if (RA.isMinSignedValue()) {
5126 Pred = ICmpInst::ICMP_EQ;
5130 if (RA.isMaxSignedValue()) goto trivially_true;
5132 Pred = ICmpInst::ICMP_SLT;
5133 RHS = getConstant(RA + 1);
5136 case ICmpInst::ICMP_UGT:
5137 if (RA.isMinValue()) {
5138 Pred = ICmpInst::ICMP_NE;
5142 if ((RA + 1).isMaxValue()) {
5143 Pred = ICmpInst::ICMP_EQ;
5144 RHS = getConstant(RA + 1);
5148 if (RA.isMaxValue()) goto trivially_false;
5150 case ICmpInst::ICMP_ULT:
5151 if (RA.isMaxValue()) {
5152 Pred = ICmpInst::ICMP_NE;
5156 if ((RA - 1).isMinValue()) {
5157 Pred = ICmpInst::ICMP_EQ;
5158 RHS = getConstant(RA - 1);
5162 if (RA.isMinValue()) goto trivially_false;
5164 case ICmpInst::ICMP_SGT:
5165 if (RA.isMinSignedValue()) {
5166 Pred = ICmpInst::ICMP_NE;
5170 if ((RA + 1).isMaxSignedValue()) {
5171 Pred = ICmpInst::ICMP_EQ;
5172 RHS = getConstant(RA + 1);
5176 if (RA.isMaxSignedValue()) goto trivially_false;
5178 case ICmpInst::ICMP_SLT:
5179 if (RA.isMaxSignedValue()) {
5180 Pred = ICmpInst::ICMP_NE;
5184 if ((RA - 1).isMinSignedValue()) {
5185 Pred = ICmpInst::ICMP_EQ;
5186 RHS = getConstant(RA - 1);
5190 if (RA.isMinSignedValue()) goto trivially_false;
5195 // Check for obvious equality.
5196 if (HasSameValue(LHS, RHS)) {
5197 if (ICmpInst::isTrueWhenEqual(Pred))
5198 goto trivially_true;
5199 if (ICmpInst::isFalseWhenEqual(Pred))
5200 goto trivially_false;
5203 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
5204 // adding or subtracting 1 from one of the operands.
5206 case ICmpInst::ICMP_SLE:
5207 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
5208 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5209 /*HasNUW=*/false, /*HasNSW=*/true);
5210 Pred = ICmpInst::ICMP_SLT;
5212 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
5213 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5214 /*HasNUW=*/false, /*HasNSW=*/true);
5215 Pred = ICmpInst::ICMP_SLT;
5219 case ICmpInst::ICMP_SGE:
5220 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
5221 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5222 /*HasNUW=*/false, /*HasNSW=*/true);
5223 Pred = ICmpInst::ICMP_SGT;
5225 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
5226 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5227 /*HasNUW=*/false, /*HasNSW=*/true);
5228 Pred = ICmpInst::ICMP_SGT;
5232 case ICmpInst::ICMP_ULE:
5233 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
5234 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5235 /*HasNUW=*/true, /*HasNSW=*/false);
5236 Pred = ICmpInst::ICMP_ULT;
5238 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
5239 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5240 /*HasNUW=*/true, /*HasNSW=*/false);
5241 Pred = ICmpInst::ICMP_ULT;
5245 case ICmpInst::ICMP_UGE:
5246 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
5247 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5248 /*HasNUW=*/true, /*HasNSW=*/false);
5249 Pred = ICmpInst::ICMP_UGT;
5251 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
5252 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5253 /*HasNUW=*/true, /*HasNSW=*/false);
5254 Pred = ICmpInst::ICMP_UGT;
5262 // TODO: More simplifications are possible here.
5268 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5269 Pred = ICmpInst::ICMP_EQ;
5274 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5275 Pred = ICmpInst::ICMP_NE;
5279 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
5280 return getSignedRange(S).getSignedMax().isNegative();
5283 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5284 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5287 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5288 return !getSignedRange(S).getSignedMin().isNegative();
5291 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5292 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5295 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5296 return isKnownNegative(S) || isKnownPositive(S);
5299 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5300 const SCEV *LHS, const SCEV *RHS) {
5301 // Canonicalize the inputs first.
5302 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5304 // If LHS or RHS is an addrec, check to see if the condition is true in
5305 // every iteration of the loop.
5306 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5307 if (isLoopEntryGuardedByCond(
5308 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5309 isLoopBackedgeGuardedByCond(
5310 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5312 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5313 if (isLoopEntryGuardedByCond(
5314 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5315 isLoopBackedgeGuardedByCond(
5316 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5319 // Otherwise see what can be done with known constant ranges.
5320 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5324 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5325 const SCEV *LHS, const SCEV *RHS) {
5326 if (HasSameValue(LHS, RHS))
5327 return ICmpInst::isTrueWhenEqual(Pred);
5329 // This code is split out from isKnownPredicate because it is called from
5330 // within isLoopEntryGuardedByCond.
5333 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5335 case ICmpInst::ICMP_SGT:
5336 Pred = ICmpInst::ICMP_SLT;
5337 std::swap(LHS, RHS);
5338 case ICmpInst::ICMP_SLT: {
5339 ConstantRange LHSRange = getSignedRange(LHS);
5340 ConstantRange RHSRange = getSignedRange(RHS);
5341 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5343 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5347 case ICmpInst::ICMP_SGE:
5348 Pred = ICmpInst::ICMP_SLE;
5349 std::swap(LHS, RHS);
5350 case ICmpInst::ICMP_SLE: {
5351 ConstantRange LHSRange = getSignedRange(LHS);
5352 ConstantRange RHSRange = getSignedRange(RHS);
5353 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5355 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5359 case ICmpInst::ICMP_UGT:
5360 Pred = ICmpInst::ICMP_ULT;
5361 std::swap(LHS, RHS);
5362 case ICmpInst::ICMP_ULT: {
5363 ConstantRange LHSRange = getUnsignedRange(LHS);
5364 ConstantRange RHSRange = getUnsignedRange(RHS);
5365 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5367 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5371 case ICmpInst::ICMP_UGE:
5372 Pred = ICmpInst::ICMP_ULE;
5373 std::swap(LHS, RHS);
5374 case ICmpInst::ICMP_ULE: {
5375 ConstantRange LHSRange = getUnsignedRange(LHS);
5376 ConstantRange RHSRange = getUnsignedRange(RHS);
5377 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5379 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5383 case ICmpInst::ICMP_NE: {
5384 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5386 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5389 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5390 if (isKnownNonZero(Diff))
5394 case ICmpInst::ICMP_EQ:
5395 // The check at the top of the function catches the case where
5396 // the values are known to be equal.
5402 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5403 /// protected by a conditional between LHS and RHS. This is used to
5404 /// to eliminate casts.
5406 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5407 ICmpInst::Predicate Pred,
5408 const SCEV *LHS, const SCEV *RHS) {
5409 // Interpret a null as meaning no loop, where there is obviously no guard
5410 // (interprocedural conditions notwithstanding).
5411 if (!L) return true;
5413 BasicBlock *Latch = L->getLoopLatch();
5417 BranchInst *LoopContinuePredicate =
5418 dyn_cast<BranchInst>(Latch->getTerminator());
5419 if (!LoopContinuePredicate ||
5420 LoopContinuePredicate->isUnconditional())
5423 return isImpliedCond(Pred, LHS, RHS,
5424 LoopContinuePredicate->getCondition(),
5425 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
5428 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
5429 /// by a conditional between LHS and RHS. This is used to help avoid max
5430 /// expressions in loop trip counts, and to eliminate casts.
5432 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
5433 ICmpInst::Predicate Pred,
5434 const SCEV *LHS, const SCEV *RHS) {
5435 // Interpret a null as meaning no loop, where there is obviously no guard
5436 // (interprocedural conditions notwithstanding).
5437 if (!L) return false;
5439 // Starting at the loop predecessor, climb up the predecessor chain, as long
5440 // as there are predecessors that can be found that have unique successors
5441 // leading to the original header.
5442 for (std::pair<BasicBlock *, BasicBlock *>
5443 Pair(L->getLoopPredecessor(), L->getHeader());
5445 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
5447 BranchInst *LoopEntryPredicate =
5448 dyn_cast<BranchInst>(Pair.first->getTerminator());
5449 if (!LoopEntryPredicate ||
5450 LoopEntryPredicate->isUnconditional())
5453 if (isImpliedCond(Pred, LHS, RHS,
5454 LoopEntryPredicate->getCondition(),
5455 LoopEntryPredicate->getSuccessor(0) != Pair.second))
5462 /// isImpliedCond - Test whether the condition described by Pred, LHS,
5463 /// and RHS is true whenever the given Cond value evaluates to true.
5464 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
5465 const SCEV *LHS, const SCEV *RHS,
5466 Value *FoundCondValue,
5468 // Recursively handle And and Or conditions.
5469 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
5470 if (BO->getOpcode() == Instruction::And) {
5472 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5473 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5474 } else if (BO->getOpcode() == Instruction::Or) {
5476 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5477 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5481 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
5482 if (!ICI) return false;
5484 // Bail if the ICmp's operands' types are wider than the needed type
5485 // before attempting to call getSCEV on them. This avoids infinite
5486 // recursion, since the analysis of widening casts can require loop
5487 // exit condition information for overflow checking, which would
5489 if (getTypeSizeInBits(LHS->getType()) <
5490 getTypeSizeInBits(ICI->getOperand(0)->getType()))
5493 // Now that we found a conditional branch that dominates the loop, check to
5494 // see if it is the comparison we are looking for.
5495 ICmpInst::Predicate FoundPred;
5497 FoundPred = ICI->getInversePredicate();
5499 FoundPred = ICI->getPredicate();
5501 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
5502 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
5504 // Balance the types. The case where FoundLHS' type is wider than
5505 // LHS' type is checked for above.
5506 if (getTypeSizeInBits(LHS->getType()) >
5507 getTypeSizeInBits(FoundLHS->getType())) {
5508 if (CmpInst::isSigned(Pred)) {
5509 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
5510 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
5512 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
5513 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
5517 // Canonicalize the query to match the way instcombine will have
5518 // canonicalized the comparison.
5519 if (SimplifyICmpOperands(Pred, LHS, RHS))
5521 return CmpInst::isTrueWhenEqual(Pred);
5522 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
5523 if (FoundLHS == FoundRHS)
5524 return CmpInst::isFalseWhenEqual(Pred);
5526 // Check to see if we can make the LHS or RHS match.
5527 if (LHS == FoundRHS || RHS == FoundLHS) {
5528 if (isa<SCEVConstant>(RHS)) {
5529 std::swap(FoundLHS, FoundRHS);
5530 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
5532 std::swap(LHS, RHS);
5533 Pred = ICmpInst::getSwappedPredicate(Pred);
5537 // Check whether the found predicate is the same as the desired predicate.
5538 if (FoundPred == Pred)
5539 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
5541 // Check whether swapping the found predicate makes it the same as the
5542 // desired predicate.
5543 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
5544 if (isa<SCEVConstant>(RHS))
5545 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
5547 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
5548 RHS, LHS, FoundLHS, FoundRHS);
5551 // Check whether the actual condition is beyond sufficient.
5552 if (FoundPred == ICmpInst::ICMP_EQ)
5553 if (ICmpInst::isTrueWhenEqual(Pred))
5554 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
5556 if (Pred == ICmpInst::ICMP_NE)
5557 if (!ICmpInst::isTrueWhenEqual(FoundPred))
5558 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
5561 // Otherwise assume the worst.
5565 /// isImpliedCondOperands - Test whether the condition described by Pred,
5566 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
5567 /// and FoundRHS is true.
5568 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
5569 const SCEV *LHS, const SCEV *RHS,
5570 const SCEV *FoundLHS,
5571 const SCEV *FoundRHS) {
5572 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
5573 FoundLHS, FoundRHS) ||
5574 // ~x < ~y --> x > y
5575 isImpliedCondOperandsHelper(Pred, LHS, RHS,
5576 getNotSCEV(FoundRHS),
5577 getNotSCEV(FoundLHS));
5580 /// isImpliedCondOperandsHelper - Test whether the condition described by
5581 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
5582 /// FoundLHS, and FoundRHS is true.
5584 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
5585 const SCEV *LHS, const SCEV *RHS,
5586 const SCEV *FoundLHS,
5587 const SCEV *FoundRHS) {
5589 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5590 case ICmpInst::ICMP_EQ:
5591 case ICmpInst::ICMP_NE:
5592 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5595 case ICmpInst::ICMP_SLT:
5596 case ICmpInst::ICMP_SLE:
5597 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5598 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5601 case ICmpInst::ICMP_SGT:
5602 case ICmpInst::ICMP_SGE:
5603 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5604 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5607 case ICmpInst::ICMP_ULT:
5608 case ICmpInst::ICMP_ULE:
5609 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5610 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5613 case ICmpInst::ICMP_UGT:
5614 case ICmpInst::ICMP_UGE:
5615 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5616 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5624 /// getBECount - Subtract the end and start values and divide by the step,
5625 /// rounding up, to get the number of times the backedge is executed. Return
5626 /// CouldNotCompute if an intermediate computation overflows.
5627 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5631 assert(!isKnownNegative(Step) &&
5632 "This code doesn't handle negative strides yet!");
5634 const Type *Ty = Start->getType();
5635 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
5636 const SCEV *Diff = getMinusSCEV(End, Start);
5637 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5639 // Add an adjustment to the difference between End and Start so that
5640 // the division will effectively round up.
5641 const SCEV *Add = getAddExpr(Diff, RoundUp);
5644 // Check Add for unsigned overflow.
5645 // TODO: More sophisticated things could be done here.
5646 const Type *WideTy = IntegerType::get(getContext(),
5647 getTypeSizeInBits(Ty) + 1);
5648 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5649 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5650 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5651 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5652 return getCouldNotCompute();
5655 return getUDivExpr(Add, Step);
5658 /// HowManyLessThans - Return the number of times a backedge containing the
5659 /// specified less-than comparison will execute. If not computable, return
5660 /// CouldNotCompute.
5661 ScalarEvolution::BackedgeTakenInfo
5662 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5663 const Loop *L, bool isSigned) {
5664 // Only handle: "ADDREC < LoopInvariant".
5665 if (!isLoopInvariant(RHS, L)) return getCouldNotCompute();
5667 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5668 if (!AddRec || AddRec->getLoop() != L)
5669 return getCouldNotCompute();
5671 // Check to see if we have a flag which makes analysis easy.
5672 bool NoWrap = isSigned ? AddRec->hasNoSignedWrap() :
5673 AddRec->hasNoUnsignedWrap();
5675 if (AddRec->isAffine()) {
5676 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5677 const SCEV *Step = AddRec->getStepRecurrence(*this);
5680 return getCouldNotCompute();
5681 if (Step->isOne()) {
5682 // With unit stride, the iteration never steps past the limit value.
5683 } else if (isKnownPositive(Step)) {
5684 // Test whether a positive iteration can step past the limit
5685 // value and past the maximum value for its type in a single step.
5686 // Note that it's not sufficient to check NoWrap here, because even
5687 // though the value after a wrap is undefined, it's not undefined
5688 // behavior, so if wrap does occur, the loop could either terminate or
5689 // loop infinitely, but in either case, the loop is guaranteed to
5690 // iterate at least until the iteration where the wrapping occurs.
5691 const SCEV *One = getConstant(Step->getType(), 1);
5693 APInt Max = APInt::getSignedMaxValue(BitWidth);
5694 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5695 .slt(getSignedRange(RHS).getSignedMax()))
5696 return getCouldNotCompute();
5698 APInt Max = APInt::getMaxValue(BitWidth);
5699 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5700 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5701 return getCouldNotCompute();
5704 // TODO: Handle negative strides here and below.
5705 return getCouldNotCompute();
5707 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5708 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5709 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5710 // treat m-n as signed nor unsigned due to overflow possibility.
5712 // First, we get the value of the LHS in the first iteration: n
5713 const SCEV *Start = AddRec->getOperand(0);
5715 // Determine the minimum constant start value.
5716 const SCEV *MinStart = getConstant(isSigned ?
5717 getSignedRange(Start).getSignedMin() :
5718 getUnsignedRange(Start).getUnsignedMin());
5720 // If we know that the condition is true in order to enter the loop,
5721 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5722 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5723 // the division must round up.
5724 const SCEV *End = RHS;
5725 if (!isLoopEntryGuardedByCond(L,
5726 isSigned ? ICmpInst::ICMP_SLT :
5728 getMinusSCEV(Start, Step), RHS))
5729 End = isSigned ? getSMaxExpr(RHS, Start)
5730 : getUMaxExpr(RHS, Start);
5732 // Determine the maximum constant end value.
5733 const SCEV *MaxEnd = getConstant(isSigned ?
5734 getSignedRange(End).getSignedMax() :
5735 getUnsignedRange(End).getUnsignedMax());
5737 // If MaxEnd is within a step of the maximum integer value in its type,
5738 // adjust it down to the minimum value which would produce the same effect.
5739 // This allows the subsequent ceiling division of (N+(step-1))/step to
5740 // compute the correct value.
5741 const SCEV *StepMinusOne = getMinusSCEV(Step,
5742 getConstant(Step->getType(), 1));
5745 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5748 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5751 // Finally, we subtract these two values and divide, rounding up, to get
5752 // the number of times the backedge is executed.
5753 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5755 // The maximum backedge count is similar, except using the minimum start
5756 // value and the maximum end value.
5757 const SCEV *MaxBECount = getBECount(MinStart, MaxEnd, Step, NoWrap);
5759 return BackedgeTakenInfo(BECount, MaxBECount);
5762 return getCouldNotCompute();
5765 /// getNumIterationsInRange - Return the number of iterations of this loop that
5766 /// produce values in the specified constant range. Another way of looking at
5767 /// this is that it returns the first iteration number where the value is not in
5768 /// the condition, thus computing the exit count. If the iteration count can't
5769 /// be computed, an instance of SCEVCouldNotCompute is returned.
5770 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5771 ScalarEvolution &SE) const {
5772 if (Range.isFullSet()) // Infinite loop.
5773 return SE.getCouldNotCompute();
5775 // If the start is a non-zero constant, shift the range to simplify things.
5776 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5777 if (!SC->getValue()->isZero()) {
5778 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5779 Operands[0] = SE.getConstant(SC->getType(), 0);
5780 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop());
5781 if (const SCEVAddRecExpr *ShiftedAddRec =
5782 dyn_cast<SCEVAddRecExpr>(Shifted))
5783 return ShiftedAddRec->getNumIterationsInRange(
5784 Range.subtract(SC->getValue()->getValue()), SE);
5785 // This is strange and shouldn't happen.
5786 return SE.getCouldNotCompute();
5789 // The only time we can solve this is when we have all constant indices.
5790 // Otherwise, we cannot determine the overflow conditions.
5791 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5792 if (!isa<SCEVConstant>(getOperand(i)))
5793 return SE.getCouldNotCompute();
5796 // Okay at this point we know that all elements of the chrec are constants and
5797 // that the start element is zero.
5799 // First check to see if the range contains zero. If not, the first
5801 unsigned BitWidth = SE.getTypeSizeInBits(getType());
5802 if (!Range.contains(APInt(BitWidth, 0)))
5803 return SE.getConstant(getType(), 0);
5806 // If this is an affine expression then we have this situation:
5807 // Solve {0,+,A} in Range === Ax in Range
5809 // We know that zero is in the range. If A is positive then we know that
5810 // the upper value of the range must be the first possible exit value.
5811 // If A is negative then the lower of the range is the last possible loop
5812 // value. Also note that we already checked for a full range.
5813 APInt One(BitWidth,1);
5814 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
5815 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
5817 // The exit value should be (End+A)/A.
5818 APInt ExitVal = (End + A).udiv(A);
5819 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
5821 // Evaluate at the exit value. If we really did fall out of the valid
5822 // range, then we computed our trip count, otherwise wrap around or other
5823 // things must have happened.
5824 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
5825 if (Range.contains(Val->getValue()))
5826 return SE.getCouldNotCompute(); // Something strange happened
5828 // Ensure that the previous value is in the range. This is a sanity check.
5829 assert(Range.contains(
5830 EvaluateConstantChrecAtConstant(this,
5831 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
5832 "Linear scev computation is off in a bad way!");
5833 return SE.getConstant(ExitValue);
5834 } else if (isQuadratic()) {
5835 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
5836 // quadratic equation to solve it. To do this, we must frame our problem in
5837 // terms of figuring out when zero is crossed, instead of when
5838 // Range.getUpper() is crossed.
5839 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
5840 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
5841 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop());
5843 // Next, solve the constructed addrec
5844 std::pair<const SCEV *,const SCEV *> Roots =
5845 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
5846 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5847 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5849 // Pick the smallest positive root value.
5850 if (ConstantInt *CB =
5851 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
5852 R1->getValue(), R2->getValue()))) {
5853 if (CB->getZExtValue() == false)
5854 std::swap(R1, R2); // R1 is the minimum root now.
5856 // Make sure the root is not off by one. The returned iteration should
5857 // not be in the range, but the previous one should be. When solving
5858 // for "X*X < 5", for example, we should not return a root of 2.
5859 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
5862 if (Range.contains(R1Val->getValue())) {
5863 // The next iteration must be out of the range...
5864 ConstantInt *NextVal =
5865 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
5867 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5868 if (!Range.contains(R1Val->getValue()))
5869 return SE.getConstant(NextVal);
5870 return SE.getCouldNotCompute(); // Something strange happened
5873 // If R1 was not in the range, then it is a good return value. Make
5874 // sure that R1-1 WAS in the range though, just in case.
5875 ConstantInt *NextVal =
5876 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
5877 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
5878 if (Range.contains(R1Val->getValue()))
5880 return SE.getCouldNotCompute(); // Something strange happened
5885 return SE.getCouldNotCompute();
5890 //===----------------------------------------------------------------------===//
5891 // SCEVCallbackVH Class Implementation
5892 //===----------------------------------------------------------------------===//
5894 void ScalarEvolution::SCEVCallbackVH::deleted() {
5895 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5896 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
5897 SE->ConstantEvolutionLoopExitValue.erase(PN);
5898 SE->ValueExprMap.erase(getValPtr());
5899 // this now dangles!
5902 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
5903 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
5905 // Forget all the expressions associated with users of the old value,
5906 // so that future queries will recompute the expressions using the new
5908 Value *Old = getValPtr();
5909 SmallVector<User *, 16> Worklist;
5910 SmallPtrSet<User *, 8> Visited;
5911 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
5913 Worklist.push_back(*UI);
5914 while (!Worklist.empty()) {
5915 User *U = Worklist.pop_back_val();
5916 // Deleting the Old value will cause this to dangle. Postpone
5917 // that until everything else is done.
5920 if (!Visited.insert(U))
5922 if (PHINode *PN = dyn_cast<PHINode>(U))
5923 SE->ConstantEvolutionLoopExitValue.erase(PN);
5924 SE->ValueExprMap.erase(U);
5925 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
5927 Worklist.push_back(*UI);
5929 // Delete the Old value.
5930 if (PHINode *PN = dyn_cast<PHINode>(Old))
5931 SE->ConstantEvolutionLoopExitValue.erase(PN);
5932 SE->ValueExprMap.erase(Old);
5933 // this now dangles!
5936 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
5937 : CallbackVH(V), SE(se) {}
5939 //===----------------------------------------------------------------------===//
5940 // ScalarEvolution Class Implementation
5941 //===----------------------------------------------------------------------===//
5943 ScalarEvolution::ScalarEvolution()
5944 : FunctionPass(ID), FirstUnknown(0) {
5945 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
5948 bool ScalarEvolution::runOnFunction(Function &F) {
5950 LI = &getAnalysis<LoopInfo>();
5951 TD = getAnalysisIfAvailable<TargetData>();
5952 DT = &getAnalysis<DominatorTree>();
5956 void ScalarEvolution::releaseMemory() {
5957 // Iterate through all the SCEVUnknown instances and call their
5958 // destructors, so that they release their references to their values.
5959 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
5963 ValueExprMap.clear();
5964 BackedgeTakenCounts.clear();
5965 ConstantEvolutionLoopExitValue.clear();
5966 ValuesAtScopes.clear();
5967 LoopDispositions.clear();
5968 BlockDispositions.clear();
5969 UnsignedRanges.clear();
5970 SignedRanges.clear();
5971 UniqueSCEVs.clear();
5972 SCEVAllocator.Reset();
5975 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
5976 AU.setPreservesAll();
5977 AU.addRequiredTransitive<LoopInfo>();
5978 AU.addRequiredTransitive<DominatorTree>();
5981 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
5982 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
5985 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
5987 // Print all inner loops first
5988 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
5989 PrintLoopInfo(OS, SE, *I);
5992 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
5995 SmallVector<BasicBlock *, 8> ExitBlocks;
5996 L->getExitBlocks(ExitBlocks);
5997 if (ExitBlocks.size() != 1)
5998 OS << "<multiple exits> ";
6000 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
6001 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
6003 OS << "Unpredictable backedge-taken count. ";
6008 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6011 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
6012 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
6014 OS << "Unpredictable max backedge-taken count. ";
6020 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
6021 // ScalarEvolution's implementation of the print method is to print
6022 // out SCEV values of all instructions that are interesting. Doing
6023 // this potentially causes it to create new SCEV objects though,
6024 // which technically conflicts with the const qualifier. This isn't
6025 // observable from outside the class though, so casting away the
6026 // const isn't dangerous.
6027 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6029 OS << "Classifying expressions for: ";
6030 WriteAsOperand(OS, F, /*PrintType=*/false);
6032 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
6033 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
6036 const SCEV *SV = SE.getSCEV(&*I);
6039 const Loop *L = LI->getLoopFor((*I).getParent());
6041 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
6048 OS << "\t\t" "Exits: ";
6049 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
6050 if (!SE.isLoopInvariant(ExitValue, L)) {
6051 OS << "<<Unknown>>";
6060 OS << "Determining loop execution counts for: ";
6061 WriteAsOperand(OS, F, /*PrintType=*/false);
6063 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
6064 PrintLoopInfo(OS, &SE, *I);
6067 ScalarEvolution::LoopDisposition
6068 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
6069 std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
6070 std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
6071 Values.insert(std::make_pair(L, LoopVariant));
6073 return Pair.first->second;
6075 LoopDisposition D = computeLoopDisposition(S, L);
6076 return LoopDispositions[S][L] = D;
6079 ScalarEvolution::LoopDisposition
6080 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
6081 switch (S->getSCEVType()) {
6083 return LoopInvariant;
6087 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
6088 case scAddRecExpr: {
6089 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6091 // If L is the addrec's loop, it's computable.
6092 if (AR->getLoop() == L)
6093 return LoopComputable;
6095 // Add recurrences are never invariant in the function-body (null loop).
6099 // This recurrence is variant w.r.t. L if L contains AR's loop.
6100 if (L->contains(AR->getLoop()))
6103 // This recurrence is invariant w.r.t. L if AR's loop contains L.
6104 if (AR->getLoop()->contains(L))
6105 return LoopInvariant;
6107 // This recurrence is variant w.r.t. L if any of its operands
6109 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
6111 if (!isLoopInvariant(*I, L))
6114 // Otherwise it's loop-invariant.
6115 return LoopInvariant;
6121 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6122 bool HasVarying = false;
6123 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6125 LoopDisposition D = getLoopDisposition(*I, L);
6126 if (D == LoopVariant)
6128 if (D == LoopComputable)
6131 return HasVarying ? LoopComputable : LoopInvariant;
6134 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6135 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
6136 if (LD == LoopVariant)
6138 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
6139 if (RD == LoopVariant)
6141 return (LD == LoopInvariant && RD == LoopInvariant) ?
6142 LoopInvariant : LoopComputable;
6145 // All non-instruction values are loop invariant. All instructions are loop
6146 // invariant if they are not contained in the specified loop.
6147 // Instructions are never considered invariant in the function body
6148 // (null loop) because they are defined within the "loop".
6149 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
6150 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
6151 return LoopInvariant;
6152 case scCouldNotCompute:
6153 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6157 llvm_unreachable("Unknown SCEV kind!");
6161 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
6162 return getLoopDisposition(S, L) == LoopInvariant;
6165 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
6166 return getLoopDisposition(S, L) == LoopComputable;
6169 ScalarEvolution::BlockDisposition
6170 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6171 std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
6172 std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
6173 Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
6175 return Pair.first->second;
6177 BlockDisposition D = computeBlockDisposition(S, BB);
6178 return BlockDispositions[S][BB] = D;
6181 ScalarEvolution::BlockDisposition
6182 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6183 switch (S->getSCEVType()) {
6185 return ProperlyDominatesBlock;
6189 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
6190 case scAddRecExpr: {
6191 // This uses a "dominates" query instead of "properly dominates" query
6192 // to test for proper dominance too, because the instruction which
6193 // produces the addrec's value is a PHI, and a PHI effectively properly
6194 // dominates its entire containing block.
6195 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6196 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
6197 return DoesNotDominateBlock;
6199 // FALL THROUGH into SCEVNAryExpr handling.
6204 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6206 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6208 BlockDisposition D = getBlockDisposition(*I, BB);
6209 if (D == DoesNotDominateBlock)
6210 return DoesNotDominateBlock;
6211 if (D == DominatesBlock)
6214 return Proper ? ProperlyDominatesBlock : DominatesBlock;
6217 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6218 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6219 BlockDisposition LD = getBlockDisposition(LHS, BB);
6220 if (LD == DoesNotDominateBlock)
6221 return DoesNotDominateBlock;
6222 BlockDisposition RD = getBlockDisposition(RHS, BB);
6223 if (RD == DoesNotDominateBlock)
6224 return DoesNotDominateBlock;
6225 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
6226 ProperlyDominatesBlock : DominatesBlock;
6229 if (Instruction *I =
6230 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
6231 if (I->getParent() == BB)
6232 return DominatesBlock;
6233 if (DT->properlyDominates(I->getParent(), BB))
6234 return ProperlyDominatesBlock;
6235 return DoesNotDominateBlock;
6237 return ProperlyDominatesBlock;
6238 case scCouldNotCompute:
6239 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6240 return DoesNotDominateBlock;
6243 llvm_unreachable("Unknown SCEV kind!");
6244 return DoesNotDominateBlock;
6247 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
6248 return getBlockDisposition(S, BB) >= DominatesBlock;
6251 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
6252 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
6255 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
6256 switch (S->getSCEVType()) {
6261 case scSignExtend: {
6262 const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
6263 const SCEV *CastOp = Cast->getOperand();
6264 return Op == CastOp || hasOperand(CastOp, Op);
6271 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6272 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6274 const SCEV *NAryOp = *I;
6275 if (NAryOp == Op || hasOperand(NAryOp, Op))
6281 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6282 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6283 return LHS == Op || hasOperand(LHS, Op) ||
6284 RHS == Op || hasOperand(RHS, Op);
6288 case scCouldNotCompute:
6289 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6293 llvm_unreachable("Unknown SCEV kind!");
6297 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
6298 ValuesAtScopes.erase(S);
6299 LoopDispositions.erase(S);
6300 BlockDispositions.erase(S);
6301 UnsignedRanges.erase(S);
6302 SignedRanges.erase(S);