#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
///
/// Note that this looks through extends, so the high bits may not be
/// represented in the result.
-/*static*/ Value *BasicAliasAnalysis::GetLinearExpression(
- Value *V, APInt &Scale, APInt &Offset, ExtensionKind &Extension,
- const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
- DominatorTree *DT) {
+/*static*/ const Value *BasicAAResult::GetLinearExpression(
+ const Value *V, APInt &Scale, APInt &Offset, unsigned &ZExtBits,
+ unsigned &SExtBits, const DataLayout &DL, unsigned Depth,
+ AssumptionCache *AC, DominatorTree *DT, bool &NSW, bool &NUW) {
assert(V->getType()->isIntegerTy() && "Not an integer value");
// Limit our recursion depth.
return V;
}
- if (ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
- // if it's a constant, just convert it to an offset
- // and remove the variable.
- Offset += Const->getValue();
+ if (const ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
+ // if it's a constant, just convert it to an offset and remove the variable.
+ // If we've been called recursively the Offset bit width will be greater
+ // than the constant's (the Offset's always as wide as the outermost call),
+ // so we'll zext here and process any extension in the isa<SExtInst> &
+ // isa<ZExtInst> cases below.
+ Offset += Const->getValue().zextOrSelf(Offset.getBitWidth());
assert(Scale == 0 && "Constant values don't have a scale");
return V;
}
- if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
+ if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
+
+ // If we've been called recursively then Offset and Scale will be wider
+ // that the BOp operands. We'll always zext it here as we'll process sign
+ // extensions below (see the isa<SExtInst> / isa<ZExtInst> cases).
+ APInt RHS = RHSC->getValue().zextOrSelf(Offset.getBitWidth());
+
switch (BOp->getOpcode()) {
default:
- break;
+ // We don't understand this instruction, so we can't decompose it any
+ // further.
+ Scale = 1;
+ Offset = 0;
+ return V;
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(), DL, 0, AC,
- BOp, DT))
- break;
+ BOp, DT)) {
+ Scale = 1;
+ Offset = 0;
+ return V;
+ }
// FALL THROUGH.
case Instruction::Add:
- V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- DL, Depth + 1, AC, DT);
- Offset += RHSC->getValue();
- return V;
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
+ SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
+ Offset += RHS;
+ break;
+ case Instruction::Sub:
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
+ SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
+ Offset -= RHS;
+ break;
case Instruction::Mul:
- V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- DL, Depth + 1, AC, DT);
- Offset *= RHSC->getValue();
- Scale *= RHSC->getValue();
- return V;
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
+ SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
+ Offset *= RHS;
+ Scale *= RHS;
+ break;
case Instruction::Shl:
- V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- DL, Depth + 1, AC, DT);
- Offset <<= RHSC->getValue().getLimitedValue();
- Scale <<= RHSC->getValue().getLimitedValue();
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
+ SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
+ Offset <<= RHS.getLimitedValue();
+ Scale <<= RHS.getLimitedValue();
+ // the semantics of nsw and nuw for left shifts don't match those of
+ // multiplications, so we won't propagate them.
+ NSW = NUW = false;
return V;
}
+
+ if (isa<OverflowingBinaryOperator>(BOp)) {
+ NUW &= BOp->hasNoUnsignedWrap();
+ NSW &= BOp->hasNoSignedWrap();
+ }
+ return V;
}
}
// Since GEP indices are sign extended anyway, we don't care about the high
// bits of a sign or zero extended value - just scales and offsets. The
// extensions have to be consistent though.
- if ((isa<SExtInst>(V) && Extension != EK_ZeroExt) ||
- (isa<ZExtInst>(V) && Extension != EK_SignExt)) {
+ if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
Value *CastOp = cast<CastInst>(V)->getOperand(0);
- unsigned OldWidth = Scale.getBitWidth();
+ unsigned NewWidth = V->getType()->getPrimitiveSizeInBits();
unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
- Scale = Scale.trunc(SmallWidth);
- Offset = Offset.trunc(SmallWidth);
- Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
-
- Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension, DL,
- Depth + 1, AC, DT);
- Scale = Scale.zext(OldWidth);
-
- // We have to sign-extend even if Extension == EK_ZeroExt as we can't
- // decompose a sign extension (i.e. zext(x - 1) != zext(x) - zext(-1)).
- Offset = Offset.sext(OldWidth);
+ unsigned OldZExtBits = ZExtBits, OldSExtBits = SExtBits;
+ const Value *Result =
+ GetLinearExpression(CastOp, Scale, Offset, ZExtBits, SExtBits, DL,
+ Depth + 1, AC, DT, NSW, NUW);
+
+ // zext(zext(%x)) == zext(%x), and similiarly for sext; we'll handle this
+ // by just incrementing the number of bits we've extended by.
+ unsigned ExtendedBy = NewWidth - SmallWidth;
+
+ if (isa<SExtInst>(V) && ZExtBits == 0) {
+ // sext(sext(%x, a), b) == sext(%x, a + b)
+
+ if (NSW) {
+ // We haven't sign-wrapped, so it's valid to decompose sext(%x + c)
+ // into sext(%x) + sext(c). We'll sext the Offset ourselves:
+ unsigned OldWidth = Offset.getBitWidth();
+ Offset = Offset.trunc(SmallWidth).sext(NewWidth).zextOrSelf(OldWidth);
+ } else {
+ // We may have signed-wrapped, so don't decompose sext(%x + c) into
+ // sext(%x) + sext(c)
+ Scale = 1;
+ Offset = 0;
+ Result = CastOp;
+ ZExtBits = OldZExtBits;
+ SExtBits = OldSExtBits;
+ }
+ SExtBits += ExtendedBy;
+ } else {
+ // sext(zext(%x, a), b) = zext(zext(%x, a), b) = zext(%x, a + b)
+
+ if (!NUW) {
+ // We may have unsigned-wrapped, so don't decompose zext(%x + c) into
+ // zext(%x) + zext(c)
+ Scale = 1;
+ Offset = 0;
+ Result = CastOp;
+ ZExtBits = OldZExtBits;
+ SExtBits = OldSExtBits;
+ }
+ ZExtBits += ExtendedBy;
+ }
return Result;
}
/// GetUnderlyingObject and DecomposeGEPExpression must use the same search
/// depth (MaxLookupSearchDepth). When DataLayout not is around, it just looks
/// through pointer casts.
-/*static*/ const Value *BasicAliasAnalysis::DecomposeGEPExpression(
+/*static*/ const Value *BasicAAResult::DecomposeGEPExpression(
const Value *V, int64_t &BaseOffs,
SmallVectorImpl<VariableGEPIndex> &VarIndices, bool &MaxLookupReached,
const DataLayout &DL, AssumptionCache *AC, DominatorTree *DT) {
gep_type_iterator GTI = gep_type_begin(GEPOp);
for (User::const_op_iterator I = GEPOp->op_begin() + 1, E = GEPOp->op_end();
I != E; ++I) {
- Value *Index = *I;
+ const Value *Index = *I;
// Compute the (potentially symbolic) offset in bytes for this index.
if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset.
}
// For an array/pointer, add the element offset, explicitly scaled.
- if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
+ if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero())
continue;
BaseOffs += DL.getTypeAllocSize(*GTI) * CIdx->getSExtValue();
}
uint64_t Scale = DL.getTypeAllocSize(*GTI);
- ExtensionKind Extension = EK_NotExtended;
+ unsigned ZExtBits = 0, SExtBits = 0;
// If the integer type is smaller than the pointer size, it is implicitly
// sign extended to pointer size.
unsigned Width = Index->getType()->getIntegerBitWidth();
- if (DL.getPointerSizeInBits(AS) > Width)
- Extension = EK_SignExt;
+ unsigned PointerSize = DL.getPointerSizeInBits(AS);
+ if (PointerSize > Width)
+ SExtBits += PointerSize - Width;
// 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, DL,
- 0, AC, DT);
+ bool NSW = true, NUW = true;
+ Index = GetLinearExpression(Index, IndexScale, IndexOffset, ZExtBits,
+ SExtBits, DL, 0, AC, DT, NSW, NUW);
// 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.
// A[x][x] -> x*16 + x*4 -> x*20
// This also ensures that 'x' only appears in the index list once.
for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
- if (VarIndices[i].V == Index && VarIndices[i].Extension == Extension) {
+ if (VarIndices[i].V == Index && VarIndices[i].ZExtBits == ZExtBits &&
+ VarIndices[i].SExtBits == SExtBits) {
Scale += VarIndices[i].Scale;
VarIndices.erase(VarIndices.begin() + i);
break;
// Make sure that we have a scale that makes sense for this target's
// pointer size.
- if (unsigned ShiftBits = 64 - DL.getPointerSizeInBits(AS)) {
+ if (unsigned ShiftBits = 64 - PointerSize) {
Scale <<= ShiftBits;
Scale = (int64_t)Scale >> ShiftBits;
}
if (Scale) {
- VariableGEPIndex Entry = {Index, Extension,
+ VariableGEPIndex Entry = {Index, ZExtBits, SExtBits,
static_cast<int64_t>(Scale)};
VarIndices.push_back(Entry);
}
return V;
}
-//===----------------------------------------------------------------------===//
-// BasicAliasAnalysis Pass
-//===----------------------------------------------------------------------===//
-
-// Register the pass...
-char BasicAliasAnalysis::ID = 0;
-INITIALIZE_AG_PASS_BEGIN(BasicAliasAnalysis, AliasAnalysis, "basicaa",
- "Basic Alias Analysis (stateless AA impl)", false,
- true, false)
-INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
-INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
-INITIALIZE_AG_PASS_END(BasicAliasAnalysis, AliasAnalysis, "basicaa",
- "Basic Alias Analysis (stateless AA impl)", false, true,
- false)
-
-ImmutablePass *llvm::createBasicAliasAnalysisPass() {
- return new BasicAliasAnalysis();
-}
-
/// Returns whether the given pointer value points to memory that is local to
/// the function, with global constants being considered local to all
/// functions.
-bool BasicAliasAnalysis::pointsToConstantMemory(const MemoryLocation &Loc,
- bool OrLocal) {
+bool BasicAAResult::pointsToConstantMemory(const MemoryLocation &Loc,
+ bool OrLocal) {
assert(Visited.empty() && "Visited must be cleared after use!");
unsigned MaxLookup = 8;
SmallVector<const Value *, 16> Worklist;
Worklist.push_back(Loc.Ptr);
do {
- const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), *DL);
+ const Value *V = GetUnderlyingObject(Worklist.pop_back_val(), DL);
if (!Visited.insert(V).second) {
Visited.clear();
- return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+ return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
}
// An alloca instruction defines local memory.
// others. GV may even be a declaration, not a definition.
if (!GV->isConstant()) {
Visited.clear();
- return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+ return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
}
continue;
}
// Don't bother inspecting phi nodes with many operands.
if (PN->getNumIncomingValues() > MaxLookup) {
Visited.clear();
- return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+ return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
}
for (Value *IncValue : PN->incoming_values())
Worklist.push_back(IncValue);
// Otherwise be conservative.
Visited.clear();
- return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+ return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
} while (!Worklist.empty() && --MaxLookup);
}
/// Returns the behavior when calling the given call site.
-FunctionModRefBehavior
-BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+FunctionModRefBehavior BasicAAResult::getModRefBehavior(ImmutableCallSite CS) {
if (CS.doesNotAccessMemory())
// Can't do better than this.
return FMRB_DoesNotAccessMemory;
if (CS.onlyAccessesArgMemory())
Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
- // The AliasAnalysis base class has some smarts, lets use them.
- return FunctionModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
+ // The AAResultBase base class has some smarts, lets use them.
+ return FunctionModRefBehavior(AAResultBase::getModRefBehavior(CS) & Min);
}
/// Returns the behavior when calling the given function. For use when the call
/// site is not known.
-FunctionModRefBehavior
-BasicAliasAnalysis::getModRefBehavior(const Function *F) {
+FunctionModRefBehavior BasicAAResult::getModRefBehavior(const Function *F) {
// If the function declares it doesn't access memory, we can't do better.
if (F->doesNotAccessMemory())
return FMRB_DoesNotAccessMemory;
- // For intrinsics, we can check the table.
- if (Intrinsic::ID iid = F->getIntrinsicID()) {
-#define GET_INTRINSIC_MODREF_BEHAVIOR
-#include "llvm/IR/Intrinsics.gen"
-#undef GET_INTRINSIC_MODREF_BEHAVIOR
- }
-
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
// If the function declares it only reads memory, go with that.
if (F->onlyAccessesArgMemory())
Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
- const TargetLibraryInfo &TLI =
- getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
if (isMemsetPattern16(F, TLI))
Min = FMRB_OnlyAccessesArgumentPointees;
// Otherwise be conservative.
- return FunctionModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min);
+ return FunctionModRefBehavior(AAResultBase::getModRefBehavior(F) & Min);
}
-ModRefInfo BasicAliasAnalysis::getArgModRefInfo(ImmutableCallSite CS,
- unsigned ArgIdx) {
+ModRefInfo BasicAAResult::getArgModRefInfo(ImmutableCallSite CS,
+ unsigned ArgIdx) {
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction()))
switch (II->getIntrinsicID()) {
default:
// LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
// whenever possible.
if (CS.getCalledFunction() &&
- isMemsetPattern16(CS.getCalledFunction(), *TLI)) {
+ isMemsetPattern16(CS.getCalledFunction(), TLI)) {
assert((ArgIdx == 0 || ArgIdx == 1) &&
"Invalid argument index for memset_pattern16");
return ArgIdx ? MRI_Ref : MRI_Mod;
}
// FIXME: Handle memset_pattern4 and memset_pattern8 also.
- return AliasAnalysis::getArgModRefInfo(CS, ArgIdx);
+ return AAResultBase::getArgModRefInfo(CS, ArgIdx);
}
static bool isAssumeIntrinsic(ImmutableCallSite CS) {
return false;
}
-bool BasicAliasAnalysis::doInitialization(Module &M) {
- InitializeAliasAnalysis(this, &M.getDataLayout());
- return true;
-}
-
/// Checks to see if the specified callsite can clobber the specified memory
/// object.
///
/// Since we only look at local properties of this function, we really can't
/// say much about this query. We do, however, use simple "address taken"
/// analysis on local objects.
-ModRefInfo BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
- const MemoryLocation &Loc) {
+ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS,
+ const MemoryLocation &Loc) {
assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
"AliasAnalysis query involving multiple functions!");
- const Value *Object = GetUnderlyingObject(Loc.Ptr, *DL);
+ 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.
// is impossible to alias the pointer we're checking. If not, we have to
// assume that the call could touch the pointer, even though it doesn't
// escape.
- if (!isNoAlias(MemoryLocation(*CI), MemoryLocation(Object))) {
+ AliasResult AR =
+ getBestAAResults().alias(MemoryLocation(*CI), MemoryLocation(Object));
+ if (AR) {
PassedAsArg = true;
break;
}
if (isAssumeIntrinsic(CS))
return MRI_NoModRef;
- // The AliasAnalysis base class has some smarts, lets use them.
- return AliasAnalysis::getModRefInfo(CS, Loc);
+ // The AAResultBase base class has some smarts, lets use them.
+ return AAResultBase::getModRefInfo(CS, Loc);
}
-ModRefInfo BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
- ImmutableCallSite CS2) {
+ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
// While the assume intrinsic is marked as arbitrarily writing so that
// proper control dependencies will be maintained, it never aliases any
// particular memory location.
if (isAssumeIntrinsic(CS1) || isAssumeIntrinsic(CS2))
return MRI_NoModRef;
- // The AliasAnalysis base class has some smarts, lets use them.
- return AliasAnalysis::getModRefInfo(CS1, CS2);
+ // The AAResultBase base class has some smarts, lets use them.
+ return AAResultBase::getModRefInfo(CS1, CS2);
}
/// Provide ad-hoc rules to disambiguate accesses through two GEP operators,
/// We know that V1 is a GEP, but we don't know anything about V2.
/// UnderlyingV1 is GetUnderlyingObject(GEP1, DL), UnderlyingV2 is the same for
/// V2.
-AliasResult BasicAliasAnalysis::aliasGEP(
- const GEPOperator *GEP1, uint64_t V1Size, const AAMDNodes &V1AAInfo,
- const Value *V2, uint64_t V2Size, const AAMDNodes &V2AAInfo,
- const Value *UnderlyingV1, const Value *UnderlyingV2) {
+AliasResult BasicAAResult::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
+ const AAMDNodes &V1AAInfo, const Value *V2,
+ uint64_t V2Size, const AAMDNodes &V2AAInfo,
+ const Value *UnderlyingV1,
+ const Value *UnderlyingV2) {
int64_t GEP1BaseOffset;
bool GEP1MaxLookupReached;
SmallVector<VariableGEPIndex, 4> GEP1VariableIndices;
- // We have to get two AssumptionCaches here because GEP1 and V2 may be from
- // different functions.
- // FIXME: This really doesn't make any sense. We get a dominator tree below
- // that can only refer to a single function. But this function (aliasGEP) is
- // a method on an immutable pass that can be called when there *isn't*
- // a single function. The old pass management layer makes this "work", but
- // this isn't really a clean solution.
- AssumptionCacheTracker &ACT = getAnalysis<AssumptionCacheTracker>();
- AssumptionCache *AC1 = nullptr, *AC2 = nullptr;
- if (auto *GEP1I = dyn_cast<Instruction>(GEP1))
- AC1 = &ACT.getAssumptionCache(
- const_cast<Function &>(*GEP1I->getParent()->getParent()));
- if (auto *I2 = dyn_cast<Instruction>(V2))
- AC2 = &ACT.getAssumptionCache(
- const_cast<Function &>(*I2->getParent()->getParent()));
-
- DominatorTreeWrapperPass *DTWP =
- getAnalysisIfAvailable<DominatorTreeWrapperPass>();
- DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
-
// If we have two gep instructions with must-alias or not-alias'ing base
// pointers, figure out if the indexes to the GEP tell us anything about the
// derived pointer.
SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
const Value *GEP2BasePtr =
DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices,
- GEP2MaxLookupReached, *DL, AC2, DT);
+ GEP2MaxLookupReached, DL, &AC, DT);
const Value *GEP1BasePtr =
DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
- GEP1MaxLookupReached, *DL, AC1, DT);
+ GEP1MaxLookupReached, DL, &AC, DT);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
+ // FIXME: They always have a DataLayout so this should become an
+ // assert.
if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
- assert(!DL &&
- "DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
// If the max search depth is reached the result is undefined
// about the relation of the resulting pointer.
const Value *GEP1BasePtr =
DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
- GEP1MaxLookupReached, *DL, AC1, DT);
+ GEP1MaxLookupReached, DL, &AC, DT);
int64_t GEP2BaseOffset;
bool GEP2MaxLookupReached;
SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
const Value *GEP2BasePtr =
DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices,
- GEP2MaxLookupReached, *DL, AC2, DT);
+ GEP2MaxLookupReached, DL, &AC, DT);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
+ // FIXME: They always have a DataLayout so this should become an assert.
if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
- assert(!DL && "DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
// If we know the two GEPs are based off of the exact same pointer (and not
// just the same underlying object), see if that tells us anything about
// the resulting pointers.
- if (DL && GEP1->getPointerOperand() == GEP2->getPointerOperand()) {
- AliasResult R = aliasSameBasePointerGEPs(GEP1, V1Size, GEP2, V2Size, *DL);
+ if (GEP1->getPointerOperand() == GEP2->getPointerOperand()) {
+ AliasResult R = aliasSameBasePointerGEPs(GEP1, V1Size, GEP2, V2Size, DL);
// If we couldn't find anything interesting, don't abandon just yet.
if (R != MayAlias)
return R;
const Value *GEP1BasePtr =
DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices,
- GEP1MaxLookupReached, *DL, AC1, DT);
+ GEP1MaxLookupReached, DL, &AC, DT);
// DecomposeGEPExpression and GetUnderlyingObject should return the
// same result except when DecomposeGEPExpression has no DataLayout.
+ // FIXME: They always have a DataLayout so this should become an assert.
if (GEP1BasePtr != UnderlyingV1) {
- assert(!DL && "DecomposeGEPExpression and GetUnderlyingObject disagree!");
return MayAlias;
}
// If the max search depth is reached the result is undefined
const Value *V = GEP1VariableIndices[i].V;
bool SignKnownZero, SignKnownOne;
- ComputeSignBit(const_cast<Value *>(V), SignKnownZero, SignKnownOne, *DL,
- 0, AC1, nullptr, DT);
+ ComputeSignBit(const_cast<Value *>(V), SignKnownZero, SignKnownOne, DL,
+ 0, &AC, nullptr, DT);
// Zero-extension widens the variable, and so forces the sign
// bit to zero.
- bool IsZExt = GEP1VariableIndices[i].Extension == EK_ZeroExt;
+ bool IsZExt = GEP1VariableIndices[i].ZExtBits > 0 || isa<ZExtInst>(V);
SignKnownZero |= IsZExt;
SignKnownOne &= !IsZExt;
// don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t)GEP1BaseOffset)
return NoAlias;
+
+ if (constantOffsetHeuristic(GEP1VariableIndices, V1Size, V2Size,
+ GEP1BaseOffset, &AC, DT))
+ return NoAlias;
}
// Statically, we can see that the base objects are the same, but the
/// Provides a bunch of ad-hoc rules to disambiguate a Select instruction
/// against another.
-AliasResult BasicAliasAnalysis::aliasSelect(const SelectInst *SI,
- uint64_t SISize,
- const AAMDNodes &SIAAInfo,
- const Value *V2, uint64_t V2Size,
- const AAMDNodes &V2AAInfo) {
+AliasResult BasicAAResult::aliasSelect(const SelectInst *SI, uint64_t SISize,
+ const AAMDNodes &SIAAInfo,
+ const Value *V2, uint64_t V2Size,
+ const AAMDNodes &V2AAInfo) {
// If the values are Selects with the same condition, we can do a more precise
// check: just check for aliases between the values on corresponding arms.
if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2))
/// Provide a bunch of ad-hoc rules to disambiguate a PHI instruction against
/// another.
-AliasResult BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
- const AAMDNodes &PNAAInfo,
- const Value *V2, uint64_t V2Size,
- const AAMDNodes &V2AAInfo) {
+AliasResult BasicAAResult::aliasPHI(const PHINode *PN, uint64_t PNSize,
+ const AAMDNodes &PNAAInfo, const Value *V2,
+ uint64_t V2Size,
+ const AAMDNodes &V2AAInfo) {
// Track phi nodes we have visited. We use this information when we determine
// value equivalence.
VisitedPhiBBs.insert(PN->getParent());
/// Provideis a bunch of ad-hoc rules to disambiguate in common cases, such as
/// array references.
-AliasResult BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size,
- AAMDNodes V1AAInfo, const Value *V2,
- uint64_t V2Size,
- AAMDNodes V2AAInfo) {
+AliasResult BasicAAResult::aliasCheck(const Value *V1, uint64_t V1Size,
+ AAMDNodes V1AAInfo, const Value *V2,
+ uint64_t V2Size, AAMDNodes V2AAInfo) {
// If either of the memory references is empty, it doesn't matter what the
// pointer values are.
if (V1Size == 0 || V2Size == 0)
return NoAlias; // Scalars cannot alias each other
// Figure out what objects these things are pointing to if we can.
- const Value *O1 = GetUnderlyingObject(V1, *DL, MaxLookupSearchDepth);
- const Value *O2 = GetUnderlyingObject(V2, *DL, MaxLookupSearchDepth);
+ 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 (DL)
- if ((V1Size != MemoryLocation::UnknownSize &&
- isObjectSmallerThan(O2, V1Size, *DL, *TLI)) ||
- (V2Size != MemoryLocation::UnknownSize &&
- isObjectSmallerThan(O1, V2Size, *DL, *TLI)))
- return NoAlias;
+ if ((V1Size != MemoryLocation::UnknownSize &&
+ isObjectSmallerThan(O2, V1Size, DL, TLI)) ||
+ (V2Size != MemoryLocation::UnknownSize &&
+ isObjectSmallerThan(O1, V2Size, DL, TLI)))
+ return NoAlias;
// Check the cache before climbing up use-def chains. This also terminates
// otherwise infinitely recursive queries.
// 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 (DL && O1 == O2)
+ if (O1 == O2)
if ((V1Size != MemoryLocation::UnknownSize &&
- isObjectSize(O1, V1Size, *DL, *TLI)) ||
+ isObjectSize(O1, V1Size, DL, TLI)) ||
(V2Size != MemoryLocation::UnknownSize &&
- isObjectSize(O2, V2Size, *DL, *TLI)))
+ isObjectSize(O2, V2Size, DL, TLI)))
return AliasCache[Locs] = PartialAlias;
- AliasResult Result =
- AliasAnalysis::alias(MemoryLocation(V1, V1Size, V1AAInfo),
- MemoryLocation(V2, V2Size, V2AAInfo));
+ // Recurse back into the best AA results we have, potentially with refined
+ // memory locations. We have already ensured that BasicAA has a MayAlias
+ // cache result for these, so any recursion back into BasicAA won't loop.
+ AliasResult Result = getBestAAResults().alias(Locs.first, Locs.second);
return AliasCache[Locs] = Result;
}
/// visited phi nodes an making sure that the phis cannot reach the value. We
/// have to do this because we are looking through phi nodes (That is we say
/// noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
-bool BasicAliasAnalysis::isValueEqualInPotentialCycles(const Value *V,
- const Value *V2) {
+bool BasicAAResult::isValueEqualInPotentialCycles(const Value *V,
+ const Value *V2) {
if (V != V2)
return false;
if (VisitedPhiBBs.size() > MaxNumPhiBBsValueReachabilityCheck)
return false;
- // Use dominance or loop info if available.
- DominatorTreeWrapperPass *DTWP =
- getAnalysisIfAvailable<DominatorTreeWrapperPass>();
- DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
- auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
- LoopInfo *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
-
// Make sure that the visited phis cannot reach the Value. This ensures that
// the Values cannot come from different iterations of a potential cycle the
// phi nodes could be involved in.
///
/// Dest and Src are the variable indices from two decomposed GetElementPtr
/// instructions GEP1 and GEP2 which have common base pointers.
-void BasicAliasAnalysis::GetIndexDifference(
+void BasicAAResult::GetIndexDifference(
SmallVectorImpl<VariableGEPIndex> &Dest,
const SmallVectorImpl<VariableGEPIndex> &Src) {
if (Src.empty())
for (unsigned i = 0, e = Src.size(); i != e; ++i) {
const Value *V = Src[i].V;
- ExtensionKind Extension = Src[i].Extension;
+ unsigned ZExtBits = Src[i].ZExtBits, SExtBits = Src[i].SExtBits;
int64_t Scale = Src[i].Scale;
// Find V in Dest. This is N^2, but pointer indices almost never have more
// than a few variable indexes.
for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
if (!isValueEqualInPotentialCycles(Dest[j].V, V) ||
- Dest[j].Extension != Extension)
+ Dest[j].ZExtBits != ZExtBits || Dest[j].SExtBits != SExtBits)
continue;
// If we found it, subtract off Scale V's from the entry in Dest. If it
// If we didn't consume this entry, add it to the end of the Dest list.
if (Scale) {
- VariableGEPIndex Entry = {V, Extension, -Scale};
+ VariableGEPIndex Entry = {V, ZExtBits, SExtBits, -Scale};
Dest.push_back(Entry);
}
}
}
+
+bool BasicAAResult::constantOffsetHeuristic(
+ const SmallVectorImpl<VariableGEPIndex> &VarIndices, uint64_t V1Size,
+ uint64_t V2Size, int64_t BaseOffset, AssumptionCache *AC,
+ DominatorTree *DT) {
+ if (VarIndices.size() != 2 || V1Size == MemoryLocation::UnknownSize ||
+ V2Size == MemoryLocation::UnknownSize)
+ return false;
+
+ const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
+
+ if (Var0.ZExtBits != Var1.ZExtBits || Var0.SExtBits != Var1.SExtBits ||
+ Var0.Scale != -Var1.Scale)
+ return false;
+
+ unsigned Width = Var1.V->getType()->getIntegerBitWidth();
+
+ // We'll strip off the Extensions of Var0 and Var1 and do another round
+ // of GetLinearExpression decomposition. In the example above, if Var0
+ // is zext(%x + 1) we should get V1 == %x and V1Offset == 1.
+
+ APInt V0Scale(Width, 0), V0Offset(Width, 0), V1Scale(Width, 0),
+ V1Offset(Width, 0);
+ bool NSW = true, NUW = true;
+ unsigned V0ZExtBits = 0, V0SExtBits = 0, V1ZExtBits = 0, V1SExtBits = 0;
+ const Value *V0 = GetLinearExpression(Var0.V, V0Scale, V0Offset, V0ZExtBits,
+ V0SExtBits, DL, 0, AC, DT, NSW, NUW);
+ NSW = true, NUW = true;
+ const Value *V1 = GetLinearExpression(Var1.V, V1Scale, V1Offset, V1ZExtBits,
+ V1SExtBits, DL, 0, AC, DT, NSW, NUW);
+
+ if (V0Scale != V1Scale || V0ZExtBits != V1ZExtBits ||
+ V0SExtBits != V1SExtBits || !isValueEqualInPotentialCycles(V0, V1))
+ return false;
+
+ // We have a hit - Var0 and Var1 only differ by a constant offset!
+
+ // If we've been sext'ed then zext'd the maximum difference between Var0 and
+ // Var1 is possible to calculate, but we're just interested in the absolute
+ // minumum difference between the two. The minimum distance may occur due to
+ // wrapping; consider "add i3 %i, 5": if %i == 7 then 7 + 5 mod 8 == 4, and so
+ // the minimum distance between %i and %i + 5 is 3.
+ APInt MinDiff = V0Offset - V1Offset,
+ Wrapped = APInt::getMaxValue(Width) - MinDiff + APInt(Width, 1);
+ MinDiff = APIntOps::umin(MinDiff, Wrapped);
+ uint64_t MinDiffBytes = MinDiff.getZExtValue() * std::abs(Var0.Scale);
+
+ // We can't definitely say whether GEP1 is before or after V2 due to wrapping
+ // arithmetic (i.e. for some values of GEP1 and V2 GEP1 < V2, and for other
+ // values GEP1 > V2). We'll therefore only declare NoAlias if both V1Size and
+ // V2Size can fit in the MinDiffBytes gap.
+ return V1Size + std::abs(BaseOffset) <= MinDiffBytes &&
+ V2Size + std::abs(BaseOffset) <= MinDiffBytes;
+}
+
+//===----------------------------------------------------------------------===//
+// BasicAliasAnalysis Pass
+//===----------------------------------------------------------------------===//
+
+char BasicAA::PassID;
+
+BasicAAResult BasicAA::run(Function &F, AnalysisManager<Function> *AM) {
+ return BasicAAResult(F.getParent()->getDataLayout(),
+ AM->getResult<TargetLibraryAnalysis>(F),
+ AM->getResult<AssumptionAnalysis>(F),
+ AM->getCachedResult<DominatorTreeAnalysis>(F),
+ AM->getCachedResult<LoopAnalysis>(F));
+}
+
+char BasicAAWrapperPass::ID = 0;
+void BasicAAWrapperPass::anchor() {}
+
+INITIALIZE_PASS_BEGIN(BasicAAWrapperPass, "basicaa",
+ "Basic Alias Analysis (stateless AA impl)", true, true)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(BasicAAWrapperPass, "basicaa",
+ "Basic Alias Analysis (stateless AA impl)", true, true)
+
+FunctionPass *llvm::createBasicAAWrapperPass() {
+ return new BasicAAWrapperPass();
+}
+
+bool BasicAAWrapperPass::runOnFunction(Function &F) {
+ auto &ACT = getAnalysis<AssumptionCacheTracker>();
+ auto &TLIWP = getAnalysis<TargetLibraryInfoWrapperPass>();
+ auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
+ auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
+
+ Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), TLIWP.getTLI(),
+ ACT.getAssumptionCache(F),
+ DTWP ? &DTWP->getDomTree() : nullptr,
+ LIWP ? &LIWP->getLoopInfo() : nullptr));
+
+ return false;
+}
+
+void BasicAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+}
+
+BasicAAResult llvm::createLegacyPMBasicAAResult(Pass &P, Function &F) {
+ return BasicAAResult(
+ F.getParent()->getDataLayout(),
+ P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
+ P.getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));
+}