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Diffstat (limited to 'lib/Target/PowerPC/PPCLoopPreIncPrep.cpp')
| -rw-r--r-- | lib/Target/PowerPC/PPCLoopPreIncPrep.cpp | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp b/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp new file mode 100644 index 0000000..df65227 --- /dev/null +++ b/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp @@ -0,0 +1,382 @@ +//===------ PPCLoopPreIncPrep.cpp - Loop Pre-Inc. AM Prep. Pass -----------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements a pass to prepare loops for pre-increment addressing +// modes. Additional PHIs are created for loop induction variables used by +// load/store instructions so that the pre-increment forms can be used. +// Generically, this means transforming loops like this: +// for (int i = 0; i < n; ++i) +// array[i] = c; +// to look like this: +// T *p = array[-1]; +// for (int i = 0; i < n; ++i) +// *++p = c; +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "ppc-loop-preinc-prep" +#include "PPC.h" +#include "PPCTargetMachine.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/CodeMetrics.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/ScalarEvolution.h" +#include "llvm/Analysis/ScalarEvolutionExpander.h" +#include "llvm/Analysis/ScalarEvolutionExpressions.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Transforms/Utils/LoopUtils.h" +#include "llvm/Transforms/Utils/ValueMapper.h" +using namespace llvm; + +// By default, we limit this to creating 16 PHIs (which is a little over half +// of the allocatable register set). +static cl::opt<unsigned> MaxVars("ppc-preinc-prep-max-vars", + cl::Hidden, cl::init(16), + cl::desc("Potential PHI threshold for PPC preinc loop prep")); + +namespace llvm { + void initializePPCLoopPreIncPrepPass(PassRegistry&); +} + +namespace { + + class PPCLoopPreIncPrep : public FunctionPass { + public: + static char ID; // Pass ID, replacement for typeid + PPCLoopPreIncPrep() : FunctionPass(ID), TM(nullptr) { + initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry()); + } + PPCLoopPreIncPrep(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) { + initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry()); + } + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addPreserved<DominatorTreeWrapperPass>(); + AU.addRequired<LoopInfoWrapperPass>(); + AU.addPreserved<LoopInfoWrapperPass>(); + AU.addRequired<ScalarEvolution>(); + } + + bool runOnFunction(Function &F) override; + + bool runOnLoop(Loop *L); + void simplifyLoopLatch(Loop *L); + bool rotateLoop(Loop *L); + + private: + PPCTargetMachine *TM; + LoopInfo *LI; + ScalarEvolution *SE; + const DataLayout *DL; + }; +} + +char PPCLoopPreIncPrep::ID = 0; +static const char *name = "Prepare loop for pre-inc. addressing modes"; +INITIALIZE_PASS_BEGIN(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false) +INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) +INITIALIZE_PASS_END(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false) + +FunctionPass *llvm::createPPCLoopPreIncPrepPass(PPCTargetMachine &TM) { + return new PPCLoopPreIncPrep(TM); +} + +namespace { + struct SCEVLess : std::binary_function<const SCEV *, const SCEV *, bool> + { + SCEVLess(ScalarEvolution *SE) : SE(SE) {} + + bool operator() (const SCEV *X, const SCEV *Y) const { + const SCEV *Diff = SE->getMinusSCEV(X, Y); + return cast<SCEVConstant>(Diff)->getValue()->getSExtValue() < 0; + } + + protected: + ScalarEvolution *SE; + }; +} + +static bool IsPtrInBounds(Value *BasePtr) { + Value *StrippedBasePtr = BasePtr; + while (BitCastInst *BC = dyn_cast<BitCastInst>(StrippedBasePtr)) + StrippedBasePtr = BC->getOperand(0); + if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(StrippedBasePtr)) + return GEP->isInBounds(); + + return false; +} + +static Value *GetPointerOperand(Value *MemI) { + if (LoadInst *LMemI = dyn_cast<LoadInst>(MemI)) { + return LMemI->getPointerOperand(); + } else if (StoreInst *SMemI = dyn_cast<StoreInst>(MemI)) { + return SMemI->getPointerOperand(); + } else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(MemI)) { + if (IMemI->getIntrinsicID() == Intrinsic::prefetch) + return IMemI->getArgOperand(0); + } + + return 0; +} + +bool PPCLoopPreIncPrep::runOnFunction(Function &F) { + LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); + SE = &getAnalysis<ScalarEvolution>(); + + DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); + DL = DLP ? &DLP->getDataLayout() : 0; + + bool MadeChange = false; + + for (LoopInfo::iterator I = LI->begin(), E = LI->end(); + I != E; ++I) { + Loop *L = *I; + MadeChange |= runOnLoop(L); + } + + return MadeChange; +} + +bool PPCLoopPreIncPrep::runOnLoop(Loop *L) { + bool MadeChange = false; + + if (!DL) + return MadeChange; + + // Only prep. the inner-most loop + if (!L->empty()) + return MadeChange; + + BasicBlock *Header = L->getHeader(); + + const PPCSubtarget *ST = + TM ? TM->getSubtargetImpl(*Header->getParent()) : nullptr; + + unsigned HeaderLoopPredCount = 0; + for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); + PI != PE; ++PI) { + ++HeaderLoopPredCount; + } + + // Collect buckets of comparable addresses used by loads and stores. + typedef std::multimap<const SCEV *, Instruction *, SCEVLess> Bucket; + SmallVector<Bucket, 16> Buckets; + for (Loop::block_iterator I = L->block_begin(), IE = L->block_end(); + I != IE; ++I) { + for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end(); + J != JE; ++J) { + Value *PtrValue; + Instruction *MemI; + + if (LoadInst *LMemI = dyn_cast<LoadInst>(J)) { + MemI = LMemI; + PtrValue = LMemI->getPointerOperand(); + } else if (StoreInst *SMemI = dyn_cast<StoreInst>(J)) { + MemI = SMemI; + PtrValue = SMemI->getPointerOperand(); + } else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(J)) { + if (IMemI->getIntrinsicID() == Intrinsic::prefetch) { + MemI = IMemI; + PtrValue = IMemI->getArgOperand(0); + } else continue; + } else continue; + + unsigned PtrAddrSpace = PtrValue->getType()->getPointerAddressSpace(); + if (PtrAddrSpace) + continue; + + // There are no update forms for Altivec vector load/stores. + if (ST && ST->hasAltivec() && + PtrValue->getType()->getPointerElementType()->isVectorTy()) + continue; + + if (L->isLoopInvariant(PtrValue)) + continue; + + const SCEV *LSCEV = SE->getSCEV(PtrValue); + if (!isa<SCEVAddRecExpr>(LSCEV)) + continue; + + bool FoundBucket = false; + for (unsigned i = 0, e = Buckets.size(); i != e; ++i) + for (Bucket::iterator K = Buckets[i].begin(), KE = Buckets[i].end(); + K != KE; ++K) { + const SCEV *Diff = SE->getMinusSCEV(K->first, LSCEV); + if (isa<SCEVConstant>(Diff)) { + Buckets[i].insert(std::make_pair(LSCEV, MemI)); + FoundBucket = true; + break; + } + } + + if (!FoundBucket) { + Buckets.push_back(Bucket(SCEVLess(SE))); + Buckets[Buckets.size()-1].insert(std::make_pair(LSCEV, MemI)); + } + } + } + + if (Buckets.empty() || Buckets.size() > MaxVars) + return MadeChange; + + BasicBlock *LoopPredecessor = L->getLoopPredecessor(); + // If there is no loop predecessor, or the loop predecessor's terminator + // returns a value (which might contribute to determining the loop's + // iteration space), insert a new preheader for the loop. + if (!LoopPredecessor || + !LoopPredecessor->getTerminator()->getType()->isVoidTy()) + LoopPredecessor = InsertPreheaderForLoop(L, this); + if (!LoopPredecessor) + return MadeChange; + + SmallSet<BasicBlock *, 16> BBChanged; + for (unsigned i = 0, e = Buckets.size(); i != e; ++i) { + // The base address of each bucket is transformed into a phi and the others + // are rewritten as offsets of that variable. + + const SCEVAddRecExpr *BasePtrSCEV = + cast<SCEVAddRecExpr>(Buckets[i].begin()->first); + if (!BasePtrSCEV->isAffine()) + continue; + + Instruction *MemI = Buckets[i].begin()->second; + Value *BasePtr = GetPointerOperand(MemI); + assert(BasePtr && "No pointer operand"); + + Type *I8PtrTy = Type::getInt8PtrTy(MemI->getParent()->getContext(), + BasePtr->getType()->getPointerAddressSpace()); + + const SCEV *BasePtrStartSCEV = BasePtrSCEV->getStart(); + if (!SE->isLoopInvariant(BasePtrStartSCEV, L)) + continue; + + const SCEVConstant *BasePtrIncSCEV = + dyn_cast<SCEVConstant>(BasePtrSCEV->getStepRecurrence(*SE)); + if (!BasePtrIncSCEV) + continue; + BasePtrStartSCEV = SE->getMinusSCEV(BasePtrStartSCEV, BasePtrIncSCEV); + if (!isSafeToExpand(BasePtrStartSCEV, *SE)) + continue; + + PHINode *NewPHI = PHINode::Create(I8PtrTy, HeaderLoopPredCount, + MemI->hasName() ? MemI->getName() + ".phi" : "", + Header->getFirstNonPHI()); + + SCEVExpander SCEVE(*SE, "pistart"); + Value *BasePtrStart = SCEVE.expandCodeFor(BasePtrStartSCEV, I8PtrTy, + LoopPredecessor->getTerminator()); + + // Note that LoopPredecessor might occur in the predecessor list multiple + // times, and we need to add it the right number of times. + for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); + PI != PE; ++PI) { + if (*PI != LoopPredecessor) + continue; + + NewPHI->addIncoming(BasePtrStart, LoopPredecessor); + } + + Instruction *InsPoint = Header->getFirstInsertionPt(); + GetElementPtrInst *PtrInc = + GetElementPtrInst::Create(NewPHI, BasePtrIncSCEV->getValue(), + MemI->hasName() ? MemI->getName() + ".inc" : "", InsPoint); + PtrInc->setIsInBounds(IsPtrInBounds(BasePtr)); + for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header); + PI != PE; ++PI) { + if (*PI == LoopPredecessor) + continue; + + NewPHI->addIncoming(PtrInc, *PI); + } + + Instruction *NewBasePtr; + if (PtrInc->getType() != BasePtr->getType()) + NewBasePtr = new BitCastInst(PtrInc, BasePtr->getType(), + PtrInc->hasName() ? PtrInc->getName() + ".cast" : "", InsPoint); + else + NewBasePtr = PtrInc; + + if (Instruction *IDel = dyn_cast<Instruction>(BasePtr)) + BBChanged.insert(IDel->getParent()); + BasePtr->replaceAllUsesWith(NewBasePtr); + RecursivelyDeleteTriviallyDeadInstructions(BasePtr); + + Value *LastNewPtr = NewBasePtr; + for (Bucket::iterator I = std::next(Buckets[i].begin()), + IE = Buckets[i].end(); I != IE; ++I) { + Value *Ptr = GetPointerOperand(I->second); + assert(Ptr && "No pointer operand"); + if (Ptr == LastNewPtr) + continue; + + Instruction *RealNewPtr; + const SCEVConstant *Diff = + cast<SCEVConstant>(SE->getMinusSCEV(I->first, BasePtrSCEV)); + if (Diff->isZero()) { + RealNewPtr = NewBasePtr; + } else { + Instruction *PtrIP = dyn_cast<Instruction>(Ptr); + if (PtrIP && isa<Instruction>(NewBasePtr) && + cast<Instruction>(NewBasePtr)->getParent() == PtrIP->getParent()) + PtrIP = 0; + else if (isa<PHINode>(PtrIP)) + PtrIP = PtrIP->getParent()->getFirstInsertionPt(); + else if (!PtrIP) + PtrIP = I->second; + + GetElementPtrInst *NewPtr = + GetElementPtrInst::Create(PtrInc, Diff->getValue(), + I->second->hasName() ? I->second->getName() + ".off" : "", PtrIP); + if (!PtrIP) + NewPtr->insertAfter(cast<Instruction>(PtrInc)); + NewPtr->setIsInBounds(IsPtrInBounds(Ptr)); + RealNewPtr = NewPtr; + } + + if (Instruction *IDel = dyn_cast<Instruction>(Ptr)) + BBChanged.insert(IDel->getParent()); + + Instruction *ReplNewPtr; + if (Ptr->getType() != RealNewPtr->getType()) { + ReplNewPtr = new BitCastInst(RealNewPtr, Ptr->getType(), + Ptr->hasName() ? Ptr->getName() + ".cast" : ""); + ReplNewPtr->insertAfter(RealNewPtr); + } else + ReplNewPtr = RealNewPtr; + + Ptr->replaceAllUsesWith(ReplNewPtr); + RecursivelyDeleteTriviallyDeadInstructions(Ptr); + + LastNewPtr = RealNewPtr; + } + + MadeChange = true; + } + + for (Loop::block_iterator I = L->block_begin(), IE = L->block_end(); + I != IE; ++I) { + if (BBChanged.count(*I)) + DeleteDeadPHIs(*I); + } + + return MadeChange; +} + |