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->getNoWrapFlags(FlagNUW))
162 if (AR->getNoWrapFlags(FlagNSW))
164 if (AR->getNoWrapFlags(FlagNW) &&
165 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
167 WriteAsOperand(OS, AR->getLoop()->getHeader(), /*PrintType=*/false);
175 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
176 const char *OpStr = 0;
177 switch (NAry->getSCEVType()) {
178 case scAddExpr: OpStr = " + "; break;
179 case scMulExpr: OpStr = " * "; break;
180 case scUMaxExpr: OpStr = " umax "; break;
181 case scSMaxExpr: OpStr = " smax "; break;
184 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
187 if (llvm::next(I) != E)
191 switch (NAry->getSCEVType()) {
194 if (NAry->getNoWrapFlags(FlagNUW))
196 if (NAry->getNoWrapFlags(FlagNSW))
202 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
203 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
207 const SCEVUnknown *U = cast<SCEVUnknown>(this);
209 if (U->isSizeOf(AllocTy)) {
210 OS << "sizeof(" << *AllocTy << ")";
213 if (U->isAlignOf(AllocTy)) {
214 OS << "alignof(" << *AllocTy << ")";
220 if (U->isOffsetOf(CTy, FieldNo)) {
221 OS << "offsetof(" << *CTy << ", ";
222 WriteAsOperand(OS, FieldNo, false);
227 // Otherwise just print it normally.
228 WriteAsOperand(OS, U->getValue(), false);
231 case scCouldNotCompute:
232 OS << "***COULDNOTCOMPUTE***";
236 llvm_unreachable("Unknown SCEV kind!");
239 Type *SCEV::getType() const {
240 switch (getSCEVType()) {
242 return cast<SCEVConstant>(this)->getType();
246 return cast<SCEVCastExpr>(this)->getType();
251 return cast<SCEVNAryExpr>(this)->getType();
253 return cast<SCEVAddExpr>(this)->getType();
255 return cast<SCEVUDivExpr>(this)->getType();
257 return cast<SCEVUnknown>(this)->getType();
258 case scCouldNotCompute:
259 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
263 llvm_unreachable("Unknown SCEV kind!");
267 bool SCEV::isZero() const {
268 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
269 return SC->getValue()->isZero();
273 bool SCEV::isOne() const {
274 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
275 return SC->getValue()->isOne();
279 bool SCEV::isAllOnesValue() const {
280 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
281 return SC->getValue()->isAllOnesValue();
285 SCEVCouldNotCompute::SCEVCouldNotCompute() :
286 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
288 bool SCEVCouldNotCompute::classof(const SCEV *S) {
289 return S->getSCEVType() == scCouldNotCompute;
292 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
294 ID.AddInteger(scConstant);
297 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
298 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
299 UniqueSCEVs.InsertNode(S, IP);
303 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
304 return getConstant(ConstantInt::get(getContext(), Val));
308 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
309 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
310 return getConstant(ConstantInt::get(ITy, V, isSigned));
313 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
314 unsigned SCEVTy, const SCEV *op, Type *ty)
315 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
317 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
318 const SCEV *op, Type *ty)
319 : SCEVCastExpr(ID, scTruncate, op, ty) {
320 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
321 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
322 "Cannot truncate non-integer value!");
325 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
326 const SCEV *op, Type *ty)
327 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
328 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
329 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
330 "Cannot zero extend non-integer value!");
333 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
334 const SCEV *op, Type *ty)
335 : SCEVCastExpr(ID, scSignExtend, op, ty) {
336 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
337 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
338 "Cannot sign extend non-integer value!");
341 void SCEVUnknown::deleted() {
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 // Release the value.
352 void SCEVUnknown::allUsesReplacedWith(Value *New) {
353 // Clear this SCEVUnknown from various maps.
354 SE->forgetMemoizedResults(this);
356 // Remove this SCEVUnknown from the uniquing map.
357 SE->UniqueSCEVs.RemoveNode(this);
359 // Update this SCEVUnknown to point to the new value. This is needed
360 // because there may still be outstanding SCEVs which still point to
365 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
366 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
367 if (VCE->getOpcode() == Instruction::PtrToInt)
368 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
369 if (CE->getOpcode() == Instruction::GetElementPtr &&
370 CE->getOperand(0)->isNullValue() &&
371 CE->getNumOperands() == 2)
372 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
374 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
382 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
383 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
384 if (VCE->getOpcode() == Instruction::PtrToInt)
385 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
386 if (CE->getOpcode() == Instruction::GetElementPtr &&
387 CE->getOperand(0)->isNullValue()) {
389 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
390 if (StructType *STy = dyn_cast<StructType>(Ty))
391 if (!STy->isPacked() &&
392 CE->getNumOperands() == 3 &&
393 CE->getOperand(1)->isNullValue()) {
394 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
396 STy->getNumElements() == 2 &&
397 STy->getElementType(0)->isIntegerTy(1)) {
398 AllocTy = STy->getElementType(1);
407 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
408 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
409 if (VCE->getOpcode() == Instruction::PtrToInt)
410 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
411 if (CE->getOpcode() == Instruction::GetElementPtr &&
412 CE->getNumOperands() == 3 &&
413 CE->getOperand(0)->isNullValue() &&
414 CE->getOperand(1)->isNullValue()) {
416 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
417 // Ignore vector types here so that ScalarEvolutionExpander doesn't
418 // emit getelementptrs that index into vectors.
419 if (Ty->isStructTy() || Ty->isArrayTy()) {
421 FieldNo = CE->getOperand(2);
429 //===----------------------------------------------------------------------===//
431 //===----------------------------------------------------------------------===//
434 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
435 /// than the complexity of the RHS. This comparator is used to canonicalize
437 class SCEVComplexityCompare {
438 const LoopInfo *const LI;
440 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
442 // Return true or false if LHS is less than, or at least RHS, respectively.
443 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
444 return compare(LHS, RHS) < 0;
447 // Return negative, zero, or positive, if LHS is less than, equal to, or
448 // greater than RHS, respectively. A three-way result allows recursive
449 // comparisons to be more efficient.
450 int compare(const SCEV *LHS, const SCEV *RHS) const {
451 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
455 // Primarily, sort the SCEVs by their getSCEVType().
456 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
458 return (int)LType - (int)RType;
460 // Aside from the getSCEVType() ordering, the particular ordering
461 // isn't very important except that it's beneficial to be consistent,
462 // so that (a + b) and (b + a) don't end up as different expressions.
465 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
466 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
468 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
469 // not as complete as it could be.
470 const Value *LV = LU->getValue(), *RV = RU->getValue();
472 // Order pointer values after integer values. This helps SCEVExpander
474 bool LIsPointer = LV->getType()->isPointerTy(),
475 RIsPointer = RV->getType()->isPointerTy();
476 if (LIsPointer != RIsPointer)
477 return (int)LIsPointer - (int)RIsPointer;
479 // Compare getValueID values.
480 unsigned LID = LV->getValueID(),
481 RID = RV->getValueID();
483 return (int)LID - (int)RID;
485 // Sort arguments by their position.
486 if (const Argument *LA = dyn_cast<Argument>(LV)) {
487 const Argument *RA = cast<Argument>(RV);
488 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
489 return (int)LArgNo - (int)RArgNo;
492 // For instructions, compare their loop depth, and their operand
493 // count. This is pretty loose.
494 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
495 const Instruction *RInst = cast<Instruction>(RV);
497 // Compare loop depths.
498 const BasicBlock *LParent = LInst->getParent(),
499 *RParent = RInst->getParent();
500 if (LParent != RParent) {
501 unsigned LDepth = LI->getLoopDepth(LParent),
502 RDepth = LI->getLoopDepth(RParent);
503 if (LDepth != RDepth)
504 return (int)LDepth - (int)RDepth;
507 // Compare the number of operands.
508 unsigned LNumOps = LInst->getNumOperands(),
509 RNumOps = RInst->getNumOperands();
510 return (int)LNumOps - (int)RNumOps;
517 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
518 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
520 // Compare constant values.
521 const APInt &LA = LC->getValue()->getValue();
522 const APInt &RA = RC->getValue()->getValue();
523 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
524 if (LBitWidth != RBitWidth)
525 return (int)LBitWidth - (int)RBitWidth;
526 return LA.ult(RA) ? -1 : 1;
530 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
531 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
533 // Compare addrec loop depths.
534 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
535 if (LLoop != RLoop) {
536 unsigned LDepth = LLoop->getLoopDepth(),
537 RDepth = RLoop->getLoopDepth();
538 if (LDepth != RDepth)
539 return (int)LDepth - (int)RDepth;
542 // Addrec complexity grows with operand count.
543 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
544 if (LNumOps != RNumOps)
545 return (int)LNumOps - (int)RNumOps;
547 // Lexicographically compare.
548 for (unsigned i = 0; i != LNumOps; ++i) {
549 long X = compare(LA->getOperand(i), RA->getOperand(i));
561 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
562 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
564 // Lexicographically compare n-ary expressions.
565 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
566 for (unsigned i = 0; i != LNumOps; ++i) {
569 long X = compare(LC->getOperand(i), RC->getOperand(i));
573 return (int)LNumOps - (int)RNumOps;
577 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
578 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
580 // Lexicographically compare udiv expressions.
581 long X = compare(LC->getLHS(), RC->getLHS());
584 return compare(LC->getRHS(), RC->getRHS());
590 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
591 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
593 // Compare cast expressions by operand.
594 return compare(LC->getOperand(), RC->getOperand());
601 llvm_unreachable("Unknown SCEV kind!");
607 /// GroupByComplexity - Given a list of SCEV objects, order them by their
608 /// complexity, and group objects of the same complexity together by value.
609 /// When this routine is finished, we know that any duplicates in the vector are
610 /// consecutive and that complexity is monotonically increasing.
612 /// Note that we go take special precautions to ensure that we get deterministic
613 /// results from this routine. In other words, we don't want the results of
614 /// this to depend on where the addresses of various SCEV objects happened to
617 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
619 if (Ops.size() < 2) return; // Noop
620 if (Ops.size() == 2) {
621 // This is the common case, which also happens to be trivially simple.
623 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
624 if (SCEVComplexityCompare(LI)(RHS, LHS))
629 // Do the rough sort by complexity.
630 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
632 // Now that we are sorted by complexity, group elements of the same
633 // complexity. Note that this is, at worst, N^2, but the vector is likely to
634 // be extremely short in practice. Note that we take this approach because we
635 // do not want to depend on the addresses of the objects we are grouping.
636 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
637 const SCEV *S = Ops[i];
638 unsigned Complexity = S->getSCEVType();
640 // If there are any objects of the same complexity and same value as this
642 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
643 if (Ops[j] == S) { // Found a duplicate.
644 // Move it to immediately after i'th element.
645 std::swap(Ops[i+1], Ops[j]);
646 ++i; // no need to rescan it.
647 if (i == e-2) return; // Done!
655 //===----------------------------------------------------------------------===//
656 // Simple SCEV method implementations
657 //===----------------------------------------------------------------------===//
659 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
661 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
664 // Handle the simplest case efficiently.
666 return SE.getTruncateOrZeroExtend(It, ResultTy);
668 // We are using the following formula for BC(It, K):
670 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
672 // Suppose, W is the bitwidth of the return value. We must be prepared for
673 // overflow. Hence, we must assure that the result of our computation is
674 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
675 // safe in modular arithmetic.
677 // However, this code doesn't use exactly that formula; the formula it uses
678 // is something like the following, where T is the number of factors of 2 in
679 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
682 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
684 // This formula is trivially equivalent to the previous formula. However,
685 // this formula can be implemented much more efficiently. The trick is that
686 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
687 // arithmetic. To do exact division in modular arithmetic, all we have
688 // to do is multiply by the inverse. Therefore, this step can be done at
691 // The next issue is how to safely do the division by 2^T. The way this
692 // is done is by doing the multiplication step at a width of at least W + T
693 // bits. This way, the bottom W+T bits of the product are accurate. Then,
694 // when we perform the division by 2^T (which is equivalent to a right shift
695 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
696 // truncated out after the division by 2^T.
698 // In comparison to just directly using the first formula, this technique
699 // is much more efficient; using the first formula requires W * K bits,
700 // but this formula less than W + K bits. Also, the first formula requires
701 // a division step, whereas this formula only requires multiplies and shifts.
703 // It doesn't matter whether the subtraction step is done in the calculation
704 // width or the input iteration count's width; if the subtraction overflows,
705 // the result must be zero anyway. We prefer here to do it in the width of
706 // the induction variable because it helps a lot for certain cases; CodeGen
707 // isn't smart enough to ignore the overflow, which leads to much less
708 // efficient code if the width of the subtraction is wider than the native
711 // (It's possible to not widen at all by pulling out factors of 2 before
712 // the multiplication; for example, K=2 can be calculated as
713 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
714 // extra arithmetic, so it's not an obvious win, and it gets
715 // much more complicated for K > 3.)
717 // Protection from insane SCEVs; this bound is conservative,
718 // but it probably doesn't matter.
720 return SE.getCouldNotCompute();
722 unsigned W = SE.getTypeSizeInBits(ResultTy);
724 // Calculate K! / 2^T and T; we divide out the factors of two before
725 // multiplying for calculating K! / 2^T to avoid overflow.
726 // Other overflow doesn't matter because we only care about the bottom
727 // W bits of the result.
728 APInt OddFactorial(W, 1);
730 for (unsigned i = 3; i <= K; ++i) {
732 unsigned TwoFactors = Mult.countTrailingZeros();
734 Mult = Mult.lshr(TwoFactors);
735 OddFactorial *= Mult;
738 // We need at least W + T bits for the multiplication step
739 unsigned CalculationBits = W + T;
741 // Calculate 2^T, at width T+W.
742 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
744 // Calculate the multiplicative inverse of K! / 2^T;
745 // this multiplication factor will perform the exact division by
747 APInt Mod = APInt::getSignedMinValue(W+1);
748 APInt MultiplyFactor = OddFactorial.zext(W+1);
749 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
750 MultiplyFactor = MultiplyFactor.trunc(W);
752 // Calculate the product, at width T+W
753 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
755 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
756 for (unsigned i = 1; i != K; ++i) {
757 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
758 Dividend = SE.getMulExpr(Dividend,
759 SE.getTruncateOrZeroExtend(S, CalculationTy));
763 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
765 // Truncate the result, and divide by K! / 2^T.
767 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
768 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
771 /// evaluateAtIteration - Return the value of this chain of recurrences at
772 /// the specified iteration number. We can evaluate this recurrence by
773 /// multiplying each element in the chain by the binomial coefficient
774 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
776 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
778 /// where BC(It, k) stands for binomial coefficient.
780 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
781 ScalarEvolution &SE) const {
782 const SCEV *Result = getStart();
783 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
784 // The computation is correct in the face of overflow provided that the
785 // multiplication is performed _after_ the evaluation of the binomial
787 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
788 if (isa<SCEVCouldNotCompute>(Coeff))
791 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
796 //===----------------------------------------------------------------------===//
797 // SCEV Expression folder implementations
798 //===----------------------------------------------------------------------===//
800 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
802 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
803 "This is not a truncating conversion!");
804 assert(isSCEVable(Ty) &&
805 "This is not a conversion to a SCEVable type!");
806 Ty = getEffectiveSCEVType(Ty);
809 ID.AddInteger(scTruncate);
813 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
815 // Fold if the operand is constant.
816 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
818 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
819 getEffectiveSCEVType(Ty))));
821 // trunc(trunc(x)) --> trunc(x)
822 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
823 return getTruncateExpr(ST->getOperand(), Ty);
825 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
826 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
827 return getTruncateOrSignExtend(SS->getOperand(), Ty);
829 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
830 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
831 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
833 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
834 // eliminate all the truncates.
835 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
836 SmallVector<const SCEV *, 4> Operands;
837 bool hasTrunc = false;
838 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
839 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
840 hasTrunc = isa<SCEVTruncateExpr>(S);
841 Operands.push_back(S);
844 return getAddExpr(Operands);
845 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
848 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
849 // eliminate all the truncates.
850 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
851 SmallVector<const SCEV *, 4> Operands;
852 bool hasTrunc = false;
853 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
854 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
855 hasTrunc = isa<SCEVTruncateExpr>(S);
856 Operands.push_back(S);
859 return getMulExpr(Operands);
860 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
863 // If the input value is a chrec scev, truncate the chrec's operands.
864 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
865 SmallVector<const SCEV *, 4> Operands;
866 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
867 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
868 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
871 // As a special case, fold trunc(undef) to undef. We don't want to
872 // know too much about SCEVUnknowns, but this special case is handy
874 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
875 if (isa<UndefValue>(U->getValue()))
876 return getSCEV(UndefValue::get(Ty));
878 // The cast wasn't folded; create an explicit cast node. We can reuse
879 // the existing insert position since if we get here, we won't have
880 // made any changes which would invalidate it.
881 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
883 UniqueSCEVs.InsertNode(S, IP);
887 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
889 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
890 "This is not an extending conversion!");
891 assert(isSCEVable(Ty) &&
892 "This is not a conversion to a SCEVable type!");
893 Ty = getEffectiveSCEVType(Ty);
895 // Fold if the operand is constant.
896 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
898 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
899 getEffectiveSCEVType(Ty))));
901 // zext(zext(x)) --> zext(x)
902 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
903 return getZeroExtendExpr(SZ->getOperand(), Ty);
905 // Before doing any expensive analysis, check to see if we've already
906 // computed a SCEV for this Op and Ty.
908 ID.AddInteger(scZeroExtend);
912 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
914 // zext(trunc(x)) --> zext(x) or x or trunc(x)
915 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
916 // It's possible the bits taken off by the truncate were all zero bits. If
917 // so, we should be able to simplify this further.
918 const SCEV *X = ST->getOperand();
919 ConstantRange CR = getUnsignedRange(X);
920 unsigned TruncBits = getTypeSizeInBits(ST->getType());
921 unsigned NewBits = getTypeSizeInBits(Ty);
922 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
923 CR.zextOrTrunc(NewBits)))
924 return getTruncateOrZeroExtend(X, Ty);
927 // If the input value is a chrec scev, and we can prove that the value
928 // did not overflow the old, smaller, value, we can zero extend all of the
929 // operands (often constants). This allows analysis of something like
930 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
931 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
932 if (AR->isAffine()) {
933 const SCEV *Start = AR->getStart();
934 const SCEV *Step = AR->getStepRecurrence(*this);
935 unsigned BitWidth = getTypeSizeInBits(AR->getType());
936 const Loop *L = AR->getLoop();
938 // If we have special knowledge that this addrec won't overflow,
939 // we don't need to do any further analysis.
940 if (AR->getNoWrapFlags(SCEV::FlagNUW))
941 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
942 getZeroExtendExpr(Step, Ty),
943 L, AR->getNoWrapFlags());
945 // Check whether the backedge-taken count is SCEVCouldNotCompute.
946 // Note that this serves two purposes: It filters out loops that are
947 // simply not analyzable, and it covers the case where this code is
948 // being called from within backedge-taken count analysis, such that
949 // attempting to ask for the backedge-taken count would likely result
950 // in infinite recursion. In the later case, the analysis code will
951 // cope with a conservative value, and it will take care to purge
952 // that value once it has finished.
953 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
954 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
955 // Manually compute the final value for AR, checking for
958 // Check whether the backedge-taken count can be losslessly casted to
959 // the addrec's type. The count is always unsigned.
960 const SCEV *CastedMaxBECount =
961 getTruncateOrZeroExtend(MaxBECount, Start->getType());
962 const SCEV *RecastedMaxBECount =
963 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
964 if (MaxBECount == RecastedMaxBECount) {
965 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
966 // Check whether Start+Step*MaxBECount has no unsigned overflow.
967 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
968 const SCEV *Add = getAddExpr(Start, ZMul);
969 const SCEV *OperandExtendedAdd =
970 getAddExpr(getZeroExtendExpr(Start, WideTy),
971 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
972 getZeroExtendExpr(Step, WideTy)));
973 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd) {
974 // Cache knowledge of AR NUW, which is propagated to this AddRec.
975 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
976 // Return the expression with the addrec on the outside.
977 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
978 getZeroExtendExpr(Step, Ty),
979 L, AR->getNoWrapFlags());
981 // Similar to above, only this time treat the step value as signed.
982 // This covers loops that count down.
983 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
984 Add = getAddExpr(Start, SMul);
986 getAddExpr(getZeroExtendExpr(Start, WideTy),
987 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
988 getSignExtendExpr(Step, WideTy)));
989 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd) {
990 // Cache knowledge of AR NW, which is propagated to this AddRec.
991 // Negative step causes unsigned wrap, but it still can't self-wrap.
992 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
993 // Return the expression with the addrec on the outside.
994 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
995 getSignExtendExpr(Step, Ty),
996 L, AR->getNoWrapFlags());
1000 // If the backedge is guarded by a comparison with the pre-inc value
1001 // the addrec is safe. Also, if the entry is guarded by a comparison
1002 // with the start value and the backedge is guarded by a comparison
1003 // with the post-inc value, the addrec is safe.
1004 if (isKnownPositive(Step)) {
1005 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1006 getUnsignedRange(Step).getUnsignedMax());
1007 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1008 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1009 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1010 AR->getPostIncExpr(*this), N))) {
1011 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1012 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1013 // Return the expression with the addrec on the outside.
1014 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1015 getZeroExtendExpr(Step, Ty),
1016 L, AR->getNoWrapFlags());
1018 } else if (isKnownNegative(Step)) {
1019 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1020 getSignedRange(Step).getSignedMin());
1021 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1022 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1023 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1024 AR->getPostIncExpr(*this), N))) {
1025 // Cache knowledge of AR NW, which is propagated to this AddRec.
1026 // Negative step causes unsigned wrap, but it still can't self-wrap.
1027 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1028 // Return the expression with the addrec on the outside.
1029 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1030 getSignExtendExpr(Step, Ty),
1031 L, AR->getNoWrapFlags());
1037 // The cast wasn't folded; create an explicit cast node.
1038 // Recompute the insert position, as it may have been invalidated.
1039 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1040 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1042 UniqueSCEVs.InsertNode(S, IP);
1046 // Get the limit of a recurrence such that incrementing by Step cannot cause
1047 // signed overflow as long as the value of the recurrence within the loop does
1048 // not exceed this limit before incrementing.
1049 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1050 ICmpInst::Predicate *Pred,
1051 ScalarEvolution *SE) {
1052 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1053 if (SE->isKnownPositive(Step)) {
1054 *Pred = ICmpInst::ICMP_SLT;
1055 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1056 SE->getSignedRange(Step).getSignedMax());
1058 if (SE->isKnownNegative(Step)) {
1059 *Pred = ICmpInst::ICMP_SGT;
1060 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1061 SE->getSignedRange(Step).getSignedMin());
1066 // The recurrence AR has been shown to have no signed wrap. Typically, if we can
1067 // prove NSW for AR, then we can just as easily prove NSW for its preincrement
1068 // or postincrement sibling. This allows normalizing a sign extended AddRec as
1069 // such: {sext(Step + Start),+,Step} => {(Step + sext(Start),+,Step} As a
1070 // result, the expression "Step + sext(PreIncAR)" is congruent with
1071 // "sext(PostIncAR)"
1072 static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR,
1074 ScalarEvolution *SE) {
1075 const Loop *L = AR->getLoop();
1076 const SCEV *Start = AR->getStart();
1077 const SCEV *Step = AR->getStepRecurrence(*SE);
1079 // Check for a simple looking step prior to loop entry.
1080 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1084 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1085 // subtraction is expensive. For this purpose, perform a quick and dirty
1086 // difference, by checking for Step in the operand list.
1087 SmallVector<const SCEV *, 4> DiffOps;
1088 for (SCEVAddExpr::op_iterator I = SA->op_begin(), E = SA->op_end();
1091 DiffOps.push_back(*I);
1093 if (DiffOps.size() == SA->getNumOperands())
1096 // This is a postinc AR. Check for overflow on the preinc recurrence using the
1097 // same three conditions that getSignExtendedExpr checks.
1099 // 1. NSW flags on the step increment.
1100 const SCEV *PreStart = SE->getAddExpr(DiffOps, SA->getNoWrapFlags());
1101 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1102 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1104 if (PreAR && PreAR->getNoWrapFlags(SCEV::FlagNSW))
1107 // 2. Direct overflow check on the step operation's expression.
1108 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1109 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1110 const SCEV *OperandExtendedStart =
1111 SE->getAddExpr(SE->getSignExtendExpr(PreStart, WideTy),
1112 SE->getSignExtendExpr(Step, WideTy));
1113 if (SE->getSignExtendExpr(Start, WideTy) == OperandExtendedStart) {
1114 // Cache knowledge of PreAR NSW.
1116 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(SCEV::FlagNSW);
1117 // FIXME: this optimization needs a unit test
1118 DEBUG(dbgs() << "SCEV: untested prestart overflow check\n");
1122 // 3. Loop precondition.
1123 ICmpInst::Predicate Pred;
1124 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, SE);
1126 if (OverflowLimit &&
1127 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) {
1133 // Get the normalized sign-extended expression for this AddRec's Start.
1134 static const SCEV *getSignExtendAddRecStart(const SCEVAddRecExpr *AR,
1136 ScalarEvolution *SE) {
1137 const SCEV *PreStart = getPreStartForSignExtend(AR, Ty, SE);
1139 return SE->getSignExtendExpr(AR->getStart(), Ty);
1141 return SE->getAddExpr(SE->getSignExtendExpr(AR->getStepRecurrence(*SE), Ty),
1142 SE->getSignExtendExpr(PreStart, Ty));
1145 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1147 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1148 "This is not an extending conversion!");
1149 assert(isSCEVable(Ty) &&
1150 "This is not a conversion to a SCEVable type!");
1151 Ty = getEffectiveSCEVType(Ty);
1153 // Fold if the operand is constant.
1154 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1156 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1157 getEffectiveSCEVType(Ty))));
1159 // sext(sext(x)) --> sext(x)
1160 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1161 return getSignExtendExpr(SS->getOperand(), Ty);
1163 // sext(zext(x)) --> zext(x)
1164 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1165 return getZeroExtendExpr(SZ->getOperand(), Ty);
1167 // Before doing any expensive analysis, check to see if we've already
1168 // computed a SCEV for this Op and Ty.
1169 FoldingSetNodeID ID;
1170 ID.AddInteger(scSignExtend);
1174 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1176 // If the input value is provably positive, build a zext instead.
1177 if (isKnownNonNegative(Op))
1178 return getZeroExtendExpr(Op, Ty);
1180 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1181 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1182 // It's possible the bits taken off by the truncate were all sign bits. If
1183 // so, we should be able to simplify this further.
1184 const SCEV *X = ST->getOperand();
1185 ConstantRange CR = getSignedRange(X);
1186 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1187 unsigned NewBits = getTypeSizeInBits(Ty);
1188 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1189 CR.sextOrTrunc(NewBits)))
1190 return getTruncateOrSignExtend(X, Ty);
1193 // If the input value is a chrec scev, and we can prove that the value
1194 // did not overflow the old, smaller, value, we can sign extend all of the
1195 // operands (often constants). This allows analysis of something like
1196 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1197 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1198 if (AR->isAffine()) {
1199 const SCEV *Start = AR->getStart();
1200 const SCEV *Step = AR->getStepRecurrence(*this);
1201 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1202 const Loop *L = AR->getLoop();
1204 // If we have special knowledge that this addrec won't overflow,
1205 // we don't need to do any further analysis.
1206 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1207 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1208 getSignExtendExpr(Step, Ty),
1211 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1212 // Note that this serves two purposes: It filters out loops that are
1213 // simply not analyzable, and it covers the case where this code is
1214 // being called from within backedge-taken count analysis, such that
1215 // attempting to ask for the backedge-taken count would likely result
1216 // in infinite recursion. In the later case, the analysis code will
1217 // cope with a conservative value, and it will take care to purge
1218 // that value once it has finished.
1219 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1220 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1221 // Manually compute the final value for AR, checking for
1224 // Check whether the backedge-taken count can be losslessly casted to
1225 // the addrec's type. The count is always unsigned.
1226 const SCEV *CastedMaxBECount =
1227 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1228 const SCEV *RecastedMaxBECount =
1229 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1230 if (MaxBECount == RecastedMaxBECount) {
1231 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1232 // Check whether Start+Step*MaxBECount has no signed overflow.
1233 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1234 const SCEV *Add = getAddExpr(Start, SMul);
1235 const SCEV *OperandExtendedAdd =
1236 getAddExpr(getSignExtendExpr(Start, WideTy),
1237 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1238 getSignExtendExpr(Step, WideTy)));
1239 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd) {
1240 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1241 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1242 // Return the expression with the addrec on the outside.
1243 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1244 getSignExtendExpr(Step, Ty),
1245 L, AR->getNoWrapFlags());
1247 // Similar to above, only this time treat the step value as unsigned.
1248 // This covers loops that count up with an unsigned step.
1249 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1250 Add = getAddExpr(Start, UMul);
1251 OperandExtendedAdd =
1252 getAddExpr(getSignExtendExpr(Start, WideTy),
1253 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1254 getZeroExtendExpr(Step, WideTy)));
1255 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd) {
1256 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1257 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1258 // Return the expression with the addrec on the outside.
1259 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1260 getZeroExtendExpr(Step, Ty),
1261 L, AR->getNoWrapFlags());
1265 // If the backedge is guarded by a comparison with the pre-inc value
1266 // the addrec is safe. Also, if the entry is guarded by a comparison
1267 // with the start value and the backedge is guarded by a comparison
1268 // with the post-inc value, the addrec is safe.
1269 ICmpInst::Predicate Pred;
1270 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, this);
1271 if (OverflowLimit &&
1272 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1273 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1274 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1276 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1277 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1278 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1279 getSignExtendExpr(Step, Ty),
1280 L, AR->getNoWrapFlags());
1285 // The cast wasn't folded; create an explicit cast node.
1286 // Recompute the insert position, as it may have been invalidated.
1287 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1288 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1290 UniqueSCEVs.InsertNode(S, IP);
1294 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1295 /// unspecified bits out to the given type.
1297 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1299 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1300 "This is not an extending conversion!");
1301 assert(isSCEVable(Ty) &&
1302 "This is not a conversion to a SCEVable type!");
1303 Ty = getEffectiveSCEVType(Ty);
1305 // Sign-extend negative constants.
1306 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1307 if (SC->getValue()->getValue().isNegative())
1308 return getSignExtendExpr(Op, Ty);
1310 // Peel off a truncate cast.
1311 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1312 const SCEV *NewOp = T->getOperand();
1313 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1314 return getAnyExtendExpr(NewOp, Ty);
1315 return getTruncateOrNoop(NewOp, Ty);
1318 // Next try a zext cast. If the cast is folded, use it.
1319 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1320 if (!isa<SCEVZeroExtendExpr>(ZExt))
1323 // Next try a sext cast. If the cast is folded, use it.
1324 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1325 if (!isa<SCEVSignExtendExpr>(SExt))
1328 // Force the cast to be folded into the operands of an addrec.
1329 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1330 SmallVector<const SCEV *, 4> Ops;
1331 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1333 Ops.push_back(getAnyExtendExpr(*I, Ty));
1334 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1337 // As a special case, fold anyext(undef) to undef. We don't want to
1338 // know too much about SCEVUnknowns, but this special case is handy
1340 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
1341 if (isa<UndefValue>(U->getValue()))
1342 return getSCEV(UndefValue::get(Ty));
1344 // If the expression is obviously signed, use the sext cast value.
1345 if (isa<SCEVSMaxExpr>(Op))
1348 // Absent any other information, use the zext cast value.
1352 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1353 /// a list of operands to be added under the given scale, update the given
1354 /// map. This is a helper function for getAddRecExpr. As an example of
1355 /// what it does, given a sequence of operands that would form an add
1356 /// expression like this:
1358 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1360 /// where A and B are constants, update the map with these values:
1362 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1364 /// and add 13 + A*B*29 to AccumulatedConstant.
1365 /// This will allow getAddRecExpr to produce this:
1367 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1369 /// This form often exposes folding opportunities that are hidden in
1370 /// the original operand list.
1372 /// Return true iff it appears that any interesting folding opportunities
1373 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1374 /// the common case where no interesting opportunities are present, and
1375 /// is also used as a check to avoid infinite recursion.
1378 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1379 SmallVector<const SCEV *, 8> &NewOps,
1380 APInt &AccumulatedConstant,
1381 const SCEV *const *Ops, size_t NumOperands,
1383 ScalarEvolution &SE) {
1384 bool Interesting = false;
1386 // Iterate over the add operands. They are sorted, with constants first.
1388 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1390 // Pull a buried constant out to the outside.
1391 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1393 AccumulatedConstant += Scale * C->getValue()->getValue();
1396 // Next comes everything else. We're especially interested in multiplies
1397 // here, but they're in the middle, so just visit the rest with one loop.
1398 for (; i != NumOperands; ++i) {
1399 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1400 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1402 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1403 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1404 // A multiplication of a constant with another add; recurse.
1405 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1407 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1408 Add->op_begin(), Add->getNumOperands(),
1411 // A multiplication of a constant with some other value. Update
1413 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1414 const SCEV *Key = SE.getMulExpr(MulOps);
1415 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1416 M.insert(std::make_pair(Key, NewScale));
1418 NewOps.push_back(Pair.first->first);
1420 Pair.first->second += NewScale;
1421 // The map already had an entry for this value, which may indicate
1422 // a folding opportunity.
1427 // An ordinary operand. Update the map.
1428 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1429 M.insert(std::make_pair(Ops[i], Scale));
1431 NewOps.push_back(Pair.first->first);
1433 Pair.first->second += Scale;
1434 // The map already had an entry for this value, which may indicate
1435 // a folding opportunity.
1445 struct APIntCompare {
1446 bool operator()(const APInt &LHS, const APInt &RHS) const {
1447 return LHS.ult(RHS);
1452 /// getAddExpr - Get a canonical add expression, or something simpler if
1454 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1455 SCEV::NoWrapFlags Flags) {
1456 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
1457 "only nuw or nsw allowed");
1458 assert(!Ops.empty() && "Cannot get empty add!");
1459 if (Ops.size() == 1) return Ops[0];
1461 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1462 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1463 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1464 "SCEVAddExpr operand types don't match!");
1467 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1469 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1470 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1471 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1473 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1474 E = Ops.end(); I != E; ++I)
1475 if (!isKnownNonNegative(*I)) {
1479 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1482 // Sort by complexity, this groups all similar expression types together.
1483 GroupByComplexity(Ops, LI);
1485 // If there are any constants, fold them together.
1487 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1489 assert(Idx < Ops.size());
1490 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1491 // We found two constants, fold them together!
1492 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1493 RHSC->getValue()->getValue());
1494 if (Ops.size() == 2) return Ops[0];
1495 Ops.erase(Ops.begin()+1); // Erase the folded element
1496 LHSC = cast<SCEVConstant>(Ops[0]);
1499 // If we are left with a constant zero being added, strip it off.
1500 if (LHSC->getValue()->isZero()) {
1501 Ops.erase(Ops.begin());
1505 if (Ops.size() == 1) return Ops[0];
1508 // Okay, check to see if the same value occurs in the operand list more than
1509 // once. If so, merge them together into an multiply expression. Since we
1510 // sorted the list, these values are required to be adjacent.
1511 Type *Ty = Ops[0]->getType();
1512 bool FoundMatch = false;
1513 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1514 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1515 // Scan ahead to count how many equal operands there are.
1517 while (i+Count != e && Ops[i+Count] == Ops[i])
1519 // Merge the values into a multiply.
1520 const SCEV *Scale = getConstant(Ty, Count);
1521 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1522 if (Ops.size() == Count)
1525 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1526 --i; e -= Count - 1;
1530 return getAddExpr(Ops, Flags);
1532 // Check for truncates. If all the operands are truncated from the same
1533 // type, see if factoring out the truncate would permit the result to be
1534 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1535 // if the contents of the resulting outer trunc fold to something simple.
1536 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1537 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1538 Type *DstType = Trunc->getType();
1539 Type *SrcType = Trunc->getOperand()->getType();
1540 SmallVector<const SCEV *, 8> LargeOps;
1542 // Check all the operands to see if they can be represented in the
1543 // source type of the truncate.
1544 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1545 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1546 if (T->getOperand()->getType() != SrcType) {
1550 LargeOps.push_back(T->getOperand());
1551 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1552 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1553 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1554 SmallVector<const SCEV *, 8> LargeMulOps;
1555 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1556 if (const SCEVTruncateExpr *T =
1557 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1558 if (T->getOperand()->getType() != SrcType) {
1562 LargeMulOps.push_back(T->getOperand());
1563 } else if (const SCEVConstant *C =
1564 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1565 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1572 LargeOps.push_back(getMulExpr(LargeMulOps));
1579 // Evaluate the expression in the larger type.
1580 const SCEV *Fold = getAddExpr(LargeOps, Flags);
1581 // If it folds to something simple, use it. Otherwise, don't.
1582 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1583 return getTruncateExpr(Fold, DstType);
1587 // Skip past any other cast SCEVs.
1588 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1591 // If there are add operands they would be next.
1592 if (Idx < Ops.size()) {
1593 bool DeletedAdd = false;
1594 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1595 // If we have an add, expand the add operands onto the end of the operands
1597 Ops.erase(Ops.begin()+Idx);
1598 Ops.append(Add->op_begin(), Add->op_end());
1602 // If we deleted at least one add, we added operands to the end of the list,
1603 // and they are not necessarily sorted. Recurse to resort and resimplify
1604 // any operands we just acquired.
1606 return getAddExpr(Ops);
1609 // Skip over the add expression until we get to a multiply.
1610 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1613 // Check to see if there are any folding opportunities present with
1614 // operands multiplied by constant values.
1615 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1616 uint64_t BitWidth = getTypeSizeInBits(Ty);
1617 DenseMap<const SCEV *, APInt> M;
1618 SmallVector<const SCEV *, 8> NewOps;
1619 APInt AccumulatedConstant(BitWidth, 0);
1620 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1621 Ops.data(), Ops.size(),
1622 APInt(BitWidth, 1), *this)) {
1623 // Some interesting folding opportunity is present, so its worthwhile to
1624 // re-generate the operands list. Group the operands by constant scale,
1625 // to avoid multiplying by the same constant scale multiple times.
1626 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1627 for (SmallVector<const SCEV *, 8>::const_iterator I = NewOps.begin(),
1628 E = NewOps.end(); I != E; ++I)
1629 MulOpLists[M.find(*I)->second].push_back(*I);
1630 // Re-generate the operands list.
1632 if (AccumulatedConstant != 0)
1633 Ops.push_back(getConstant(AccumulatedConstant));
1634 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1635 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1637 Ops.push_back(getMulExpr(getConstant(I->first),
1638 getAddExpr(I->second)));
1640 return getConstant(Ty, 0);
1641 if (Ops.size() == 1)
1643 return getAddExpr(Ops);
1647 // If we are adding something to a multiply expression, make sure the
1648 // something is not already an operand of the multiply. If so, merge it into
1650 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1651 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1652 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1653 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1654 if (isa<SCEVConstant>(MulOpSCEV))
1656 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1657 if (MulOpSCEV == Ops[AddOp]) {
1658 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1659 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1660 if (Mul->getNumOperands() != 2) {
1661 // If the multiply has more than two operands, we must get the
1663 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1664 Mul->op_begin()+MulOp);
1665 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1666 InnerMul = getMulExpr(MulOps);
1668 const SCEV *One = getConstant(Ty, 1);
1669 const SCEV *AddOne = getAddExpr(One, InnerMul);
1670 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1671 if (Ops.size() == 2) return OuterMul;
1673 Ops.erase(Ops.begin()+AddOp);
1674 Ops.erase(Ops.begin()+Idx-1);
1676 Ops.erase(Ops.begin()+Idx);
1677 Ops.erase(Ops.begin()+AddOp-1);
1679 Ops.push_back(OuterMul);
1680 return getAddExpr(Ops);
1683 // Check this multiply against other multiplies being added together.
1684 for (unsigned OtherMulIdx = Idx+1;
1685 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1687 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1688 // If MulOp occurs in OtherMul, we can fold the two multiplies
1690 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1691 OMulOp != e; ++OMulOp)
1692 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1693 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1694 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1695 if (Mul->getNumOperands() != 2) {
1696 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1697 Mul->op_begin()+MulOp);
1698 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1699 InnerMul1 = getMulExpr(MulOps);
1701 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1702 if (OtherMul->getNumOperands() != 2) {
1703 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1704 OtherMul->op_begin()+OMulOp);
1705 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
1706 InnerMul2 = getMulExpr(MulOps);
1708 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1709 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1710 if (Ops.size() == 2) return OuterMul;
1711 Ops.erase(Ops.begin()+Idx);
1712 Ops.erase(Ops.begin()+OtherMulIdx-1);
1713 Ops.push_back(OuterMul);
1714 return getAddExpr(Ops);
1720 // If there are any add recurrences in the operands list, see if any other
1721 // added values are loop invariant. If so, we can fold them into the
1723 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1726 // Scan over all recurrences, trying to fold loop invariants into them.
1727 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1728 // Scan all of the other operands to this add and add them to the vector if
1729 // they are loop invariant w.r.t. the recurrence.
1730 SmallVector<const SCEV *, 8> LIOps;
1731 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1732 const Loop *AddRecLoop = AddRec->getLoop();
1733 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1734 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1735 LIOps.push_back(Ops[i]);
1736 Ops.erase(Ops.begin()+i);
1740 // If we found some loop invariants, fold them into the recurrence.
1741 if (!LIOps.empty()) {
1742 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1743 LIOps.push_back(AddRec->getStart());
1745 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1747 AddRecOps[0] = getAddExpr(LIOps);
1749 // Build the new addrec. Propagate the NUW and NSW flags if both the
1750 // outer add and the inner addrec are guaranteed to have no overflow.
1751 // Always propagate NW.
1752 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
1753 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
1755 // If all of the other operands were loop invariant, we are done.
1756 if (Ops.size() == 1) return NewRec;
1758 // Otherwise, add the folded AddRec by the non-invariant parts.
1759 for (unsigned i = 0;; ++i)
1760 if (Ops[i] == AddRec) {
1764 return getAddExpr(Ops);
1767 // Okay, if there weren't any loop invariants to be folded, check to see if
1768 // there are multiple AddRec's with the same loop induction variable being
1769 // added together. If so, we can fold them.
1770 for (unsigned OtherIdx = Idx+1;
1771 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1773 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1774 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
1775 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1777 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1779 if (const SCEVAddRecExpr *OtherAddRec =
1780 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1781 if (OtherAddRec->getLoop() == AddRecLoop) {
1782 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
1784 if (i >= AddRecOps.size()) {
1785 AddRecOps.append(OtherAddRec->op_begin()+i,
1786 OtherAddRec->op_end());
1789 AddRecOps[i] = getAddExpr(AddRecOps[i],
1790 OtherAddRec->getOperand(i));
1792 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1794 // Step size has changed, so we cannot guarantee no self-wraparound.
1795 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
1796 return getAddExpr(Ops);
1799 // Otherwise couldn't fold anything into this recurrence. Move onto the
1803 // Okay, it looks like we really DO need an add expr. Check to see if we
1804 // already have one, otherwise create a new one.
1805 FoldingSetNodeID ID;
1806 ID.AddInteger(scAddExpr);
1807 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1808 ID.AddPointer(Ops[i]);
1811 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1813 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1814 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1815 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1817 UniqueSCEVs.InsertNode(S, IP);
1819 S->setNoWrapFlags(Flags);
1823 static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
1825 if (j > 1 && k / j != i) Overflow = true;
1829 /// Compute the result of "n choose k", the binomial coefficient. If an
1830 /// intermediate computation overflows, Overflow will be set and the return will
1831 /// be garbage. Overflow is not cleared on absense of overflow.
1832 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
1833 // We use the multiplicative formula:
1834 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
1835 // At each iteration, we take the n-th term of the numeral and divide by the
1836 // (k-n)th term of the denominator. This division will always produce an
1837 // integral result, and helps reduce the chance of overflow in the
1838 // intermediate computations. However, we can still overflow even when the
1839 // final result would fit.
1841 if (n == 0 || n == k) return 1;
1842 if (k > n) return 0;
1848 for (uint64_t i = 1; i <= k; ++i) {
1849 r = umul_ov(r, n-(i-1), Overflow);
1855 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1857 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1858 SCEV::NoWrapFlags Flags) {
1859 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
1860 "only nuw or nsw allowed");
1861 assert(!Ops.empty() && "Cannot get empty mul!");
1862 if (Ops.size() == 1) return Ops[0];
1864 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1865 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1866 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1867 "SCEVMulExpr operand types don't match!");
1870 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1872 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1873 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1874 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1876 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1877 E = Ops.end(); I != E; ++I)
1878 if (!isKnownNonNegative(*I)) {
1882 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1885 // Sort by complexity, this groups all similar expression types together.
1886 GroupByComplexity(Ops, LI);
1888 // If there are any constants, fold them together.
1890 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1892 // C1*(C2+V) -> C1*C2 + C1*V
1893 if (Ops.size() == 2)
1894 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1895 if (Add->getNumOperands() == 2 &&
1896 isa<SCEVConstant>(Add->getOperand(0)))
1897 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1898 getMulExpr(LHSC, Add->getOperand(1)));
1901 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1902 // We found two constants, fold them together!
1903 ConstantInt *Fold = ConstantInt::get(getContext(),
1904 LHSC->getValue()->getValue() *
1905 RHSC->getValue()->getValue());
1906 Ops[0] = getConstant(Fold);
1907 Ops.erase(Ops.begin()+1); // Erase the folded element
1908 if (Ops.size() == 1) return Ops[0];
1909 LHSC = cast<SCEVConstant>(Ops[0]);
1912 // If we are left with a constant one being multiplied, strip it off.
1913 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1914 Ops.erase(Ops.begin());
1916 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1917 // If we have a multiply of zero, it will always be zero.
1919 } else if (Ops[0]->isAllOnesValue()) {
1920 // If we have a mul by -1 of an add, try distributing the -1 among the
1922 if (Ops.size() == 2) {
1923 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1924 SmallVector<const SCEV *, 4> NewOps;
1925 bool AnyFolded = false;
1926 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
1927 E = Add->op_end(); I != E; ++I) {
1928 const SCEV *Mul = getMulExpr(Ops[0], *I);
1929 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1930 NewOps.push_back(Mul);
1933 return getAddExpr(NewOps);
1935 else if (const SCEVAddRecExpr *
1936 AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
1937 // Negation preserves a recurrence's no self-wrap property.
1938 SmallVector<const SCEV *, 4> Operands;
1939 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
1940 E = AddRec->op_end(); I != E; ++I) {
1941 Operands.push_back(getMulExpr(Ops[0], *I));
1943 return getAddRecExpr(Operands, AddRec->getLoop(),
1944 AddRec->getNoWrapFlags(SCEV::FlagNW));
1949 if (Ops.size() == 1)
1953 // Skip over the add expression until we get to a multiply.
1954 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1957 // If there are mul operands inline them all into this expression.
1958 if (Idx < Ops.size()) {
1959 bool DeletedMul = false;
1960 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1961 // If we have an mul, expand the mul operands onto the end of the operands
1963 Ops.erase(Ops.begin()+Idx);
1964 Ops.append(Mul->op_begin(), Mul->op_end());
1968 // If we deleted at least one mul, we added operands to the end of the list,
1969 // and they are not necessarily sorted. Recurse to resort and resimplify
1970 // any operands we just acquired.
1972 return getMulExpr(Ops);
1975 // If there are any add recurrences in the operands list, see if any other
1976 // added values are loop invariant. If so, we can fold them into the
1978 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1981 // Scan over all recurrences, trying to fold loop invariants into them.
1982 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1983 // Scan all of the other operands to this mul and add them to the vector if
1984 // they are loop invariant w.r.t. the recurrence.
1985 SmallVector<const SCEV *, 8> LIOps;
1986 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1987 const Loop *AddRecLoop = AddRec->getLoop();
1988 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1989 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1990 LIOps.push_back(Ops[i]);
1991 Ops.erase(Ops.begin()+i);
1995 // If we found some loop invariants, fold them into the recurrence.
1996 if (!LIOps.empty()) {
1997 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1998 SmallVector<const SCEV *, 4> NewOps;
1999 NewOps.reserve(AddRec->getNumOperands());
2000 const SCEV *Scale = getMulExpr(LIOps);
2001 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2002 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2004 // Build the new addrec. Propagate the NUW and NSW flags if both the
2005 // outer mul and the inner addrec are guaranteed to have no overflow.
2007 // No self-wrap cannot be guaranteed after changing the step size, but
2008 // will be inferred if either NUW or NSW is true.
2009 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2010 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2012 // If all of the other operands were loop invariant, we are done.
2013 if (Ops.size() == 1) return NewRec;
2015 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2016 for (unsigned i = 0;; ++i)
2017 if (Ops[i] == AddRec) {
2021 return getMulExpr(Ops);
2024 // Okay, if there weren't any loop invariants to be folded, check to see if
2025 // there are multiple AddRec's with the same loop induction variable being
2026 // multiplied together. If so, we can fold them.
2027 for (unsigned OtherIdx = Idx+1;
2028 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2030 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2031 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2032 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2033 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2034 // ]]],+,...up to x=2n}.
2035 // Note that the arguments to choose() are always integers with values
2036 // known at compile time, never SCEV objects.
2038 // The implementation avoids pointless extra computations when the two
2039 // addrec's are of different length (mathematically, it's equivalent to
2040 // an infinite stream of zeros on the right).
2041 bool OpsModified = false;
2042 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2044 if (const SCEVAddRecExpr *OtherAddRec =
2045 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2046 if (OtherAddRec->getLoop() == AddRecLoop) {
2047 bool Overflow = false;
2048 Type *Ty = AddRec->getType();
2049 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2050 SmallVector<const SCEV*, 7> AddRecOps;
2051 for (int x = 0, xe = AddRec->getNumOperands() +
2052 OtherAddRec->getNumOperands() - 1;
2053 x != xe && !Overflow; ++x) {
2054 const SCEV *Term = getConstant(Ty, 0);
2055 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2056 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2057 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2058 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2059 z < ze && !Overflow; ++z) {
2060 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2062 if (LargerThan64Bits)
2063 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2065 Coeff = Coeff1*Coeff2;
2066 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2067 const SCEV *Term1 = AddRec->getOperand(y-z);
2068 const SCEV *Term2 = OtherAddRec->getOperand(z);
2069 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2072 AddRecOps.push_back(Term);
2075 const SCEV *NewAddRec = getAddRecExpr(AddRecOps,
2078 if (Ops.size() == 2) return NewAddRec;
2079 Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
2080 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2085 return getMulExpr(Ops);
2089 // Otherwise couldn't fold anything into this recurrence. Move onto the
2093 // Okay, it looks like we really DO need an mul expr. Check to see if we
2094 // already have one, otherwise create a new one.
2095 FoldingSetNodeID ID;
2096 ID.AddInteger(scMulExpr);
2097 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2098 ID.AddPointer(Ops[i]);
2101 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2103 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2104 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2105 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2107 UniqueSCEVs.InsertNode(S, IP);
2109 S->setNoWrapFlags(Flags);
2113 /// getUDivExpr - Get a canonical unsigned division expression, or something
2114 /// simpler if possible.
2115 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2117 assert(getEffectiveSCEVType(LHS->getType()) ==
2118 getEffectiveSCEVType(RHS->getType()) &&
2119 "SCEVUDivExpr operand types don't match!");
2121 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2122 if (RHSC->getValue()->equalsInt(1))
2123 return LHS; // X udiv 1 --> x
2124 // If the denominator is zero, the result of the udiv is undefined. Don't
2125 // try to analyze it, because the resolution chosen here may differ from
2126 // the resolution chosen in other parts of the compiler.
2127 if (!RHSC->getValue()->isZero()) {
2128 // Determine if the division can be folded into the operands of
2130 // TODO: Generalize this to non-constants by using known-bits information.
2131 Type *Ty = LHS->getType();
2132 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2133 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2134 // For non-power-of-two values, effectively round the value up to the
2135 // nearest power of two.
2136 if (!RHSC->getValue()->getValue().isPowerOf2())
2138 IntegerType *ExtTy =
2139 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2140 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2141 if (const SCEVConstant *Step =
2142 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2143 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2144 const APInt &StepInt = Step->getValue()->getValue();
2145 const APInt &DivInt = RHSC->getValue()->getValue();
2146 if (!StepInt.urem(DivInt) &&
2147 getZeroExtendExpr(AR, ExtTy) ==
2148 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2149 getZeroExtendExpr(Step, ExtTy),
2150 AR->getLoop(), SCEV::FlagAnyWrap)) {
2151 SmallVector<const SCEV *, 4> Operands;
2152 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
2153 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
2154 return getAddRecExpr(Operands, AR->getLoop(),
2157 /// Get a canonical UDivExpr for a recurrence.
2158 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2159 // We can currently only fold X%N if X is constant.
2160 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2161 if (StartC && !DivInt.urem(StepInt) &&
2162 getZeroExtendExpr(AR, ExtTy) ==
2163 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2164 getZeroExtendExpr(Step, ExtTy),
2165 AR->getLoop(), SCEV::FlagAnyWrap)) {
2166 const APInt &StartInt = StartC->getValue()->getValue();
2167 const APInt &StartRem = StartInt.urem(StepInt);
2169 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2170 AR->getLoop(), SCEV::FlagNW);
2173 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2174 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2175 SmallVector<const SCEV *, 4> Operands;
2176 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
2177 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
2178 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2179 // Find an operand that's safely divisible.
2180 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2181 const SCEV *Op = M->getOperand(i);
2182 const SCEV *Div = getUDivExpr(Op, RHSC);
2183 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2184 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2187 return getMulExpr(Operands);
2191 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2192 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2193 SmallVector<const SCEV *, 4> Operands;
2194 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
2195 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
2196 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2198 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2199 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2200 if (isa<SCEVUDivExpr>(Op) ||
2201 getMulExpr(Op, RHS) != A->getOperand(i))
2203 Operands.push_back(Op);
2205 if (Operands.size() == A->getNumOperands())
2206 return getAddExpr(Operands);
2210 // Fold if both operands are constant.
2211 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2212 Constant *LHSCV = LHSC->getValue();
2213 Constant *RHSCV = RHSC->getValue();
2214 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2220 FoldingSetNodeID ID;
2221 ID.AddInteger(scUDivExpr);
2225 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2226 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2228 UniqueSCEVs.InsertNode(S, IP);
2233 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2234 /// Simplify the expression as much as possible.
2235 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2237 SCEV::NoWrapFlags Flags) {
2238 SmallVector<const SCEV *, 4> Operands;
2239 Operands.push_back(Start);
2240 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2241 if (StepChrec->getLoop() == L) {
2242 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2243 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2246 Operands.push_back(Step);
2247 return getAddRecExpr(Operands, L, Flags);
2250 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2251 /// Simplify the expression as much as possible.
2253 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2254 const Loop *L, SCEV::NoWrapFlags Flags) {
2255 if (Operands.size() == 1) return Operands[0];
2257 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2258 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2259 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2260 "SCEVAddRecExpr operand types don't match!");
2261 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2262 assert(isLoopInvariant(Operands[i], L) &&
2263 "SCEVAddRecExpr operand is not loop-invariant!");
2266 if (Operands.back()->isZero()) {
2267 Operands.pop_back();
2268 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2271 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2272 // use that information to infer NUW and NSW flags. However, computing a
2273 // BE count requires calling getAddRecExpr, so we may not yet have a
2274 // meaningful BE count at this point (and if we don't, we'd be stuck
2275 // with a SCEVCouldNotCompute as the cached BE count).
2277 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2279 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2280 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2281 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2283 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2284 E = Operands.end(); I != E; ++I)
2285 if (!isKnownNonNegative(*I)) {
2289 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2292 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2293 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2294 const Loop *NestedLoop = NestedAR->getLoop();
2295 if (L->contains(NestedLoop) ?
2296 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2297 (!NestedLoop->contains(L) &&
2298 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2299 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2300 NestedAR->op_end());
2301 Operands[0] = NestedAR->getStart();
2302 // AddRecs require their operands be loop-invariant with respect to their
2303 // loops. Don't perform this transformation if it would break this
2305 bool AllInvariant = true;
2306 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2307 if (!isLoopInvariant(Operands[i], L)) {
2308 AllInvariant = false;
2312 // Create a recurrence for the outer loop with the same step size.
2314 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2315 // inner recurrence has the same property.
2316 SCEV::NoWrapFlags OuterFlags =
2317 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2319 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2320 AllInvariant = true;
2321 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2322 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2323 AllInvariant = false;
2327 // Ok, both add recurrences are valid after the transformation.
2329 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2330 // the outer recurrence has the same property.
2331 SCEV::NoWrapFlags InnerFlags =
2332 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2333 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2336 // Reset Operands to its original state.
2337 Operands[0] = NestedAR;
2341 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2342 // already have one, otherwise create a new one.
2343 FoldingSetNodeID ID;
2344 ID.AddInteger(scAddRecExpr);
2345 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2346 ID.AddPointer(Operands[i]);
2350 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2352 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2353 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2354 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2355 O, Operands.size(), L);
2356 UniqueSCEVs.InsertNode(S, IP);
2358 S->setNoWrapFlags(Flags);
2362 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2364 SmallVector<const SCEV *, 2> Ops;
2367 return getSMaxExpr(Ops);
2371 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2372 assert(!Ops.empty() && "Cannot get empty smax!");
2373 if (Ops.size() == 1) return Ops[0];
2375 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2376 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2377 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2378 "SCEVSMaxExpr operand types don't match!");
2381 // Sort by complexity, this groups all similar expression types together.
2382 GroupByComplexity(Ops, LI);
2384 // If there are any constants, fold them together.
2386 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2388 assert(Idx < Ops.size());
2389 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2390 // We found two constants, fold them together!
2391 ConstantInt *Fold = ConstantInt::get(getContext(),
2392 APIntOps::smax(LHSC->getValue()->getValue(),
2393 RHSC->getValue()->getValue()));
2394 Ops[0] = getConstant(Fold);
2395 Ops.erase(Ops.begin()+1); // Erase the folded element
2396 if (Ops.size() == 1) return Ops[0];
2397 LHSC = cast<SCEVConstant>(Ops[0]);
2400 // If we are left with a constant minimum-int, strip it off.
2401 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2402 Ops.erase(Ops.begin());
2404 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2405 // If we have an smax with a constant maximum-int, it will always be
2410 if (Ops.size() == 1) return Ops[0];
2413 // Find the first SMax
2414 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2417 // Check to see if one of the operands is an SMax. If so, expand its operands
2418 // onto our operand list, and recurse to simplify.
2419 if (Idx < Ops.size()) {
2420 bool DeletedSMax = false;
2421 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2422 Ops.erase(Ops.begin()+Idx);
2423 Ops.append(SMax->op_begin(), SMax->op_end());
2428 return getSMaxExpr(Ops);
2431 // Okay, check to see if the same value occurs in the operand list twice. If
2432 // so, delete one. Since we sorted the list, these values are required to
2434 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2435 // X smax Y smax Y --> X smax Y
2436 // X smax Y --> X, if X is always greater than Y
2437 if (Ops[i] == Ops[i+1] ||
2438 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2439 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2441 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2442 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2446 if (Ops.size() == 1) return Ops[0];
2448 assert(!Ops.empty() && "Reduced smax down to nothing!");
2450 // Okay, it looks like we really DO need an smax expr. Check to see if we
2451 // already have one, otherwise create a new one.
2452 FoldingSetNodeID ID;
2453 ID.AddInteger(scSMaxExpr);
2454 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2455 ID.AddPointer(Ops[i]);
2457 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2458 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2459 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2460 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2462 UniqueSCEVs.InsertNode(S, IP);
2466 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2468 SmallVector<const SCEV *, 2> Ops;
2471 return getUMaxExpr(Ops);
2475 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2476 assert(!Ops.empty() && "Cannot get empty umax!");
2477 if (Ops.size() == 1) return Ops[0];
2479 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2480 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2481 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2482 "SCEVUMaxExpr operand types don't match!");
2485 // Sort by complexity, this groups all similar expression types together.
2486 GroupByComplexity(Ops, LI);
2488 // If there are any constants, fold them together.
2490 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2492 assert(Idx < Ops.size());
2493 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2494 // We found two constants, fold them together!
2495 ConstantInt *Fold = ConstantInt::get(getContext(),
2496 APIntOps::umax(LHSC->getValue()->getValue(),
2497 RHSC->getValue()->getValue()));
2498 Ops[0] = getConstant(Fold);
2499 Ops.erase(Ops.begin()+1); // Erase the folded element
2500 if (Ops.size() == 1) return Ops[0];
2501 LHSC = cast<SCEVConstant>(Ops[0]);
2504 // If we are left with a constant minimum-int, strip it off.
2505 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2506 Ops.erase(Ops.begin());
2508 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2509 // If we have an umax with a constant maximum-int, it will always be
2514 if (Ops.size() == 1) return Ops[0];
2517 // Find the first UMax
2518 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2521 // Check to see if one of the operands is a UMax. If so, expand its operands
2522 // onto our operand list, and recurse to simplify.
2523 if (Idx < Ops.size()) {
2524 bool DeletedUMax = false;
2525 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2526 Ops.erase(Ops.begin()+Idx);
2527 Ops.append(UMax->op_begin(), UMax->op_end());
2532 return getUMaxExpr(Ops);
2535 // Okay, check to see if the same value occurs in the operand list twice. If
2536 // so, delete one. Since we sorted the list, these values are required to
2538 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2539 // X umax Y umax Y --> X umax Y
2540 // X umax Y --> X, if X is always greater than Y
2541 if (Ops[i] == Ops[i+1] ||
2542 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2543 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2545 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2546 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2550 if (Ops.size() == 1) return Ops[0];
2552 assert(!Ops.empty() && "Reduced umax down to nothing!");
2554 // Okay, it looks like we really DO need a umax expr. Check to see if we
2555 // already have one, otherwise create a new one.
2556 FoldingSetNodeID ID;
2557 ID.AddInteger(scUMaxExpr);
2558 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2559 ID.AddPointer(Ops[i]);
2561 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2562 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2563 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2564 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2566 UniqueSCEVs.InsertNode(S, IP);
2570 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2572 // ~smax(~x, ~y) == smin(x, y).
2573 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2576 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2578 // ~umax(~x, ~y) == umin(x, y)
2579 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2582 const SCEV *ScalarEvolution::getSizeOfExpr(Type *AllocTy) {
2583 // If we have TargetData, we can bypass creating a target-independent
2584 // constant expression and then folding it back into a ConstantInt.
2585 // This is just a compile-time optimization.
2587 return getConstant(TD->getIntPtrType(getContext()),
2588 TD->getTypeAllocSize(AllocTy));
2590 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2591 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2592 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2594 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2595 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2598 const SCEV *ScalarEvolution::getAlignOfExpr(Type *AllocTy) {
2599 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2600 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2601 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2603 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2604 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2607 const SCEV *ScalarEvolution::getOffsetOfExpr(StructType *STy,
2609 // If we have TargetData, we can bypass creating a target-independent
2610 // constant expression and then folding it back into a ConstantInt.
2611 // This is just a compile-time optimization.
2613 return getConstant(TD->getIntPtrType(getContext()),
2614 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2616 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2617 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2618 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2620 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2621 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2624 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *CTy,
2625 Constant *FieldNo) {
2626 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2627 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2628 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2630 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2631 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2634 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2635 // Don't attempt to do anything other than create a SCEVUnknown object
2636 // here. createSCEV only calls getUnknown after checking for all other
2637 // interesting possibilities, and any other code that calls getUnknown
2638 // is doing so in order to hide a value from SCEV canonicalization.
2640 FoldingSetNodeID ID;
2641 ID.AddInteger(scUnknown);
2644 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
2645 assert(cast<SCEVUnknown>(S)->getValue() == V &&
2646 "Stale SCEVUnknown in uniquing map!");
2649 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
2651 FirstUnknown = cast<SCEVUnknown>(S);
2652 UniqueSCEVs.InsertNode(S, IP);
2656 //===----------------------------------------------------------------------===//
2657 // Basic SCEV Analysis and PHI Idiom Recognition Code
2660 /// isSCEVable - Test if values of the given type are analyzable within
2661 /// the SCEV framework. This primarily includes integer types, and it
2662 /// can optionally include pointer types if the ScalarEvolution class
2663 /// has access to target-specific information.
2664 bool ScalarEvolution::isSCEVable(Type *Ty) const {
2665 // Integers and pointers are always SCEVable.
2666 return Ty->isIntegerTy() || Ty->isPointerTy();
2669 /// getTypeSizeInBits - Return the size in bits of the specified type,
2670 /// for which isSCEVable must return true.
2671 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
2672 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2674 // If we have a TargetData, use it!
2676 return TD->getTypeSizeInBits(Ty);
2678 // Integer types have fixed sizes.
2679 if (Ty->isIntegerTy())
2680 return Ty->getPrimitiveSizeInBits();
2682 // The only other support type is pointer. Without TargetData, conservatively
2683 // assume pointers are 64-bit.
2684 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2688 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2689 /// the given type and which represents how SCEV will treat the given
2690 /// type, for which isSCEVable must return true. For pointer types,
2691 /// this is the pointer-sized integer type.
2692 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
2693 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2695 if (Ty->isIntegerTy())
2698 // The only other support type is pointer.
2699 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2700 if (TD) return TD->getIntPtrType(getContext());
2702 // Without TargetData, conservatively assume pointers are 64-bit.
2703 return Type::getInt64Ty(getContext());
2706 const SCEV *ScalarEvolution::getCouldNotCompute() {
2707 return &CouldNotCompute;
2710 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2711 /// expression and create a new one.
2712 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2713 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2715 ValueExprMapType::const_iterator I = ValueExprMap.find(V);
2716 if (I != ValueExprMap.end()) return I->second;
2717 const SCEV *S = createSCEV(V);
2719 // The process of creating a SCEV for V may have caused other SCEVs
2720 // to have been created, so it's necessary to insert the new entry
2721 // from scratch, rather than trying to remember the insert position
2723 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2727 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2729 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2730 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2732 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2734 Type *Ty = V->getType();
2735 Ty = getEffectiveSCEVType(Ty);
2736 return getMulExpr(V,
2737 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2740 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2741 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2742 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2744 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2746 Type *Ty = V->getType();
2747 Ty = getEffectiveSCEVType(Ty);
2748 const SCEV *AllOnes =
2749 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2750 return getMinusSCEV(AllOnes, V);
2753 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
2754 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
2755 SCEV::NoWrapFlags Flags) {
2756 assert(!maskFlags(Flags, SCEV::FlagNUW) && "subtraction does not have NUW");
2758 // Fast path: X - X --> 0.
2760 return getConstant(LHS->getType(), 0);
2763 return getAddExpr(LHS, getNegativeSCEV(RHS), Flags);
2766 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2767 /// input value to the specified type. If the type must be extended, it is zero
2770 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
2771 Type *SrcTy = V->getType();
2772 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2773 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2774 "Cannot truncate or zero extend with non-integer arguments!");
2775 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2776 return V; // No conversion
2777 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2778 return getTruncateExpr(V, Ty);
2779 return getZeroExtendExpr(V, Ty);
2782 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2783 /// input value to the specified type. If the type must be extended, it is sign
2786 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2788 Type *SrcTy = V->getType();
2789 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2790 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2791 "Cannot truncate or zero extend with non-integer arguments!");
2792 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2793 return V; // No conversion
2794 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2795 return getTruncateExpr(V, Ty);
2796 return getSignExtendExpr(V, Ty);
2799 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2800 /// input value to the specified type. If the type must be extended, it is zero
2801 /// extended. The conversion must not be narrowing.
2803 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
2804 Type *SrcTy = V->getType();
2805 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2806 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2807 "Cannot noop or zero extend with non-integer arguments!");
2808 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2809 "getNoopOrZeroExtend cannot truncate!");
2810 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2811 return V; // No conversion
2812 return getZeroExtendExpr(V, Ty);
2815 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2816 /// input value to the specified type. If the type must be extended, it is sign
2817 /// extended. The conversion must not be narrowing.
2819 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
2820 Type *SrcTy = V->getType();
2821 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2822 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2823 "Cannot noop or sign extend with non-integer arguments!");
2824 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2825 "getNoopOrSignExtend cannot truncate!");
2826 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2827 return V; // No conversion
2828 return getSignExtendExpr(V, Ty);
2831 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2832 /// the input value to the specified type. If the type must be extended,
2833 /// it is extended with unspecified bits. The conversion must not be
2836 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
2837 Type *SrcTy = V->getType();
2838 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2839 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2840 "Cannot noop or any extend with non-integer arguments!");
2841 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2842 "getNoopOrAnyExtend cannot truncate!");
2843 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2844 return V; // No conversion
2845 return getAnyExtendExpr(V, Ty);
2848 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2849 /// input value to the specified type. The conversion must not be widening.
2851 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
2852 Type *SrcTy = V->getType();
2853 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2854 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2855 "Cannot truncate or noop with non-integer arguments!");
2856 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2857 "getTruncateOrNoop cannot extend!");
2858 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2859 return V; // No conversion
2860 return getTruncateExpr(V, Ty);
2863 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2864 /// the types using zero-extension, and then perform a umax operation
2866 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2868 const SCEV *PromotedLHS = LHS;
2869 const SCEV *PromotedRHS = RHS;
2871 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2872 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2874 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2876 return getUMaxExpr(PromotedLHS, PromotedRHS);
2879 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2880 /// the types using zero-extension, and then perform a umin operation
2882 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2884 const SCEV *PromotedLHS = LHS;
2885 const SCEV *PromotedRHS = RHS;
2887 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2888 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2890 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2892 return getUMinExpr(PromotedLHS, PromotedRHS);
2895 /// getPointerBase - Transitively follow the chain of pointer-type operands
2896 /// until reaching a SCEV that does not have a single pointer operand. This
2897 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
2898 /// but corner cases do exist.
2899 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
2900 // A pointer operand may evaluate to a nonpointer expression, such as null.
2901 if (!V->getType()->isPointerTy())
2904 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
2905 return getPointerBase(Cast->getOperand());
2907 else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
2908 const SCEV *PtrOp = 0;
2909 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
2911 if ((*I)->getType()->isPointerTy()) {
2912 // Cannot find the base of an expression with multiple pointer operands.
2920 return getPointerBase(PtrOp);
2925 /// PushDefUseChildren - Push users of the given Instruction
2926 /// onto the given Worklist.
2928 PushDefUseChildren(Instruction *I,
2929 SmallVectorImpl<Instruction *> &Worklist) {
2930 // Push the def-use children onto the Worklist stack.
2931 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2933 Worklist.push_back(cast<Instruction>(*UI));
2936 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2937 /// instructions that depend on the given instruction and removes them from
2938 /// the ValueExprMapType map if they reference SymName. This is used during PHI
2941 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2942 SmallVector<Instruction *, 16> Worklist;
2943 PushDefUseChildren(PN, Worklist);
2945 SmallPtrSet<Instruction *, 8> Visited;
2947 while (!Worklist.empty()) {
2948 Instruction *I = Worklist.pop_back_val();
2949 if (!Visited.insert(I)) continue;
2951 ValueExprMapType::iterator It =
2952 ValueExprMap.find(static_cast<Value *>(I));
2953 if (It != ValueExprMap.end()) {
2954 const SCEV *Old = It->second;
2956 // Short-circuit the def-use traversal if the symbolic name
2957 // ceases to appear in expressions.
2958 if (Old != SymName && !hasOperand(Old, SymName))
2961 // SCEVUnknown for a PHI either means that it has an unrecognized
2962 // structure, it's a PHI that's in the progress of being computed
2963 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2964 // additional loop trip count information isn't going to change anything.
2965 // In the second case, createNodeForPHI will perform the necessary
2966 // updates on its own when it gets to that point. In the third, we do
2967 // want to forget the SCEVUnknown.
2968 if (!isa<PHINode>(I) ||
2969 !isa<SCEVUnknown>(Old) ||
2970 (I != PN && Old == SymName)) {
2971 forgetMemoizedResults(Old);
2972 ValueExprMap.erase(It);
2976 PushDefUseChildren(I, Worklist);
2980 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2981 /// a loop header, making it a potential recurrence, or it doesn't.
2983 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2984 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2985 if (L->getHeader() == PN->getParent()) {
2986 // The loop may have multiple entrances or multiple exits; we can analyze
2987 // this phi as an addrec if it has a unique entry value and a unique
2989 Value *BEValueV = 0, *StartValueV = 0;
2990 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2991 Value *V = PN->getIncomingValue(i);
2992 if (L->contains(PN->getIncomingBlock(i))) {
2995 } else if (BEValueV != V) {
2999 } else if (!StartValueV) {
3001 } else if (StartValueV != V) {
3006 if (BEValueV && StartValueV) {
3007 // While we are analyzing this PHI node, handle its value symbolically.
3008 const SCEV *SymbolicName = getUnknown(PN);
3009 assert(ValueExprMap.find(PN) == ValueExprMap.end() &&
3010 "PHI node already processed?");
3011 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
3013 // Using this symbolic name for the PHI, analyze the value coming around
3015 const SCEV *BEValue = getSCEV(BEValueV);
3017 // NOTE: If BEValue is loop invariant, we know that the PHI node just
3018 // has a special value for the first iteration of the loop.
3020 // If the value coming around the backedge is an add with the symbolic
3021 // value we just inserted, then we found a simple induction variable!
3022 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
3023 // If there is a single occurrence of the symbolic value, replace it
3024 // with a recurrence.
3025 unsigned FoundIndex = Add->getNumOperands();
3026 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3027 if (Add->getOperand(i) == SymbolicName)
3028 if (FoundIndex == e) {
3033 if (FoundIndex != Add->getNumOperands()) {
3034 // Create an add with everything but the specified operand.
3035 SmallVector<const SCEV *, 8> Ops;
3036 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
3037 if (i != FoundIndex)
3038 Ops.push_back(Add->getOperand(i));
3039 const SCEV *Accum = getAddExpr(Ops);
3041 // This is not a valid addrec if the step amount is varying each
3042 // loop iteration, but is not itself an addrec in this loop.
3043 if (isLoopInvariant(Accum, L) ||
3044 (isa<SCEVAddRecExpr>(Accum) &&
3045 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
3046 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3048 // If the increment doesn't overflow, then neither the addrec nor
3049 // the post-increment will overflow.
3050 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
3051 if (OBO->hasNoUnsignedWrap())
3052 Flags = setFlags(Flags, SCEV::FlagNUW);
3053 if (OBO->hasNoSignedWrap())
3054 Flags = setFlags(Flags, SCEV::FlagNSW);
3055 } else if (const GEPOperator *GEP =
3056 dyn_cast<GEPOperator>(BEValueV)) {
3057 // If the increment is an inbounds GEP, then we know the address
3058 // space cannot be wrapped around. We cannot make any guarantee
3059 // about signed or unsigned overflow because pointers are
3060 // unsigned but we may have a negative index from the base
3062 if (GEP->isInBounds())
3063 Flags = setFlags(Flags, SCEV::FlagNW);
3066 const SCEV *StartVal = getSCEV(StartValueV);
3067 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
3069 // Since the no-wrap flags are on the increment, they apply to the
3070 // post-incremented value as well.
3071 if (isLoopInvariant(Accum, L))
3072 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
3075 // Okay, for the entire analysis of this edge we assumed the PHI
3076 // to be symbolic. We now need to go back and purge all of the
3077 // entries for the scalars that use the symbolic expression.
3078 ForgetSymbolicName(PN, SymbolicName);
3079 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3083 } else if (const SCEVAddRecExpr *AddRec =
3084 dyn_cast<SCEVAddRecExpr>(BEValue)) {
3085 // Otherwise, this could be a loop like this:
3086 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
3087 // In this case, j = {1,+,1} and BEValue is j.
3088 // Because the other in-value of i (0) fits the evolution of BEValue
3089 // i really is an addrec evolution.
3090 if (AddRec->getLoop() == L && AddRec->isAffine()) {
3091 const SCEV *StartVal = getSCEV(StartValueV);
3093 // If StartVal = j.start - j.stride, we can use StartVal as the
3094 // initial step of the addrec evolution.
3095 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
3096 AddRec->getOperand(1))) {
3097 // FIXME: For constant StartVal, we should be able to infer
3099 const SCEV *PHISCEV =
3100 getAddRecExpr(StartVal, AddRec->getOperand(1), L,
3103 // Okay, for the entire analysis of this edge we assumed the PHI
3104 // to be symbolic. We now need to go back and purge all of the
3105 // entries for the scalars that use the symbolic expression.
3106 ForgetSymbolicName(PN, SymbolicName);
3107 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3115 // If the PHI has a single incoming value, follow that value, unless the
3116 // PHI's incoming blocks are in a different loop, in which case doing so
3117 // risks breaking LCSSA form. Instcombine would normally zap these, but
3118 // it doesn't have DominatorTree information, so it may miss cases.
3119 if (Value *V = SimplifyInstruction(PN, TD, DT))
3120 if (LI->replacementPreservesLCSSAForm(PN, V))
3123 // If it's not a loop phi, we can't handle it yet.
3124 return getUnknown(PN);
3127 /// createNodeForGEP - Expand GEP instructions into add and multiply
3128 /// operations. This allows them to be analyzed by regular SCEV code.
3130 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
3132 // Don't blindly transfer the inbounds flag from the GEP instruction to the
3133 // Add expression, because the Instruction may be guarded by control flow
3134 // and the no-overflow bits may not be valid for the expression in any
3136 bool isInBounds = GEP->isInBounds();
3138 Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
3139 Value *Base = GEP->getOperand(0);
3140 // Don't attempt to analyze GEPs over unsized objects.
3141 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
3142 return getUnknown(GEP);
3143 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
3144 gep_type_iterator GTI = gep_type_begin(GEP);
3145 for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
3149 // Compute the (potentially symbolic) offset in bytes for this index.
3150 if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
3151 // For a struct, add the member offset.
3152 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
3153 const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
3155 // Add the field offset to the running total offset.
3156 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3158 // For an array, add the element offset, explicitly scaled.
3159 const SCEV *ElementSize = getSizeOfExpr(*GTI);
3160 const SCEV *IndexS = getSCEV(Index);
3161 // Getelementptr indices are signed.
3162 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
3164 // Multiply the index by the element size to compute the element offset.
3165 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize,
3166 isInBounds ? SCEV::FlagNSW :
3169 // Add the element offset to the running total offset.
3170 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3174 // Get the SCEV for the GEP base.
3175 const SCEV *BaseS = getSCEV(Base);
3177 // Add the total offset from all the GEP indices to the base.
3178 return getAddExpr(BaseS, TotalOffset,
3179 isInBounds ? SCEV::FlagNSW : SCEV::FlagAnyWrap);
3182 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
3183 /// guaranteed to end in (at every loop iteration). It is, at the same time,
3184 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
3185 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
3187 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
3188 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3189 return C->getValue()->getValue().countTrailingZeros();
3191 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
3192 return std::min(GetMinTrailingZeros(T->getOperand()),
3193 (uint32_t)getTypeSizeInBits(T->getType()));
3195 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
3196 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3197 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3198 getTypeSizeInBits(E->getType()) : OpRes;
3201 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
3202 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3203 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3204 getTypeSizeInBits(E->getType()) : OpRes;
3207 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
3208 // The result is the min of all operands results.
3209 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3210 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3211 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3215 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
3216 // The result is the sum of all operands results.
3217 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
3218 uint32_t BitWidth = getTypeSizeInBits(M->getType());
3219 for (unsigned i = 1, e = M->getNumOperands();
3220 SumOpRes != BitWidth && i != e; ++i)
3221 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
3226 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
3227 // The result is the min of all operands results.
3228 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3229 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3230 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3234 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
3235 // The result is the min of all operands results.
3236 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3237 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3238 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3242 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
3243 // The result is the min of all operands results.
3244 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3245 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3246 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3250 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3251 // For a SCEVUnknown, ask ValueTracking.
3252 unsigned BitWidth = getTypeSizeInBits(U->getType());
3253 APInt Mask = APInt::getAllOnesValue(BitWidth);
3254 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3255 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
3256 return Zeros.countTrailingOnes();
3263 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
3266 ScalarEvolution::getUnsignedRange(const SCEV *S) {
3267 // See if we've computed this range already.
3268 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
3269 if (I != UnsignedRanges.end())
3272 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3273 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
3275 unsigned BitWidth = getTypeSizeInBits(S->getType());
3276 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3278 // If the value has known zeros, the maximum unsigned value will have those
3279 // known zeros as well.
3280 uint32_t TZ = GetMinTrailingZeros(S);
3282 ConservativeResult =
3283 ConstantRange(APInt::getMinValue(BitWidth),
3284 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3286 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3287 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3288 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3289 X = X.add(getUnsignedRange(Add->getOperand(i)));
3290 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3293 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3294 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3295 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3296 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3297 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3300 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3301 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3302 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3303 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3304 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3307 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3308 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3309 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3310 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3311 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3314 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3315 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3316 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3317 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3320 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3321 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3322 return setUnsignedRange(ZExt,
3323 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3326 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3327 ConstantRange X = getUnsignedRange(SExt->getOperand());
3328 return setUnsignedRange(SExt,
3329 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3332 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3333 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3334 return setUnsignedRange(Trunc,
3335 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3338 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3339 // If there's no unsigned wrap, the value will never be less than its
3341 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
3342 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3343 if (!C->getValue()->isZero())
3344 ConservativeResult =
3345 ConservativeResult.intersectWith(
3346 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3348 // TODO: non-affine addrec
3349 if (AddRec->isAffine()) {
3350 Type *Ty = AddRec->getType();
3351 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3352 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3353 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3354 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3356 const SCEV *Start = AddRec->getStart();
3357 const SCEV *Step = AddRec->getStepRecurrence(*this);
3359 ConstantRange StartRange = getUnsignedRange(Start);
3360 ConstantRange StepRange = getSignedRange(Step);
3361 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3362 ConstantRange EndRange =
3363 StartRange.add(MaxBECountRange.multiply(StepRange));
3365 // Check for overflow. This must be done with ConstantRange arithmetic
3366 // because we could be called from within the ScalarEvolution overflow
3368 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3369 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3370 ConstantRange ExtMaxBECountRange =
3371 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3372 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3373 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3375 return setUnsignedRange(AddRec, ConservativeResult);
3377 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3378 EndRange.getUnsignedMin());
3379 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3380 EndRange.getUnsignedMax());
3381 if (Min.isMinValue() && Max.isMaxValue())
3382 return setUnsignedRange(AddRec, ConservativeResult);
3383 return setUnsignedRange(AddRec,
3384 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3388 return setUnsignedRange(AddRec, ConservativeResult);
3391 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3392 // For a SCEVUnknown, ask ValueTracking.
3393 APInt Mask = APInt::getAllOnesValue(BitWidth);
3394 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3395 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3396 if (Ones == ~Zeros + 1)
3397 return setUnsignedRange(U, ConservativeResult);
3398 return setUnsignedRange(U,
3399 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3402 return setUnsignedRange(S, ConservativeResult);
3405 /// getSignedRange - Determine the signed range for a particular SCEV.
3408 ScalarEvolution::getSignedRange(const SCEV *S) {
3409 // See if we've computed this range already.
3410 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3411 if (I != SignedRanges.end())
3414 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3415 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3417 unsigned BitWidth = getTypeSizeInBits(S->getType());
3418 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3420 // If the value has known zeros, the maximum signed value will have those
3421 // known zeros as well.
3422 uint32_t TZ = GetMinTrailingZeros(S);
3424 ConservativeResult =
3425 ConstantRange(APInt::getSignedMinValue(BitWidth),
3426 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3428 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3429 ConstantRange X = getSignedRange(Add->getOperand(0));
3430 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3431 X = X.add(getSignedRange(Add->getOperand(i)));
3432 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3435 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3436 ConstantRange X = getSignedRange(Mul->getOperand(0));
3437 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3438 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3439 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3442 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3443 ConstantRange X = getSignedRange(SMax->getOperand(0));
3444 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3445 X = X.smax(getSignedRange(SMax->getOperand(i)));
3446 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3449 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3450 ConstantRange X = getSignedRange(UMax->getOperand(0));
3451 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3452 X = X.umax(getSignedRange(UMax->getOperand(i)));
3453 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3456 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3457 ConstantRange X = getSignedRange(UDiv->getLHS());
3458 ConstantRange Y = getSignedRange(UDiv->getRHS());
3459 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3462 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3463 ConstantRange X = getSignedRange(ZExt->getOperand());
3464 return setSignedRange(ZExt,
3465 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3468 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3469 ConstantRange X = getSignedRange(SExt->getOperand());
3470 return setSignedRange(SExt,
3471 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3474 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3475 ConstantRange X = getSignedRange(Trunc->getOperand());
3476 return setSignedRange(Trunc,
3477 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3480 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3481 // If there's no signed wrap, and all the operands have the same sign or
3482 // zero, the value won't ever change sign.
3483 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
3484 bool AllNonNeg = true;
3485 bool AllNonPos = true;
3486 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3487 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3488 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3491 ConservativeResult = ConservativeResult.intersectWith(
3492 ConstantRange(APInt(BitWidth, 0),
3493 APInt::getSignedMinValue(BitWidth)));
3495 ConservativeResult = ConservativeResult.intersectWith(
3496 ConstantRange(APInt::getSignedMinValue(BitWidth),
3497 APInt(BitWidth, 1)));
3500 // TODO: non-affine addrec
3501 if (AddRec->isAffine()) {
3502 Type *Ty = AddRec->getType();
3503 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3504 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3505 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3506 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3508 const SCEV *Start = AddRec->getStart();
3509 const SCEV *Step = AddRec->getStepRecurrence(*this);
3511 ConstantRange StartRange = getSignedRange(Start);
3512 ConstantRange StepRange = getSignedRange(Step);
3513 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3514 ConstantRange EndRange =
3515 StartRange.add(MaxBECountRange.multiply(StepRange));
3517 // Check for overflow. This must be done with ConstantRange arithmetic
3518 // because we could be called from within the ScalarEvolution overflow
3520 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3521 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3522 ConstantRange ExtMaxBECountRange =
3523 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3524 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3525 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3527 return setSignedRange(AddRec, ConservativeResult);
3529 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3530 EndRange.getSignedMin());
3531 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3532 EndRange.getSignedMax());
3533 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3534 return setSignedRange(AddRec, ConservativeResult);
3535 return setSignedRange(AddRec,
3536 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3540 return setSignedRange(AddRec, ConservativeResult);
3543 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3544 // For a SCEVUnknown, ask ValueTracking.
3545 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3546 return setSignedRange(U, ConservativeResult);
3547 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3549 return setSignedRange(U, ConservativeResult);
3550 return setSignedRange(U, ConservativeResult.intersectWith(
3551 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3552 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
3555 return setSignedRange(S, ConservativeResult);
3558 /// createSCEV - We know that there is no SCEV for the specified value.
3559 /// Analyze the expression.
3561 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3562 if (!isSCEVable(V->getType()))
3563 return getUnknown(V);
3565 unsigned Opcode = Instruction::UserOp1;
3566 if (Instruction *I = dyn_cast<Instruction>(V)) {
3567 Opcode = I->getOpcode();
3569 // Don't attempt to analyze instructions in blocks that aren't
3570 // reachable. Such instructions don't matter, and they aren't required
3571 // to obey basic rules for definitions dominating uses which this
3572 // analysis depends on.
3573 if (!DT->isReachableFromEntry(I->getParent()))
3574 return getUnknown(V);
3575 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3576 Opcode = CE->getOpcode();
3577 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3578 return getConstant(CI);
3579 else if (isa<ConstantPointerNull>(V))
3580 return getConstant(V->getType(), 0);
3581 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3582 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3584 return getUnknown(V);
3586 Operator *U = cast<Operator>(V);
3588 case Instruction::Add: {
3589 // The simple thing to do would be to just call getSCEV on both operands
3590 // and call getAddExpr with the result. However if we're looking at a
3591 // bunch of things all added together, this can be quite inefficient,
3592 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3593 // Instead, gather up all the operands and make a single getAddExpr call.
3594 // LLVM IR canonical form means we need only traverse the left operands.
3595 SmallVector<const SCEV *, 4> AddOps;
3596 AddOps.push_back(getSCEV(U->getOperand(1)));
3597 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
3598 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
3599 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
3601 U = cast<Operator>(Op);
3602 const SCEV *Op1 = getSCEV(U->getOperand(1));
3603 if (Opcode == Instruction::Sub)
3604 AddOps.push_back(getNegativeSCEV(Op1));
3606 AddOps.push_back(Op1);
3608 AddOps.push_back(getSCEV(U->getOperand(0)));
3609 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
3610 OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(V);
3611 if (OBO->hasNoSignedWrap())
3612 Flags = setFlags(Flags, SCEV::FlagNSW);
3613 if (OBO->hasNoUnsignedWrap())
3614 Flags = setFlags(Flags, SCEV::FlagNUW);
3615 return getAddExpr(AddOps, Flags);
3617 case Instruction::Mul: {
3618 // See the Add code above.
3619 SmallVector<const SCEV *, 4> MulOps;
3620 MulOps.push_back(getSCEV(U->getOperand(1)));
3621 for (Value *Op = U->getOperand(0);
3622 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
3623 Op = U->getOperand(0)) {
3624 U = cast<Operator>(Op);
3625 MulOps.push_back(getSCEV(U->getOperand(1)));
3627 MulOps.push_back(getSCEV(U->getOperand(0)));
3628 return getMulExpr(MulOps);
3630 case Instruction::UDiv:
3631 return getUDivExpr(getSCEV(U->getOperand(0)),
3632 getSCEV(U->getOperand(1)));
3633 case Instruction::Sub:
3634 return getMinusSCEV(getSCEV(U->getOperand(0)),
3635 getSCEV(U->getOperand(1)));
3636 case Instruction::And:
3637 // For an expression like x&255 that merely masks off the high bits,
3638 // use zext(trunc(x)) as the SCEV expression.
3639 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3640 if (CI->isNullValue())
3641 return getSCEV(U->getOperand(1));
3642 if (CI->isAllOnesValue())
3643 return getSCEV(U->getOperand(0));
3644 const APInt &A = CI->getValue();
3646 // Instcombine's ShrinkDemandedConstant may strip bits out of
3647 // constants, obscuring what would otherwise be a low-bits mask.
3648 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3649 // knew about to reconstruct a low-bits mask value.
3650 unsigned LZ = A.countLeadingZeros();
3651 unsigned BitWidth = A.getBitWidth();
3652 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3653 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3654 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3656 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3658 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3660 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3661 IntegerType::get(getContext(), BitWidth - LZ)),
3666 case Instruction::Or:
3667 // If the RHS of the Or is a constant, we may have something like:
3668 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3669 // optimizations will transparently handle this case.
3671 // In order for this transformation to be safe, the LHS must be of the
3672 // form X*(2^n) and the Or constant must be less than 2^n.
3673 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3674 const SCEV *LHS = getSCEV(U->getOperand(0));
3675 const APInt &CIVal = CI->getValue();
3676 if (GetMinTrailingZeros(LHS) >=
3677 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3678 // Build a plain add SCEV.
3679 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3680 // If the LHS of the add was an addrec and it has no-wrap flags,
3681 // transfer the no-wrap flags, since an or won't introduce a wrap.
3682 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3683 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3684 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
3685 OldAR->getNoWrapFlags());
3691 case Instruction::Xor:
3692 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3693 // If the RHS of the xor is a signbit, then this is just an add.
3694 // Instcombine turns add of signbit into xor as a strength reduction step.
3695 if (CI->getValue().isSignBit())
3696 return getAddExpr(getSCEV(U->getOperand(0)),
3697 getSCEV(U->getOperand(1)));
3699 // If the RHS of xor is -1, then this is a not operation.
3700 if (CI->isAllOnesValue())
3701 return getNotSCEV(getSCEV(U->getOperand(0)));
3703 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3704 // This is a variant of the check for xor with -1, and it handles
3705 // the case where instcombine has trimmed non-demanded bits out
3706 // of an xor with -1.
3707 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3708 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3709 if (BO->getOpcode() == Instruction::And &&
3710 LCI->getValue() == CI->getValue())
3711 if (const SCEVZeroExtendExpr *Z =
3712 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3713 Type *UTy = U->getType();
3714 const SCEV *Z0 = Z->getOperand();
3715 Type *Z0Ty = Z0->getType();
3716 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3718 // If C is a low-bits mask, the zero extend is serving to
3719 // mask off the high bits. Complement the operand and
3720 // re-apply the zext.
3721 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3722 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3724 // If C is a single bit, it may be in the sign-bit position
3725 // before the zero-extend. In this case, represent the xor
3726 // using an add, which is equivalent, and re-apply the zext.
3727 APInt Trunc = CI->getValue().trunc(Z0TySize);
3728 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3730 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3736 case Instruction::Shl:
3737 // Turn shift left of a constant amount into a multiply.
3738 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3739 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3741 // If the shift count is not less than the bitwidth, the result of
3742 // the shift is undefined. Don't try to analyze it, because the
3743 // resolution chosen here may differ from the resolution chosen in
3744 // other parts of the compiler.
3745 if (SA->getValue().uge(BitWidth))
3748 Constant *X = ConstantInt::get(getContext(),
3749 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3750 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3754 case Instruction::LShr:
3755 // Turn logical shift right of a constant into a unsigned divide.
3756 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3757 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3759 // If the shift count is not less than the bitwidth, the result of
3760 // the shift is undefined. Don't try to analyze it, because the
3761 // resolution chosen here may differ from the resolution chosen in
3762 // other parts of the compiler.
3763 if (SA->getValue().uge(BitWidth))
3766 Constant *X = ConstantInt::get(getContext(),
3767 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3768 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3772 case Instruction::AShr:
3773 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3774 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3775 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3776 if (L->getOpcode() == Instruction::Shl &&
3777 L->getOperand(1) == U->getOperand(1)) {
3778 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3780 // If the shift count is not less than the bitwidth, the result of
3781 // the shift is undefined. Don't try to analyze it, because the
3782 // resolution chosen here may differ from the resolution chosen in
3783 // other parts of the compiler.
3784 if (CI->getValue().uge(BitWidth))
3787 uint64_t Amt = BitWidth - CI->getZExtValue();
3788 if (Amt == BitWidth)
3789 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3791 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3792 IntegerType::get(getContext(),
3798 case Instruction::Trunc:
3799 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3801 case Instruction::ZExt:
3802 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3804 case Instruction::SExt:
3805 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3807 case Instruction::BitCast:
3808 // BitCasts are no-op casts so we just eliminate the cast.
3809 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3810 return getSCEV(U->getOperand(0));
3813 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3814 // lead to pointer expressions which cannot safely be expanded to GEPs,
3815 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3816 // simplifying integer expressions.
3818 case Instruction::GetElementPtr:
3819 return createNodeForGEP(cast<GEPOperator>(U));
3821 case Instruction::PHI:
3822 return createNodeForPHI(cast<PHINode>(U));
3824 case Instruction::Select:
3825 // This could be a smax or umax that was lowered earlier.
3826 // Try to recover it.
3827 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3828 Value *LHS = ICI->getOperand(0);
3829 Value *RHS = ICI->getOperand(1);
3830 switch (ICI->getPredicate()) {
3831 case ICmpInst::ICMP_SLT:
3832 case ICmpInst::ICMP_SLE:
3833 std::swap(LHS, RHS);
3835 case ICmpInst::ICMP_SGT:
3836 case ICmpInst::ICMP_SGE:
3837 // a >s b ? a+x : b+x -> smax(a, b)+x
3838 // a >s b ? b+x : a+x -> smin(a, b)+x
3839 if (LHS->getType() == U->getType()) {
3840 const SCEV *LS = getSCEV(LHS);
3841 const SCEV *RS = getSCEV(RHS);
3842 const SCEV *LA = getSCEV(U->getOperand(1));
3843 const SCEV *RA = getSCEV(U->getOperand(2));
3844 const SCEV *LDiff = getMinusSCEV(LA, LS);
3845 const SCEV *RDiff = getMinusSCEV(RA, RS);
3847 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3848 LDiff = getMinusSCEV(LA, RS);
3849 RDiff = getMinusSCEV(RA, LS);
3851 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3854 case ICmpInst::ICMP_ULT:
3855 case ICmpInst::ICMP_ULE:
3856 std::swap(LHS, RHS);
3858 case ICmpInst::ICMP_UGT:
3859 case ICmpInst::ICMP_UGE:
3860 // a >u b ? a+x : b+x -> umax(a, b)+x
3861 // a >u b ? b+x : a+x -> umin(a, b)+x
3862 if (LHS->getType() == U->getType()) {
3863 const SCEV *LS = getSCEV(LHS);
3864 const SCEV *RS = getSCEV(RHS);
3865 const SCEV *LA = getSCEV(U->getOperand(1));
3866 const SCEV *RA = getSCEV(U->getOperand(2));
3867 const SCEV *LDiff = getMinusSCEV(LA, LS);
3868 const SCEV *RDiff = getMinusSCEV(RA, RS);
3870 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3871 LDiff = getMinusSCEV(LA, RS);
3872 RDiff = getMinusSCEV(RA, LS);
3874 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3877 case ICmpInst::ICMP_NE:
3878 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3879 if (LHS->getType() == U->getType() &&
3880 isa<ConstantInt>(RHS) &&
3881 cast<ConstantInt>(RHS)->isZero()) {
3882 const SCEV *One = getConstant(LHS->getType(), 1);
3883 const SCEV *LS = getSCEV(LHS);
3884 const SCEV *LA = getSCEV(U->getOperand(1));
3885 const SCEV *RA = getSCEV(U->getOperand(2));
3886 const SCEV *LDiff = getMinusSCEV(LA, LS);
3887 const SCEV *RDiff = getMinusSCEV(RA, One);
3889 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3892 case ICmpInst::ICMP_EQ:
3893 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3894 if (LHS->getType() == U->getType() &&
3895 isa<ConstantInt>(RHS) &&
3896 cast<ConstantInt>(RHS)->isZero()) {
3897 const SCEV *One = getConstant(LHS->getType(), 1);
3898 const SCEV *LS = getSCEV(LHS);
3899 const SCEV *LA = getSCEV(U->getOperand(1));
3900 const SCEV *RA = getSCEV(U->getOperand(2));
3901 const SCEV *LDiff = getMinusSCEV(LA, One);
3902 const SCEV *RDiff = getMinusSCEV(RA, LS);
3904 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3912 default: // We cannot analyze this expression.
3916 return getUnknown(V);
3921 //===----------------------------------------------------------------------===//
3922 // Iteration Count Computation Code
3925 /// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
3926 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown
3927 /// or not constant. Will also return 0 if the maximum trip count is very large
3929 unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
3930 BasicBlock *ExitBlock) {
3931 const SCEVConstant *ExitCount =
3932 dyn_cast<SCEVConstant>(getExitCount(L, ExitBlock));
3936 ConstantInt *ExitConst = ExitCount->getValue();
3938 // Guard against huge trip counts.
3939 if (ExitConst->getValue().getActiveBits() > 32)
3942 // In case of integer overflow, this returns 0, which is correct.
3943 return ((unsigned)ExitConst->getZExtValue()) + 1;
3946 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the
3947 /// trip count of this loop as a normal unsigned value, if possible. This
3948 /// means that the actual trip count is always a multiple of the returned
3949 /// value (don't forget the trip count could very well be zero as well!).
3951 /// Returns 1 if the trip count is unknown or not guaranteed to be the
3952 /// multiple of a constant (which is also the case if the trip count is simply
3953 /// constant, use getSmallConstantTripCount for that case), Will also return 1
3954 /// if the trip count is very large (>= 2^32).
3955 unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
3956 BasicBlock *ExitBlock) {
3957 const SCEV *ExitCount = getExitCount(L, ExitBlock);
3958 if (ExitCount == getCouldNotCompute())
3961 // Get the trip count from the BE count by adding 1.
3962 const SCEV *TCMul = getAddExpr(ExitCount,
3963 getConstant(ExitCount->getType(), 1));
3964 // FIXME: SCEV distributes multiplication as V1*C1 + V2*C1. We could attempt
3965 // to factor simple cases.
3966 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(TCMul))
3967 TCMul = Mul->getOperand(0);
3969 const SCEVConstant *MulC = dyn_cast<SCEVConstant>(TCMul);
3973 ConstantInt *Result = MulC->getValue();
3975 // Guard against huge trip counts.
3976 if (!Result || Result->getValue().getActiveBits() > 32)
3979 return (unsigned)Result->getZExtValue();
3982 // getExitCount - Get the expression for the number of loop iterations for which
3983 // this loop is guaranteed not to exit via ExitintBlock. Otherwise return
3984 // SCEVCouldNotCompute.
3985 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
3986 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
3989 /// getBackedgeTakenCount - If the specified loop has a predictable
3990 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3991 /// object. The backedge-taken count is the number of times the loop header
3992 /// will be branched to from within the loop. This is one less than the
3993 /// trip count of the loop, since it doesn't count the first iteration,
3994 /// when the header is branched to from outside the loop.
3996 /// Note that it is not valid to call this method on a loop without a
3997 /// loop-invariant backedge-taken count (see
3998 /// hasLoopInvariantBackedgeTakenCount).
4000 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
4001 return getBackedgeTakenInfo(L).getExact(this);
4004 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
4005 /// return the least SCEV value that is known never to be less than the
4006 /// actual backedge taken count.
4007 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
4008 return getBackedgeTakenInfo(L).getMax(this);
4011 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
4012 /// onto the given Worklist.
4014 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
4015 BasicBlock *Header = L->getHeader();
4017 // Push all Loop-header PHIs onto the Worklist stack.
4018 for (BasicBlock::iterator I = Header->begin();
4019 PHINode *PN = dyn_cast<PHINode>(I); ++I)
4020 Worklist.push_back(PN);
4023 const ScalarEvolution::BackedgeTakenInfo &
4024 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
4025 // Initially insert an invalid entry for this loop. If the insertion
4026 // succeeds, proceed to actually compute a backedge-taken count and
4027 // update the value. The temporary CouldNotCompute value tells SCEV
4028 // code elsewhere that it shouldn't attempt to request a new
4029 // backedge-taken count, which could result in infinite recursion.
4030 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
4031 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
4033 return Pair.first->second;
4035 // ComputeBackedgeTakenCount may allocate memory for its result. Inserting it
4036 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
4037 // must be cleared in this scope.
4038 BackedgeTakenInfo Result = ComputeBackedgeTakenCount(L);
4040 if (Result.getExact(this) != getCouldNotCompute()) {
4041 assert(isLoopInvariant(Result.getExact(this), L) &&
4042 isLoopInvariant(Result.getMax(this), L) &&
4043 "Computed backedge-taken count isn't loop invariant for loop!");
4044 ++NumTripCountsComputed;
4046 else if (Result.getMax(this) == getCouldNotCompute() &&
4047 isa<PHINode>(L->getHeader()->begin())) {
4048 // Only count loops that have phi nodes as not being computable.
4049 ++NumTripCountsNotComputed;
4052 // Now that we know more about the trip count for this loop, forget any
4053 // existing SCEV values for PHI nodes in this loop since they are only
4054 // conservative estimates made without the benefit of trip count
4055 // information. This is similar to the code in forgetLoop, except that
4056 // it handles SCEVUnknown PHI nodes specially.
4057 if (Result.hasAnyInfo()) {
4058 SmallVector<Instruction *, 16> Worklist;
4059 PushLoopPHIs(L, Worklist);
4061 SmallPtrSet<Instruction *, 8> Visited;
4062 while (!Worklist.empty()) {
4063 Instruction *I = Worklist.pop_back_val();
4064 if (!Visited.insert(I)) continue;
4066 ValueExprMapType::iterator It =
4067 ValueExprMap.find(static_cast<Value *>(I));
4068 if (It != ValueExprMap.end()) {
4069 const SCEV *Old = It->second;
4071 // SCEVUnknown for a PHI either means that it has an unrecognized
4072 // structure, or it's a PHI that's in the progress of being computed
4073 // by createNodeForPHI. In the former case, additional loop trip
4074 // count information isn't going to change anything. In the later
4075 // case, createNodeForPHI will perform the necessary updates on its
4076 // own when it gets to that point.
4077 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
4078 forgetMemoizedResults(Old);
4079 ValueExprMap.erase(It);
4081 if (PHINode *PN = dyn_cast<PHINode>(I))
4082 ConstantEvolutionLoopExitValue.erase(PN);
4085 PushDefUseChildren(I, Worklist);
4089 // Re-lookup the insert position, since the call to
4090 // ComputeBackedgeTakenCount above could result in a
4091 // recusive call to getBackedgeTakenInfo (on a different
4092 // loop), which would invalidate the iterator computed
4094 return BackedgeTakenCounts.find(L)->second = Result;
4097 /// forgetLoop - This method should be called by the client when it has
4098 /// changed a loop in a way that may effect ScalarEvolution's ability to
4099 /// compute a trip count, or if the loop is deleted.
4100 void ScalarEvolution::forgetLoop(const Loop *L) {
4101 // Drop any stored trip count value.
4102 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
4103 BackedgeTakenCounts.find(L);
4104 if (BTCPos != BackedgeTakenCounts.end()) {
4105 BTCPos->second.clear();
4106 BackedgeTakenCounts.erase(BTCPos);
4109 // Drop information about expressions based on loop-header PHIs.
4110 SmallVector<Instruction *, 16> Worklist;
4111 PushLoopPHIs(L, Worklist);
4113 SmallPtrSet<Instruction *, 8> Visited;
4114 while (!Worklist.empty()) {
4115 Instruction *I = Worklist.pop_back_val();
4116 if (!Visited.insert(I)) continue;
4118 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
4119 if (It != ValueExprMap.end()) {
4120 forgetMemoizedResults(It->second);
4121 ValueExprMap.erase(It);
4122 if (PHINode *PN = dyn_cast<PHINode>(I))
4123 ConstantEvolutionLoopExitValue.erase(PN);
4126 PushDefUseChildren(I, Worklist);
4129 // Forget all contained loops too, to avoid dangling entries in the
4130 // ValuesAtScopes map.
4131 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
4135 /// forgetValue - This method should be called by the client when it has
4136 /// changed a value in a way that may effect its value, or which may
4137 /// disconnect it from a def-use chain linking it to a loop.
4138 void ScalarEvolution::forgetValue(Value *V) {
4139 Instruction *I = dyn_cast<Instruction>(V);
4142 // Drop information about expressions based on loop-header PHIs.
4143 SmallVector<Instruction *, 16> Worklist;
4144 Worklist.push_back(I);
4146 SmallPtrSet<Instruction *, 8> Visited;
4147 while (!Worklist.empty()) {
4148 I = Worklist.pop_back_val();
4149 if (!Visited.insert(I)) continue;
4151 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
4152 if (It != ValueExprMap.end()) {
4153 forgetMemoizedResults(It->second);
4154 ValueExprMap.erase(It);
4155 if (PHINode *PN = dyn_cast<PHINode>(I))
4156 ConstantEvolutionLoopExitValue.erase(PN);
4159 PushDefUseChildren(I, Worklist);
4163 /// getExact - Get the exact loop backedge taken count considering all loop
4164 /// exits. A computable result can only be return for loops with a single exit.
4165 /// Returning the minimum taken count among all exits is incorrect because one
4166 /// of the loop's exit limit's may have been skipped. HowFarToZero assumes that
4167 /// the limit of each loop test is never skipped. This is a valid assumption as
4168 /// long as the loop exits via that test. For precise results, it is the
4169 /// caller's responsibility to specify the relevant loop exit using
4170 /// getExact(ExitingBlock, SE).
4172 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
4173 // If any exits were not computable, the loop is not computable.
4174 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
4176 // We need exactly one computable exit.
4177 if (!ExitNotTaken.ExitingBlock) return SE->getCouldNotCompute();
4178 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
4180 const SCEV *BECount = 0;
4181 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4182 ENT != 0; ENT = ENT->getNextExit()) {
4184 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
4187 BECount = ENT->ExactNotTaken;
4188 else if (BECount != ENT->ExactNotTaken)
4189 return SE->getCouldNotCompute();
4191 assert(BECount && "Invalid not taken count for loop exit");
4195 /// getExact - Get the exact not taken count for this loop exit.
4197 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
4198 ScalarEvolution *SE) const {
4199 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4200 ENT != 0; ENT = ENT->getNextExit()) {
4202 if (ENT->ExitingBlock == ExitingBlock)
4203 return ENT->ExactNotTaken;
4205 return SE->getCouldNotCompute();
4208 /// getMax - Get the max backedge taken count for the loop.
4210 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
4211 return Max ? Max : SE->getCouldNotCompute();
4214 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
4215 /// computable exit into a persistent ExitNotTakenInfo array.
4216 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
4217 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
4218 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
4221 ExitNotTaken.setIncomplete();
4223 unsigned NumExits = ExitCounts.size();
4224 if (NumExits == 0) return;
4226 ExitNotTaken.ExitingBlock = ExitCounts[0].first;
4227 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
4228 if (NumExits == 1) return;
4230 // Handle the rare case of multiple computable exits.
4231 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
4233 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
4234 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
4235 PrevENT->setNextExit(ENT);
4236 ENT->ExitingBlock = ExitCounts[i].first;
4237 ENT->ExactNotTaken = ExitCounts[i].second;
4241 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
4242 void ScalarEvolution::BackedgeTakenInfo::clear() {
4243 ExitNotTaken.ExitingBlock = 0;
4244 ExitNotTaken.ExactNotTaken = 0;
4245 delete[] ExitNotTaken.getNextExit();
4248 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
4249 /// of the specified loop will execute.
4250 ScalarEvolution::BackedgeTakenInfo
4251 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
4252 SmallVector<BasicBlock *, 8> ExitingBlocks;
4253 L->getExitingBlocks(ExitingBlocks);
4255 // Examine all exits and pick the most conservative values.
4256 const SCEV *MaxBECount = getCouldNotCompute();
4257 bool CouldComputeBECount = true;
4258 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
4259 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
4260 ExitLimit EL = ComputeExitLimit(L, ExitingBlocks[i]);
4261 if (EL.Exact == getCouldNotCompute())
4262 // We couldn't compute an exact value for this exit, so
4263 // we won't be able to compute an exact value for the loop.
4264 CouldComputeBECount = false;
4266 ExitCounts.push_back(std::make_pair(ExitingBlocks[i], EL.Exact));
4268 if (MaxBECount == getCouldNotCompute())
4269 MaxBECount = EL.Max;
4270 else if (EL.Max != getCouldNotCompute()) {
4271 // We cannot take the "min" MaxBECount, because non-unit stride loops may
4272 // skip some loop tests. Taking the max over the exits is sufficiently
4273 // conservative. TODO: We could do better taking into consideration
4274 // that (1) the loop has unit stride (2) the last loop test is
4275 // less-than/greater-than (3) any loop test is less-than/greater-than AND
4276 // falls-through some constant times less then the other tests.
4277 MaxBECount = getUMaxFromMismatchedTypes(MaxBECount, EL.Max);
4281 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
4284 /// ComputeExitLimit - Compute the number of times the backedge of the specified
4285 /// loop will execute if it exits via the specified block.
4286 ScalarEvolution::ExitLimit
4287 ScalarEvolution::ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
4289 // Okay, we've chosen an exiting block. See what condition causes us to
4290 // exit at this block.
4292 // FIXME: we should be able to handle switch instructions (with a single exit)
4293 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
4294 if (ExitBr == 0) return getCouldNotCompute();
4295 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
4297 // At this point, we know we have a conditional branch that determines whether
4298 // the loop is exited. However, we don't know if the branch is executed each
4299 // time through the loop. If not, then the execution count of the branch will
4300 // not be equal to the trip count of the loop.
4302 // Currently we check for this by checking to see if the Exit branch goes to
4303 // the loop header. If so, we know it will always execute the same number of
4304 // times as the loop. We also handle the case where the exit block *is* the
4305 // loop header. This is common for un-rotated loops.
4307 // If both of those tests fail, walk up the unique predecessor chain to the
4308 // header, stopping if there is an edge that doesn't exit the loop. If the
4309 // header is reached, the execution count of the branch will be equal to the
4310 // trip count of the loop.
4312 // More extensive analysis could be done to handle more cases here.
4314 if (ExitBr->getSuccessor(0) != L->getHeader() &&
4315 ExitBr->getSuccessor(1) != L->getHeader() &&
4316 ExitBr->getParent() != L->getHeader()) {
4317 // The simple checks failed, try climbing the unique predecessor chain
4318 // up to the header.
4320 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
4321 BasicBlock *Pred = BB->getUniquePredecessor();
4323 return getCouldNotCompute();
4324 TerminatorInst *PredTerm = Pred->getTerminator();
4325 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
4326 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
4329 // If the predecessor has a successor that isn't BB and isn't
4330 // outside the loop, assume the worst.
4331 if (L->contains(PredSucc))
4332 return getCouldNotCompute();
4334 if (Pred == L->getHeader()) {
4341 return getCouldNotCompute();
4344 // Proceed to the next level to examine the exit condition expression.
4345 return ComputeExitLimitFromCond(L, ExitBr->getCondition(),
4346 ExitBr->getSuccessor(0),
4347 ExitBr->getSuccessor(1));
4350 /// ComputeExitLimitFromCond - Compute the number of times the
4351 /// backedge of the specified loop will execute if its exit condition
4352 /// were a conditional branch of ExitCond, TBB, and FBB.
4353 ScalarEvolution::ExitLimit
4354 ScalarEvolution::ComputeExitLimitFromCond(const Loop *L,
4358 // Check if the controlling expression for this loop is an And or Or.
4359 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
4360 if (BO->getOpcode() == Instruction::And) {
4361 // Recurse on the operands of the and.
4362 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB);
4363 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB);
4364 const SCEV *BECount = getCouldNotCompute();
4365 const SCEV *MaxBECount = getCouldNotCompute();
4366 if (L->contains(TBB)) {
4367 // Both conditions must be true for the loop to continue executing.
4368 // Choose the less conservative count.
4369 if (EL0.Exact == getCouldNotCompute() ||
4370 EL1.Exact == getCouldNotCompute())
4371 BECount = getCouldNotCompute();
4373 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4374 if (EL0.Max == getCouldNotCompute())
4375 MaxBECount = EL1.Max;
4376 else if (EL1.Max == getCouldNotCompute())
4377 MaxBECount = EL0.Max;
4379 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4381 // Both conditions must be true at the same time for the loop to exit.
4382 // For now, be conservative.
4383 assert(L->contains(FBB) && "Loop block has no successor in loop!");
4384 if (EL0.Max == EL1.Max)
4385 MaxBECount = EL0.Max;
4386 if (EL0.Exact == EL1.Exact)
4387 BECount = EL0.Exact;
4390 return ExitLimit(BECount, MaxBECount);
4392 if (BO->getOpcode() == Instruction::Or) {
4393 // Recurse on the operands of the or.
4394 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB);
4395 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB);
4396 const SCEV *BECount = getCouldNotCompute();
4397 const SCEV *MaxBECount = getCouldNotCompute();
4398 if (L->contains(FBB)) {
4399 // Both conditions must be false for the loop to continue executing.
4400 // Choose the less conservative count.
4401 if (EL0.Exact == getCouldNotCompute() ||
4402 EL1.Exact == getCouldNotCompute())
4403 BECount = getCouldNotCompute();
4405 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4406 if (EL0.Max == getCouldNotCompute())
4407 MaxBECount = EL1.Max;
4408 else if (EL1.Max == getCouldNotCompute())
4409 MaxBECount = EL0.Max;
4411 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4413 // Both conditions must be false at the same time for the loop to exit.
4414 // For now, be conservative.
4415 assert(L->contains(TBB) && "Loop block has no successor in loop!");
4416 if (EL0.Max == EL1.Max)
4417 MaxBECount = EL0.Max;
4418 if (EL0.Exact == EL1.Exact)
4419 BECount = EL0.Exact;
4422 return ExitLimit(BECount, MaxBECount);
4426 // With an icmp, it may be feasible to compute an exact backedge-taken count.
4427 // Proceed to the next level to examine the icmp.
4428 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
4429 return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB);
4431 // Check for a constant condition. These are normally stripped out by
4432 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
4433 // preserve the CFG and is temporarily leaving constant conditions
4435 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
4436 if (L->contains(FBB) == !CI->getZExtValue())
4437 // The backedge is always taken.
4438 return getCouldNotCompute();
4440 // The backedge is never taken.
4441 return getConstant(CI->getType(), 0);
4444 // If it's not an integer or pointer comparison then compute it the hard way.
4445 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
4448 /// ComputeExitLimitFromICmp - Compute the number of times the
4449 /// backedge of the specified loop will execute if its exit condition
4450 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4451 ScalarEvolution::ExitLimit
4452 ScalarEvolution::ComputeExitLimitFromICmp(const Loop *L,
4457 // If the condition was exit on true, convert the condition to exit on false
4458 ICmpInst::Predicate Cond;
4459 if (!L->contains(FBB))
4460 Cond = ExitCond->getPredicate();
4462 Cond = ExitCond->getInversePredicate();
4464 // Handle common loops like: for (X = "string"; *X; ++X)
4465 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4466 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4468 ComputeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
4469 if (ItCnt.hasAnyInfo())
4473 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4474 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4476 // Try to evaluate any dependencies out of the loop.
4477 LHS = getSCEVAtScope(LHS, L);
4478 RHS = getSCEVAtScope(RHS, L);
4480 // At this point, we would like to compute how many iterations of the
4481 // loop the predicate will return true for these inputs.
4482 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
4483 // If there is a loop-invariant, force it into the RHS.
4484 std::swap(LHS, RHS);
4485 Cond = ICmpInst::getSwappedPredicate(Cond);
4488 // Simplify the operands before analyzing them.
4489 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4491 // If we have a comparison of a chrec against a constant, try to use value
4492 // ranges to answer this query.
4493 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4494 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4495 if (AddRec->getLoop() == L) {
4496 // Form the constant range.
4497 ConstantRange CompRange(
4498 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4500 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4501 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4505 case ICmpInst::ICMP_NE: { // while (X != Y)
4506 // Convert to: while (X-Y != 0)
4507 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L);
4508 if (EL.hasAnyInfo()) return EL;
4511 case ICmpInst::ICMP_EQ: { // while (X == Y)
4512 // Convert to: while (X-Y == 0)
4513 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
4514 if (EL.hasAnyInfo()) return EL;
4517 case ICmpInst::ICMP_SLT: {
4518 ExitLimit EL = HowManyLessThans(LHS, RHS, L, true);
4519 if (EL.hasAnyInfo()) return EL;
4522 case ICmpInst::ICMP_SGT: {
4523 ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
4524 getNotSCEV(RHS), L, true);
4525 if (EL.hasAnyInfo()) return EL;
4528 case ICmpInst::ICMP_ULT: {
4529 ExitLimit EL = HowManyLessThans(LHS, RHS, L, false);
4530 if (EL.hasAnyInfo()) return EL;
4533 case ICmpInst::ICMP_UGT: {
4534 ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
4535 getNotSCEV(RHS), L, false);
4536 if (EL.hasAnyInfo()) return EL;
4541 dbgs() << "ComputeBackedgeTakenCount ";
4542 if (ExitCond->getOperand(0)->getType()->isUnsigned())
4543 dbgs() << "[unsigned] ";
4544 dbgs() << *LHS << " "
4545 << Instruction::getOpcodeName(Instruction::ICmp)
4546 << " " << *RHS << "\n";
4550 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
4553 static ConstantInt *
4554 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
4555 ScalarEvolution &SE) {
4556 const SCEV *InVal = SE.getConstant(C);
4557 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
4558 assert(isa<SCEVConstant>(Val) &&
4559 "Evaluation of SCEV at constant didn't fold correctly?");
4560 return cast<SCEVConstant>(Val)->getValue();
4563 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
4564 /// and a GEP expression (missing the pointer index) indexing into it, return
4565 /// the addressed element of the initializer or null if the index expression is
4568 GetAddressedElementFromGlobal(GlobalVariable *GV,
4569 const std::vector<ConstantInt*> &Indices) {
4570 Constant *Init = GV->getInitializer();
4571 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
4572 uint64_t Idx = Indices[i]->getZExtValue();
4573 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
4574 assert(Idx < CS->getNumOperands() && "Bad struct index!");
4575 Init = cast<Constant>(CS->getOperand(Idx));
4576 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
4577 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
4578 Init = cast<Constant>(CA->getOperand(Idx));
4579 } else if (isa<ConstantAggregateZero>(Init)) {
4580 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
4581 assert(Idx < STy->getNumElements() && "Bad struct index!");
4582 Init = Constant::getNullValue(STy->getElementType(Idx));
4583 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
4584 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4585 Init = Constant::getNullValue(ATy->getElementType());
4587 llvm_unreachable("Unknown constant aggregate type!");
4591 return 0; // Unknown initializer type
4597 /// ComputeLoadConstantCompareExitLimit - Given an exit condition of
4598 /// 'icmp op load X, cst', try to see if we can compute the backedge
4599 /// execution count.
4600 ScalarEvolution::ExitLimit
4601 ScalarEvolution::ComputeLoadConstantCompareExitLimit(
4605 ICmpInst::Predicate predicate) {
4607 if (LI->isVolatile()) return getCouldNotCompute();
4609 // Check to see if the loaded pointer is a getelementptr of a global.
4610 // TODO: Use SCEV instead of manually grubbing with GEPs.
4611 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4612 if (!GEP) return getCouldNotCompute();
4614 // Make sure that it is really a constant global we are gepping, with an
4615 // initializer, and make sure the first IDX is really 0.
4616 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4617 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4618 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4619 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4620 return getCouldNotCompute();
4622 // Okay, we allow one non-constant index into the GEP instruction.
4624 std::vector<ConstantInt*> Indexes;
4625 unsigned VarIdxNum = 0;
4626 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4627 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4628 Indexes.push_back(CI);
4629 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4630 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4631 VarIdx = GEP->getOperand(i);
4633 Indexes.push_back(0);
4636 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4637 // Check to see if X is a loop variant variable value now.
4638 const SCEV *Idx = getSCEV(VarIdx);
4639 Idx = getSCEVAtScope(Idx, L);
4641 // We can only recognize very limited forms of loop index expressions, in
4642 // particular, only affine AddRec's like {C1,+,C2}.
4643 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4644 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
4645 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4646 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4647 return getCouldNotCompute();
4649 unsigned MaxSteps = MaxBruteForceIterations;
4650 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4651 ConstantInt *ItCst = ConstantInt::get(
4652 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4653 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4655 // Form the GEP offset.
4656 Indexes[VarIdxNum] = Val;
4658 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4659 if (Result == 0) break; // Cannot compute!
4661 // Evaluate the condition for this iteration.
4662 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4663 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4664 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4666 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4667 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4670 ++NumArrayLenItCounts;
4671 return getConstant(ItCst); // Found terminating iteration!
4674 return getCouldNotCompute();
4678 /// CanConstantFold - Return true if we can constant fold an instruction of the
4679 /// specified type, assuming that all operands were constants.
4680 static bool CanConstantFold(const Instruction *I) {
4681 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4682 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
4686 if (const CallInst *CI = dyn_cast<CallInst>(I))
4687 if (const Function *F = CI->getCalledFunction())
4688 return canConstantFoldCallTo(F);
4692 /// Determine whether this instruction can constant evolve within this loop
4693 /// assuming its operands can all constant evolve.
4694 static bool canConstantEvolve(Instruction *I, const Loop *L) {
4695 // An instruction outside of the loop can't be derived from a loop PHI.
4696 if (!L->contains(I)) return false;
4698 if (isa<PHINode>(I)) {
4699 if (L->getHeader() == I->getParent())
4702 // We don't currently keep track of the control flow needed to evaluate
4703 // PHIs, so we cannot handle PHIs inside of loops.
4707 // If we won't be able to constant fold this expression even if the operands
4708 // are constants, bail early.
4709 return CanConstantFold(I);
4712 /// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
4713 /// recursing through each instruction operand until reaching a loop header phi.
4715 getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
4716 DenseMap<Instruction *, PHINode *> &PHIMap) {
4718 // Otherwise, we can evaluate this instruction if all of its operands are
4719 // constant or derived from a PHI node themselves.
4721 for (Instruction::op_iterator OpI = UseInst->op_begin(),
4722 OpE = UseInst->op_end(); OpI != OpE; ++OpI) {
4724 if (isa<Constant>(*OpI)) continue;
4726 Instruction *OpInst = dyn_cast<Instruction>(*OpI);
4727 if (!OpInst || !canConstantEvolve(OpInst, L)) return 0;
4729 PHINode *P = dyn_cast<PHINode>(OpInst);
4731 // If this operand is already visited, reuse the prior result.
4732 // We may have P != PHI if this is the deepest point at which the
4733 // inconsistent paths meet.
4734 P = PHIMap.lookup(OpInst);
4736 // Recurse and memoize the results, whether a phi is found or not.
4737 // This recursive call invalidates pointers into PHIMap.
4738 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap);
4741 if (P == 0) return 0; // Not evolving from PHI
4742 if (PHI && PHI != P) return 0; // Evolving from multiple different PHIs.
4745 // This is a expression evolving from a constant PHI!
4749 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4750 /// in the loop that V is derived from. We allow arbitrary operations along the
4751 /// way, but the operands of an operation must either be constants or a value
4752 /// derived from a constant PHI. If this expression does not fit with these
4753 /// constraints, return null.
4754 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4755 Instruction *I = dyn_cast<Instruction>(V);
4756 if (I == 0 || !canConstantEvolve(I, L)) return 0;
4758 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4762 // Record non-constant instructions contained by the loop.
4763 DenseMap<Instruction *, PHINode *> PHIMap;
4764 return getConstantEvolvingPHIOperands(I, L, PHIMap);
4767 /// EvaluateExpression - Given an expression that passes the
4768 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4769 /// in the loop has the value PHIVal. If we can't fold this expression for some
4770 /// reason, return null.
4771 static Constant *EvaluateExpression(Value *V, const Loop *L,
4772 DenseMap<Instruction *, Constant *> &Vals,
4773 const TargetData *TD) {
4774 // Convenient constant check, but redundant for recursive calls.
4775 if (Constant *C = dyn_cast<Constant>(V)) return C;
4776 Instruction *I = dyn_cast<Instruction>(V);
4779 if (Constant *C = Vals.lookup(I)) return C;
4781 // An instruction inside the loop depends on a value outside the loop that we
4782 // weren't given a mapping for, or a value such as a call inside the loop.
4783 if (!canConstantEvolve(I, L)) return 0;
4785 // An unmapped PHI can be due to a branch or another loop inside this loop,
4786 // or due to this not being the initial iteration through a loop where we
4787 // couldn't compute the evolution of this particular PHI last time.
4788 if (isa<PHINode>(I)) return 0;
4790 std::vector<Constant*> Operands(I->getNumOperands());
4792 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4793 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
4795 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
4796 if (!Operands[i]) return 0;
4799 Constant *C = EvaluateExpression(Operand, L, Vals, TD);
4805 if (CmpInst *CI = dyn_cast<CmpInst>(I))
4806 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4808 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
4809 if (!LI->isVolatile())
4810 return ConstantFoldLoadFromConstPtr(Operands[0], TD);
4812 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, TD);
4815 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4816 /// in the header of its containing loop, we know the loop executes a
4817 /// constant number of times, and the PHI node is just a recurrence
4818 /// involving constants, fold it.
4820 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4823 DenseMap<PHINode*, Constant*>::const_iterator I =
4824 ConstantEvolutionLoopExitValue.find(PN);
4825 if (I != ConstantEvolutionLoopExitValue.end())
4828 if (BEs.ugt(MaxBruteForceIterations))
4829 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4831 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4833 DenseMap<Instruction *, Constant *> CurrentIterVals;
4834 BasicBlock *Header = L->getHeader();
4835 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
4837 // Since the loop is canonicalized, the PHI node must have two entries. One
4838 // entry must be a constant (coming in from outside of the loop), and the
4839 // second must be derived from the same PHI.
4840 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4842 for (BasicBlock::iterator I = Header->begin();
4843 (PHI = dyn_cast<PHINode>(I)); ++I) {
4844 Constant *StartCST =
4845 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
4846 if (StartCST == 0) continue;
4847 CurrentIterVals[PHI] = StartCST;
4849 if (!CurrentIterVals.count(PN))
4852 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4854 // Execute the loop symbolically to determine the exit value.
4855 if (BEs.getActiveBits() >= 32)
4856 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4858 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4859 unsigned IterationNum = 0;
4860 for (; ; ++IterationNum) {
4861 if (IterationNum == NumIterations)
4862 return RetVal = CurrentIterVals[PN]; // Got exit value!
4864 // Compute the value of the PHIs for the next iteration.
4865 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
4866 DenseMap<Instruction *, Constant *> NextIterVals;
4867 Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
4869 return 0; // Couldn't evaluate!
4870 NextIterVals[PN] = NextPHI;
4872 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
4874 // Also evaluate the other PHI nodes. However, we don't get to stop if we
4875 // cease to be able to evaluate one of them or if they stop evolving,
4876 // because that doesn't necessarily prevent us from computing PN.
4877 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
4878 for (DenseMap<Instruction *, Constant *>::const_iterator
4879 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
4880 PHINode *PHI = dyn_cast<PHINode>(I->first);
4881 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
4882 PHIsToCompute.push_back(std::make_pair(PHI, I->second));
4884 // We use two distinct loops because EvaluateExpression may invalidate any
4885 // iterators into CurrentIterVals.
4886 for (SmallVectorImpl<std::pair<PHINode *, Constant*> >::const_iterator
4887 I = PHIsToCompute.begin(), E = PHIsToCompute.end(); I != E; ++I) {
4888 PHINode *PHI = I->first;
4889 Constant *&NextPHI = NextIterVals[PHI];
4890 if (!NextPHI) { // Not already computed.
4891 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
4892 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
4894 if (NextPHI != I->second)
4895 StoppedEvolving = false;
4898 // If all entries in CurrentIterVals == NextIterVals then we can stop
4899 // iterating, the loop can't continue to change.
4900 if (StoppedEvolving)
4901 return RetVal = CurrentIterVals[PN];
4903 CurrentIterVals.swap(NextIterVals);
4907 /// ComputeExitCountExhaustively - If the loop is known to execute a
4908 /// constant number of times (the condition evolves only from constants),
4909 /// try to evaluate a few iterations of the loop until we get the exit
4910 /// condition gets a value of ExitWhen (true or false). If we cannot
4911 /// evaluate the trip count of the loop, return getCouldNotCompute().
4912 const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
4915 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4916 if (PN == 0) return getCouldNotCompute();
4918 // If the loop is canonicalized, the PHI will have exactly two entries.
4919 // That's the only form we support here.
4920 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4922 DenseMap<Instruction *, Constant *> CurrentIterVals;
4923 BasicBlock *Header = L->getHeader();
4924 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
4926 // One entry must be a constant (coming in from outside of the loop), and the
4927 // second must be derived from the same PHI.
4928 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4930 for (BasicBlock::iterator I = Header->begin();
4931 (PHI = dyn_cast<PHINode>(I)); ++I) {
4932 Constant *StartCST =
4933 dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
4934 if (StartCST == 0) continue;
4935 CurrentIterVals[PHI] = StartCST;
4937 if (!CurrentIterVals.count(PN))
4938 return getCouldNotCompute();
4940 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4941 // the loop symbolically to determine when the condition gets a value of
4944 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4945 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
4946 ConstantInt *CondVal =
4947 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L,
4948 CurrentIterVals, TD));
4950 // Couldn't symbolically evaluate.
4951 if (!CondVal) return getCouldNotCompute();
4953 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4954 ++NumBruteForceTripCountsComputed;
4955 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4958 // Update all the PHI nodes for the next iteration.
4959 DenseMap<Instruction *, Constant *> NextIterVals;
4961 // Create a list of which PHIs we need to compute. We want to do this before
4962 // calling EvaluateExpression on them because that may invalidate iterators
4963 // into CurrentIterVals.
4964 SmallVector<PHINode *, 8> PHIsToCompute;
4965 for (DenseMap<Instruction *, Constant *>::const_iterator
4966 I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
4967 PHINode *PHI = dyn_cast<PHINode>(I->first);
4968 if (!PHI || PHI->getParent() != Header) continue;
4969 PHIsToCompute.push_back(PHI);
4971 for (SmallVectorImpl<PHINode *>::const_iterator I = PHIsToCompute.begin(),
4972 E = PHIsToCompute.end(); I != E; ++I) {
4974 Constant *&NextPHI = NextIterVals[PHI];
4975 if (NextPHI) continue; // Already computed!
4977 Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
4978 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
4980 CurrentIterVals.swap(NextIterVals);
4983 // Too many iterations were needed to evaluate.
4984 return getCouldNotCompute();
4987 /// getSCEVAtScope - Return a SCEV expression for the specified value
4988 /// at the specified scope in the program. The L value specifies a loop
4989 /// nest to evaluate the expression at, where null is the top-level or a
4990 /// specified loop is immediately inside of the loop.
4992 /// This method can be used to compute the exit value for a variable defined
4993 /// in a loop by querying what the value will hold in the parent loop.
4995 /// In the case that a relevant loop exit value cannot be computed, the
4996 /// original value V is returned.
4997 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4998 // Check to see if we've folded this expression at this loop before.
4999 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
5000 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
5001 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
5003 return Pair.first->second ? Pair.first->second : V;
5005 // Otherwise compute it.
5006 const SCEV *C = computeSCEVAtScope(V, L);
5007 ValuesAtScopes[V][L] = C;
5011 /// This builds up a Constant using the ConstantExpr interface. That way, we
5012 /// will return Constants for objects which aren't represented by a
5013 /// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
5014 /// Returns NULL if the SCEV isn't representable as a Constant.
5015 static Constant *BuildConstantFromSCEV(const SCEV *V) {
5016 switch (V->getSCEVType()) {
5017 default: // TODO: smax, umax.
5018 case scCouldNotCompute:
5022 return cast<SCEVConstant>(V)->getValue();
5024 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
5025 case scSignExtend: {
5026 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
5027 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
5028 return ConstantExpr::getSExt(CastOp, SS->getType());
5031 case scZeroExtend: {
5032 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
5033 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
5034 return ConstantExpr::getZExt(CastOp, SZ->getType());
5038 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
5039 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
5040 return ConstantExpr::getTrunc(CastOp, ST->getType());
5044 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
5045 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
5046 if (C->getType()->isPointerTy())
5047 C = ConstantExpr::getBitCast(C, Type::getInt8PtrTy(C->getContext()));
5048 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
5049 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
5053 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
5055 // The offsets have been converted to bytes. We can add bytes to an
5056 // i8* by GEP with the byte count in the first index.
5057 C = ConstantExpr::getBitCast(C,Type::getInt8PtrTy(C->getContext()));
5060 // Don't bother trying to sum two pointers. We probably can't
5061 // statically compute a load that results from it anyway.
5062 if (C2->getType()->isPointerTy())
5065 if (C->getType()->isPointerTy()) {
5066 if (cast<PointerType>(C->getType())->getElementType()->isStructTy())
5067 C2 = ConstantExpr::getIntegerCast(
5068 C2, Type::getInt32Ty(C->getContext()), true);
5069 C = ConstantExpr::getGetElementPtr(C, C2);
5071 C = ConstantExpr::getAdd(C, C2);
5078 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
5079 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
5080 // Don't bother with pointers at all.
5081 if (C->getType()->isPointerTy()) return 0;
5082 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
5083 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
5084 if (!C2 || C2->getType()->isPointerTy()) return 0;
5085 C = ConstantExpr::getMul(C, C2);
5092 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
5093 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
5094 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
5095 if (LHS->getType() == RHS->getType())
5096 return ConstantExpr::getUDiv(LHS, RHS);
5103 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
5104 if (isa<SCEVConstant>(V)) return V;
5106 // If this instruction is evolved from a constant-evolving PHI, compute the
5107 // exit value from the loop without using SCEVs.
5108 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
5109 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
5110 const Loop *LI = (*this->LI)[I->getParent()];
5111 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
5112 if (PHINode *PN = dyn_cast<PHINode>(I))
5113 if (PN->getParent() == LI->getHeader()) {
5114 // Okay, there is no closed form solution for the PHI node. Check
5115 // to see if the loop that contains it has a known backedge-taken
5116 // count. If so, we may be able to force computation of the exit
5118 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
5119 if (const SCEVConstant *BTCC =
5120 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
5121 // Okay, we know how many times the containing loop executes. If
5122 // this is a constant evolving PHI node, get the final value at
5123 // the specified iteration number.
5124 Constant *RV = getConstantEvolutionLoopExitValue(PN,
5125 BTCC->getValue()->getValue(),
5127 if (RV) return getSCEV(RV);
5131 // Okay, this is an expression that we cannot symbolically evaluate
5132 // into a SCEV. Check to see if it's possible to symbolically evaluate
5133 // the arguments into constants, and if so, try to constant propagate the
5134 // result. This is particularly useful for computing loop exit values.
5135 if (CanConstantFold(I)) {
5136 SmallVector<Constant *, 4> Operands;
5137 bool MadeImprovement = false;
5138 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
5139 Value *Op = I->getOperand(i);
5140 if (Constant *C = dyn_cast<Constant>(Op)) {
5141 Operands.push_back(C);
5145 // If any of the operands is non-constant and if they are
5146 // non-integer and non-pointer, don't even try to analyze them
5147 // with scev techniques.
5148 if (!isSCEVable(Op->getType()))
5151 const SCEV *OrigV = getSCEV(Op);
5152 const SCEV *OpV = getSCEVAtScope(OrigV, L);
5153 MadeImprovement |= OrigV != OpV;
5155 Constant *C = BuildConstantFromSCEV(OpV);
5157 if (C->getType() != Op->getType())
5158 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5162 Operands.push_back(C);
5165 // Check to see if getSCEVAtScope actually made an improvement.
5166 if (MadeImprovement) {
5168 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
5169 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
5170 Operands[0], Operands[1], TD);
5171 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
5172 if (!LI->isVolatile())
5173 C = ConstantFoldLoadFromConstPtr(Operands[0], TD);
5175 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
5183 // This is some other type of SCEVUnknown, just return it.
5187 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
5188 // Avoid performing the look-up in the common case where the specified
5189 // expression has no loop-variant portions.
5190 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
5191 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5192 if (OpAtScope != Comm->getOperand(i)) {
5193 // Okay, at least one of these operands is loop variant but might be
5194 // foldable. Build a new instance of the folded commutative expression.
5195 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
5196 Comm->op_begin()+i);
5197 NewOps.push_back(OpAtScope);
5199 for (++i; i != e; ++i) {
5200 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
5201 NewOps.push_back(OpAtScope);
5203 if (isa<SCEVAddExpr>(Comm))
5204 return getAddExpr(NewOps);
5205 if (isa<SCEVMulExpr>(Comm))
5206 return getMulExpr(NewOps);
5207 if (isa<SCEVSMaxExpr>(Comm))
5208 return getSMaxExpr(NewOps);
5209 if (isa<SCEVUMaxExpr>(Comm))
5210 return getUMaxExpr(NewOps);
5211 llvm_unreachable("Unknown commutative SCEV type!");
5214 // If we got here, all operands are loop invariant.
5218 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
5219 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
5220 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
5221 if (LHS == Div->getLHS() && RHS == Div->getRHS())
5222 return Div; // must be loop invariant
5223 return getUDivExpr(LHS, RHS);
5226 // If this is a loop recurrence for a loop that does not contain L, then we
5227 // are dealing with the final value computed by the loop.
5228 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
5229 // First, attempt to evaluate each operand.
5230 // Avoid performing the look-up in the common case where the specified
5231 // expression has no loop-variant portions.
5232 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
5233 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
5234 if (OpAtScope == AddRec->getOperand(i))
5237 // Okay, at least one of these operands is loop variant but might be
5238 // foldable. Build a new instance of the folded commutative expression.
5239 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
5240 AddRec->op_begin()+i);
5241 NewOps.push_back(OpAtScope);
5242 for (++i; i != e; ++i)
5243 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
5245 const SCEV *FoldedRec =
5246 getAddRecExpr(NewOps, AddRec->getLoop(),
5247 AddRec->getNoWrapFlags(SCEV::FlagNW));
5248 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
5249 // The addrec may be folded to a nonrecurrence, for example, if the
5250 // induction variable is multiplied by zero after constant folding. Go
5251 // ahead and return the folded value.
5257 // If the scope is outside the addrec's loop, evaluate it by using the
5258 // loop exit value of the addrec.
5259 if (!AddRec->getLoop()->contains(L)) {
5260 // To evaluate this recurrence, we need to know how many times the AddRec
5261 // loop iterates. Compute this now.
5262 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
5263 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
5265 // Then, evaluate the AddRec.
5266 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
5272 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
5273 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5274 if (Op == Cast->getOperand())
5275 return Cast; // must be loop invariant
5276 return getZeroExtendExpr(Op, Cast->getType());
5279 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
5280 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5281 if (Op == Cast->getOperand())
5282 return Cast; // must be loop invariant
5283 return getSignExtendExpr(Op, Cast->getType());
5286 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
5287 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
5288 if (Op == Cast->getOperand())
5289 return Cast; // must be loop invariant
5290 return getTruncateExpr(Op, Cast->getType());
5293 llvm_unreachable("Unknown SCEV type!");
5297 /// getSCEVAtScope - This is a convenience function which does
5298 /// getSCEVAtScope(getSCEV(V), L).
5299 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
5300 return getSCEVAtScope(getSCEV(V), L);
5303 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
5304 /// following equation:
5306 /// A * X = B (mod N)
5308 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
5309 /// A and B isn't important.
5311 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
5312 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
5313 ScalarEvolution &SE) {
5314 uint32_t BW = A.getBitWidth();
5315 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
5316 assert(A != 0 && "A must be non-zero.");
5320 // The gcd of A and N may have only one prime factor: 2. The number of
5321 // trailing zeros in A is its multiplicity
5322 uint32_t Mult2 = A.countTrailingZeros();
5325 // 2. Check if B is divisible by D.
5327 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
5328 // is not less than multiplicity of this prime factor for D.
5329 if (B.countTrailingZeros() < Mult2)
5330 return SE.getCouldNotCompute();
5332 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
5335 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
5336 // bit width during computations.
5337 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
5338 APInt Mod(BW + 1, 0);
5339 Mod.setBit(BW - Mult2); // Mod = N / D
5340 APInt I = AD.multiplicativeInverse(Mod);
5342 // 4. Compute the minimum unsigned root of the equation:
5343 // I * (B / D) mod (N / D)
5344 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
5346 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
5348 return SE.getConstant(Result.trunc(BW));
5351 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
5352 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
5353 /// might be the same) or two SCEVCouldNotCompute objects.
5355 static std::pair<const SCEV *,const SCEV *>
5356 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
5357 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
5358 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
5359 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
5360 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
5362 // We currently can only solve this if the coefficients are constants.
5363 if (!LC || !MC || !NC) {
5364 const SCEV *CNC = SE.getCouldNotCompute();
5365 return std::make_pair(CNC, CNC);
5368 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
5369 const APInt &L = LC->getValue()->getValue();
5370 const APInt &M = MC->getValue()->getValue();
5371 const APInt &N = NC->getValue()->getValue();
5372 APInt Two(BitWidth, 2);
5373 APInt Four(BitWidth, 4);
5376 using namespace APIntOps;
5378 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
5379 // The B coefficient is M-N/2
5383 // The A coefficient is N/2
5384 APInt A(N.sdiv(Two));
5386 // Compute the B^2-4ac term.
5389 SqrtTerm -= Four * (A * C);
5391 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
5392 // integer value or else APInt::sqrt() will assert.
5393 APInt SqrtVal(SqrtTerm.sqrt());
5395 // Compute the two solutions for the quadratic formula.
5396 // The divisions must be performed as signed divisions.
5399 if (TwoA.isMinValue()) {
5400 const SCEV *CNC = SE.getCouldNotCompute();
5401 return std::make_pair(CNC, CNC);
5404 LLVMContext &Context = SE.getContext();
5406 ConstantInt *Solution1 =
5407 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
5408 ConstantInt *Solution2 =
5409 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
5411 return std::make_pair(SE.getConstant(Solution1),
5412 SE.getConstant(Solution2));
5413 } // end APIntOps namespace
5416 /// HowFarToZero - Return the number of times a backedge comparing the specified
5417 /// value to zero will execute. If not computable, return CouldNotCompute.
5419 /// This is only used for loops with a "x != y" exit test. The exit condition is
5420 /// now expressed as a single expression, V = x-y. So the exit test is
5421 /// effectively V != 0. We know and take advantage of the fact that this
5422 /// expression only being used in a comparison by zero context.
5423 ScalarEvolution::ExitLimit
5424 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
5425 // If the value is a constant
5426 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
5427 // If the value is already zero, the branch will execute zero times.
5428 if (C->getValue()->isZero()) return C;
5429 return getCouldNotCompute(); // Otherwise it will loop infinitely.
5432 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
5433 if (!AddRec || AddRec->getLoop() != L)
5434 return getCouldNotCompute();
5436 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
5437 // the quadratic equation to solve it.
5438 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
5439 std::pair<const SCEV *,const SCEV *> Roots =
5440 SolveQuadraticEquation(AddRec, *this);
5441 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5442 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5445 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
5446 << " sol#2: " << *R2 << "\n";
5448 // Pick the smallest positive root value.
5449 if (ConstantInt *CB =
5450 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
5453 if (CB->getZExtValue() == false)
5454 std::swap(R1, R2); // R1 is the minimum root now.
5456 // We can only use this value if the chrec ends up with an exact zero
5457 // value at this index. When solving for "X*X != 5", for example, we
5458 // should not accept a root of 2.
5459 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
5461 return R1; // We found a quadratic root!
5464 return getCouldNotCompute();
5467 // Otherwise we can only handle this if it is affine.
5468 if (!AddRec->isAffine())
5469 return getCouldNotCompute();
5471 // If this is an affine expression, the execution count of this branch is
5472 // the minimum unsigned root of the following equation:
5474 // Start + Step*N = 0 (mod 2^BW)
5478 // Step*N = -Start (mod 2^BW)
5480 // where BW is the common bit width of Start and Step.
5482 // Get the initial value for the loop.
5483 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
5484 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
5486 // For now we handle only constant steps.
5488 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
5489 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
5490 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
5491 // We have not yet seen any such cases.
5492 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
5494 return getCouldNotCompute();
5496 // For positive steps (counting up until unsigned overflow):
5497 // N = -Start/Step (as unsigned)
5498 // For negative steps (counting down to zero):
5500 // First compute the unsigned distance from zero in the direction of Step.
5501 bool CountDown = StepC->getValue()->getValue().isNegative();
5502 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
5504 // Handle unitary steps, which cannot wraparound.
5505 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
5506 // N = Distance (as unsigned)
5507 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
5508 ConstantRange CR = getUnsignedRange(Start);
5509 const SCEV *MaxBECount;
5510 if (!CountDown && CR.getUnsignedMin().isMinValue())
5511 // When counting up, the worst starting value is 1, not 0.
5512 MaxBECount = CR.getUnsignedMax().isMinValue()
5513 ? getConstant(APInt::getMinValue(CR.getBitWidth()))
5514 : getConstant(APInt::getMaxValue(CR.getBitWidth()));
5516 MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
5517 : -CR.getUnsignedMin());
5518 return ExitLimit(Distance, MaxBECount);
5521 // If the recurrence is known not to wraparound, unsigned divide computes the
5522 // back edge count. We know that the value will either become zero (and thus
5523 // the loop terminates), that the loop will terminate through some other exit
5524 // condition first, or that the loop has undefined behavior. This means
5525 // we can't "miss" the exit value, even with nonunit stride.
5527 // FIXME: Prove that loops always exhibits *acceptable* undefined
5528 // behavior. Loops must exhibit defined behavior until a wrapped value is
5529 // actually used. So the trip count computed by udiv could be smaller than the
5530 // number of well-defined iterations.
5531 if (AddRec->getNoWrapFlags(SCEV::FlagNW)) {
5532 // FIXME: We really want an "isexact" bit for udiv.
5533 return getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
5535 // Then, try to solve the above equation provided that Start is constant.
5536 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
5537 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
5538 -StartC->getValue()->getValue(),
5540 return getCouldNotCompute();
5543 /// HowFarToNonZero - Return the number of times a backedge checking the
5544 /// specified value for nonzero will execute. If not computable, return
5546 ScalarEvolution::ExitLimit
5547 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
5548 // Loops that look like: while (X == 0) are very strange indeed. We don't
5549 // handle them yet except for the trivial case. This could be expanded in the
5550 // future as needed.
5552 // If the value is a constant, check to see if it is known to be non-zero
5553 // already. If so, the backedge will execute zero times.
5554 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
5555 if (!C->getValue()->isNullValue())
5556 return getConstant(C->getType(), 0);
5557 return getCouldNotCompute(); // Otherwise it will loop infinitely.
5560 // We could implement others, but I really doubt anyone writes loops like
5561 // this, and if they did, they would already be constant folded.
5562 return getCouldNotCompute();
5565 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
5566 /// (which may not be an immediate predecessor) which has exactly one
5567 /// successor from which BB is reachable, or null if no such block is
5570 std::pair<BasicBlock *, BasicBlock *>
5571 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
5572 // If the block has a unique predecessor, then there is no path from the
5573 // predecessor to the block that does not go through the direct edge
5574 // from the predecessor to the block.
5575 if (BasicBlock *Pred = BB->getSinglePredecessor())
5576 return std::make_pair(Pred, BB);
5578 // A loop's header is defined to be a block that dominates the loop.
5579 // If the header has a unique predecessor outside the loop, it must be
5580 // a block that has exactly one successor that can reach the loop.
5581 if (Loop *L = LI->getLoopFor(BB))
5582 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
5584 return std::pair<BasicBlock *, BasicBlock *>();
5587 /// HasSameValue - SCEV structural equivalence is usually sufficient for
5588 /// testing whether two expressions are equal, however for the purposes of
5589 /// looking for a condition guarding a loop, it can be useful to be a little
5590 /// more general, since a front-end may have replicated the controlling
5593 static bool HasSameValue(const SCEV *A, const SCEV *B) {
5594 // Quick check to see if they are the same SCEV.
5595 if (A == B) return true;
5597 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
5598 // two different instructions with the same value. Check for this case.
5599 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
5600 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
5601 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
5602 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
5603 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
5606 // Otherwise assume they may have a different value.
5610 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
5611 /// predicate Pred. Return true iff any changes were made.
5613 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
5614 const SCEV *&LHS, const SCEV *&RHS) {
5615 bool Changed = false;
5617 // Canonicalize a constant to the right side.
5618 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
5619 // Check for both operands constant.
5620 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
5621 if (ConstantExpr::getICmp(Pred,
5623 RHSC->getValue())->isNullValue())
5624 goto trivially_false;
5626 goto trivially_true;
5628 // Otherwise swap the operands to put the constant on the right.
5629 std::swap(LHS, RHS);
5630 Pred = ICmpInst::getSwappedPredicate(Pred);
5634 // If we're comparing an addrec with a value which is loop-invariant in the
5635 // addrec's loop, put the addrec on the left. Also make a dominance check,
5636 // as both operands could be addrecs loop-invariant in each other's loop.
5637 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
5638 const Loop *L = AR->getLoop();
5639 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
5640 std::swap(LHS, RHS);
5641 Pred = ICmpInst::getSwappedPredicate(Pred);
5646 // If there's a constant operand, canonicalize comparisons with boundary
5647 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
5648 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
5649 const APInt &RA = RC->getValue()->getValue();
5651 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5652 case ICmpInst::ICMP_EQ:
5653 case ICmpInst::ICMP_NE:
5655 case ICmpInst::ICMP_UGE:
5656 if ((RA - 1).isMinValue()) {
5657 Pred = ICmpInst::ICMP_NE;
5658 RHS = getConstant(RA - 1);
5662 if (RA.isMaxValue()) {
5663 Pred = ICmpInst::ICMP_EQ;
5667 if (RA.isMinValue()) goto trivially_true;
5669 Pred = ICmpInst::ICMP_UGT;
5670 RHS = getConstant(RA - 1);
5673 case ICmpInst::ICMP_ULE:
5674 if ((RA + 1).isMaxValue()) {
5675 Pred = ICmpInst::ICMP_NE;
5676 RHS = getConstant(RA + 1);
5680 if (RA.isMinValue()) {
5681 Pred = ICmpInst::ICMP_EQ;
5685 if (RA.isMaxValue()) goto trivially_true;
5687 Pred = ICmpInst::ICMP_ULT;
5688 RHS = getConstant(RA + 1);
5691 case ICmpInst::ICMP_SGE:
5692 if ((RA - 1).isMinSignedValue()) {
5693 Pred = ICmpInst::ICMP_NE;
5694 RHS = getConstant(RA - 1);
5698 if (RA.isMaxSignedValue()) {
5699 Pred = ICmpInst::ICMP_EQ;
5703 if (RA.isMinSignedValue()) goto trivially_true;
5705 Pred = ICmpInst::ICMP_SGT;
5706 RHS = getConstant(RA - 1);
5709 case ICmpInst::ICMP_SLE:
5710 if ((RA + 1).isMaxSignedValue()) {
5711 Pred = ICmpInst::ICMP_NE;
5712 RHS = getConstant(RA + 1);
5716 if (RA.isMinSignedValue()) {
5717 Pred = ICmpInst::ICMP_EQ;
5721 if (RA.isMaxSignedValue()) goto trivially_true;
5723 Pred = ICmpInst::ICMP_SLT;
5724 RHS = getConstant(RA + 1);
5727 case ICmpInst::ICMP_UGT:
5728 if (RA.isMinValue()) {
5729 Pred = ICmpInst::ICMP_NE;
5733 if ((RA + 1).isMaxValue()) {
5734 Pred = ICmpInst::ICMP_EQ;
5735 RHS = getConstant(RA + 1);
5739 if (RA.isMaxValue()) goto trivially_false;
5741 case ICmpInst::ICMP_ULT:
5742 if (RA.isMaxValue()) {
5743 Pred = ICmpInst::ICMP_NE;
5747 if ((RA - 1).isMinValue()) {
5748 Pred = ICmpInst::ICMP_EQ;
5749 RHS = getConstant(RA - 1);
5753 if (RA.isMinValue()) goto trivially_false;
5755 case ICmpInst::ICMP_SGT:
5756 if (RA.isMinSignedValue()) {
5757 Pred = ICmpInst::ICMP_NE;
5761 if ((RA + 1).isMaxSignedValue()) {
5762 Pred = ICmpInst::ICMP_EQ;
5763 RHS = getConstant(RA + 1);
5767 if (RA.isMaxSignedValue()) goto trivially_false;
5769 case ICmpInst::ICMP_SLT:
5770 if (RA.isMaxSignedValue()) {
5771 Pred = ICmpInst::ICMP_NE;
5775 if ((RA - 1).isMinSignedValue()) {
5776 Pred = ICmpInst::ICMP_EQ;
5777 RHS = getConstant(RA - 1);
5781 if (RA.isMinSignedValue()) goto trivially_false;
5786 // Check for obvious equality.
5787 if (HasSameValue(LHS, RHS)) {
5788 if (ICmpInst::isTrueWhenEqual(Pred))
5789 goto trivially_true;
5790 if (ICmpInst::isFalseWhenEqual(Pred))
5791 goto trivially_false;
5794 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
5795 // adding or subtracting 1 from one of the operands.
5797 case ICmpInst::ICMP_SLE:
5798 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
5799 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5801 Pred = ICmpInst::ICMP_SLT;
5803 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
5804 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5806 Pred = ICmpInst::ICMP_SLT;
5810 case ICmpInst::ICMP_SGE:
5811 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
5812 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5814 Pred = ICmpInst::ICMP_SGT;
5816 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
5817 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5819 Pred = ICmpInst::ICMP_SGT;
5823 case ICmpInst::ICMP_ULE:
5824 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
5825 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5827 Pred = ICmpInst::ICMP_ULT;
5829 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
5830 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5832 Pred = ICmpInst::ICMP_ULT;
5836 case ICmpInst::ICMP_UGE:
5837 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
5838 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5840 Pred = ICmpInst::ICMP_UGT;
5842 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
5843 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5845 Pred = ICmpInst::ICMP_UGT;
5853 // TODO: More simplifications are possible here.
5859 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5860 Pred = ICmpInst::ICMP_EQ;
5865 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5866 Pred = ICmpInst::ICMP_NE;
5870 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
5871 return getSignedRange(S).getSignedMax().isNegative();
5874 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5875 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5878 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5879 return !getSignedRange(S).getSignedMin().isNegative();
5882 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5883 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5886 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5887 return isKnownNegative(S) || isKnownPositive(S);
5890 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5891 const SCEV *LHS, const SCEV *RHS) {
5892 // Canonicalize the inputs first.
5893 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5895 // If LHS or RHS is an addrec, check to see if the condition is true in
5896 // every iteration of the loop.
5897 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5898 if (isLoopEntryGuardedByCond(
5899 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5900 isLoopBackedgeGuardedByCond(
5901 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5903 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5904 if (isLoopEntryGuardedByCond(
5905 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5906 isLoopBackedgeGuardedByCond(
5907 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5910 // Otherwise see what can be done with known constant ranges.
5911 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5915 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5916 const SCEV *LHS, const SCEV *RHS) {
5917 if (HasSameValue(LHS, RHS))
5918 return ICmpInst::isTrueWhenEqual(Pred);
5920 // This code is split out from isKnownPredicate because it is called from
5921 // within isLoopEntryGuardedByCond.
5924 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5926 case ICmpInst::ICMP_SGT:
5927 Pred = ICmpInst::ICMP_SLT;
5928 std::swap(LHS, RHS);
5929 case ICmpInst::ICMP_SLT: {
5930 ConstantRange LHSRange = getSignedRange(LHS);
5931 ConstantRange RHSRange = getSignedRange(RHS);
5932 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5934 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5938 case ICmpInst::ICMP_SGE:
5939 Pred = ICmpInst::ICMP_SLE;
5940 std::swap(LHS, RHS);
5941 case ICmpInst::ICMP_SLE: {
5942 ConstantRange LHSRange = getSignedRange(LHS);
5943 ConstantRange RHSRange = getSignedRange(RHS);
5944 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5946 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5950 case ICmpInst::ICMP_UGT:
5951 Pred = ICmpInst::ICMP_ULT;
5952 std::swap(LHS, RHS);
5953 case ICmpInst::ICMP_ULT: {
5954 ConstantRange LHSRange = getUnsignedRange(LHS);
5955 ConstantRange RHSRange = getUnsignedRange(RHS);
5956 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5958 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5962 case ICmpInst::ICMP_UGE:
5963 Pred = ICmpInst::ICMP_ULE;
5964 std::swap(LHS, RHS);
5965 case ICmpInst::ICMP_ULE: {
5966 ConstantRange LHSRange = getUnsignedRange(LHS);
5967 ConstantRange RHSRange = getUnsignedRange(RHS);
5968 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5970 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5974 case ICmpInst::ICMP_NE: {
5975 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5977 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5980 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5981 if (isKnownNonZero(Diff))
5985 case ICmpInst::ICMP_EQ:
5986 // The check at the top of the function catches the case where
5987 // the values are known to be equal.
5993 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5994 /// protected by a conditional between LHS and RHS. This is used to
5995 /// to eliminate casts.
5997 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5998 ICmpInst::Predicate Pred,
5999 const SCEV *LHS, const SCEV *RHS) {
6000 // Interpret a null as meaning no loop, where there is obviously no guard
6001 // (interprocedural conditions notwithstanding).
6002 if (!L) return true;
6004 BasicBlock *Latch = L->getLoopLatch();
6008 BranchInst *LoopContinuePredicate =
6009 dyn_cast<BranchInst>(Latch->getTerminator());
6010 if (!LoopContinuePredicate ||
6011 LoopContinuePredicate->isUnconditional())
6014 return isImpliedCond(Pred, LHS, RHS,
6015 LoopContinuePredicate->getCondition(),
6016 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
6019 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
6020 /// by a conditional between LHS and RHS. This is used to help avoid max
6021 /// expressions in loop trip counts, and to eliminate casts.
6023 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
6024 ICmpInst::Predicate Pred,
6025 const SCEV *LHS, const SCEV *RHS) {
6026 // Interpret a null as meaning no loop, where there is obviously no guard
6027 // (interprocedural conditions notwithstanding).
6028 if (!L) return false;
6030 // Starting at the loop predecessor, climb up the predecessor chain, as long
6031 // as there are predecessors that can be found that have unique successors
6032 // leading to the original header.
6033 for (std::pair<BasicBlock *, BasicBlock *>
6034 Pair(L->getLoopPredecessor(), L->getHeader());
6036 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
6038 BranchInst *LoopEntryPredicate =
6039 dyn_cast<BranchInst>(Pair.first->getTerminator());
6040 if (!LoopEntryPredicate ||
6041 LoopEntryPredicate->isUnconditional())
6044 if (isImpliedCond(Pred, LHS, RHS,
6045 LoopEntryPredicate->getCondition(),
6046 LoopEntryPredicate->getSuccessor(0) != Pair.second))
6053 /// isImpliedCond - Test whether the condition described by Pred, LHS,
6054 /// and RHS is true whenever the given Cond value evaluates to true.
6055 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
6056 const SCEV *LHS, const SCEV *RHS,
6057 Value *FoundCondValue,
6059 // Recursively handle And and Or conditions.
6060 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
6061 if (BO->getOpcode() == Instruction::And) {
6063 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6064 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6065 } else if (BO->getOpcode() == Instruction::Or) {
6067 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
6068 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
6072 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
6073 if (!ICI) return false;
6075 // Bail if the ICmp's operands' types are wider than the needed type
6076 // before attempting to call getSCEV on them. This avoids infinite
6077 // recursion, since the analysis of widening casts can require loop
6078 // exit condition information for overflow checking, which would
6080 if (getTypeSizeInBits(LHS->getType()) <
6081 getTypeSizeInBits(ICI->getOperand(0)->getType()))
6084 // Now that we found a conditional branch that dominates the loop, check to
6085 // see if it is the comparison we are looking for.
6086 ICmpInst::Predicate FoundPred;
6088 FoundPred = ICI->getInversePredicate();
6090 FoundPred = ICI->getPredicate();
6092 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
6093 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
6095 // Balance the types. The case where FoundLHS' type is wider than
6096 // LHS' type is checked for above.
6097 if (getTypeSizeInBits(LHS->getType()) >
6098 getTypeSizeInBits(FoundLHS->getType())) {
6099 if (CmpInst::isSigned(Pred)) {
6100 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
6101 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
6103 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
6104 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
6108 // Canonicalize the query to match the way instcombine will have
6109 // canonicalized the comparison.
6110 if (SimplifyICmpOperands(Pred, LHS, RHS))
6112 return CmpInst::isTrueWhenEqual(Pred);
6113 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
6114 if (FoundLHS == FoundRHS)
6115 return CmpInst::isFalseWhenEqual(Pred);
6117 // Check to see if we can make the LHS or RHS match.
6118 if (LHS == FoundRHS || RHS == FoundLHS) {
6119 if (isa<SCEVConstant>(RHS)) {
6120 std::swap(FoundLHS, FoundRHS);
6121 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
6123 std::swap(LHS, RHS);
6124 Pred = ICmpInst::getSwappedPredicate(Pred);
6128 // Check whether the found predicate is the same as the desired predicate.
6129 if (FoundPred == Pred)
6130 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
6132 // Check whether swapping the found predicate makes it the same as the
6133 // desired predicate.
6134 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
6135 if (isa<SCEVConstant>(RHS))
6136 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
6138 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
6139 RHS, LHS, FoundLHS, FoundRHS);
6142 // Check whether the actual condition is beyond sufficient.
6143 if (FoundPred == ICmpInst::ICMP_EQ)
6144 if (ICmpInst::isTrueWhenEqual(Pred))
6145 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
6147 if (Pred == ICmpInst::ICMP_NE)
6148 if (!ICmpInst::isTrueWhenEqual(FoundPred))
6149 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
6152 // Otherwise assume the worst.
6156 /// isImpliedCondOperands - Test whether the condition described by Pred,
6157 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
6158 /// and FoundRHS is true.
6159 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
6160 const SCEV *LHS, const SCEV *RHS,
6161 const SCEV *FoundLHS,
6162 const SCEV *FoundRHS) {
6163 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
6164 FoundLHS, FoundRHS) ||
6165 // ~x < ~y --> x > y
6166 isImpliedCondOperandsHelper(Pred, LHS, RHS,
6167 getNotSCEV(FoundRHS),
6168 getNotSCEV(FoundLHS));
6171 /// isImpliedCondOperandsHelper - Test whether the condition described by
6172 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
6173 /// FoundLHS, and FoundRHS is true.
6175 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
6176 const SCEV *LHS, const SCEV *RHS,
6177 const SCEV *FoundLHS,
6178 const SCEV *FoundRHS) {
6180 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
6181 case ICmpInst::ICMP_EQ:
6182 case ICmpInst::ICMP_NE:
6183 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
6186 case ICmpInst::ICMP_SLT:
6187 case ICmpInst::ICMP_SLE:
6188 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
6189 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
6192 case ICmpInst::ICMP_SGT:
6193 case ICmpInst::ICMP_SGE:
6194 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
6195 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
6198 case ICmpInst::ICMP_ULT:
6199 case ICmpInst::ICMP_ULE:
6200 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
6201 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
6204 case ICmpInst::ICMP_UGT:
6205 case ICmpInst::ICMP_UGE:
6206 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
6207 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
6215 /// getBECount - Subtract the end and start values and divide by the step,
6216 /// rounding up, to get the number of times the backedge is executed. Return
6217 /// CouldNotCompute if an intermediate computation overflows.
6218 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
6222 assert(!isKnownNegative(Step) &&
6223 "This code doesn't handle negative strides yet!");
6225 Type *Ty = Start->getType();
6227 // When Start == End, we have an exact BECount == 0. Short-circuit this case
6228 // here because SCEV may not be able to determine that the unsigned division
6229 // after rounding is zero.
6231 return getConstant(Ty, 0);
6233 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
6234 const SCEV *Diff = getMinusSCEV(End, Start);
6235 const SCEV *RoundUp = getAddExpr(Step, NegOne);
6237 // Add an adjustment to the difference between End and Start so that
6238 // the division will effectively round up.
6239 const SCEV *Add = getAddExpr(Diff, RoundUp);
6242 // Check Add for unsigned overflow.
6243 // TODO: More sophisticated things could be done here.
6244 Type *WideTy = IntegerType::get(getContext(),
6245 getTypeSizeInBits(Ty) + 1);
6246 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
6247 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
6248 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
6249 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
6250 return getCouldNotCompute();
6253 return getUDivExpr(Add, Step);
6256 /// HowManyLessThans - Return the number of times a backedge containing the
6257 /// specified less-than comparison will execute. If not computable, return
6258 /// CouldNotCompute.
6259 ScalarEvolution::ExitLimit
6260 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
6261 const Loop *L, bool isSigned) {
6262 // Only handle: "ADDREC < LoopInvariant".
6263 if (!isLoopInvariant(RHS, L)) return getCouldNotCompute();
6265 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
6266 if (!AddRec || AddRec->getLoop() != L)
6267 return getCouldNotCompute();
6269 // Check to see if we have a flag which makes analysis easy.
6270 bool NoWrap = isSigned ?
6271 AddRec->getNoWrapFlags((SCEV::NoWrapFlags)(SCEV::FlagNSW | SCEV::FlagNW)) :
6272 AddRec->getNoWrapFlags((SCEV::NoWrapFlags)(SCEV::FlagNUW | SCEV::FlagNW));
6274 if (AddRec->isAffine()) {
6275 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
6276 const SCEV *Step = AddRec->getStepRecurrence(*this);
6279 return getCouldNotCompute();
6280 if (Step->isOne()) {
6281 // With unit stride, the iteration never steps past the limit value.
6282 } else if (isKnownPositive(Step)) {
6283 // Test whether a positive iteration can step past the limit
6284 // value and past the maximum value for its type in a single step.
6285 // Note that it's not sufficient to check NoWrap here, because even
6286 // though the value after a wrap is undefined, it's not undefined
6287 // behavior, so if wrap does occur, the loop could either terminate or
6288 // loop infinitely, but in either case, the loop is guaranteed to
6289 // iterate at least until the iteration where the wrapping occurs.
6290 const SCEV *One = getConstant(Step->getType(), 1);
6292 APInt Max = APInt::getSignedMaxValue(BitWidth);
6293 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
6294 .slt(getSignedRange(RHS).getSignedMax()))
6295 return getCouldNotCompute();
6297 APInt Max = APInt::getMaxValue(BitWidth);
6298 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
6299 .ult(getUnsignedRange(RHS).getUnsignedMax()))
6300 return getCouldNotCompute();
6303 // TODO: Handle negative strides here and below.
6304 return getCouldNotCompute();
6306 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
6307 // m. So, we count the number of iterations in which {n,+,s} < m is true.
6308 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
6309 // treat m-n as signed nor unsigned due to overflow possibility.
6311 // First, we get the value of the LHS in the first iteration: n
6312 const SCEV *Start = AddRec->getOperand(0);
6314 // Determine the minimum constant start value.
6315 const SCEV *MinStart = getConstant(isSigned ?
6316 getSignedRange(Start).getSignedMin() :
6317 getUnsignedRange(Start).getUnsignedMin());
6319 // If we know that the condition is true in order to enter the loop,
6320 // then we know that it will run exactly (m-n)/s times. Otherwise, we
6321 // only know that it will execute (max(m,n)-n)/s times. In both cases,
6322 // the division must round up.
6323 const SCEV *End = RHS;
6324 if (!isLoopEntryGuardedByCond(L,
6325 isSigned ? ICmpInst::ICMP_SLT :
6327 getMinusSCEV(Start, Step), RHS))
6328 End = isSigned ? getSMaxExpr(RHS, Start)
6329 : getUMaxExpr(RHS, Start);
6331 // Determine the maximum constant end value.
6332 const SCEV *MaxEnd = getConstant(isSigned ?
6333 getSignedRange(End).getSignedMax() :
6334 getUnsignedRange(End).getUnsignedMax());
6336 // If MaxEnd is within a step of the maximum integer value in its type,
6337 // adjust it down to the minimum value which would produce the same effect.
6338 // This allows the subsequent ceiling division of (N+(step-1))/step to
6339 // compute the correct value.
6340 const SCEV *StepMinusOne = getMinusSCEV(Step,
6341 getConstant(Step->getType(), 1));
6344 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
6347 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
6350 // Finally, we subtract these two values and divide, rounding up, to get
6351 // the number of times the backedge is executed.
6352 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
6354 // The maximum backedge count is similar, except using the minimum start
6355 // value and the maximum end value.
6356 // If we already have an exact constant BECount, use it instead.
6357 const SCEV *MaxBECount = isa<SCEVConstant>(BECount) ? BECount
6358 : getBECount(MinStart, MaxEnd, Step, NoWrap);
6360 // If the stride is nonconstant, and NoWrap == true, then
6361 // getBECount(MinStart, MaxEnd) may not compute. This would result in an
6362 // exact BECount and invalid MaxBECount, which should be avoided to catch
6363 // more optimization opportunities.
6364 if (isa<SCEVCouldNotCompute>(MaxBECount))
6365 MaxBECount = BECount;
6367 return ExitLimit(BECount, MaxBECount);
6370 return getCouldNotCompute();
6373 /// getNumIterationsInRange - Return the number of iterations of this loop that
6374 /// produce values in the specified constant range. Another way of looking at
6375 /// this is that it returns the first iteration number where the value is not in
6376 /// the condition, thus computing the exit count. If the iteration count can't
6377 /// be computed, an instance of SCEVCouldNotCompute is returned.
6378 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
6379 ScalarEvolution &SE) const {
6380 if (Range.isFullSet()) // Infinite loop.
6381 return SE.getCouldNotCompute();
6383 // If the start is a non-zero constant, shift the range to simplify things.
6384 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
6385 if (!SC->getValue()->isZero()) {
6386 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
6387 Operands[0] = SE.getConstant(SC->getType(), 0);
6388 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
6389 getNoWrapFlags(FlagNW));
6390 if (const SCEVAddRecExpr *ShiftedAddRec =
6391 dyn_cast<SCEVAddRecExpr>(Shifted))
6392 return ShiftedAddRec->getNumIterationsInRange(
6393 Range.subtract(SC->getValue()->getValue()), SE);
6394 // This is strange and shouldn't happen.
6395 return SE.getCouldNotCompute();
6398 // The only time we can solve this is when we have all constant indices.
6399 // Otherwise, we cannot determine the overflow conditions.
6400 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
6401 if (!isa<SCEVConstant>(getOperand(i)))
6402 return SE.getCouldNotCompute();
6405 // Okay at this point we know that all elements of the chrec are constants and
6406 // that the start element is zero.
6408 // First check to see if the range contains zero. If not, the first
6410 unsigned BitWidth = SE.getTypeSizeInBits(getType());
6411 if (!Range.contains(APInt(BitWidth, 0)))
6412 return SE.getConstant(getType(), 0);
6415 // If this is an affine expression then we have this situation:
6416 // Solve {0,+,A} in Range === Ax in Range
6418 // We know that zero is in the range. If A is positive then we know that
6419 // the upper value of the range must be the first possible exit value.
6420 // If A is negative then the lower of the range is the last possible loop
6421 // value. Also note that we already checked for a full range.
6422 APInt One(BitWidth,1);
6423 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
6424 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
6426 // The exit value should be (End+A)/A.
6427 APInt ExitVal = (End + A).udiv(A);
6428 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
6430 // Evaluate at the exit value. If we really did fall out of the valid
6431 // range, then we computed our trip count, otherwise wrap around or other
6432 // things must have happened.
6433 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
6434 if (Range.contains(Val->getValue()))
6435 return SE.getCouldNotCompute(); // Something strange happened
6437 // Ensure that the previous value is in the range. This is a sanity check.
6438 assert(Range.contains(
6439 EvaluateConstantChrecAtConstant(this,
6440 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
6441 "Linear scev computation is off in a bad way!");
6442 return SE.getConstant(ExitValue);
6443 } else if (isQuadratic()) {
6444 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
6445 // quadratic equation to solve it. To do this, we must frame our problem in
6446 // terms of figuring out when zero is crossed, instead of when
6447 // Range.getUpper() is crossed.
6448 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
6449 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
6450 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
6451 // getNoWrapFlags(FlagNW)
6454 // Next, solve the constructed addrec
6455 std::pair<const SCEV *,const SCEV *> Roots =
6456 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
6457 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
6458 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
6460 // Pick the smallest positive root value.
6461 if (ConstantInt *CB =
6462 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
6463 R1->getValue(), R2->getValue()))) {
6464 if (CB->getZExtValue() == false)
6465 std::swap(R1, R2); // R1 is the minimum root now.
6467 // Make sure the root is not off by one. The returned iteration should
6468 // not be in the range, but the previous one should be. When solving
6469 // for "X*X < 5", for example, we should not return a root of 2.
6470 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
6473 if (Range.contains(R1Val->getValue())) {
6474 // The next iteration must be out of the range...
6475 ConstantInt *NextVal =
6476 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
6478 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
6479 if (!Range.contains(R1Val->getValue()))
6480 return SE.getConstant(NextVal);
6481 return SE.getCouldNotCompute(); // Something strange happened
6484 // If R1 was not in the range, then it is a good return value. Make
6485 // sure that R1-1 WAS in the range though, just in case.
6486 ConstantInt *NextVal =
6487 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
6488 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
6489 if (Range.contains(R1Val->getValue()))
6491 return SE.getCouldNotCompute(); // Something strange happened
6496 return SE.getCouldNotCompute();
6501 //===----------------------------------------------------------------------===//
6502 // SCEVCallbackVH Class Implementation
6503 //===----------------------------------------------------------------------===//
6505 void ScalarEvolution::SCEVCallbackVH::deleted() {
6506 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
6507 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
6508 SE->ConstantEvolutionLoopExitValue.erase(PN);
6509 SE->ValueExprMap.erase(getValPtr());
6510 // this now dangles!
6513 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
6514 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
6516 // Forget all the expressions associated with users of the old value,
6517 // so that future queries will recompute the expressions using the new
6519 Value *Old = getValPtr();
6520 SmallVector<User *, 16> Worklist;
6521 SmallPtrSet<User *, 8> Visited;
6522 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
6524 Worklist.push_back(*UI);
6525 while (!Worklist.empty()) {
6526 User *U = Worklist.pop_back_val();
6527 // Deleting the Old value will cause this to dangle. Postpone
6528 // that until everything else is done.
6531 if (!Visited.insert(U))
6533 if (PHINode *PN = dyn_cast<PHINode>(U))
6534 SE->ConstantEvolutionLoopExitValue.erase(PN);
6535 SE->ValueExprMap.erase(U);
6536 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
6538 Worklist.push_back(*UI);
6540 // Delete the Old value.
6541 if (PHINode *PN = dyn_cast<PHINode>(Old))
6542 SE->ConstantEvolutionLoopExitValue.erase(PN);
6543 SE->ValueExprMap.erase(Old);
6544 // this now dangles!
6547 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
6548 : CallbackVH(V), SE(se) {}
6550 //===----------------------------------------------------------------------===//
6551 // ScalarEvolution Class Implementation
6552 //===----------------------------------------------------------------------===//
6554 ScalarEvolution::ScalarEvolution()
6555 : FunctionPass(ID), FirstUnknown(0) {
6556 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
6559 bool ScalarEvolution::runOnFunction(Function &F) {
6561 LI = &getAnalysis<LoopInfo>();
6562 TD = getAnalysisIfAvailable<TargetData>();
6563 DT = &getAnalysis<DominatorTree>();
6567 void ScalarEvolution::releaseMemory() {
6568 // Iterate through all the SCEVUnknown instances and call their
6569 // destructors, so that they release their references to their values.
6570 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
6574 ValueExprMap.clear();
6576 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
6577 // that a loop had multiple computable exits.
6578 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
6579 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end();
6584 BackedgeTakenCounts.clear();
6585 ConstantEvolutionLoopExitValue.clear();
6586 ValuesAtScopes.clear();
6587 LoopDispositions.clear();
6588 BlockDispositions.clear();
6589 UnsignedRanges.clear();
6590 SignedRanges.clear();
6591 UniqueSCEVs.clear();
6592 SCEVAllocator.Reset();
6595 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
6596 AU.setPreservesAll();
6597 AU.addRequiredTransitive<LoopInfo>();
6598 AU.addRequiredTransitive<DominatorTree>();
6601 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
6602 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
6605 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
6607 // Print all inner loops first
6608 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
6609 PrintLoopInfo(OS, SE, *I);
6612 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6615 SmallVector<BasicBlock *, 8> ExitBlocks;
6616 L->getExitBlocks(ExitBlocks);
6617 if (ExitBlocks.size() != 1)
6618 OS << "<multiple exits> ";
6620 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
6621 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
6623 OS << "Unpredictable backedge-taken count. ";
6628 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6631 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
6632 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
6634 OS << "Unpredictable max backedge-taken count. ";
6640 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
6641 // ScalarEvolution's implementation of the print method is to print
6642 // out SCEV values of all instructions that are interesting. Doing
6643 // this potentially causes it to create new SCEV objects though,
6644 // which technically conflicts with the const qualifier. This isn't
6645 // observable from outside the class though, so casting away the
6646 // const isn't dangerous.
6647 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6649 OS << "Classifying expressions for: ";
6650 WriteAsOperand(OS, F, /*PrintType=*/false);
6652 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
6653 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
6656 const SCEV *SV = SE.getSCEV(&*I);
6659 const Loop *L = LI->getLoopFor((*I).getParent());
6661 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
6668 OS << "\t\t" "Exits: ";
6669 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
6670 if (!SE.isLoopInvariant(ExitValue, L)) {
6671 OS << "<<Unknown>>";
6680 OS << "Determining loop execution counts for: ";
6681 WriteAsOperand(OS, F, /*PrintType=*/false);
6683 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
6684 PrintLoopInfo(OS, &SE, *I);
6687 ScalarEvolution::LoopDisposition
6688 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
6689 std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
6690 std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
6691 Values.insert(std::make_pair(L, LoopVariant));
6693 return Pair.first->second;
6695 LoopDisposition D = computeLoopDisposition(S, L);
6696 return LoopDispositions[S][L] = D;
6699 ScalarEvolution::LoopDisposition
6700 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
6701 switch (S->getSCEVType()) {
6703 return LoopInvariant;
6707 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
6708 case scAddRecExpr: {
6709 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6711 // If L is the addrec's loop, it's computable.
6712 if (AR->getLoop() == L)
6713 return LoopComputable;
6715 // Add recurrences are never invariant in the function-body (null loop).
6719 // This recurrence is variant w.r.t. L if L contains AR's loop.
6720 if (L->contains(AR->getLoop()))
6723 // This recurrence is invariant w.r.t. L if AR's loop contains L.
6724 if (AR->getLoop()->contains(L))
6725 return LoopInvariant;
6727 // This recurrence is variant w.r.t. L if any of its operands
6729 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
6731 if (!isLoopInvariant(*I, L))
6734 // Otherwise it's loop-invariant.
6735 return LoopInvariant;
6741 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6742 bool HasVarying = false;
6743 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6745 LoopDisposition D = getLoopDisposition(*I, L);
6746 if (D == LoopVariant)
6748 if (D == LoopComputable)
6751 return HasVarying ? LoopComputable : LoopInvariant;
6754 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6755 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
6756 if (LD == LoopVariant)
6758 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
6759 if (RD == LoopVariant)
6761 return (LD == LoopInvariant && RD == LoopInvariant) ?
6762 LoopInvariant : LoopComputable;
6765 // All non-instruction values are loop invariant. All instructions are loop
6766 // invariant if they are not contained in the specified loop.
6767 // Instructions are never considered invariant in the function body
6768 // (null loop) because they are defined within the "loop".
6769 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
6770 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
6771 return LoopInvariant;
6772 case scCouldNotCompute:
6773 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6777 llvm_unreachable("Unknown SCEV kind!");
6781 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
6782 return getLoopDisposition(S, L) == LoopInvariant;
6785 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
6786 return getLoopDisposition(S, L) == LoopComputable;
6789 ScalarEvolution::BlockDisposition
6790 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6791 std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
6792 std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
6793 Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
6795 return Pair.first->second;
6797 BlockDisposition D = computeBlockDisposition(S, BB);
6798 return BlockDispositions[S][BB] = D;
6801 ScalarEvolution::BlockDisposition
6802 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6803 switch (S->getSCEVType()) {
6805 return ProperlyDominatesBlock;
6809 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
6810 case scAddRecExpr: {
6811 // This uses a "dominates" query instead of "properly dominates" query
6812 // to test for proper dominance too, because the instruction which
6813 // produces the addrec's value is a PHI, and a PHI effectively properly
6814 // dominates its entire containing block.
6815 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6816 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
6817 return DoesNotDominateBlock;
6819 // FALL THROUGH into SCEVNAryExpr handling.
6824 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6826 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6828 BlockDisposition D = getBlockDisposition(*I, BB);
6829 if (D == DoesNotDominateBlock)
6830 return DoesNotDominateBlock;
6831 if (D == DominatesBlock)
6834 return Proper ? ProperlyDominatesBlock : DominatesBlock;
6837 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6838 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6839 BlockDisposition LD = getBlockDisposition(LHS, BB);
6840 if (LD == DoesNotDominateBlock)
6841 return DoesNotDominateBlock;
6842 BlockDisposition RD = getBlockDisposition(RHS, BB);
6843 if (RD == DoesNotDominateBlock)
6844 return DoesNotDominateBlock;
6845 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
6846 ProperlyDominatesBlock : DominatesBlock;
6849 if (Instruction *I =
6850 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
6851 if (I->getParent() == BB)
6852 return DominatesBlock;
6853 if (DT->properlyDominates(I->getParent(), BB))
6854 return ProperlyDominatesBlock;
6855 return DoesNotDominateBlock;
6857 return ProperlyDominatesBlock;
6858 case scCouldNotCompute:
6859 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6860 return DoesNotDominateBlock;
6863 llvm_unreachable("Unknown SCEV kind!");
6864 return DoesNotDominateBlock;
6867 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
6868 return getBlockDisposition(S, BB) >= DominatesBlock;
6871 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
6872 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
6875 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
6876 switch (S->getSCEVType()) {
6881 case scSignExtend: {
6882 const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
6883 const SCEV *CastOp = Cast->getOperand();
6884 return Op == CastOp || hasOperand(CastOp, Op);
6891 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6892 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6894 const SCEV *NAryOp = *I;
6895 if (NAryOp == Op || hasOperand(NAryOp, Op))
6901 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6902 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6903 return LHS == Op || hasOperand(LHS, Op) ||
6904 RHS == Op || hasOperand(RHS, Op);
6908 case scCouldNotCompute:
6909 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6913 llvm_unreachable("Unknown SCEV kind!");
6917 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
6918 ValuesAtScopes.erase(S);
6919 LoopDispositions.erase(S);
6920 BlockDispositions.erase(S);
6921 UnsignedRanges.erase(S);
6922 SignedRanges.erase(S);