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This will allow it to be shared with the new Loop Distribution pass. getFirstInst is currently duplicated across LoopVectorize.cpp and LoopAccessAnalysis.cpp. This is a short-term work-around until we figure out a better solution. NFC. (The code moved is adjusted a bit for the name of the Loop member and that PtrRtCheck is now a reference rather than a pointer.) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228418 91177308-0d34-0410-b5e6-96231b3b80d8
1191 lines
44 KiB
C++
1191 lines
44 KiB
C++
//===- LoopAccessAnalysis.cpp - Loop Access Analysis Implementation --------==//
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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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// The implementation for the loop memory dependence that was originally
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// developed for the loop vectorizer.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LoopAccessAnalysis.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/DiagnosticInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Transforms/Utils/VectorUtils.h"
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using namespace llvm;
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#define DEBUG_TYPE "loop-vectorize"
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void VectorizationReport::emitAnalysis(VectorizationReport &Message,
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const Function *TheFunction,
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const Loop *TheLoop) {
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DebugLoc DL = TheLoop->getStartLoc();
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if (Instruction *I = Message.getInstr())
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DL = I->getDebugLoc();
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emitOptimizationRemarkAnalysis(TheFunction->getContext(), DEBUG_TYPE,
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*TheFunction, DL, Message.str());
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}
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Value *llvm::stripIntegerCast(Value *V) {
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if (CastInst *CI = dyn_cast<CastInst>(V))
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if (CI->getOperand(0)->getType()->isIntegerTy())
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return CI->getOperand(0);
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return V;
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}
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const SCEV *llvm::replaceSymbolicStrideSCEV(ScalarEvolution *SE,
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ValueToValueMap &PtrToStride,
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Value *Ptr, Value *OrigPtr) {
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const SCEV *OrigSCEV = SE->getSCEV(Ptr);
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// If there is an entry in the map return the SCEV of the pointer with the
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// symbolic stride replaced by one.
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ValueToValueMap::iterator SI = PtrToStride.find(OrigPtr ? OrigPtr : Ptr);
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if (SI != PtrToStride.end()) {
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Value *StrideVal = SI->second;
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// Strip casts.
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StrideVal = stripIntegerCast(StrideVal);
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// Replace symbolic stride by one.
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Value *One = ConstantInt::get(StrideVal->getType(), 1);
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ValueToValueMap RewriteMap;
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RewriteMap[StrideVal] = One;
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const SCEV *ByOne =
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SCEVParameterRewriter::rewrite(OrigSCEV, *SE, RewriteMap, true);
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DEBUG(dbgs() << "LV: Replacing SCEV: " << *OrigSCEV << " by: " << *ByOne
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<< "\n");
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return ByOne;
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}
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// Otherwise, just return the SCEV of the original pointer.
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return SE->getSCEV(Ptr);
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}
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void LoopAccessAnalysis::RuntimePointerCheck::insert(ScalarEvolution *SE,
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Loop *Lp, Value *Ptr,
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bool WritePtr,
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unsigned DepSetId,
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unsigned ASId,
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ValueToValueMap &Strides) {
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// Get the stride replaced scev.
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const SCEV *Sc = replaceSymbolicStrideSCEV(SE, Strides, Ptr);
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const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
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assert(AR && "Invalid addrec expression");
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const SCEV *Ex = SE->getBackedgeTakenCount(Lp);
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const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
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Pointers.push_back(Ptr);
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Starts.push_back(AR->getStart());
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Ends.push_back(ScEnd);
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IsWritePtr.push_back(WritePtr);
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DependencySetId.push_back(DepSetId);
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AliasSetId.push_back(ASId);
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}
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namespace {
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/// \brief Analyses memory accesses in a loop.
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///
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/// Checks whether run time pointer checks are needed and builds sets for data
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/// dependence checking.
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class AccessAnalysis {
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public:
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/// \brief Read or write access location.
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typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
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typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
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/// \brief Set of potential dependent memory accesses.
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typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
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AccessAnalysis(const DataLayout *Dl, AliasAnalysis *AA, DepCandidates &DA) :
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DL(Dl), AST(*AA), DepCands(DA), IsRTCheckNeeded(false) {}
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/// \brief Register a load and whether it is only read from.
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void addLoad(AliasAnalysis::Location &Loc, bool IsReadOnly) {
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Value *Ptr = const_cast<Value*>(Loc.Ptr);
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AST.add(Ptr, AliasAnalysis::UnknownSize, Loc.AATags);
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Accesses.insert(MemAccessInfo(Ptr, false));
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if (IsReadOnly)
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ReadOnlyPtr.insert(Ptr);
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}
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/// \brief Register a store.
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void addStore(AliasAnalysis::Location &Loc) {
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Value *Ptr = const_cast<Value*>(Loc.Ptr);
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AST.add(Ptr, AliasAnalysis::UnknownSize, Loc.AATags);
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Accesses.insert(MemAccessInfo(Ptr, true));
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}
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/// \brief Check whether we can check the pointers at runtime for
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/// non-intersection.
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bool canCheckPtrAtRT(LoopAccessAnalysis::RuntimePointerCheck &RtCheck,
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unsigned &NumComparisons,
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ScalarEvolution *SE, Loop *TheLoop,
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ValueToValueMap &Strides,
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bool ShouldCheckStride = false);
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/// \brief Goes over all memory accesses, checks whether a RT check is needed
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/// and builds sets of dependent accesses.
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void buildDependenceSets() {
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processMemAccesses();
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}
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bool isRTCheckNeeded() { return IsRTCheckNeeded; }
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bool isDependencyCheckNeeded() { return !CheckDeps.empty(); }
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void resetDepChecks() { CheckDeps.clear(); }
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MemAccessInfoSet &getDependenciesToCheck() { return CheckDeps; }
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private:
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typedef SetVector<MemAccessInfo> PtrAccessSet;
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/// \brief Go over all memory access and check whether runtime pointer checks
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/// are needed /// and build sets of dependency check candidates.
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void processMemAccesses();
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/// Set of all accesses.
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PtrAccessSet Accesses;
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/// Set of accesses that need a further dependence check.
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MemAccessInfoSet CheckDeps;
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/// Set of pointers that are read only.
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SmallPtrSet<Value*, 16> ReadOnlyPtr;
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const DataLayout *DL;
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/// An alias set tracker to partition the access set by underlying object and
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//intrinsic property (such as TBAA metadata).
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AliasSetTracker AST;
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/// Sets of potentially dependent accesses - members of one set share an
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/// underlying pointer. The set "CheckDeps" identfies which sets really need a
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/// dependence check.
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DepCandidates &DepCands;
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bool IsRTCheckNeeded;
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};
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} // end anonymous namespace
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/// \brief Check whether a pointer can participate in a runtime bounds check.
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static bool hasComputableBounds(ScalarEvolution *SE, ValueToValueMap &Strides,
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Value *Ptr) {
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const SCEV *PtrScev = replaceSymbolicStrideSCEV(SE, Strides, Ptr);
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const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
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if (!AR)
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return false;
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return AR->isAffine();
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}
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/// \brief Check the stride of the pointer and ensure that it does not wrap in
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/// the address space.
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static int isStridedPtr(ScalarEvolution *SE, const DataLayout *DL, Value *Ptr,
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const Loop *Lp, ValueToValueMap &StridesMap);
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bool AccessAnalysis::canCheckPtrAtRT(
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LoopAccessAnalysis::RuntimePointerCheck &RtCheck,
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unsigned &NumComparisons, ScalarEvolution *SE, Loop *TheLoop,
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ValueToValueMap &StridesMap, bool ShouldCheckStride) {
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// Find pointers with computable bounds. We are going to use this information
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// to place a runtime bound check.
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bool CanDoRT = true;
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bool IsDepCheckNeeded = isDependencyCheckNeeded();
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NumComparisons = 0;
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// We assign a consecutive id to access from different alias sets.
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// Accesses between different groups doesn't need to be checked.
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unsigned ASId = 1;
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for (auto &AS : AST) {
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unsigned NumReadPtrChecks = 0;
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unsigned NumWritePtrChecks = 0;
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// We assign consecutive id to access from different dependence sets.
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// Accesses within the same set don't need a runtime check.
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unsigned RunningDepId = 1;
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DenseMap<Value *, unsigned> DepSetId;
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for (auto A : AS) {
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Value *Ptr = A.getValue();
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bool IsWrite = Accesses.count(MemAccessInfo(Ptr, true));
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MemAccessInfo Access(Ptr, IsWrite);
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if (IsWrite)
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++NumWritePtrChecks;
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else
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++NumReadPtrChecks;
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if (hasComputableBounds(SE, StridesMap, Ptr) &&
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// When we run after a failing dependency check we have to make sure we
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// don't have wrapping pointers.
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(!ShouldCheckStride ||
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isStridedPtr(SE, DL, Ptr, TheLoop, StridesMap) == 1)) {
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// The id of the dependence set.
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unsigned DepId;
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if (IsDepCheckNeeded) {
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Value *Leader = DepCands.getLeaderValue(Access).getPointer();
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unsigned &LeaderId = DepSetId[Leader];
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if (!LeaderId)
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LeaderId = RunningDepId++;
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DepId = LeaderId;
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} else
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// Each access has its own dependence set.
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DepId = RunningDepId++;
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RtCheck.insert(SE, TheLoop, Ptr, IsWrite, DepId, ASId, StridesMap);
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DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *Ptr << '\n');
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} else {
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CanDoRT = false;
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}
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}
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if (IsDepCheckNeeded && CanDoRT && RunningDepId == 2)
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NumComparisons += 0; // Only one dependence set.
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else {
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NumComparisons += (NumWritePtrChecks * (NumReadPtrChecks +
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NumWritePtrChecks - 1));
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}
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++ASId;
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}
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// If the pointers that we would use for the bounds comparison have different
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// address spaces, assume the values aren't directly comparable, so we can't
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// use them for the runtime check. We also have to assume they could
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// overlap. In the future there should be metadata for whether address spaces
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// are disjoint.
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unsigned NumPointers = RtCheck.Pointers.size();
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for (unsigned i = 0; i < NumPointers; ++i) {
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for (unsigned j = i + 1; j < NumPointers; ++j) {
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// Only need to check pointers between two different dependency sets.
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if (RtCheck.DependencySetId[i] == RtCheck.DependencySetId[j])
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continue;
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// Only need to check pointers in the same alias set.
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if (RtCheck.AliasSetId[i] != RtCheck.AliasSetId[j])
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continue;
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Value *PtrI = RtCheck.Pointers[i];
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Value *PtrJ = RtCheck.Pointers[j];
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unsigned ASi = PtrI->getType()->getPointerAddressSpace();
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unsigned ASj = PtrJ->getType()->getPointerAddressSpace();
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if (ASi != ASj) {
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DEBUG(dbgs() << "LV: Runtime check would require comparison between"
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" different address spaces\n");
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return false;
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}
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}
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}
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return CanDoRT;
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}
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void AccessAnalysis::processMemAccesses() {
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// We process the set twice: first we process read-write pointers, last we
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// process read-only pointers. This allows us to skip dependence tests for
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// read-only pointers.
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DEBUG(dbgs() << "LV: Processing memory accesses...\n");
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DEBUG(dbgs() << " AST: "; AST.dump());
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DEBUG(dbgs() << "LV: Accesses:\n");
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DEBUG({
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for (auto A : Accesses)
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dbgs() << "\t" << *A.getPointer() << " (" <<
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(A.getInt() ? "write" : (ReadOnlyPtr.count(A.getPointer()) ?
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"read-only" : "read")) << ")\n";
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});
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// The AliasSetTracker has nicely partitioned our pointers by metadata
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// compatibility and potential for underlying-object overlap. As a result, we
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// only need to check for potential pointer dependencies within each alias
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// set.
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for (auto &AS : AST) {
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// Note that both the alias-set tracker and the alias sets themselves used
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// linked lists internally and so the iteration order here is deterministic
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// (matching the original instruction order within each set).
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bool SetHasWrite = false;
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// Map of pointers to last access encountered.
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typedef DenseMap<Value*, MemAccessInfo> UnderlyingObjToAccessMap;
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UnderlyingObjToAccessMap ObjToLastAccess;
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// Set of access to check after all writes have been processed.
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PtrAccessSet DeferredAccesses;
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// Iterate over each alias set twice, once to process read/write pointers,
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// and then to process read-only pointers.
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for (int SetIteration = 0; SetIteration < 2; ++SetIteration) {
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bool UseDeferred = SetIteration > 0;
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PtrAccessSet &S = UseDeferred ? DeferredAccesses : Accesses;
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for (auto AV : AS) {
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Value *Ptr = AV.getValue();
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// For a single memory access in AliasSetTracker, Accesses may contain
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// both read and write, and they both need to be handled for CheckDeps.
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for (auto AC : S) {
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if (AC.getPointer() != Ptr)
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continue;
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bool IsWrite = AC.getInt();
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// If we're using the deferred access set, then it contains only
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// reads.
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bool IsReadOnlyPtr = ReadOnlyPtr.count(Ptr) && !IsWrite;
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if (UseDeferred && !IsReadOnlyPtr)
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continue;
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// Otherwise, the pointer must be in the PtrAccessSet, either as a
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// read or a write.
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assert(((IsReadOnlyPtr && UseDeferred) || IsWrite ||
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S.count(MemAccessInfo(Ptr, false))) &&
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"Alias-set pointer not in the access set?");
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MemAccessInfo Access(Ptr, IsWrite);
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DepCands.insert(Access);
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// Memorize read-only pointers for later processing and skip them in
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// the first round (they need to be checked after we have seen all
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// write pointers). Note: we also mark pointer that are not
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// consecutive as "read-only" pointers (so that we check
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// "a[b[i]] +="). Hence, we need the second check for "!IsWrite".
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if (!UseDeferred && IsReadOnlyPtr) {
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DeferredAccesses.insert(Access);
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continue;
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}
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// If this is a write - check other reads and writes for conflicts. If
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// this is a read only check other writes for conflicts (but only if
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// there is no other write to the ptr - this is an optimization to
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// catch "a[i] = a[i] + " without having to do a dependence check).
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if ((IsWrite || IsReadOnlyPtr) && SetHasWrite) {
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CheckDeps.insert(Access);
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IsRTCheckNeeded = true;
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}
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if (IsWrite)
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SetHasWrite = true;
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// Create sets of pointers connected by a shared alias set and
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// underlying object.
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typedef SmallVector<Value *, 16> ValueVector;
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ValueVector TempObjects;
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GetUnderlyingObjects(Ptr, TempObjects, DL);
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for (Value *UnderlyingObj : TempObjects) {
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UnderlyingObjToAccessMap::iterator Prev =
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ObjToLastAccess.find(UnderlyingObj);
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if (Prev != ObjToLastAccess.end())
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DepCands.unionSets(Access, Prev->second);
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ObjToLastAccess[UnderlyingObj] = Access;
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}
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}
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}
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}
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}
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}
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namespace {
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/// \brief Checks memory dependences among accesses to the same underlying
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/// object to determine whether there vectorization is legal or not (and at
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/// which vectorization factor).
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///
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/// This class works under the assumption that we already checked that memory
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/// locations with different underlying pointers are "must-not alias".
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/// We use the ScalarEvolution framework to symbolically evalutate access
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/// functions pairs. Since we currently don't restructure the loop we can rely
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/// on the program order of memory accesses to determine their safety.
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/// At the moment we will only deem accesses as safe for:
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/// * A negative constant distance assuming program order.
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///
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/// Safe: tmp = a[i + 1]; OR a[i + 1] = x;
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/// a[i] = tmp; y = a[i];
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///
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/// The latter case is safe because later checks guarantuee that there can't
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/// be a cycle through a phi node (that is, we check that "x" and "y" is not
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/// the same variable: a header phi can only be an induction or a reduction, a
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/// reduction can't have a memory sink, an induction can't have a memory
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/// source). This is important and must not be violated (or we have to
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/// resort to checking for cycles through memory).
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///
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/// * A positive constant distance assuming program order that is bigger
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/// than the biggest memory access.
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///
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/// tmp = a[i] OR b[i] = x
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/// a[i+2] = tmp y = b[i+2];
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///
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/// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively.
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///
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/// * Zero distances and all accesses have the same size.
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///
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class MemoryDepChecker {
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public:
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typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
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typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
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MemoryDepChecker(ScalarEvolution *Se, const DataLayout *Dl, const Loop *L,
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const LoopAccessAnalysis::VectorizerParams &VectParams)
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: SE(Se), DL(Dl), InnermostLoop(L), AccessIdx(0),
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ShouldRetryWithRuntimeCheck(false), VectParams(VectParams) {}
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/// \brief Register the location (instructions are given increasing numbers)
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/// of a write access.
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void addAccess(StoreInst *SI) {
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Value *Ptr = SI->getPointerOperand();
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Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
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InstMap.push_back(SI);
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++AccessIdx;
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}
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/// \brief Register the location (instructions are given increasing numbers)
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/// of a write access.
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void addAccess(LoadInst *LI) {
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Value *Ptr = LI->getPointerOperand();
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Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
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InstMap.push_back(LI);
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++AccessIdx;
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}
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/// \brief Check whether the dependencies between the accesses are safe.
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///
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/// Only checks sets with elements in \p CheckDeps.
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bool areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
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MemAccessInfoSet &CheckDeps, ValueToValueMap &Strides);
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/// \brief The maximum number of bytes of a vector register we can vectorize
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/// the accesses safely with.
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unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
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/// \brief In same cases when the dependency check fails we can still
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/// vectorize the loop with a dynamic array access check.
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bool shouldRetryWithRuntimeCheck() { return ShouldRetryWithRuntimeCheck; }
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|
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private:
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ScalarEvolution *SE;
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const DataLayout *DL;
|
|
const Loop *InnermostLoop;
|
|
|
|
/// \brief Maps access locations (ptr, read/write) to program order.
|
|
DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
|
|
|
|
/// \brief Memory access instructions in program order.
|
|
SmallVector<Instruction *, 16> InstMap;
|
|
|
|
/// \brief The program order index to be used for the next instruction.
|
|
unsigned AccessIdx;
|
|
|
|
// We can access this many bytes in parallel safely.
|
|
unsigned MaxSafeDepDistBytes;
|
|
|
|
/// \brief If we see a non-constant dependence distance we can still try to
|
|
/// vectorize this loop with runtime checks.
|
|
bool ShouldRetryWithRuntimeCheck;
|
|
|
|
/// \brief Vectorizer parameters used by the analysis.
|
|
LoopAccessAnalysis::VectorizerParams VectParams;
|
|
|
|
/// \brief Check whether there is a plausible dependence between the two
|
|
/// accesses.
|
|
///
|
|
/// Access \p A must happen before \p B in program order. The two indices
|
|
/// identify the index into the program order map.
|
|
///
|
|
/// This function checks whether there is a plausible dependence (or the
|
|
/// absence of such can't be proved) between the two accesses. If there is a
|
|
/// plausible dependence but the dependence distance is bigger than one
|
|
/// element access it records this distance in \p MaxSafeDepDistBytes (if this
|
|
/// distance is smaller than any other distance encountered so far).
|
|
/// Otherwise, this function returns true signaling a possible dependence.
|
|
bool isDependent(const MemAccessInfo &A, unsigned AIdx,
|
|
const MemAccessInfo &B, unsigned BIdx,
|
|
ValueToValueMap &Strides);
|
|
|
|
/// \brief Check whether the data dependence could prevent store-load
|
|
/// forwarding.
|
|
bool couldPreventStoreLoadForward(unsigned Distance, unsigned TypeByteSize);
|
|
};
|
|
|
|
} // end anonymous namespace
|
|
|
|
static bool isInBoundsGep(Value *Ptr) {
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr))
|
|
return GEP->isInBounds();
|
|
return false;
|
|
}
|
|
|
|
/// \brief Check whether the access through \p Ptr has a constant stride.
|
|
static int isStridedPtr(ScalarEvolution *SE, const DataLayout *DL, Value *Ptr,
|
|
const Loop *Lp, ValueToValueMap &StridesMap) {
|
|
const Type *Ty = Ptr->getType();
|
|
assert(Ty->isPointerTy() && "Unexpected non-ptr");
|
|
|
|
// Make sure that the pointer does not point to aggregate types.
|
|
const PointerType *PtrTy = cast<PointerType>(Ty);
|
|
if (PtrTy->getElementType()->isAggregateType()) {
|
|
DEBUG(dbgs() << "LV: Bad stride - Not a pointer to a scalar type" << *Ptr <<
|
|
"\n");
|
|
return 0;
|
|
}
|
|
|
|
const SCEV *PtrScev = replaceSymbolicStrideSCEV(SE, StridesMap, Ptr);
|
|
|
|
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
|
|
if (!AR) {
|
|
DEBUG(dbgs() << "LV: Bad stride - Not an AddRecExpr pointer "
|
|
<< *Ptr << " SCEV: " << *PtrScev << "\n");
|
|
return 0;
|
|
}
|
|
|
|
// The accesss function must stride over the innermost loop.
|
|
if (Lp != AR->getLoop()) {
|
|
DEBUG(dbgs() << "LV: Bad stride - Not striding over innermost loop " <<
|
|
*Ptr << " SCEV: " << *PtrScev << "\n");
|
|
}
|
|
|
|
// The address calculation must not wrap. Otherwise, a dependence could be
|
|
// inverted.
|
|
// An inbounds getelementptr that is a AddRec with a unit stride
|
|
// cannot wrap per definition. The unit stride requirement is checked later.
|
|
// An getelementptr without an inbounds attribute and unit stride would have
|
|
// to access the pointer value "0" which is undefined behavior in address
|
|
// space 0, therefore we can also vectorize this case.
|
|
bool IsInBoundsGEP = isInBoundsGep(Ptr);
|
|
bool IsNoWrapAddRec = AR->getNoWrapFlags(SCEV::NoWrapMask);
|
|
bool IsInAddressSpaceZero = PtrTy->getAddressSpace() == 0;
|
|
if (!IsNoWrapAddRec && !IsInBoundsGEP && !IsInAddressSpaceZero) {
|
|
DEBUG(dbgs() << "LV: Bad stride - Pointer may wrap in the address space "
|
|
<< *Ptr << " SCEV: " << *PtrScev << "\n");
|
|
return 0;
|
|
}
|
|
|
|
// Check the step is constant.
|
|
const SCEV *Step = AR->getStepRecurrence(*SE);
|
|
|
|
// Calculate the pointer stride and check if it is consecutive.
|
|
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
|
|
if (!C) {
|
|
DEBUG(dbgs() << "LV: Bad stride - Not a constant strided " << *Ptr <<
|
|
" SCEV: " << *PtrScev << "\n");
|
|
return 0;
|
|
}
|
|
|
|
int64_t Size = DL->getTypeAllocSize(PtrTy->getElementType());
|
|
const APInt &APStepVal = C->getValue()->getValue();
|
|
|
|
// Huge step value - give up.
|
|
if (APStepVal.getBitWidth() > 64)
|
|
return 0;
|
|
|
|
int64_t StepVal = APStepVal.getSExtValue();
|
|
|
|
// Strided access.
|
|
int64_t Stride = StepVal / Size;
|
|
int64_t Rem = StepVal % Size;
|
|
if (Rem)
|
|
return 0;
|
|
|
|
// If the SCEV could wrap but we have an inbounds gep with a unit stride we
|
|
// know we can't "wrap around the address space". In case of address space
|
|
// zero we know that this won't happen without triggering undefined behavior.
|
|
if (!IsNoWrapAddRec && (IsInBoundsGEP || IsInAddressSpaceZero) &&
|
|
Stride != 1 && Stride != -1)
|
|
return 0;
|
|
|
|
return Stride;
|
|
}
|
|
|
|
bool MemoryDepChecker::couldPreventStoreLoadForward(unsigned Distance,
|
|
unsigned TypeByteSize) {
|
|
// If loads occur at a distance that is not a multiple of a feasible vector
|
|
// factor store-load forwarding does not take place.
|
|
// Positive dependences might cause troubles because vectorizing them might
|
|
// prevent store-load forwarding making vectorized code run a lot slower.
|
|
// a[i] = a[i-3] ^ a[i-8];
|
|
// The stores to a[i:i+1] don't align with the stores to a[i-3:i-2] and
|
|
// hence on your typical architecture store-load forwarding does not take
|
|
// place. Vectorizing in such cases does not make sense.
|
|
// Store-load forwarding distance.
|
|
const unsigned NumCyclesForStoreLoadThroughMemory = 8*TypeByteSize;
|
|
// Maximum vector factor.
|
|
unsigned MaxVFWithoutSLForwardIssues = VectParams.MaxVectorWidth*TypeByteSize;
|
|
if(MaxSafeDepDistBytes < MaxVFWithoutSLForwardIssues)
|
|
MaxVFWithoutSLForwardIssues = MaxSafeDepDistBytes;
|
|
|
|
for (unsigned vf = 2*TypeByteSize; vf <= MaxVFWithoutSLForwardIssues;
|
|
vf *= 2) {
|
|
if (Distance % vf && Distance / vf < NumCyclesForStoreLoadThroughMemory) {
|
|
MaxVFWithoutSLForwardIssues = (vf >>=1);
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (MaxVFWithoutSLForwardIssues< 2*TypeByteSize) {
|
|
DEBUG(dbgs() << "LV: Distance " << Distance <<
|
|
" that could cause a store-load forwarding conflict\n");
|
|
return true;
|
|
}
|
|
|
|
if (MaxVFWithoutSLForwardIssues < MaxSafeDepDistBytes &&
|
|
MaxVFWithoutSLForwardIssues != VectParams.MaxVectorWidth*TypeByteSize)
|
|
MaxSafeDepDistBytes = MaxVFWithoutSLForwardIssues;
|
|
return false;
|
|
}
|
|
|
|
bool MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
|
|
const MemAccessInfo &B, unsigned BIdx,
|
|
ValueToValueMap &Strides) {
|
|
assert (AIdx < BIdx && "Must pass arguments in program order");
|
|
|
|
Value *APtr = A.getPointer();
|
|
Value *BPtr = B.getPointer();
|
|
bool AIsWrite = A.getInt();
|
|
bool BIsWrite = B.getInt();
|
|
|
|
// Two reads are independent.
|
|
if (!AIsWrite && !BIsWrite)
|
|
return false;
|
|
|
|
// We cannot check pointers in different address spaces.
|
|
if (APtr->getType()->getPointerAddressSpace() !=
|
|
BPtr->getType()->getPointerAddressSpace())
|
|
return true;
|
|
|
|
const SCEV *AScev = replaceSymbolicStrideSCEV(SE, Strides, APtr);
|
|
const SCEV *BScev = replaceSymbolicStrideSCEV(SE, Strides, BPtr);
|
|
|
|
int StrideAPtr = isStridedPtr(SE, DL, APtr, InnermostLoop, Strides);
|
|
int StrideBPtr = isStridedPtr(SE, DL, BPtr, InnermostLoop, Strides);
|
|
|
|
const SCEV *Src = AScev;
|
|
const SCEV *Sink = BScev;
|
|
|
|
// If the induction step is negative we have to invert source and sink of the
|
|
// dependence.
|
|
if (StrideAPtr < 0) {
|
|
//Src = BScev;
|
|
//Sink = AScev;
|
|
std::swap(APtr, BPtr);
|
|
std::swap(Src, Sink);
|
|
std::swap(AIsWrite, BIsWrite);
|
|
std::swap(AIdx, BIdx);
|
|
std::swap(StrideAPtr, StrideBPtr);
|
|
}
|
|
|
|
const SCEV *Dist = SE->getMinusSCEV(Sink, Src);
|
|
|
|
DEBUG(dbgs() << "LV: Src Scev: " << *Src << "Sink Scev: " << *Sink
|
|
<< "(Induction step: " << StrideAPtr << ")\n");
|
|
DEBUG(dbgs() << "LV: Distance for " << *InstMap[AIdx] << " to "
|
|
<< *InstMap[BIdx] << ": " << *Dist << "\n");
|
|
|
|
// Need consecutive accesses. We don't want to vectorize
|
|
// "A[B[i]] += ..." and similar code or pointer arithmetic that could wrap in
|
|
// the address space.
|
|
if (!StrideAPtr || !StrideBPtr || StrideAPtr != StrideBPtr){
|
|
DEBUG(dbgs() << "Non-consecutive pointer access\n");
|
|
return true;
|
|
}
|
|
|
|
const SCEVConstant *C = dyn_cast<SCEVConstant>(Dist);
|
|
if (!C) {
|
|
DEBUG(dbgs() << "LV: Dependence because of non-constant distance\n");
|
|
ShouldRetryWithRuntimeCheck = true;
|
|
return true;
|
|
}
|
|
|
|
Type *ATy = APtr->getType()->getPointerElementType();
|
|
Type *BTy = BPtr->getType()->getPointerElementType();
|
|
unsigned TypeByteSize = DL->getTypeAllocSize(ATy);
|
|
|
|
// Negative distances are not plausible dependencies.
|
|
const APInt &Val = C->getValue()->getValue();
|
|
if (Val.isNegative()) {
|
|
bool IsTrueDataDependence = (AIsWrite && !BIsWrite);
|
|
if (IsTrueDataDependence &&
|
|
(couldPreventStoreLoadForward(Val.abs().getZExtValue(), TypeByteSize) ||
|
|
ATy != BTy))
|
|
return true;
|
|
|
|
DEBUG(dbgs() << "LV: Dependence is negative: NoDep\n");
|
|
return false;
|
|
}
|
|
|
|
// Write to the same location with the same size.
|
|
// Could be improved to assert type sizes are the same (i32 == float, etc).
|
|
if (Val == 0) {
|
|
if (ATy == BTy)
|
|
return false;
|
|
DEBUG(dbgs() << "LV: Zero dependence difference but different types\n");
|
|
return true;
|
|
}
|
|
|
|
assert(Val.isStrictlyPositive() && "Expect a positive value");
|
|
|
|
// Positive distance bigger than max vectorization factor.
|
|
if (ATy != BTy) {
|
|
DEBUG(dbgs() <<
|
|
"LV: ReadWrite-Write positive dependency with different types\n");
|
|
return false;
|
|
}
|
|
|
|
unsigned Distance = (unsigned) Val.getZExtValue();
|
|
|
|
// Bail out early if passed-in parameters make vectorization not feasible.
|
|
unsigned ForcedFactor = (VectParams.VectorizationFactor ?
|
|
VectParams.VectorizationFactor : 1);
|
|
unsigned ForcedUnroll = (VectParams.VectorizationInterleave ?
|
|
VectParams.VectorizationInterleave : 1);
|
|
|
|
// The distance must be bigger than the size needed for a vectorized version
|
|
// of the operation and the size of the vectorized operation must not be
|
|
// bigger than the currrent maximum size.
|
|
if (Distance < 2*TypeByteSize ||
|
|
2*TypeByteSize > MaxSafeDepDistBytes ||
|
|
Distance < TypeByteSize * ForcedUnroll * ForcedFactor) {
|
|
DEBUG(dbgs() << "LV: Failure because of Positive distance "
|
|
<< Val.getSExtValue() << '\n');
|
|
return true;
|
|
}
|
|
|
|
MaxSafeDepDistBytes = Distance < MaxSafeDepDistBytes ?
|
|
Distance : MaxSafeDepDistBytes;
|
|
|
|
bool IsTrueDataDependence = (!AIsWrite && BIsWrite);
|
|
if (IsTrueDataDependence &&
|
|
couldPreventStoreLoadForward(Distance, TypeByteSize))
|
|
return true;
|
|
|
|
DEBUG(dbgs() << "LV: Positive distance " << Val.getSExtValue() <<
|
|
" with max VF = " << MaxSafeDepDistBytes / TypeByteSize << '\n');
|
|
|
|
return false;
|
|
}
|
|
|
|
bool MemoryDepChecker::areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
|
|
MemAccessInfoSet &CheckDeps,
|
|
ValueToValueMap &Strides) {
|
|
|
|
MaxSafeDepDistBytes = -1U;
|
|
while (!CheckDeps.empty()) {
|
|
MemAccessInfo CurAccess = *CheckDeps.begin();
|
|
|
|
// Get the relevant memory access set.
|
|
EquivalenceClasses<MemAccessInfo>::iterator I =
|
|
AccessSets.findValue(AccessSets.getLeaderValue(CurAccess));
|
|
|
|
// Check accesses within this set.
|
|
EquivalenceClasses<MemAccessInfo>::member_iterator AI, AE;
|
|
AI = AccessSets.member_begin(I), AE = AccessSets.member_end();
|
|
|
|
// Check every access pair.
|
|
while (AI != AE) {
|
|
CheckDeps.erase(*AI);
|
|
EquivalenceClasses<MemAccessInfo>::member_iterator OI = std::next(AI);
|
|
while (OI != AE) {
|
|
// Check every accessing instruction pair in program order.
|
|
for (std::vector<unsigned>::iterator I1 = Accesses[*AI].begin(),
|
|
I1E = Accesses[*AI].end(); I1 != I1E; ++I1)
|
|
for (std::vector<unsigned>::iterator I2 = Accesses[*OI].begin(),
|
|
I2E = Accesses[*OI].end(); I2 != I2E; ++I2) {
|
|
if (*I1 < *I2 && isDependent(*AI, *I1, *OI, *I2, Strides))
|
|
return false;
|
|
if (*I2 < *I1 && isDependent(*OI, *I2, *AI, *I1, Strides))
|
|
return false;
|
|
}
|
|
++OI;
|
|
}
|
|
AI++;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool LoopAccessAnalysis::canVectorizeMemory(ValueToValueMap &Strides) {
|
|
|
|
typedef SmallVector<Value*, 16> ValueVector;
|
|
typedef SmallPtrSet<Value*, 16> ValueSet;
|
|
|
|
// Holds the Load and Store *instructions*.
|
|
ValueVector Loads;
|
|
ValueVector Stores;
|
|
|
|
// Holds all the different accesses in the loop.
|
|
unsigned NumReads = 0;
|
|
unsigned NumReadWrites = 0;
|
|
|
|
PtrRtCheck.Pointers.clear();
|
|
PtrRtCheck.Need = false;
|
|
|
|
const bool IsAnnotatedParallel = TheLoop->isAnnotatedParallel();
|
|
MemoryDepChecker DepChecker(SE, DL, TheLoop, VectParams);
|
|
|
|
// For each block.
|
|
for (Loop::block_iterator bb = TheLoop->block_begin(),
|
|
be = TheLoop->block_end(); bb != be; ++bb) {
|
|
|
|
// Scan the BB and collect legal loads and stores.
|
|
for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
|
|
++it) {
|
|
|
|
// If this is a load, save it. If this instruction can read from memory
|
|
// but is not a load, then we quit. Notice that we don't handle function
|
|
// calls that read or write.
|
|
if (it->mayReadFromMemory()) {
|
|
// Many math library functions read the rounding mode. We will only
|
|
// vectorize a loop if it contains known function calls that don't set
|
|
// the flag. Therefore, it is safe to ignore this read from memory.
|
|
CallInst *Call = dyn_cast<CallInst>(it);
|
|
if (Call && getIntrinsicIDForCall(Call, TLI))
|
|
continue;
|
|
|
|
LoadInst *Ld = dyn_cast<LoadInst>(it);
|
|
if (!Ld || (!Ld->isSimple() && !IsAnnotatedParallel)) {
|
|
emitAnalysis(VectorizationReport(Ld)
|
|
<< "read with atomic ordering or volatile read");
|
|
DEBUG(dbgs() << "LV: Found a non-simple load.\n");
|
|
return false;
|
|
}
|
|
NumLoads++;
|
|
Loads.push_back(Ld);
|
|
DepChecker.addAccess(Ld);
|
|
continue;
|
|
}
|
|
|
|
// Save 'store' instructions. Abort if other instructions write to memory.
|
|
if (it->mayWriteToMemory()) {
|
|
StoreInst *St = dyn_cast<StoreInst>(it);
|
|
if (!St) {
|
|
emitAnalysis(VectorizationReport(it) <<
|
|
"instruction cannot be vectorized");
|
|
return false;
|
|
}
|
|
if (!St->isSimple() && !IsAnnotatedParallel) {
|
|
emitAnalysis(VectorizationReport(St)
|
|
<< "write with atomic ordering or volatile write");
|
|
DEBUG(dbgs() << "LV: Found a non-simple store.\n");
|
|
return false;
|
|
}
|
|
NumStores++;
|
|
Stores.push_back(St);
|
|
DepChecker.addAccess(St);
|
|
}
|
|
} // Next instr.
|
|
} // Next block.
|
|
|
|
// Now we have two lists that hold the loads and the stores.
|
|
// Next, we find the pointers that they use.
|
|
|
|
// Check if we see any stores. If there are no stores, then we don't
|
|
// care if the pointers are *restrict*.
|
|
if (!Stores.size()) {
|
|
DEBUG(dbgs() << "LV: Found a read-only loop!\n");
|
|
return true;
|
|
}
|
|
|
|
AccessAnalysis::DepCandidates DependentAccesses;
|
|
AccessAnalysis Accesses(DL, AA, DependentAccesses);
|
|
|
|
// Holds the analyzed pointers. We don't want to call GetUnderlyingObjects
|
|
// multiple times on the same object. If the ptr is accessed twice, once
|
|
// for read and once for write, it will only appear once (on the write
|
|
// list). This is okay, since we are going to check for conflicts between
|
|
// writes and between reads and writes, but not between reads and reads.
|
|
ValueSet Seen;
|
|
|
|
ValueVector::iterator I, IE;
|
|
for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
|
|
StoreInst *ST = cast<StoreInst>(*I);
|
|
Value* Ptr = ST->getPointerOperand();
|
|
|
|
if (isUniform(Ptr)) {
|
|
emitAnalysis(
|
|
VectorizationReport(ST)
|
|
<< "write to a loop invariant address could not be vectorized");
|
|
DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n");
|
|
return false;
|
|
}
|
|
|
|
// If we did *not* see this pointer before, insert it to the read-write
|
|
// list. At this phase it is only a 'write' list.
|
|
if (Seen.insert(Ptr).second) {
|
|
++NumReadWrites;
|
|
|
|
AliasAnalysis::Location Loc = AA->getLocation(ST);
|
|
// The TBAA metadata could have a control dependency on the predication
|
|
// condition, so we cannot rely on it when determining whether or not we
|
|
// need runtime pointer checks.
|
|
if (blockNeedsPredication(ST->getParent()))
|
|
Loc.AATags.TBAA = nullptr;
|
|
|
|
Accesses.addStore(Loc);
|
|
}
|
|
}
|
|
|
|
if (IsAnnotatedParallel) {
|
|
DEBUG(dbgs()
|
|
<< "LV: A loop annotated parallel, ignore memory dependency "
|
|
<< "checks.\n");
|
|
return true;
|
|
}
|
|
|
|
for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
|
|
LoadInst *LD = cast<LoadInst>(*I);
|
|
Value* Ptr = LD->getPointerOperand();
|
|
// If we did *not* see this pointer before, insert it to the
|
|
// read list. If we *did* see it before, then it is already in
|
|
// the read-write list. This allows us to vectorize expressions
|
|
// such as A[i] += x; Because the address of A[i] is a read-write
|
|
// pointer. This only works if the index of A[i] is consecutive.
|
|
// If the address of i is unknown (for example A[B[i]]) then we may
|
|
// read a few words, modify, and write a few words, and some of the
|
|
// words may be written to the same address.
|
|
bool IsReadOnlyPtr = false;
|
|
if (Seen.insert(Ptr).second ||
|
|
!isStridedPtr(SE, DL, Ptr, TheLoop, Strides)) {
|
|
++NumReads;
|
|
IsReadOnlyPtr = true;
|
|
}
|
|
|
|
AliasAnalysis::Location Loc = AA->getLocation(LD);
|
|
// The TBAA metadata could have a control dependency on the predication
|
|
// condition, so we cannot rely on it when determining whether or not we
|
|
// need runtime pointer checks.
|
|
if (blockNeedsPredication(LD->getParent()))
|
|
Loc.AATags.TBAA = nullptr;
|
|
|
|
Accesses.addLoad(Loc, IsReadOnlyPtr);
|
|
}
|
|
|
|
// If we write (or read-write) to a single destination and there are no
|
|
// other reads in this loop then is it safe to vectorize.
|
|
if (NumReadWrites == 1 && NumReads == 0) {
|
|
DEBUG(dbgs() << "LV: Found a write-only loop!\n");
|
|
return true;
|
|
}
|
|
|
|
// Build dependence sets and check whether we need a runtime pointer bounds
|
|
// check.
|
|
Accesses.buildDependenceSets();
|
|
bool NeedRTCheck = Accesses.isRTCheckNeeded();
|
|
|
|
// Find pointers with computable bounds. We are going to use this information
|
|
// to place a runtime bound check.
|
|
unsigned NumComparisons = 0;
|
|
bool CanDoRT = false;
|
|
if (NeedRTCheck)
|
|
CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE, TheLoop,
|
|
Strides);
|
|
|
|
DEBUG(dbgs() << "LV: We need to do " << NumComparisons <<
|
|
" pointer comparisons.\n");
|
|
|
|
// If we only have one set of dependences to check pointers among we don't
|
|
// need a runtime check.
|
|
if (NumComparisons == 0 && NeedRTCheck)
|
|
NeedRTCheck = false;
|
|
|
|
// Check that we did not collect too many pointers or found an unsizeable
|
|
// pointer.
|
|
if (!CanDoRT || NumComparisons > VectParams.RuntimeMemoryCheckThreshold) {
|
|
PtrRtCheck.reset();
|
|
CanDoRT = false;
|
|
}
|
|
|
|
if (CanDoRT) {
|
|
DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
|
|
}
|
|
|
|
if (NeedRTCheck && !CanDoRT) {
|
|
emitAnalysis(VectorizationReport() << "cannot identify array bounds");
|
|
DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
|
|
"the array bounds.\n");
|
|
PtrRtCheck.reset();
|
|
return false;
|
|
}
|
|
|
|
PtrRtCheck.Need = NeedRTCheck;
|
|
|
|
bool CanVecMem = true;
|
|
if (Accesses.isDependencyCheckNeeded()) {
|
|
DEBUG(dbgs() << "LV: Checking memory dependencies\n");
|
|
CanVecMem = DepChecker.areDepsSafe(
|
|
DependentAccesses, Accesses.getDependenciesToCheck(), Strides);
|
|
MaxSafeDepDistBytes = DepChecker.getMaxSafeDepDistBytes();
|
|
|
|
if (!CanVecMem && DepChecker.shouldRetryWithRuntimeCheck()) {
|
|
DEBUG(dbgs() << "LV: Retrying with memory checks\n");
|
|
NeedRTCheck = true;
|
|
|
|
// Clear the dependency checks. We assume they are not needed.
|
|
Accesses.resetDepChecks();
|
|
|
|
PtrRtCheck.reset();
|
|
PtrRtCheck.Need = true;
|
|
|
|
CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE,
|
|
TheLoop, Strides, true);
|
|
// Check that we did not collect too many pointers or found an unsizeable
|
|
// pointer.
|
|
if (!CanDoRT || NumComparisons > VectParams.RuntimeMemoryCheckThreshold) {
|
|
if (!CanDoRT && NumComparisons > 0)
|
|
emitAnalysis(VectorizationReport()
|
|
<< "cannot check memory dependencies at runtime");
|
|
else
|
|
emitAnalysis(VectorizationReport()
|
|
<< NumComparisons << " exceeds limit of "
|
|
<< VectParams.RuntimeMemoryCheckThreshold
|
|
<< " dependent memory operations checked at runtime");
|
|
DEBUG(dbgs() << "LV: Can't vectorize with memory checks\n");
|
|
PtrRtCheck.reset();
|
|
return false;
|
|
}
|
|
|
|
CanVecMem = true;
|
|
}
|
|
}
|
|
|
|
if (!CanVecMem)
|
|
emitAnalysis(VectorizationReport() <<
|
|
"unsafe dependent memory operations in loop");
|
|
|
|
DEBUG(dbgs() << "LV: We" << (NeedRTCheck ? "" : " don't") <<
|
|
" need a runtime memory check.\n");
|
|
|
|
return CanVecMem;
|
|
}
|
|
|
|
bool LoopAccessAnalysis::blockNeedsPredication(BasicBlock *BB) {
|
|
assert(TheLoop->contains(BB) && "Unknown block used");
|
|
|
|
// Blocks that do not dominate the latch need predication.
|
|
BasicBlock* Latch = TheLoop->getLoopLatch();
|
|
return !DT->dominates(BB, Latch);
|
|
}
|
|
|
|
void LoopAccessAnalysis::emitAnalysis(VectorizationReport &Message) {
|
|
VectorizationReport::emitAnalysis(Message, TheFunction, TheLoop);
|
|
}
|
|
|
|
bool LoopAccessAnalysis::isUniform(Value *V) {
|
|
return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
|
|
}
|
|
|
|
// FIXME: this function is currently a duplicate of the one in
|
|
// LoopVectorize.cpp.
|
|
static Instruction *getFirstInst(Instruction *FirstInst, Value *V,
|
|
Instruction *Loc) {
|
|
if (FirstInst)
|
|
return FirstInst;
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
|
return I->getParent() == Loc->getParent() ? I : nullptr;
|
|
return nullptr;
|
|
}
|
|
|
|
std::pair<Instruction *, Instruction *>
|
|
LoopAccessAnalysis::addRuntimeCheck(Instruction *Loc) {
|
|
Instruction *tnullptr = nullptr;
|
|
if (!PtrRtCheck.Need)
|
|
return std::pair<Instruction *, Instruction *>(tnullptr, tnullptr);
|
|
|
|
unsigned NumPointers = PtrRtCheck.Pointers.size();
|
|
SmallVector<TrackingVH<Value> , 2> Starts;
|
|
SmallVector<TrackingVH<Value> , 2> Ends;
|
|
|
|
LLVMContext &Ctx = Loc->getContext();
|
|
SCEVExpander Exp(*SE, "induction");
|
|
Instruction *FirstInst = nullptr;
|
|
|
|
for (unsigned i = 0; i < NumPointers; ++i) {
|
|
Value *Ptr = PtrRtCheck.Pointers[i];
|
|
const SCEV *Sc = SE->getSCEV(Ptr);
|
|
|
|
if (SE->isLoopInvariant(Sc, TheLoop)) {
|
|
DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
|
|
*Ptr <<"\n");
|
|
Starts.push_back(Ptr);
|
|
Ends.push_back(Ptr);
|
|
} else {
|
|
DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr << '\n');
|
|
unsigned AS = Ptr->getType()->getPointerAddressSpace();
|
|
|
|
// Use this type for pointer arithmetic.
|
|
Type *PtrArithTy = Type::getInt8PtrTy(Ctx, AS);
|
|
|
|
Value *Start = Exp.expandCodeFor(PtrRtCheck.Starts[i], PtrArithTy, Loc);
|
|
Value *End = Exp.expandCodeFor(PtrRtCheck.Ends[i], PtrArithTy, Loc);
|
|
Starts.push_back(Start);
|
|
Ends.push_back(End);
|
|
}
|
|
}
|
|
|
|
IRBuilder<> ChkBuilder(Loc);
|
|
// Our instructions might fold to a constant.
|
|
Value *MemoryRuntimeCheck = nullptr;
|
|
for (unsigned i = 0; i < NumPointers; ++i) {
|
|
for (unsigned j = i+1; j < NumPointers; ++j) {
|
|
// No need to check if two readonly pointers intersect.
|
|
if (!PtrRtCheck.IsWritePtr[i] && !PtrRtCheck.IsWritePtr[j])
|
|
continue;
|
|
|
|
// Only need to check pointers between two different dependency sets.
|
|
if (PtrRtCheck.DependencySetId[i] == PtrRtCheck.DependencySetId[j])
|
|
continue;
|
|
// Only need to check pointers in the same alias set.
|
|
if (PtrRtCheck.AliasSetId[i] != PtrRtCheck.AliasSetId[j])
|
|
continue;
|
|
|
|
unsigned AS0 = Starts[i]->getType()->getPointerAddressSpace();
|
|
unsigned AS1 = Starts[j]->getType()->getPointerAddressSpace();
|
|
|
|
assert((AS0 == Ends[j]->getType()->getPointerAddressSpace()) &&
|
|
(AS1 == Ends[i]->getType()->getPointerAddressSpace()) &&
|
|
"Trying to bounds check pointers with different address spaces");
|
|
|
|
Type *PtrArithTy0 = Type::getInt8PtrTy(Ctx, AS0);
|
|
Type *PtrArithTy1 = Type::getInt8PtrTy(Ctx, AS1);
|
|
|
|
Value *Start0 = ChkBuilder.CreateBitCast(Starts[i], PtrArithTy0, "bc");
|
|
Value *Start1 = ChkBuilder.CreateBitCast(Starts[j], PtrArithTy1, "bc");
|
|
Value *End0 = ChkBuilder.CreateBitCast(Ends[i], PtrArithTy1, "bc");
|
|
Value *End1 = ChkBuilder.CreateBitCast(Ends[j], PtrArithTy0, "bc");
|
|
|
|
Value *Cmp0 = ChkBuilder.CreateICmpULE(Start0, End1, "bound0");
|
|
FirstInst = getFirstInst(FirstInst, Cmp0, Loc);
|
|
Value *Cmp1 = ChkBuilder.CreateICmpULE(Start1, End0, "bound1");
|
|
FirstInst = getFirstInst(FirstInst, Cmp1, Loc);
|
|
Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
|
|
FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
|
|
if (MemoryRuntimeCheck) {
|
|
IsConflict = ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict,
|
|
"conflict.rdx");
|
|
FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
|
|
}
|
|
MemoryRuntimeCheck = IsConflict;
|
|
}
|
|
}
|
|
|
|
// We have to do this trickery because the IRBuilder might fold the check to a
|
|
// constant expression in which case there is no Instruction anchored in a
|
|
// the block.
|
|
Instruction *Check = BinaryOperator::CreateAnd(MemoryRuntimeCheck,
|
|
ConstantInt::getTrue(Ctx));
|
|
ChkBuilder.Insert(Check, "memcheck.conflict");
|
|
FirstInst = getFirstInst(FirstInst, Check, Loc);
|
|
return std::make_pair(FirstInst, Check);
|
|
}
|