#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include <algorithm>
using namespace llvm;
/// cannot be involved in a cycle.
const unsigned MaxNumPhiBBsValueReachabilityCheck = 20;
+// The max limit of the search depth in DecomposeGEPExpression() and
+// GetUnderlyingObject(), both functions need to use the same search
+// depth otherwise the algorithm in aliasGEP will assert.
+static const unsigned MaxLookupSearchDepth = 6;
+
//===----------------------------------------------------------------------===//
// Useful predicates
//===----------------------------------------------------------------------===//
/// getObjectSize - Return the size of the object specified by V, or
/// UnknownSize if unknown.
-static uint64_t getObjectSize(const Value *V, const DataLayout &TD,
+static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
const TargetLibraryInfo &TLI,
bool RoundToAlign = false) {
uint64_t Size;
- if (getObjectSize(V, Size, &TD, &TLI, RoundToAlign))
+ if (getObjectSize(V, Size, &DL, &TLI, RoundToAlign))
return Size;
return AliasAnalysis::UnknownSize;
}
/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
static bool isObjectSmallerThan(const Value *V, uint64_t Size,
- const DataLayout &TD,
+ const DataLayout &DL,
const TargetLibraryInfo &TLI) {
// Note that the meanings of the "object" are slightly different in the
// following contexts:
// This function needs to use the aligned object size because we allow
// reads a bit past the end given sufficient alignment.
- uint64_t ObjectSize = getObjectSize(V, TD, TLI, /*RoundToAlign*/true);
+ uint64_t ObjectSize = getObjectSize(V, DL, TLI, /*RoundToAlign*/true);
return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize < Size;
}
/// isObjectSize - Return true if we can prove that the object specified
/// by V has size Size.
static bool isObjectSize(const Value *V, uint64_t Size,
- const DataLayout &TD, const TargetLibraryInfo &TLI) {
- uint64_t ObjectSize = getObjectSize(V, TD, TLI);
+ const DataLayout &DL, const TargetLibraryInfo &TLI) {
+ uint64_t ObjectSize = getObjectSize(V, DL, TLI);
return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize == Size;
}
/// isIdentifiedFunctionLocal - Return true if V is umabigously identified
/// at the function-level. Different IdentifiedFunctionLocals can't alias.
/// Further, an IdentifiedFunctionLocal can not alias with any function
-/// arguments other than itself, which is not neccessarily true for
+/// arguments other than itself, which is not necessarily true for
/// IdentifiedObjects.
static bool isIdentifiedFunctionLocal(const Value *V)
{
/// represented in the result.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
ExtensionKind &Extension,
- const DataLayout &TD, unsigned Depth) {
+ const DataLayout &DL, unsigned Depth) {
assert(V->getType()->isIntegerTy() && "Not an integer value");
// Limit our recursion depth.
case Instruction::Or:
// X|C == X+C if all the bits in C are unset in X. Otherwise we can't
// analyze it.
- if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), &TD))
+ if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), &DL))
break;
// FALL THROUGH.
case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- TD, Depth+1);
+ DL, Depth+1);
Offset += RHSC->getValue();
return V;
case Instruction::Mul:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- TD, Depth+1);
+ DL, Depth+1);
Offset *= RHSC->getValue();
Scale *= RHSC->getValue();
return V;
case Instruction::Shl:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- TD, Depth+1);
+ DL, Depth+1);
Offset <<= RHSC->getValue().getLimitedValue();
Scale <<= RHSC->getValue().getLimitedValue();
return V;
Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension,
- TD, Depth+1);
+ DL, Depth+1);
Scale = Scale.zext(OldWidth);
Offset = Offset.zext(OldWidth);
/// the gep cannot necessarily be reconstructed from its decomposed form.
///
/// When DataLayout is around, this function is capable of analyzing everything
-/// that GetUnderlyingObject can look through. When not, it just looks
-/// through pointer casts.
+/// that GetUnderlyingObject can look through. To be able to do that
+/// GetUnderlyingObject and DecomposeGEPExpression must use the same search
+/// depth (MaxLookupSearchDepth).
+/// When DataLayout not is around, it just looks through pointer casts.
///
static const Value *
DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
SmallVectorImpl<VariableGEPIndex> &VarIndices,
- const DataLayout *TD) {
+ bool &MaxLookupReached, const DataLayout *DL) {
// Limit recursion depth to limit compile time in crazy cases.
- unsigned MaxLookup = 6;
+ unsigned MaxLookup = MaxLookupSearchDepth;
+ MaxLookupReached = false;
BaseOffs = 0;
do {
// See if this is a bitcast or GEP.
const Operator *Op = dyn_cast<Operator>(V);
- if (Op == 0) {
+ if (!Op) {
// The only non-operator case we can handle are GlobalAliases.
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (!GA->mayBeOverridden()) {
}
const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
- if (GEPOp == 0) {
+ if (!GEPOp) {
// If it's not a GEP, hand it off to SimplifyInstruction to see if it
// can come up with something. This matches what GetUnderlyingObject does.
if (const Instruction *I = dyn_cast<Instruction>(V))
// TODO: Get a DominatorTree and use it here.
if (const Value *Simplified =
- SimplifyInstruction(const_cast<Instruction *>(I), TD)) {
+ SimplifyInstruction(const_cast<Instruction *>(I), DL)) {
V = Simplified;
continue;
}
// If we are lacking DataLayout information, we can't compute the offets of
// elements computed by GEPs. However, we can handle bitcast equivalent
// GEPs.
- if (TD == 0) {
+ if (!DL) {
if (!GEPOp->hasAllZeroIndices())
return V;
V = GEPOp->getOperand(0);
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
if (FieldNo == 0) continue;
- BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo);
+ BaseOffs += DL->getStructLayout(STy)->getElementOffset(FieldNo);
continue;
}
// For an array/pointer, add the element offset, explicitly scaled.
if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero()) continue;
- BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
+ BaseOffs += DL->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
continue;
}
- uint64_t Scale = TD->getTypeAllocSize(*GTI);
+ uint64_t Scale = DL->getTypeAllocSize(*GTI);
ExtensionKind Extension = EK_NotExtended;
// If the integer type is smaller than the pointer size, it is implicitly
// sign extended to pointer size.
unsigned Width = Index->getType()->getIntegerBitWidth();
- if (TD->getPointerSizeInBits(AS) > Width)
+ if (DL->getPointerSizeInBits(AS) > Width)
Extension = EK_SignExt;
// Use GetLinearExpression to decompose the index into a C1*V+C2 form.
APInt IndexScale(Width, 0), IndexOffset(Width, 0);
Index = GetLinearExpression(Index, IndexScale, IndexOffset, Extension,
- *TD, 0);
+ *DL, 0);
// The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
// This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
// Make sure that we have a scale that makes sense for this target's
// pointer size.
- if (unsigned ShiftBits = 64 - TD->getPointerSizeInBits(AS)) {
+ if (unsigned ShiftBits = 64 - DL->getPointerSizeInBits(AS)) {
Scale <<= ShiftBits;
Scale = (int64_t)Scale >> ShiftBits;
}
} while (--MaxLookup);
// If the chain of expressions is too deep, just return early.
+ MaxLookupReached = true;
return V;
}
if (const Argument *arg = dyn_cast<Argument>(V))
return arg->getParent();
- return NULL;
+ return nullptr;
}
static bool notDifferentParent(const Value *O1, const Value *O2) {
initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
}
- virtual void initializePass() {
+ void initializePass() override {
InitializeAliasAnalysis(this);
}
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AliasAnalysis>();
AU.addRequired<TargetLibraryInfo>();
}
- virtual AliasResult alias(const Location &LocA,
- const Location &LocB) {
+ AliasResult alias(const Location &LocA, const Location &LocB) override {
assert(AliasCache.empty() && "AliasCache must be cleared after use!");
assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
"BasicAliasAnalysis doesn't support interprocedural queries.");
return Alias;
}
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
- const Location &Loc);
+ ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Location &Loc) override;
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
- ImmutableCallSite CS2) {
+ ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) override {
// The AliasAnalysis base class has some smarts, lets use them.
return AliasAnalysis::getModRefInfo(CS1, CS2);
}
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
- virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
+ bool pointsToConstantMemory(const Location &Loc, bool OrLocal) override;
/// getModRefBehavior - Return the behavior when calling the given
/// call site.
- virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+ ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override;
/// getModRefBehavior - Return the behavior when calling the given function.
/// For use when the call site is not known.
- virtual ModRefBehavior getModRefBehavior(const Function *F);
+ ModRefBehavior getModRefBehavior(const Function *F) override;
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
/// should override this to adjust the this pointer as needed for the
/// specified pass info.
- virtual void *getAdjustedAnalysisPointer(const void *ID) {
+ void *getAdjustedAnalysisPointer(const void *ID) override {
if (ID == &AliasAnalysis::ID)
return (AliasAnalysis*)this;
return this;
SmallVector<const Value *, 16> Worklist;
Worklist.push_back(Loc.Ptr);
do {
- const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), TD);
+ const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), DL);
if (!Visited.insert(V)) {
Visited.clear();
return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
"AliasAnalysis query involving multiple functions!");
- const Value *Object = GetUnderlyingObject(Loc.Ptr, TD);
+ const Value *Object = GetUnderlyingObject(Loc.Ptr, DL);
// If this is a tail call and Loc.Ptr points to a stack location, we know that
// the tail call cannot access or modify the local stack.
// Finally, handle specific knowledge of intrinsics.
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
- if (II != 0)
+ if (II != nullptr)
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::memcpy:
// LLVM's vld1 and vst1 intrinsics currently only support a single
// vector register.
uint64_t Size =
- TD ? TD->getTypeStoreSize(II->getType()) : UnknownSize;
+ DL ? DL->getTypeStoreSize(II->getType()) : UnknownSize;
if (isNoAlias(Location(II->getArgOperand(0), Size,
II->getMetadata(LLVMContext::MD_tbaa)),
Loc))
}
case Intrinsic::arm_neon_vst1: {
uint64_t Size =
- TD ? TD->getTypeStoreSize(II->getArgOperand(1)->getType()) : UnknownSize;
+ DL ? DL->getTypeStoreSize(II->getArgOperand(1)->getType()) : UnknownSize;
if (isNoAlias(Location(II->getArgOperand(0), Size,
II->getMetadata(LLVMContext::MD_tbaa)),
Loc))
return ModRefResult(AliasAnalysis::getModRefInfo(CS, Loc) & Min);
}
-static bool areVarIndicesEqual(SmallVectorImpl<VariableGEPIndex> &Indices1,
- SmallVectorImpl<VariableGEPIndex> &Indices2) {
- unsigned Size1 = Indices1.size();
- unsigned Size2 = Indices2.size();
-
- if (Size1 != Size2)
- return false;
-
- for (unsigned I = 0; I != Size1; ++I)
- if (Indices1[I] != Indices2[I])
- return false;
-
- return true;
-}
-
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
/// against another pointer. We know that V1 is a GEP, but we don't know
-/// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, TD),
+/// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, DL),
/// UnderlyingV2 is the same for V2.
///
AliasAnalysis::AliasResult
const Value *UnderlyingV1,
const Value *UnderlyingV2) {
int64_t GEP1BaseOffset;
+ bool GEP1MaxLookupReached;
SmallVector<VariableGEPIndex, 4> GEP1VariableIndices;
// If we have two gep instructions with must-alias or not-alias'ing base
// derived pointer.
if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
// Do the base pointers alias?
- AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize, 0,
- UnderlyingV2, UnknownSize, 0);
+ AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize, nullptr,
+ UnderlyingV2, UnknownSize, nullptr);
// Check for geps of non-aliasing underlying pointers where the offsets are
// identical.
// See if the computed offset from the common pointer tells us about the
// relation of the resulting pointer.
int64_t GEP2BaseOffset;
+ bool GEP2MaxLookupReached;
SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
const Value *GEP2BasePtr =
- DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
+ DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices,
+ GEP2MaxLookupReached, DL);
const Value *GEP1BasePtr =
- DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
+ DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
+ GEP1MaxLookupReached, DL);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
- assert(TD == 0 &&
- "DecomposeGEPExpression and GetUnderlyingObject disagree!");
+ assert(!DL &&
+ "DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
+ // If the max search depth is reached the result is undefined
+ if (GEP2MaxLookupReached || GEP1MaxLookupReached)
+ return MayAlias;
+
// Same offsets.
if (GEP1BaseOffset == GEP2BaseOffset &&
- areVarIndicesEqual(GEP1VariableIndices, GEP2VariableIndices))
+ GEP1VariableIndices == GEP2VariableIndices)
return NoAlias;
GEP1VariableIndices.clear();
}
// exactly, see if the computed offset from the common pointer tells us
// about the relation of the resulting pointer.
const Value *GEP1BasePtr =
- DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
+ DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
+ GEP1MaxLookupReached, DL);
int64_t GEP2BaseOffset;
+ bool GEP2MaxLookupReached;
SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
const Value *GEP2BasePtr =
- DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
+ DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices,
+ GEP2MaxLookupReached, DL);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
- assert(TD == 0 &&
+ assert(!DL &&
"DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
+ // If the max search depth is reached the result is undefined
+ if (GEP2MaxLookupReached || GEP1MaxLookupReached)
+ return MayAlias;
// Subtract the GEP2 pointer from the GEP1 pointer to find out their
// symbolic difference.
if (V1Size == UnknownSize && V2Size == UnknownSize)
return MayAlias;
- AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, 0,
+ AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, nullptr,
V2, V2Size, V2TBAAInfo);
if (R != MustAlias)
// If V2 may alias GEP base pointer, conservatively returns MayAlias.
return R;
const Value *GEP1BasePtr =
- DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
+ DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
+ GEP1MaxLookupReached, DL);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
if (GEP1BasePtr != UnderlyingV1) {
- assert(TD == 0 &&
+ assert(!DL &&
"DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
+ // If the max search depth is reached the result is undefined
+ if (GEP1MaxLookupReached)
+ return MayAlias;
}
// In the two GEP Case, if there is no difference in the offsets of the
return NoAlias;
}
} else {
- if (V1Size != UnknownSize) {
+ // We have the situation where:
+ // + +
+ // | BaseOffset |
+ // ---------------->|
+ // |-->V1Size |-------> V2Size
+ // GEP1 V2
+ // We need to know that V2Size is not unknown, otherwise we might have
+ // stripped a gep with negative index ('gep <ptr>, -1, ...).
+ if (V1Size != UnknownSize && V2Size != UnknownSize) {
if (-(uint64_t)GEP1BaseOffset < V1Size)
return PartialAlias;
return NoAlias;
return NoAlias; // Scalars cannot alias each other
// Figure out what objects these things are pointing to if we can.
- const Value *O1 = GetUnderlyingObject(V1, TD);
- const Value *O2 = GetUnderlyingObject(V2, TD);
+ const Value *O1 = GetUnderlyingObject(V1, DL, MaxLookupSearchDepth);
+ const Value *O2 = GetUnderlyingObject(V2, DL, MaxLookupSearchDepth);
// Null values in the default address space don't point to any object, so they
// don't alias any other pointer.
// If the size of one access is larger than the entire object on the other
// side, then we know such behavior is undefined and can assume no alias.
- if (TD)
- if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD, *TLI)) ||
- (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD, *TLI)))
+ if (DL)
+ if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *DL, *TLI)) ||
+ (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *DL, *TLI)))
return NoAlias;
// Check the cache before climbing up use-def chains. This also terminates
// If both pointers are pointing into the same object and one of them
// accesses is accessing the entire object, then the accesses must
// overlap in some way.
- if (TD && O1 == O2)
- if ((V1Size != UnknownSize && isObjectSize(O1, V1Size, *TD, *TLI)) ||
- (V2Size != UnknownSize && isObjectSize(O2, V2Size, *TD, *TLI)))
+ if (DL && O1 == O2)
+ if ((V1Size != UnknownSize && isObjectSize(O1, V1Size, *DL, *TLI)) ||
+ (V2Size != UnknownSize && isObjectSize(O2, V2Size, *DL, *TLI)))
return AliasCache[Locs] = PartialAlias;
AliasResult Result =
return false;
// Use dominance or loop info if available.
- DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
+ DominatorTreeWrapperPass *DTWP =
+ getAnalysisIfAvailable<DominatorTreeWrapperPass>();
+ DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
LoopInfo *LI = getAnalysisIfAvailable<LoopInfo>();
// Make sure that the visited phis cannot reach the Value. This ensures that
projects / oota-llvm.git / blobdiff