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)
194 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
195 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
199 const SCEVUnknown *U = cast<SCEVUnknown>(this);
201 if (U->isSizeOf(AllocTy)) {
202 OS << "sizeof(" << *AllocTy << ")";
205 if (U->isAlignOf(AllocTy)) {
206 OS << "alignof(" << *AllocTy << ")";
212 if (U->isOffsetOf(CTy, FieldNo)) {
213 OS << "offsetof(" << *CTy << ", ";
214 WriteAsOperand(OS, FieldNo, false);
219 // Otherwise just print it normally.
220 WriteAsOperand(OS, U->getValue(), false);
223 case scCouldNotCompute:
224 OS << "***COULDNOTCOMPUTE***";
228 llvm_unreachable("Unknown SCEV kind!");
231 Type *SCEV::getType() const {
232 switch (getSCEVType()) {
234 return cast<SCEVConstant>(this)->getType();
238 return cast<SCEVCastExpr>(this)->getType();
243 return cast<SCEVNAryExpr>(this)->getType();
245 return cast<SCEVAddExpr>(this)->getType();
247 return cast<SCEVUDivExpr>(this)->getType();
249 return cast<SCEVUnknown>(this)->getType();
250 case scCouldNotCompute:
251 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
255 llvm_unreachable("Unknown SCEV kind!");
259 bool SCEV::isZero() const {
260 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
261 return SC->getValue()->isZero();
265 bool SCEV::isOne() const {
266 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
267 return SC->getValue()->isOne();
271 bool SCEV::isAllOnesValue() const {
272 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
273 return SC->getValue()->isAllOnesValue();
277 SCEVCouldNotCompute::SCEVCouldNotCompute() :
278 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
280 bool SCEVCouldNotCompute::classof(const SCEV *S) {
281 return S->getSCEVType() == scCouldNotCompute;
284 const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
286 ID.AddInteger(scConstant);
289 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
290 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
291 UniqueSCEVs.InsertNode(S, IP);
295 const SCEV *ScalarEvolution::getConstant(const APInt& Val) {
296 return getConstant(ConstantInt::get(getContext(), Val));
300 ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
301 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
302 return getConstant(ConstantInt::get(ITy, V, isSigned));
305 SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
306 unsigned SCEVTy, const SCEV *op, Type *ty)
307 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
309 SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
310 const SCEV *op, Type *ty)
311 : SCEVCastExpr(ID, scTruncate, op, ty) {
312 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
313 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
314 "Cannot truncate non-integer value!");
317 SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
318 const SCEV *op, Type *ty)
319 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
320 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
321 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
322 "Cannot zero extend non-integer value!");
325 SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
326 const SCEV *op, Type *ty)
327 : SCEVCastExpr(ID, scSignExtend, op, ty) {
328 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&
329 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
330 "Cannot sign extend non-integer value!");
333 void SCEVUnknown::deleted() {
334 // Clear this SCEVUnknown from various maps.
335 SE->forgetMemoizedResults(this);
337 // Remove this SCEVUnknown from the uniquing map.
338 SE->UniqueSCEVs.RemoveNode(this);
340 // Release the value.
344 void SCEVUnknown::allUsesReplacedWith(Value *New) {
345 // Clear this SCEVUnknown from various maps.
346 SE->forgetMemoizedResults(this);
348 // Remove this SCEVUnknown from the uniquing map.
349 SE->UniqueSCEVs.RemoveNode(this);
351 // Update this SCEVUnknown to point to the new value. This is needed
352 // because there may still be outstanding SCEVs which still point to
357 bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
358 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
359 if (VCE->getOpcode() == Instruction::PtrToInt)
360 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
361 if (CE->getOpcode() == Instruction::GetElementPtr &&
362 CE->getOperand(0)->isNullValue() &&
363 CE->getNumOperands() == 2)
364 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
366 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
374 bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
375 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
376 if (VCE->getOpcode() == Instruction::PtrToInt)
377 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
378 if (CE->getOpcode() == Instruction::GetElementPtr &&
379 CE->getOperand(0)->isNullValue()) {
381 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
382 if (StructType *STy = dyn_cast<StructType>(Ty))
383 if (!STy->isPacked() &&
384 CE->getNumOperands() == 3 &&
385 CE->getOperand(1)->isNullValue()) {
386 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
388 STy->getNumElements() == 2 &&
389 STy->getElementType(0)->isIntegerTy(1)) {
390 AllocTy = STy->getElementType(1);
399 bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
400 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
401 if (VCE->getOpcode() == Instruction::PtrToInt)
402 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
403 if (CE->getOpcode() == Instruction::GetElementPtr &&
404 CE->getNumOperands() == 3 &&
405 CE->getOperand(0)->isNullValue() &&
406 CE->getOperand(1)->isNullValue()) {
408 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
409 // Ignore vector types here so that ScalarEvolutionExpander doesn't
410 // emit getelementptrs that index into vectors.
411 if (Ty->isStructTy() || Ty->isArrayTy()) {
413 FieldNo = CE->getOperand(2);
421 //===----------------------------------------------------------------------===//
423 //===----------------------------------------------------------------------===//
426 /// SCEVComplexityCompare - Return true if the complexity of the LHS is less
427 /// than the complexity of the RHS. This comparator is used to canonicalize
429 class SCEVComplexityCompare {
430 const LoopInfo *const LI;
432 explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
434 // Return true or false if LHS is less than, or at least RHS, respectively.
435 bool operator()(const SCEV *LHS, const SCEV *RHS) const {
436 return compare(LHS, RHS) < 0;
439 // Return negative, zero, or positive, if LHS is less than, equal to, or
440 // greater than RHS, respectively. A three-way result allows recursive
441 // comparisons to be more efficient.
442 int compare(const SCEV *LHS, const SCEV *RHS) const {
443 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
447 // Primarily, sort the SCEVs by their getSCEVType().
448 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
450 return (int)LType - (int)RType;
452 // Aside from the getSCEVType() ordering, the particular ordering
453 // isn't very important except that it's beneficial to be consistent,
454 // so that (a + b) and (b + a) don't end up as different expressions.
457 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
458 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
460 // Sort SCEVUnknown values with some loose heuristics. TODO: This is
461 // not as complete as it could be.
462 const Value *LV = LU->getValue(), *RV = RU->getValue();
464 // Order pointer values after integer values. This helps SCEVExpander
466 bool LIsPointer = LV->getType()->isPointerTy(),
467 RIsPointer = RV->getType()->isPointerTy();
468 if (LIsPointer != RIsPointer)
469 return (int)LIsPointer - (int)RIsPointer;
471 // Compare getValueID values.
472 unsigned LID = LV->getValueID(),
473 RID = RV->getValueID();
475 return (int)LID - (int)RID;
477 // Sort arguments by their position.
478 if (const Argument *LA = dyn_cast<Argument>(LV)) {
479 const Argument *RA = cast<Argument>(RV);
480 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
481 return (int)LArgNo - (int)RArgNo;
484 // For instructions, compare their loop depth, and their operand
485 // count. This is pretty loose.
486 if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
487 const Instruction *RInst = cast<Instruction>(RV);
489 // Compare loop depths.
490 const BasicBlock *LParent = LInst->getParent(),
491 *RParent = RInst->getParent();
492 if (LParent != RParent) {
493 unsigned LDepth = LI->getLoopDepth(LParent),
494 RDepth = LI->getLoopDepth(RParent);
495 if (LDepth != RDepth)
496 return (int)LDepth - (int)RDepth;
499 // Compare the number of operands.
500 unsigned LNumOps = LInst->getNumOperands(),
501 RNumOps = RInst->getNumOperands();
502 return (int)LNumOps - (int)RNumOps;
509 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
510 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
512 // Compare constant values.
513 const APInt &LA = LC->getValue()->getValue();
514 const APInt &RA = RC->getValue()->getValue();
515 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
516 if (LBitWidth != RBitWidth)
517 return (int)LBitWidth - (int)RBitWidth;
518 return LA.ult(RA) ? -1 : 1;
522 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
523 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
525 // Compare addrec loop depths.
526 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
527 if (LLoop != RLoop) {
528 unsigned LDepth = LLoop->getLoopDepth(),
529 RDepth = RLoop->getLoopDepth();
530 if (LDepth != RDepth)
531 return (int)LDepth - (int)RDepth;
534 // Addrec complexity grows with operand count.
535 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
536 if (LNumOps != RNumOps)
537 return (int)LNumOps - (int)RNumOps;
539 // Lexicographically compare.
540 for (unsigned i = 0; i != LNumOps; ++i) {
541 long X = compare(LA->getOperand(i), RA->getOperand(i));
553 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
554 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
556 // Lexicographically compare n-ary expressions.
557 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
558 for (unsigned i = 0; i != LNumOps; ++i) {
561 long X = compare(LC->getOperand(i), RC->getOperand(i));
565 return (int)LNumOps - (int)RNumOps;
569 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
570 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
572 // Lexicographically compare udiv expressions.
573 long X = compare(LC->getLHS(), RC->getLHS());
576 return compare(LC->getRHS(), RC->getRHS());
582 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
583 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
585 // Compare cast expressions by operand.
586 return compare(LC->getOperand(), RC->getOperand());
593 llvm_unreachable("Unknown SCEV kind!");
599 /// GroupByComplexity - Given a list of SCEV objects, order them by their
600 /// complexity, and group objects of the same complexity together by value.
601 /// When this routine is finished, we know that any duplicates in the vector are
602 /// consecutive and that complexity is monotonically increasing.
604 /// Note that we go take special precautions to ensure that we get deterministic
605 /// results from this routine. In other words, we don't want the results of
606 /// this to depend on where the addresses of various SCEV objects happened to
609 static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
611 if (Ops.size() < 2) return; // Noop
612 if (Ops.size() == 2) {
613 // This is the common case, which also happens to be trivially simple.
615 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
616 if (SCEVComplexityCompare(LI)(RHS, LHS))
621 // Do the rough sort by complexity.
622 std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
624 // Now that we are sorted by complexity, group elements of the same
625 // complexity. Note that this is, at worst, N^2, but the vector is likely to
626 // be extremely short in practice. Note that we take this approach because we
627 // do not want to depend on the addresses of the objects we are grouping.
628 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
629 const SCEV *S = Ops[i];
630 unsigned Complexity = S->getSCEVType();
632 // If there are any objects of the same complexity and same value as this
634 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
635 if (Ops[j] == S) { // Found a duplicate.
636 // Move it to immediately after i'th element.
637 std::swap(Ops[i+1], Ops[j]);
638 ++i; // no need to rescan it.
639 if (i == e-2) return; // Done!
647 //===----------------------------------------------------------------------===//
648 // Simple SCEV method implementations
649 //===----------------------------------------------------------------------===//
651 /// BinomialCoefficient - Compute BC(It, K). The result has width W.
653 static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
656 // Handle the simplest case efficiently.
658 return SE.getTruncateOrZeroExtend(It, ResultTy);
660 // We are using the following formula for BC(It, K):
662 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
664 // Suppose, W is the bitwidth of the return value. We must be prepared for
665 // overflow. Hence, we must assure that the result of our computation is
666 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
667 // safe in modular arithmetic.
669 // However, this code doesn't use exactly that formula; the formula it uses
670 // is something like the following, where T is the number of factors of 2 in
671 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
674 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
676 // This formula is trivially equivalent to the previous formula. However,
677 // this formula can be implemented much more efficiently. The trick is that
678 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
679 // arithmetic. To do exact division in modular arithmetic, all we have
680 // to do is multiply by the inverse. Therefore, this step can be done at
683 // The next issue is how to safely do the division by 2^T. The way this
684 // is done is by doing the multiplication step at a width of at least W + T
685 // bits. This way, the bottom W+T bits of the product are accurate. Then,
686 // when we perform the division by 2^T (which is equivalent to a right shift
687 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
688 // truncated out after the division by 2^T.
690 // In comparison to just directly using the first formula, this technique
691 // is much more efficient; using the first formula requires W * K bits,
692 // but this formula less than W + K bits. Also, the first formula requires
693 // a division step, whereas this formula only requires multiplies and shifts.
695 // It doesn't matter whether the subtraction step is done in the calculation
696 // width or the input iteration count's width; if the subtraction overflows,
697 // the result must be zero anyway. We prefer here to do it in the width of
698 // the induction variable because it helps a lot for certain cases; CodeGen
699 // isn't smart enough to ignore the overflow, which leads to much less
700 // efficient code if the width of the subtraction is wider than the native
703 // (It's possible to not widen at all by pulling out factors of 2 before
704 // the multiplication; for example, K=2 can be calculated as
705 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
706 // extra arithmetic, so it's not an obvious win, and it gets
707 // much more complicated for K > 3.)
709 // Protection from insane SCEVs; this bound is conservative,
710 // but it probably doesn't matter.
712 return SE.getCouldNotCompute();
714 unsigned W = SE.getTypeSizeInBits(ResultTy);
716 // Calculate K! / 2^T and T; we divide out the factors of two before
717 // multiplying for calculating K! / 2^T to avoid overflow.
718 // Other overflow doesn't matter because we only care about the bottom
719 // W bits of the result.
720 APInt OddFactorial(W, 1);
722 for (unsigned i = 3; i <= K; ++i) {
724 unsigned TwoFactors = Mult.countTrailingZeros();
726 Mult = Mult.lshr(TwoFactors);
727 OddFactorial *= Mult;
730 // We need at least W + T bits for the multiplication step
731 unsigned CalculationBits = W + T;
733 // Calculate 2^T, at width T+W.
734 APInt DivFactor = APInt(CalculationBits, 1).shl(T);
736 // Calculate the multiplicative inverse of K! / 2^T;
737 // this multiplication factor will perform the exact division by
739 APInt Mod = APInt::getSignedMinValue(W+1);
740 APInt MultiplyFactor = OddFactorial.zext(W+1);
741 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
742 MultiplyFactor = MultiplyFactor.trunc(W);
744 // Calculate the product, at width T+W
745 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
747 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
748 for (unsigned i = 1; i != K; ++i) {
749 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
750 Dividend = SE.getMulExpr(Dividend,
751 SE.getTruncateOrZeroExtend(S, CalculationTy));
755 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
757 // Truncate the result, and divide by K! / 2^T.
759 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
760 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
763 /// evaluateAtIteration - Return the value of this chain of recurrences at
764 /// the specified iteration number. We can evaluate this recurrence by
765 /// multiplying each element in the chain by the binomial coefficient
766 /// corresponding to it. In other words, we can evaluate {A,+,B,+,C,+,D} as:
768 /// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
770 /// where BC(It, k) stands for binomial coefficient.
772 const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
773 ScalarEvolution &SE) const {
774 const SCEV *Result = getStart();
775 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
776 // The computation is correct in the face of overflow provided that the
777 // multiplication is performed _after_ the evaluation of the binomial
779 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
780 if (isa<SCEVCouldNotCompute>(Coeff))
783 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
788 //===----------------------------------------------------------------------===//
789 // SCEV Expression folder implementations
790 //===----------------------------------------------------------------------===//
792 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
794 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&
795 "This is not a truncating conversion!");
796 assert(isSCEVable(Ty) &&
797 "This is not a conversion to a SCEVable type!");
798 Ty = getEffectiveSCEVType(Ty);
801 ID.AddInteger(scTruncate);
805 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
807 // Fold if the operand is constant.
808 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
810 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
811 getEffectiveSCEVType(Ty))));
813 // trunc(trunc(x)) --> trunc(x)
814 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
815 return getTruncateExpr(ST->getOperand(), Ty);
817 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
818 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
819 return getTruncateOrSignExtend(SS->getOperand(), Ty);
821 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
822 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
823 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
825 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
826 // eliminate all the truncates.
827 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
828 SmallVector<const SCEV *, 4> Operands;
829 bool hasTrunc = false;
830 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
831 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
832 hasTrunc = isa<SCEVTruncateExpr>(S);
833 Operands.push_back(S);
836 return getAddExpr(Operands);
837 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
840 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
841 // eliminate all the truncates.
842 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
843 SmallVector<const SCEV *, 4> Operands;
844 bool hasTrunc = false;
845 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
846 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
847 hasTrunc = isa<SCEVTruncateExpr>(S);
848 Operands.push_back(S);
851 return getMulExpr(Operands);
852 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
855 // If the input value is a chrec scev, truncate the chrec's operands.
856 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
857 SmallVector<const SCEV *, 4> Operands;
858 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
859 Operands.push_back(getTruncateExpr(AddRec->getOperand(i), Ty));
860 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
863 // As a special case, fold trunc(undef) to undef. We don't want to
864 // know too much about SCEVUnknowns, but this special case is handy
866 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
867 if (isa<UndefValue>(U->getValue()))
868 return getSCEV(UndefValue::get(Ty));
870 // The cast wasn't folded; create an explicit cast node. We can reuse
871 // the existing insert position since if we get here, we won't have
872 // made any changes which would invalidate it.
873 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
875 UniqueSCEVs.InsertNode(S, IP);
879 const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
881 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
882 "This is not an extending conversion!");
883 assert(isSCEVable(Ty) &&
884 "This is not a conversion to a SCEVable type!");
885 Ty = getEffectiveSCEVType(Ty);
887 // Fold if the operand is constant.
888 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
890 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
891 getEffectiveSCEVType(Ty))));
893 // zext(zext(x)) --> zext(x)
894 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
895 return getZeroExtendExpr(SZ->getOperand(), Ty);
897 // Before doing any expensive analysis, check to see if we've already
898 // computed a SCEV for this Op and Ty.
900 ID.AddInteger(scZeroExtend);
904 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
906 // zext(trunc(x)) --> zext(x) or x or trunc(x)
907 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
908 // It's possible the bits taken off by the truncate were all zero bits. If
909 // so, we should be able to simplify this further.
910 const SCEV *X = ST->getOperand();
911 ConstantRange CR = getUnsignedRange(X);
912 unsigned TruncBits = getTypeSizeInBits(ST->getType());
913 unsigned NewBits = getTypeSizeInBits(Ty);
914 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
915 CR.zextOrTrunc(NewBits)))
916 return getTruncateOrZeroExtend(X, Ty);
919 // If the input value is a chrec scev, and we can prove that the value
920 // did not overflow the old, smaller, value, we can zero extend all of the
921 // operands (often constants). This allows analysis of something like
922 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
923 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
924 if (AR->isAffine()) {
925 const SCEV *Start = AR->getStart();
926 const SCEV *Step = AR->getStepRecurrence(*this);
927 unsigned BitWidth = getTypeSizeInBits(AR->getType());
928 const Loop *L = AR->getLoop();
930 // If we have special knowledge that this addrec won't overflow,
931 // we don't need to do any further analysis.
932 if (AR->getNoWrapFlags(SCEV::FlagNUW))
933 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
934 getZeroExtendExpr(Step, Ty),
935 L, AR->getNoWrapFlags());
937 // Check whether the backedge-taken count is SCEVCouldNotCompute.
938 // Note that this serves two purposes: It filters out loops that are
939 // simply not analyzable, and it covers the case where this code is
940 // being called from within backedge-taken count analysis, such that
941 // attempting to ask for the backedge-taken count would likely result
942 // in infinite recursion. In the later case, the analysis code will
943 // cope with a conservative value, and it will take care to purge
944 // that value once it has finished.
945 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
946 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
947 // Manually compute the final value for AR, checking for
950 // Check whether the backedge-taken count can be losslessly casted to
951 // the addrec's type. The count is always unsigned.
952 const SCEV *CastedMaxBECount =
953 getTruncateOrZeroExtend(MaxBECount, Start->getType());
954 const SCEV *RecastedMaxBECount =
955 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
956 if (MaxBECount == RecastedMaxBECount) {
957 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
958 // Check whether Start+Step*MaxBECount has no unsigned overflow.
959 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
960 const SCEV *Add = getAddExpr(Start, ZMul);
961 const SCEV *OperandExtendedAdd =
962 getAddExpr(getZeroExtendExpr(Start, WideTy),
963 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
964 getZeroExtendExpr(Step, WideTy)));
965 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd) {
966 // Cache knowledge of AR NUW, which is propagated to this AddRec.
967 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
968 // Return the expression with the addrec on the outside.
969 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
970 getZeroExtendExpr(Step, Ty),
971 L, AR->getNoWrapFlags());
973 // Similar to above, only this time treat the step value as signed.
974 // This covers loops that count down.
975 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
976 Add = getAddExpr(Start, SMul);
978 getAddExpr(getZeroExtendExpr(Start, WideTy),
979 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
980 getSignExtendExpr(Step, WideTy)));
981 if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd) {
982 // Cache knowledge of AR NW, which is propagated to this AddRec.
983 // Negative step causes unsigned wrap, but it still can't self-wrap.
984 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
985 // Return the expression with the addrec on the outside.
986 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
987 getSignExtendExpr(Step, Ty),
988 L, AR->getNoWrapFlags());
992 // If the backedge is guarded by a comparison with the pre-inc value
993 // the addrec is safe. Also, if the entry is guarded by a comparison
994 // with the start value and the backedge is guarded by a comparison
995 // with the post-inc value, the addrec is safe.
996 if (isKnownPositive(Step)) {
997 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
998 getUnsignedRange(Step).getUnsignedMax());
999 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1000 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1001 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1002 AR->getPostIncExpr(*this), N))) {
1003 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1004 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1005 // Return the expression with the addrec on the outside.
1006 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1007 getZeroExtendExpr(Step, Ty),
1008 L, AR->getNoWrapFlags());
1010 } else if (isKnownNegative(Step)) {
1011 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1012 getSignedRange(Step).getSignedMin());
1013 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1014 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1015 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1016 AR->getPostIncExpr(*this), N))) {
1017 // Cache knowledge of AR NW, which is propagated to this AddRec.
1018 // Negative step causes unsigned wrap, but it still can't self-wrap.
1019 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1020 // Return the expression with the addrec on the outside.
1021 return getAddRecExpr(getZeroExtendExpr(Start, Ty),
1022 getSignExtendExpr(Step, Ty),
1023 L, AR->getNoWrapFlags());
1029 // The cast wasn't folded; create an explicit cast node.
1030 // Recompute the insert position, as it may have been invalidated.
1031 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1032 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1034 UniqueSCEVs.InsertNode(S, IP);
1038 // Get the limit of a recurrence such that incrementing by Step cannot cause
1039 // signed overflow as long as the value of the recurrence within the loop does
1040 // not exceed this limit before incrementing.
1041 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1042 ICmpInst::Predicate *Pred,
1043 ScalarEvolution *SE) {
1044 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1045 if (SE->isKnownPositive(Step)) {
1046 *Pred = ICmpInst::ICMP_SLT;
1047 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1048 SE->getSignedRange(Step).getSignedMax());
1050 if (SE->isKnownNegative(Step)) {
1051 *Pred = ICmpInst::ICMP_SGT;
1052 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1053 SE->getSignedRange(Step).getSignedMin());
1058 // The recurrence AR has been shown to have no signed wrap. Typically, if we can
1059 // prove NSW for AR, then we can just as easily prove NSW for its preincrement
1060 // or postincrement sibling. This allows normalizing a sign extended AddRec as
1061 // such: {sext(Step + Start),+,Step} => {(Step + sext(Start),+,Step} As a
1062 // result, the expression "Step + sext(PreIncAR)" is congruent with
1063 // "sext(PostIncAR)"
1064 static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR,
1066 ScalarEvolution *SE) {
1067 const Loop *L = AR->getLoop();
1068 const SCEV *Start = AR->getStart();
1069 const SCEV *Step = AR->getStepRecurrence(*SE);
1071 // Check for a simple looking step prior to loop entry.
1072 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1073 if (!SA || SA->getNumOperands() != 2 || SA->getOperand(0) != Step)
1076 // This is a postinc AR. Check for overflow on the preinc recurrence using the
1077 // same three conditions that getSignExtendedExpr checks.
1079 // 1. NSW flags on the step increment.
1080 const SCEV *PreStart = SA->getOperand(1);
1081 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1082 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1084 if (PreAR && PreAR->getNoWrapFlags(SCEV::FlagNSW))
1087 // 2. Direct overflow check on the step operation's expression.
1088 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1089 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1090 const SCEV *OperandExtendedStart =
1091 SE->getAddExpr(SE->getSignExtendExpr(PreStart, WideTy),
1092 SE->getSignExtendExpr(Step, WideTy));
1093 if (SE->getSignExtendExpr(Start, WideTy) == OperandExtendedStart) {
1094 // Cache knowledge of PreAR NSW.
1096 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(SCEV::FlagNSW);
1097 // FIXME: this optimization needs a unit test
1098 DEBUG(dbgs() << "SCEV: untested prestart overflow check\n");
1102 // 3. Loop precondition.
1103 ICmpInst::Predicate Pred;
1104 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, SE);
1106 if (OverflowLimit &&
1107 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit)) {
1113 // Get the normalized sign-extended expression for this AddRec's Start.
1114 static const SCEV *getSignExtendAddRecStart(const SCEVAddRecExpr *AR,
1116 ScalarEvolution *SE) {
1117 const SCEV *PreStart = getPreStartForSignExtend(AR, Ty, SE);
1119 return SE->getSignExtendExpr(AR->getStart(), Ty);
1121 return SE->getAddExpr(SE->getSignExtendExpr(AR->getStepRecurrence(*SE), Ty),
1122 SE->getSignExtendExpr(PreStart, Ty));
1125 const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1127 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1128 "This is not an extending conversion!");
1129 assert(isSCEVable(Ty) &&
1130 "This is not a conversion to a SCEVable type!");
1131 Ty = getEffectiveSCEVType(Ty);
1133 // Fold if the operand is constant.
1134 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1136 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
1137 getEffectiveSCEVType(Ty))));
1139 // sext(sext(x)) --> sext(x)
1140 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1141 return getSignExtendExpr(SS->getOperand(), Ty);
1143 // sext(zext(x)) --> zext(x)
1144 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1145 return getZeroExtendExpr(SZ->getOperand(), Ty);
1147 // Before doing any expensive analysis, check to see if we've already
1148 // computed a SCEV for this Op and Ty.
1149 FoldingSetNodeID ID;
1150 ID.AddInteger(scSignExtend);
1154 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1156 // If the input value is provably positive, build a zext instead.
1157 if (isKnownNonNegative(Op))
1158 return getZeroExtendExpr(Op, Ty);
1160 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1161 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1162 // It's possible the bits taken off by the truncate were all sign bits. If
1163 // so, we should be able to simplify this further.
1164 const SCEV *X = ST->getOperand();
1165 ConstantRange CR = getSignedRange(X);
1166 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1167 unsigned NewBits = getTypeSizeInBits(Ty);
1168 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1169 CR.sextOrTrunc(NewBits)))
1170 return getTruncateOrSignExtend(X, Ty);
1173 // If the input value is a chrec scev, and we can prove that the value
1174 // did not overflow the old, smaller, value, we can sign extend all of the
1175 // operands (often constants). This allows analysis of something like
1176 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1177 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1178 if (AR->isAffine()) {
1179 const SCEV *Start = AR->getStart();
1180 const SCEV *Step = AR->getStepRecurrence(*this);
1181 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1182 const Loop *L = AR->getLoop();
1184 // If we have special knowledge that this addrec won't overflow,
1185 // we don't need to do any further analysis.
1186 if (AR->getNoWrapFlags(SCEV::FlagNSW))
1187 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1188 getSignExtendExpr(Step, Ty),
1191 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1192 // Note that this serves two purposes: It filters out loops that are
1193 // simply not analyzable, and it covers the case where this code is
1194 // being called from within backedge-taken count analysis, such that
1195 // attempting to ask for the backedge-taken count would likely result
1196 // in infinite recursion. In the later case, the analysis code will
1197 // cope with a conservative value, and it will take care to purge
1198 // that value once it has finished.
1199 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1200 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1201 // Manually compute the final value for AR, checking for
1204 // Check whether the backedge-taken count can be losslessly casted to
1205 // the addrec's type. The count is always unsigned.
1206 const SCEV *CastedMaxBECount =
1207 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1208 const SCEV *RecastedMaxBECount =
1209 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1210 if (MaxBECount == RecastedMaxBECount) {
1211 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1212 // Check whether Start+Step*MaxBECount has no signed overflow.
1213 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1214 const SCEV *Add = getAddExpr(Start, SMul);
1215 const SCEV *OperandExtendedAdd =
1216 getAddExpr(getSignExtendExpr(Start, WideTy),
1217 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1218 getSignExtendExpr(Step, WideTy)));
1219 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd) {
1220 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1221 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1222 // Return the expression with the addrec on the outside.
1223 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1224 getSignExtendExpr(Step, Ty),
1225 L, AR->getNoWrapFlags());
1227 // Similar to above, only this time treat the step value as unsigned.
1228 // This covers loops that count up with an unsigned step.
1229 const SCEV *UMul = getMulExpr(CastedMaxBECount, Step);
1230 Add = getAddExpr(Start, UMul);
1231 OperandExtendedAdd =
1232 getAddExpr(getSignExtendExpr(Start, WideTy),
1233 getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
1234 getZeroExtendExpr(Step, WideTy)));
1235 if (getSignExtendExpr(Add, WideTy) == OperandExtendedAdd) {
1236 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1237 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1238 // Return the expression with the addrec on the outside.
1239 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1240 getZeroExtendExpr(Step, Ty),
1241 L, AR->getNoWrapFlags());
1245 // If the backedge is guarded by a comparison with the pre-inc value
1246 // the addrec is safe. Also, if the entry is guarded by a comparison
1247 // with the start value and the backedge is guarded by a comparison
1248 // with the post-inc value, the addrec is safe.
1249 ICmpInst::Predicate Pred;
1250 const SCEV *OverflowLimit = getOverflowLimitForStep(Step, &Pred, this);
1251 if (OverflowLimit &&
1252 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1253 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1254 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1256 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1257 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1258 return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
1259 getSignExtendExpr(Step, Ty),
1260 L, AR->getNoWrapFlags());
1265 // The cast wasn't folded; create an explicit cast node.
1266 // Recompute the insert position, as it may have been invalidated.
1267 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1268 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1270 UniqueSCEVs.InsertNode(S, IP);
1274 /// getAnyExtendExpr - Return a SCEV for the given operand extended with
1275 /// unspecified bits out to the given type.
1277 const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1279 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
1280 "This is not an extending conversion!");
1281 assert(isSCEVable(Ty) &&
1282 "This is not a conversion to a SCEVable type!");
1283 Ty = getEffectiveSCEVType(Ty);
1285 // Sign-extend negative constants.
1286 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1287 if (SC->getValue()->getValue().isNegative())
1288 return getSignExtendExpr(Op, Ty);
1290 // Peel off a truncate cast.
1291 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1292 const SCEV *NewOp = T->getOperand();
1293 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1294 return getAnyExtendExpr(NewOp, Ty);
1295 return getTruncateOrNoop(NewOp, Ty);
1298 // Next try a zext cast. If the cast is folded, use it.
1299 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1300 if (!isa<SCEVZeroExtendExpr>(ZExt))
1303 // Next try a sext cast. If the cast is folded, use it.
1304 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1305 if (!isa<SCEVSignExtendExpr>(SExt))
1308 // Force the cast to be folded into the operands of an addrec.
1309 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1310 SmallVector<const SCEV *, 4> Ops;
1311 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
1313 Ops.push_back(getAnyExtendExpr(*I, Ty));
1314 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1317 // As a special case, fold anyext(undef) to undef. We don't want to
1318 // know too much about SCEVUnknowns, but this special case is handy
1320 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
1321 if (isa<UndefValue>(U->getValue()))
1322 return getSCEV(UndefValue::get(Ty));
1324 // If the expression is obviously signed, use the sext cast value.
1325 if (isa<SCEVSMaxExpr>(Op))
1328 // Absent any other information, use the zext cast value.
1332 /// CollectAddOperandsWithScales - Process the given Ops list, which is
1333 /// a list of operands to be added under the given scale, update the given
1334 /// map. This is a helper function for getAddRecExpr. As an example of
1335 /// what it does, given a sequence of operands that would form an add
1336 /// expression like this:
1338 /// m + n + 13 + (A * (o + p + (B * q + m + 29))) + r + (-1 * r)
1340 /// where A and B are constants, update the map with these values:
1342 /// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1344 /// and add 13 + A*B*29 to AccumulatedConstant.
1345 /// This will allow getAddRecExpr to produce this:
1347 /// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1349 /// This form often exposes folding opportunities that are hidden in
1350 /// the original operand list.
1352 /// Return true iff it appears that any interesting folding opportunities
1353 /// may be exposed. This helps getAddRecExpr short-circuit extra work in
1354 /// the common case where no interesting opportunities are present, and
1355 /// is also used as a check to avoid infinite recursion.
1358 CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1359 SmallVector<const SCEV *, 8> &NewOps,
1360 APInt &AccumulatedConstant,
1361 const SCEV *const *Ops, size_t NumOperands,
1363 ScalarEvolution &SE) {
1364 bool Interesting = false;
1366 // Iterate over the add operands. They are sorted, with constants first.
1368 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1370 // Pull a buried constant out to the outside.
1371 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
1373 AccumulatedConstant += Scale * C->getValue()->getValue();
1376 // Next comes everything else. We're especially interested in multiplies
1377 // here, but they're in the middle, so just visit the rest with one loop.
1378 for (; i != NumOperands; ++i) {
1379 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
1380 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
1382 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getValue()->getValue();
1383 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
1384 // A multiplication of a constant with another add; recurse.
1385 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
1387 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1388 Add->op_begin(), Add->getNumOperands(),
1391 // A multiplication of a constant with some other value. Update
1393 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
1394 const SCEV *Key = SE.getMulExpr(MulOps);
1395 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1396 M.insert(std::make_pair(Key, NewScale));
1398 NewOps.push_back(Pair.first->first);
1400 Pair.first->second += NewScale;
1401 // The map already had an entry for this value, which may indicate
1402 // a folding opportunity.
1407 // An ordinary operand. Update the map.
1408 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
1409 M.insert(std::make_pair(Ops[i], Scale));
1411 NewOps.push_back(Pair.first->first);
1413 Pair.first->second += Scale;
1414 // The map already had an entry for this value, which may indicate
1415 // a folding opportunity.
1425 struct APIntCompare {
1426 bool operator()(const APInt &LHS, const APInt &RHS) const {
1427 return LHS.ult(RHS);
1432 /// getAddExpr - Get a canonical add expression, or something simpler if
1434 const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1435 SCEV::NoWrapFlags Flags) {
1436 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&
1437 "only nuw or nsw allowed");
1438 assert(!Ops.empty() && "Cannot get empty add!");
1439 if (Ops.size() == 1) return Ops[0];
1441 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1442 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1443 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1444 "SCEVAddExpr operand types don't match!");
1447 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1449 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1450 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1451 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1453 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1454 E = Ops.end(); I != E; ++I)
1455 if (!isKnownNonNegative(*I)) {
1459 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1462 // Sort by complexity, this groups all similar expression types together.
1463 GroupByComplexity(Ops, LI);
1465 // If there are any constants, fold them together.
1467 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1469 assert(Idx < Ops.size());
1470 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1471 // We found two constants, fold them together!
1472 Ops[0] = getConstant(LHSC->getValue()->getValue() +
1473 RHSC->getValue()->getValue());
1474 if (Ops.size() == 2) return Ops[0];
1475 Ops.erase(Ops.begin()+1); // Erase the folded element
1476 LHSC = cast<SCEVConstant>(Ops[0]);
1479 // If we are left with a constant zero being added, strip it off.
1480 if (LHSC->getValue()->isZero()) {
1481 Ops.erase(Ops.begin());
1485 if (Ops.size() == 1) return Ops[0];
1488 // Okay, check to see if the same value occurs in the operand list more than
1489 // once. If so, merge them together into an multiply expression. Since we
1490 // sorted the list, these values are required to be adjacent.
1491 Type *Ty = Ops[0]->getType();
1492 bool FoundMatch = false;
1493 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
1494 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
1495 // Scan ahead to count how many equal operands there are.
1497 while (i+Count != e && Ops[i+Count] == Ops[i])
1499 // Merge the values into a multiply.
1500 const SCEV *Scale = getConstant(Ty, Count);
1501 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
1502 if (Ops.size() == Count)
1505 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
1506 --i; e -= Count - 1;
1510 return getAddExpr(Ops, Flags);
1512 // Check for truncates. If all the operands are truncated from the same
1513 // type, see if factoring out the truncate would permit the result to be
1514 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
1515 // if the contents of the resulting outer trunc fold to something simple.
1516 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
1517 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
1518 Type *DstType = Trunc->getType();
1519 Type *SrcType = Trunc->getOperand()->getType();
1520 SmallVector<const SCEV *, 8> LargeOps;
1522 // Check all the operands to see if they can be represented in the
1523 // source type of the truncate.
1524 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1525 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
1526 if (T->getOperand()->getType() != SrcType) {
1530 LargeOps.push_back(T->getOperand());
1531 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
1532 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
1533 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
1534 SmallVector<const SCEV *, 8> LargeMulOps;
1535 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
1536 if (const SCEVTruncateExpr *T =
1537 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
1538 if (T->getOperand()->getType() != SrcType) {
1542 LargeMulOps.push_back(T->getOperand());
1543 } else if (const SCEVConstant *C =
1544 dyn_cast<SCEVConstant>(M->getOperand(j))) {
1545 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
1552 LargeOps.push_back(getMulExpr(LargeMulOps));
1559 // Evaluate the expression in the larger type.
1560 const SCEV *Fold = getAddExpr(LargeOps, Flags);
1561 // If it folds to something simple, use it. Otherwise, don't.
1562 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
1563 return getTruncateExpr(Fold, DstType);
1567 // Skip past any other cast SCEVs.
1568 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
1571 // If there are add operands they would be next.
1572 if (Idx < Ops.size()) {
1573 bool DeletedAdd = false;
1574 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
1575 // If we have an add, expand the add operands onto the end of the operands
1577 Ops.erase(Ops.begin()+Idx);
1578 Ops.append(Add->op_begin(), Add->op_end());
1582 // If we deleted at least one add, we added operands to the end of the list,
1583 // and they are not necessarily sorted. Recurse to resort and resimplify
1584 // any operands we just acquired.
1586 return getAddExpr(Ops);
1589 // Skip over the add expression until we get to a multiply.
1590 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1593 // Check to see if there are any folding opportunities present with
1594 // operands multiplied by constant values.
1595 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
1596 uint64_t BitWidth = getTypeSizeInBits(Ty);
1597 DenseMap<const SCEV *, APInt> M;
1598 SmallVector<const SCEV *, 8> NewOps;
1599 APInt AccumulatedConstant(BitWidth, 0);
1600 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
1601 Ops.data(), Ops.size(),
1602 APInt(BitWidth, 1), *this)) {
1603 // Some interesting folding opportunity is present, so its worthwhile to
1604 // re-generate the operands list. Group the operands by constant scale,
1605 // to avoid multiplying by the same constant scale multiple times.
1606 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
1607 for (SmallVector<const SCEV *, 8>::const_iterator I = NewOps.begin(),
1608 E = NewOps.end(); I != E; ++I)
1609 MulOpLists[M.find(*I)->second].push_back(*I);
1610 // Re-generate the operands list.
1612 if (AccumulatedConstant != 0)
1613 Ops.push_back(getConstant(AccumulatedConstant));
1614 for (std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare>::iterator
1615 I = MulOpLists.begin(), E = MulOpLists.end(); I != E; ++I)
1617 Ops.push_back(getMulExpr(getConstant(I->first),
1618 getAddExpr(I->second)));
1620 return getConstant(Ty, 0);
1621 if (Ops.size() == 1)
1623 return getAddExpr(Ops);
1627 // If we are adding something to a multiply expression, make sure the
1628 // something is not already an operand of the multiply. If so, merge it into
1630 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
1631 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
1632 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
1633 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
1634 if (isa<SCEVConstant>(MulOpSCEV))
1636 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
1637 if (MulOpSCEV == Ops[AddOp]) {
1638 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
1639 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
1640 if (Mul->getNumOperands() != 2) {
1641 // If the multiply has more than two operands, we must get the
1643 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1644 Mul->op_begin()+MulOp);
1645 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1646 InnerMul = getMulExpr(MulOps);
1648 const SCEV *One = getConstant(Ty, 1);
1649 const SCEV *AddOne = getAddExpr(One, InnerMul);
1650 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
1651 if (Ops.size() == 2) return OuterMul;
1653 Ops.erase(Ops.begin()+AddOp);
1654 Ops.erase(Ops.begin()+Idx-1);
1656 Ops.erase(Ops.begin()+Idx);
1657 Ops.erase(Ops.begin()+AddOp-1);
1659 Ops.push_back(OuterMul);
1660 return getAddExpr(Ops);
1663 // Check this multiply against other multiplies being added together.
1664 for (unsigned OtherMulIdx = Idx+1;
1665 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
1667 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
1668 // If MulOp occurs in OtherMul, we can fold the two multiplies
1670 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
1671 OMulOp != e; ++OMulOp)
1672 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
1673 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
1674 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
1675 if (Mul->getNumOperands() != 2) {
1676 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
1677 Mul->op_begin()+MulOp);
1678 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
1679 InnerMul1 = getMulExpr(MulOps);
1681 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
1682 if (OtherMul->getNumOperands() != 2) {
1683 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
1684 OtherMul->op_begin()+OMulOp);
1685 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
1686 InnerMul2 = getMulExpr(MulOps);
1688 const SCEV *InnerMulSum = getAddExpr(InnerMul1,InnerMul2);
1689 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
1690 if (Ops.size() == 2) return OuterMul;
1691 Ops.erase(Ops.begin()+Idx);
1692 Ops.erase(Ops.begin()+OtherMulIdx-1);
1693 Ops.push_back(OuterMul);
1694 return getAddExpr(Ops);
1700 // If there are any add recurrences in the operands list, see if any other
1701 // added values are loop invariant. If so, we can fold them into the
1703 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1706 // Scan over all recurrences, trying to fold loop invariants into them.
1707 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1708 // Scan all of the other operands to this add and add them to the vector if
1709 // they are loop invariant w.r.t. the recurrence.
1710 SmallVector<const SCEV *, 8> LIOps;
1711 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1712 const Loop *AddRecLoop = AddRec->getLoop();
1713 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1714 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1715 LIOps.push_back(Ops[i]);
1716 Ops.erase(Ops.begin()+i);
1720 // If we found some loop invariants, fold them into the recurrence.
1721 if (!LIOps.empty()) {
1722 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
1723 LIOps.push_back(AddRec->getStart());
1725 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1727 AddRecOps[0] = getAddExpr(LIOps);
1729 // Build the new addrec. Propagate the NUW and NSW flags if both the
1730 // outer add and the inner addrec are guaranteed to have no overflow.
1731 // Always propagate NW.
1732 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
1733 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
1735 // If all of the other operands were loop invariant, we are done.
1736 if (Ops.size() == 1) return NewRec;
1738 // Otherwise, add the folded AddRec by the non-liv parts.
1739 for (unsigned i = 0;; ++i)
1740 if (Ops[i] == AddRec) {
1744 return getAddExpr(Ops);
1747 // Okay, if there weren't any loop invariants to be folded, check to see if
1748 // there are multiple AddRec's with the same loop induction variable being
1749 // added together. If so, we can fold them.
1750 for (unsigned OtherIdx = Idx+1;
1751 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1753 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1754 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
1755 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
1757 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1759 if (const SCEVAddRecExpr *OtherAddRec =
1760 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1761 if (OtherAddRec->getLoop() == AddRecLoop) {
1762 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
1764 if (i >= AddRecOps.size()) {
1765 AddRecOps.append(OtherAddRec->op_begin()+i,
1766 OtherAddRec->op_end());
1769 AddRecOps[i] = getAddExpr(AddRecOps[i],
1770 OtherAddRec->getOperand(i));
1772 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
1774 // Step size has changed, so we cannot guarantee no self-wraparound.
1775 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
1776 return getAddExpr(Ops);
1779 // Otherwise couldn't fold anything into this recurrence. Move onto the
1783 // Okay, it looks like we really DO need an add expr. Check to see if we
1784 // already have one, otherwise create a new one.
1785 FoldingSetNodeID ID;
1786 ID.AddInteger(scAddExpr);
1787 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1788 ID.AddPointer(Ops[i]);
1791 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1793 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
1794 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
1795 S = new (SCEVAllocator) SCEVAddExpr(ID.Intern(SCEVAllocator),
1797 UniqueSCEVs.InsertNode(S, IP);
1799 S->setNoWrapFlags(Flags);
1803 /// getMulExpr - Get a canonical multiply expression, or something simpler if
1805 const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1806 SCEV::NoWrapFlags Flags) {
1807 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
1808 "only nuw or nsw allowed");
1809 assert(!Ops.empty() && "Cannot get empty mul!");
1810 if (Ops.size() == 1) return Ops[0];
1812 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
1813 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
1814 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
1815 "SCEVMulExpr operand types don't match!");
1818 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
1820 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
1821 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
1822 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
1824 for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
1825 E = Ops.end(); I != E; ++I)
1826 if (!isKnownNonNegative(*I)) {
1830 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
1833 // Sort by complexity, this groups all similar expression types together.
1834 GroupByComplexity(Ops, LI);
1836 // If there are any constants, fold them together.
1838 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
1840 // C1*(C2+V) -> C1*C2 + C1*V
1841 if (Ops.size() == 2)
1842 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
1843 if (Add->getNumOperands() == 2 &&
1844 isa<SCEVConstant>(Add->getOperand(0)))
1845 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
1846 getMulExpr(LHSC, Add->getOperand(1)));
1849 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
1850 // We found two constants, fold them together!
1851 ConstantInt *Fold = ConstantInt::get(getContext(),
1852 LHSC->getValue()->getValue() *
1853 RHSC->getValue()->getValue());
1854 Ops[0] = getConstant(Fold);
1855 Ops.erase(Ops.begin()+1); // Erase the folded element
1856 if (Ops.size() == 1) return Ops[0];
1857 LHSC = cast<SCEVConstant>(Ops[0]);
1860 // If we are left with a constant one being multiplied, strip it off.
1861 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
1862 Ops.erase(Ops.begin());
1864 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
1865 // If we have a multiply of zero, it will always be zero.
1867 } else if (Ops[0]->isAllOnesValue()) {
1868 // If we have a mul by -1 of an add, try distributing the -1 among the
1870 if (Ops.size() == 2) {
1871 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
1872 SmallVector<const SCEV *, 4> NewOps;
1873 bool AnyFolded = false;
1874 for (SCEVAddRecExpr::op_iterator I = Add->op_begin(),
1875 E = Add->op_end(); I != E; ++I) {
1876 const SCEV *Mul = getMulExpr(Ops[0], *I);
1877 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
1878 NewOps.push_back(Mul);
1881 return getAddExpr(NewOps);
1883 else if (const SCEVAddRecExpr *
1884 AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
1885 // Negation preserves a recurrence's no self-wrap property.
1886 SmallVector<const SCEV *, 4> Operands;
1887 for (SCEVAddRecExpr::op_iterator I = AddRec->op_begin(),
1888 E = AddRec->op_end(); I != E; ++I) {
1889 Operands.push_back(getMulExpr(Ops[0], *I));
1891 return getAddRecExpr(Operands, AddRec->getLoop(),
1892 AddRec->getNoWrapFlags(SCEV::FlagNW));
1897 if (Ops.size() == 1)
1901 // Skip over the add expression until we get to a multiply.
1902 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
1905 // If there are mul operands inline them all into this expression.
1906 if (Idx < Ops.size()) {
1907 bool DeletedMul = false;
1908 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
1909 // If we have an mul, expand the mul operands onto the end of the operands
1911 Ops.erase(Ops.begin()+Idx);
1912 Ops.append(Mul->op_begin(), Mul->op_end());
1916 // If we deleted at least one mul, we added operands to the end of the list,
1917 // and they are not necessarily sorted. Recurse to resort and resimplify
1918 // any operands we just acquired.
1920 return getMulExpr(Ops);
1923 // If there are any add recurrences in the operands list, see if any other
1924 // added values are loop invariant. If so, we can fold them into the
1926 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
1929 // Scan over all recurrences, trying to fold loop invariants into them.
1930 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
1931 // Scan all of the other operands to this mul and add them to the vector if
1932 // they are loop invariant w.r.t. the recurrence.
1933 SmallVector<const SCEV *, 8> LIOps;
1934 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
1935 const Loop *AddRecLoop = AddRec->getLoop();
1936 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1937 if (isLoopInvariant(Ops[i], AddRecLoop)) {
1938 LIOps.push_back(Ops[i]);
1939 Ops.erase(Ops.begin()+i);
1943 // If we found some loop invariants, fold them into the recurrence.
1944 if (!LIOps.empty()) {
1945 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
1946 SmallVector<const SCEV *, 4> NewOps;
1947 NewOps.reserve(AddRec->getNumOperands());
1948 const SCEV *Scale = getMulExpr(LIOps);
1949 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
1950 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
1952 // Build the new addrec. Propagate the NUW and NSW flags if both the
1953 // outer mul and the inner addrec are guaranteed to have no overflow.
1955 // No self-wrap cannot be guaranteed after changing the step size, but
1956 // will be inferred if either NUW or NSW is true.
1957 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
1958 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
1960 // If all of the other operands were loop invariant, we are done.
1961 if (Ops.size() == 1) return NewRec;
1963 // Otherwise, multiply the folded AddRec by the non-liv parts.
1964 for (unsigned i = 0;; ++i)
1965 if (Ops[i] == AddRec) {
1969 return getMulExpr(Ops);
1972 // Okay, if there weren't any loop invariants to be folded, check to see if
1973 // there are multiple AddRec's with the same loop induction variable being
1974 // multiplied together. If so, we can fold them.
1975 for (unsigned OtherIdx = Idx+1;
1976 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1978 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
1979 // F * G, where F = {A,+,B}<L> and G = {C,+,D}<L> -->
1980 // {A*C,+,F*D + G*B + B*D}<L>
1981 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
1983 if (const SCEVAddRecExpr *OtherAddRec =
1984 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
1985 if (OtherAddRec->getLoop() == AddRecLoop) {
1986 const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
1987 const SCEV *NewStart = getMulExpr(F->getStart(), G->getStart());
1988 const SCEV *B = F->getStepRecurrence(*this);
1989 const SCEV *D = G->getStepRecurrence(*this);
1990 const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
1993 const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
1996 if (Ops.size() == 2) return NewAddRec;
1997 Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
1998 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2000 return getMulExpr(Ops);
2003 // Otherwise couldn't fold anything into this recurrence. Move onto the
2007 // Okay, it looks like we really DO need an mul expr. Check to see if we
2008 // already have one, otherwise create a new one.
2009 FoldingSetNodeID ID;
2010 ID.AddInteger(scMulExpr);
2011 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2012 ID.AddPointer(Ops[i]);
2015 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2017 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2018 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2019 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2021 UniqueSCEVs.InsertNode(S, IP);
2023 S->setNoWrapFlags(Flags);
2027 /// getUDivExpr - Get a canonical unsigned division expression, or something
2028 /// simpler if possible.
2029 const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2031 assert(getEffectiveSCEVType(LHS->getType()) ==
2032 getEffectiveSCEVType(RHS->getType()) &&
2033 "SCEVUDivExpr operand types don't match!");
2035 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2036 if (RHSC->getValue()->equalsInt(1))
2037 return LHS; // X udiv 1 --> x
2038 // If the denominator is zero, the result of the udiv is undefined. Don't
2039 // try to analyze it, because the resolution chosen here may differ from
2040 // the resolution chosen in other parts of the compiler.
2041 if (!RHSC->getValue()->isZero()) {
2042 // Determine if the division can be folded into the operands of
2044 // TODO: Generalize this to non-constants by using known-bits information.
2045 Type *Ty = LHS->getType();
2046 unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
2047 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2048 // For non-power-of-two values, effectively round the value up to the
2049 // nearest power of two.
2050 if (!RHSC->getValue()->getValue().isPowerOf2())
2052 IntegerType *ExtTy =
2053 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2054 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2055 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2056 if (const SCEVConstant *Step =
2057 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
2058 if (!Step->getValue()->getValue()
2059 .urem(RHSC->getValue()->getValue()) &&
2060 getZeroExtendExpr(AR, ExtTy) ==
2061 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2062 getZeroExtendExpr(Step, ExtTy),
2063 AR->getLoop(), SCEV::FlagAnyWrap)) {
2064 SmallVector<const SCEV *, 4> Operands;
2065 for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
2066 Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
2067 return getAddRecExpr(Operands, AR->getLoop(),
2070 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2071 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2072 SmallVector<const SCEV *, 4> Operands;
2073 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
2074 Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
2075 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2076 // Find an operand that's safely divisible.
2077 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2078 const SCEV *Op = M->getOperand(i);
2079 const SCEV *Div = getUDivExpr(Op, RHSC);
2080 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2081 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2084 return getMulExpr(Operands);
2088 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2089 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2090 SmallVector<const SCEV *, 4> Operands;
2091 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
2092 Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
2093 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2095 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2096 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2097 if (isa<SCEVUDivExpr>(Op) ||
2098 getMulExpr(Op, RHS) != A->getOperand(i))
2100 Operands.push_back(Op);
2102 if (Operands.size() == A->getNumOperands())
2103 return getAddExpr(Operands);
2107 // Fold if both operands are constant.
2108 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2109 Constant *LHSCV = LHSC->getValue();
2110 Constant *RHSCV = RHSC->getValue();
2111 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2117 FoldingSetNodeID ID;
2118 ID.AddInteger(scUDivExpr);
2122 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2123 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2125 UniqueSCEVs.InsertNode(S, IP);
2130 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2131 /// Simplify the expression as much as possible.
2132 const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2134 SCEV::NoWrapFlags Flags) {
2135 SmallVector<const SCEV *, 4> Operands;
2136 Operands.push_back(Start);
2137 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2138 if (StepChrec->getLoop() == L) {
2139 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2140 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2143 Operands.push_back(Step);
2144 return getAddRecExpr(Operands, L, Flags);
2147 /// getAddRecExpr - Get an add recurrence expression for the specified loop.
2148 /// Simplify the expression as much as possible.
2150 ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2151 const Loop *L, SCEV::NoWrapFlags Flags) {
2152 if (Operands.size() == 1) return Operands[0];
2154 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2155 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2156 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
2157 "SCEVAddRecExpr operand types don't match!");
2158 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2159 assert(isLoopInvariant(Operands[i], L) &&
2160 "SCEVAddRecExpr operand is not loop-invariant!");
2163 if (Operands.back()->isZero()) {
2164 Operands.pop_back();
2165 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
2168 // It's tempting to want to call getMaxBackedgeTakenCount count here and
2169 // use that information to infer NUW and NSW flags. However, computing a
2170 // BE count requires calling getAddRecExpr, so we may not yet have a
2171 // meaningful BE count at this point (and if we don't, we'd be stuck
2172 // with a SCEVCouldNotCompute as the cached BE count).
2174 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2176 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2177 SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
2178 if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
2180 for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
2181 E = Operands.end(); I != E; ++I)
2182 if (!isKnownNonNegative(*I)) {
2186 if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2189 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
2190 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
2191 const Loop *NestedLoop = NestedAR->getLoop();
2192 if (L->contains(NestedLoop) ?
2193 (L->getLoopDepth() < NestedLoop->getLoopDepth()) :
2194 (!NestedLoop->contains(L) &&
2195 DT->dominates(L->getHeader(), NestedLoop->getHeader()))) {
2196 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
2197 NestedAR->op_end());
2198 Operands[0] = NestedAR->getStart();
2199 // AddRecs require their operands be loop-invariant with respect to their
2200 // loops. Don't perform this transformation if it would break this
2202 bool AllInvariant = true;
2203 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2204 if (!isLoopInvariant(Operands[i], L)) {
2205 AllInvariant = false;
2209 // Create a recurrence for the outer loop with the same step size.
2211 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
2212 // inner recurrence has the same property.
2213 SCEV::NoWrapFlags OuterFlags =
2214 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
2216 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
2217 AllInvariant = true;
2218 for (unsigned i = 0, e = NestedOperands.size(); i != e; ++i)
2219 if (!isLoopInvariant(NestedOperands[i], NestedLoop)) {
2220 AllInvariant = false;
2224 // Ok, both add recurrences are valid after the transformation.
2226 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
2227 // the outer recurrence has the same property.
2228 SCEV::NoWrapFlags InnerFlags =
2229 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
2230 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
2233 // Reset Operands to its original state.
2234 Operands[0] = NestedAR;
2238 // Okay, it looks like we really DO need an addrec expr. Check to see if we
2239 // already have one, otherwise create a new one.
2240 FoldingSetNodeID ID;
2241 ID.AddInteger(scAddRecExpr);
2242 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
2243 ID.AddPointer(Operands[i]);
2247 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2249 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
2250 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
2251 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
2252 O, Operands.size(), L);
2253 UniqueSCEVs.InsertNode(S, IP);
2255 S->setNoWrapFlags(Flags);
2259 const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
2261 SmallVector<const SCEV *, 2> Ops;
2264 return getSMaxExpr(Ops);
2268 ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2269 assert(!Ops.empty() && "Cannot get empty smax!");
2270 if (Ops.size() == 1) return Ops[0];
2272 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2273 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2274 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2275 "SCEVSMaxExpr operand types don't match!");
2278 // Sort by complexity, this groups all similar expression types together.
2279 GroupByComplexity(Ops, LI);
2281 // If there are any constants, fold them together.
2283 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2285 assert(Idx < Ops.size());
2286 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2287 // We found two constants, fold them together!
2288 ConstantInt *Fold = ConstantInt::get(getContext(),
2289 APIntOps::smax(LHSC->getValue()->getValue(),
2290 RHSC->getValue()->getValue()));
2291 Ops[0] = getConstant(Fold);
2292 Ops.erase(Ops.begin()+1); // Erase the folded element
2293 if (Ops.size() == 1) return Ops[0];
2294 LHSC = cast<SCEVConstant>(Ops[0]);
2297 // If we are left with a constant minimum-int, strip it off.
2298 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
2299 Ops.erase(Ops.begin());
2301 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
2302 // If we have an smax with a constant maximum-int, it will always be
2307 if (Ops.size() == 1) return Ops[0];
2310 // Find the first SMax
2311 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
2314 // Check to see if one of the operands is an SMax. If so, expand its operands
2315 // onto our operand list, and recurse to simplify.
2316 if (Idx < Ops.size()) {
2317 bool DeletedSMax = false;
2318 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
2319 Ops.erase(Ops.begin()+Idx);
2320 Ops.append(SMax->op_begin(), SMax->op_end());
2325 return getSMaxExpr(Ops);
2328 // Okay, check to see if the same value occurs in the operand list twice. If
2329 // so, delete one. Since we sorted the list, these values are required to
2331 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2332 // X smax Y smax Y --> X smax Y
2333 // X smax Y --> X, if X is always greater than Y
2334 if (Ops[i] == Ops[i+1] ||
2335 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
2336 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2338 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
2339 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2343 if (Ops.size() == 1) return Ops[0];
2345 assert(!Ops.empty() && "Reduced smax down to nothing!");
2347 // Okay, it looks like we really DO need an smax expr. Check to see if we
2348 // already have one, otherwise create a new one.
2349 FoldingSetNodeID ID;
2350 ID.AddInteger(scSMaxExpr);
2351 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2352 ID.AddPointer(Ops[i]);
2354 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2355 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2356 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2357 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
2359 UniqueSCEVs.InsertNode(S, IP);
2363 const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
2365 SmallVector<const SCEV *, 2> Ops;
2368 return getUMaxExpr(Ops);
2372 ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
2373 assert(!Ops.empty() && "Cannot get empty umax!");
2374 if (Ops.size() == 1) return Ops[0];
2376 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2377 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2378 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
2379 "SCEVUMaxExpr operand types don't match!");
2382 // Sort by complexity, this groups all similar expression types together.
2383 GroupByComplexity(Ops, LI);
2385 // If there are any constants, fold them together.
2387 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2389 assert(Idx < Ops.size());
2390 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2391 // We found two constants, fold them together!
2392 ConstantInt *Fold = ConstantInt::get(getContext(),
2393 APIntOps::umax(LHSC->getValue()->getValue(),
2394 RHSC->getValue()->getValue()));
2395 Ops[0] = getConstant(Fold);
2396 Ops.erase(Ops.begin()+1); // Erase the folded element
2397 if (Ops.size() == 1) return Ops[0];
2398 LHSC = cast<SCEVConstant>(Ops[0]);
2401 // If we are left with a constant minimum-int, strip it off.
2402 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
2403 Ops.erase(Ops.begin());
2405 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
2406 // If we have an umax with a constant maximum-int, it will always be
2411 if (Ops.size() == 1) return Ops[0];
2414 // Find the first UMax
2415 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
2418 // Check to see if one of the operands is a UMax. If so, expand its operands
2419 // onto our operand list, and recurse to simplify.
2420 if (Idx < Ops.size()) {
2421 bool DeletedUMax = false;
2422 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
2423 Ops.erase(Ops.begin()+Idx);
2424 Ops.append(UMax->op_begin(), UMax->op_end());
2429 return getUMaxExpr(Ops);
2432 // Okay, check to see if the same value occurs in the operand list twice. If
2433 // so, delete one. Since we sorted the list, these values are required to
2435 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
2436 // X umax Y umax Y --> X umax Y
2437 // X umax Y --> X, if X is always greater than Y
2438 if (Ops[i] == Ops[i+1] ||
2439 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
2440 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
2442 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
2443 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
2447 if (Ops.size() == 1) return Ops[0];
2449 assert(!Ops.empty() && "Reduced umax down to nothing!");
2451 // Okay, it looks like we really DO need a umax expr. Check to see if we
2452 // already have one, otherwise create a new one.
2453 FoldingSetNodeID ID;
2454 ID.AddInteger(scUMaxExpr);
2455 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2456 ID.AddPointer(Ops[i]);
2458 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2459 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2460 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2461 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
2463 UniqueSCEVs.InsertNode(S, IP);
2467 const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
2469 // ~smax(~x, ~y) == smin(x, y).
2470 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2473 const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
2475 // ~umax(~x, ~y) == umin(x, y)
2476 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
2479 const SCEV *ScalarEvolution::getSizeOfExpr(Type *AllocTy) {
2480 // If we have TargetData, we can bypass creating a target-independent
2481 // constant expression and then folding it back into a ConstantInt.
2482 // This is just a compile-time optimization.
2484 return getConstant(TD->getIntPtrType(getContext()),
2485 TD->getTypeAllocSize(AllocTy));
2487 Constant *C = ConstantExpr::getSizeOf(AllocTy);
2488 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2489 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2491 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2492 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2495 const SCEV *ScalarEvolution::getAlignOfExpr(Type *AllocTy) {
2496 Constant *C = ConstantExpr::getAlignOf(AllocTy);
2497 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2498 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2500 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(AllocTy));
2501 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2504 const SCEV *ScalarEvolution::getOffsetOfExpr(StructType *STy,
2506 // If we have TargetData, we can bypass creating a target-independent
2507 // constant expression and then folding it back into a ConstantInt.
2508 // This is just a compile-time optimization.
2510 return getConstant(TD->getIntPtrType(getContext()),
2511 TD->getStructLayout(STy)->getElementOffset(FieldNo));
2513 Constant *C = ConstantExpr::getOffsetOf(STy, FieldNo);
2514 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2515 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2517 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(STy));
2518 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2521 const SCEV *ScalarEvolution::getOffsetOfExpr(Type *CTy,
2522 Constant *FieldNo) {
2523 Constant *C = ConstantExpr::getOffsetOf(CTy, FieldNo);
2524 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2525 if (Constant *Folded = ConstantFoldConstantExpression(CE, TD))
2527 Type *Ty = getEffectiveSCEVType(PointerType::getUnqual(CTy));
2528 return getTruncateOrZeroExtend(getSCEV(C), Ty);
2531 const SCEV *ScalarEvolution::getUnknown(Value *V) {
2532 // Don't attempt to do anything other than create a SCEVUnknown object
2533 // here. createSCEV only calls getUnknown after checking for all other
2534 // interesting possibilities, and any other code that calls getUnknown
2535 // is doing so in order to hide a value from SCEV canonicalization.
2537 FoldingSetNodeID ID;
2538 ID.AddInteger(scUnknown);
2541 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
2542 assert(cast<SCEVUnknown>(S)->getValue() == V &&
2543 "Stale SCEVUnknown in uniquing map!");
2546 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
2548 FirstUnknown = cast<SCEVUnknown>(S);
2549 UniqueSCEVs.InsertNode(S, IP);
2553 //===----------------------------------------------------------------------===//
2554 // Basic SCEV Analysis and PHI Idiom Recognition Code
2557 /// isSCEVable - Test if values of the given type are analyzable within
2558 /// the SCEV framework. This primarily includes integer types, and it
2559 /// can optionally include pointer types if the ScalarEvolution class
2560 /// has access to target-specific information.
2561 bool ScalarEvolution::isSCEVable(Type *Ty) const {
2562 // Integers and pointers are always SCEVable.
2563 return Ty->isIntegerTy() || Ty->isPointerTy();
2566 /// getTypeSizeInBits - Return the size in bits of the specified type,
2567 /// for which isSCEVable must return true.
2568 uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
2569 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2571 // If we have a TargetData, use it!
2573 return TD->getTypeSizeInBits(Ty);
2575 // Integer types have fixed sizes.
2576 if (Ty->isIntegerTy())
2577 return Ty->getPrimitiveSizeInBits();
2579 // The only other support type is pointer. Without TargetData, conservatively
2580 // assume pointers are 64-bit.
2581 assert(Ty->isPointerTy() && "isSCEVable permitted a non-SCEVable type!");
2585 /// getEffectiveSCEVType - Return a type with the same bitwidth as
2586 /// the given type and which represents how SCEV will treat the given
2587 /// type, for which isSCEVable must return true. For pointer types,
2588 /// this is the pointer-sized integer type.
2589 Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
2590 assert(isSCEVable(Ty) && "Type is not SCEVable!");
2592 if (Ty->isIntegerTy())
2595 // The only other support type is pointer.
2596 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!");
2597 if (TD) return TD->getIntPtrType(getContext());
2599 // Without TargetData, conservatively assume pointers are 64-bit.
2600 return Type::getInt64Ty(getContext());
2603 const SCEV *ScalarEvolution::getCouldNotCompute() {
2604 return &CouldNotCompute;
2607 /// getSCEV - Return an existing SCEV if it exists, otherwise analyze the
2608 /// expression and create a new one.
2609 const SCEV *ScalarEvolution::getSCEV(Value *V) {
2610 assert(isSCEVable(V->getType()) && "Value is not SCEVable!");
2612 ValueExprMapType::const_iterator I = ValueExprMap.find(V);
2613 if (I != ValueExprMap.end()) return I->second;
2614 const SCEV *S = createSCEV(V);
2616 // The process of creating a SCEV for V may have caused other SCEVs
2617 // to have been created, so it's necessary to insert the new entry
2618 // from scratch, rather than trying to remember the insert position
2620 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(V, this), S));
2624 /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V
2626 const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V) {
2627 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2629 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
2631 Type *Ty = V->getType();
2632 Ty = getEffectiveSCEVType(Ty);
2633 return getMulExpr(V,
2634 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))));
2637 /// getNotSCEV - Return a SCEV corresponding to ~V = -1-V
2638 const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
2639 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
2641 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
2643 Type *Ty = V->getType();
2644 Ty = getEffectiveSCEVType(Ty);
2645 const SCEV *AllOnes =
2646 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
2647 return getMinusSCEV(AllOnes, V);
2650 /// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
2651 const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
2652 SCEV::NoWrapFlags Flags) {
2653 assert(!maskFlags(Flags, SCEV::FlagNUW) && "subtraction does not have NUW");
2655 // Fast path: X - X --> 0.
2657 return getConstant(LHS->getType(), 0);
2660 return getAddExpr(LHS, getNegativeSCEV(RHS), Flags);
2663 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the
2664 /// input value to the specified type. If the type must be extended, it is zero
2667 ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
2668 Type *SrcTy = V->getType();
2669 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2670 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2671 "Cannot truncate or zero extend with non-integer arguments!");
2672 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2673 return V; // No conversion
2674 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2675 return getTruncateExpr(V, Ty);
2676 return getZeroExtendExpr(V, Ty);
2679 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion of the
2680 /// input value to the specified type. If the type must be extended, it is sign
2683 ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
2685 Type *SrcTy = V->getType();
2686 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2687 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2688 "Cannot truncate or zero extend with non-integer arguments!");
2689 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2690 return V; // No conversion
2691 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
2692 return getTruncateExpr(V, Ty);
2693 return getSignExtendExpr(V, Ty);
2696 /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of the
2697 /// input value to the specified type. If the type must be extended, it is zero
2698 /// extended. The conversion must not be narrowing.
2700 ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
2701 Type *SrcTy = V->getType();
2702 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2703 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2704 "Cannot noop or zero extend with non-integer arguments!");
2705 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2706 "getNoopOrZeroExtend cannot truncate!");
2707 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2708 return V; // No conversion
2709 return getZeroExtendExpr(V, Ty);
2712 /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of the
2713 /// input value to the specified type. If the type must be extended, it is sign
2714 /// extended. The conversion must not be narrowing.
2716 ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
2717 Type *SrcTy = V->getType();
2718 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2719 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2720 "Cannot noop or sign extend with non-integer arguments!");
2721 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2722 "getNoopOrSignExtend cannot truncate!");
2723 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2724 return V; // No conversion
2725 return getSignExtendExpr(V, Ty);
2728 /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
2729 /// the input value to the specified type. If the type must be extended,
2730 /// it is extended with unspecified bits. The conversion must not be
2733 ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
2734 Type *SrcTy = V->getType();
2735 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2736 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2737 "Cannot noop or any extend with non-integer arguments!");
2738 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
2739 "getNoopOrAnyExtend cannot truncate!");
2740 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2741 return V; // No conversion
2742 return getAnyExtendExpr(V, Ty);
2745 /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
2746 /// input value to the specified type. The conversion must not be widening.
2748 ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
2749 Type *SrcTy = V->getType();
2750 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
2751 (Ty->isIntegerTy() || Ty->isPointerTy()) &&
2752 "Cannot truncate or noop with non-integer arguments!");
2753 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
2754 "getTruncateOrNoop cannot extend!");
2755 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
2756 return V; // No conversion
2757 return getTruncateExpr(V, Ty);
2760 /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
2761 /// the types using zero-extension, and then perform a umax operation
2763 const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
2765 const SCEV *PromotedLHS = LHS;
2766 const SCEV *PromotedRHS = RHS;
2768 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2769 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2771 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2773 return getUMaxExpr(PromotedLHS, PromotedRHS);
2776 /// getUMinFromMismatchedTypes - Promote the operands to the wider of
2777 /// the types using zero-extension, and then perform a umin operation
2779 const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
2781 const SCEV *PromotedLHS = LHS;
2782 const SCEV *PromotedRHS = RHS;
2784 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
2785 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
2787 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
2789 return getUMinExpr(PromotedLHS, PromotedRHS);
2792 /// getPointerBase - Transitively follow the chain of pointer-type operands
2793 /// until reaching a SCEV that does not have a single pointer operand. This
2794 /// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
2795 /// but corner cases do exist.
2796 const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
2797 // A pointer operand may evaluate to a nonpointer expression, such as null.
2798 if (!V->getType()->isPointerTy())
2801 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
2802 return getPointerBase(Cast->getOperand());
2804 else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
2805 const SCEV *PtrOp = 0;
2806 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
2808 if ((*I)->getType()->isPointerTy()) {
2809 // Cannot find the base of an expression with multiple pointer operands.
2817 return getPointerBase(PtrOp);
2822 /// PushDefUseChildren - Push users of the given Instruction
2823 /// onto the given Worklist.
2825 PushDefUseChildren(Instruction *I,
2826 SmallVectorImpl<Instruction *> &Worklist) {
2827 // Push the def-use children onto the Worklist stack.
2828 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
2830 Worklist.push_back(cast<Instruction>(*UI));
2833 /// ForgetSymbolicValue - This looks up computed SCEV values for all
2834 /// instructions that depend on the given instruction and removes them from
2835 /// the ValueExprMapType map if they reference SymName. This is used during PHI
2838 ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
2839 SmallVector<Instruction *, 16> Worklist;
2840 PushDefUseChildren(PN, Worklist);
2842 SmallPtrSet<Instruction *, 8> Visited;
2844 while (!Worklist.empty()) {
2845 Instruction *I = Worklist.pop_back_val();
2846 if (!Visited.insert(I)) continue;
2848 ValueExprMapType::iterator It =
2849 ValueExprMap.find(static_cast<Value *>(I));
2850 if (It != ValueExprMap.end()) {
2851 const SCEV *Old = It->second;
2853 // Short-circuit the def-use traversal if the symbolic name
2854 // ceases to appear in expressions.
2855 if (Old != SymName && !hasOperand(Old, SymName))
2858 // SCEVUnknown for a PHI either means that it has an unrecognized
2859 // structure, it's a PHI that's in the progress of being computed
2860 // by createNodeForPHI, or it's a single-value PHI. In the first case,
2861 // additional loop trip count information isn't going to change anything.
2862 // In the second case, createNodeForPHI will perform the necessary
2863 // updates on its own when it gets to that point. In the third, we do
2864 // want to forget the SCEVUnknown.
2865 if (!isa<PHINode>(I) ||
2866 !isa<SCEVUnknown>(Old) ||
2867 (I != PN && Old == SymName)) {
2868 forgetMemoizedResults(Old);
2869 ValueExprMap.erase(It);
2873 PushDefUseChildren(I, Worklist);
2877 /// createNodeForPHI - PHI nodes have two cases. Either the PHI node exists in
2878 /// a loop header, making it a potential recurrence, or it doesn't.
2880 const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
2881 if (const Loop *L = LI->getLoopFor(PN->getParent()))
2882 if (L->getHeader() == PN->getParent()) {
2883 // The loop may have multiple entrances or multiple exits; we can analyze
2884 // this phi as an addrec if it has a unique entry value and a unique
2886 Value *BEValueV = 0, *StartValueV = 0;
2887 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2888 Value *V = PN->getIncomingValue(i);
2889 if (L->contains(PN->getIncomingBlock(i))) {
2892 } else if (BEValueV != V) {
2896 } else if (!StartValueV) {
2898 } else if (StartValueV != V) {
2903 if (BEValueV && StartValueV) {
2904 // While we are analyzing this PHI node, handle its value symbolically.
2905 const SCEV *SymbolicName = getUnknown(PN);
2906 assert(ValueExprMap.find(PN) == ValueExprMap.end() &&
2907 "PHI node already processed?");
2908 ValueExprMap.insert(std::make_pair(SCEVCallbackVH(PN, this), SymbolicName));
2910 // Using this symbolic name for the PHI, analyze the value coming around
2912 const SCEV *BEValue = getSCEV(BEValueV);
2914 // NOTE: If BEValue is loop invariant, we know that the PHI node just
2915 // has a special value for the first iteration of the loop.
2917 // If the value coming around the backedge is an add with the symbolic
2918 // value we just inserted, then we found a simple induction variable!
2919 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
2920 // If there is a single occurrence of the symbolic value, replace it
2921 // with a recurrence.
2922 unsigned FoundIndex = Add->getNumOperands();
2923 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2924 if (Add->getOperand(i) == SymbolicName)
2925 if (FoundIndex == e) {
2930 if (FoundIndex != Add->getNumOperands()) {
2931 // Create an add with everything but the specified operand.
2932 SmallVector<const SCEV *, 8> Ops;
2933 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
2934 if (i != FoundIndex)
2935 Ops.push_back(Add->getOperand(i));
2936 const SCEV *Accum = getAddExpr(Ops);
2938 // This is not a valid addrec if the step amount is varying each
2939 // loop iteration, but is not itself an addrec in this loop.
2940 if (isLoopInvariant(Accum, L) ||
2941 (isa<SCEVAddRecExpr>(Accum) &&
2942 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
2943 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
2945 // If the increment doesn't overflow, then neither the addrec nor
2946 // the post-increment will overflow.
2947 if (const AddOperator *OBO = dyn_cast<AddOperator>(BEValueV)) {
2948 if (OBO->hasNoUnsignedWrap())
2949 Flags = setFlags(Flags, SCEV::FlagNUW);
2950 if (OBO->hasNoSignedWrap())
2951 Flags = setFlags(Flags, SCEV::FlagNSW);
2952 } else if (const GEPOperator *GEP =
2953 dyn_cast<GEPOperator>(BEValueV)) {
2954 // If the increment is an inbounds GEP, then we know the address
2955 // space cannot be wrapped around. We cannot make any guarantee
2956 // about signed or unsigned overflow because pointers are
2957 // unsigned but we may have a negative index from the base
2959 if (GEP->isInBounds())
2960 Flags = setFlags(Flags, SCEV::FlagNW);
2963 const SCEV *StartVal = getSCEV(StartValueV);
2964 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
2966 // Since the no-wrap flags are on the increment, they apply to the
2967 // post-incremented value as well.
2968 if (isLoopInvariant(Accum, L))
2969 (void)getAddRecExpr(getAddExpr(StartVal, Accum),
2972 // Okay, for the entire analysis of this edge we assumed the PHI
2973 // to be symbolic. We now need to go back and purge all of the
2974 // entries for the scalars that use the symbolic expression.
2975 ForgetSymbolicName(PN, SymbolicName);
2976 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
2980 } else if (const SCEVAddRecExpr *AddRec =
2981 dyn_cast<SCEVAddRecExpr>(BEValue)) {
2982 // Otherwise, this could be a loop like this:
2983 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
2984 // In this case, j = {1,+,1} and BEValue is j.
2985 // Because the other in-value of i (0) fits the evolution of BEValue
2986 // i really is an addrec evolution.
2987 if (AddRec->getLoop() == L && AddRec->isAffine()) {
2988 const SCEV *StartVal = getSCEV(StartValueV);
2990 // If StartVal = j.start - j.stride, we can use StartVal as the
2991 // initial step of the addrec evolution.
2992 if (StartVal == getMinusSCEV(AddRec->getOperand(0),
2993 AddRec->getOperand(1))) {
2994 // FIXME: For constant StartVal, we should be able to infer
2996 const SCEV *PHISCEV =
2997 getAddRecExpr(StartVal, AddRec->getOperand(1), L,
3000 // Okay, for the entire analysis of this edge we assumed the PHI
3001 // to be symbolic. We now need to go back and purge all of the
3002 // entries for the scalars that use the symbolic expression.
3003 ForgetSymbolicName(PN, SymbolicName);
3004 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
3012 // If the PHI has a single incoming value, follow that value, unless the
3013 // PHI's incoming blocks are in a different loop, in which case doing so
3014 // risks breaking LCSSA form. Instcombine would normally zap these, but
3015 // it doesn't have DominatorTree information, so it may miss cases.
3016 if (Value *V = SimplifyInstruction(PN, TD, DT))
3017 if (LI->replacementPreservesLCSSAForm(PN, V))
3020 // If it's not a loop phi, we can't handle it yet.
3021 return getUnknown(PN);
3024 /// createNodeForGEP - Expand GEP instructions into add and multiply
3025 /// operations. This allows them to be analyzed by regular SCEV code.
3027 const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
3029 // Don't blindly transfer the inbounds flag from the GEP instruction to the
3030 // Add expression, because the Instruction may be guarded by control flow
3031 // and the no-overflow bits may not be valid for the expression in any
3033 bool isInBounds = GEP->isInBounds();
3035 Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
3036 Value *Base = GEP->getOperand(0);
3037 // Don't attempt to analyze GEPs over unsized objects.
3038 if (!cast<PointerType>(Base->getType())->getElementType()->isSized())
3039 return getUnknown(GEP);
3040 const SCEV *TotalOffset = getConstant(IntPtrTy, 0);
3041 gep_type_iterator GTI = gep_type_begin(GEP);
3042 for (GetElementPtrInst::op_iterator I = llvm::next(GEP->op_begin()),
3046 // Compute the (potentially symbolic) offset in bytes for this index.
3047 if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
3048 // For a struct, add the member offset.
3049 unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
3050 const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
3052 // Add the field offset to the running total offset.
3053 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3055 // For an array, add the element offset, explicitly scaled.
3056 const SCEV *ElementSize = getSizeOfExpr(*GTI);
3057 const SCEV *IndexS = getSCEV(Index);
3058 // Getelementptr indices are signed.
3059 IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
3061 // Multiply the index by the element size to compute the element offset.
3062 const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize,
3063 isInBounds ? SCEV::FlagNSW :
3066 // Add the element offset to the running total offset.
3067 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3071 // Get the SCEV for the GEP base.
3072 const SCEV *BaseS = getSCEV(Base);
3074 // Add the total offset from all the GEP indices to the base.
3075 return getAddExpr(BaseS, TotalOffset,
3076 isInBounds ? SCEV::FlagNSW : SCEV::FlagAnyWrap);
3079 /// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
3080 /// guaranteed to end in (at every loop iteration). It is, at the same time,
3081 /// the minimum number of times S is divisible by 2. For example, given {4,+,8}
3082 /// it returns 2. If S is guaranteed to be 0, it returns the bitwidth of S.
3084 ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
3085 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3086 return C->getValue()->getValue().countTrailingZeros();
3088 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
3089 return std::min(GetMinTrailingZeros(T->getOperand()),
3090 (uint32_t)getTypeSizeInBits(T->getType()));
3092 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
3093 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3094 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3095 getTypeSizeInBits(E->getType()) : OpRes;
3098 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
3099 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
3100 return OpRes == getTypeSizeInBits(E->getOperand()->getType()) ?
3101 getTypeSizeInBits(E->getType()) : OpRes;
3104 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
3105 // The result is the min of all operands results.
3106 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3107 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3108 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3112 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
3113 // The result is the sum of all operands results.
3114 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
3115 uint32_t BitWidth = getTypeSizeInBits(M->getType());
3116 for (unsigned i = 1, e = M->getNumOperands();
3117 SumOpRes != BitWidth && i != e; ++i)
3118 SumOpRes = std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)),
3123 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
3124 // The result is the min of all operands results.
3125 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
3126 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
3127 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
3131 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
3132 // The result is the min of all operands results.
3133 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3134 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3135 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3139 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
3140 // The result is the min of all operands results.
3141 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
3142 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
3143 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
3147 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3148 // For a SCEVUnknown, ask ValueTracking.
3149 unsigned BitWidth = getTypeSizeInBits(U->getType());
3150 APInt Mask = APInt::getAllOnesValue(BitWidth);
3151 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3152 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones);
3153 return Zeros.countTrailingOnes();
3160 /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
3163 ScalarEvolution::getUnsignedRange(const SCEV *S) {
3164 // See if we've computed this range already.
3165 DenseMap<const SCEV *, ConstantRange>::iterator I = UnsignedRanges.find(S);
3166 if (I != UnsignedRanges.end())
3169 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3170 return setUnsignedRange(C, ConstantRange(C->getValue()->getValue()));
3172 unsigned BitWidth = getTypeSizeInBits(S->getType());
3173 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3175 // If the value has known zeros, the maximum unsigned value will have those
3176 // known zeros as well.
3177 uint32_t TZ = GetMinTrailingZeros(S);
3179 ConservativeResult =
3180 ConstantRange(APInt::getMinValue(BitWidth),
3181 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
3183 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3184 ConstantRange X = getUnsignedRange(Add->getOperand(0));
3185 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3186 X = X.add(getUnsignedRange(Add->getOperand(i)));
3187 return setUnsignedRange(Add, ConservativeResult.intersectWith(X));
3190 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3191 ConstantRange X = getUnsignedRange(Mul->getOperand(0));
3192 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3193 X = X.multiply(getUnsignedRange(Mul->getOperand(i)));
3194 return setUnsignedRange(Mul, ConservativeResult.intersectWith(X));
3197 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3198 ConstantRange X = getUnsignedRange(SMax->getOperand(0));
3199 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3200 X = X.smax(getUnsignedRange(SMax->getOperand(i)));
3201 return setUnsignedRange(SMax, ConservativeResult.intersectWith(X));
3204 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3205 ConstantRange X = getUnsignedRange(UMax->getOperand(0));
3206 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3207 X = X.umax(getUnsignedRange(UMax->getOperand(i)));
3208 return setUnsignedRange(UMax, ConservativeResult.intersectWith(X));
3211 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3212 ConstantRange X = getUnsignedRange(UDiv->getLHS());
3213 ConstantRange Y = getUnsignedRange(UDiv->getRHS());
3214 return setUnsignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3217 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3218 ConstantRange X = getUnsignedRange(ZExt->getOperand());
3219 return setUnsignedRange(ZExt,
3220 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3223 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3224 ConstantRange X = getUnsignedRange(SExt->getOperand());
3225 return setUnsignedRange(SExt,
3226 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3229 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3230 ConstantRange X = getUnsignedRange(Trunc->getOperand());
3231 return setUnsignedRange(Trunc,
3232 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3235 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3236 // If there's no unsigned wrap, the value will never be less than its
3238 if (AddRec->getNoWrapFlags(SCEV::FlagNUW))
3239 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
3240 if (!C->getValue()->isZero())
3241 ConservativeResult =
3242 ConservativeResult.intersectWith(
3243 ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
3245 // TODO: non-affine addrec
3246 if (AddRec->isAffine()) {
3247 Type *Ty = AddRec->getType();
3248 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3249 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3250 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3251 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3253 const SCEV *Start = AddRec->getStart();
3254 const SCEV *Step = AddRec->getStepRecurrence(*this);
3256 ConstantRange StartRange = getUnsignedRange(Start);
3257 ConstantRange StepRange = getSignedRange(Step);
3258 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3259 ConstantRange EndRange =
3260 StartRange.add(MaxBECountRange.multiply(StepRange));
3262 // Check for overflow. This must be done with ConstantRange arithmetic
3263 // because we could be called from within the ScalarEvolution overflow
3265 ConstantRange ExtStartRange = StartRange.zextOrTrunc(BitWidth*2+1);
3266 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3267 ConstantRange ExtMaxBECountRange =
3268 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3269 ConstantRange ExtEndRange = EndRange.zextOrTrunc(BitWidth*2+1);
3270 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3272 return setUnsignedRange(AddRec, ConservativeResult);
3274 APInt Min = APIntOps::umin(StartRange.getUnsignedMin(),
3275 EndRange.getUnsignedMin());
3276 APInt Max = APIntOps::umax(StartRange.getUnsignedMax(),
3277 EndRange.getUnsignedMax());
3278 if (Min.isMinValue() && Max.isMaxValue())
3279 return setUnsignedRange(AddRec, ConservativeResult);
3280 return setUnsignedRange(AddRec,
3281 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3285 return setUnsignedRange(AddRec, ConservativeResult);
3288 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3289 // For a SCEVUnknown, ask ValueTracking.
3290 APInt Mask = APInt::getAllOnesValue(BitWidth);
3291 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
3292 ComputeMaskedBits(U->getValue(), Mask, Zeros, Ones, TD);
3293 if (Ones == ~Zeros + 1)
3294 return setUnsignedRange(U, ConservativeResult);
3295 return setUnsignedRange(U,
3296 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1)));
3299 return setUnsignedRange(S, ConservativeResult);
3302 /// getSignedRange - Determine the signed range for a particular SCEV.
3305 ScalarEvolution::getSignedRange(const SCEV *S) {
3306 // See if we've computed this range already.
3307 DenseMap<const SCEV *, ConstantRange>::iterator I = SignedRanges.find(S);
3308 if (I != SignedRanges.end())
3311 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
3312 return setSignedRange(C, ConstantRange(C->getValue()->getValue()));
3314 unsigned BitWidth = getTypeSizeInBits(S->getType());
3315 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
3317 // If the value has known zeros, the maximum signed value will have those
3318 // known zeros as well.
3319 uint32_t TZ = GetMinTrailingZeros(S);
3321 ConservativeResult =
3322 ConstantRange(APInt::getSignedMinValue(BitWidth),
3323 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
3325 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3326 ConstantRange X = getSignedRange(Add->getOperand(0));
3327 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
3328 X = X.add(getSignedRange(Add->getOperand(i)));
3329 return setSignedRange(Add, ConservativeResult.intersectWith(X));
3332 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3333 ConstantRange X = getSignedRange(Mul->getOperand(0));
3334 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
3335 X = X.multiply(getSignedRange(Mul->getOperand(i)));
3336 return setSignedRange(Mul, ConservativeResult.intersectWith(X));
3339 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
3340 ConstantRange X = getSignedRange(SMax->getOperand(0));
3341 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
3342 X = X.smax(getSignedRange(SMax->getOperand(i)));
3343 return setSignedRange(SMax, ConservativeResult.intersectWith(X));
3346 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
3347 ConstantRange X = getSignedRange(UMax->getOperand(0));
3348 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
3349 X = X.umax(getSignedRange(UMax->getOperand(i)));
3350 return setSignedRange(UMax, ConservativeResult.intersectWith(X));
3353 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
3354 ConstantRange X = getSignedRange(UDiv->getLHS());
3355 ConstantRange Y = getSignedRange(UDiv->getRHS());
3356 return setSignedRange(UDiv, ConservativeResult.intersectWith(X.udiv(Y)));
3359 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
3360 ConstantRange X = getSignedRange(ZExt->getOperand());
3361 return setSignedRange(ZExt,
3362 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
3365 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
3366 ConstantRange X = getSignedRange(SExt->getOperand());
3367 return setSignedRange(SExt,
3368 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
3371 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
3372 ConstantRange X = getSignedRange(Trunc->getOperand());
3373 return setSignedRange(Trunc,
3374 ConservativeResult.intersectWith(X.truncate(BitWidth)));
3377 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
3378 // If there's no signed wrap, and all the operands have the same sign or
3379 // zero, the value won't ever change sign.
3380 if (AddRec->getNoWrapFlags(SCEV::FlagNSW)) {
3381 bool AllNonNeg = true;
3382 bool AllNonPos = true;
3383 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
3384 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
3385 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
3388 ConservativeResult = ConservativeResult.intersectWith(
3389 ConstantRange(APInt(BitWidth, 0),
3390 APInt::getSignedMinValue(BitWidth)));
3392 ConservativeResult = ConservativeResult.intersectWith(
3393 ConstantRange(APInt::getSignedMinValue(BitWidth),
3394 APInt(BitWidth, 1)));
3397 // TODO: non-affine addrec
3398 if (AddRec->isAffine()) {
3399 Type *Ty = AddRec->getType();
3400 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
3401 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
3402 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
3403 MaxBECount = getNoopOrZeroExtend(MaxBECount, Ty);
3405 const SCEV *Start = AddRec->getStart();
3406 const SCEV *Step = AddRec->getStepRecurrence(*this);
3408 ConstantRange StartRange = getSignedRange(Start);
3409 ConstantRange StepRange = getSignedRange(Step);
3410 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
3411 ConstantRange EndRange =
3412 StartRange.add(MaxBECountRange.multiply(StepRange));
3414 // Check for overflow. This must be done with ConstantRange arithmetic
3415 // because we could be called from within the ScalarEvolution overflow
3417 ConstantRange ExtStartRange = StartRange.sextOrTrunc(BitWidth*2+1);
3418 ConstantRange ExtStepRange = StepRange.sextOrTrunc(BitWidth*2+1);
3419 ConstantRange ExtMaxBECountRange =
3420 MaxBECountRange.zextOrTrunc(BitWidth*2+1);
3421 ConstantRange ExtEndRange = EndRange.sextOrTrunc(BitWidth*2+1);
3422 if (ExtStartRange.add(ExtMaxBECountRange.multiply(ExtStepRange)) !=
3424 return setSignedRange(AddRec, ConservativeResult);
3426 APInt Min = APIntOps::smin(StartRange.getSignedMin(),
3427 EndRange.getSignedMin());
3428 APInt Max = APIntOps::smax(StartRange.getSignedMax(),
3429 EndRange.getSignedMax());
3430 if (Min.isMinSignedValue() && Max.isMaxSignedValue())
3431 return setSignedRange(AddRec, ConservativeResult);
3432 return setSignedRange(AddRec,
3433 ConservativeResult.intersectWith(ConstantRange(Min, Max+1)));
3437 return setSignedRange(AddRec, ConservativeResult);
3440 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
3441 // For a SCEVUnknown, ask ValueTracking.
3442 if (!U->getValue()->getType()->isIntegerTy() && !TD)
3443 return setSignedRange(U, ConservativeResult);
3444 unsigned NS = ComputeNumSignBits(U->getValue(), TD);
3446 return setSignedRange(U, ConservativeResult);
3447 return setSignedRange(U, ConservativeResult.intersectWith(
3448 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
3449 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1)+1)));
3452 return setSignedRange(S, ConservativeResult);
3455 /// createSCEV - We know that there is no SCEV for the specified value.
3456 /// Analyze the expression.
3458 const SCEV *ScalarEvolution::createSCEV(Value *V) {
3459 if (!isSCEVable(V->getType()))
3460 return getUnknown(V);
3462 unsigned Opcode = Instruction::UserOp1;
3463 if (Instruction *I = dyn_cast<Instruction>(V)) {
3464 Opcode = I->getOpcode();
3466 // Don't attempt to analyze instructions in blocks that aren't
3467 // reachable. Such instructions don't matter, and they aren't required
3468 // to obey basic rules for definitions dominating uses which this
3469 // analysis depends on.
3470 if (!DT->isReachableFromEntry(I->getParent()))
3471 return getUnknown(V);
3472 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
3473 Opcode = CE->getOpcode();
3474 else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
3475 return getConstant(CI);
3476 else if (isa<ConstantPointerNull>(V))
3477 return getConstant(V->getType(), 0);
3478 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
3479 return GA->mayBeOverridden() ? getUnknown(V) : getSCEV(GA->getAliasee());
3481 return getUnknown(V);
3483 Operator *U = cast<Operator>(V);
3485 case Instruction::Add: {
3486 // The simple thing to do would be to just call getSCEV on both operands
3487 // and call getAddExpr with the result. However if we're looking at a
3488 // bunch of things all added together, this can be quite inefficient,
3489 // because it leads to N-1 getAddExpr calls for N ultimate operands.
3490 // Instead, gather up all the operands and make a single getAddExpr call.
3491 // LLVM IR canonical form means we need only traverse the left operands.
3492 SmallVector<const SCEV *, 4> AddOps;
3493 AddOps.push_back(getSCEV(U->getOperand(1)));
3494 for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) {
3495 unsigned Opcode = Op->getValueID() - Value::InstructionVal;
3496 if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
3498 U = cast<Operator>(Op);
3499 const SCEV *Op1 = getSCEV(U->getOperand(1));
3500 if (Opcode == Instruction::Sub)
3501 AddOps.push_back(getNegativeSCEV(Op1));
3503 AddOps.push_back(Op1);
3505 AddOps.push_back(getSCEV(U->getOperand(0)));
3506 return getAddExpr(AddOps);
3508 case Instruction::Mul: {
3509 // See the Add code above.
3510 SmallVector<const SCEV *, 4> MulOps;
3511 MulOps.push_back(getSCEV(U->getOperand(1)));
3512 for (Value *Op = U->getOperand(0);
3513 Op->getValueID() == Instruction::Mul + Value::InstructionVal;
3514 Op = U->getOperand(0)) {
3515 U = cast<Operator>(Op);
3516 MulOps.push_back(getSCEV(U->getOperand(1)));
3518 MulOps.push_back(getSCEV(U->getOperand(0)));
3519 return getMulExpr(MulOps);
3521 case Instruction::UDiv:
3522 return getUDivExpr(getSCEV(U->getOperand(0)),
3523 getSCEV(U->getOperand(1)));
3524 case Instruction::Sub:
3525 return getMinusSCEV(getSCEV(U->getOperand(0)),
3526 getSCEV(U->getOperand(1)));
3527 case Instruction::And:
3528 // For an expression like x&255 that merely masks off the high bits,
3529 // use zext(trunc(x)) as the SCEV expression.
3530 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3531 if (CI->isNullValue())
3532 return getSCEV(U->getOperand(1));
3533 if (CI->isAllOnesValue())
3534 return getSCEV(U->getOperand(0));
3535 const APInt &A = CI->getValue();
3537 // Instcombine's ShrinkDemandedConstant may strip bits out of
3538 // constants, obscuring what would otherwise be a low-bits mask.
3539 // Use ComputeMaskedBits to compute what ShrinkDemandedConstant
3540 // knew about to reconstruct a low-bits mask value.
3541 unsigned LZ = A.countLeadingZeros();
3542 unsigned BitWidth = A.getBitWidth();
3543 APInt AllOnes = APInt::getAllOnesValue(BitWidth);
3544 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3545 ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD);
3547 APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ);
3549 if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask))
3551 getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)),
3552 IntegerType::get(getContext(), BitWidth - LZ)),
3557 case Instruction::Or:
3558 // If the RHS of the Or is a constant, we may have something like:
3559 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
3560 // optimizations will transparently handle this case.
3562 // In order for this transformation to be safe, the LHS must be of the
3563 // form X*(2^n) and the Or constant must be less than 2^n.
3564 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3565 const SCEV *LHS = getSCEV(U->getOperand(0));
3566 const APInt &CIVal = CI->getValue();
3567 if (GetMinTrailingZeros(LHS) >=
3568 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
3569 // Build a plain add SCEV.
3570 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
3571 // If the LHS of the add was an addrec and it has no-wrap flags,
3572 // transfer the no-wrap flags, since an or won't introduce a wrap.
3573 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
3574 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
3575 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
3576 OldAR->getNoWrapFlags());
3582 case Instruction::Xor:
3583 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
3584 // If the RHS of the xor is a signbit, then this is just an add.
3585 // Instcombine turns add of signbit into xor as a strength reduction step.
3586 if (CI->getValue().isSignBit())
3587 return getAddExpr(getSCEV(U->getOperand(0)),
3588 getSCEV(U->getOperand(1)));
3590 // If the RHS of xor is -1, then this is a not operation.
3591 if (CI->isAllOnesValue())
3592 return getNotSCEV(getSCEV(U->getOperand(0)));
3594 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
3595 // This is a variant of the check for xor with -1, and it handles
3596 // the case where instcombine has trimmed non-demanded bits out
3597 // of an xor with -1.
3598 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U->getOperand(0)))
3599 if (ConstantInt *LCI = dyn_cast<ConstantInt>(BO->getOperand(1)))
3600 if (BO->getOpcode() == Instruction::And &&
3601 LCI->getValue() == CI->getValue())
3602 if (const SCEVZeroExtendExpr *Z =
3603 dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) {
3604 Type *UTy = U->getType();
3605 const SCEV *Z0 = Z->getOperand();
3606 Type *Z0Ty = Z0->getType();
3607 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
3609 // If C is a low-bits mask, the zero extend is serving to
3610 // mask off the high bits. Complement the operand and
3611 // re-apply the zext.
3612 if (APIntOps::isMask(Z0TySize, CI->getValue()))
3613 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
3615 // If C is a single bit, it may be in the sign-bit position
3616 // before the zero-extend. In this case, represent the xor
3617 // using an add, which is equivalent, and re-apply the zext.
3618 APInt Trunc = CI->getValue().trunc(Z0TySize);
3619 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
3621 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
3627 case Instruction::Shl:
3628 // Turn shift left of a constant amount into a multiply.
3629 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3630 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3632 // If the shift count is not less than the bitwidth, the result of
3633 // the shift is undefined. Don't try to analyze it, because the
3634 // resolution chosen here may differ from the resolution chosen in
3635 // other parts of the compiler.
3636 if (SA->getValue().uge(BitWidth))
3639 Constant *X = ConstantInt::get(getContext(),
3640 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3641 return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3645 case Instruction::LShr:
3646 // Turn logical shift right of a constant into a unsigned divide.
3647 if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
3648 uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
3650 // If the shift count is not less than the bitwidth, the result of
3651 // the shift is undefined. Don't try to analyze it, because the
3652 // resolution chosen here may differ from the resolution chosen in
3653 // other parts of the compiler.
3654 if (SA->getValue().uge(BitWidth))
3657 Constant *X = ConstantInt::get(getContext(),
3658 APInt(BitWidth, 1).shl(SA->getZExtValue()));
3659 return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
3663 case Instruction::AShr:
3664 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
3665 if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
3666 if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
3667 if (L->getOpcode() == Instruction::Shl &&
3668 L->getOperand(1) == U->getOperand(1)) {
3669 uint64_t BitWidth = getTypeSizeInBits(U->getType());
3671 // If the shift count is not less than the bitwidth, the result of
3672 // the shift is undefined. Don't try to analyze it, because the
3673 // resolution chosen here may differ from the resolution chosen in
3674 // other parts of the compiler.
3675 if (CI->getValue().uge(BitWidth))
3678 uint64_t Amt = BitWidth - CI->getZExtValue();
3679 if (Amt == BitWidth)
3680 return getSCEV(L->getOperand(0)); // shift by zero --> noop
3682 getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
3683 IntegerType::get(getContext(),
3689 case Instruction::Trunc:
3690 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
3692 case Instruction::ZExt:
3693 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3695 case Instruction::SExt:
3696 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
3698 case Instruction::BitCast:
3699 // BitCasts are no-op casts so we just eliminate the cast.
3700 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
3701 return getSCEV(U->getOperand(0));
3704 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
3705 // lead to pointer expressions which cannot safely be expanded to GEPs,
3706 // because ScalarEvolution doesn't respect the GEP aliasing rules when
3707 // simplifying integer expressions.
3709 case Instruction::GetElementPtr:
3710 return createNodeForGEP(cast<GEPOperator>(U));
3712 case Instruction::PHI:
3713 return createNodeForPHI(cast<PHINode>(U));
3715 case Instruction::Select:
3716 // This could be a smax or umax that was lowered earlier.
3717 // Try to recover it.
3718 if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
3719 Value *LHS = ICI->getOperand(0);
3720 Value *RHS = ICI->getOperand(1);
3721 switch (ICI->getPredicate()) {
3722 case ICmpInst::ICMP_SLT:
3723 case ICmpInst::ICMP_SLE:
3724 std::swap(LHS, RHS);
3726 case ICmpInst::ICMP_SGT:
3727 case ICmpInst::ICMP_SGE:
3728 // a >s b ? a+x : b+x -> smax(a, b)+x
3729 // a >s b ? b+x : a+x -> smin(a, b)+x
3730 if (LHS->getType() == U->getType()) {
3731 const SCEV *LS = getSCEV(LHS);
3732 const SCEV *RS = getSCEV(RHS);
3733 const SCEV *LA = getSCEV(U->getOperand(1));
3734 const SCEV *RA = getSCEV(U->getOperand(2));
3735 const SCEV *LDiff = getMinusSCEV(LA, LS);
3736 const SCEV *RDiff = getMinusSCEV(RA, RS);
3738 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
3739 LDiff = getMinusSCEV(LA, RS);
3740 RDiff = getMinusSCEV(RA, LS);
3742 return getAddExpr(getSMinExpr(LS, RS), LDiff);
3745 case ICmpInst::ICMP_ULT:
3746 case ICmpInst::ICMP_ULE:
3747 std::swap(LHS, RHS);
3749 case ICmpInst::ICMP_UGT:
3750 case ICmpInst::ICMP_UGE:
3751 // a >u b ? a+x : b+x -> umax(a, b)+x
3752 // a >u b ? b+x : a+x -> umin(a, b)+x
3753 if (LHS->getType() == U->getType()) {
3754 const SCEV *LS = getSCEV(LHS);
3755 const SCEV *RS = getSCEV(RHS);
3756 const SCEV *LA = getSCEV(U->getOperand(1));
3757 const SCEV *RA = getSCEV(U->getOperand(2));
3758 const SCEV *LDiff = getMinusSCEV(LA, LS);
3759 const SCEV *RDiff = getMinusSCEV(RA, RS);
3761 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
3762 LDiff = getMinusSCEV(LA, RS);
3763 RDiff = getMinusSCEV(RA, LS);
3765 return getAddExpr(getUMinExpr(LS, RS), LDiff);
3768 case ICmpInst::ICMP_NE:
3769 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
3770 if (LHS->getType() == U->getType() &&
3771 isa<ConstantInt>(RHS) &&
3772 cast<ConstantInt>(RHS)->isZero()) {
3773 const SCEV *One = getConstant(LHS->getType(), 1);
3774 const SCEV *LS = getSCEV(LHS);
3775 const SCEV *LA = getSCEV(U->getOperand(1));
3776 const SCEV *RA = getSCEV(U->getOperand(2));
3777 const SCEV *LDiff = getMinusSCEV(LA, LS);
3778 const SCEV *RDiff = getMinusSCEV(RA, One);
3780 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3783 case ICmpInst::ICMP_EQ:
3784 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
3785 if (LHS->getType() == U->getType() &&
3786 isa<ConstantInt>(RHS) &&
3787 cast<ConstantInt>(RHS)->isZero()) {
3788 const SCEV *One = getConstant(LHS->getType(), 1);
3789 const SCEV *LS = getSCEV(LHS);
3790 const SCEV *LA = getSCEV(U->getOperand(1));
3791 const SCEV *RA = getSCEV(U->getOperand(2));
3792 const SCEV *LDiff = getMinusSCEV(LA, One);
3793 const SCEV *RDiff = getMinusSCEV(RA, LS);
3795 return getAddExpr(getUMaxExpr(One, LS), LDiff);
3803 default: // We cannot analyze this expression.
3807 return getUnknown(V);
3812 //===----------------------------------------------------------------------===//
3813 // Iteration Count Computation Code
3816 // getExitCount - Get the expression for the number of loop iterations for which
3817 // this loop is guaranteed not to exit via ExitBlock. Otherwise return
3818 // SCEVCouldNotCompute.
3819 const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitBlock) {
3820 return getBackedgeTakenInfo(L).getExact(ExitBlock, this);
3823 /// getBackedgeTakenCount - If the specified loop has a predictable
3824 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
3825 /// object. The backedge-taken count is the number of times the loop header
3826 /// will be branched to from within the loop. This is one less than the
3827 /// trip count of the loop, since it doesn't count the first iteration,
3828 /// when the header is branched to from outside the loop.
3830 /// Note that it is not valid to call this method on a loop without a
3831 /// loop-invariant backedge-taken count (see
3832 /// hasLoopInvariantBackedgeTakenCount).
3834 const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
3835 return getBackedgeTakenInfo(L).getExact(this);
3838 /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
3839 /// return the least SCEV value that is known never to be less than the
3840 /// actual backedge taken count.
3841 const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
3842 return getBackedgeTakenInfo(L).getMax(this);
3845 /// PushLoopPHIs - Push PHI nodes in the header of the given loop
3846 /// onto the given Worklist.
3848 PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
3849 BasicBlock *Header = L->getHeader();
3851 // Push all Loop-header PHIs onto the Worklist stack.
3852 for (BasicBlock::iterator I = Header->begin();
3853 PHINode *PN = dyn_cast<PHINode>(I); ++I)
3854 Worklist.push_back(PN);
3857 const ScalarEvolution::BackedgeTakenInfo &
3858 ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
3859 // Initially insert an invalid entry for this loop. If the insertion
3860 // succeeds, proceed to actually compute a backedge-taken count and
3861 // update the value. The temporary CouldNotCompute value tells SCEV
3862 // code elsewhere that it shouldn't attempt to request a new
3863 // backedge-taken count, which could result in infinite recursion.
3864 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
3865 BackedgeTakenCounts.insert(std::make_pair(L, BackedgeTakenInfo()));
3867 return Pair.first->second;
3869 // ComputeBackedgeTakenCount may allocate memory for its result. Inserting it
3870 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
3871 // must be cleared in this scope.
3872 BackedgeTakenInfo Result = ComputeBackedgeTakenCount(L);
3874 if (Result.getExact(this) != getCouldNotCompute()) {
3875 assert(isLoopInvariant(Result.getExact(this), L) &&
3876 isLoopInvariant(Result.getMax(this), L) &&
3877 "Computed backedge-taken count isn't loop invariant for loop!");
3878 ++NumTripCountsComputed;
3880 else if (Result.getMax(this) == getCouldNotCompute() &&
3881 isa<PHINode>(L->getHeader()->begin())) {
3882 // Only count loops that have phi nodes as not being computable.
3883 ++NumTripCountsNotComputed;
3886 // Now that we know more about the trip count for this loop, forget any
3887 // existing SCEV values for PHI nodes in this loop since they are only
3888 // conservative estimates made without the benefit of trip count
3889 // information. This is similar to the code in forgetLoop, except that
3890 // it handles SCEVUnknown PHI nodes specially.
3891 if (Result.hasAnyInfo()) {
3892 SmallVector<Instruction *, 16> Worklist;
3893 PushLoopPHIs(L, Worklist);
3895 SmallPtrSet<Instruction *, 8> Visited;
3896 while (!Worklist.empty()) {
3897 Instruction *I = Worklist.pop_back_val();
3898 if (!Visited.insert(I)) continue;
3900 ValueExprMapType::iterator It =
3901 ValueExprMap.find(static_cast<Value *>(I));
3902 if (It != ValueExprMap.end()) {
3903 const SCEV *Old = It->second;
3905 // SCEVUnknown for a PHI either means that it has an unrecognized
3906 // structure, or it's a PHI that's in the progress of being computed
3907 // by createNodeForPHI. In the former case, additional loop trip
3908 // count information isn't going to change anything. In the later
3909 // case, createNodeForPHI will perform the necessary updates on its
3910 // own when it gets to that point.
3911 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
3912 forgetMemoizedResults(Old);
3913 ValueExprMap.erase(It);
3915 if (PHINode *PN = dyn_cast<PHINode>(I))
3916 ConstantEvolutionLoopExitValue.erase(PN);
3919 PushDefUseChildren(I, Worklist);
3923 // Re-lookup the insert position, since the call to
3924 // ComputeBackedgeTakenCount above could result in a
3925 // recusive call to getBackedgeTakenInfo (on a different
3926 // loop), which would invalidate the iterator computed
3928 return BackedgeTakenCounts.find(L)->second = Result;
3931 /// forgetLoop - This method should be called by the client when it has
3932 /// changed a loop in a way that may effect ScalarEvolution's ability to
3933 /// compute a trip count, or if the loop is deleted.
3934 void ScalarEvolution::forgetLoop(const Loop *L) {
3935 // Drop any stored trip count value.
3936 DenseMap<const Loop*, BackedgeTakenInfo>::iterator BTCPos =
3937 BackedgeTakenCounts.find(L);
3938 if (BTCPos != BackedgeTakenCounts.end()) {
3939 BTCPos->second.clear();
3940 BackedgeTakenCounts.erase(BTCPos);
3943 // Drop information about expressions based on loop-header PHIs.
3944 SmallVector<Instruction *, 16> Worklist;
3945 PushLoopPHIs(L, Worklist);
3947 SmallPtrSet<Instruction *, 8> Visited;
3948 while (!Worklist.empty()) {
3949 Instruction *I = Worklist.pop_back_val();
3950 if (!Visited.insert(I)) continue;
3952 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3953 if (It != ValueExprMap.end()) {
3954 forgetMemoizedResults(It->second);
3955 ValueExprMap.erase(It);
3956 if (PHINode *PN = dyn_cast<PHINode>(I))
3957 ConstantEvolutionLoopExitValue.erase(PN);
3960 PushDefUseChildren(I, Worklist);
3963 // Forget all contained loops too, to avoid dangling entries in the
3964 // ValuesAtScopes map.
3965 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
3969 /// forgetValue - This method should be called by the client when it has
3970 /// changed a value in a way that may effect its value, or which may
3971 /// disconnect it from a def-use chain linking it to a loop.
3972 void ScalarEvolution::forgetValue(Value *V) {
3973 Instruction *I = dyn_cast<Instruction>(V);
3976 // Drop information about expressions based on loop-header PHIs.
3977 SmallVector<Instruction *, 16> Worklist;
3978 Worklist.push_back(I);
3980 SmallPtrSet<Instruction *, 8> Visited;
3981 while (!Worklist.empty()) {
3982 I = Worklist.pop_back_val();
3983 if (!Visited.insert(I)) continue;
3985 ValueExprMapType::iterator It = ValueExprMap.find(static_cast<Value *>(I));
3986 if (It != ValueExprMap.end()) {
3987 forgetMemoizedResults(It->second);
3988 ValueExprMap.erase(It);
3989 if (PHINode *PN = dyn_cast<PHINode>(I))
3990 ConstantEvolutionLoopExitValue.erase(PN);
3993 PushDefUseChildren(I, Worklist);
3997 /// getExact - Get the exact loop backedge taken count considering all loop
3998 /// exits. If all exits are computable, this is the minimum computed count.
4000 ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE) const {
4001 // If any exits were not computable, the loop is not computable.
4002 if (!ExitNotTaken.isCompleteList()) return SE->getCouldNotCompute();
4004 // We need at least one computable exit.
4005 if (!ExitNotTaken.ExitBlock) return SE->getCouldNotCompute();
4006 assert(ExitNotTaken.ExactNotTaken && "uninitialized not-taken info");
4008 const SCEV *BECount = 0;
4009 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4010 ENT != 0; ENT = ENT->getNextExit()) {
4012 assert(ENT->ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV");
4015 BECount = ENT->ExactNotTaken;
4017 BECount = SE->getUMinFromMismatchedTypes(BECount, ENT->ExactNotTaken);
4022 /// getExact - Get the exact not taken count for this loop exit.
4024 ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitBlock,
4025 ScalarEvolution *SE) const {
4026 for (const ExitNotTakenInfo *ENT = &ExitNotTaken;
4027 ENT != 0; ENT = ENT->getNextExit()) {
4029 if (ENT->ExitBlock == ExitBlock)
4030 return ENT->ExactNotTaken;
4032 return SE->getCouldNotCompute();
4035 /// getMax - Get the max backedge taken count for the loop.
4037 ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
4038 return Max ? Max : SE->getCouldNotCompute();
4041 /// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
4042 /// computable exit into a persistent ExitNotTakenInfo array.
4043 ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
4044 SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
4045 bool Complete, const SCEV *MaxCount) : Max(MaxCount) {
4048 ExitNotTaken.setIncomplete();
4050 unsigned NumExits = ExitCounts.size();
4051 if (NumExits == 0) return;
4053 ExitNotTaken.ExitBlock = ExitCounts[0].first;
4054 ExitNotTaken.ExactNotTaken = ExitCounts[0].second;
4055 if (NumExits == 1) return;
4057 // Handle the rare case of multiple computable exits.
4058 ExitNotTakenInfo *ENT = new ExitNotTakenInfo[NumExits-1];
4060 ExitNotTakenInfo *PrevENT = &ExitNotTaken;
4061 for (unsigned i = 1; i < NumExits; ++i, PrevENT = ENT, ++ENT) {
4062 PrevENT->setNextExit(ENT);
4063 ENT->ExitBlock = ExitCounts[i].first;
4064 ENT->ExactNotTaken = ExitCounts[i].second;
4068 /// clear - Invalidate this result and free the ExitNotTakenInfo array.
4069 void ScalarEvolution::BackedgeTakenInfo::clear() {
4070 ExitNotTaken.ExitBlock = 0;
4071 ExitNotTaken.ExactNotTaken = 0;
4072 delete[] ExitNotTaken.getNextExit();
4075 /// ComputeBackedgeTakenCount - Compute the number of times the backedge
4076 /// of the specified loop will execute.
4077 ScalarEvolution::BackedgeTakenInfo
4078 ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
4079 SmallVector<BasicBlock *, 8> ExitingBlocks;
4080 L->getExitingBlocks(ExitingBlocks);
4082 // Examine all exits and pick the most conservative values.
4083 const SCEV *MaxBECount = getCouldNotCompute();
4084 bool CouldComputeBECount = true;
4085 SmallVector<std::pair<BasicBlock *, const SCEV *>, 4> ExitCounts;
4086 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
4087 ExitLimit EL = ComputeExitLimit(L, ExitingBlocks[i]);
4088 if (EL.Exact == getCouldNotCompute())
4089 // We couldn't compute an exact value for this exit, so
4090 // we won't be able to compute an exact value for the loop.
4091 CouldComputeBECount = false;
4093 ExitCounts.push_back(std::make_pair(ExitingBlocks[i], EL.Exact));
4095 if (MaxBECount == getCouldNotCompute())
4096 MaxBECount = EL.Max;
4097 else if (EL.Max != getCouldNotCompute())
4098 MaxBECount = getUMinFromMismatchedTypes(MaxBECount, EL.Max);
4101 return BackedgeTakenInfo(ExitCounts, CouldComputeBECount, MaxBECount);
4104 /// ComputeExitLimit - Compute the number of times the backedge of the specified
4105 /// loop will execute if it exits via the specified block.
4106 ScalarEvolution::ExitLimit
4107 ScalarEvolution::ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock) {
4109 // Okay, we've chosen an exiting block. See what condition causes us to
4110 // exit at this block.
4112 // FIXME: we should be able to handle switch instructions (with a single exit)
4113 BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
4114 if (ExitBr == 0) return getCouldNotCompute();
4115 assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
4117 // At this point, we know we have a conditional branch that determines whether
4118 // the loop is exited. However, we don't know if the branch is executed each
4119 // time through the loop. If not, then the execution count of the branch will
4120 // not be equal to the trip count of the loop.
4122 // Currently we check for this by checking to see if the Exit branch goes to
4123 // the loop header. If so, we know it will always execute the same number of
4124 // times as the loop. We also handle the case where the exit block *is* the
4125 // loop header. This is common for un-rotated loops.
4127 // If both of those tests fail, walk up the unique predecessor chain to the
4128 // header, stopping if there is an edge that doesn't exit the loop. If the
4129 // header is reached, the execution count of the branch will be equal to the
4130 // trip count of the loop.
4132 // More extensive analysis could be done to handle more cases here.
4134 if (ExitBr->getSuccessor(0) != L->getHeader() &&
4135 ExitBr->getSuccessor(1) != L->getHeader() &&
4136 ExitBr->getParent() != L->getHeader()) {
4137 // The simple checks failed, try climbing the unique predecessor chain
4138 // up to the header.
4140 for (BasicBlock *BB = ExitBr->getParent(); BB; ) {
4141 BasicBlock *Pred = BB->getUniquePredecessor();
4143 return getCouldNotCompute();
4144 TerminatorInst *PredTerm = Pred->getTerminator();
4145 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i) {
4146 BasicBlock *PredSucc = PredTerm->getSuccessor(i);
4149 // If the predecessor has a successor that isn't BB and isn't
4150 // outside the loop, assume the worst.
4151 if (L->contains(PredSucc))
4152 return getCouldNotCompute();
4154 if (Pred == L->getHeader()) {
4161 return getCouldNotCompute();
4164 // Proceed to the next level to examine the exit condition expression.
4165 return ComputeExitLimitFromCond(L, ExitBr->getCondition(),
4166 ExitBr->getSuccessor(0),
4167 ExitBr->getSuccessor(1));
4170 /// ComputeExitLimitFromCond - Compute the number of times the
4171 /// backedge of the specified loop will execute if its exit condition
4172 /// were a conditional branch of ExitCond, TBB, and FBB.
4173 ScalarEvolution::ExitLimit
4174 ScalarEvolution::ComputeExitLimitFromCond(const Loop *L,
4178 // Check if the controlling expression for this loop is an And or Or.
4179 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
4180 if (BO->getOpcode() == Instruction::And) {
4181 // Recurse on the operands of the and.
4182 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB);
4183 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB);
4184 const SCEV *BECount = getCouldNotCompute();
4185 const SCEV *MaxBECount = getCouldNotCompute();
4186 if (L->contains(TBB)) {
4187 // Both conditions must be true for the loop to continue executing.
4188 // Choose the less conservative count.
4189 if (EL0.Exact == getCouldNotCompute() ||
4190 EL1.Exact == getCouldNotCompute())
4191 BECount = getCouldNotCompute();
4193 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4194 if (EL0.Max == getCouldNotCompute())
4195 MaxBECount = EL1.Max;
4196 else if (EL1.Max == getCouldNotCompute())
4197 MaxBECount = EL0.Max;
4199 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4201 // Both conditions must be true at the same time for the loop to exit.
4202 // For now, be conservative.
4203 assert(L->contains(FBB) && "Loop block has no successor in loop!");
4204 if (EL0.Max == EL1.Max)
4205 MaxBECount = EL0.Max;
4206 if (EL0.Exact == EL1.Exact)
4207 BECount = EL0.Exact;
4210 return ExitLimit(BECount, MaxBECount);
4212 if (BO->getOpcode() == Instruction::Or) {
4213 // Recurse on the operands of the or.
4214 ExitLimit EL0 = ComputeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB);
4215 ExitLimit EL1 = ComputeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB);
4216 const SCEV *BECount = getCouldNotCompute();
4217 const SCEV *MaxBECount = getCouldNotCompute();
4218 if (L->contains(FBB)) {
4219 // Both conditions must be false for the loop to continue executing.
4220 // Choose the less conservative count.
4221 if (EL0.Exact == getCouldNotCompute() ||
4222 EL1.Exact == getCouldNotCompute())
4223 BECount = getCouldNotCompute();
4225 BECount = getUMinFromMismatchedTypes(EL0.Exact, EL1.Exact);
4226 if (EL0.Max == getCouldNotCompute())
4227 MaxBECount = EL1.Max;
4228 else if (EL1.Max == getCouldNotCompute())
4229 MaxBECount = EL0.Max;
4231 MaxBECount = getUMinFromMismatchedTypes(EL0.Max, EL1.Max);
4233 // Both conditions must be false at the same time for the loop to exit.
4234 // For now, be conservative.
4235 assert(L->contains(TBB) && "Loop block has no successor in loop!");
4236 if (EL0.Max == EL1.Max)
4237 MaxBECount = EL0.Max;
4238 if (EL0.Exact == EL1.Exact)
4239 BECount = EL0.Exact;
4242 return ExitLimit(BECount, MaxBECount);
4246 // With an icmp, it may be feasible to compute an exact backedge-taken count.
4247 // Proceed to the next level to examine the icmp.
4248 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
4249 return ComputeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB);
4251 // Check for a constant condition. These are normally stripped out by
4252 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
4253 // preserve the CFG and is temporarily leaving constant conditions
4255 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
4256 if (L->contains(FBB) == !CI->getZExtValue())
4257 // The backedge is always taken.
4258 return getCouldNotCompute();
4260 // The backedge is never taken.
4261 return getConstant(CI->getType(), 0);
4264 // If it's not an integer or pointer comparison then compute it the hard way.
4265 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
4268 /// ComputeExitLimitFromICmp - Compute the number of times the
4269 /// backedge of the specified loop will execute if its exit condition
4270 /// were a conditional branch of the ICmpInst ExitCond, TBB, and FBB.
4271 ScalarEvolution::ExitLimit
4272 ScalarEvolution::ComputeExitLimitFromICmp(const Loop *L,
4277 // If the condition was exit on true, convert the condition to exit on false
4278 ICmpInst::Predicate Cond;
4279 if (!L->contains(FBB))
4280 Cond = ExitCond->getPredicate();
4282 Cond = ExitCond->getInversePredicate();
4284 // Handle common loops like: for (X = "string"; *X; ++X)
4285 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
4286 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
4288 ComputeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
4289 if (ItCnt.hasAnyInfo())
4293 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
4294 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
4296 // Try to evaluate any dependencies out of the loop.
4297 LHS = getSCEVAtScope(LHS, L);
4298 RHS = getSCEVAtScope(RHS, L);
4300 // At this point, we would like to compute how many iterations of the
4301 // loop the predicate will return true for these inputs.
4302 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
4303 // If there is a loop-invariant, force it into the RHS.
4304 std::swap(LHS, RHS);
4305 Cond = ICmpInst::getSwappedPredicate(Cond);
4308 // Simplify the operands before analyzing them.
4309 (void)SimplifyICmpOperands(Cond, LHS, RHS);
4311 // If we have a comparison of a chrec against a constant, try to use value
4312 // ranges to answer this query.
4313 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
4314 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
4315 if (AddRec->getLoop() == L) {
4316 // Form the constant range.
4317 ConstantRange CompRange(
4318 ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
4320 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
4321 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
4325 case ICmpInst::ICMP_NE: { // while (X != Y)
4326 // Convert to: while (X-Y != 0)
4327 ExitLimit EL = HowFarToZero(getMinusSCEV(LHS, RHS), L);
4328 if (EL.hasAnyInfo()) return EL;
4331 case ICmpInst::ICMP_EQ: { // while (X == Y)
4332 // Convert to: while (X-Y == 0)
4333 ExitLimit EL = HowFarToNonZero(getMinusSCEV(LHS, RHS), L);
4334 if (EL.hasAnyInfo()) return EL;
4337 case ICmpInst::ICMP_SLT: {
4338 ExitLimit EL = HowManyLessThans(LHS, RHS, L, true);
4339 if (EL.hasAnyInfo()) return EL;
4342 case ICmpInst::ICMP_SGT: {
4343 ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
4344 getNotSCEV(RHS), L, true);
4345 if (EL.hasAnyInfo()) return EL;
4348 case ICmpInst::ICMP_ULT: {
4349 ExitLimit EL = HowManyLessThans(LHS, RHS, L, false);
4350 if (EL.hasAnyInfo()) return EL;
4353 case ICmpInst::ICMP_UGT: {
4354 ExitLimit EL = HowManyLessThans(getNotSCEV(LHS),
4355 getNotSCEV(RHS), L, false);
4356 if (EL.hasAnyInfo()) return EL;
4361 dbgs() << "ComputeBackedgeTakenCount ";
4362 if (ExitCond->getOperand(0)->getType()->isUnsigned())
4363 dbgs() << "[unsigned] ";
4364 dbgs() << *LHS << " "
4365 << Instruction::getOpcodeName(Instruction::ICmp)
4366 << " " << *RHS << "\n";
4370 return ComputeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
4373 static ConstantInt *
4374 EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
4375 ScalarEvolution &SE) {
4376 const SCEV *InVal = SE.getConstant(C);
4377 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
4378 assert(isa<SCEVConstant>(Val) &&
4379 "Evaluation of SCEV at constant didn't fold correctly?");
4380 return cast<SCEVConstant>(Val)->getValue();
4383 /// GetAddressedElementFromGlobal - Given a global variable with an initializer
4384 /// and a GEP expression (missing the pointer index) indexing into it, return
4385 /// the addressed element of the initializer or null if the index expression is
4388 GetAddressedElementFromGlobal(GlobalVariable *GV,
4389 const std::vector<ConstantInt*> &Indices) {
4390 Constant *Init = GV->getInitializer();
4391 for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
4392 uint64_t Idx = Indices[i]->getZExtValue();
4393 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
4394 assert(Idx < CS->getNumOperands() && "Bad struct index!");
4395 Init = cast<Constant>(CS->getOperand(Idx));
4396 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
4397 if (Idx >= CA->getNumOperands()) return 0; // Bogus program
4398 Init = cast<Constant>(CA->getOperand(Idx));
4399 } else if (isa<ConstantAggregateZero>(Init)) {
4400 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
4401 assert(Idx < STy->getNumElements() && "Bad struct index!");
4402 Init = Constant::getNullValue(STy->getElementType(Idx));
4403 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
4404 if (Idx >= ATy->getNumElements()) return 0; // Bogus program
4405 Init = Constant::getNullValue(ATy->getElementType());
4407 llvm_unreachable("Unknown constant aggregate type!");
4411 return 0; // Unknown initializer type
4417 /// ComputeLoadConstantCompareExitLimit - Given an exit condition of
4418 /// 'icmp op load X, cst', try to see if we can compute the backedge
4419 /// execution count.
4420 ScalarEvolution::ExitLimit
4421 ScalarEvolution::ComputeLoadConstantCompareExitLimit(
4425 ICmpInst::Predicate predicate) {
4427 if (LI->isVolatile()) return getCouldNotCompute();
4429 // Check to see if the loaded pointer is a getelementptr of a global.
4430 // TODO: Use SCEV instead of manually grubbing with GEPs.
4431 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
4432 if (!GEP) return getCouldNotCompute();
4434 // Make sure that it is really a constant global we are gepping, with an
4435 // initializer, and make sure the first IDX is really 0.
4436 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
4437 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
4438 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
4439 !cast<Constant>(GEP->getOperand(1))->isNullValue())
4440 return getCouldNotCompute();
4442 // Okay, we allow one non-constant index into the GEP instruction.
4444 std::vector<ConstantInt*> Indexes;
4445 unsigned VarIdxNum = 0;
4446 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
4447 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
4448 Indexes.push_back(CI);
4449 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
4450 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
4451 VarIdx = GEP->getOperand(i);
4453 Indexes.push_back(0);
4456 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
4457 // Check to see if X is a loop variant variable value now.
4458 const SCEV *Idx = getSCEV(VarIdx);
4459 Idx = getSCEVAtScope(Idx, L);
4461 // We can only recognize very limited forms of loop index expressions, in
4462 // particular, only affine AddRec's like {C1,+,C2}.
4463 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
4464 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
4465 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
4466 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
4467 return getCouldNotCompute();
4469 unsigned MaxSteps = MaxBruteForceIterations;
4470 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
4471 ConstantInt *ItCst = ConstantInt::get(
4472 cast<IntegerType>(IdxExpr->getType()), IterationNum);
4473 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
4475 // Form the GEP offset.
4476 Indexes[VarIdxNum] = Val;
4478 Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
4479 if (Result == 0) break; // Cannot compute!
4481 // Evaluate the condition for this iteration.
4482 Result = ConstantExpr::getICmp(predicate, Result, RHS);
4483 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
4484 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
4486 dbgs() << "\n***\n*** Computed loop count " << *ItCst
4487 << "\n*** From global " << *GV << "*** BB: " << *L->getHeader()
4490 ++NumArrayLenItCounts;
4491 return getConstant(ItCst); // Found terminating iteration!
4494 return getCouldNotCompute();
4498 /// CanConstantFold - Return true if we can constant fold an instruction of the
4499 /// specified type, assuming that all operands were constants.
4500 static bool CanConstantFold(const Instruction *I) {
4501 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
4502 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I))
4505 if (const CallInst *CI = dyn_cast<CallInst>(I))
4506 if (const Function *F = CI->getCalledFunction())
4507 return canConstantFoldCallTo(F);
4511 /// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
4512 /// in the loop that V is derived from. We allow arbitrary operations along the
4513 /// way, but the operands of an operation must either be constants or a value
4514 /// derived from a constant PHI. If this expression does not fit with these
4515 /// constraints, return null.
4516 static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
4517 // If this is not an instruction, or if this is an instruction outside of the
4518 // loop, it can't be derived from a loop PHI.
4519 Instruction *I = dyn_cast<Instruction>(V);
4520 if (I == 0 || !L->contains(I)) return 0;
4522 if (PHINode *PN = dyn_cast<PHINode>(I)) {
4523 if (L->getHeader() == I->getParent())
4526 // We don't currently keep track of the control flow needed to evaluate
4527 // PHIs, so we cannot handle PHIs inside of loops.
4531 // If we won't be able to constant fold this expression even if the operands
4532 // are constants, return early.
4533 if (!CanConstantFold(I)) return 0;
4535 // Otherwise, we can evaluate this instruction if all of its operands are
4536 // constant or derived from a PHI node themselves.
4538 for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
4539 if (!isa<Constant>(I->getOperand(Op))) {
4540 PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
4541 if (P == 0) return 0; // Not evolving from PHI
4545 return 0; // Evolving from multiple different PHIs.
4548 // This is a expression evolving from a constant PHI!
4552 /// EvaluateExpression - Given an expression that passes the
4553 /// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
4554 /// in the loop has the value PHIVal. If we can't fold this expression for some
4555 /// reason, return null.
4556 static Constant *EvaluateExpression(Value *V, Constant *PHIVal,
4557 const TargetData *TD) {
4558 if (isa<PHINode>(V)) return PHIVal;
4559 if (Constant *C = dyn_cast<Constant>(V)) return C;
4560 Instruction *I = cast<Instruction>(V);
4562 std::vector<Constant*> Operands(I->getNumOperands());
4564 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4565 Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
4566 if (Operands[i] == 0) return 0;
4569 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4570 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
4572 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Operands, TD);
4575 /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
4576 /// in the header of its containing loop, we know the loop executes a
4577 /// constant number of times, and the PHI node is just a recurrence
4578 /// involving constants, fold it.
4580 ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
4583 DenseMap<PHINode*, Constant*>::const_iterator I =
4584 ConstantEvolutionLoopExitValue.find(PN);
4585 if (I != ConstantEvolutionLoopExitValue.end())
4588 if (BEs.ugt(MaxBruteForceIterations))
4589 return ConstantEvolutionLoopExitValue[PN] = 0; // Not going to evaluate it.
4591 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
4593 // Since the loop is canonicalized, the PHI node must have two entries. One
4594 // entry must be a constant (coming in from outside of the loop), and the
4595 // second must be derived from the same PHI.
4596 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4597 Constant *StartCST =
4598 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4600 return RetVal = 0; // Must be a constant.
4602 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4603 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4604 !isa<Constant>(BEValue))
4605 return RetVal = 0; // Not derived from same PHI.
4607 // Execute the loop symbolically to determine the exit value.
4608 if (BEs.getActiveBits() >= 32)
4609 return RetVal = 0; // More than 2^32-1 iterations?? Not doing it!
4611 unsigned NumIterations = BEs.getZExtValue(); // must be in range
4612 unsigned IterationNum = 0;
4613 for (Constant *PHIVal = StartCST; ; ++IterationNum) {
4614 if (IterationNum == NumIterations)
4615 return RetVal = PHIVal; // Got exit value!
4617 // Compute the value of the PHI node for the next iteration.
4618 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4619 if (NextPHI == PHIVal)
4620 return RetVal = NextPHI; // Stopped evolving!
4622 return 0; // Couldn't evaluate!
4627 /// ComputeExitCountExhaustively - If the loop is known to execute a
4628 /// constant number of times (the condition evolves only from constants),
4629 /// try to evaluate a few iterations of the loop until we get the exit
4630 /// condition gets a value of ExitWhen (true or false). If we cannot
4631 /// evaluate the trip count of the loop, return getCouldNotCompute().
4632 const SCEV * ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
4635 PHINode *PN = getConstantEvolvingPHI(Cond, L);
4636 if (PN == 0) return getCouldNotCompute();
4638 // If the loop is canonicalized, the PHI will have exactly two entries.
4639 // That's the only form we support here.
4640 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
4642 // One entry must be a constant (coming in from outside of the loop), and the
4643 // second must be derived from the same PHI.
4644 bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
4645 Constant *StartCST =
4646 dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
4647 if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
4649 Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
4650 if (getConstantEvolvingPHI(BEValue, L) != PN &&
4651 !isa<Constant>(BEValue))
4652 return getCouldNotCompute(); // Not derived from same PHI.
4654 // Okay, we find a PHI node that defines the trip count of this loop. Execute
4655 // the loop symbolically to determine when the condition gets a value of
4657 unsigned IterationNum = 0;
4658 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
4659 for (Constant *PHIVal = StartCST;
4660 IterationNum != MaxIterations; ++IterationNum) {
4661 ConstantInt *CondVal =
4662 dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, PHIVal, TD));
4664 // Couldn't symbolically evaluate.
4665 if (!CondVal) return getCouldNotCompute();
4667 if (CondVal->getValue() == uint64_t(ExitWhen)) {
4668 ++NumBruteForceTripCountsComputed;
4669 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
4672 // Compute the value of the PHI node for the next iteration.
4673 Constant *NextPHI = EvaluateExpression(BEValue, PHIVal, TD);
4674 if (NextPHI == 0 || NextPHI == PHIVal)
4675 return getCouldNotCompute();// Couldn't evaluate or not making progress...
4679 // Too many iterations were needed to evaluate.
4680 return getCouldNotCompute();
4683 /// getSCEVAtScope - Return a SCEV expression for the specified value
4684 /// at the specified scope in the program. The L value specifies a loop
4685 /// nest to evaluate the expression at, where null is the top-level or a
4686 /// specified loop is immediately inside of the loop.
4688 /// This method can be used to compute the exit value for a variable defined
4689 /// in a loop by querying what the value will hold in the parent loop.
4691 /// In the case that a relevant loop exit value cannot be computed, the
4692 /// original value V is returned.
4693 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
4694 // Check to see if we've folded this expression at this loop before.
4695 std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
4696 std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
4697 Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
4699 return Pair.first->second ? Pair.first->second : V;
4701 // Otherwise compute it.
4702 const SCEV *C = computeSCEVAtScope(V, L);
4703 ValuesAtScopes[V][L] = C;
4707 const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
4708 if (isa<SCEVConstant>(V)) return V;
4710 // If this instruction is evolved from a constant-evolving PHI, compute the
4711 // exit value from the loop without using SCEVs.
4712 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
4713 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
4714 const Loop *LI = (*this->LI)[I->getParent()];
4715 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
4716 if (PHINode *PN = dyn_cast<PHINode>(I))
4717 if (PN->getParent() == LI->getHeader()) {
4718 // Okay, there is no closed form solution for the PHI node. Check
4719 // to see if the loop that contains it has a known backedge-taken
4720 // count. If so, we may be able to force computation of the exit
4722 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
4723 if (const SCEVConstant *BTCC =
4724 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
4725 // Okay, we know how many times the containing loop executes. If
4726 // this is a constant evolving PHI node, get the final value at
4727 // the specified iteration number.
4728 Constant *RV = getConstantEvolutionLoopExitValue(PN,
4729 BTCC->getValue()->getValue(),
4731 if (RV) return getSCEV(RV);
4735 // Okay, this is an expression that we cannot symbolically evaluate
4736 // into a SCEV. Check to see if it's possible to symbolically evaluate
4737 // the arguments into constants, and if so, try to constant propagate the
4738 // result. This is particularly useful for computing loop exit values.
4739 if (CanConstantFold(I)) {
4740 SmallVector<Constant *, 4> Operands;
4741 bool MadeImprovement = false;
4742 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
4743 Value *Op = I->getOperand(i);
4744 if (Constant *C = dyn_cast<Constant>(Op)) {
4745 Operands.push_back(C);
4749 // If any of the operands is non-constant and if they are
4750 // non-integer and non-pointer, don't even try to analyze them
4751 // with scev techniques.
4752 if (!isSCEVable(Op->getType()))
4755 const SCEV *OrigV = getSCEV(Op);
4756 const SCEV *OpV = getSCEVAtScope(OrigV, L);
4757 MadeImprovement |= OrigV != OpV;
4760 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
4762 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
4763 C = dyn_cast<Constant>(SU->getValue());
4765 if (C->getType() != Op->getType())
4766 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4770 Operands.push_back(C);
4773 // Check to see if getSCEVAtScope actually made an improvement.
4774 if (MadeImprovement) {
4776 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
4777 C = ConstantFoldCompareInstOperands(CI->getPredicate(),
4778 Operands[0], Operands[1], TD);
4780 C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
4788 // This is some other type of SCEVUnknown, just return it.
4792 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
4793 // Avoid performing the look-up in the common case where the specified
4794 // expression has no loop-variant portions.
4795 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
4796 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4797 if (OpAtScope != Comm->getOperand(i)) {
4798 // Okay, at least one of these operands is loop variant but might be
4799 // foldable. Build a new instance of the folded commutative expression.
4800 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
4801 Comm->op_begin()+i);
4802 NewOps.push_back(OpAtScope);
4804 for (++i; i != e; ++i) {
4805 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
4806 NewOps.push_back(OpAtScope);
4808 if (isa<SCEVAddExpr>(Comm))
4809 return getAddExpr(NewOps);
4810 if (isa<SCEVMulExpr>(Comm))
4811 return getMulExpr(NewOps);
4812 if (isa<SCEVSMaxExpr>(Comm))
4813 return getSMaxExpr(NewOps);
4814 if (isa<SCEVUMaxExpr>(Comm))
4815 return getUMaxExpr(NewOps);
4816 llvm_unreachable("Unknown commutative SCEV type!");
4819 // If we got here, all operands are loop invariant.
4823 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
4824 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
4825 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
4826 if (LHS == Div->getLHS() && RHS == Div->getRHS())
4827 return Div; // must be loop invariant
4828 return getUDivExpr(LHS, RHS);
4831 // If this is a loop recurrence for a loop that does not contain L, then we
4832 // are dealing with the final value computed by the loop.
4833 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
4834 // First, attempt to evaluate each operand.
4835 // Avoid performing the look-up in the common case where the specified
4836 // expression has no loop-variant portions.
4837 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4838 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
4839 if (OpAtScope == AddRec->getOperand(i))
4842 // Okay, at least one of these operands is loop variant but might be
4843 // foldable. Build a new instance of the folded commutative expression.
4844 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
4845 AddRec->op_begin()+i);
4846 NewOps.push_back(OpAtScope);
4847 for (++i; i != e; ++i)
4848 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
4850 const SCEV *FoldedRec =
4851 getAddRecExpr(NewOps, AddRec->getLoop(),
4852 AddRec->getNoWrapFlags(SCEV::FlagNW));
4853 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
4854 // The addrec may be folded to a nonrecurrence, for example, if the
4855 // induction variable is multiplied by zero after constant folding. Go
4856 // ahead and return the folded value.
4862 // If the scope is outside the addrec's loop, evaluate it by using the
4863 // loop exit value of the addrec.
4864 if (!AddRec->getLoop()->contains(L)) {
4865 // To evaluate this recurrence, we need to know how many times the AddRec
4866 // loop iterates. Compute this now.
4867 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
4868 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
4870 // Then, evaluate the AddRec.
4871 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
4877 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
4878 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4879 if (Op == Cast->getOperand())
4880 return Cast; // must be loop invariant
4881 return getZeroExtendExpr(Op, Cast->getType());
4884 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
4885 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4886 if (Op == Cast->getOperand())
4887 return Cast; // must be loop invariant
4888 return getSignExtendExpr(Op, Cast->getType());
4891 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
4892 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
4893 if (Op == Cast->getOperand())
4894 return Cast; // must be loop invariant
4895 return getTruncateExpr(Op, Cast->getType());
4898 llvm_unreachable("Unknown SCEV type!");
4902 /// getSCEVAtScope - This is a convenience function which does
4903 /// getSCEVAtScope(getSCEV(V), L).
4904 const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
4905 return getSCEVAtScope(getSCEV(V), L);
4908 /// SolveLinEquationWithOverflow - Finds the minimum unsigned root of the
4909 /// following equation:
4911 /// A * X = B (mod N)
4913 /// where N = 2^BW and BW is the common bit width of A and B. The signedness of
4914 /// A and B isn't important.
4916 /// If the equation does not have a solution, SCEVCouldNotCompute is returned.
4917 static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const APInt &B,
4918 ScalarEvolution &SE) {
4919 uint32_t BW = A.getBitWidth();
4920 assert(BW == B.getBitWidth() && "Bit widths must be the same.");
4921 assert(A != 0 && "A must be non-zero.");
4925 // The gcd of A and N may have only one prime factor: 2. The number of
4926 // trailing zeros in A is its multiplicity
4927 uint32_t Mult2 = A.countTrailingZeros();
4930 // 2. Check if B is divisible by D.
4932 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
4933 // is not less than multiplicity of this prime factor for D.
4934 if (B.countTrailingZeros() < Mult2)
4935 return SE.getCouldNotCompute();
4937 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
4940 // (N / D) may need BW+1 bits in its representation. Hence, we'll use this
4941 // bit width during computations.
4942 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
4943 APInt Mod(BW + 1, 0);
4944 Mod.setBit(BW - Mult2); // Mod = N / D
4945 APInt I = AD.multiplicativeInverse(Mod);
4947 // 4. Compute the minimum unsigned root of the equation:
4948 // I * (B / D) mod (N / D)
4949 APInt Result = (I * B.lshr(Mult2).zext(BW + 1)).urem(Mod);
4951 // The result is guaranteed to be less than 2^BW so we may truncate it to BW
4953 return SE.getConstant(Result.trunc(BW));
4956 /// SolveQuadraticEquation - Find the roots of the quadratic equation for the
4957 /// given quadratic chrec {L,+,M,+,N}. This returns either the two roots (which
4958 /// might be the same) or two SCEVCouldNotCompute objects.
4960 static std::pair<const SCEV *,const SCEV *>
4961 SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
4962 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!");
4963 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
4964 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
4965 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
4967 // We currently can only solve this if the coefficients are constants.
4968 if (!LC || !MC || !NC) {
4969 const SCEV *CNC = SE.getCouldNotCompute();
4970 return std::make_pair(CNC, CNC);
4973 uint32_t BitWidth = LC->getValue()->getValue().getBitWidth();
4974 const APInt &L = LC->getValue()->getValue();
4975 const APInt &M = MC->getValue()->getValue();
4976 const APInt &N = NC->getValue()->getValue();
4977 APInt Two(BitWidth, 2);
4978 APInt Four(BitWidth, 4);
4981 using namespace APIntOps;
4983 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
4984 // The B coefficient is M-N/2
4988 // The A coefficient is N/2
4989 APInt A(N.sdiv(Two));
4991 // Compute the B^2-4ac term.
4994 SqrtTerm -= Four * (A * C);
4996 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
4997 // integer value or else APInt::sqrt() will assert.
4998 APInt SqrtVal(SqrtTerm.sqrt());
5000 // Compute the two solutions for the quadratic formula.
5001 // The divisions must be performed as signed divisions.
5003 APInt TwoA( A << 1 );
5004 if (TwoA.isMinValue()) {
5005 const SCEV *CNC = SE.getCouldNotCompute();
5006 return std::make_pair(CNC, CNC);
5009 LLVMContext &Context = SE.getContext();
5011 ConstantInt *Solution1 =
5012 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
5013 ConstantInt *Solution2 =
5014 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
5016 return std::make_pair(SE.getConstant(Solution1),
5017 SE.getConstant(Solution2));
5018 } // end APIntOps namespace
5021 /// HowFarToZero - Return the number of times a backedge comparing the specified
5022 /// value to zero will execute. If not computable, return CouldNotCompute.
5024 /// This is only used for loops with a "x != y" exit test. The exit condition is
5025 /// now expressed as a single expression, V = x-y. So the exit test is
5026 /// effectively V != 0. We know and take advantage of the fact that this
5027 /// expression only being used in a comparison by zero context.
5028 ScalarEvolution::ExitLimit
5029 ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) {
5030 // If the value is a constant
5031 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
5032 // If the value is already zero, the branch will execute zero times.
5033 if (C->getValue()->isZero()) return C;
5034 return getCouldNotCompute(); // Otherwise it will loop infinitely.
5037 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
5038 if (!AddRec || AddRec->getLoop() != L)
5039 return getCouldNotCompute();
5041 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
5042 // the quadratic equation to solve it.
5043 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
5044 std::pair<const SCEV *,const SCEV *> Roots =
5045 SolveQuadraticEquation(AddRec, *this);
5046 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
5047 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
5050 dbgs() << "HFTZ: " << *V << " - sol#1: " << *R1
5051 << " sol#2: " << *R2 << "\n";
5053 // Pick the smallest positive root value.
5054 if (ConstantInt *CB =
5055 dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
5058 if (CB->getZExtValue() == false)
5059 std::swap(R1, R2); // R1 is the minimum root now.
5061 // We can only use this value if the chrec ends up with an exact zero
5062 // value at this index. When solving for "X*X != 5", for example, we
5063 // should not accept a root of 2.
5064 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
5066 return R1; // We found a quadratic root!
5069 return getCouldNotCompute();
5072 // Otherwise we can only handle this if it is affine.
5073 if (!AddRec->isAffine())
5074 return getCouldNotCompute();
5076 // If this is an affine expression, the execution count of this branch is
5077 // the minimum unsigned root of the following equation:
5079 // Start + Step*N = 0 (mod 2^BW)
5083 // Step*N = -Start (mod 2^BW)
5085 // where BW is the common bit width of Start and Step.
5087 // Get the initial value for the loop.
5088 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
5089 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
5091 // For now we handle only constant steps.
5093 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
5094 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
5095 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
5096 // We have not yet seen any such cases.
5097 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
5099 return getCouldNotCompute();
5101 // For positive steps (counting up until unsigned overflow):
5102 // N = -Start/Step (as unsigned)
5103 // For negative steps (counting down to zero):
5105 // First compute the unsigned distance from zero in the direction of Step.
5106 bool CountDown = StepC->getValue()->getValue().isNegative();
5107 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
5109 // Handle unitary steps, which cannot wraparound.
5110 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
5111 // N = Distance (as unsigned)
5112 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue())
5115 // If the recurrence is known not to wraparound, unsigned divide computes the
5116 // back edge count. We know that the value will either become zero (and thus
5117 // the loop terminates), that the loop will terminate through some other exit
5118 // condition first, or that the loop has undefined behavior. This means
5119 // we can't "miss" the exit value, even with nonunit stride.
5121 // FIXME: Prove that loops always exhibits *acceptable* undefined
5122 // behavior. Loops must exhibit defined behavior until a wrapped value is
5123 // actually used. So the trip count computed by udiv could be smaller than the
5124 // number of well-defined iterations.
5125 if (AddRec->getNoWrapFlags(SCEV::FlagNW))
5126 // FIXME: We really want an "isexact" bit for udiv.
5127 return getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
5129 // Then, try to solve the above equation provided that Start is constant.
5130 if (const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start))
5131 return SolveLinEquationWithOverflow(StepC->getValue()->getValue(),
5132 -StartC->getValue()->getValue(),
5134 return getCouldNotCompute();
5137 /// HowFarToNonZero - Return the number of times a backedge checking the
5138 /// specified value for nonzero will execute. If not computable, return
5140 ScalarEvolution::ExitLimit
5141 ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) {
5142 // Loops that look like: while (X == 0) are very strange indeed. We don't
5143 // handle them yet except for the trivial case. This could be expanded in the
5144 // future as needed.
5146 // If the value is a constant, check to see if it is known to be non-zero
5147 // already. If so, the backedge will execute zero times.
5148 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
5149 if (!C->getValue()->isNullValue())
5150 return getConstant(C->getType(), 0);
5151 return getCouldNotCompute(); // Otherwise it will loop infinitely.
5154 // We could implement others, but I really doubt anyone writes loops like
5155 // this, and if they did, they would already be constant folded.
5156 return getCouldNotCompute();
5159 /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
5160 /// (which may not be an immediate predecessor) which has exactly one
5161 /// successor from which BB is reachable, or null if no such block is
5164 std::pair<BasicBlock *, BasicBlock *>
5165 ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
5166 // If the block has a unique predecessor, then there is no path from the
5167 // predecessor to the block that does not go through the direct edge
5168 // from the predecessor to the block.
5169 if (BasicBlock *Pred = BB->getSinglePredecessor())
5170 return std::make_pair(Pred, BB);
5172 // A loop's header is defined to be a block that dominates the loop.
5173 // If the header has a unique predecessor outside the loop, it must be
5174 // a block that has exactly one successor that can reach the loop.
5175 if (Loop *L = LI->getLoopFor(BB))
5176 return std::make_pair(L->getLoopPredecessor(), L->getHeader());
5178 return std::pair<BasicBlock *, BasicBlock *>();
5181 /// HasSameValue - SCEV structural equivalence is usually sufficient for
5182 /// testing whether two expressions are equal, however for the purposes of
5183 /// looking for a condition guarding a loop, it can be useful to be a little
5184 /// more general, since a front-end may have replicated the controlling
5187 static bool HasSameValue(const SCEV *A, const SCEV *B) {
5188 // Quick check to see if they are the same SCEV.
5189 if (A == B) return true;
5191 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
5192 // two different instructions with the same value. Check for this case.
5193 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
5194 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
5195 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
5196 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
5197 if (AI->isIdenticalTo(BI) && !AI->mayReadFromMemory())
5200 // Otherwise assume they may have a different value.
5204 /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
5205 /// predicate Pred. Return true iff any changes were made.
5207 bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
5208 const SCEV *&LHS, const SCEV *&RHS) {
5209 bool Changed = false;
5211 // Canonicalize a constant to the right side.
5212 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
5213 // Check for both operands constant.
5214 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
5215 if (ConstantExpr::getICmp(Pred,
5217 RHSC->getValue())->isNullValue())
5218 goto trivially_false;
5220 goto trivially_true;
5222 // Otherwise swap the operands to put the constant on the right.
5223 std::swap(LHS, RHS);
5224 Pred = ICmpInst::getSwappedPredicate(Pred);
5228 // If we're comparing an addrec with a value which is loop-invariant in the
5229 // addrec's loop, put the addrec on the left. Also make a dominance check,
5230 // as both operands could be addrecs loop-invariant in each other's loop.
5231 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
5232 const Loop *L = AR->getLoop();
5233 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
5234 std::swap(LHS, RHS);
5235 Pred = ICmpInst::getSwappedPredicate(Pred);
5240 // If there's a constant operand, canonicalize comparisons with boundary
5241 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
5242 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
5243 const APInt &RA = RC->getValue()->getValue();
5245 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5246 case ICmpInst::ICMP_EQ:
5247 case ICmpInst::ICMP_NE:
5249 case ICmpInst::ICMP_UGE:
5250 if ((RA - 1).isMinValue()) {
5251 Pred = ICmpInst::ICMP_NE;
5252 RHS = getConstant(RA - 1);
5256 if (RA.isMaxValue()) {
5257 Pred = ICmpInst::ICMP_EQ;
5261 if (RA.isMinValue()) goto trivially_true;
5263 Pred = ICmpInst::ICMP_UGT;
5264 RHS = getConstant(RA - 1);
5267 case ICmpInst::ICMP_ULE:
5268 if ((RA + 1).isMaxValue()) {
5269 Pred = ICmpInst::ICMP_NE;
5270 RHS = getConstant(RA + 1);
5274 if (RA.isMinValue()) {
5275 Pred = ICmpInst::ICMP_EQ;
5279 if (RA.isMaxValue()) goto trivially_true;
5281 Pred = ICmpInst::ICMP_ULT;
5282 RHS = getConstant(RA + 1);
5285 case ICmpInst::ICMP_SGE:
5286 if ((RA - 1).isMinSignedValue()) {
5287 Pred = ICmpInst::ICMP_NE;
5288 RHS = getConstant(RA - 1);
5292 if (RA.isMaxSignedValue()) {
5293 Pred = ICmpInst::ICMP_EQ;
5297 if (RA.isMinSignedValue()) goto trivially_true;
5299 Pred = ICmpInst::ICMP_SGT;
5300 RHS = getConstant(RA - 1);
5303 case ICmpInst::ICMP_SLE:
5304 if ((RA + 1).isMaxSignedValue()) {
5305 Pred = ICmpInst::ICMP_NE;
5306 RHS = getConstant(RA + 1);
5310 if (RA.isMinSignedValue()) {
5311 Pred = ICmpInst::ICMP_EQ;
5315 if (RA.isMaxSignedValue()) goto trivially_true;
5317 Pred = ICmpInst::ICMP_SLT;
5318 RHS = getConstant(RA + 1);
5321 case ICmpInst::ICMP_UGT:
5322 if (RA.isMinValue()) {
5323 Pred = ICmpInst::ICMP_NE;
5327 if ((RA + 1).isMaxValue()) {
5328 Pred = ICmpInst::ICMP_EQ;
5329 RHS = getConstant(RA + 1);
5333 if (RA.isMaxValue()) goto trivially_false;
5335 case ICmpInst::ICMP_ULT:
5336 if (RA.isMaxValue()) {
5337 Pred = ICmpInst::ICMP_NE;
5341 if ((RA - 1).isMinValue()) {
5342 Pred = ICmpInst::ICMP_EQ;
5343 RHS = getConstant(RA - 1);
5347 if (RA.isMinValue()) goto trivially_false;
5349 case ICmpInst::ICMP_SGT:
5350 if (RA.isMinSignedValue()) {
5351 Pred = ICmpInst::ICMP_NE;
5355 if ((RA + 1).isMaxSignedValue()) {
5356 Pred = ICmpInst::ICMP_EQ;
5357 RHS = getConstant(RA + 1);
5361 if (RA.isMaxSignedValue()) goto trivially_false;
5363 case ICmpInst::ICMP_SLT:
5364 if (RA.isMaxSignedValue()) {
5365 Pred = ICmpInst::ICMP_NE;
5369 if ((RA - 1).isMinSignedValue()) {
5370 Pred = ICmpInst::ICMP_EQ;
5371 RHS = getConstant(RA - 1);
5375 if (RA.isMinSignedValue()) goto trivially_false;
5380 // Check for obvious equality.
5381 if (HasSameValue(LHS, RHS)) {
5382 if (ICmpInst::isTrueWhenEqual(Pred))
5383 goto trivially_true;
5384 if (ICmpInst::isFalseWhenEqual(Pred))
5385 goto trivially_false;
5388 // If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
5389 // adding or subtracting 1 from one of the operands.
5391 case ICmpInst::ICMP_SLE:
5392 if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
5393 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5395 Pred = ICmpInst::ICMP_SLT;
5397 } else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
5398 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5400 Pred = ICmpInst::ICMP_SLT;
5404 case ICmpInst::ICMP_SGE:
5405 if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
5406 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5408 Pred = ICmpInst::ICMP_SGT;
5410 } else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
5411 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5413 Pred = ICmpInst::ICMP_SGT;
5417 case ICmpInst::ICMP_ULE:
5418 if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
5419 RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
5421 Pred = ICmpInst::ICMP_ULT;
5423 } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
5424 LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS,
5426 Pred = ICmpInst::ICMP_ULT;
5430 case ICmpInst::ICMP_UGE:
5431 if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
5432 RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS,
5434 Pred = ICmpInst::ICMP_UGT;
5436 } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
5437 LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
5439 Pred = ICmpInst::ICMP_UGT;
5447 // TODO: More simplifications are possible here.
5453 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5454 Pred = ICmpInst::ICMP_EQ;
5459 LHS = RHS = getConstant(ConstantInt::getFalse(getContext()));
5460 Pred = ICmpInst::ICMP_NE;
5464 bool ScalarEvolution::isKnownNegative(const SCEV *S) {
5465 return getSignedRange(S).getSignedMax().isNegative();
5468 bool ScalarEvolution::isKnownPositive(const SCEV *S) {
5469 return getSignedRange(S).getSignedMin().isStrictlyPositive();
5472 bool ScalarEvolution::isKnownNonNegative(const SCEV *S) {
5473 return !getSignedRange(S).getSignedMin().isNegative();
5476 bool ScalarEvolution::isKnownNonPositive(const SCEV *S) {
5477 return !getSignedRange(S).getSignedMax().isStrictlyPositive();
5480 bool ScalarEvolution::isKnownNonZero(const SCEV *S) {
5481 return isKnownNegative(S) || isKnownPositive(S);
5484 bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
5485 const SCEV *LHS, const SCEV *RHS) {
5486 // Canonicalize the inputs first.
5487 (void)SimplifyICmpOperands(Pred, LHS, RHS);
5489 // If LHS or RHS is an addrec, check to see if the condition is true in
5490 // every iteration of the loop.
5491 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
5492 if (isLoopEntryGuardedByCond(
5493 AR->getLoop(), Pred, AR->getStart(), RHS) &&
5494 isLoopBackedgeGuardedByCond(
5495 AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
5497 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
5498 if (isLoopEntryGuardedByCond(
5499 AR->getLoop(), Pred, LHS, AR->getStart()) &&
5500 isLoopBackedgeGuardedByCond(
5501 AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
5504 // Otherwise see what can be done with known constant ranges.
5505 return isKnownPredicateWithRanges(Pred, LHS, RHS);
5509 ScalarEvolution::isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
5510 const SCEV *LHS, const SCEV *RHS) {
5511 if (HasSameValue(LHS, RHS))
5512 return ICmpInst::isTrueWhenEqual(Pred);
5514 // This code is split out from isKnownPredicate because it is called from
5515 // within isLoopEntryGuardedByCond.
5518 llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5520 case ICmpInst::ICMP_SGT:
5521 Pred = ICmpInst::ICMP_SLT;
5522 std::swap(LHS, RHS);
5523 case ICmpInst::ICMP_SLT: {
5524 ConstantRange LHSRange = getSignedRange(LHS);
5525 ConstantRange RHSRange = getSignedRange(RHS);
5526 if (LHSRange.getSignedMax().slt(RHSRange.getSignedMin()))
5528 if (LHSRange.getSignedMin().sge(RHSRange.getSignedMax()))
5532 case ICmpInst::ICMP_SGE:
5533 Pred = ICmpInst::ICMP_SLE;
5534 std::swap(LHS, RHS);
5535 case ICmpInst::ICMP_SLE: {
5536 ConstantRange LHSRange = getSignedRange(LHS);
5537 ConstantRange RHSRange = getSignedRange(RHS);
5538 if (LHSRange.getSignedMax().sle(RHSRange.getSignedMin()))
5540 if (LHSRange.getSignedMin().sgt(RHSRange.getSignedMax()))
5544 case ICmpInst::ICMP_UGT:
5545 Pred = ICmpInst::ICMP_ULT;
5546 std::swap(LHS, RHS);
5547 case ICmpInst::ICMP_ULT: {
5548 ConstantRange LHSRange = getUnsignedRange(LHS);
5549 ConstantRange RHSRange = getUnsignedRange(RHS);
5550 if (LHSRange.getUnsignedMax().ult(RHSRange.getUnsignedMin()))
5552 if (LHSRange.getUnsignedMin().uge(RHSRange.getUnsignedMax()))
5556 case ICmpInst::ICMP_UGE:
5557 Pred = ICmpInst::ICMP_ULE;
5558 std::swap(LHS, RHS);
5559 case ICmpInst::ICMP_ULE: {
5560 ConstantRange LHSRange = getUnsignedRange(LHS);
5561 ConstantRange RHSRange = getUnsignedRange(RHS);
5562 if (LHSRange.getUnsignedMax().ule(RHSRange.getUnsignedMin()))
5564 if (LHSRange.getUnsignedMin().ugt(RHSRange.getUnsignedMax()))
5568 case ICmpInst::ICMP_NE: {
5569 if (getUnsignedRange(LHS).intersectWith(getUnsignedRange(RHS)).isEmptySet())
5571 if (getSignedRange(LHS).intersectWith(getSignedRange(RHS)).isEmptySet())
5574 const SCEV *Diff = getMinusSCEV(LHS, RHS);
5575 if (isKnownNonZero(Diff))
5579 case ICmpInst::ICMP_EQ:
5580 // The check at the top of the function catches the case where
5581 // the values are known to be equal.
5587 /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
5588 /// protected by a conditional between LHS and RHS. This is used to
5589 /// to eliminate casts.
5591 ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
5592 ICmpInst::Predicate Pred,
5593 const SCEV *LHS, const SCEV *RHS) {
5594 // Interpret a null as meaning no loop, where there is obviously no guard
5595 // (interprocedural conditions notwithstanding).
5596 if (!L) return true;
5598 BasicBlock *Latch = L->getLoopLatch();
5602 BranchInst *LoopContinuePredicate =
5603 dyn_cast<BranchInst>(Latch->getTerminator());
5604 if (!LoopContinuePredicate ||
5605 LoopContinuePredicate->isUnconditional())
5608 return isImpliedCond(Pred, LHS, RHS,
5609 LoopContinuePredicate->getCondition(),
5610 LoopContinuePredicate->getSuccessor(0) != L->getHeader());
5613 /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
5614 /// by a conditional between LHS and RHS. This is used to help avoid max
5615 /// expressions in loop trip counts, and to eliminate casts.
5617 ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
5618 ICmpInst::Predicate Pred,
5619 const SCEV *LHS, const SCEV *RHS) {
5620 // Interpret a null as meaning no loop, where there is obviously no guard
5621 // (interprocedural conditions notwithstanding).
5622 if (!L) return false;
5624 // Starting at the loop predecessor, climb up the predecessor chain, as long
5625 // as there are predecessors that can be found that have unique successors
5626 // leading to the original header.
5627 for (std::pair<BasicBlock *, BasicBlock *>
5628 Pair(L->getLoopPredecessor(), L->getHeader());
5630 Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
5632 BranchInst *LoopEntryPredicate =
5633 dyn_cast<BranchInst>(Pair.first->getTerminator());
5634 if (!LoopEntryPredicate ||
5635 LoopEntryPredicate->isUnconditional())
5638 if (isImpliedCond(Pred, LHS, RHS,
5639 LoopEntryPredicate->getCondition(),
5640 LoopEntryPredicate->getSuccessor(0) != Pair.second))
5647 /// isImpliedCond - Test whether the condition described by Pred, LHS,
5648 /// and RHS is true whenever the given Cond value evaluates to true.
5649 bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred,
5650 const SCEV *LHS, const SCEV *RHS,
5651 Value *FoundCondValue,
5653 // Recursively handle And and Or conditions.
5654 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FoundCondValue)) {
5655 if (BO->getOpcode() == Instruction::And) {
5657 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5658 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5659 } else if (BO->getOpcode() == Instruction::Or) {
5661 return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
5662 isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
5666 ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
5667 if (!ICI) return false;
5669 // Bail if the ICmp's operands' types are wider than the needed type
5670 // before attempting to call getSCEV on them. This avoids infinite
5671 // recursion, since the analysis of widening casts can require loop
5672 // exit condition information for overflow checking, which would
5674 if (getTypeSizeInBits(LHS->getType()) <
5675 getTypeSizeInBits(ICI->getOperand(0)->getType()))
5678 // Now that we found a conditional branch that dominates the loop, check to
5679 // see if it is the comparison we are looking for.
5680 ICmpInst::Predicate FoundPred;
5682 FoundPred = ICI->getInversePredicate();
5684 FoundPred = ICI->getPredicate();
5686 const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
5687 const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
5689 // Balance the types. The case where FoundLHS' type is wider than
5690 // LHS' type is checked for above.
5691 if (getTypeSizeInBits(LHS->getType()) >
5692 getTypeSizeInBits(FoundLHS->getType())) {
5693 if (CmpInst::isSigned(Pred)) {
5694 FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
5695 FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
5697 FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
5698 FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
5702 // Canonicalize the query to match the way instcombine will have
5703 // canonicalized the comparison.
5704 if (SimplifyICmpOperands(Pred, LHS, RHS))
5706 return CmpInst::isTrueWhenEqual(Pred);
5707 if (SimplifyICmpOperands(FoundPred, FoundLHS, FoundRHS))
5708 if (FoundLHS == FoundRHS)
5709 return CmpInst::isFalseWhenEqual(Pred);
5711 // Check to see if we can make the LHS or RHS match.
5712 if (LHS == FoundRHS || RHS == FoundLHS) {
5713 if (isa<SCEVConstant>(RHS)) {
5714 std::swap(FoundLHS, FoundRHS);
5715 FoundPred = ICmpInst::getSwappedPredicate(FoundPred);
5717 std::swap(LHS, RHS);
5718 Pred = ICmpInst::getSwappedPredicate(Pred);
5722 // Check whether the found predicate is the same as the desired predicate.
5723 if (FoundPred == Pred)
5724 return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
5726 // Check whether swapping the found predicate makes it the same as the
5727 // desired predicate.
5728 if (ICmpInst::getSwappedPredicate(FoundPred) == Pred) {
5729 if (isa<SCEVConstant>(RHS))
5730 return isImpliedCondOperands(Pred, LHS, RHS, FoundRHS, FoundLHS);
5732 return isImpliedCondOperands(ICmpInst::getSwappedPredicate(Pred),
5733 RHS, LHS, FoundLHS, FoundRHS);
5736 // Check whether the actual condition is beyond sufficient.
5737 if (FoundPred == ICmpInst::ICMP_EQ)
5738 if (ICmpInst::isTrueWhenEqual(Pred))
5739 if (isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS))
5741 if (Pred == ICmpInst::ICMP_NE)
5742 if (!ICmpInst::isTrueWhenEqual(FoundPred))
5743 if (isImpliedCondOperands(FoundPred, LHS, RHS, FoundLHS, FoundRHS))
5746 // Otherwise assume the worst.
5750 /// isImpliedCondOperands - Test whether the condition described by Pred,
5751 /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
5752 /// and FoundRHS is true.
5753 bool ScalarEvolution::isImpliedCondOperands(ICmpInst::Predicate Pred,
5754 const SCEV *LHS, const SCEV *RHS,
5755 const SCEV *FoundLHS,
5756 const SCEV *FoundRHS) {
5757 return isImpliedCondOperandsHelper(Pred, LHS, RHS,
5758 FoundLHS, FoundRHS) ||
5759 // ~x < ~y --> x > y
5760 isImpliedCondOperandsHelper(Pred, LHS, RHS,
5761 getNotSCEV(FoundRHS),
5762 getNotSCEV(FoundLHS));
5765 /// isImpliedCondOperandsHelper - Test whether the condition described by
5766 /// Pred, LHS, and RHS is true whenever the condition described by Pred,
5767 /// FoundLHS, and FoundRHS is true.
5769 ScalarEvolution::isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
5770 const SCEV *LHS, const SCEV *RHS,
5771 const SCEV *FoundLHS,
5772 const SCEV *FoundRHS) {
5774 default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
5775 case ICmpInst::ICMP_EQ:
5776 case ICmpInst::ICMP_NE:
5777 if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
5780 case ICmpInst::ICMP_SLT:
5781 case ICmpInst::ICMP_SLE:
5782 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
5783 isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, RHS, FoundRHS))
5786 case ICmpInst::ICMP_SGT:
5787 case ICmpInst::ICMP_SGE:
5788 if (isKnownPredicateWithRanges(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
5789 isKnownPredicateWithRanges(ICmpInst::ICMP_SLE, RHS, FoundRHS))
5792 case ICmpInst::ICMP_ULT:
5793 case ICmpInst::ICMP_ULE:
5794 if (isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
5795 isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, RHS, FoundRHS))
5798 case ICmpInst::ICMP_UGT:
5799 case ICmpInst::ICMP_UGE:
5800 if (isKnownPredicateWithRanges(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
5801 isKnownPredicateWithRanges(ICmpInst::ICMP_ULE, RHS, FoundRHS))
5809 /// getBECount - Subtract the end and start values and divide by the step,
5810 /// rounding up, to get the number of times the backedge is executed. Return
5811 /// CouldNotCompute if an intermediate computation overflows.
5812 const SCEV *ScalarEvolution::getBECount(const SCEV *Start,
5816 assert(!isKnownNegative(Step) &&
5817 "This code doesn't handle negative strides yet!");
5819 Type *Ty = Start->getType();
5821 // When Start == End, we have an exact BECount == 0. Short-circuit this case
5822 // here because SCEV may not be able to determine that the unsigned division
5823 // after rounding is zero.
5825 return getConstant(Ty, 0);
5827 const SCEV *NegOne = getConstant(Ty, (uint64_t)-1);
5828 const SCEV *Diff = getMinusSCEV(End, Start);
5829 const SCEV *RoundUp = getAddExpr(Step, NegOne);
5831 // Add an adjustment to the difference between End and Start so that
5832 // the division will effectively round up.
5833 const SCEV *Add = getAddExpr(Diff, RoundUp);
5836 // Check Add for unsigned overflow.
5837 // TODO: More sophisticated things could be done here.
5838 Type *WideTy = IntegerType::get(getContext(),
5839 getTypeSizeInBits(Ty) + 1);
5840 const SCEV *EDiff = getZeroExtendExpr(Diff, WideTy);
5841 const SCEV *ERoundUp = getZeroExtendExpr(RoundUp, WideTy);
5842 const SCEV *OperandExtendedAdd = getAddExpr(EDiff, ERoundUp);
5843 if (getZeroExtendExpr(Add, WideTy) != OperandExtendedAdd)
5844 return getCouldNotCompute();
5847 return getUDivExpr(Add, Step);
5850 /// HowManyLessThans - Return the number of times a backedge containing the
5851 /// specified less-than comparison will execute. If not computable, return
5852 /// CouldNotCompute.
5853 ScalarEvolution::ExitLimit
5854 ScalarEvolution::HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
5855 const Loop *L, bool isSigned) {
5856 // Only handle: "ADDREC < LoopInvariant".
5857 if (!isLoopInvariant(RHS, L)) return getCouldNotCompute();
5859 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS);
5860 if (!AddRec || AddRec->getLoop() != L)
5861 return getCouldNotCompute();
5863 // Check to see if we have a flag which makes analysis easy.
5864 bool NoWrap = isSigned ? AddRec->getNoWrapFlags(SCEV::FlagNSW) :
5865 AddRec->getNoWrapFlags(SCEV::FlagNUW);
5867 if (AddRec->isAffine()) {
5868 unsigned BitWidth = getTypeSizeInBits(AddRec->getType());
5869 const SCEV *Step = AddRec->getStepRecurrence(*this);
5872 return getCouldNotCompute();
5873 if (Step->isOne()) {
5874 // With unit stride, the iteration never steps past the limit value.
5875 } else if (isKnownPositive(Step)) {
5876 // Test whether a positive iteration can step past the limit
5877 // value and past the maximum value for its type in a single step.
5878 // Note that it's not sufficient to check NoWrap here, because even
5879 // though the value after a wrap is undefined, it's not undefined
5880 // behavior, so if wrap does occur, the loop could either terminate or
5881 // loop infinitely, but in either case, the loop is guaranteed to
5882 // iterate at least until the iteration where the wrapping occurs.
5883 const SCEV *One = getConstant(Step->getType(), 1);
5885 APInt Max = APInt::getSignedMaxValue(BitWidth);
5886 if ((Max - getSignedRange(getMinusSCEV(Step, One)).getSignedMax())
5887 .slt(getSignedRange(RHS).getSignedMax()))
5888 return getCouldNotCompute();
5890 APInt Max = APInt::getMaxValue(BitWidth);
5891 if ((Max - getUnsignedRange(getMinusSCEV(Step, One)).getUnsignedMax())
5892 .ult(getUnsignedRange(RHS).getUnsignedMax()))
5893 return getCouldNotCompute();
5896 // TODO: Handle negative strides here and below.
5897 return getCouldNotCompute();
5899 // We know the LHS is of the form {n,+,s} and the RHS is some loop-invariant
5900 // m. So, we count the number of iterations in which {n,+,s} < m is true.
5901 // Note that we cannot simply return max(m-n,0)/s because it's not safe to
5902 // treat m-n as signed nor unsigned due to overflow possibility.
5904 // First, we get the value of the LHS in the first iteration: n
5905 const SCEV *Start = AddRec->getOperand(0);
5907 // Determine the minimum constant start value.
5908 const SCEV *MinStart = getConstant(isSigned ?
5909 getSignedRange(Start).getSignedMin() :
5910 getUnsignedRange(Start).getUnsignedMin());
5912 // If we know that the condition is true in order to enter the loop,
5913 // then we know that it will run exactly (m-n)/s times. Otherwise, we
5914 // only know that it will execute (max(m,n)-n)/s times. In both cases,
5915 // the division must round up.
5916 const SCEV *End = RHS;
5917 if (!isLoopEntryGuardedByCond(L,
5918 isSigned ? ICmpInst::ICMP_SLT :
5920 getMinusSCEV(Start, Step), RHS))
5921 End = isSigned ? getSMaxExpr(RHS, Start)
5922 : getUMaxExpr(RHS, Start);
5924 // Determine the maximum constant end value.
5925 const SCEV *MaxEnd = getConstant(isSigned ?
5926 getSignedRange(End).getSignedMax() :
5927 getUnsignedRange(End).getUnsignedMax());
5929 // If MaxEnd is within a step of the maximum integer value in its type,
5930 // adjust it down to the minimum value which would produce the same effect.
5931 // This allows the subsequent ceiling division of (N+(step-1))/step to
5932 // compute the correct value.
5933 const SCEV *StepMinusOne = getMinusSCEV(Step,
5934 getConstant(Step->getType(), 1));
5937 getMinusSCEV(getConstant(APInt::getSignedMaxValue(BitWidth)),
5940 getMinusSCEV(getConstant(APInt::getMaxValue(BitWidth)),
5943 // Finally, we subtract these two values and divide, rounding up, to get
5944 // the number of times the backedge is executed.
5945 const SCEV *BECount = getBECount(Start, End, Step, NoWrap);
5947 // The maximum backedge count is similar, except using the minimum start
5948 // value and the maximum end value.
5949 // If we already have an exact constant BECount, use it instead.
5950 const SCEV *MaxBECount = isa<SCEVConstant>(BECount) ? BECount
5951 : getBECount(MinStart, MaxEnd, Step, NoWrap);
5953 // If the stride is nonconstant, and NoWrap == true, then
5954 // getBECount(MinStart, MaxEnd) may not compute. This would result in an
5955 // exact BECount and invalid MaxBECount, which should be avoided to catch
5956 // more optimization opportunities.
5957 if (isa<SCEVCouldNotCompute>(MaxBECount))
5958 MaxBECount = BECount;
5960 return ExitLimit(BECount, MaxBECount);
5963 return getCouldNotCompute();
5966 /// getNumIterationsInRange - Return the number of iterations of this loop that
5967 /// produce values in the specified constant range. Another way of looking at
5968 /// this is that it returns the first iteration number where the value is not in
5969 /// the condition, thus computing the exit count. If the iteration count can't
5970 /// be computed, an instance of SCEVCouldNotCompute is returned.
5971 const SCEV *SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
5972 ScalarEvolution &SE) const {
5973 if (Range.isFullSet()) // Infinite loop.
5974 return SE.getCouldNotCompute();
5976 // If the start is a non-zero constant, shift the range to simplify things.
5977 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(getStart()))
5978 if (!SC->getValue()->isZero()) {
5979 SmallVector<const SCEV *, 4> Operands(op_begin(), op_end());
5980 Operands[0] = SE.getConstant(SC->getType(), 0);
5981 const SCEV *Shifted = SE.getAddRecExpr(Operands, getLoop(),
5982 getNoWrapFlags(FlagNW));
5983 if (const SCEVAddRecExpr *ShiftedAddRec =
5984 dyn_cast<SCEVAddRecExpr>(Shifted))
5985 return ShiftedAddRec->getNumIterationsInRange(
5986 Range.subtract(SC->getValue()->getValue()), SE);
5987 // This is strange and shouldn't happen.
5988 return SE.getCouldNotCompute();
5991 // The only time we can solve this is when we have all constant indices.
5992 // Otherwise, we cannot determine the overflow conditions.
5993 for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
5994 if (!isa<SCEVConstant>(getOperand(i)))
5995 return SE.getCouldNotCompute();
5998 // Okay at this point we know that all elements of the chrec are constants and
5999 // that the start element is zero.
6001 // First check to see if the range contains zero. If not, the first
6003 unsigned BitWidth = SE.getTypeSizeInBits(getType());
6004 if (!Range.contains(APInt(BitWidth, 0)))
6005 return SE.getConstant(getType(), 0);
6008 // If this is an affine expression then we have this situation:
6009 // Solve {0,+,A} in Range === Ax in Range
6011 // We know that zero is in the range. If A is positive then we know that
6012 // the upper value of the range must be the first possible exit value.
6013 // If A is negative then the lower of the range is the last possible loop
6014 // value. Also note that we already checked for a full range.
6015 APInt One(BitWidth,1);
6016 APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
6017 APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
6019 // The exit value should be (End+A)/A.
6020 APInt ExitVal = (End + A).udiv(A);
6021 ConstantInt *ExitValue = ConstantInt::get(SE.getContext(), ExitVal);
6023 // Evaluate at the exit value. If we really did fall out of the valid
6024 // range, then we computed our trip count, otherwise wrap around or other
6025 // things must have happened.
6026 ConstantInt *Val = EvaluateConstantChrecAtConstant(this, ExitValue, SE);
6027 if (Range.contains(Val->getValue()))
6028 return SE.getCouldNotCompute(); // Something strange happened
6030 // Ensure that the previous value is in the range. This is a sanity check.
6031 assert(Range.contains(
6032 EvaluateConstantChrecAtConstant(this,
6033 ConstantInt::get(SE.getContext(), ExitVal - One), SE)->getValue()) &&
6034 "Linear scev computation is off in a bad way!");
6035 return SE.getConstant(ExitValue);
6036 } else if (isQuadratic()) {
6037 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of the
6038 // quadratic equation to solve it. To do this, we must frame our problem in
6039 // terms of figuring out when zero is crossed, instead of when
6040 // Range.getUpper() is crossed.
6041 SmallVector<const SCEV *, 4> NewOps(op_begin(), op_end());
6042 NewOps[0] = SE.getNegativeSCEV(SE.getConstant(Range.getUpper()));
6043 const SCEV *NewAddRec = SE.getAddRecExpr(NewOps, getLoop(),
6044 // getNoWrapFlags(FlagNW)
6047 // Next, solve the constructed addrec
6048 std::pair<const SCEV *,const SCEV *> Roots =
6049 SolveQuadraticEquation(cast<SCEVAddRecExpr>(NewAddRec), SE);
6050 const SCEVConstant *R1 = dyn_cast<SCEVConstant>(Roots.first);
6051 const SCEVConstant *R2 = dyn_cast<SCEVConstant>(Roots.second);
6053 // Pick the smallest positive root value.
6054 if (ConstantInt *CB =
6055 dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
6056 R1->getValue(), R2->getValue()))) {
6057 if (CB->getZExtValue() == false)
6058 std::swap(R1, R2); // R1 is the minimum root now.
6060 // Make sure the root is not off by one. The returned iteration should
6061 // not be in the range, but the previous one should be. When solving
6062 // for "X*X < 5", for example, we should not return a root of 2.
6063 ConstantInt *R1Val = EvaluateConstantChrecAtConstant(this,
6066 if (Range.contains(R1Val->getValue())) {
6067 // The next iteration must be out of the range...
6068 ConstantInt *NextVal =
6069 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()+1);
6071 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
6072 if (!Range.contains(R1Val->getValue()))
6073 return SE.getConstant(NextVal);
6074 return SE.getCouldNotCompute(); // Something strange happened
6077 // If R1 was not in the range, then it is a good return value. Make
6078 // sure that R1-1 WAS in the range though, just in case.
6079 ConstantInt *NextVal =
6080 ConstantInt::get(SE.getContext(), R1->getValue()->getValue()-1);
6081 R1Val = EvaluateConstantChrecAtConstant(this, NextVal, SE);
6082 if (Range.contains(R1Val->getValue()))
6084 return SE.getCouldNotCompute(); // Something strange happened
6089 return SE.getCouldNotCompute();
6094 //===----------------------------------------------------------------------===//
6095 // SCEVCallbackVH Class Implementation
6096 //===----------------------------------------------------------------------===//
6098 void ScalarEvolution::SCEVCallbackVH::deleted() {
6099 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
6100 if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
6101 SE->ConstantEvolutionLoopExitValue.erase(PN);
6102 SE->ValueExprMap.erase(getValPtr());
6103 // this now dangles!
6106 void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
6107 assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
6109 // Forget all the expressions associated with users of the old value,
6110 // so that future queries will recompute the expressions using the new
6112 Value *Old = getValPtr();
6113 SmallVector<User *, 16> Worklist;
6114 SmallPtrSet<User *, 8> Visited;
6115 for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
6117 Worklist.push_back(*UI);
6118 while (!Worklist.empty()) {
6119 User *U = Worklist.pop_back_val();
6120 // Deleting the Old value will cause this to dangle. Postpone
6121 // that until everything else is done.
6124 if (!Visited.insert(U))
6126 if (PHINode *PN = dyn_cast<PHINode>(U))
6127 SE->ConstantEvolutionLoopExitValue.erase(PN);
6128 SE->ValueExprMap.erase(U);
6129 for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
6131 Worklist.push_back(*UI);
6133 // Delete the Old value.
6134 if (PHINode *PN = dyn_cast<PHINode>(Old))
6135 SE->ConstantEvolutionLoopExitValue.erase(PN);
6136 SE->ValueExprMap.erase(Old);
6137 // this now dangles!
6140 ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
6141 : CallbackVH(V), SE(se) {}
6143 //===----------------------------------------------------------------------===//
6144 // ScalarEvolution Class Implementation
6145 //===----------------------------------------------------------------------===//
6147 ScalarEvolution::ScalarEvolution()
6148 : FunctionPass(ID), FirstUnknown(0) {
6149 initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
6152 bool ScalarEvolution::runOnFunction(Function &F) {
6154 LI = &getAnalysis<LoopInfo>();
6155 TD = getAnalysisIfAvailable<TargetData>();
6156 DT = &getAnalysis<DominatorTree>();
6160 void ScalarEvolution::releaseMemory() {
6161 // Iterate through all the SCEVUnknown instances and call their
6162 // destructors, so that they release their references to their values.
6163 for (SCEVUnknown *U = FirstUnknown; U; U = U->Next)
6167 ValueExprMap.clear();
6169 // Free any extra memory created for ExitNotTakenInfo in the unlikely event
6170 // that a loop had multiple computable exits.
6171 for (DenseMap<const Loop*, BackedgeTakenInfo>::iterator I =
6172 BackedgeTakenCounts.begin(), E = BackedgeTakenCounts.end();
6177 BackedgeTakenCounts.clear();
6178 ConstantEvolutionLoopExitValue.clear();
6179 ValuesAtScopes.clear();
6180 LoopDispositions.clear();
6181 BlockDispositions.clear();
6182 UnsignedRanges.clear();
6183 SignedRanges.clear();
6184 UniqueSCEVs.clear();
6185 SCEVAllocator.Reset();
6188 void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {
6189 AU.setPreservesAll();
6190 AU.addRequiredTransitive<LoopInfo>();
6191 AU.addRequiredTransitive<DominatorTree>();
6194 bool ScalarEvolution::hasLoopInvariantBackedgeTakenCount(const Loop *L) {
6195 return !isa<SCEVCouldNotCompute>(getBackedgeTakenCount(L));
6198 static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
6200 // Print all inner loops first
6201 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
6202 PrintLoopInfo(OS, SE, *I);
6205 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6208 SmallVector<BasicBlock *, 8> ExitBlocks;
6209 L->getExitBlocks(ExitBlocks);
6210 if (ExitBlocks.size() != 1)
6211 OS << "<multiple exits> ";
6213 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
6214 OS << "backedge-taken count is " << *SE->getBackedgeTakenCount(L);
6216 OS << "Unpredictable backedge-taken count. ";
6221 WriteAsOperand(OS, L->getHeader(), /*PrintType=*/false);
6224 if (!isa<SCEVCouldNotCompute>(SE->getMaxBackedgeTakenCount(L))) {
6225 OS << "max backedge-taken count is " << *SE->getMaxBackedgeTakenCount(L);
6227 OS << "Unpredictable max backedge-taken count. ";
6233 void ScalarEvolution::print(raw_ostream &OS, const Module *) const {
6234 // ScalarEvolution's implementation of the print method is to print
6235 // out SCEV values of all instructions that are interesting. Doing
6236 // this potentially causes it to create new SCEV objects though,
6237 // which technically conflicts with the const qualifier. This isn't
6238 // observable from outside the class though, so casting away the
6239 // const isn't dangerous.
6240 ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
6242 OS << "Classifying expressions for: ";
6243 WriteAsOperand(OS, F, /*PrintType=*/false);
6245 for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
6246 if (isSCEVable(I->getType()) && !isa<CmpInst>(*I)) {
6249 const SCEV *SV = SE.getSCEV(&*I);
6252 const Loop *L = LI->getLoopFor((*I).getParent());
6254 const SCEV *AtUse = SE.getSCEVAtScope(SV, L);
6261 OS << "\t\t" "Exits: ";
6262 const SCEV *ExitValue = SE.getSCEVAtScope(SV, L->getParentLoop());
6263 if (!SE.isLoopInvariant(ExitValue, L)) {
6264 OS << "<<Unknown>>";
6273 OS << "Determining loop execution counts for: ";
6274 WriteAsOperand(OS, F, /*PrintType=*/false);
6276 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
6277 PrintLoopInfo(OS, &SE, *I);
6280 ScalarEvolution::LoopDisposition
6281 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
6282 std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
6283 std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
6284 Values.insert(std::make_pair(L, LoopVariant));
6286 return Pair.first->second;
6288 LoopDisposition D = computeLoopDisposition(S, L);
6289 return LoopDispositions[S][L] = D;
6292 ScalarEvolution::LoopDisposition
6293 ScalarEvolution::computeLoopDisposition(const SCEV *S, const Loop *L) {
6294 switch (S->getSCEVType()) {
6296 return LoopInvariant;
6300 return getLoopDisposition(cast<SCEVCastExpr>(S)->getOperand(), L);
6301 case scAddRecExpr: {
6302 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6304 // If L is the addrec's loop, it's computable.
6305 if (AR->getLoop() == L)
6306 return LoopComputable;
6308 // Add recurrences are never invariant in the function-body (null loop).
6312 // This recurrence is variant w.r.t. L if L contains AR's loop.
6313 if (L->contains(AR->getLoop()))
6316 // This recurrence is invariant w.r.t. L if AR's loop contains L.
6317 if (AR->getLoop()->contains(L))
6318 return LoopInvariant;
6320 // This recurrence is variant w.r.t. L if any of its operands
6322 for (SCEVAddRecExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
6324 if (!isLoopInvariant(*I, L))
6327 // Otherwise it's loop-invariant.
6328 return LoopInvariant;
6334 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6335 bool HasVarying = false;
6336 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6338 LoopDisposition D = getLoopDisposition(*I, L);
6339 if (D == LoopVariant)
6341 if (D == LoopComputable)
6344 return HasVarying ? LoopComputable : LoopInvariant;
6347 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6348 LoopDisposition LD = getLoopDisposition(UDiv->getLHS(), L);
6349 if (LD == LoopVariant)
6351 LoopDisposition RD = getLoopDisposition(UDiv->getRHS(), L);
6352 if (RD == LoopVariant)
6354 return (LD == LoopInvariant && RD == LoopInvariant) ?
6355 LoopInvariant : LoopComputable;
6358 // All non-instruction values are loop invariant. All instructions are loop
6359 // invariant if they are not contained in the specified loop.
6360 // Instructions are never considered invariant in the function body
6361 // (null loop) because they are defined within the "loop".
6362 if (Instruction *I = dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue()))
6363 return (L && !L->contains(I)) ? LoopInvariant : LoopVariant;
6364 return LoopInvariant;
6365 case scCouldNotCompute:
6366 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6370 llvm_unreachable("Unknown SCEV kind!");
6374 bool ScalarEvolution::isLoopInvariant(const SCEV *S, const Loop *L) {
6375 return getLoopDisposition(S, L) == LoopInvariant;
6378 bool ScalarEvolution::hasComputableLoopEvolution(const SCEV *S, const Loop *L) {
6379 return getLoopDisposition(S, L) == LoopComputable;
6382 ScalarEvolution::BlockDisposition
6383 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6384 std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
6385 std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
6386 Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
6388 return Pair.first->second;
6390 BlockDisposition D = computeBlockDisposition(S, BB);
6391 return BlockDispositions[S][BB] = D;
6394 ScalarEvolution::BlockDisposition
6395 ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
6396 switch (S->getSCEVType()) {
6398 return ProperlyDominatesBlock;
6402 return getBlockDisposition(cast<SCEVCastExpr>(S)->getOperand(), BB);
6403 case scAddRecExpr: {
6404 // This uses a "dominates" query instead of "properly dominates" query
6405 // to test for proper dominance too, because the instruction which
6406 // produces the addrec's value is a PHI, and a PHI effectively properly
6407 // dominates its entire containing block.
6408 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
6409 if (!DT->dominates(AR->getLoop()->getHeader(), BB))
6410 return DoesNotDominateBlock;
6412 // FALL THROUGH into SCEVNAryExpr handling.
6417 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6419 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6421 BlockDisposition D = getBlockDisposition(*I, BB);
6422 if (D == DoesNotDominateBlock)
6423 return DoesNotDominateBlock;
6424 if (D == DominatesBlock)
6427 return Proper ? ProperlyDominatesBlock : DominatesBlock;
6430 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6431 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6432 BlockDisposition LD = getBlockDisposition(LHS, BB);
6433 if (LD == DoesNotDominateBlock)
6434 return DoesNotDominateBlock;
6435 BlockDisposition RD = getBlockDisposition(RHS, BB);
6436 if (RD == DoesNotDominateBlock)
6437 return DoesNotDominateBlock;
6438 return (LD == ProperlyDominatesBlock && RD == ProperlyDominatesBlock) ?
6439 ProperlyDominatesBlock : DominatesBlock;
6442 if (Instruction *I =
6443 dyn_cast<Instruction>(cast<SCEVUnknown>(S)->getValue())) {
6444 if (I->getParent() == BB)
6445 return DominatesBlock;
6446 if (DT->properlyDominates(I->getParent(), BB))
6447 return ProperlyDominatesBlock;
6448 return DoesNotDominateBlock;
6450 return ProperlyDominatesBlock;
6451 case scCouldNotCompute:
6452 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6453 return DoesNotDominateBlock;
6456 llvm_unreachable("Unknown SCEV kind!");
6457 return DoesNotDominateBlock;
6460 bool ScalarEvolution::dominates(const SCEV *S, const BasicBlock *BB) {
6461 return getBlockDisposition(S, BB) >= DominatesBlock;
6464 bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
6465 return getBlockDisposition(S, BB) == ProperlyDominatesBlock;
6468 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
6469 switch (S->getSCEVType()) {
6474 case scSignExtend: {
6475 const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
6476 const SCEV *CastOp = Cast->getOperand();
6477 return Op == CastOp || hasOperand(CastOp, Op);
6484 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
6485 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
6487 const SCEV *NAryOp = *I;
6488 if (NAryOp == Op || hasOperand(NAryOp, Op))
6494 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
6495 const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
6496 return LHS == Op || hasOperand(LHS, Op) ||
6497 RHS == Op || hasOperand(RHS, Op);
6501 case scCouldNotCompute:
6502 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
6506 llvm_unreachable("Unknown SCEV kind!");
6510 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
6511 ValuesAtScopes.erase(S);
6512 LoopDispositions.erase(S);
6513 BlockDispositions.erase(S);
6514 UnsignedRanges.erase(S);
6515 SignedRanges.erase(S);