#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
-#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include <algorithm>
return false;
}
+/// isEscapeSource - Return true if the pointer is one which would have
+/// been considered an escape by isNonEscapingLocalObject.
+static bool isEscapeSource(const Value *V) {
+ if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
+ return true;
+
+ // The load case works because isNonEscapingLocalObject considers all
+ // stores to be escapes (it passes true for the StoreCaptures argument
+ // to PointerMayBeCaptured).
+ if (isa<LoadInst>(V))
+ return true;
+
+ return false;
+}
/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
} else if (const CallInst* CI = extractMallocCall(V)) {
if (!isArrayMalloc(V, &TD))
// The size is the argument to the malloc call.
- if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getOperand(1)))
+ if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getArgOperand(0)))
return (C->getZExtValue() < Size);
return false;
} else if (const Argument *A = dyn_cast<Argument>(V)) {
///
struct NoAA : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
- NoAA() : ImmutablePass(&ID) {}
- explicit NoAA(void *PID) : ImmutablePass(PID) { }
+ NoAA() : ImmutablePass(ID) {}
+ explicit NoAA(char &PID) : ImmutablePass(PID) { }
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
}
return MayAlias;
}
- virtual void getArgumentAccesses(Function *F, CallSite CS,
- std::vector<PointerAccessInfo> &Info) {
- llvm_unreachable("This method may not be called on this function!");
+ virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
+ return UnknownModRefBehavior;
+ }
+ virtual ModRefBehavior getModRefBehavior(const Function *F) {
+ return UnknownModRefBehavior;
}
virtual bool pointsToConstantMemory(const Value *P) { return false; }
- virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size) {
return ModRef;
}
- virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
return ModRef;
}
+ virtual DependenceResult getDependence(const Instruction *First,
+ const Value *FirstPHITranslatedAddr,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ const Value *SecondPHITranslatedAddr,
+ DependenceQueryFlags SecondFlags) {
+ return Unknown;
+ }
+
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
+
+ /// 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) {
+ if (ID == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
};
} // End of anonymous namespace
// Register this pass...
char NoAA::ID = 0;
-static RegisterPass<NoAA>
-U("no-aa", "No Alias Analysis (always returns 'may' alias)", true, true);
-
-// Declare that we implement the AliasAnalysis interface
-static RegisterAnalysisGroup<AliasAnalysis> V(U);
+INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
+ "No Alias Analysis (always returns 'may' alias)",
+ true, true, false);
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
//===----------------------------------------------------------------------===//
-// BasicAA Pass
+// GetElementPtr Instruction Decomposition and Analysis
//===----------------------------------------------------------------------===//
namespace {
- /// BasicAliasAnalysis - This is the default alias analysis implementation.
- /// Because it doesn't chain to a previous alias analysis (like -no-aa), it
- /// derives from the NoAA class.
- struct BasicAliasAnalysis : public NoAA {
- static char ID; // Class identification, replacement for typeinfo
- BasicAliasAnalysis() : NoAA(&ID) {}
- AliasResult alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- assert(VisitedPHIs.empty() && "VisitedPHIs must be cleared after use!");
- AliasResult Alias = aliasCheck(V1, V1Size, V2, V2Size);
- VisitedPHIs.clear();
- return Alias;
- }
-
- ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
- ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
-
- /// pointsToConstantMemory - Chase pointers until we find a (constant
- /// global) or not.
- bool pointsToConstantMemory(const Value *P);
-
- private:
- // VisitedPHIs - Track PHI nodes visited by a aliasCheck() call.
- SmallPtrSet<const Value*, 16> VisitedPHIs;
-
- // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
- // instruction against another.
- AliasResult aliasGEP(const GEPOperator *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size,
- const Value *UnderlyingV1, const Value *UnderlyingV2);
-
- // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI
- // instruction against another.
- AliasResult aliasPHI(const PHINode *PN, unsigned PNSize,
- const Value *V2, unsigned V2Size);
-
- /// aliasSelect - Disambiguate a Select instruction against another value.
- AliasResult aliasSelect(const SelectInst *SI, unsigned SISize,
- const Value *V2, unsigned V2Size);
-
- AliasResult aliasCheck(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size);
+ enum ExtensionKind {
+ EK_NotExtended,
+ EK_SignExt,
+ EK_ZeroExt
};
-} // End of anonymous namespace
-
-// Register this pass...
-char BasicAliasAnalysis::ID = 0;
-static RegisterPass<BasicAliasAnalysis>
-X("basicaa", "Basic Alias Analysis (default AA impl)", false, true);
-
-// Declare that we implement the AliasAnalysis interface
-static RegisterAnalysisGroup<AliasAnalysis, true> Y(X);
-
-ImmutablePass *llvm::createBasicAliasAnalysisPass() {
- return new BasicAliasAnalysis();
-}
-
-
-/// pointsToConstantMemory - Chase pointers until we find a (constant
-/// global) or not.
-bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
- if (const GlobalVariable *GV =
- dyn_cast<GlobalVariable>(P->getUnderlyingObject()))
- // Note: this doesn't require GV to be "ODR" because it isn't legal for a
- // global to be marked constant in some modules and non-constant in others.
- // GV may even be a declaration, not a definition.
- return GV->isConstant();
- return false;
-}
-
-
-/// getModRefInfo - Check 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.
-AliasAnalysis::ModRefResult
-BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- const Value *Object = P->getUnderlyingObject();
-
- // If this is a tail call and P points to a stack location, we know that
- // the tail call cannot access or modify the local stack.
- // We cannot exclude byval arguments here; these belong to the caller of
- // the current function not to the current function, and a tail callee
- // may reference them.
- if (isa<AllocaInst>(Object))
- if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
- if (CI->isTailCall())
- return NoModRef;
- // If the pointer is to a locally allocated object that does not escape,
- // then the call can not mod/ref the pointer unless the call takes the pointer
- // as an argument, and itself doesn't capture it.
- if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
- isNonEscapingLocalObject(Object)) {
- bool PassedAsArg = false;
- unsigned ArgNo = 0;
- for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
- CI != CE; ++CI, ++ArgNo) {
- // Only look at the no-capture pointer arguments.
- if (!isa<PointerType>((*CI)->getType()) ||
- !CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))
- continue;
-
- // If this is a no-capture pointer argument, see if we can tell that it
- // 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(cast<Value>(CI), ~0U, P, ~0U)) {
- PassedAsArg = true;
- break;
- }
- }
-
- if (!PassedAsArg)
- return NoModRef;
- }
-
- // Finally, handle specific knowledge of intrinsics.
- IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
- if (II == 0)
- return AliasAnalysis::getModRefInfo(CS, P, Size);
-
- switch (II->getIntrinsicID()) {
- default: break;
- case Intrinsic::memcpy:
- case Intrinsic::memmove: {
- unsigned Len = ~0U;
- if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3)))
- Len = LenCI->getZExtValue();
- Value *Dest = II->getOperand(1);
- Value *Src = II->getOperand(2);
- if (isNoAlias(Dest, Len, P, Size)) {
- if (isNoAlias(Src, Len, P, Size))
- return NoModRef;
- return Ref;
- }
- break;
- }
- case Intrinsic::memset:
- // Since memset is 'accesses arguments' only, the AliasAnalysis base class
- // will handle it for the variable length case.
- if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3))) {
- unsigned Len = LenCI->getZExtValue();
- Value *Dest = II->getOperand(1);
- if (isNoAlias(Dest, Len, P, Size))
- return NoModRef;
- }
- break;
- case Intrinsic::atomic_cmp_swap:
- case Intrinsic::atomic_swap:
- case Intrinsic::atomic_load_add:
- case Intrinsic::atomic_load_sub:
- case Intrinsic::atomic_load_and:
- case Intrinsic::atomic_load_nand:
- case Intrinsic::atomic_load_or:
- case Intrinsic::atomic_load_xor:
- case Intrinsic::atomic_load_max:
- case Intrinsic::atomic_load_min:
- case Intrinsic::atomic_load_umax:
- case Intrinsic::atomic_load_umin:
- if (TD) {
- Value *Op1 = II->getOperand(1);
- unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
- if (isNoAlias(Op1, Op1Size, P, Size))
- return NoModRef;
- }
- break;
- case Intrinsic::lifetime_start:
- case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start: {
- unsigned PtrSize = cast<ConstantInt>(II->getOperand(1))->getZExtValue();
- if (isNoAlias(II->getOperand(2), PtrSize, P, Size))
- return NoModRef;
- break;
- }
- case Intrinsic::invariant_end: {
- unsigned PtrSize = cast<ConstantInt>(II->getOperand(2))->getZExtValue();
- if (isNoAlias(II->getOperand(3), PtrSize, P, Size))
- return NoModRef;
- break;
- }
- }
-
- // The AliasAnalysis base class has some smarts, lets use them.
- return AliasAnalysis::getModRefInfo(CS, P, Size);
+ struct VariableGEPIndex {
+ const Value *V;
+ ExtensionKind Extension;
+ int64_t Scale;
+ };
}
-AliasAnalysis::ModRefResult
-BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
- // If CS1 or CS2 are readnone, they don't interact.
- ModRefBehavior CS1B = AliasAnalysis::getModRefBehavior(CS1);
- if (CS1B == DoesNotAccessMemory) return NoModRef;
-
- ModRefBehavior CS2B = AliasAnalysis::getModRefBehavior(CS2);
- if (CS2B == DoesNotAccessMemory) return NoModRef;
-
- // If they both only read from memory, just return ref.
- if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
- return Ref;
-
- // Otherwise, fall back to NoAA (mod+ref).
- return NoAA::getModRefInfo(CS1, CS2);
-}
-
/// GetLinearExpression - Analyze the specified value as a linear expression:
-/// "A*V + B". Return the scale and offset values as APInts and return V as a
-/// Value*. The incoming Value is known to be a scalar integer.
+/// "A*V + B", where A and B are constant integers. Return the scale and offset
+/// values as APInts and return V as a Value*, and return whether we looked
+/// through any sign or zero extends. The incoming Value is known to have
+/// IntegerType and it may already be sign or zero extended.
+///
+/// Note that this looks through extends, so the high bits may not be
+/// represented in the result.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
- const TargetData *TD) {
- assert(isa<IntegerType>(V->getType()) && "Not an integer value");
+ ExtensionKind &Extension,
+ const TargetData &TD, unsigned Depth) {
+ assert(V->getType()->isIntegerTy() && "Not an integer value");
+
+ // Limit our recursion depth.
+ if (Depth == 6) {
+ Scale = 1;
+ Offset = 0;
+ return V;
+ }
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
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(), &TD))
break;
// FALL THROUGH.
case Instruction::Add:
- V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
+ TD, Depth+1);
Offset += RHSC->getValue();
return V;
- // TODO: SHL, MUL, OR.
+ case Instruction::Mul:
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
+ TD, Depth+1);
+ Offset *= RHSC->getValue();
+ Scale *= RHSC->getValue();
+ return V;
+ case Instruction::Shl:
+ V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
+ TD, Depth+1);
+ Offset <<= RHSC->getValue().getLimitedValue();
+ Scale <<= RHSC->getValue().getLimitedValue();
+ 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)) {
+ Value *CastOp = cast<CastInst>(V)->getOperand(0);
+ unsigned OldWidth = Scale.getBitWidth();
+ unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
+ Scale.trunc(SmallWidth);
+ Offset.trunc(SmallWidth);
+ Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
+
+ Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension,
+ TD, Depth+1);
+ Scale.zext(OldWidth);
+ Offset.zext(OldWidth);
+
+ return Result;
+ }
+
Scale = 1;
Offset = 0;
return V;
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
///
+/// The scaled symbolic offsets (represented by pairs of a Value* and a scale in
+/// the VarIndices vector) are Value*'s that are known to be scaled by the
+/// specified amount, but which may have other unrepresented high bits. As such,
+/// the gep cannot necessarily be reconstructed from its decomposed form.
+///
/// When TargetData is around, this function is capable of analyzing everything
/// that Value::getUnderlyingObject() can look through. When not, it just looks
/// through pointer casts.
///
-/// FIXME: Move this out to ValueTracking.cpp
-///
-static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
- SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
- const TargetData *TD) {
- // FIXME: Should limit depth like getUnderlyingObject?
+static const Value *
+DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
+ SmallVectorImpl<VariableGEPIndex> &VarIndices,
+ const TargetData *TD) {
+ // Limit recursion depth to limit compile time in crazy cases.
+ unsigned MaxLookup = 6;
+
BaseOffs = 0;
- while (1) {
+ do {
// See if this is a bitcast or GEP.
const Operator *Op = dyn_cast<Operator>(V);
if (Op == 0) {
// Don't attempt to analyze GEPs over unsized objects.
if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
- ->getElementType()->isSized())
+ ->getElementType()->isSized())
return V;
-
+
// If we are lacking TargetData information, we can't compute the offets of
// elements computed by GEPs. However, we can handle bitcast equivalent
// GEPs.
- if (!TD) {
+ if (TD == 0) {
if (!GEPOp->hasAllZeroIndices())
return V;
V = GEPOp->getOperand(0);
// Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
gep_type_iterator GTI = gep_type_begin(GEPOp);
- for (User::const_op_iterator I = next(GEPOp->op_begin()),
+ for (User::const_op_iterator I = GEPOp->op_begin()+1,
E = GEPOp->op_end(); I != E; ++I) {
Value *Index = *I;
// Compute the (potentially symbolic) offset in bytes for this index.
continue;
}
- // TODO: Could handle linear expressions here like A[X+1], also A[X*4|1].
uint64_t Scale = TD->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 = cast<IntegerType>(Index->getType())->getBitWidth();
+ if (TD->getPointerSizeInBits() > 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, TD);
+ Index = GetLinearExpression(Index, IndexScale, IndexOffset, Extension,
+ *TD, 0);
- Scale *= IndexScale.getZExtValue();
+ // 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.
BaseOffs += IndexOffset.getZExtValue()*Scale;
+ Scale *= IndexScale.getZExtValue();
// If we already had an occurrance of this index variable, merge this
// 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].first == Index) {
- Scale += VarIndices[i].second;
+ if (VarIndices[i].V == Index &&
+ VarIndices[i].Extension == Extension) {
+ Scale += VarIndices[i].Scale;
VarIndices.erase(VarIndices.begin()+i);
break;
}
Scale >>= ShiftBits;
}
- if (Scale)
- VarIndices.push_back(std::make_pair(Index, Scale));
+ if (Scale) {
+ VariableGEPIndex Entry = {Index, Extension, Scale};
+ VarIndices.push_back(Entry);
+ }
}
// Analyze the base pointer next.
V = GEPOp->getOperand(0);
- }
+ } while (--MaxLookup);
+
+ // If the chain of expressions is too deep, just return early.
+ return V;
}
-/// GetIndiceDifference - Dest and Src are the variable indices from two
+/// GetIndexDifference - Dest and Src are the variable indices from two
/// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
/// difference between the two pointers.
-static void GetIndiceDifference(
- SmallVectorImpl<std::pair<const Value*, int64_t> > &Dest,
- const SmallVectorImpl<std::pair<const Value*, int64_t> > &Src) {
+static void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
+ const SmallVectorImpl<VariableGEPIndex> &Src) {
if (Src.empty()) return;
for (unsigned i = 0, e = Src.size(); i != e; ++i) {
- const Value *V = Src[i].first;
- int64_t Scale = Src[i].second;
+ const Value *V = Src[i].V;
+ ExtensionKind Extension = Src[i].Extension;
+ 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 (Dest[j].first != V) continue;
+ if (Dest[j].V != V || Dest[j].Extension != Extension) continue;
// If we found it, subtract off Scale V's from the entry in Dest. If it
// goes to zero, remove the entry.
- if (Dest[j].second != Scale)
- Dest[j].second -= Scale;
+ if (Dest[j].Scale != Scale)
+ Dest[j].Scale -= Scale;
else
Dest.erase(Dest.begin()+j);
Scale = 0;
}
// If we didn't consume this entry, add it to the end of the Dest list.
- if (Scale)
- Dest.push_back(std::make_pair(V, -Scale));
+ if (Scale) {
+ VariableGEPIndex Entry = { V, Extension, -Scale };
+ Dest.push_back(Entry);
+ }
+ }
+}
+
+//===----------------------------------------------------------------------===//
+// BasicAliasAnalysis Pass
+//===----------------------------------------------------------------------===//
+
+#ifndef NDEBUG
+static const Function *getParent(const Value *V) {
+ if (const Instruction *inst = dyn_cast<Instruction>(V))
+ return inst->getParent()->getParent();
+
+ if (const Argument *arg = dyn_cast<Argument>(V))
+ return arg->getParent();
+
+ return NULL;
+}
+
+static bool notDifferentParent(const Value *O1, const Value *O2) {
+
+ const Function *F1 = getParent(O1);
+ const Function *F2 = getParent(O2);
+
+ return !F1 || !F2 || F1 == F2;
+}
+#endif
+
+namespace {
+ /// BasicAliasAnalysis - This is the default alias analysis implementation.
+ /// Because it doesn't chain to a previous alias analysis (like -no-aa), it
+ /// derives from the NoAA class.
+ struct BasicAliasAnalysis : public NoAA {
+ static char ID; // Class identification, replacement for typeinfo
+ BasicAliasAnalysis() : NoAA(ID) {}
+
+ virtual AliasResult alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ assert(Visited.empty() && "Visited must be cleared after use!");
+ assert(notDifferentParent(V1, V2) &&
+ "BasicAliasAnalysis doesn't support interprocedural queries.");
+ AliasResult Alias = aliasCheck(V1, V1Size, V2, V2Size);
+ Visited.clear();
+ return Alias;
+ }
+
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size);
+
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
+ // 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 Value *P);
+
+ /// getModRefBehavior - Return the behavior when calling the given
+ /// call site.
+ virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+
+ /// getModRefBehavior - Return the behavior when calling the given function.
+ /// For use when the call site is not known.
+ virtual ModRefBehavior getModRefBehavior(const Function *F);
+
+ virtual DependenceResult getDependence(const Instruction *First,
+ const Value *FirstPHITranslatedAddr,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ const Value *SecondPHITranslatedAddr,
+ DependenceQueryFlags SecondFlags);
+
+ /// 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) {
+ if (ID == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
+
+ private:
+ // Visited - Track instructions visited by a aliasPHI, aliasSelect(), and aliasGEP().
+ SmallPtrSet<const Value*, 16> Visited;
+
+ // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
+ // instruction against another.
+ AliasResult aliasGEP(const GEPOperator *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size,
+ const Value *UnderlyingV1, const Value *UnderlyingV2);
+
+ // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI
+ // instruction against another.
+ AliasResult aliasPHI(const PHINode *PN, unsigned PNSize,
+ const Value *V2, unsigned V2Size);
+
+ /// aliasSelect - Disambiguate a Select instruction against another value.
+ AliasResult aliasSelect(const SelectInst *SI, unsigned SISize,
+ const Value *V2, unsigned V2Size);
+
+ AliasResult aliasCheck(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+ };
+} // End of anonymous namespace
+
+// Register this pass...
+char BasicAliasAnalysis::ID = 0;
+INITIALIZE_AG_PASS(BasicAliasAnalysis, AliasAnalysis, "basicaa",
+ "Basic Alias Analysis (default AA impl)",
+ false, true, true);
+
+ImmutablePass *llvm::createBasicAliasAnalysisPass() {
+ return new BasicAliasAnalysis();
+}
+
+
+/// pointsToConstantMemory - Chase pointers until we find a (constant
+/// global) or not.
+bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
+ if (const GlobalVariable *GV =
+ dyn_cast<GlobalVariable>(P->getUnderlyingObject()))
+ // Note: this doesn't require GV to be "ODR" because it isn't legal for a
+ // global to be marked constant in some modules and non-constant in others.
+ // GV may even be a declaration, not a definition.
+ return GV->isConstant();
+
+ return NoAA::pointsToConstantMemory(P);
+}
+
+/// getModRefBehavior - Return the behavior when calling the given call site.
+AliasAnalysis::ModRefBehavior
+BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ if (CS.doesNotAccessMemory())
+ // Can't do better than this.
+ return DoesNotAccessMemory;
+
+ ModRefBehavior Min = UnknownModRefBehavior;
+
+ // If the callsite knows it only reads memory, don't return worse
+ // than that.
+ if (CS.onlyReadsMemory())
+ Min = OnlyReadsMemory;
+
+ // The AliasAnalysis base class has some smarts, lets use them.
+ return std::min(AliasAnalysis::getModRefBehavior(CS), Min);
+}
+
+/// getModRefBehavior - Return the behavior when calling the given function.
+/// For use when the call site is not known.
+AliasAnalysis::ModRefBehavior
+BasicAliasAnalysis::getModRefBehavior(const Function *F) {
+ if (F->doesNotAccessMemory())
+ // Can't do better than this.
+ return DoesNotAccessMemory;
+ if (F->onlyReadsMemory())
+ return OnlyReadsMemory;
+ if (unsigned id = F->getIntrinsicID())
+ return getIntrinsicModRefBehavior(id);
+
+ return NoAA::getModRefBehavior(F);
+}
+
+/// getModRefInfo - Check 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.
+AliasAnalysis::ModRefResult
+BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size) {
+ assert(notDifferentParent(CS.getInstruction(), P) &&
+ "AliasAnalysis query involving multiple functions!");
+
+ const Value *Object = P->getUnderlyingObject();
+
+ // If this is a tail call and P points to a stack location, we know that
+ // the tail call cannot access or modify the local stack.
+ // We cannot exclude byval arguments here; these belong to the caller of
+ // the current function not to the current function, and a tail callee
+ // may reference them.
+ if (isa<AllocaInst>(Object))
+ if (const CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
+ if (CI->isTailCall())
+ return NoModRef;
+
+ // If the pointer is to a locally allocated object that does not escape,
+ // then the call can not mod/ref the pointer unless the call takes the pointer
+ // as an argument, and itself doesn't capture it.
+ if (!isa<Constant>(Object) && CS.getInstruction() != Object &&
+ isNonEscapingLocalObject(Object)) {
+ bool PassedAsArg = false;
+ unsigned ArgNo = 0;
+ for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ CI != CE; ++CI, ++ArgNo) {
+ // Only look at the no-capture pointer arguments.
+ if (!(*CI)->getType()->isPointerTy() ||
+ !CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))
+ continue;
+
+ // If this is a no-capture pointer argument, see if we can tell that it
+ // 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(cast<Value>(CI), UnknownSize, P, UnknownSize)) {
+ PassedAsArg = true;
+ break;
+ }
+ }
+
+ if (!PassedAsArg)
+ return NoModRef;
}
+
+ // Finally, handle specific knowledge of intrinsics.
+ const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
+ if (II != 0)
+ switch (II->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::memcpy:
+ case Intrinsic::memmove: {
+ unsigned Len = UnknownSize;
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
+ Len = LenCI->getZExtValue();
+ Value *Dest = II->getArgOperand(0);
+ Value *Src = II->getArgOperand(1);
+ if (isNoAlias(Dest, Len, P, Size)) {
+ if (isNoAlias(Src, Len, P, Size))
+ return NoModRef;
+ return Ref;
+ }
+ break;
+ }
+ case Intrinsic::memset:
+ // Since memset is 'accesses arguments' only, the AliasAnalysis base class
+ // will handle it for the variable length case.
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
+ unsigned Len = LenCI->getZExtValue();
+ Value *Dest = II->getArgOperand(0);
+ if (isNoAlias(Dest, Len, P, Size))
+ return NoModRef;
+ }
+ break;
+ case Intrinsic::atomic_cmp_swap:
+ case Intrinsic::atomic_swap:
+ case Intrinsic::atomic_load_add:
+ case Intrinsic::atomic_load_sub:
+ case Intrinsic::atomic_load_and:
+ case Intrinsic::atomic_load_nand:
+ case Intrinsic::atomic_load_or:
+ case Intrinsic::atomic_load_xor:
+ case Intrinsic::atomic_load_max:
+ case Intrinsic::atomic_load_min:
+ case Intrinsic::atomic_load_umax:
+ case Intrinsic::atomic_load_umin:
+ if (TD) {
+ Value *Op1 = II->getArgOperand(0);
+ unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
+ if (isNoAlias(Op1, Op1Size, P, Size))
+ return NoModRef;
+ }
+ break;
+ case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start: {
+ unsigned PtrSize =
+ cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
+ if (isNoAlias(II->getArgOperand(1), PtrSize, P, Size))
+ return NoModRef;
+ break;
+ }
+ case Intrinsic::invariant_end: {
+ unsigned PtrSize =
+ cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
+ if (isNoAlias(II->getArgOperand(2), PtrSize, P, Size))
+ return NoModRef;
+ break;
+ }
+ }
+
+ // The AliasAnalysis base class has some smarts, lets use them.
+ return AliasAnalysis::getModRefInfo(CS, P, Size);
+}
+
+AliasAnalysis::DependenceResult
+BasicAliasAnalysis::getDependence(const Instruction *First,
+ const Value *FirstPHITranslatedAddr,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ const Value *SecondPHITranslatedAddr,
+ DependenceQueryFlags SecondFlags) {
+ // We don't have anything special to say yet.
+ return getDependenceViaModRefInfo(First, FirstPHITranslatedAddr, FirstFlags,
+ Second, SecondPHITranslatedAddr, SecondFlags);
}
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
const Value *V2, unsigned V2Size,
const Value *UnderlyingV1,
const Value *UnderlyingV2) {
+ // If this GEP has been visited before, we're on a use-def cycle.
+ // Such cycles are only valid when PHI nodes are involved or in unreachable
+ // code. The visitPHI function catches cycles containing PHIs, but there
+ // could still be a cycle without PHIs in unreachable code.
+ if (!Visited.insert(GEP1))
+ return MayAlias;
+
int64_t GEP1BaseOffset;
- SmallVector<std::pair<const Value*, int64_t>, 4> GEP1VariableIndices;
+ SmallVector<VariableGEPIndex, 4> GEP1VariableIndices;
// If we have two gep instructions with must-alias'ing base pointers, figure
// out if the indexes to the GEP tell us anything about the derived pointer.
if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
// Do the base pointers alias?
- AliasResult BaseAlias = aliasCheck(UnderlyingV1, ~0U, UnderlyingV2, ~0U);
+ AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize,
+ UnderlyingV2, UnknownSize);
// If we get a No or May, then return it immediately, no amount of analysis
// will improve this situation.
DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
int64_t GEP2BaseOffset;
- SmallVector<std::pair<const Value*, int64_t>, 4> GEP2VariableIndices;
+ SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
const Value *GEP2BasePtr =
DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
// Subtract the GEP2 pointer from the GEP1 pointer to find out their
// symbolic difference.
GEP1BaseOffset -= GEP2BaseOffset;
- GetIndiceDifference(GEP1VariableIndices, GEP2VariableIndices);
+ GetIndexDifference(GEP1VariableIndices, GEP2VariableIndices);
} else {
// Check to see if these two pointers are related by the getelementptr
// instruction. If one pointer is a GEP with a non-zero index of the other
// pointer, we know they cannot alias.
- //
- // FIXME: The check below only looks at the size of one of the pointers, not
- // both, this may cause us to miss things.
- if (V1Size == ~0U || V2Size == ~0U)
+
+ // If both accesses are unknown size, we can't do anything useful here.
+ if (V1Size == UnknownSize && V2Size == UnknownSize)
return MayAlias;
- AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
+ AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, V2, V2Size);
if (R != MustAlias)
// If V2 may alias GEP base pointer, conservatively returns MayAlias.
// If V2 is known not to alias GEP base pointer, then the two values
// provides an offset of 4 bytes (assuming a <= 4 byte access).
for (unsigned i = 0, e = GEP1VariableIndices.size();
i != e && GEP1BaseOffset;++i)
- if (int64_t RemovedOffset = GEP1BaseOffset/GEP1VariableIndices[i].second)
- GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].second;
+ if (int64_t RemovedOffset = GEP1BaseOffset/GEP1VariableIndices[i].Scale)
+ GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].Scale;
// If our known offset is bigger than the access size, we know we don't have
// an alias.
AliasAnalysis::AliasResult
BasicAliasAnalysis::aliasSelect(const SelectInst *SI, unsigned SISize,
const Value *V2, unsigned V2Size) {
+ // If this select has been visited before, we're on a use-def cycle.
+ // Such cycles are only valid when PHI nodes are involved or in unreachable
+ // code. The visitPHI function catches cycles containing PHIs, but there
+ // could still be a cycle without PHIs in unreachable code.
+ if (!Visited.insert(SI))
+ return MayAlias;
+
// 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))
// If both arms of the Select node NoAlias or MustAlias V2, then returns
// NoAlias / MustAlias. Otherwise, returns MayAlias.
AliasResult Alias =
- aliasCheck(SI->getTrueValue(), SISize, V2, V2Size);
+ aliasCheck(V2, V2Size, SI->getTrueValue(), SISize);
if (Alias == MayAlias)
return MayAlias;
+
+ // If V2 is visited, the recursive case will have been caught in the
+ // above aliasCheck call, so these subsequent calls to aliasCheck
+ // don't need to assume that V2 is being visited recursively.
+ Visited.erase(V2);
+
AliasResult ThisAlias =
- aliasCheck(SI->getFalseValue(), SISize, V2, V2Size);
+ aliasCheck(V2, V2Size, SI->getFalseValue(), SISize);
if (ThisAlias != Alias)
return MayAlias;
return Alias;
BasicAliasAnalysis::aliasPHI(const PHINode *PN, unsigned PNSize,
const Value *V2, unsigned V2Size) {
// The PHI node has already been visited, avoid recursion any further.
- if (!VisitedPHIs.insert(PN))
+ if (!Visited.insert(PN))
return MayAlias;
// If the values are PHIs in the same block, we can do a more precise
for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
Value *V = V1Srcs[i];
- // If V2 is a PHI, the recursive case will have been caught in the
+ // If V2 is visited, the recursive case will have been caught in the
// above aliasCheck call, so these subsequent calls to aliasCheck
// don't need to assume that V2 is being visited recursively.
- VisitedPHIs.erase(V2);
+ Visited.erase(V2);
AliasResult ThisAlias = aliasCheck(V2, V2Size, V, PNSize);
if (ThisAlias != Alias || ThisAlias == MayAlias)
AliasAnalysis::AliasResult
BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
+ // If either of the memory references is empty, it doesn't matter what the
+ // pointer values are.
+ if (V1Size == 0 || V2Size == 0)
+ return NoAlias;
+
// Strip off any casts if they exist.
V1 = V1->stripPointerCasts();
V2 = V2->stripPointerCasts();
// Are we checking for alias of the same value?
if (V1 == V2) return MustAlias;
- if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
+ if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
return NoAlias; // Scalars cannot alias each other
// Figure out what objects these things are pointing to if we can.
(isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
return NoAlias;
- // Arguments can't alias with local allocations or noalias calls.
- if ((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1))))
+ // Arguments can't alias with local allocations or noalias calls
+ // in the same function.
+ if (((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
+ (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1)))))
return NoAlias;
// Most objects can't alias null.
- if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
- (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
+ if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
+ (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
return NoAlias;
- }
+ // If one pointer is the result of a call/invoke or load and the other is a
+ // non-escaping local object within the same function, then we know the
+ // object couldn't escape to a point where the call could return it.
+ //
+ // Note that if the pointers are in different functions, there are a
+ // variety of complications. A call with a nocapture argument may still
+ // temporary store the nocapture argument's value in a temporary memory
+ // location if that memory location doesn't escape. Or it may pass a
+ // nocapture value to other functions as long as they don't capture it.
+ if (isEscapeSource(O1) && isNonEscapingLocalObject(O2))
+ return NoAlias;
+ if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
+ return NoAlias;
+ }
+
// 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 != ~0U && isObjectSmallerThan(O2, V1Size, *TD)) ||
- (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, *TD)))
+ if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD)) ||
+ (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD)))
return NoAlias;
- // If one pointer is the result of a call/invoke or load and the other is a
- // non-escaping local object, then we know the object couldn't escape to a
- // point where the call could return it. The load case works because
- // isNonEscapingLocalObject considers all stores to be escapes (it
- // passes true for the StoreCaptures argument to PointerMayBeCaptured).
- if (O1 != O2) {
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1) || isa<LoadInst>(O1) ||
- isa<Argument>(O1)) &&
- isNonEscapingLocalObject(O2))
- return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2) || isa<LoadInst>(O2) ||
- isa<Argument>(O2)) &&
- isNonEscapingLocalObject(O1))
- return NoAlias;
- }
-
// FIXME: This isn't aggressively handling alias(GEP, PHI) for example: if the
// GEP can't simplify, we don't even look at the PHI cases.
if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
if (const SelectInst *S1 = dyn_cast<SelectInst>(V1))
return aliasSelect(S1, V1Size, V2, V2Size);
- return MayAlias;
+ return NoAA::alias(V1, V1Size, V2, V2Size);
}
// Make sure that anything that uses AliasAnalysis pulls in this file.
projects / oota-llvm.git / blobdiff