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https://github.com/c64scene-ar/llvm-6502.git
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529919ff31
Summary: Now that the DataLayout is a mandatory part of the module, let's start cleaning the codebase. This patch is a first attempt at doing that. This patch is not exactly NFC as for instance some places were passing a nullptr instead of the DataLayout, possibly just because there was a default value on the DataLayout argument to many functions in the API. Even though it is not purely NFC, there is no change in the validation. I turned as many pointer to DataLayout to references, this helped figuring out all the places where a nullptr could come up. I had initially a local version of this patch broken into over 30 independant, commits but some later commit were cleaning the API and touching part of the code modified in the previous commits, so it seemed cleaner without the intermediate state. Test Plan: Reviewers: echristo Subscribers: llvm-commits From: Mehdi Amini <mehdi.amini@apple.com> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231740 91177308-0d34-0410-b5e6-96231b3b80d8
232 lines
7.9 KiB
C++
232 lines
7.9 KiB
C++
//===-------- PPCLoopDataPrefetch.cpp - Loop Data Prefetching 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 Loop Data Prefetching Pass.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "ppc-loop-data-prefetch"
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#include "PPC.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/AssumptionCache.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/TargetTransformInfo.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/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.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<bool>
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PrefetchWrites("ppc-loop-prefetch-writes", cl::Hidden, cl::init(false),
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cl::desc("Prefetch write addresses"));
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// This seems like a reasonable default for the BG/Q (this pass is enabled, by
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// default, only on the BG/Q).
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static cl::opt<unsigned>
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PrefDist("ppc-loop-prefetch-distance", cl::Hidden, cl::init(300),
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cl::desc("The loop prefetch distance"));
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static cl::opt<unsigned>
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CacheLineSize("ppc-loop-prefetch-cache-line", cl::Hidden, cl::init(64),
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cl::desc("The loop prefetch cache line size"));
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namespace llvm {
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void initializePPCLoopDataPrefetchPass(PassRegistry&);
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}
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namespace {
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class PPCLoopDataPrefetch : public FunctionPass {
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public:
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static char ID; // Pass ID, replacement for typeid
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PPCLoopDataPrefetch() : FunctionPass(ID) {
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initializePPCLoopDataPrefetchPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addRequired<AssumptionCacheTracker>();
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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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// FIXME: For some reason, preserving SE here breaks LSR (even if
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// this pass changes nothing).
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// AU.addPreserved<ScalarEvolution>();
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AU.addRequired<TargetTransformInfoWrapperPass>();
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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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private:
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AssumptionCache *AC;
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LoopInfo *LI;
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ScalarEvolution *SE;
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const TargetTransformInfo *TTI;
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const DataLayout *DL;
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};
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}
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char PPCLoopDataPrefetch::ID = 0;
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INITIALIZE_PASS_BEGIN(PPCLoopDataPrefetch, "ppc-loop-data-prefetch",
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"PPC Loop Data Prefetch", false, false)
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INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
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INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
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INITIALIZE_PASS_END(PPCLoopDataPrefetch, "ppc-loop-data-prefetch",
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"PPC Loop Data Prefetch", false, false)
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FunctionPass *llvm::createPPCLoopDataPrefetchPass() { return new PPCLoopDataPrefetch(); }
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bool PPCLoopDataPrefetch::runOnFunction(Function &F) {
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LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
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SE = &getAnalysis<ScalarEvolution>();
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DL = &F.getParent()->getDataLayout();
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AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
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TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
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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 PPCLoopDataPrefetch::runOnLoop(Loop *L) {
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bool MadeChange = false;
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// Only prefetch in the inner-most loop
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if (!L->empty())
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return MadeChange;
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SmallPtrSet<const Value *, 32> EphValues;
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CodeMetrics::collectEphemeralValues(L, AC, EphValues);
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// Calculate the number of iterations ahead to prefetch
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CodeMetrics Metrics;
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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 the loop already has prefetches, then assume that the user knows
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// what he or she is doing and don't add any more.
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for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end();
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J != JE; ++J)
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if (CallInst *CI = dyn_cast<CallInst>(J))
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if (Function *F = CI->getCalledFunction())
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if (F->getIntrinsicID() == Intrinsic::prefetch)
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return MadeChange;
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Metrics.analyzeBasicBlock(*I, *TTI, EphValues);
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}
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unsigned LoopSize = Metrics.NumInsts;
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if (!LoopSize)
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LoopSize = 1;
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unsigned ItersAhead = PrefDist/LoopSize;
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if (!ItersAhead)
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ItersAhead = 1;
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SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>, 16> PrefLoads;
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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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if (!PrefetchWrites) continue;
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MemI = SMemI;
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PtrValue = SMemI->getPointerOperand();
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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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if (L->isLoopInvariant(PtrValue))
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continue;
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const SCEV *LSCEV = SE->getSCEV(PtrValue);
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const SCEVAddRecExpr *LSCEVAddRec = dyn_cast<SCEVAddRecExpr>(LSCEV);
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if (!LSCEVAddRec)
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continue;
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// We don't want to double prefetch individual cache lines. If this load
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// is known to be within one cache line of some other load that has
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// already been prefetched, then don't prefetch this one as well.
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bool DupPref = false;
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for (SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>,
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16>::iterator K = PrefLoads.begin(), KE = PrefLoads.end();
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K != KE; ++K) {
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const SCEV *PtrDiff = SE->getMinusSCEV(LSCEVAddRec, K->second);
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if (const SCEVConstant *ConstPtrDiff =
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dyn_cast<SCEVConstant>(PtrDiff)) {
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int64_t PD = std::abs(ConstPtrDiff->getValue()->getSExtValue());
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if (PD < (int64_t) CacheLineSize) {
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DupPref = true;
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break;
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}
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}
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}
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if (DupPref)
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continue;
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const SCEV *NextLSCEV = SE->getAddExpr(LSCEVAddRec, SE->getMulExpr(
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SE->getConstant(LSCEVAddRec->getType(), ItersAhead),
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LSCEVAddRec->getStepRecurrence(*SE)));
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if (!isSafeToExpand(NextLSCEV, *SE))
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continue;
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PrefLoads.push_back(std::make_pair(MemI, LSCEVAddRec));
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Type *I8Ptr = Type::getInt8PtrTy((*I)->getContext(), PtrAddrSpace);
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SCEVExpander SCEVE(*SE, J->getModule()->getDataLayout(), "prefaddr");
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Value *PrefPtrValue = SCEVE.expandCodeFor(NextLSCEV, I8Ptr, MemI);
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IRBuilder<> Builder(MemI);
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Module *M = (*I)->getParent()->getParent();
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Type *I32 = Type::getInt32Ty((*I)->getContext());
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Value *PrefetchFunc = Intrinsic::getDeclaration(M, Intrinsic::prefetch);
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Builder.CreateCall4(PrefetchFunc, PrefPtrValue,
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ConstantInt::get(I32, MemI->mayReadFromMemory() ? 0 : 1),
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ConstantInt::get(I32, 3), ConstantInt::get(I32, 1));
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MadeChange = true;
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}
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}
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return MadeChange;
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}
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