forked from OSchip/llvm-project
378 lines
12 KiB
C++
378 lines
12 KiB
C++
//===------ PPCLoopPreIncPrep.cpp - Loop Pre-Inc. AM Prep. Pass -----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a pass to prepare loops for pre-increment addressing
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// modes. Additional PHIs are created for loop induction variables used by
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// load/store instructions so that the pre-increment forms can be used.
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// Generically, this means transforming loops like this:
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// for (int i = 0; i < n; ++i)
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// array[i] = c;
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// to look like this:
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// T *p = array[-1];
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// for (int i = 0; i < n; ++i)
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// *++p = c;
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "ppc-loop-preinc-prep"
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#include "PPC.h"
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#include "PPCTargetMachine.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/CodeMetrics.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/LoopUtils.h"
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#include "llvm/Transforms/Utils/ValueMapper.h"
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using namespace llvm;
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// By default, we limit this to creating 16 PHIs (which is a little over half
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// of the allocatable register set).
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static cl::opt<unsigned> MaxVars("ppc-preinc-prep-max-vars",
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cl::Hidden, cl::init(16),
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cl::desc("Potential PHI threshold for PPC preinc loop prep"));
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namespace llvm {
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void initializePPCLoopPreIncPrepPass(PassRegistry&);
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}
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namespace {
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class PPCLoopPreIncPrep : public FunctionPass {
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public:
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static char ID; // Pass ID, replacement for typeid
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PPCLoopPreIncPrep() : FunctionPass(ID), TM(nullptr) {
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initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry());
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}
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PPCLoopPreIncPrep(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) {
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initializePPCLoopPreIncPrepPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addPreserved<DominatorTreeWrapperPass>();
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AU.addRequired<LoopInfoWrapperPass>();
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AU.addPreserved<LoopInfoWrapperPass>();
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AU.addRequired<ScalarEvolution>();
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}
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bool runOnFunction(Function &F) override;
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bool runOnLoop(Loop *L);
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void simplifyLoopLatch(Loop *L);
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bool rotateLoop(Loop *L);
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private:
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PPCTargetMachine *TM;
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LoopInfo *LI;
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ScalarEvolution *SE;
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};
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}
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char PPCLoopPreIncPrep::ID = 0;
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static const char *name = "Prepare loop for pre-inc. addressing modes";
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INITIALIZE_PASS_BEGIN(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false)
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INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
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INITIALIZE_PASS_END(PPCLoopPreIncPrep, DEBUG_TYPE, name, false, false)
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FunctionPass *llvm::createPPCLoopPreIncPrepPass(PPCTargetMachine &TM) {
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return new PPCLoopPreIncPrep(TM);
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}
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namespace {
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struct SCEVLess : std::binary_function<const SCEV *, const SCEV *, bool>
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{
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SCEVLess(ScalarEvolution *SE) : SE(SE) {}
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bool operator() (const SCEV *X, const SCEV *Y) const {
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const SCEV *Diff = SE->getMinusSCEV(X, Y);
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return cast<SCEVConstant>(Diff)->getValue()->getSExtValue() < 0;
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}
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protected:
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ScalarEvolution *SE;
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};
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}
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static bool IsPtrInBounds(Value *BasePtr) {
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Value *StrippedBasePtr = BasePtr;
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while (BitCastInst *BC = dyn_cast<BitCastInst>(StrippedBasePtr))
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StrippedBasePtr = BC->getOperand(0);
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if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(StrippedBasePtr))
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return GEP->isInBounds();
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return false;
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}
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static Value *GetPointerOperand(Value *MemI) {
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if (LoadInst *LMemI = dyn_cast<LoadInst>(MemI)) {
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return LMemI->getPointerOperand();
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} else if (StoreInst *SMemI = dyn_cast<StoreInst>(MemI)) {
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return SMemI->getPointerOperand();
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} else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(MemI)) {
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if (IMemI->getIntrinsicID() == Intrinsic::prefetch)
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return IMemI->getArgOperand(0);
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}
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return 0;
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}
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bool PPCLoopPreIncPrep::runOnFunction(Function &F) {
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LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
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SE = &getAnalysis<ScalarEvolution>();
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bool MadeChange = false;
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for (LoopInfo::iterator I = LI->begin(), E = LI->end();
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I != E; ++I) {
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Loop *L = *I;
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MadeChange |= runOnLoop(L);
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}
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return MadeChange;
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}
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bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
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bool MadeChange = false;
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// Only prep. the inner-most loop
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if (!L->empty())
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return MadeChange;
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BasicBlock *Header = L->getHeader();
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const PPCSubtarget *ST =
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TM ? TM->getSubtargetImpl(*Header->getParent()) : nullptr;
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unsigned HeaderLoopPredCount = 0;
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for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
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PI != PE; ++PI) {
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++HeaderLoopPredCount;
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}
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// Collect buckets of comparable addresses used by loads and stores.
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typedef std::multimap<const SCEV *, Instruction *, SCEVLess> Bucket;
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SmallVector<Bucket, 16> Buckets;
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for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
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I != IE; ++I) {
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for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end();
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J != JE; ++J) {
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Value *PtrValue;
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Instruction *MemI;
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if (LoadInst *LMemI = dyn_cast<LoadInst>(J)) {
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MemI = LMemI;
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PtrValue = LMemI->getPointerOperand();
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} else if (StoreInst *SMemI = dyn_cast<StoreInst>(J)) {
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MemI = SMemI;
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PtrValue = SMemI->getPointerOperand();
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} else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(J)) {
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if (IMemI->getIntrinsicID() == Intrinsic::prefetch) {
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MemI = IMemI;
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PtrValue = IMemI->getArgOperand(0);
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} else continue;
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} else continue;
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unsigned PtrAddrSpace = PtrValue->getType()->getPointerAddressSpace();
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if (PtrAddrSpace)
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continue;
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// There are no update forms for Altivec vector load/stores.
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if (ST && ST->hasAltivec() &&
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PtrValue->getType()->getPointerElementType()->isVectorTy())
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continue;
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if (L->isLoopInvariant(PtrValue))
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continue;
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const SCEV *LSCEV = SE->getSCEV(PtrValue);
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if (!isa<SCEVAddRecExpr>(LSCEV))
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continue;
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bool FoundBucket = false;
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for (unsigned i = 0, e = Buckets.size(); i != e; ++i)
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for (Bucket::iterator K = Buckets[i].begin(), KE = Buckets[i].end();
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K != KE; ++K) {
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const SCEV *Diff = SE->getMinusSCEV(K->first, LSCEV);
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if (isa<SCEVConstant>(Diff)) {
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Buckets[i].insert(std::make_pair(LSCEV, MemI));
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FoundBucket = true;
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break;
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}
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}
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if (!FoundBucket) {
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Buckets.push_back(Bucket(SCEVLess(SE)));
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Buckets[Buckets.size()-1].insert(std::make_pair(LSCEV, MemI));
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}
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}
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}
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if (Buckets.empty() || Buckets.size() > MaxVars)
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return MadeChange;
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BasicBlock *LoopPredecessor = L->getLoopPredecessor();
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// If there is no loop predecessor, or the loop predecessor's terminator
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// returns a value (which might contribute to determining the loop's
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// iteration space), insert a new preheader for the loop.
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if (!LoopPredecessor ||
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!LoopPredecessor->getTerminator()->getType()->isVoidTy())
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LoopPredecessor = InsertPreheaderForLoop(L, this);
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if (!LoopPredecessor)
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return MadeChange;
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SmallSet<BasicBlock *, 16> BBChanged;
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for (unsigned i = 0, e = Buckets.size(); i != e; ++i) {
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// The base address of each bucket is transformed into a phi and the others
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// are rewritten as offsets of that variable.
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const SCEVAddRecExpr *BasePtrSCEV =
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cast<SCEVAddRecExpr>(Buckets[i].begin()->first);
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if (!BasePtrSCEV->isAffine())
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continue;
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Instruction *MemI = Buckets[i].begin()->second;
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Value *BasePtr = GetPointerOperand(MemI);
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assert(BasePtr && "No pointer operand");
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Type *I8Ty = Type::getInt8Ty(MemI->getParent()->getContext());
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Type *I8PtrTy = Type::getInt8PtrTy(MemI->getParent()->getContext(),
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BasePtr->getType()->getPointerAddressSpace());
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const SCEV *BasePtrStartSCEV = BasePtrSCEV->getStart();
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if (!SE->isLoopInvariant(BasePtrStartSCEV, L))
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continue;
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const SCEVConstant *BasePtrIncSCEV =
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dyn_cast<SCEVConstant>(BasePtrSCEV->getStepRecurrence(*SE));
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if (!BasePtrIncSCEV)
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continue;
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BasePtrStartSCEV = SE->getMinusSCEV(BasePtrStartSCEV, BasePtrIncSCEV);
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if (!isSafeToExpand(BasePtrStartSCEV, *SE))
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continue;
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PHINode *NewPHI = PHINode::Create(I8PtrTy, HeaderLoopPredCount,
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MemI->hasName() ? MemI->getName() + ".phi" : "",
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Header->getFirstNonPHI());
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SCEVExpander SCEVE(*SE, Header->getModule()->getDataLayout(), "pistart");
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Value *BasePtrStart = SCEVE.expandCodeFor(BasePtrStartSCEV, I8PtrTy,
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LoopPredecessor->getTerminator());
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// Note that LoopPredecessor might occur in the predecessor list multiple
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// times, and we need to add it the right number of times.
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for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
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PI != PE; ++PI) {
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if (*PI != LoopPredecessor)
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continue;
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NewPHI->addIncoming(BasePtrStart, LoopPredecessor);
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}
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Instruction *InsPoint = Header->getFirstInsertionPt();
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GetElementPtrInst *PtrInc = GetElementPtrInst::Create(
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I8Ty, NewPHI, BasePtrIncSCEV->getValue(),
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MemI->hasName() ? MemI->getName() + ".inc" : "", InsPoint);
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PtrInc->setIsInBounds(IsPtrInBounds(BasePtr));
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for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
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PI != PE; ++PI) {
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if (*PI == LoopPredecessor)
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continue;
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NewPHI->addIncoming(PtrInc, *PI);
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}
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Instruction *NewBasePtr;
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if (PtrInc->getType() != BasePtr->getType())
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NewBasePtr = new BitCastInst(PtrInc, BasePtr->getType(),
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PtrInc->hasName() ? PtrInc->getName() + ".cast" : "", InsPoint);
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else
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NewBasePtr = PtrInc;
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if (Instruction *IDel = dyn_cast<Instruction>(BasePtr))
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BBChanged.insert(IDel->getParent());
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BasePtr->replaceAllUsesWith(NewBasePtr);
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RecursivelyDeleteTriviallyDeadInstructions(BasePtr);
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Value *LastNewPtr = NewBasePtr;
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for (Bucket::iterator I = std::next(Buckets[i].begin()),
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IE = Buckets[i].end(); I != IE; ++I) {
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Value *Ptr = GetPointerOperand(I->second);
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assert(Ptr && "No pointer operand");
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if (Ptr == LastNewPtr)
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continue;
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Instruction *RealNewPtr;
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const SCEVConstant *Diff =
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cast<SCEVConstant>(SE->getMinusSCEV(I->first, BasePtrSCEV));
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if (Diff->isZero()) {
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RealNewPtr = NewBasePtr;
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} else {
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Instruction *PtrIP = dyn_cast<Instruction>(Ptr);
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if (PtrIP && isa<Instruction>(NewBasePtr) &&
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cast<Instruction>(NewBasePtr)->getParent() == PtrIP->getParent())
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PtrIP = 0;
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else if (isa<PHINode>(PtrIP))
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PtrIP = PtrIP->getParent()->getFirstInsertionPt();
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else if (!PtrIP)
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PtrIP = I->second;
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GetElementPtrInst *NewPtr = GetElementPtrInst::Create(
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I8Ty, PtrInc, Diff->getValue(),
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I->second->hasName() ? I->second->getName() + ".off" : "", PtrIP);
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if (!PtrIP)
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NewPtr->insertAfter(cast<Instruction>(PtrInc));
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NewPtr->setIsInBounds(IsPtrInBounds(Ptr));
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RealNewPtr = NewPtr;
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}
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if (Instruction *IDel = dyn_cast<Instruction>(Ptr))
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BBChanged.insert(IDel->getParent());
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Instruction *ReplNewPtr;
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if (Ptr->getType() != RealNewPtr->getType()) {
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ReplNewPtr = new BitCastInst(RealNewPtr, Ptr->getType(),
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Ptr->hasName() ? Ptr->getName() + ".cast" : "");
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ReplNewPtr->insertAfter(RealNewPtr);
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} else
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ReplNewPtr = RealNewPtr;
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Ptr->replaceAllUsesWith(ReplNewPtr);
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RecursivelyDeleteTriviallyDeadInstructions(Ptr);
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LastNewPtr = RealNewPtr;
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}
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MadeChange = true;
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}
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for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
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I != IE; ++I) {
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if (BBChanged.count(*I))
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DeleteDeadPHIs(*I);
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}
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return MadeChange;
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}
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