1 //===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===//
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 //===----------------------------------------------------------------------===//
9 #include "LoopVectorize.h"
10 #include "llvm/ADT/SmallSet.h"
11 #include "llvm/ADT/StringExtras.h"
12 #include "llvm/Analysis/AliasAnalysis.h"
13 #include "llvm/Analysis/AliasSetTracker.h"
14 #include "llvm/Analysis/Dominators.h"
15 #include "llvm/Analysis/LoopInfo.h"
16 #include "llvm/Analysis/LoopIterator.h"
17 #include "llvm/Analysis/LoopPass.h"
18 #include "llvm/Analysis/ScalarEvolutionExpander.h"
19 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
20 #include "llvm/Analysis/TargetTransformInfo.h"
21 #include "llvm/Analysis/ValueTracking.h"
22 #include "llvm/Analysis/Verifier.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/DerivedTypes.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/IR/IntrinsicInst.h"
29 #include "llvm/IR/LLVMContext.h"
30 #include "llvm/IR/Module.h"
31 #include "llvm/IR/Type.h"
32 #include "llvm/IR/Value.h"
33 #include "llvm/Pass.h"
34 #include "llvm/Support/CommandLine.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
39 #include "llvm/Transforms/Utils/Local.h"
40 #include "llvm/Transforms/Vectorize.h"
42 static cl::opt<unsigned>
43 VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden,
44 cl::desc("Sets the SIMD width. Zero is autoselect."));
46 static cl::opt<unsigned>
47 VectorizationUnroll("force-vector-unroll", cl::init(0), cl::Hidden,
48 cl::desc("Sets the vectorization unroll count. "
49 "Zero is autoselect."));
52 EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
53 cl::desc("Enable if-conversion during vectorization."));
57 /// The LoopVectorize Pass.
58 struct LoopVectorize : public LoopPass {
59 /// Pass identification, replacement for typeid
62 explicit LoopVectorize() : LoopPass(ID) {
63 initializeLoopVectorizePass(*PassRegistry::getPassRegistry());
69 TargetTransformInfo *TTI;
72 virtual bool runOnLoop(Loop *L, LPPassManager &LPM) {
73 // We only vectorize innermost loops.
77 SE = &getAnalysis<ScalarEvolution>();
78 DL = getAnalysisIfAvailable<DataLayout>();
79 LI = &getAnalysis<LoopInfo>();
80 TTI = getAnalysisIfAvailable<TargetTransformInfo>();
81 DT = &getAnalysis<DominatorTree>();
83 DEBUG(dbgs() << "LV: Checking a loop in \"" <<
84 L->getHeader()->getParent()->getName() << "\"\n");
86 // Check if it is legal to vectorize the loop.
87 LoopVectorizationLegality LVL(L, SE, DL, DT);
88 if (!LVL.canVectorize()) {
89 DEBUG(dbgs() << "LV: Not vectorizing.\n");
93 // Use the cost model.
94 LoopVectorizationCostModel CM(L, SE, LI, &LVL, TTI);
96 // Check the function attribues to find out if this function should be
97 // optimized for size.
98 Function *F = L->getHeader()->getParent();
99 Attribute::AttrKind SzAttr = Attribute::OptimizeForSize;
100 Attribute::AttrKind FlAttr = Attribute::NoImplicitFloat;
101 unsigned FnIndex = AttributeSet::FunctionIndex;
102 bool OptForSize = F->getAttributes().hasAttribute(FnIndex, SzAttr);
103 bool NoFloat = F->getAttributes().hasAttribute(FnIndex, FlAttr);
106 DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
107 "attribute is used.\n");
111 unsigned VF = CM.selectVectorizationFactor(OptForSize, VectorizationFactor);
112 unsigned UF = CM.selectUnrollFactor(OptForSize, VectorizationUnroll);
115 DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
119 DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF << ") in "<<
120 F->getParent()->getModuleIdentifier()<<"\n");
121 DEBUG(dbgs() << "LV: Unroll Factor is " << UF << "\n");
123 // If we decided that it is *legal* to vectorizer the loop then do it.
124 InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF, UF);
127 DEBUG(verifyFunction(*L->getHeader()->getParent()));
131 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
132 LoopPass::getAnalysisUsage(AU);
133 AU.addRequiredID(LoopSimplifyID);
134 AU.addRequiredID(LCSSAID);
135 AU.addRequired<LoopInfo>();
136 AU.addRequired<ScalarEvolution>();
137 AU.addRequired<DominatorTree>();
138 AU.addPreserved<LoopInfo>();
139 AU.addPreserved<DominatorTree>();
146 //===----------------------------------------------------------------------===//
147 // Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
148 // LoopVectorizationCostModel.
149 //===----------------------------------------------------------------------===//
152 LoopVectorizationLegality::RuntimePointerCheck::insert(ScalarEvolution *SE,
153 Loop *Lp, Value *Ptr) {
154 const SCEV *Sc = SE->getSCEV(Ptr);
155 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
156 assert(AR && "Invalid addrec expression");
157 const SCEV *Ex = SE->getExitCount(Lp, Lp->getLoopLatch());
158 const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
159 Pointers.push_back(Ptr);
160 Starts.push_back(AR->getStart());
161 Ends.push_back(ScEnd);
164 Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
165 // Save the current insertion location.
166 Instruction *Loc = Builder.GetInsertPoint();
168 // We need to place the broadcast of invariant variables outside the loop.
169 Instruction *Instr = dyn_cast<Instruction>(V);
170 bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
171 bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
173 // Place the code for broadcasting invariant variables in the new preheader.
175 Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
177 // Broadcast the scalar into all locations in the vector.
178 Value *Shuf = Builder.CreateVectorSplat(VF, V, "broadcast");
180 // Restore the builder insertion point.
182 Builder.SetInsertPoint(Loc);
187 Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, unsigned StartIdx,
189 assert(Val->getType()->isVectorTy() && "Must be a vector");
190 assert(Val->getType()->getScalarType()->isIntegerTy() &&
191 "Elem must be an integer");
193 Type *ITy = Val->getType()->getScalarType();
194 VectorType *Ty = cast<VectorType>(Val->getType());
195 int VLen = Ty->getNumElements();
196 SmallVector<Constant*, 8> Indices;
198 // Create a vector of consecutive numbers from zero to VF.
199 for (int i = 0; i < VLen; ++i) {
200 int Idx = Negate ? (-i): i;
201 Indices.push_back(ConstantInt::get(ITy, StartIdx + Idx));
204 // Add the consecutive indices to the vector value.
205 Constant *Cv = ConstantVector::get(Indices);
206 assert(Cv->getType() == Val->getType() && "Invalid consecutive vec");
207 return Builder.CreateAdd(Val, Cv, "induction");
210 int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
211 assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr");
213 // If this value is a pointer induction variable we know it is consecutive.
214 PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
215 if (Phi && Inductions.count(Phi)) {
216 InductionInfo II = Inductions[Phi];
217 if (PtrInduction == II.IK)
221 GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
225 unsigned NumOperands = Gep->getNumOperands();
226 Value *LastIndex = Gep->getOperand(NumOperands - 1);
228 // Check that all of the gep indices are uniform except for the last.
229 for (unsigned i = 0; i < NumOperands - 1; ++i)
230 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
233 // We can emit wide load/stores only if the last index is the induction
235 const SCEV *Last = SE->getSCEV(LastIndex);
236 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) {
237 const SCEV *Step = AR->getStepRecurrence(*SE);
239 // The memory is consecutive because the last index is consecutive
240 // and all other indices are loop invariant.
243 if (Step->isAllOnesValue())
250 bool LoopVectorizationLegality::isUniform(Value *V) {
251 return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
254 InnerLoopVectorizer::VectorParts&
255 InnerLoopVectorizer::getVectorValue(Value *V) {
256 assert(V != Induction && "The new induction variable should not be used.");
257 assert(!V->getType()->isVectorTy() && "Can't widen a vector");
259 // If we have this scalar in the map, return it.
261 return WidenMap.get(V);
263 // If this scalar is unknown, assume that it is a constant or that it is
264 // loop invariant. Broadcast V and save the value for future uses.
265 Value *B = getBroadcastInstrs(V);
266 WidenMap.splat(V, B);
267 return WidenMap.get(V);
271 InnerLoopVectorizer::getUniformVector(unsigned Val, Type* ScalarTy) {
272 return ConstantVector::getSplat(VF, ConstantInt::get(ScalarTy, Val, true));
275 Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
276 assert(Vec->getType()->isVectorTy() && "Invalid type");
277 SmallVector<Constant*, 8> ShuffleMask;
278 for (unsigned i = 0; i < VF; ++i)
279 ShuffleMask.push_back(Builder.getInt32(VF - i - 1));
281 return Builder.CreateShuffleVector(Vec, UndefValue::get(Vec->getType()),
282 ConstantVector::get(ShuffleMask),
286 void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
287 assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
288 // Holds vector parameters or scalars, in case of uniform vals.
289 SmallVector<VectorParts, 4> Params;
291 // Find all of the vectorized parameters.
292 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
293 Value *SrcOp = Instr->getOperand(op);
295 // If we are accessing the old induction variable, use the new one.
296 if (SrcOp == OldInduction) {
297 Params.push_back(getVectorValue(SrcOp));
301 // Try using previously calculated values.
302 Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
304 // If the src is an instruction that appeared earlier in the basic block
305 // then it should already be vectorized.
306 if (SrcInst && OrigLoop->contains(SrcInst)) {
307 assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
308 // The parameter is a vector value from earlier.
309 Params.push_back(WidenMap.get(SrcInst));
311 // The parameter is a scalar from outside the loop. Maybe even a constant.
313 Scalars.append(UF, SrcOp);
314 Params.push_back(Scalars);
318 assert(Params.size() == Instr->getNumOperands() &&
319 "Invalid number of operands");
321 // Does this instruction return a value ?
322 bool IsVoidRetTy = Instr->getType()->isVoidTy();
324 Value *UndefVec = IsVoidRetTy ? 0 :
325 UndefValue::get(VectorType::get(Instr->getType(), VF));
326 // Create a new entry in the WidenMap and initialize it to Undef or Null.
327 VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
329 // For each scalar that we create:
330 for (unsigned Width = 0; Width < VF; ++Width) {
331 // For each vector unroll 'part':
332 for (unsigned Part = 0; Part < UF; ++Part) {
333 Instruction *Cloned = Instr->clone();
335 Cloned->setName(Instr->getName() + ".cloned");
336 // Replace the operands of the cloned instrucions with extracted scalars.
337 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
338 Value *Op = Params[op][Part];
339 // Param is a vector. Need to extract the right lane.
340 if (Op->getType()->isVectorTy())
341 Op = Builder.CreateExtractElement(Op, Builder.getInt32(Width));
342 Cloned->setOperand(op, Op);
345 // Place the cloned scalar in the new loop.
346 Builder.Insert(Cloned);
348 // If the original scalar returns a value we need to place it in a vector
349 // so that future users will be able to use it.
351 VecResults[Part] = Builder.CreateInsertElement(VecResults[Part], Cloned,
352 Builder.getInt32(Width));
358 InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
360 LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
361 Legal->getRuntimePointerCheck();
363 if (!PtrRtCheck->Need)
366 Value *MemoryRuntimeCheck = 0;
367 unsigned NumPointers = PtrRtCheck->Pointers.size();
368 SmallVector<Value* , 2> Starts;
369 SmallVector<Value* , 2> Ends;
371 SCEVExpander Exp(*SE, "induction");
373 // Use this type for pointer arithmetic.
374 Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0);
376 for (unsigned i = 0; i < NumPointers; ++i) {
377 Value *Ptr = PtrRtCheck->Pointers[i];
378 const SCEV *Sc = SE->getSCEV(Ptr);
380 if (SE->isLoopInvariant(Sc, OrigLoop)) {
381 DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
383 Starts.push_back(Ptr);
386 DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
388 Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
389 Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
390 Starts.push_back(Start);
395 for (unsigned i = 0; i < NumPointers; ++i) {
396 for (unsigned j = i+1; j < NumPointers; ++j) {
397 Instruction::CastOps Op = Instruction::BitCast;
398 Value *Start0 = CastInst::Create(Op, Starts[i], PtrArithTy, "bc", Loc);
399 Value *Start1 = CastInst::Create(Op, Starts[j], PtrArithTy, "bc", Loc);
400 Value *End0 = CastInst::Create(Op, Ends[i], PtrArithTy, "bc", Loc);
401 Value *End1 = CastInst::Create(Op, Ends[j], PtrArithTy, "bc", Loc);
403 Value *Cmp0 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
404 Start0, End1, "bound0", Loc);
405 Value *Cmp1 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
406 Start1, End0, "bound1", Loc);
407 Value *IsConflict = BinaryOperator::Create(Instruction::And, Cmp0, Cmp1,
408 "found.conflict", Loc);
409 if (MemoryRuntimeCheck)
410 MemoryRuntimeCheck = BinaryOperator::Create(Instruction::Or,
413 "conflict.rdx", Loc);
415 MemoryRuntimeCheck = IsConflict;
420 return MemoryRuntimeCheck;
424 InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
426 In this function we generate a new loop. The new loop will contain
427 the vectorized instructions while the old loop will continue to run the
430 [ ] <-- vector loop bypass.
433 | [ ] <-- vector pre header.
437 | [ ]_| <-- vector loop.
440 >[ ] <--- middle-block.
443 | [ ] <--- new preheader.
447 | [ ]_| <-- old scalar loop to handle remainder.
454 BasicBlock *OldBasicBlock = OrigLoop->getHeader();
455 BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
456 BasicBlock *ExitBlock = OrigLoop->getExitBlock();
457 assert(ExitBlock && "Must have an exit block");
459 // Some loops have a single integer induction variable, while other loops
460 // don't. One example is c++ iterators that often have multiple pointer
461 // induction variables. In the code below we also support a case where we
462 // don't have a single induction variable.
463 OldInduction = Legal->getInduction();
464 Type *IdxTy = OldInduction ? OldInduction->getType() :
465 DL->getIntPtrType(SE->getContext());
467 // Find the loop boundaries.
468 const SCEV *ExitCount = SE->getExitCount(OrigLoop, OrigLoop->getLoopLatch());
469 assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count");
471 // Get the total trip count from the count by adding 1.
472 ExitCount = SE->getAddExpr(ExitCount,
473 SE->getConstant(ExitCount->getType(), 1));
475 // Expand the trip count and place the new instructions in the preheader.
476 // Notice that the pre-header does not change, only the loop body.
477 SCEVExpander Exp(*SE, "induction");
479 // Count holds the overall loop count (N).
480 Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
481 BypassBlock->getTerminator());
483 // The loop index does not have to start at Zero. Find the original start
484 // value from the induction PHI node. If we don't have an induction variable
485 // then we know that it starts at zero.
486 Value *StartIdx = OldInduction ?
487 OldInduction->getIncomingValueForBlock(BypassBlock):
488 ConstantInt::get(IdxTy, 0);
490 assert(BypassBlock && "Invalid loop structure");
492 // Generate the code that checks in runtime if arrays overlap.
493 Value *MemoryRuntimeCheck = addRuntimeCheck(Legal,
494 BypassBlock->getTerminator());
496 // Split the single block loop into the two loop structure described above.
497 BasicBlock *VectorPH =
498 BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
499 BasicBlock *VecBody =
500 VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
501 BasicBlock *MiddleBlock =
502 VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
503 BasicBlock *ScalarPH =
504 MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
506 // This is the location in which we add all of the logic for bypassing
507 // the new vector loop.
508 Instruction *Loc = BypassBlock->getTerminator();
510 // Use this IR builder to create the loop instructions (Phi, Br, Cmp)
512 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
514 // Generate the induction variable.
515 Induction = Builder.CreatePHI(IdxTy, 2, "index");
516 // The loop step is equal to the vectorization factor (num of SIMD elements)
517 // times the unroll factor (num of SIMD instructions).
518 Constant *Step = ConstantInt::get(IdxTy, VF * UF);
520 // We may need to extend the index in case there is a type mismatch.
521 // We know that the count starts at zero and does not overflow.
522 if (Count->getType() != IdxTy) {
523 // The exit count can be of pointer type. Convert it to the correct
525 if (ExitCount->getType()->isPointerTy())
526 Count = CastInst::CreatePointerCast(Count, IdxTy, "ptrcnt.to.int", Loc);
528 Count = CastInst::CreateZExtOrBitCast(Count, IdxTy, "zext.cnt", Loc);
531 // Add the start index to the loop count to get the new end index.
532 Value *IdxEnd = BinaryOperator::CreateAdd(Count, StartIdx, "end.idx", Loc);
534 // Now we need to generate the expression for N - (N % VF), which is
535 // the part that the vectorized body will execute.
536 Value *R = BinaryOperator::CreateURem(Count, Step, "n.mod.vf", Loc);
537 Value *CountRoundDown = BinaryOperator::CreateSub(Count, R, "n.vec", Loc);
538 Value *IdxEndRoundDown = BinaryOperator::CreateAdd(CountRoundDown, StartIdx,
539 "end.idx.rnd.down", Loc);
541 // Now, compare the new count to zero. If it is zero skip the vector loop and
542 // jump to the scalar loop.
543 Value *Cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
548 // If we are using memory runtime checks, include them in.
549 if (MemoryRuntimeCheck)
550 Cmp = BinaryOperator::Create(Instruction::Or, Cmp, MemoryRuntimeCheck,
553 BranchInst::Create(MiddleBlock, VectorPH, Cmp, Loc);
554 // Remove the old terminator.
555 Loc->eraseFromParent();
557 // We are going to resume the execution of the scalar loop.
558 // Go over all of the induction variables that we found and fix the
559 // PHIs that are left in the scalar version of the loop.
560 // The starting values of PHI nodes depend on the counter of the last
561 // iteration in the vectorized loop.
562 // If we come from a bypass edge then we need to start from the original
565 // This variable saves the new starting index for the scalar loop.
566 PHINode *ResumeIndex = 0;
567 LoopVectorizationLegality::InductionList::iterator I, E;
568 LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
569 for (I = List->begin(), E = List->end(); I != E; ++I) {
570 PHINode *OrigPhi = I->first;
571 LoopVectorizationLegality::InductionInfo II = I->second;
572 PHINode *ResumeVal = PHINode::Create(OrigPhi->getType(), 2, "resume.val",
573 MiddleBlock->getTerminator());
576 case LoopVectorizationLegality::NoInduction:
577 llvm_unreachable("Unknown induction");
578 case LoopVectorizationLegality::IntInduction: {
579 // Handle the integer induction counter:
580 assert(OrigPhi->getType()->isIntegerTy() && "Invalid type");
581 assert(OrigPhi == OldInduction && "Unknown integer PHI");
582 // We know what the end value is.
583 EndValue = IdxEndRoundDown;
584 // We also know which PHI node holds it.
585 ResumeIndex = ResumeVal;
588 case LoopVectorizationLegality::ReverseIntInduction: {
589 // Convert the CountRoundDown variable to the PHI size.
590 unsigned CRDSize = CountRoundDown->getType()->getScalarSizeInBits();
591 unsigned IISize = II.StartValue->getType()->getScalarSizeInBits();
592 Value *CRD = CountRoundDown;
593 if (CRDSize > IISize)
594 CRD = CastInst::Create(Instruction::Trunc, CountRoundDown,
595 II.StartValue->getType(),
596 "tr.crd", BypassBlock->getTerminator());
597 else if (CRDSize < IISize)
598 CRD = CastInst::Create(Instruction::SExt, CountRoundDown,
599 II.StartValue->getType(),
600 "sext.crd", BypassBlock->getTerminator());
601 // Handle reverse integer induction counter:
602 EndValue = BinaryOperator::CreateSub(II.StartValue, CRD, "rev.ind.end",
603 BypassBlock->getTerminator());
606 case LoopVectorizationLegality::PtrInduction: {
607 // For pointer induction variables, calculate the offset using
609 EndValue = GetElementPtrInst::Create(II.StartValue, CountRoundDown,
611 BypassBlock->getTerminator());
616 // The new PHI merges the original incoming value, in case of a bypass,
617 // or the value at the end of the vectorized loop.
618 ResumeVal->addIncoming(II.StartValue, BypassBlock);
619 ResumeVal->addIncoming(EndValue, VecBody);
621 // Fix the scalar body counter (PHI node).
622 unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH);
623 OrigPhi->setIncomingValue(BlockIdx, ResumeVal);
626 // If we are generating a new induction variable then we also need to
627 // generate the code that calculates the exit value. This value is not
628 // simply the end of the counter because we may skip the vectorized body
629 // in case of a runtime check.
631 assert(!ResumeIndex && "Unexpected resume value found");
632 ResumeIndex = PHINode::Create(IdxTy, 2, "new.indc.resume.val",
633 MiddleBlock->getTerminator());
634 ResumeIndex->addIncoming(StartIdx, BypassBlock);
635 ResumeIndex->addIncoming(IdxEndRoundDown, VecBody);
638 // Make sure that we found the index where scalar loop needs to continue.
639 assert(ResumeIndex && ResumeIndex->getType()->isIntegerTy() &&
640 "Invalid resume Index");
642 // Add a check in the middle block to see if we have completed
643 // all of the iterations in the first vector loop.
644 // If (N - N%VF) == N, then we *don't* need to run the remainder.
645 Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd,
646 ResumeIndex, "cmp.n",
647 MiddleBlock->getTerminator());
649 BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator());
650 // Remove the old terminator.
651 MiddleBlock->getTerminator()->eraseFromParent();
653 // Create i+1 and fill the PHINode.
654 Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next");
655 Induction->addIncoming(StartIdx, VectorPH);
656 Induction->addIncoming(NextIdx, VecBody);
657 // Create the compare.
658 Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown);
659 Builder.CreateCondBr(ICmp, MiddleBlock, VecBody);
661 // Now we have two terminators. Remove the old one from the block.
662 VecBody->getTerminator()->eraseFromParent();
664 // Get ready to start creating new instructions into the vectorized body.
665 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
667 // Create and register the new vector loop.
668 Loop* Lp = new Loop();
669 Loop *ParentLoop = OrigLoop->getParentLoop();
671 // Insert the new loop into the loop nest and register the new basic blocks.
673 ParentLoop->addChildLoop(Lp);
674 ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
675 ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
676 ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
678 LI->addTopLevelLoop(Lp);
681 Lp->addBasicBlockToLoop(VecBody, LI->getBase());
684 LoopVectorPreHeader = VectorPH;
685 LoopScalarPreHeader = ScalarPH;
686 LoopMiddleBlock = MiddleBlock;
687 LoopExitBlock = ExitBlock;
688 LoopVectorBody = VecBody;
689 LoopScalarBody = OldBasicBlock;
690 LoopBypassBlock = BypassBlock;
693 /// This function returns the identity element (or neutral element) for
696 getReductionIdentity(LoopVectorizationLegality::ReductionKind K) {
698 case LoopVectorizationLegality::IntegerXor:
699 case LoopVectorizationLegality::IntegerAdd:
700 case LoopVectorizationLegality::IntegerOr:
701 // Adding, Xoring, Oring zero to a number does not change it.
703 case LoopVectorizationLegality::IntegerMult:
704 // Multiplying a number by 1 does not change it.
706 case LoopVectorizationLegality::IntegerAnd:
707 // AND-ing a number with an all-1 value does not change it.
710 llvm_unreachable("Unknown reduction kind");
715 isTriviallyVectorizableIntrinsic(Instruction *Inst) {
716 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst);
719 switch (II->getIntrinsicID()) {
720 case Intrinsic::sqrt:
724 case Intrinsic::exp2:
726 case Intrinsic::log10:
727 case Intrinsic::log2:
728 case Intrinsic::fabs:
729 case Intrinsic::floor:
730 case Intrinsic::ceil:
731 case Intrinsic::trunc:
732 case Intrinsic::rint:
733 case Intrinsic::nearbyint:
736 case Intrinsic::fmuladd:
745 InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
746 //===------------------------------------------------===//
748 // Notice: any optimization or new instruction that go
749 // into the code below should be also be implemented in
752 //===------------------------------------------------===//
753 BasicBlock &BB = *OrigLoop->getHeader();
755 ConstantInt::get(IntegerType::getInt32Ty(BB.getContext()), 0);
757 // In order to support reduction variables we need to be able to vectorize
758 // Phi nodes. Phi nodes have cycles, so we need to vectorize them in two
759 // stages. First, we create a new vector PHI node with no incoming edges.
760 // We use this value when we vectorize all of the instructions that use the
761 // PHI. Next, after all of the instructions in the block are complete we
762 // add the new incoming edges to the PHI. At this point all of the
763 // instructions in the basic block are vectorized, so we can use them to
764 // construct the PHI.
765 PhiVector RdxPHIsToFix;
767 // Scan the loop in a topological order to ensure that defs are vectorized
769 LoopBlocksDFS DFS(OrigLoop);
772 // Vectorize all of the blocks in the original loop.
773 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
774 be = DFS.endRPO(); bb != be; ++bb)
775 vectorizeBlockInLoop(Legal, *bb, &RdxPHIsToFix);
777 // At this point every instruction in the original loop is widened to
778 // a vector form. We are almost done. Now, we need to fix the PHI nodes
779 // that we vectorized. The PHI nodes are currently empty because we did
780 // not want to introduce cycles. Notice that the remaining PHI nodes
781 // that we need to fix are reduction variables.
783 // Create the 'reduced' values for each of the induction vars.
784 // The reduced values are the vector values that we scalarize and combine
785 // after the loop is finished.
786 for (PhiVector::iterator it = RdxPHIsToFix.begin(), e = RdxPHIsToFix.end();
788 PHINode *RdxPhi = *it;
789 assert(RdxPhi && "Unable to recover vectorized PHI");
791 // Find the reduction variable descriptor.
792 assert(Legal->getReductionVars()->count(RdxPhi) &&
793 "Unable to find the reduction variable");
794 LoopVectorizationLegality::ReductionDescriptor RdxDesc =
795 (*Legal->getReductionVars())[RdxPhi];
797 // We need to generate a reduction vector from the incoming scalar.
798 // To do so, we need to generate the 'identity' vector and overide
799 // one of the elements with the incoming scalar reduction. We need
800 // to do it in the vector-loop preheader.
801 Builder.SetInsertPoint(LoopBypassBlock->getTerminator());
803 // This is the vector-clone of the value that leaves the loop.
804 VectorParts &VectorExit = getVectorValue(RdxDesc.LoopExitInstr);
805 Type *VecTy = VectorExit[0]->getType();
807 // Find the reduction identity variable. Zero for addition, or, xor,
808 // one for multiplication, -1 for And.
809 Constant *Identity = getUniformVector(getReductionIdentity(RdxDesc.Kind),
810 VecTy->getScalarType());
812 // This vector is the Identity vector where the first element is the
813 // incoming scalar reduction.
814 Value *VectorStart = Builder.CreateInsertElement(Identity,
815 RdxDesc.StartValue, Zero);
817 // Fix the vector-loop phi.
818 // We created the induction variable so we know that the
819 // preheader is the first entry.
820 BasicBlock *VecPreheader = Induction->getIncomingBlock(0);
822 // Reductions do not have to start at zero. They can start with
823 // any loop invariant values.
824 VectorParts &VecRdxPhi = WidenMap.get(RdxPhi);
825 BasicBlock *Latch = OrigLoop->getLoopLatch();
826 Value *LoopVal = RdxPhi->getIncomingValueForBlock(Latch);
827 VectorParts &Val = getVectorValue(LoopVal);
828 for (unsigned part = 0; part < UF; ++part) {
829 // Make sure to add the reduction stat value only to the
830 // first unroll part.
831 Value *StartVal = (part == 0) ? VectorStart : Identity;
832 cast<PHINode>(VecRdxPhi[part])->addIncoming(StartVal, VecPreheader);
833 cast<PHINode>(VecRdxPhi[part])->addIncoming(Val[part], LoopVectorBody);
836 // Before each round, move the insertion point right between
837 // the PHIs and the values we are going to write.
838 // This allows us to write both PHINodes and the extractelement
840 Builder.SetInsertPoint(LoopMiddleBlock->getFirstInsertionPt());
842 VectorParts RdxParts;
843 for (unsigned part = 0; part < UF; ++part) {
844 // This PHINode contains the vectorized reduction variable, or
845 // the initial value vector, if we bypass the vector loop.
846 VectorParts &RdxExitVal = getVectorValue(RdxDesc.LoopExitInstr);
847 PHINode *NewPhi = Builder.CreatePHI(VecTy, 2, "rdx.vec.exit.phi");
848 Value *StartVal = (part == 0) ? VectorStart : Identity;
849 NewPhi->addIncoming(StartVal, LoopBypassBlock);
850 NewPhi->addIncoming(RdxExitVal[part], LoopVectorBody);
851 RdxParts.push_back(NewPhi);
854 // Reduce all of the unrolled parts into a single vector.
855 Value *ReducedPartRdx = RdxParts[0];
856 for (unsigned part = 1; part < UF; ++part) {
857 switch (RdxDesc.Kind) {
858 case LoopVectorizationLegality::IntegerAdd:
860 Builder.CreateAdd(RdxParts[part], ReducedPartRdx, "add.rdx");
862 case LoopVectorizationLegality::IntegerMult:
864 Builder.CreateMul(RdxParts[part], ReducedPartRdx, "mul.rdx");
866 case LoopVectorizationLegality::IntegerOr:
868 Builder.CreateOr(RdxParts[part], ReducedPartRdx, "or.rdx");
870 case LoopVectorizationLegality::IntegerAnd:
872 Builder.CreateAnd(RdxParts[part], ReducedPartRdx, "and.rdx");
874 case LoopVectorizationLegality::IntegerXor:
876 Builder.CreateXor(RdxParts[part], ReducedPartRdx, "xor.rdx");
879 llvm_unreachable("Unknown reduction operation");
884 // VF is a power of 2 so we can emit the reduction using log2(VF) shuffles
885 // and vector ops, reducing the set of values being computed by half each
887 assert(isPowerOf2_32(VF) &&
888 "Reduction emission only supported for pow2 vectors!");
889 Value *TmpVec = ReducedPartRdx;
890 SmallVector<Constant*, 32> ShuffleMask(VF, 0);
891 for (unsigned i = VF; i != 1; i >>= 1) {
892 // Move the upper half of the vector to the lower half.
893 for (unsigned j = 0; j != i/2; ++j)
894 ShuffleMask[j] = Builder.getInt32(i/2 + j);
896 // Fill the rest of the mask with undef.
897 std::fill(&ShuffleMask[i/2], ShuffleMask.end(),
898 UndefValue::get(Builder.getInt32Ty()));
901 Builder.CreateShuffleVector(TmpVec,
902 UndefValue::get(TmpVec->getType()),
903 ConstantVector::get(ShuffleMask),
906 // Emit the operation on the shuffled value.
907 switch (RdxDesc.Kind) {
908 case LoopVectorizationLegality::IntegerAdd:
909 TmpVec = Builder.CreateAdd(TmpVec, Shuf, "add.rdx");
911 case LoopVectorizationLegality::IntegerMult:
912 TmpVec = Builder.CreateMul(TmpVec, Shuf, "mul.rdx");
914 case LoopVectorizationLegality::IntegerOr:
915 TmpVec = Builder.CreateOr(TmpVec, Shuf, "or.rdx");
917 case LoopVectorizationLegality::IntegerAnd:
918 TmpVec = Builder.CreateAnd(TmpVec, Shuf, "and.rdx");
920 case LoopVectorizationLegality::IntegerXor:
921 TmpVec = Builder.CreateXor(TmpVec, Shuf, "xor.rdx");
924 llvm_unreachable("Unknown reduction operation");
928 // The result is in the first element of the vector.
929 Value *Scalar0 = Builder.CreateExtractElement(TmpVec, Builder.getInt32(0));
931 // Now, we need to fix the users of the reduction variable
932 // inside and outside of the scalar remainder loop.
933 // We know that the loop is in LCSSA form. We need to update the
934 // PHI nodes in the exit blocks.
935 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
936 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
937 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
938 if (!LCSSAPhi) continue;
940 // All PHINodes need to have a single entry edge, or two if
941 // we already fixed them.
942 assert(LCSSAPhi->getNumIncomingValues() < 3 && "Invalid LCSSA PHI");
944 // We found our reduction value exit-PHI. Update it with the
945 // incoming bypass edge.
946 if (LCSSAPhi->getIncomingValue(0) == RdxDesc.LoopExitInstr) {
947 // Add an edge coming from the bypass.
948 LCSSAPhi->addIncoming(Scalar0, LoopMiddleBlock);
951 }// end of the LCSSA phi scan.
953 // Fix the scalar loop reduction variable with the incoming reduction sum
954 // from the vector body and from the backedge value.
955 int IncomingEdgeBlockIdx =
956 (RdxPhi)->getBasicBlockIndex(OrigLoop->getLoopLatch());
957 assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index");
958 // Pick the other block.
959 int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1);
960 (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, Scalar0);
961 (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
962 }// end of for each redux variable.
964 // The Loop exit block may have single value PHI nodes where the incoming
965 // value is 'undef'. While vectorizing we only handled real values that
966 // were defined inside the loop. Here we handle the 'undef case'.
968 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
969 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
970 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
971 if (!LCSSAPhi) continue;
972 if (LCSSAPhi->getNumIncomingValues() == 1)
973 LCSSAPhi->addIncoming(UndefValue::get(LCSSAPhi->getType()),
978 InnerLoopVectorizer::VectorParts
979 InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
980 assert(std::find(pred_begin(Dst), pred_end(Dst), Src) != pred_end(Dst) &&
983 VectorParts SrcMask = createBlockInMask(Src);
985 // The terminator has to be a branch inst!
986 BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator());
987 assert(BI && "Unexpected terminator found");
989 if (BI->isConditional()) {
990 VectorParts EdgeMask = getVectorValue(BI->getCondition());
992 if (BI->getSuccessor(0) != Dst)
993 for (unsigned part = 0; part < UF; ++part)
994 EdgeMask[part] = Builder.CreateNot(EdgeMask[part]);
996 for (unsigned part = 0; part < UF; ++part)
997 EdgeMask[part] = Builder.CreateAnd(EdgeMask[part], SrcMask[part]);
1004 InnerLoopVectorizer::VectorParts
1005 InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) {
1006 assert(OrigLoop->contains(BB) && "Block is not a part of a loop");
1008 // Loop incoming mask is all-one.
1009 if (OrigLoop->getHeader() == BB) {
1010 Value *C = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 1);
1011 return getVectorValue(C);
1014 // This is the block mask. We OR all incoming edges, and with zero.
1015 Value *Zero = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 0);
1016 VectorParts BlockMask = getVectorValue(Zero);
1019 for (pred_iterator it = pred_begin(BB), e = pred_end(BB); it != e; ++it) {
1020 VectorParts EM = createEdgeMask(*it, BB);
1021 for (unsigned part = 0; part < UF; ++part)
1022 BlockMask[part] = Builder.CreateOr(BlockMask[part], EM[part]);
1029 InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
1030 BasicBlock *BB, PhiVector *PV) {
1031 Constant *Zero = Builder.getInt32(0);
1033 // For each instruction in the old loop.
1034 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
1035 VectorParts &Entry = WidenMap.get(it);
1036 switch (it->getOpcode()) {
1037 case Instruction::Br:
1038 // Nothing to do for PHIs and BR, since we already took care of the
1039 // loop control flow instructions.
1041 case Instruction::PHI:{
1042 PHINode* P = cast<PHINode>(it);
1043 // Handle reduction variables:
1044 if (Legal->getReductionVars()->count(P)) {
1045 for (unsigned part = 0; part < UF; ++part) {
1046 // This is phase one of vectorizing PHIs.
1047 Type *VecTy = VectorType::get(it->getType(), VF);
1048 Entry[part] = PHINode::Create(VecTy, 2, "vec.phi",
1049 LoopVectorBody-> getFirstInsertionPt());
1055 // Check for PHI nodes that are lowered to vector selects.
1056 if (P->getParent() != OrigLoop->getHeader()) {
1057 // We know that all PHIs in non header blocks are converted into
1058 // selects, so we don't have to worry about the insertion order and we
1059 // can just use the builder.
1061 // At this point we generate the predication tree. There may be
1062 // duplications since this is a simple recursive scan, but future
1063 // optimizations will clean it up.
1064 VectorParts Cond = createEdgeMask(P->getIncomingBlock(0),
1067 for (unsigned part = 0; part < UF; ++part) {
1068 VectorParts &In0 = getVectorValue(P->getIncomingValue(0));
1069 VectorParts &In1 = getVectorValue(P->getIncomingValue(1));
1070 Entry[part] = Builder.CreateSelect(Cond[part], In0[part], In1[part],
1076 // This PHINode must be an induction variable.
1077 // Make sure that we know about it.
1078 assert(Legal->getInductionVars()->count(P) &&
1079 "Not an induction variable");
1081 LoopVectorizationLegality::InductionInfo II =
1082 Legal->getInductionVars()->lookup(P);
1085 case LoopVectorizationLegality::NoInduction:
1086 llvm_unreachable("Unknown induction");
1087 case LoopVectorizationLegality::IntInduction: {
1088 assert(P == OldInduction && "Unexpected PHI");
1089 Value *Broadcasted = getBroadcastInstrs(Induction);
1090 // After broadcasting the induction variable we need to make the
1091 // vector consecutive by adding 0, 1, 2 ...
1092 for (unsigned part = 0; part < UF; ++part)
1093 Entry[part] = getConsecutiveVector(Broadcasted, VF * part, false);
1096 case LoopVectorizationLegality::ReverseIntInduction:
1097 case LoopVectorizationLegality::PtrInduction:
1098 // Handle reverse integer and pointer inductions.
1099 Value *StartIdx = 0;
1100 // If we have a single integer induction variable then use it.
1101 // Otherwise, start counting at zero.
1103 LoopVectorizationLegality::InductionInfo OldII =
1104 Legal->getInductionVars()->lookup(OldInduction);
1105 StartIdx = OldII.StartValue;
1107 StartIdx = ConstantInt::get(Induction->getType(), 0);
1109 // This is the normalized GEP that starts counting at zero.
1110 Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
1113 // Handle the reverse integer induction variable case.
1114 if (LoopVectorizationLegality::ReverseIntInduction == II.IK) {
1115 IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType());
1116 Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy,
1118 Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI,
1121 // This is a new value so do not hoist it out.
1122 Value *Broadcasted = getBroadcastInstrs(ReverseInd);
1123 // After broadcasting the induction variable we need to make the
1124 // vector consecutive by adding ... -3, -2, -1, 0.
1125 for (unsigned part = 0; part < UF; ++part)
1126 Entry[part] = getConsecutiveVector(Broadcasted, -VF * part, true);
1130 // Handle the pointer induction variable case.
1131 assert(P->getType()->isPointerTy() && "Unexpected type.");
1133 // This is the vector of results. Notice that we don't generate
1134 // vector geps because scalar geps result in better code.
1135 for (unsigned part = 0; part < UF; ++part) {
1136 Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
1137 for (unsigned int i = 0; i < VF; ++i) {
1138 Constant *Idx = ConstantInt::get(Induction->getType(),
1140 Value *GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx,
1142 Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
1144 VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
1145 Builder.getInt32(i),
1148 Entry[part] = VecVal;
1155 case Instruction::Add:
1156 case Instruction::FAdd:
1157 case Instruction::Sub:
1158 case Instruction::FSub:
1159 case Instruction::Mul:
1160 case Instruction::FMul:
1161 case Instruction::UDiv:
1162 case Instruction::SDiv:
1163 case Instruction::FDiv:
1164 case Instruction::URem:
1165 case Instruction::SRem:
1166 case Instruction::FRem:
1167 case Instruction::Shl:
1168 case Instruction::LShr:
1169 case Instruction::AShr:
1170 case Instruction::And:
1171 case Instruction::Or:
1172 case Instruction::Xor: {
1173 // Just widen binops.
1174 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(it);
1175 VectorParts &A = getVectorValue(it->getOperand(0));
1176 VectorParts &B = getVectorValue(it->getOperand(1));
1178 // Use this vector value for all users of the original instruction.
1179 for (unsigned Part = 0; Part < UF; ++Part) {
1180 Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A[Part], B[Part]);
1182 // Update the NSW, NUW and Exact flags.
1183 BinaryOperator *VecOp = cast<BinaryOperator>(V);
1184 if (isa<OverflowingBinaryOperator>(BinOp)) {
1185 VecOp->setHasNoSignedWrap(BinOp->hasNoSignedWrap());
1186 VecOp->setHasNoUnsignedWrap(BinOp->hasNoUnsignedWrap());
1188 if (isa<PossiblyExactOperator>(VecOp))
1189 VecOp->setIsExact(BinOp->isExact());
1195 case Instruction::Select: {
1197 // If the selector is loop invariant we can create a select
1198 // instruction with a scalar condition. Otherwise, use vector-select.
1199 bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(it->getOperand(0)),
1202 // The condition can be loop invariant but still defined inside the
1203 // loop. This means that we can't just use the original 'cond' value.
1204 // We have to take the 'vectorized' value and pick the first lane.
1205 // Instcombine will make this a no-op.
1206 VectorParts &Cond = getVectorValue(it->getOperand(0));
1207 VectorParts &Op0 = getVectorValue(it->getOperand(1));
1208 VectorParts &Op1 = getVectorValue(it->getOperand(2));
1209 Value *ScalarCond = Builder.CreateExtractElement(Cond[0],
1210 Builder.getInt32(0));
1211 for (unsigned Part = 0; Part < UF; ++Part) {
1212 Entry[Part] = Builder.CreateSelect(
1213 InvariantCond ? ScalarCond : Cond[Part],
1220 case Instruction::ICmp:
1221 case Instruction::FCmp: {
1222 // Widen compares. Generate vector compares.
1223 bool FCmp = (it->getOpcode() == Instruction::FCmp);
1224 CmpInst *Cmp = dyn_cast<CmpInst>(it);
1225 VectorParts &A = getVectorValue(it->getOperand(0));
1226 VectorParts &B = getVectorValue(it->getOperand(1));
1227 for (unsigned Part = 0; Part < UF; ++Part) {
1230 C = Builder.CreateFCmp(Cmp->getPredicate(), A[Part], B[Part]);
1232 C = Builder.CreateICmp(Cmp->getPredicate(), A[Part], B[Part]);
1238 case Instruction::Store: {
1239 // Attempt to issue a wide store.
1240 StoreInst *SI = dyn_cast<StoreInst>(it);
1241 Type *StTy = VectorType::get(SI->getValueOperand()->getType(), VF);
1242 Value *Ptr = SI->getPointerOperand();
1243 unsigned Alignment = SI->getAlignment();
1245 assert(!Legal->isUniform(Ptr) &&
1246 "We do not allow storing to uniform addresses");
1249 int Stride = Legal->isConsecutivePtr(Ptr);
1250 bool Reverse = Stride < 0;
1252 scalarizeInstruction(it);
1256 // Handle consecutive stores.
1258 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
1260 // The last index does not have to be the induction. It can be
1261 // consecutive and be a function of the index. For example A[I+1];
1262 unsigned NumOperands = Gep->getNumOperands();
1264 Value *LastGepOperand = Gep->getOperand(NumOperands - 1);
1265 VectorParts &GEPParts = getVectorValue(LastGepOperand);
1266 Value *LastIndex = GEPParts[0];
1267 LastIndex = Builder.CreateExtractElement(LastIndex, Zero);
1269 // Create the new GEP with the new induction variable.
1270 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
1271 Gep2->setOperand(NumOperands - 1, LastIndex);
1272 Ptr = Builder.Insert(Gep2);
1274 // Use the induction element ptr.
1275 assert(isa<PHINode>(Ptr) && "Invalid induction ptr");
1276 VectorParts &PtrVal = getVectorValue(Ptr);
1277 Ptr = Builder.CreateExtractElement(PtrVal[0], Zero);
1280 VectorParts &StoredVal = getVectorValue(SI->getValueOperand());
1281 for (unsigned Part = 0; Part < UF; ++Part) {
1282 // Calculate the pointer for the specific unroll-part.
1283 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1286 // If we store to reverse consecutive memory locations then we need
1287 // to reverse the order of elements in the stored value.
1288 StoredVal[Part] = reverseVector(StoredVal[Part]);
1289 // If the address is consecutive but reversed, then the
1290 // wide store needs to start at the last vector element.
1291 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1292 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1295 Value *VecPtr = Builder.CreateBitCast(PartPtr, StTy->getPointerTo());
1296 Builder.CreateStore(StoredVal[Part], VecPtr)->setAlignment(Alignment);
1300 case Instruction::Load: {
1301 // Attempt to issue a wide load.
1302 LoadInst *LI = dyn_cast<LoadInst>(it);
1303 Type *RetTy = VectorType::get(LI->getType(), VF);
1304 Value *Ptr = LI->getPointerOperand();
1305 unsigned Alignment = LI->getAlignment();
1307 // If the pointer is loop invariant or if it is non consecutive,
1308 // scalarize the load.
1309 int Stride = Legal->isConsecutivePtr(Ptr);
1310 bool Reverse = Stride < 0;
1311 if (Legal->isUniform(Ptr) || Stride == 0) {
1312 scalarizeInstruction(it);
1316 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
1318 // The last index does not have to be the induction. It can be
1319 // consecutive and be a function of the index. For example A[I+1];
1320 unsigned NumOperands = Gep->getNumOperands();
1322 Value *LastGepOperand = Gep->getOperand(NumOperands - 1);
1323 VectorParts &GEPParts = getVectorValue(LastGepOperand);
1324 Value *LastIndex = GEPParts[0];
1325 LastIndex = Builder.CreateExtractElement(LastIndex, Zero);
1327 // Create the new GEP with the new induction variable.
1328 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
1329 Gep2->setOperand(NumOperands - 1, LastIndex);
1330 Ptr = Builder.Insert(Gep2);
1332 // Use the induction element ptr.
1333 assert(isa<PHINode>(Ptr) && "Invalid induction ptr");
1334 VectorParts &PtrVal = getVectorValue(Ptr);
1335 Ptr = Builder.CreateExtractElement(PtrVal[0], Zero);
1338 for (unsigned Part = 0; Part < UF; ++Part) {
1339 // Calculate the pointer for the specific unroll-part.
1340 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1343 // If the address is consecutive but reversed, then the
1344 // wide store needs to start at the last vector element.
1345 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1346 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1349 Value *VecPtr = Builder.CreateBitCast(PartPtr, RetTy->getPointerTo());
1350 Value *LI = Builder.CreateLoad(VecPtr, "wide.load");
1351 cast<LoadInst>(LI)->setAlignment(Alignment);
1352 Entry[Part] = Reverse ? reverseVector(LI) : LI;
1356 case Instruction::ZExt:
1357 case Instruction::SExt:
1358 case Instruction::FPToUI:
1359 case Instruction::FPToSI:
1360 case Instruction::FPExt:
1361 case Instruction::PtrToInt:
1362 case Instruction::IntToPtr:
1363 case Instruction::SIToFP:
1364 case Instruction::UIToFP:
1365 case Instruction::Trunc:
1366 case Instruction::FPTrunc:
1367 case Instruction::BitCast: {
1368 CastInst *CI = dyn_cast<CastInst>(it);
1369 /// Optimize the special case where the source is the induction
1370 /// variable. Notice that we can only optimize the 'trunc' case
1371 /// because: a. FP conversions lose precision, b. sext/zext may wrap,
1372 /// c. other casts depend on pointer size.
1373 if (CI->getOperand(0) == OldInduction &&
1374 it->getOpcode() == Instruction::Trunc) {
1375 Value *ScalarCast = Builder.CreateCast(CI->getOpcode(), Induction,
1377 Value *Broadcasted = getBroadcastInstrs(ScalarCast);
1378 for (unsigned Part = 0; Part < UF; ++Part)
1379 Entry[Part] = getConsecutiveVector(Broadcasted, VF * Part, false);
1382 /// Vectorize casts.
1383 Type *DestTy = VectorType::get(CI->getType()->getScalarType(), VF);
1385 VectorParts &A = getVectorValue(it->getOperand(0));
1386 for (unsigned Part = 0; Part < UF; ++Part)
1387 Entry[Part] = Builder.CreateCast(CI->getOpcode(), A[Part], DestTy);
1391 case Instruction::Call: {
1392 assert(isTriviallyVectorizableIntrinsic(it));
1393 Module *M = BB->getParent()->getParent();
1394 IntrinsicInst *II = cast<IntrinsicInst>(it);
1395 Intrinsic::ID ID = II->getIntrinsicID();
1396 for (unsigned Part = 0; Part < UF; ++Part) {
1397 SmallVector<Value*, 4> Args;
1398 for (unsigned i = 0, ie = II->getNumArgOperands(); i != ie; ++i) {
1399 VectorParts &Arg = getVectorValue(II->getArgOperand(i));
1400 Args.push_back(Arg[Part]);
1402 Type *Tys[] = { VectorType::get(II->getType()->getScalarType(), VF) };
1403 Function *F = Intrinsic::getDeclaration(M, ID, Tys);
1404 Entry[Part] = Builder.CreateCall(F, Args);
1410 // All other instructions are unsupported. Scalarize them.
1411 scalarizeInstruction(it);
1414 }// end of for_each instr.
1417 void InnerLoopVectorizer::updateAnalysis() {
1418 // Forget the original basic block.
1419 SE->forgetLoop(OrigLoop);
1421 // Update the dominator tree information.
1422 assert(DT->properlyDominates(LoopBypassBlock, LoopExitBlock) &&
1423 "Entry does not dominate exit.");
1425 DT->addNewBlock(LoopVectorPreHeader, LoopBypassBlock);
1426 DT->addNewBlock(LoopVectorBody, LoopVectorPreHeader);
1427 DT->addNewBlock(LoopMiddleBlock, LoopBypassBlock);
1428 DT->addNewBlock(LoopScalarPreHeader, LoopMiddleBlock);
1429 DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader);
1430 DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock);
1432 DEBUG(DT->verifyAnalysis());
1435 bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
1436 if (!EnableIfConversion)
1439 assert(TheLoop->getNumBlocks() > 1 && "Single block loops are vectorizable");
1440 std::vector<BasicBlock*> &LoopBlocks = TheLoop->getBlocksVector();
1442 // Collect the blocks that need predication.
1443 for (unsigned i = 0, e = LoopBlocks.size(); i < e; ++i) {
1444 BasicBlock *BB = LoopBlocks[i];
1446 // We don't support switch statements inside loops.
1447 if (!isa<BranchInst>(BB->getTerminator()))
1450 // We must have at most two predecessors because we need to convert
1451 // all PHIs to selects.
1452 unsigned Preds = std::distance(pred_begin(BB), pred_end(BB));
1456 // We must be able to predicate all blocks that need to be predicated.
1457 if (blockNeedsPredication(BB) && !blockCanBePredicated(BB))
1461 // We can if-convert this loop.
1465 bool LoopVectorizationLegality::canVectorize() {
1466 assert(TheLoop->getLoopPreheader() && "No preheader!!");
1468 // We can only vectorize innermost loops.
1469 if (TheLoop->getSubLoopsVector().size())
1472 // We must have a single backedge.
1473 if (TheLoop->getNumBackEdges() != 1)
1476 // We must have a single exiting block.
1477 if (!TheLoop->getExitingBlock())
1480 unsigned NumBlocks = TheLoop->getNumBlocks();
1482 // Check if we can if-convert non single-bb loops.
1483 if (NumBlocks != 1 && !canVectorizeWithIfConvert()) {
1484 DEBUG(dbgs() << "LV: Can't if-convert the loop.\n");
1488 // We need to have a loop header.
1489 BasicBlock *Latch = TheLoop->getLoopLatch();
1490 DEBUG(dbgs() << "LV: Found a loop: " <<
1491 TheLoop->getHeader()->getName() << "\n");
1493 // ScalarEvolution needs to be able to find the exit count.
1494 const SCEV *ExitCount = SE->getExitCount(TheLoop, Latch);
1495 if (ExitCount == SE->getCouldNotCompute()) {
1496 DEBUG(dbgs() << "LV: SCEV could not compute the loop exit count.\n");
1500 // Do not loop-vectorize loops with a tiny trip count.
1501 unsigned TC = SE->getSmallConstantTripCount(TheLoop, Latch);
1502 if (TC > 0u && TC < TinyTripCountThreshold) {
1503 DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " <<
1504 "This loop is not worth vectorizing.\n");
1508 // Check if we can vectorize the instructions and CFG in this loop.
1509 if (!canVectorizeInstrs()) {
1510 DEBUG(dbgs() << "LV: Can't vectorize the instructions or CFG\n");
1514 // Go over each instruction and look at memory deps.
1515 if (!canVectorizeMemory()) {
1516 DEBUG(dbgs() << "LV: Can't vectorize due to memory conflicts\n");
1520 // Collect all of the variables that remain uniform after vectorization.
1521 collectLoopUniforms();
1523 DEBUG(dbgs() << "LV: We can vectorize this loop" <<
1524 (PtrRtCheck.Need ? " (with a runtime bound check)" : "")
1527 // Okay! We can vectorize. At this point we don't have any other mem analysis
1528 // which may limit our maximum vectorization factor, so just return true with
1533 bool LoopVectorizationLegality::canVectorizeInstrs() {
1534 BasicBlock *PreHeader = TheLoop->getLoopPreheader();
1535 BasicBlock *Header = TheLoop->getHeader();
1537 // For each block in the loop.
1538 for (Loop::block_iterator bb = TheLoop->block_begin(),
1539 be = TheLoop->block_end(); bb != be; ++bb) {
1541 // Scan the instructions in the block and look for hazards.
1542 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
1545 if (PHINode *Phi = dyn_cast<PHINode>(it)) {
1546 // This should not happen because the loop should be normalized.
1547 if (Phi->getNumIncomingValues() != 2) {
1548 DEBUG(dbgs() << "LV: Found an invalid PHI.\n");
1552 // Check that this PHI type is allowed.
1553 if (!Phi->getType()->isIntegerTy() &&
1554 !Phi->getType()->isPointerTy()) {
1555 DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
1559 // If this PHINode is not in the header block, then we know that we
1560 // can convert it to select during if-conversion. No need to check if
1561 // the PHIs in this block are induction or reduction variables.
1565 // This is the value coming from the preheader.
1566 Value *StartValue = Phi->getIncomingValueForBlock(PreHeader);
1567 // Check if this is an induction variable.
1568 InductionKind IK = isInductionVariable(Phi);
1570 if (NoInduction != IK) {
1571 // Int inductions are special because we only allow one IV.
1572 if (IK == IntInduction) {
1574 DEBUG(dbgs() << "LV: Found too many inductions."<< *Phi <<"\n");
1580 DEBUG(dbgs() << "LV: Found an induction variable.\n");
1581 Inductions[Phi] = InductionInfo(StartValue, IK);
1585 if (AddReductionVar(Phi, IntegerAdd)) {
1586 DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n");
1589 if (AddReductionVar(Phi, IntegerMult)) {
1590 DEBUG(dbgs() << "LV: Found a MUL reduction PHI."<< *Phi <<"\n");
1593 if (AddReductionVar(Phi, IntegerOr)) {
1594 DEBUG(dbgs() << "LV: Found an OR reduction PHI."<< *Phi <<"\n");
1597 if (AddReductionVar(Phi, IntegerAnd)) {
1598 DEBUG(dbgs() << "LV: Found an AND reduction PHI."<< *Phi <<"\n");
1601 if (AddReductionVar(Phi, IntegerXor)) {
1602 DEBUG(dbgs() << "LV: Found a XOR reduction PHI."<< *Phi <<"\n");
1606 DEBUG(dbgs() << "LV: Found an unidentified PHI."<< *Phi <<"\n");
1608 }// end of PHI handling
1610 // We still don't handle functions.
1611 CallInst *CI = dyn_cast<CallInst>(it);
1612 if (CI && !isTriviallyVectorizableIntrinsic(it)) {
1613 DEBUG(dbgs() << "LV: Found a call site.\n");
1617 // Check that the instruction return type is vectorizable.
1618 if (!VectorType::isValidElementType(it->getType()) &&
1619 !it->getType()->isVoidTy()) {
1620 DEBUG(dbgs() << "LV: Found unvectorizable type." << "\n");
1624 // Check that the stored type is vectorizable.
1625 if (StoreInst *ST = dyn_cast<StoreInst>(it)) {
1626 Type *T = ST->getValueOperand()->getType();
1627 if (!VectorType::isValidElementType(T))
1631 // Reduction instructions are allowed to have exit users.
1632 // All other instructions must not have external users.
1633 if (!AllowedExit.count(it))
1634 //Check that all of the users of the loop are inside the BB.
1635 for (Value::use_iterator I = it->use_begin(), E = it->use_end();
1637 Instruction *U = cast<Instruction>(*I);
1638 // This user may be a reduction exit value.
1639 if (!TheLoop->contains(U)) {
1640 DEBUG(dbgs() << "LV: Found an outside user for : "<< *U << "\n");
1649 DEBUG(dbgs() << "LV: Did not find one integer induction var.\n");
1650 assert(getInductionVars()->size() && "No induction variables");
1656 void LoopVectorizationLegality::collectLoopUniforms() {
1657 // We now know that the loop is vectorizable!
1658 // Collect variables that will remain uniform after vectorization.
1659 std::vector<Value*> Worklist;
1660 BasicBlock *Latch = TheLoop->getLoopLatch();
1662 // Start with the conditional branch and walk up the block.
1663 Worklist.push_back(Latch->getTerminator()->getOperand(0));
1665 while (Worklist.size()) {
1666 Instruction *I = dyn_cast<Instruction>(Worklist.back());
1667 Worklist.pop_back();
1669 // Look at instructions inside this loop.
1670 // Stop when reaching PHI nodes.
1671 // TODO: we need to follow values all over the loop, not only in this block.
1672 if (!I || !TheLoop->contains(I) || isa<PHINode>(I))
1675 // This is a known uniform.
1678 // Insert all operands.
1679 for (int i = 0, Op = I->getNumOperands(); i < Op; ++i) {
1680 Worklist.push_back(I->getOperand(i));
1685 bool LoopVectorizationLegality::canVectorizeMemory() {
1686 typedef SmallVector<Value*, 16> ValueVector;
1687 typedef SmallPtrSet<Value*, 16> ValueSet;
1688 // Holds the Load and Store *instructions*.
1691 PtrRtCheck.Pointers.clear();
1692 PtrRtCheck.Need = false;
1695 for (Loop::block_iterator bb = TheLoop->block_begin(),
1696 be = TheLoop->block_end(); bb != be; ++bb) {
1698 // Scan the BB and collect legal loads and stores.
1699 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
1702 // If this is a load, save it. If this instruction can read from memory
1703 // but is not a load, then we quit. Notice that we don't handle function
1704 // calls that read or write.
1705 if (it->mayReadFromMemory()) {
1706 LoadInst *Ld = dyn_cast<LoadInst>(it);
1707 if (!Ld) return false;
1708 if (!Ld->isSimple()) {
1709 DEBUG(dbgs() << "LV: Found a non-simple load.\n");
1712 Loads.push_back(Ld);
1716 // Save 'store' instructions. Abort if other instructions write to memory.
1717 if (it->mayWriteToMemory()) {
1718 StoreInst *St = dyn_cast<StoreInst>(it);
1719 if (!St) return false;
1720 if (!St->isSimple()) {
1721 DEBUG(dbgs() << "LV: Found a non-simple store.\n");
1724 Stores.push_back(St);
1729 // Now we have two lists that hold the loads and the stores.
1730 // Next, we find the pointers that they use.
1732 // Check if we see any stores. If there are no stores, then we don't
1733 // care if the pointers are *restrict*.
1734 if (!Stores.size()) {
1735 DEBUG(dbgs() << "LV: Found a read-only loop!\n");
1739 // Holds the read and read-write *pointers* that we find.
1741 ValueVector ReadWrites;
1743 // Holds the analyzed pointers. We don't want to call GetUnderlyingObjects
1744 // multiple times on the same object. If the ptr is accessed twice, once
1745 // for read and once for write, it will only appear once (on the write
1746 // list). This is okay, since we are going to check for conflicts between
1747 // writes and between reads and writes, but not between reads and reads.
1750 ValueVector::iterator I, IE;
1751 for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
1752 StoreInst *ST = cast<StoreInst>(*I);
1753 Value* Ptr = ST->getPointerOperand();
1755 if (isUniform(Ptr)) {
1756 DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n");
1760 // If we did *not* see this pointer before, insert it to
1761 // the read-write list. At this phase it is only a 'write' list.
1762 if (Seen.insert(Ptr))
1763 ReadWrites.push_back(Ptr);
1766 for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
1767 LoadInst *LD = cast<LoadInst>(*I);
1768 Value* Ptr = LD->getPointerOperand();
1769 // If we did *not* see this pointer before, insert it to the
1770 // read list. If we *did* see it before, then it is already in
1771 // the read-write list. This allows us to vectorize expressions
1772 // such as A[i] += x; Because the address of A[i] is a read-write
1773 // pointer. This only works if the index of A[i] is consecutive.
1774 // If the address of i is unknown (for example A[B[i]]) then we may
1775 // read a few words, modify, and write a few words, and some of the
1776 // words may be written to the same address.
1777 if (Seen.insert(Ptr) || 0 == isConsecutivePtr(Ptr))
1778 Reads.push_back(Ptr);
1781 // If we write (or read-write) to a single destination and there are no
1782 // other reads in this loop then is it safe to vectorize.
1783 if (ReadWrites.size() == 1 && Reads.size() == 0) {
1784 DEBUG(dbgs() << "LV: Found a write-only loop!\n");
1788 // Find pointers with computable bounds. We are going to use this information
1789 // to place a runtime bound check.
1790 bool CanDoRT = true;
1791 for (I = ReadWrites.begin(), IE = ReadWrites.end(); I != IE; ++I)
1792 if (hasComputableBounds(*I)) {
1793 PtrRtCheck.insert(SE, TheLoop, *I);
1794 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n");
1799 for (I = Reads.begin(), IE = Reads.end(); I != IE; ++I)
1800 if (hasComputableBounds(*I)) {
1801 PtrRtCheck.insert(SE, TheLoop, *I);
1802 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n");
1808 // Check that we did not collect too many pointers or found a
1809 // unsizeable pointer.
1810 if (!CanDoRT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) {
1816 DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
1819 bool NeedRTCheck = false;
1821 // Now that the pointers are in two lists (Reads and ReadWrites), we
1822 // can check that there are no conflicts between each of the writes and
1823 // between the writes to the reads.
1824 ValueSet WriteObjects;
1825 ValueVector TempObjects;
1827 // Check that the read-writes do not conflict with other read-write
1829 bool AllWritesIdentified = true;
1830 for (I = ReadWrites.begin(), IE = ReadWrites.end(); I != IE; ++I) {
1831 GetUnderlyingObjects(*I, TempObjects, DL);
1832 for (ValueVector::iterator it=TempObjects.begin(), e=TempObjects.end();
1834 if (!isIdentifiedObject(*it)) {
1835 DEBUG(dbgs() << "LV: Found an unidentified write ptr:"<< **it <<"\n");
1837 AllWritesIdentified = false;
1839 if (!WriteObjects.insert(*it)) {
1840 DEBUG(dbgs() << "LV: Found a possible write-write reorder:"
1845 TempObjects.clear();
1848 /// Check that the reads don't conflict with the read-writes.
1849 for (I = Reads.begin(), IE = Reads.end(); I != IE; ++I) {
1850 GetUnderlyingObjects(*I, TempObjects, DL);
1851 for (ValueVector::iterator it=TempObjects.begin(), e=TempObjects.end();
1853 // If all of the writes are identified then we don't care if the read
1854 // pointer is identified or not.
1855 if (!AllWritesIdentified && !isIdentifiedObject(*it)) {
1856 DEBUG(dbgs() << "LV: Found an unidentified read ptr:"<< **it <<"\n");
1859 if (WriteObjects.count(*it)) {
1860 DEBUG(dbgs() << "LV: Found a possible read/write reorder:"
1865 TempObjects.clear();
1868 PtrRtCheck.Need = NeedRTCheck;
1869 if (NeedRTCheck && !CanDoRT) {
1870 DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
1871 "the array bounds.\n");
1876 DEBUG(dbgs() << "LV: We "<< (NeedRTCheck ? "" : "don't") <<
1877 " need a runtime memory check.\n");
1881 bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
1882 ReductionKind Kind) {
1883 if (Phi->getNumIncomingValues() != 2)
1886 // Reduction variables are only found in the loop header block.
1887 if (Phi->getParent() != TheLoop->getHeader())
1890 // Obtain the reduction start value from the value that comes from the loop
1892 Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader());
1894 // ExitInstruction is the single value which is used outside the loop.
1895 // We only allow for a single reduction value to be used outside the loop.
1896 // This includes users of the reduction, variables (which form a cycle
1897 // which ends in the phi node).
1898 Instruction *ExitInstruction = 0;
1900 // Iter is our iterator. We start with the PHI node and scan for all of the
1901 // users of this instruction. All users must be instructions that can be
1902 // used as reduction variables (such as ADD). We may have a single
1903 // out-of-block user. The cycle must end with the original PHI.
1904 Instruction *Iter = Phi;
1906 // If the instruction has no users then this is a broken
1907 // chain and can't be a reduction variable.
1908 if (Iter->use_empty())
1911 // Did we find a user inside this loop already ?
1912 bool FoundInBlockUser = false;
1913 // Did we reach the initial PHI node already ?
1914 bool FoundStartPHI = false;
1916 // For each of the *users* of iter.
1917 for (Value::use_iterator it = Iter->use_begin(), e = Iter->use_end();
1919 Instruction *U = cast<Instruction>(*it);
1920 // We already know that the PHI is a user.
1922 FoundStartPHI = true;
1926 // Check if we found the exit user.
1927 BasicBlock *Parent = U->getParent();
1928 if (!TheLoop->contains(Parent)) {
1929 // Exit if you find multiple outside users.
1930 if (ExitInstruction != 0)
1932 ExitInstruction = Iter;
1935 // We allow in-loop PHINodes which are not the original reduction PHI
1936 // node. If this PHI is the only user of Iter (happens in IF w/ no ELSE
1937 // structure) then don't skip this PHI.
1938 if (isa<PHINode>(Iter) && isa<PHINode>(U) &&
1939 U->getParent() != TheLoop->getHeader() &&
1940 TheLoop->contains(U) &&
1941 Iter->getNumUses() > 1)
1944 // We can't have multiple inside users.
1945 if (FoundInBlockUser)
1947 FoundInBlockUser = true;
1949 // Any reduction instr must be of one of the allowed kinds.
1950 if (!isReductionInstr(U, Kind))
1953 // Reductions of instructions such as Div, and Sub is only
1954 // possible if the LHS is the reduction variable.
1955 if (!U->isCommutative() && U->getOperand(0) != Iter)
1961 // We found a reduction var if we have reached the original
1962 // phi node and we only have a single instruction with out-of-loop
1964 if (FoundStartPHI && ExitInstruction) {
1965 // This instruction is allowed to have out-of-loop users.
1966 AllowedExit.insert(ExitInstruction);
1968 // Save the description of this reduction variable.
1969 ReductionDescriptor RD(RdxStart, ExitInstruction, Kind);
1970 Reductions[Phi] = RD;
1974 // If we've reached the start PHI but did not find an outside user then
1975 // this is dead code. Abort.
1982 LoopVectorizationLegality::isReductionInstr(Instruction *I,
1983 ReductionKind Kind) {
1984 switch (I->getOpcode()) {
1987 case Instruction::PHI:
1990 case Instruction::Sub:
1991 case Instruction::Add:
1992 return Kind == IntegerAdd;
1993 case Instruction::SDiv:
1994 case Instruction::UDiv:
1995 case Instruction::Mul:
1996 return Kind == IntegerMult;
1997 case Instruction::And:
1998 return Kind == IntegerAnd;
1999 case Instruction::Or:
2000 return Kind == IntegerOr;
2001 case Instruction::Xor:
2002 return Kind == IntegerXor;
2006 LoopVectorizationLegality::InductionKind
2007 LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
2008 Type *PhiTy = Phi->getType();
2009 // We only handle integer and pointer inductions variables.
2010 if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
2013 // Check that the PHI is consecutive and starts at zero.
2014 const SCEV *PhiScev = SE->getSCEV(Phi);
2015 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
2017 DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
2020 const SCEV *Step = AR->getStepRecurrence(*SE);
2022 // Integer inductions need to have a stride of one.
2023 if (PhiTy->isIntegerTy()) {
2025 return IntInduction;
2026 if (Step->isAllOnesValue())
2027 return ReverseIntInduction;
2031 // Calculate the pointer stride and check if it is consecutive.
2032 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
2036 assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
2037 uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType());
2038 if (C->getValue()->equalsInt(Size))
2039 return PtrInduction;
2044 bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
2045 Value *In0 = const_cast<Value*>(V);
2046 PHINode *PN = dyn_cast_or_null<PHINode>(In0);
2050 return Inductions.count(PN);
2053 bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
2054 assert(TheLoop->contains(BB) && "Unknown block used");
2056 // Blocks that do not dominate the latch need predication.
2057 BasicBlock* Latch = TheLoop->getLoopLatch();
2058 return !DT->dominates(BB, Latch);
2061 bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB) {
2062 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
2063 // We don't predicate loads/stores at the moment.
2064 if (it->mayReadFromMemory() || it->mayWriteToMemory() || it->mayThrow())
2067 // The instructions below can trap.
2068 switch (it->getOpcode()) {
2070 case Instruction::UDiv:
2071 case Instruction::SDiv:
2072 case Instruction::URem:
2073 case Instruction::SRem:
2081 bool LoopVectorizationLegality::hasComputableBounds(Value *Ptr) {
2082 const SCEV *PhiScev = SE->getSCEV(Ptr);
2083 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
2087 return AR->isAffine();
2091 LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
2093 if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
2094 DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
2098 // Find the trip count.
2099 unsigned TC = SE->getSmallConstantTripCount(TheLoop, TheLoop->getLoopLatch());
2100 DEBUG(dbgs() << "LV: Found trip count:"<<TC<<"\n");
2102 unsigned VF = MaxVectorSize;
2104 // If we optimize the program for size, avoid creating the tail loop.
2106 // If we are unable to calculate the trip count then don't try to vectorize.
2108 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
2112 // Find the maximum SIMD width that can fit within the trip count.
2113 VF = TC % MaxVectorSize;
2118 // If the trip count that we found modulo the vectorization factor is not
2119 // zero then we require a tail.
2121 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
2127 assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
2128 DEBUG(dbgs() << "LV: Using user VF "<<UserVF<<".\n");
2134 DEBUG(dbgs() << "LV: No vector target information. Not vectorizing. \n");
2138 float Cost = expectedCost(1);
2140 DEBUG(dbgs() << "LV: Scalar loop costs: "<< (int)Cost << ".\n");
2141 for (unsigned i=2; i <= VF; i*=2) {
2142 // Notice that the vector loop needs to be executed less times, so
2143 // we need to divide the cost of the vector loops by the width of
2144 // the vector elements.
2145 float VectorCost = expectedCost(i) / (float)i;
2146 DEBUG(dbgs() << "LV: Vector loop of width "<< i << " costs: " <<
2147 (int)VectorCost << ".\n");
2148 if (VectorCost < Cost) {
2154 DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n");
2159 LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
2161 // Use the user preference, unless 'auto' is selected.
2165 // When we optimize for size we don't unroll.
2169 unsigned TargetVectorRegisters = TTI->getNumberOfRegisters(true);
2170 DEBUG(dbgs() << "LV: The target has " << TargetVectorRegisters <<
2171 " vector registers\n");
2173 LoopVectorizationCostModel::RegisterUsage R = calculateRegisterUsage();
2174 // We divide by these constants so assume that we have at least one
2175 // instruction that uses at least one register.
2176 R.MaxLocalUsers = std::max(R.MaxLocalUsers, 1U);
2177 R.NumInstructions = std::max(R.NumInstructions, 1U);
2179 // We calculate the unroll factor using the following formula.
2180 // Subtract the number of loop invariants from the number of available
2181 // registers. These registers are used by all of the unrolled instances.
2182 // Next, divide the remaining registers by the number of registers that is
2183 // required by the loop, in order to estimate how many parallel instances
2184 // fit without causing spills.
2185 unsigned UF = (TargetVectorRegisters - R.LoopInvariantRegs) / R.MaxLocalUsers;
2187 // We don't want to unroll the loops to the point where they do not fit into
2188 // the decoded cache. Assume that we only allow 32 IR instructions.
2189 UF = std::min(UF, (32 / R.NumInstructions));
2191 // Clamp the unroll factor ranges to reasonable factors.
2192 if (UF > MaxUnrollSize)
2200 LoopVectorizationCostModel::RegisterUsage
2201 LoopVectorizationCostModel::calculateRegisterUsage() {
2202 // This function calculates the register usage by measuring the highest number
2203 // of values that are alive at a single location. Obviously, this is a very
2204 // rough estimation. We scan the loop in a topological order in order and
2205 // assign a number to each instruction. We use RPO to ensure that defs are
2206 // met before their users. We assume that each instruction that has in-loop
2207 // users starts an interval. We record every time that an in-loop value is
2208 // used, so we have a list of the first and last occurrences of each
2209 // instruction. Next, we transpose this data structure into a multi map that
2210 // holds the list of intervals that *end* at a specific location. This multi
2211 // map allows us to perform a linear search. We scan the instructions linearly
2212 // and record each time that a new interval starts, by placing it in a set.
2213 // If we find this value in the multi-map then we remove it from the set.
2214 // The max register usage is the maximum size of the set.
2215 // We also search for instructions that are defined outside the loop, but are
2216 // used inside the loop. We need this number separately from the max-interval
2217 // usage number because when we unroll, loop-invariant values do not take
2219 LoopBlocksDFS DFS(TheLoop);
2223 R.NumInstructions = 0;
2225 // Each 'key' in the map opens a new interval. The values
2226 // of the map are the index of the 'last seen' usage of the
2227 // instruction that is the key.
2228 typedef DenseMap<Instruction*, unsigned> IntervalMap;
2229 // Maps instruction to its index.
2230 DenseMap<unsigned, Instruction*> IdxToInstr;
2231 // Marks the end of each interval.
2232 IntervalMap EndPoint;
2233 // Saves the list of instruction indices that are used in the loop.
2234 SmallSet<Instruction*, 8> Ends;
2235 // Saves the list of values that are used in the loop but are
2236 // defined outside the loop, such as arguments and constants.
2237 SmallPtrSet<Value*, 8> LoopInvariants;
2240 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
2241 be = DFS.endRPO(); bb != be; ++bb) {
2242 R.NumInstructions += (*bb)->size();
2243 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
2245 Instruction *I = it;
2246 IdxToInstr[Index++] = I;
2248 // Save the end location of each USE.
2249 for (unsigned i = 0; i < I->getNumOperands(); ++i) {
2250 Value *U = I->getOperand(i);
2251 Instruction *Instr = dyn_cast<Instruction>(U);
2253 // Ignore non-instruction values such as arguments, constants, etc.
2254 if (!Instr) continue;
2256 // If this instruction is outside the loop then record it and continue.
2257 if (!TheLoop->contains(Instr)) {
2258 LoopInvariants.insert(Instr);
2262 // Overwrite previous end points.
2263 EndPoint[Instr] = Index;
2269 // Saves the list of intervals that end with the index in 'key'.
2270 typedef SmallVector<Instruction*, 2> InstrList;
2271 DenseMap<unsigned, InstrList> TransposeEnds;
2273 // Transpose the EndPoints to a list of values that end at each index.
2274 for (IntervalMap::iterator it = EndPoint.begin(), e = EndPoint.end();
2276 TransposeEnds[it->second].push_back(it->first);
2278 SmallSet<Instruction*, 8> OpenIntervals;
2279 unsigned MaxUsage = 0;
2282 DEBUG(dbgs() << "LV(REG): Calculating max register usage:\n");
2283 for (unsigned int i = 0; i < Index; ++i) {
2284 Instruction *I = IdxToInstr[i];
2285 // Ignore instructions that are never used within the loop.
2286 if (!Ends.count(I)) continue;
2288 // Remove all of the instructions that end at this location.
2289 InstrList &List = TransposeEnds[i];
2290 for (unsigned int j=0, e = List.size(); j < e; ++j)
2291 OpenIntervals.erase(List[j]);
2293 // Count the number of live interals.
2294 MaxUsage = std::max(MaxUsage, OpenIntervals.size());
2296 DEBUG(dbgs() << "LV(REG): At #" << i << " Interval # " <<
2297 OpenIntervals.size() <<"\n");
2299 // Add the current instruction to the list of open intervals.
2300 OpenIntervals.insert(I);
2303 unsigned Invariant = LoopInvariants.size();
2304 DEBUG(dbgs() << "LV(REG): Found max usage: " << MaxUsage << " \n");
2305 DEBUG(dbgs() << "LV(REG): Found invariant usage: " << Invariant << " \n");
2306 DEBUG(dbgs() << "LV(REG): LoopSize: " << R.NumInstructions << " \n");
2308 R.LoopInvariantRegs = Invariant;
2309 R.MaxLocalUsers = MaxUsage;
2313 unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) {
2317 for (Loop::block_iterator bb = TheLoop->block_begin(),
2318 be = TheLoop->block_end(); bb != be; ++bb) {
2319 unsigned BlockCost = 0;
2320 BasicBlock *BB = *bb;
2322 // For each instruction in the old loop.
2323 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
2324 unsigned C = getInstructionCost(it, VF);
2326 DEBUG(dbgs() << "LV: Found an estimated cost of "<< C <<" for VF " <<
2327 VF << " For instruction: "<< *it << "\n");
2330 // We assume that if-converted blocks have a 50% chance of being executed.
2331 // When the code is scalar then some of the blocks are avoided due to CF.
2332 // When the code is vectorized we execute all code paths.
2333 if (Legal->blockNeedsPredication(*bb) && VF == 1)
2343 LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
2344 assert(TTI && "Invalid vector target transformation info");
2346 // If we know that this instruction will remain uniform, check the cost of
2347 // the scalar version.
2348 if (Legal->isUniformAfterVectorization(I))
2351 Type *RetTy = I->getType();
2352 Type *VectorTy = ToVectorTy(RetTy, VF);
2354 // TODO: We need to estimate the cost of intrinsic calls.
2355 switch (I->getOpcode()) {
2356 case Instruction::GetElementPtr:
2357 // We mark this instruction as zero-cost because scalar GEPs are usually
2358 // lowered to the intruction addressing mode. At the moment we don't
2359 // generate vector geps.
2361 case Instruction::Br: {
2362 return TTI->getCFInstrCost(I->getOpcode());
2364 case Instruction::PHI:
2365 //TODO: IF-converted IFs become selects.
2367 case Instruction::Add:
2368 case Instruction::FAdd:
2369 case Instruction::Sub:
2370 case Instruction::FSub:
2371 case Instruction::Mul:
2372 case Instruction::FMul:
2373 case Instruction::UDiv:
2374 case Instruction::SDiv:
2375 case Instruction::FDiv:
2376 case Instruction::URem:
2377 case Instruction::SRem:
2378 case Instruction::FRem:
2379 case Instruction::Shl:
2380 case Instruction::LShr:
2381 case Instruction::AShr:
2382 case Instruction::And:
2383 case Instruction::Or:
2384 case Instruction::Xor:
2385 return TTI->getArithmeticInstrCost(I->getOpcode(), VectorTy);
2386 case Instruction::Select: {
2387 SelectInst *SI = cast<SelectInst>(I);
2388 const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
2389 bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
2390 Type *CondTy = SI->getCondition()->getType();
2392 CondTy = VectorType::get(CondTy, VF);
2394 return TTI->getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy);
2396 case Instruction::ICmp:
2397 case Instruction::FCmp: {
2398 Type *ValTy = I->getOperand(0)->getType();
2399 VectorTy = ToVectorTy(ValTy, VF);
2400 return TTI->getCmpSelInstrCost(I->getOpcode(), VectorTy);
2402 case Instruction::Store: {
2403 StoreInst *SI = cast<StoreInst>(I);
2404 Type *ValTy = SI->getValueOperand()->getType();
2405 VectorTy = ToVectorTy(ValTy, VF);
2408 return TTI->getMemoryOpCost(I->getOpcode(), VectorTy,
2410 SI->getPointerAddressSpace());
2412 // Scalarized stores.
2413 int Stride = Legal->isConsecutivePtr(SI->getPointerOperand());
2414 bool Reverse = Stride < 0;
2418 // The cost of extracting from the value vector and pointer vector.
2419 Type *PtrTy = ToVectorTy(I->getOperand(0)->getType(), VF);
2420 for (unsigned i = 0; i < VF; ++i) {
2421 Cost += TTI->getVectorInstrCost(Instruction::ExtractElement,
2423 Cost += TTI->getVectorInstrCost(Instruction::ExtractElement,
2427 // The cost of the scalar stores.
2428 Cost += VF * TTI->getMemoryOpCost(I->getOpcode(),
2429 ValTy->getScalarType(),
2431 SI->getPointerAddressSpace());
2436 unsigned Cost = TTI->getMemoryOpCost(I->getOpcode(), VectorTy,
2438 SI->getPointerAddressSpace());
2440 Cost += TTI->getShuffleCost(TargetTransformInfo::Reverse,
2444 case Instruction::Load: {
2445 LoadInst *LI = cast<LoadInst>(I);
2448 return TTI->getMemoryOpCost(I->getOpcode(), VectorTy,
2450 LI->getPointerAddressSpace());
2452 // Scalarized loads.
2453 int Stride = Legal->isConsecutivePtr(LI->getPointerOperand());
2454 bool Reverse = Stride < 0;
2457 Type *PtrTy = ToVectorTy(I->getOperand(0)->getType(), VF);
2459 // The cost of extracting from the pointer vector.
2460 for (unsigned i = 0; i < VF; ++i)
2461 Cost += TTI->getVectorInstrCost(Instruction::ExtractElement,
2464 // The cost of inserting data to the result vector.
2465 for (unsigned i = 0; i < VF; ++i)
2466 Cost += TTI->getVectorInstrCost(Instruction::InsertElement,
2469 // The cost of the scalar stores.
2470 Cost += VF * TTI->getMemoryOpCost(I->getOpcode(),
2471 RetTy->getScalarType(),
2473 LI->getPointerAddressSpace());
2478 unsigned Cost = TTI->getMemoryOpCost(I->getOpcode(), VectorTy,
2480 LI->getPointerAddressSpace());
2482 Cost += TTI->getShuffleCost(TargetTransformInfo::Reverse,
2486 case Instruction::ZExt:
2487 case Instruction::SExt:
2488 case Instruction::FPToUI:
2489 case Instruction::FPToSI:
2490 case Instruction::FPExt:
2491 case Instruction::PtrToInt:
2492 case Instruction::IntToPtr:
2493 case Instruction::SIToFP:
2494 case Instruction::UIToFP:
2495 case Instruction::Trunc:
2496 case Instruction::FPTrunc:
2497 case Instruction::BitCast: {
2498 // We optimize the truncation of induction variable.
2499 // The cost of these is the same as the scalar operation.
2500 if (I->getOpcode() == Instruction::Trunc &&
2501 Legal->isInductionVariable(I->getOperand(0)))
2502 return TTI->getCastInstrCost(I->getOpcode(), I->getType(),
2503 I->getOperand(0)->getType());
2505 Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF);
2506 return TTI->getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy);
2508 case Instruction::Call: {
2509 assert(isTriviallyVectorizableIntrinsic(I));
2510 IntrinsicInst *II = cast<IntrinsicInst>(I);
2511 Type *RetTy = ToVectorTy(II->getType(), VF);
2512 SmallVector<Type*, 4> Tys;
2513 for (unsigned i = 0, ie = II->getNumArgOperands(); i != ie; ++i)
2514 Tys.push_back(ToVectorTy(II->getArgOperand(i)->getType(), VF));
2515 return TTI->getIntrinsicInstrCost(II->getIntrinsicID(), RetTy, Tys);
2518 // We are scalarizing the instruction. Return the cost of the scalar
2519 // instruction, plus the cost of insert and extract into vector
2520 // elements, times the vector width.
2523 if (!RetTy->isVoidTy() && VF != 1) {
2524 unsigned InsCost = TTI->getVectorInstrCost(Instruction::InsertElement,
2526 unsigned ExtCost = TTI->getVectorInstrCost(Instruction::ExtractElement,
2529 // The cost of inserting the results plus extracting each one of the
2531 Cost += VF * (InsCost + ExtCost * I->getNumOperands());
2534 // The cost of executing VF copies of the scalar instruction. This opcode
2535 // is unknown. Assume that it is the same as 'mul'.
2536 Cost += VF * TTI->getArithmeticInstrCost(Instruction::Mul, VectorTy);
2542 Type* LoopVectorizationCostModel::ToVectorTy(Type *Scalar, unsigned VF) {
2543 if (Scalar->isVoidTy() || VF == 1)
2545 return VectorType::get(Scalar, VF);
2548 char LoopVectorize::ID = 0;
2549 static const char lv_name[] = "Loop Vectorization";
2550 INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false)
2551 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
2552 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
2553 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
2554 INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
2557 Pass *createLoopVectorizePass() {
2558 return new LoopVectorize();