1 //===- ScalarEvolutionExpander.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 expander,
11 // which is used to generate the code corresponding to a given scalar evolution
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Analysis/ScalarEvolutionExpander.h"
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/IntrinsicInst.h"
19 #include "llvm/LLVMContext.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Target/TargetData.h"
22 #include "llvm/ADT/STLExtras.h"
26 /// ReuseOrCreateCast - Arrange for there to be a cast of V to Ty at IP,
27 /// reusing an existing cast if a suitable one exists, moving an existing
28 /// cast if a suitable one exists but isn't in the right place, or
29 /// creating a new one.
30 Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
31 Instruction::CastOps Op,
32 BasicBlock::iterator IP) {
33 // Check to see if there is already a cast!
34 for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
37 if (U->getType() == Ty)
38 if (CastInst *CI = dyn_cast<CastInst>(U))
39 if (CI->getOpcode() == Op) {
40 // If the cast isn't where we want it, fix it.
41 if (BasicBlock::iterator(CI) != IP) {
42 // Create a new cast, and leave the old cast in place in case
43 // it is being used as an insert point. Clear its operand
44 // so that it doesn't hold anything live.
45 Instruction *NewCI = CastInst::Create(Op, V, Ty, "", IP);
47 CI->replaceAllUsesWith(NewCI);
48 CI->setOperand(0, UndefValue::get(V->getType()));
49 rememberInstruction(NewCI);
52 rememberInstruction(CI);
58 Instruction *I = CastInst::Create(Op, V, Ty, V->getName(), IP);
59 rememberInstruction(I);
63 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
64 /// which must be possible with a noop cast, doing what we can to share
66 Value *SCEVExpander::InsertNoopCastOfTo(Value *V, Type *Ty) {
67 Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
68 assert((Op == Instruction::BitCast ||
69 Op == Instruction::PtrToInt ||
70 Op == Instruction::IntToPtr) &&
71 "InsertNoopCastOfTo cannot perform non-noop casts!");
72 assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
73 "InsertNoopCastOfTo cannot change sizes!");
75 // Short-circuit unnecessary bitcasts.
76 if (Op == Instruction::BitCast) {
77 if (V->getType() == Ty)
79 if (CastInst *CI = dyn_cast<CastInst>(V)) {
80 if (CI->getOperand(0)->getType() == Ty)
81 return CI->getOperand(0);
84 // Short-circuit unnecessary inttoptr<->ptrtoint casts.
85 if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) &&
86 SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
87 if (CastInst *CI = dyn_cast<CastInst>(V))
88 if ((CI->getOpcode() == Instruction::PtrToInt ||
89 CI->getOpcode() == Instruction::IntToPtr) &&
90 SE.getTypeSizeInBits(CI->getType()) ==
91 SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
92 return CI->getOperand(0);
93 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
94 if ((CE->getOpcode() == Instruction::PtrToInt ||
95 CE->getOpcode() == Instruction::IntToPtr) &&
96 SE.getTypeSizeInBits(CE->getType()) ==
97 SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
98 return CE->getOperand(0);
101 // Fold a cast of a constant.
102 if (Constant *C = dyn_cast<Constant>(V))
103 return ConstantExpr::getCast(Op, C, Ty);
105 // Cast the argument at the beginning of the entry block, after
106 // any bitcasts of other arguments.
107 if (Argument *A = dyn_cast<Argument>(V)) {
108 BasicBlock::iterator IP = A->getParent()->getEntryBlock().begin();
109 while ((isa<BitCastInst>(IP) &&
110 isa<Argument>(cast<BitCastInst>(IP)->getOperand(0)) &&
111 cast<BitCastInst>(IP)->getOperand(0) != A) ||
112 isa<DbgInfoIntrinsic>(IP) ||
113 isa<LandingPadInst>(IP))
115 return ReuseOrCreateCast(A, Ty, Op, IP);
118 // Cast the instruction immediately after the instruction.
119 Instruction *I = cast<Instruction>(V);
120 BasicBlock::iterator IP = I; ++IP;
121 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
122 IP = II->getNormalDest()->begin();
123 while (isa<PHINode>(IP) || isa<DbgInfoIntrinsic>(IP) ||
124 isa<LandingPadInst>(IP))
126 return ReuseOrCreateCast(I, Ty, Op, IP);
129 /// InsertBinop - Insert the specified binary operator, doing a small amount
130 /// of work to avoid inserting an obviously redundant operation.
131 Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode,
132 Value *LHS, Value *RHS) {
133 // Fold a binop with constant operands.
134 if (Constant *CLHS = dyn_cast<Constant>(LHS))
135 if (Constant *CRHS = dyn_cast<Constant>(RHS))
136 return ConstantExpr::get(Opcode, CLHS, CRHS);
138 // Do a quick scan to see if we have this binop nearby. If so, reuse it.
139 unsigned ScanLimit = 6;
140 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
141 // Scanning starts from the last instruction before the insertion point.
142 BasicBlock::iterator IP = Builder.GetInsertPoint();
143 if (IP != BlockBegin) {
145 for (; ScanLimit; --IP, --ScanLimit) {
146 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
148 if (isa<DbgInfoIntrinsic>(IP))
150 if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
151 IP->getOperand(1) == RHS)
153 if (IP == BlockBegin) break;
157 // Save the original insertion point so we can restore it when we're done.
158 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
159 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
161 // Move the insertion point out of as many loops as we can.
162 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
163 if (!L->isLoopInvariant(LHS) || !L->isLoopInvariant(RHS)) break;
164 BasicBlock *Preheader = L->getLoopPreheader();
165 if (!Preheader) break;
167 // Ok, move up a level.
168 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
171 // If we haven't found this binop, insert it.
172 Instruction *BO = cast<Instruction>(Builder.CreateBinOp(Opcode, LHS, RHS));
173 BO->setDebugLoc(SaveInsertPt->getDebugLoc());
174 rememberInstruction(BO);
176 // Restore the original insert point.
178 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
183 /// FactorOutConstant - Test if S is divisible by Factor, using signed
184 /// division. If so, update S with Factor divided out and return true.
185 /// S need not be evenly divisible if a reasonable remainder can be
187 /// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
188 /// unnecessary; in its place, just signed-divide Ops[i] by the scale and
189 /// check to see if the divide was folded.
190 static bool FactorOutConstant(const SCEV *&S,
191 const SCEV *&Remainder,
194 const TargetData *TD) {
195 // Everything is divisible by one.
201 S = SE.getConstant(S->getType(), 1);
205 // For a Constant, check for a multiple of the given factor.
206 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
210 // Check for divisibility.
211 if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) {
213 ConstantInt::get(SE.getContext(),
214 C->getValue()->getValue().sdiv(
215 FC->getValue()->getValue()));
216 // If the quotient is zero and the remainder is non-zero, reject
217 // the value at this scale. It will be considered for subsequent
220 const SCEV *Div = SE.getConstant(CI);
223 SE.getAddExpr(Remainder,
224 SE.getConstant(C->getValue()->getValue().srem(
225 FC->getValue()->getValue())));
231 // In a Mul, check if there is a constant operand which is a multiple
232 // of the given factor.
233 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
235 // With TargetData, the size is known. Check if there is a constant
236 // operand which is a multiple of the given factor. If so, we can
238 const SCEVConstant *FC = cast<SCEVConstant>(Factor);
239 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
240 if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) {
241 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
243 SE.getConstant(C->getValue()->getValue().sdiv(
244 FC->getValue()->getValue()));
245 S = SE.getMulExpr(NewMulOps);
249 // Without TargetData, check if Factor can be factored out of any of the
250 // Mul's operands. If so, we can just remove it.
251 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
252 const SCEV *SOp = M->getOperand(i);
253 const SCEV *Remainder = SE.getConstant(SOp->getType(), 0);
254 if (FactorOutConstant(SOp, Remainder, Factor, SE, TD) &&
255 Remainder->isZero()) {
256 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
258 S = SE.getMulExpr(NewMulOps);
265 // In an AddRec, check if both start and step are divisible.
266 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
267 const SCEV *Step = A->getStepRecurrence(SE);
268 const SCEV *StepRem = SE.getConstant(Step->getType(), 0);
269 if (!FactorOutConstant(Step, StepRem, Factor, SE, TD))
271 if (!StepRem->isZero())
273 const SCEV *Start = A->getStart();
274 if (!FactorOutConstant(Start, Remainder, Factor, SE, TD))
276 // FIXME: can use A->getNoWrapFlags(FlagNW)
277 S = SE.getAddRecExpr(Start, Step, A->getLoop(), SCEV::FlagAnyWrap);
284 /// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs
285 /// is the number of SCEVAddRecExprs present, which are kept at the end of
288 static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops,
290 ScalarEvolution &SE) {
291 unsigned NumAddRecs = 0;
292 for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i)
294 // Group Ops into non-addrecs and addrecs.
295 SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs);
296 SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end());
297 // Let ScalarEvolution sort and simplify the non-addrecs list.
298 const SCEV *Sum = NoAddRecs.empty() ?
299 SE.getConstant(Ty, 0) :
300 SE.getAddExpr(NoAddRecs);
301 // If it returned an add, use the operands. Otherwise it simplified
302 // the sum into a single value, so just use that.
304 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum))
305 Ops.append(Add->op_begin(), Add->op_end());
306 else if (!Sum->isZero())
308 // Then append the addrecs.
309 Ops.append(AddRecs.begin(), AddRecs.end());
312 /// SplitAddRecs - Flatten a list of add operands, moving addrec start values
313 /// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}.
314 /// This helps expose more opportunities for folding parts of the expressions
315 /// into GEP indices.
317 static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops,
319 ScalarEvolution &SE) {
321 SmallVector<const SCEV *, 8> AddRecs;
322 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
323 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) {
324 const SCEV *Start = A->getStart();
325 if (Start->isZero()) break;
326 const SCEV *Zero = SE.getConstant(Ty, 0);
327 AddRecs.push_back(SE.getAddRecExpr(Zero,
328 A->getStepRecurrence(SE),
330 // FIXME: A->getNoWrapFlags(FlagNW)
332 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
334 Ops.append(Add->op_begin(), Add->op_end());
335 e += Add->getNumOperands();
340 if (!AddRecs.empty()) {
341 // Add the addrecs onto the end of the list.
342 Ops.append(AddRecs.begin(), AddRecs.end());
343 // Resort the operand list, moving any constants to the front.
344 SimplifyAddOperands(Ops, Ty, SE);
348 /// expandAddToGEP - Expand an addition expression with a pointer type into
349 /// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps
350 /// BasicAliasAnalysis and other passes analyze the result. See the rules
351 /// for getelementptr vs. inttoptr in
352 /// http://llvm.org/docs/LangRef.html#pointeraliasing
355 /// Design note: The correctness of using getelementptr here depends on
356 /// ScalarEvolution not recognizing inttoptr and ptrtoint operators, as
357 /// they may introduce pointer arithmetic which may not be safely converted
358 /// into getelementptr.
360 /// Design note: It might seem desirable for this function to be more
361 /// loop-aware. If some of the indices are loop-invariant while others
362 /// aren't, it might seem desirable to emit multiple GEPs, keeping the
363 /// loop-invariant portions of the overall computation outside the loop.
364 /// However, there are a few reasons this is not done here. Hoisting simple
365 /// arithmetic is a low-level optimization that often isn't very
366 /// important until late in the optimization process. In fact, passes
367 /// like InstructionCombining will combine GEPs, even if it means
368 /// pushing loop-invariant computation down into loops, so even if the
369 /// GEPs were split here, the work would quickly be undone. The
370 /// LoopStrengthReduction pass, which is usually run quite late (and
371 /// after the last InstructionCombining pass), takes care of hoisting
372 /// loop-invariant portions of expressions, after considering what
373 /// can be folded using target addressing modes.
375 Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
376 const SCEV *const *op_end,
380 Type *ElTy = PTy->getElementType();
381 SmallVector<Value *, 4> GepIndices;
382 SmallVector<const SCEV *, 8> Ops(op_begin, op_end);
383 bool AnyNonZeroIndices = false;
385 // Split AddRecs up into parts as either of the parts may be usable
386 // without the other.
387 SplitAddRecs(Ops, Ty, SE);
389 // Descend down the pointer's type and attempt to convert the other
390 // operands into GEP indices, at each level. The first index in a GEP
391 // indexes into the array implied by the pointer operand; the rest of
392 // the indices index into the element or field type selected by the
395 // If the scale size is not 0, attempt to factor out a scale for
397 SmallVector<const SCEV *, 8> ScaledOps;
398 if (ElTy->isSized()) {
399 const SCEV *ElSize = SE.getSizeOfExpr(ElTy);
400 if (!ElSize->isZero()) {
401 SmallVector<const SCEV *, 8> NewOps;
402 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
403 const SCEV *Op = Ops[i];
404 const SCEV *Remainder = SE.getConstant(Ty, 0);
405 if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.TD)) {
406 // Op now has ElSize factored out.
407 ScaledOps.push_back(Op);
408 if (!Remainder->isZero())
409 NewOps.push_back(Remainder);
410 AnyNonZeroIndices = true;
412 // The operand was not divisible, so add it to the list of operands
413 // we'll scan next iteration.
414 NewOps.push_back(Ops[i]);
417 // If we made any changes, update Ops.
418 if (!ScaledOps.empty()) {
420 SimplifyAddOperands(Ops, Ty, SE);
425 // Record the scaled array index for this level of the type. If
426 // we didn't find any operands that could be factored, tentatively
427 // assume that element zero was selected (since the zero offset
428 // would obviously be folded away).
429 Value *Scaled = ScaledOps.empty() ?
430 Constant::getNullValue(Ty) :
431 expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
432 GepIndices.push_back(Scaled);
434 // Collect struct field index operands.
435 while (StructType *STy = dyn_cast<StructType>(ElTy)) {
436 bool FoundFieldNo = false;
437 // An empty struct has no fields.
438 if (STy->getNumElements() == 0) break;
440 // With TargetData, field offsets are known. See if a constant offset
441 // falls within any of the struct fields.
442 if (Ops.empty()) break;
443 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
444 if (SE.getTypeSizeInBits(C->getType()) <= 64) {
445 const StructLayout &SL = *SE.TD->getStructLayout(STy);
446 uint64_t FullOffset = C->getValue()->getZExtValue();
447 if (FullOffset < SL.getSizeInBytes()) {
448 unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
449 GepIndices.push_back(
450 ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx));
451 ElTy = STy->getTypeAtIndex(ElIdx);
453 SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx));
454 AnyNonZeroIndices = true;
459 // Without TargetData, just check for an offsetof expression of the
460 // appropriate struct type.
461 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
462 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i])) {
465 if (U->isOffsetOf(CTy, FieldNo) && CTy == STy) {
466 GepIndices.push_back(FieldNo);
468 STy->getTypeAtIndex(cast<ConstantInt>(FieldNo)->getZExtValue());
469 Ops[i] = SE.getConstant(Ty, 0);
470 AnyNonZeroIndices = true;
476 // If no struct field offsets were found, tentatively assume that
477 // field zero was selected (since the zero offset would obviously
480 ElTy = STy->getTypeAtIndex(0u);
481 GepIndices.push_back(
482 Constant::getNullValue(Type::getInt32Ty(Ty->getContext())));
486 if (ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
487 ElTy = ATy->getElementType();
492 // If none of the operands were convertible to proper GEP indices, cast
493 // the base to i8* and do an ugly getelementptr with that. It's still
494 // better than ptrtoint+arithmetic+inttoptr at least.
495 if (!AnyNonZeroIndices) {
496 // Cast the base to i8*.
497 V = InsertNoopCastOfTo(V,
498 Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
500 // Expand the operands for a plain byte offset.
501 Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
503 // Fold a GEP with constant operands.
504 if (Constant *CLHS = dyn_cast<Constant>(V))
505 if (Constant *CRHS = dyn_cast<Constant>(Idx))
506 return ConstantExpr::getGetElementPtr(CLHS, CRHS);
508 // Do a quick scan to see if we have this GEP nearby. If so, reuse it.
509 unsigned ScanLimit = 6;
510 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
511 // Scanning starts from the last instruction before the insertion point.
512 BasicBlock::iterator IP = Builder.GetInsertPoint();
513 if (IP != BlockBegin) {
515 for (; ScanLimit; --IP, --ScanLimit) {
516 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
518 if (isa<DbgInfoIntrinsic>(IP))
520 if (IP->getOpcode() == Instruction::GetElementPtr &&
521 IP->getOperand(0) == V && IP->getOperand(1) == Idx)
523 if (IP == BlockBegin) break;
527 // Save the original insertion point so we can restore it when we're done.
528 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
529 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
531 // Move the insertion point out of as many loops as we can.
532 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
533 if (!L->isLoopInvariant(V) || !L->isLoopInvariant(Idx)) break;
534 BasicBlock *Preheader = L->getLoopPreheader();
535 if (!Preheader) break;
537 // Ok, move up a level.
538 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
542 Value *GEP = Builder.CreateGEP(V, Idx, "uglygep");
543 rememberInstruction(GEP);
545 // Restore the original insert point.
547 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
552 // Save the original insertion point so we can restore it when we're done.
553 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
554 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
556 // Move the insertion point out of as many loops as we can.
557 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
558 if (!L->isLoopInvariant(V)) break;
560 bool AnyIndexNotLoopInvariant = false;
561 for (SmallVectorImpl<Value *>::const_iterator I = GepIndices.begin(),
562 E = GepIndices.end(); I != E; ++I)
563 if (!L->isLoopInvariant(*I)) {
564 AnyIndexNotLoopInvariant = true;
567 if (AnyIndexNotLoopInvariant)
570 BasicBlock *Preheader = L->getLoopPreheader();
571 if (!Preheader) break;
573 // Ok, move up a level.
574 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
577 // Insert a pretty getelementptr. Note that this GEP is not marked inbounds,
578 // because ScalarEvolution may have changed the address arithmetic to
579 // compute a value which is beyond the end of the allocated object.
581 if (V->getType() != PTy)
582 Casted = InsertNoopCastOfTo(Casted, PTy);
583 Value *GEP = Builder.CreateGEP(Casted,
586 Ops.push_back(SE.getUnknown(GEP));
587 rememberInstruction(GEP);
589 // Restore the original insert point.
591 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
593 return expand(SE.getAddExpr(Ops));
596 /// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
597 /// SCEV expansion. If they are nested, this is the most nested. If they are
598 /// neighboring, pick the later.
599 static const Loop *PickMostRelevantLoop(const Loop *A, const Loop *B,
603 if (A->contains(B)) return B;
604 if (B->contains(A)) return A;
605 if (DT.dominates(A->getHeader(), B->getHeader())) return B;
606 if (DT.dominates(B->getHeader(), A->getHeader())) return A;
607 return A; // Arbitrarily break the tie.
610 /// getRelevantLoop - Get the most relevant loop associated with the given
611 /// expression, according to PickMostRelevantLoop.
612 const Loop *SCEVExpander::getRelevantLoop(const SCEV *S) {
613 // Test whether we've already computed the most relevant loop for this SCEV.
614 std::pair<DenseMap<const SCEV *, const Loop *>::iterator, bool> Pair =
615 RelevantLoops.insert(std::make_pair(S, static_cast<const Loop *>(0)));
617 return Pair.first->second;
619 if (isa<SCEVConstant>(S))
620 // A constant has no relevant loops.
622 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
623 if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
624 return Pair.first->second = SE.LI->getLoopFor(I->getParent());
625 // A non-instruction has no relevant loops.
628 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
630 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
632 for (SCEVNAryExpr::op_iterator I = N->op_begin(), E = N->op_end();
634 L = PickMostRelevantLoop(L, getRelevantLoop(*I), *SE.DT);
635 return RelevantLoops[N] = L;
637 if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) {
638 const Loop *Result = getRelevantLoop(C->getOperand());
639 return RelevantLoops[C] = Result;
641 if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
643 PickMostRelevantLoop(getRelevantLoop(D->getLHS()),
644 getRelevantLoop(D->getRHS()),
646 return RelevantLoops[D] = Result;
648 llvm_unreachable("Unexpected SCEV type!");
654 /// LoopCompare - Compare loops by PickMostRelevantLoop.
658 explicit LoopCompare(DominatorTree &dt) : DT(dt) {}
660 bool operator()(std::pair<const Loop *, const SCEV *> LHS,
661 std::pair<const Loop *, const SCEV *> RHS) const {
662 // Keep pointer operands sorted at the end.
663 if (LHS.second->getType()->isPointerTy() !=
664 RHS.second->getType()->isPointerTy())
665 return LHS.second->getType()->isPointerTy();
667 // Compare loops with PickMostRelevantLoop.
668 if (LHS.first != RHS.first)
669 return PickMostRelevantLoop(LHS.first, RHS.first, DT) != LHS.first;
671 // If one operand is a non-constant negative and the other is not,
672 // put the non-constant negative on the right so that a sub can
673 // be used instead of a negate and add.
674 if (LHS.second->isNonConstantNegative()) {
675 if (!RHS.second->isNonConstantNegative())
677 } else if (RHS.second->isNonConstantNegative())
680 // Otherwise they are equivalent according to this comparison.
687 Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
688 Type *Ty = SE.getEffectiveSCEVType(S->getType());
690 // Collect all the add operands in a loop, along with their associated loops.
691 // Iterate in reverse so that constants are emitted last, all else equal, and
692 // so that pointer operands are inserted first, which the code below relies on
693 // to form more involved GEPs.
694 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
695 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(S->op_end()),
696 E(S->op_begin()); I != E; ++I)
697 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
699 // Sort by loop. Use a stable sort so that constants follow non-constants and
700 // pointer operands precede non-pointer operands.
701 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
703 // Emit instructions to add all the operands. Hoist as much as possible
704 // out of loops, and form meaningful getelementptrs where possible.
706 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
707 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
708 const Loop *CurLoop = I->first;
709 const SCEV *Op = I->second;
711 // This is the first operand. Just expand it.
714 } else if (PointerType *PTy = dyn_cast<PointerType>(Sum->getType())) {
715 // The running sum expression is a pointer. Try to form a getelementptr
716 // at this level with that as the base.
717 SmallVector<const SCEV *, 4> NewOps;
718 for (; I != E && I->first == CurLoop; ++I) {
719 // If the operand is SCEVUnknown and not instructions, peek through
720 // it, to enable more of it to be folded into the GEP.
721 const SCEV *X = I->second;
722 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(X))
723 if (!isa<Instruction>(U->getValue()))
724 X = SE.getSCEV(U->getValue());
727 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
728 } else if (PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
729 // The running sum is an integer, and there's a pointer at this level.
730 // Try to form a getelementptr. If the running sum is instructions,
731 // use a SCEVUnknown to avoid re-analyzing them.
732 SmallVector<const SCEV *, 4> NewOps;
733 NewOps.push_back(isa<Instruction>(Sum) ? SE.getUnknown(Sum) :
735 for (++I; I != E && I->first == CurLoop; ++I)
736 NewOps.push_back(I->second);
737 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
738 } else if (Op->isNonConstantNegative()) {
739 // Instead of doing a negate and add, just do a subtract.
740 Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
741 Sum = InsertNoopCastOfTo(Sum, Ty);
742 Sum = InsertBinop(Instruction::Sub, Sum, W);
746 Value *W = expandCodeFor(Op, Ty);
747 Sum = InsertNoopCastOfTo(Sum, Ty);
748 // Canonicalize a constant to the RHS.
749 if (isa<Constant>(Sum)) std::swap(Sum, W);
750 Sum = InsertBinop(Instruction::Add, Sum, W);
758 Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
759 Type *Ty = SE.getEffectiveSCEVType(S->getType());
761 // Collect all the mul operands in a loop, along with their associated loops.
762 // Iterate in reverse so that constants are emitted last, all else equal.
763 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
764 for (std::reverse_iterator<SCEVMulExpr::op_iterator> I(S->op_end()),
765 E(S->op_begin()); I != E; ++I)
766 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
768 // Sort by loop. Use a stable sort so that constants follow non-constants.
769 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
771 // Emit instructions to mul all the operands. Hoist as much as possible
774 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
775 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
776 const SCEV *Op = I->second;
778 // This is the first operand. Just expand it.
781 } else if (Op->isAllOnesValue()) {
782 // Instead of doing a multiply by negative one, just do a negate.
783 Prod = InsertNoopCastOfTo(Prod, Ty);
784 Prod = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), Prod);
788 Value *W = expandCodeFor(Op, Ty);
789 Prod = InsertNoopCastOfTo(Prod, Ty);
790 // Canonicalize a constant to the RHS.
791 if (isa<Constant>(Prod)) std::swap(Prod, W);
792 Prod = InsertBinop(Instruction::Mul, Prod, W);
800 Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
801 Type *Ty = SE.getEffectiveSCEVType(S->getType());
803 Value *LHS = expandCodeFor(S->getLHS(), Ty);
804 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
805 const APInt &RHS = SC->getValue()->getValue();
806 if (RHS.isPowerOf2())
807 return InsertBinop(Instruction::LShr, LHS,
808 ConstantInt::get(Ty, RHS.logBase2()));
811 Value *RHS = expandCodeFor(S->getRHS(), Ty);
812 return InsertBinop(Instruction::UDiv, LHS, RHS);
815 /// Move parts of Base into Rest to leave Base with the minimal
816 /// expression that provides a pointer operand suitable for a
818 static void ExposePointerBase(const SCEV *&Base, const SCEV *&Rest,
819 ScalarEvolution &SE) {
820 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
821 Base = A->getStart();
822 Rest = SE.getAddExpr(Rest,
823 SE.getAddRecExpr(SE.getConstant(A->getType(), 0),
824 A->getStepRecurrence(SE),
826 // FIXME: A->getNoWrapFlags(FlagNW)
829 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
830 Base = A->getOperand(A->getNumOperands()-1);
831 SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end());
832 NewAddOps.back() = Rest;
833 Rest = SE.getAddExpr(NewAddOps);
834 ExposePointerBase(Base, Rest, SE);
838 /// Determine if this is a well-behaved chain of instructions leading back to
839 /// the PHI. If so, it may be reused by expanded expressions.
840 bool SCEVExpander::isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV,
842 if (IncV->getNumOperands() == 0 || isa<PHINode>(IncV) ||
843 (isa<CastInst>(IncV) && !isa<BitCastInst>(IncV)))
845 // If any of the operands don't dominate the insert position, bail.
846 // Addrec operands are always loop-invariant, so this can only happen
847 // if there are instructions which haven't been hoisted.
848 if (L == IVIncInsertLoop) {
849 for (User::op_iterator OI = IncV->op_begin()+1,
850 OE = IncV->op_end(); OI != OE; ++OI)
851 if (Instruction *OInst = dyn_cast<Instruction>(OI))
852 if (!SE.DT->dominates(OInst, IVIncInsertPos))
855 // Advance to the next instruction.
856 IncV = dyn_cast<Instruction>(IncV->getOperand(0));
860 if (IncV->mayHaveSideEffects())
866 return isNormalAddRecExprPHI(PN, IncV, L);
869 /// Determine if this cyclic phi is in a form that would have been generated by
870 /// LSR. We don't care if the phi was actually expanded in this pass, as long
871 /// as it is in a low-cost form, for example, no implied multiplication. This
872 /// should match any patterns generated by getAddRecExprPHILiterally and
874 bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
876 switch (IncV->getOpcode()) {
877 // Check for a simple Add/Sub or GEP of a loop invariant step.
878 case Instruction::Add:
879 case Instruction::Sub:
880 return IncV->getOperand(0) == PN
881 && L->isLoopInvariant(IncV->getOperand(1));
882 case Instruction::BitCast:
883 IncV = dyn_cast<GetElementPtrInst>(IncV->getOperand(0));
886 // fall-thru to GEP handling
887 case Instruction::GetElementPtr: {
888 // This must be a pointer addition of constants (pretty) or some number of
889 // address-size elements (ugly).
890 for (Instruction::op_iterator I = IncV->op_begin()+1, E = IncV->op_end();
892 if (isa<Constant>(*I))
894 // ugly geps have 2 operands.
895 // i1* is used by the expander to represent an address-size element.
896 if (IncV->getNumOperands() != 2)
898 unsigned AS = cast<PointerType>(IncV->getType())->getAddressSpace();
899 if (IncV->getType() != Type::getInt1PtrTy(SE.getContext(), AS)
900 && IncV->getType() != Type::getInt8PtrTy(SE.getContext(), AS))
902 // Ensure the operands dominate the insertion point. I don't know of a
903 // case when this would not be true, so this is somewhat untested.
904 if (L == IVIncInsertLoop) {
905 for (User::op_iterator OI = IncV->op_begin()+1,
906 OE = IncV->op_end(); OI != OE; ++OI)
907 if (Instruction *OInst = dyn_cast<Instruction>(OI))
908 if (!SE.DT->dominates(OInst, IVIncInsertPos))
913 IncV = dyn_cast<Instruction>(IncV->getOperand(0));
914 if (IncV && IncV->getOpcode() == Instruction::BitCast)
915 IncV = dyn_cast<Instruction>(IncV->getOperand(0));
923 /// expandIVInc - Expand an IV increment at Builder's current InsertPos.
924 /// Typically this is the LatchBlock terminator or IVIncInsertPos, but we may
925 /// need to materialize IV increments elsewhere to handle difficult situations.
926 Value *SCEVExpander::expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
927 Type *ExpandTy, Type *IntTy,
930 // If the PHI is a pointer, use a GEP, otherwise use an add or sub.
931 if (ExpandTy->isPointerTy()) {
932 PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
933 // If the step isn't constant, don't use an implicitly scaled GEP, because
934 // that would require a multiply inside the loop.
935 if (!isa<ConstantInt>(StepV))
936 GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
937 GEPPtrTy->getAddressSpace());
938 const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
939 IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
940 if (IncV->getType() != PN->getType()) {
941 IncV = Builder.CreateBitCast(IncV, PN->getType());
942 rememberInstruction(IncV);
946 Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
947 Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
948 rememberInstruction(IncV);
953 /// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
954 /// the base addrec, which is the addrec without any non-loop-dominating
955 /// values, and return the PHI.
957 SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
961 assert((!IVIncInsertLoop||IVIncInsertPos) && "Uninitialized insert position");
963 // Reuse a previously-inserted PHI, if present.
964 BasicBlock *LatchBlock = L->getLoopLatch();
966 for (BasicBlock::iterator I = L->getHeader()->begin();
967 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
968 if (!SE.isSCEVable(PN->getType()) ||
969 (SE.getEffectiveSCEVType(PN->getType()) !=
970 SE.getEffectiveSCEVType(Normalized->getType())) ||
971 SE.getSCEV(PN) != Normalized)
975 cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
978 if (!isExpandedAddRecExprPHI(PN, IncV, L))
982 if (!isNormalAddRecExprPHI(PN, IncV, L))
985 // Ok, the add recurrence looks usable.
986 // Remember this PHI, even in post-inc mode.
987 InsertedValues.insert(PN);
988 // Remember the increment.
989 rememberInstruction(IncV);
990 if (L == IVIncInsertLoop)
992 if (SE.DT->dominates(IncV, IVIncInsertPos))
994 // Make sure the increment is where we want it. But don't move it
995 // down past a potential existing post-inc user.
996 IncV->moveBefore(IVIncInsertPos);
997 IVIncInsertPos = IncV;
998 IncV = cast<Instruction>(IncV->getOperand(0));
999 } while (IncV != PN);
1004 // Save the original insertion point so we can restore it when we're done.
1005 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
1006 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
1008 // Another AddRec may need to be recursively expanded below. For example, if
1009 // this AddRec is quadratic, the StepV may itself be an AddRec in this
1010 // loop. Remove this loop from the PostIncLoops set before expanding such
1011 // AddRecs. Otherwise, we cannot find a valid position for the step
1012 // (i.e. StepV can never dominate its loop header). Ideally, we could do
1013 // SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
1014 // so it's not worth implementing SmallPtrSet::swap.
1015 PostIncLoopSet SavedPostIncLoops = PostIncLoops;
1016 PostIncLoops.clear();
1018 // Expand code for the start value.
1019 Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
1020 L->getHeader()->begin());
1022 // StartV must be hoisted into L's preheader to dominate the new phi.
1023 assert(!isa<Instruction>(StartV) ||
1024 SE.DT->properlyDominates(cast<Instruction>(StartV)->getParent(),
1027 // Expand code for the step value. Do this before creating the PHI so that PHI
1028 // reuse code doesn't see an incomplete PHI.
1029 const SCEV *Step = Normalized->getStepRecurrence(SE);
1030 // If the stride is negative, insert a sub instead of an add for the increment
1031 // (unless it's a constant, because subtracts of constants are canonicalized
1033 bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1035 Step = SE.getNegativeSCEV(Step);
1036 // Expand the step somewhere that dominates the loop header.
1037 Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1040 BasicBlock *Header = L->getHeader();
1041 Builder.SetInsertPoint(Header, Header->begin());
1042 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1043 PHINode *PN = Builder.CreatePHI(ExpandTy, std::distance(HPB, HPE),
1044 Twine(IVName) + ".iv");
1045 rememberInstruction(PN);
1047 // Create the step instructions and populate the PHI.
1048 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1049 BasicBlock *Pred = *HPI;
1051 // Add a start value.
1052 if (!L->contains(Pred)) {
1053 PN->addIncoming(StartV, Pred);
1057 // Create a step value and add it to the PHI.
1058 // If IVIncInsertLoop is non-null and equal to the addrec's loop, insert the
1059 // instructions at IVIncInsertPos.
1060 Instruction *InsertPos = L == IVIncInsertLoop ?
1061 IVIncInsertPos : Pred->getTerminator();
1062 Builder.SetInsertPoint(InsertPos);
1063 Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1065 PN->addIncoming(IncV, Pred);
1068 // Restore the original insert point.
1070 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
1072 // After expanding subexpressions, restore the PostIncLoops set so the caller
1073 // can ensure that IVIncrement dominates the current uses.
1074 PostIncLoops = SavedPostIncLoops;
1076 // Remember this PHI, even in post-inc mode.
1077 InsertedValues.insert(PN);
1082 Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
1083 Type *STy = S->getType();
1084 Type *IntTy = SE.getEffectiveSCEVType(STy);
1085 const Loop *L = S->getLoop();
1087 // Determine a normalized form of this expression, which is the expression
1088 // before any post-inc adjustment is made.
1089 const SCEVAddRecExpr *Normalized = S;
1090 if (PostIncLoops.count(L)) {
1091 PostIncLoopSet Loops;
1094 cast<SCEVAddRecExpr>(TransformForPostIncUse(Normalize, S, 0, 0,
1095 Loops, SE, *SE.DT));
1098 // Strip off any non-loop-dominating component from the addrec start.
1099 const SCEV *Start = Normalized->getStart();
1100 const SCEV *PostLoopOffset = 0;
1101 if (!SE.properlyDominates(Start, L->getHeader())) {
1102 PostLoopOffset = Start;
1103 Start = SE.getConstant(Normalized->getType(), 0);
1104 Normalized = cast<SCEVAddRecExpr>(
1105 SE.getAddRecExpr(Start, Normalized->getStepRecurrence(SE),
1106 Normalized->getLoop(),
1107 // FIXME: Normalized->getNoWrapFlags(FlagNW)
1108 SCEV::FlagAnyWrap));
1111 // Strip off any non-loop-dominating component from the addrec step.
1112 const SCEV *Step = Normalized->getStepRecurrence(SE);
1113 const SCEV *PostLoopScale = 0;
1114 if (!SE.dominates(Step, L->getHeader())) {
1115 PostLoopScale = Step;
1116 Step = SE.getConstant(Normalized->getType(), 1);
1118 cast<SCEVAddRecExpr>(SE.getAddRecExpr(Start, Step,
1119 Normalized->getLoop(),
1120 // FIXME: Normalized
1121 // ->getNoWrapFlags(FlagNW)
1122 SCEV::FlagAnyWrap));
1125 // Expand the core addrec. If we need post-loop scaling, force it to
1126 // expand to an integer type to avoid the need for additional casting.
1127 Type *ExpandTy = PostLoopScale ? IntTy : STy;
1128 PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy);
1130 // Accommodate post-inc mode, if necessary.
1132 if (!PostIncLoops.count(L))
1135 // In PostInc mode, use the post-incremented value.
1136 BasicBlock *LatchBlock = L->getLoopLatch();
1137 assert(LatchBlock && "PostInc mode requires a unique loop latch!");
1138 Result = PN->getIncomingValueForBlock(LatchBlock);
1140 // For an expansion to use the postinc form, the client must call
1141 // expandCodeFor with an InsertPoint that is either outside the PostIncLoop
1142 // or dominated by IVIncInsertPos.
1143 if (isa<Instruction>(Result)
1144 && !SE.DT->dominates(cast<Instruction>(Result),
1145 Builder.GetInsertPoint())) {
1146 // The induction variable's postinc expansion does not dominate this use.
1147 // IVUsers tries to prevent this case, so it is rare. However, it can
1148 // happen when an IVUser outside the loop is not dominated by the latch
1149 // block. Adjusting IVIncInsertPos before expansion begins cannot handle
1150 // all cases. Consider a phi outide whose operand is replaced during
1151 // expansion with the value of the postinc user. Without fundamentally
1152 // changing the way postinc users are tracked, the only remedy is
1153 // inserting an extra IV increment. StepV might fold into PostLoopOffset,
1154 // but hopefully expandCodeFor handles that.
1156 !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1158 Step = SE.getNegativeSCEV(Step);
1159 // Expand the step somewhere that dominates the loop header.
1160 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
1161 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
1162 Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1163 // Restore the insertion point to the place where the caller has
1164 // determined dominates all uses.
1165 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
1166 Result = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1170 // Re-apply any non-loop-dominating scale.
1171 if (PostLoopScale) {
1172 Result = InsertNoopCastOfTo(Result, IntTy);
1173 Result = Builder.CreateMul(Result,
1174 expandCodeFor(PostLoopScale, IntTy));
1175 rememberInstruction(Result);
1178 // Re-apply any non-loop-dominating offset.
1179 if (PostLoopOffset) {
1180 if (PointerType *PTy = dyn_cast<PointerType>(ExpandTy)) {
1181 const SCEV *const OffsetArray[1] = { PostLoopOffset };
1182 Result = expandAddToGEP(OffsetArray, OffsetArray+1, PTy, IntTy, Result);
1184 Result = InsertNoopCastOfTo(Result, IntTy);
1185 Result = Builder.CreateAdd(Result,
1186 expandCodeFor(PostLoopOffset, IntTy));
1187 rememberInstruction(Result);
1194 Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
1195 if (!CanonicalMode) return expandAddRecExprLiterally(S);
1197 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1198 const Loop *L = S->getLoop();
1200 // First check for an existing canonical IV in a suitable type.
1201 PHINode *CanonicalIV = 0;
1202 if (PHINode *PN = L->getCanonicalInductionVariable())
1203 if (SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty))
1206 // Rewrite an AddRec in terms of the canonical induction variable, if
1207 // its type is more narrow.
1209 SE.getTypeSizeInBits(CanonicalIV->getType()) >
1210 SE.getTypeSizeInBits(Ty)) {
1211 SmallVector<const SCEV *, 4> NewOps(S->getNumOperands());
1212 for (unsigned i = 0, e = S->getNumOperands(); i != e; ++i)
1213 NewOps[i] = SE.getAnyExtendExpr(S->op_begin()[i], CanonicalIV->getType());
1214 Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop(),
1215 // FIXME: S->getNoWrapFlags(FlagNW)
1216 SCEV::FlagAnyWrap));
1217 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
1218 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
1219 BasicBlock::iterator NewInsertPt =
1220 llvm::next(BasicBlock::iterator(cast<Instruction>(V)));
1221 while (isa<PHINode>(NewInsertPt) || isa<DbgInfoIntrinsic>(NewInsertPt) ||
1222 isa<LandingPadInst>(NewInsertPt))
1224 V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0,
1226 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
1230 // {X,+,F} --> X + {0,+,F}
1231 if (!S->getStart()->isZero()) {
1232 SmallVector<const SCEV *, 4> NewOps(S->op_begin(), S->op_end());
1233 NewOps[0] = SE.getConstant(Ty, 0);
1234 // FIXME: can use S->getNoWrapFlags()
1235 const SCEV *Rest = SE.getAddRecExpr(NewOps, L, SCEV::FlagAnyWrap);
1237 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
1238 // comments on expandAddToGEP for details.
1239 const SCEV *Base = S->getStart();
1240 const SCEV *RestArray[1] = { Rest };
1241 // Dig into the expression to find the pointer base for a GEP.
1242 ExposePointerBase(Base, RestArray[0], SE);
1243 // If we found a pointer, expand the AddRec with a GEP.
1244 if (PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
1245 // Make sure the Base isn't something exotic, such as a multiplied
1246 // or divided pointer value. In those cases, the result type isn't
1247 // actually a pointer type.
1248 if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
1249 Value *StartV = expand(Base);
1250 assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
1251 return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
1255 // Just do a normal add. Pre-expand the operands to suppress folding.
1256 return expand(SE.getAddExpr(SE.getUnknown(expand(S->getStart())),
1257 SE.getUnknown(expand(Rest))));
1260 // If we don't yet have a canonical IV, create one.
1262 // Create and insert the PHI node for the induction variable in the
1264 BasicBlock *Header = L->getHeader();
1265 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1266 CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar",
1268 rememberInstruction(CanonicalIV);
1270 Constant *One = ConstantInt::get(Ty, 1);
1271 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1272 BasicBlock *HP = *HPI;
1273 if (L->contains(HP)) {
1274 // Insert a unit add instruction right before the terminator
1275 // corresponding to the back-edge.
1276 Instruction *Add = BinaryOperator::CreateAdd(CanonicalIV, One,
1278 HP->getTerminator());
1279 Add->setDebugLoc(HP->getTerminator()->getDebugLoc());
1280 rememberInstruction(Add);
1281 CanonicalIV->addIncoming(Add, HP);
1283 CanonicalIV->addIncoming(Constant::getNullValue(Ty), HP);
1288 // {0,+,1} --> Insert a canonical induction variable into the loop!
1289 if (S->isAffine() && S->getOperand(1)->isOne()) {
1290 assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) &&
1291 "IVs with types different from the canonical IV should "
1292 "already have been handled!");
1296 // {0,+,F} --> {0,+,1} * F
1298 // If this is a simple linear addrec, emit it now as a special case.
1299 if (S->isAffine()) // {0,+,F} --> i*F
1301 expand(SE.getTruncateOrNoop(
1302 SE.getMulExpr(SE.getUnknown(CanonicalIV),
1303 SE.getNoopOrAnyExtend(S->getOperand(1),
1304 CanonicalIV->getType())),
1307 // If this is a chain of recurrences, turn it into a closed form, using the
1308 // folders, then expandCodeFor the closed form. This allows the folders to
1309 // simplify the expression without having to build a bunch of special code
1310 // into this folder.
1311 const SCEV *IH = SE.getUnknown(CanonicalIV); // Get I as a "symbolic" SCEV.
1313 // Promote S up to the canonical IV type, if the cast is foldable.
1314 const SCEV *NewS = S;
1315 const SCEV *Ext = SE.getNoopOrAnyExtend(S, CanonicalIV->getType());
1316 if (isa<SCEVAddRecExpr>(Ext))
1319 const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE);
1320 //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
1322 // Truncate the result down to the original type, if needed.
1323 const SCEV *T = SE.getTruncateOrNoop(V, Ty);
1327 Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
1328 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1329 Value *V = expandCodeFor(S->getOperand(),
1330 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1331 Value *I = Builder.CreateTrunc(V, Ty);
1332 rememberInstruction(I);
1336 Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
1337 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1338 Value *V = expandCodeFor(S->getOperand(),
1339 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1340 Value *I = Builder.CreateZExt(V, Ty);
1341 rememberInstruction(I);
1345 Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
1346 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1347 Value *V = expandCodeFor(S->getOperand(),
1348 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1349 Value *I = Builder.CreateSExt(V, Ty);
1350 rememberInstruction(I);
1354 Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
1355 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1356 Type *Ty = LHS->getType();
1357 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1358 // In the case of mixed integer and pointer types, do the
1359 // rest of the comparisons as integer.
1360 if (S->getOperand(i)->getType() != Ty) {
1361 Ty = SE.getEffectiveSCEVType(Ty);
1362 LHS = InsertNoopCastOfTo(LHS, Ty);
1364 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1365 Value *ICmp = Builder.CreateICmpSGT(LHS, RHS);
1366 rememberInstruction(ICmp);
1367 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax");
1368 rememberInstruction(Sel);
1371 // In the case of mixed integer and pointer types, cast the
1372 // final result back to the pointer type.
1373 if (LHS->getType() != S->getType())
1374 LHS = InsertNoopCastOfTo(LHS, S->getType());
1378 Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
1379 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1380 Type *Ty = LHS->getType();
1381 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1382 // In the case of mixed integer and pointer types, do the
1383 // rest of the comparisons as integer.
1384 if (S->getOperand(i)->getType() != Ty) {
1385 Ty = SE.getEffectiveSCEVType(Ty);
1386 LHS = InsertNoopCastOfTo(LHS, Ty);
1388 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1389 Value *ICmp = Builder.CreateICmpUGT(LHS, RHS);
1390 rememberInstruction(ICmp);
1391 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax");
1392 rememberInstruction(Sel);
1395 // In the case of mixed integer and pointer types, cast the
1396 // final result back to the pointer type.
1397 if (LHS->getType() != S->getType())
1398 LHS = InsertNoopCastOfTo(LHS, S->getType());
1402 Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty,
1404 BasicBlock::iterator IP = I;
1405 while (isInsertedInstruction(IP) || isa<DbgInfoIntrinsic>(IP))
1407 Builder.SetInsertPoint(IP->getParent(), IP);
1408 return expandCodeFor(SH, Ty);
1411 Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty) {
1412 // Expand the code for this SCEV.
1413 Value *V = expand(SH);
1415 assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
1416 "non-trivial casts should be done with the SCEVs directly!");
1417 V = InsertNoopCastOfTo(V, Ty);
1422 Value *SCEVExpander::expand(const SCEV *S) {
1423 // Compute an insertion point for this SCEV object. Hoist the instructions
1424 // as far out in the loop nest as possible.
1425 Instruction *InsertPt = Builder.GetInsertPoint();
1426 for (Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock()); ;
1427 L = L->getParentLoop())
1428 if (SE.isLoopInvariant(S, L)) {
1430 if (BasicBlock *Preheader = L->getLoopPreheader())
1431 InsertPt = Preheader->getTerminator();
1433 // LSR sets the insertion point for AddRec start/step values to the
1434 // block start to simplify value reuse, even though it's an invalid
1435 // position. SCEVExpander must correct for this in all cases.
1436 InsertPt = L->getHeader()->getFirstInsertionPt();
1439 // If the SCEV is computable at this level, insert it into the header
1440 // after the PHIs (and after any other instructions that we've inserted
1441 // there) so that it is guaranteed to dominate any user inside the loop.
1442 if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
1443 InsertPt = L->getHeader()->getFirstInsertionPt();
1444 while (isInsertedInstruction(InsertPt) || isa<DbgInfoIntrinsic>(InsertPt))
1445 InsertPt = llvm::next(BasicBlock::iterator(InsertPt));
1449 // Check to see if we already expanded this here.
1450 std::map<std::pair<const SCEV *, Instruction *>,
1451 AssertingVH<Value> >::iterator I =
1452 InsertedExpressions.find(std::make_pair(S, InsertPt));
1453 if (I != InsertedExpressions.end())
1456 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
1457 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
1458 Builder.SetInsertPoint(InsertPt->getParent(), InsertPt);
1460 // Expand the expression into instructions.
1461 Value *V = visit(S);
1463 // Remember the expanded value for this SCEV at this location.
1465 // This is independent of PostIncLoops. The mapped value simply materializes
1466 // the expression at this insertion point. If the mapped value happened to be
1467 // a postinc expansion, it could be reused by a non postinc user, but only if
1468 // its insertion point was already at the head of the loop.
1469 InsertedExpressions[std::make_pair(S, InsertPt)] = V;
1471 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
1475 void SCEVExpander::rememberInstruction(Value *I) {
1476 if (!PostIncLoops.empty())
1477 InsertedPostIncValues.insert(I);
1479 InsertedValues.insert(I);
1481 // If we just claimed an existing instruction and that instruction had
1482 // been the insert point, adjust the insert point forward so that
1483 // subsequently inserted code will be dominated.
1484 if (Builder.GetInsertPoint() == I) {
1485 BasicBlock::iterator It = cast<Instruction>(I);
1486 do { ++It; } while (isInsertedInstruction(It) ||
1487 isa<DbgInfoIntrinsic>(It));
1488 Builder.SetInsertPoint(Builder.GetInsertBlock(), It);
1492 void SCEVExpander::restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I) {
1493 // If we acquired more instructions since the old insert point was saved,
1494 // advance past them.
1495 while (isInsertedInstruction(I) || isa<DbgInfoIntrinsic>(I)) ++I;
1497 Builder.SetInsertPoint(BB, I);
1500 /// getOrInsertCanonicalInductionVariable - This method returns the
1501 /// canonical induction variable of the specified type for the specified
1502 /// loop (inserting one if there is none). A canonical induction variable
1503 /// starts at zero and steps by one on each iteration.
1505 SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L,
1507 assert(Ty->isIntegerTy() && "Can only insert integer induction variables!");
1509 // Build a SCEV for {0,+,1}<L>.
1510 // Conservatively use FlagAnyWrap for now.
1511 const SCEV *H = SE.getAddRecExpr(SE.getConstant(Ty, 0),
1512 SE.getConstant(Ty, 1), L, SCEV::FlagAnyWrap);
1514 // Emit code for it.
1515 BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
1516 BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
1517 PHINode *V = cast<PHINode>(expandCodeFor(H, 0, L->getHeader()->begin()));
1519 restoreInsertPoint(SaveInsertBB, SaveInsertPt);
1524 /// hoistStep - Attempt to hoist an IV increment above a potential use.
1526 /// To successfully hoist, two criteria must be met:
1527 /// - IncV operands dominate InsertPos and
1528 /// - InsertPos dominates IncV
1530 /// Meeting the second condition means that we don't need to check all of IncV's
1531 /// existing uses (it's moving up in the domtree).
1533 /// This does not yet recursively hoist the operands, although that would
1534 /// not be difficult.
1536 /// This does not require a SCEVExpander instance and could be replaced by a
1537 /// general code-insertion helper.
1538 bool SCEVExpander::hoistStep(Instruction *IncV, Instruction *InsertPos,
1539 const DominatorTree *DT) {
1540 if (DT->dominates(IncV, InsertPos))
1543 if (!DT->dominates(InsertPos->getParent(), IncV->getParent()))
1546 if (IncV->mayHaveSideEffects())
1549 // Attempt to hoist IncV
1550 for (User::op_iterator OI = IncV->op_begin(), OE = IncV->op_end();
1552 Instruction *OInst = dyn_cast<Instruction>(OI);
1553 if (OInst && (OInst == InsertPos || !DT->dominates(OInst, InsertPos)))
1556 IncV->moveBefore(InsertPos);
1560 /// replaceCongruentIVs - Check for congruent phis in this loop header and
1561 /// replace them with their most canonical representative. Return the number of
1562 /// phis eliminated.
1564 /// This does not depend on any SCEVExpander state but should be used in
1565 /// the same context that SCEVExpander is used.
1566 unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
1567 SmallVectorImpl<WeakVH> &DeadInsts) {
1568 unsigned NumElim = 0;
1569 DenseMap<const SCEV *, PHINode *> ExprToIVMap;
1570 for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {
1571 PHINode *Phi = cast<PHINode>(I);
1572 if (!SE.isSCEVable(Phi->getType()))
1575 PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
1581 // If one phi derives from the other via GEPs, types may differ.
1582 // We could consider adding a bitcast here to handle it.
1583 if (OrigPhiRef->getType() != Phi->getType())
1586 if (BasicBlock *LatchBlock = L->getLoopLatch()) {
1587 Instruction *OrigInc =
1588 cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));
1589 Instruction *IsomorphicInc =
1590 cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
1592 // If this phi is more canonical, swap it with the original.
1593 if (!isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)
1594 && isExpandedAddRecExprPHI(Phi, IsomorphicInc, L)) {
1595 std::swap(OrigPhiRef, Phi);
1596 std::swap(OrigInc, IsomorphicInc);
1598 // Replacing the congruent phi is sufficient because acyclic redundancy
1599 // elimination, CSE/GVN, should handle the rest. However, once SCEV proves
1600 // that a phi is congruent, it's often the head of an IV user cycle that
1601 // is isomorphic with the original phi. So it's worth eagerly cleaning up
1602 // the common case of a single IV increment.
1603 if (OrigInc != IsomorphicInc &&
1604 OrigInc->getType() == IsomorphicInc->getType() &&
1605 SE.getSCEV(OrigInc) == SE.getSCEV(IsomorphicInc) &&
1606 hoistStep(OrigInc, IsomorphicInc, DT)) {
1607 DEBUG_WITH_TYPE(DebugType, dbgs()
1608 << "INDVARS: Eliminated congruent iv.inc: "
1609 << *IsomorphicInc << '\n');
1610 IsomorphicInc->replaceAllUsesWith(OrigInc);
1611 DeadInsts.push_back(IsomorphicInc);
1614 DEBUG_WITH_TYPE(DebugType, dbgs()
1615 << "INDVARS: Eliminated congruent iv: " << *Phi << '\n');
1617 Phi->replaceAllUsesWith(OrigPhiRef);
1618 DeadInsts.push_back(Phi);