[llvm-commits] [llvm] r116876 - in /llvm/trunk: include/llvm/Analysis/AliasAnalysis.h include/llvm/Analysis/Passes.h lib/Analysis/AliasAnalysis.cpp lib/Analysis/BasicAliasAnalysis.cpp lib/Analysis/NoAliasAnalysis.cpp
Dan Gohman
gohman at apple.com
Tue Oct 19 16:09:08 PDT 2010
Author: djg
Date: Tue Oct 19 18:09:08 2010
New Revision: 116876
URL: http://llvm.org/viewvc/llvm-project?rev=116876&view=rev
Log:
Move NoAA out of BasicAliasAnalysis.cpp into its own file, now that
it doesn't have a special relationship with BasicAliasAnalysis
anymore.
Added:
llvm/trunk/lib/Analysis/NoAliasAnalysis.cpp
- copied, changed from r116875, llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Modified:
llvm/trunk/include/llvm/Analysis/AliasAnalysis.h
llvm/trunk/include/llvm/Analysis/Passes.h
llvm/trunk/lib/Analysis/AliasAnalysis.cpp
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Modified: llvm/trunk/include/llvm/Analysis/AliasAnalysis.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/AliasAnalysis.h?rev=116876&r1=116875&r2=116876&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/AliasAnalysis.h (original)
+++ llvm/trunk/include/llvm/Analysis/AliasAnalysis.h Tue Oct 19 18:09:08 2010
@@ -28,7 +28,6 @@
#define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
#include "llvm/Support/CallSite.h"
-#include "llvm/System/IncludeFile.h"
#include <vector>
namespace llvm {
@@ -422,11 +421,4 @@
} // End llvm namespace
-// Because of the way .a files work, we must force the BasicAA implementation to
-// be pulled in if the AliasAnalysis header is included. Otherwise we run
-// the risk of AliasAnalysis being used, but the default implementation not
-// being linked into the tool that uses it.
-FORCE_DEFINING_FILE_TO_BE_LINKED(AliasAnalysis)
-FORCE_DEFINING_FILE_TO_BE_LINKED(BasicAliasAnalysis)
-
#endif
Modified: llvm/trunk/include/llvm/Analysis/Passes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Passes.h?rev=116876&r1=116875&r2=116876&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/Passes.h (original)
+++ llvm/trunk/include/llvm/Analysis/Passes.h Tue Oct 19 18:09:08 2010
@@ -59,7 +59,7 @@
//===--------------------------------------------------------------------===//
//
- // createBasicAliasAnalysisPass - This pass implements the default alias
+ // createBasicAliasAnalysisPass - This pass implements the stateless alias
// analysis.
//
ImmutablePass *createBasicAliasAnalysisPass();
Modified: llvm/trunk/lib/Analysis/AliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/AliasAnalysis.cpp?rev=116876&r1=116875&r2=116876&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/AliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/AliasAnalysis.cpp Tue Oct 19 18:09:08 2010
@@ -342,9 +342,3 @@
return A->hasNoAliasAttr() || A->hasByValAttr();
return false;
}
-
-// Because of the way .a files work, we must force the BasicAA implementation to
-// be pulled in if the AliasAnalysis classes are pulled in. Otherwise we run
-// the risk of AliasAnalysis being used, but the default implementation not
-// being linked into the tool that uses it.
-DEFINING_FILE_FOR(AliasAnalysis)
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=116876&r1=116875&r2=116876&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Tue Oct 19 18:09:08 2010
@@ -1,4 +1,4 @@
-//===- BasicAliasAnalysis.cpp - Local Alias Analysis Impl -----------------===//
+//===- BasicAliasAnalysis.cpp - Stateless Alias Analysis Impl -------------===//
//
// The LLVM Compiler Infrastructure
//
@@ -7,9 +7,9 @@
//
//===----------------------------------------------------------------------===//
//
-// This file defines the default implementation of the Alias Analysis interface
-// that simply implements a few identities (two different globals cannot alias,
-// etc), but otherwise does no analysis.
+// This file defines the primary stateless implementation of the
+// Alias Analysis interface that implements identities (two different
+// globals cannot alias, etc), but does no stateful analysis.
//
//===----------------------------------------------------------------------===//
@@ -129,74 +129,6 @@
}
//===----------------------------------------------------------------------===//
-// NoAA Pass
-//===----------------------------------------------------------------------===//
-
-namespace {
- /// NoAA - This class implements the -no-aa pass, which always returns "I
- /// don't know" for alias queries. NoAA is unlike other alias analysis
- /// implementations, in that it does not chain to a previous analysis. As
- /// such it doesn't follow many of the rules that other alias analyses must.
- ///
- struct NoAA : public ImmutablePass, public AliasAnalysis {
- static char ID; // Class identification, replacement for typeinfo
- NoAA() : ImmutablePass(ID) {
- initializeNoAAPass(*PassRegistry::getPassRegistry());
- }
- explicit NoAA(char &PID) : ImmutablePass(PID) {}
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- }
-
- virtual void initializePass() {
- TD = getAnalysisIfAvailable<TargetData>();
- }
-
- virtual AliasResult alias(const Location &LocA, const Location &LocB) {
- return MayAlias;
- }
-
- virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
- return UnknownModRefBehavior;
- }
- virtual ModRefBehavior getModRefBehavior(const Function *F) {
- return UnknownModRefBehavior;
- }
-
- virtual bool pointsToConstantMemory(const Location &Loc) { return false; }
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
- const Location &Loc) {
- return ModRef;
- }
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
- ImmutableCallSite CS2) {
- return ModRef;
- }
-
- 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;
-INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
- "No Alias Analysis (always returns 'may' alias)",
- true, true, true)
-
-ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
-
-//===----------------------------------------------------------------------===//
// GetElementPtr Instruction Decomposition and Analysis
//===----------------------------------------------------------------------===//
@@ -487,12 +419,10 @@
#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 {
+ /// BasicAliasAnalysis - This is the primary alias analysis implementation.
+ struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
- BasicAliasAnalysis() : NoAA(ID) {
+ BasicAliasAnalysis() : ImmutablePass(ID) {
initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
}
@@ -580,7 +510,7 @@
// Register this pass...
char BasicAliasAnalysis::ID = 0;
INITIALIZE_AG_PASS(BasicAliasAnalysis, AliasAnalysis, "basicaa",
- "Basic Alias Analysis (default AA impl)",
+ "Basic Alias Analysis (stateless AA impl)",
false, true, false)
ImmutablePass *llvm::createBasicAliasAnalysisPass() {
@@ -1125,6 +1055,3 @@
return AliasAnalysis::alias(Location(V1, V1Size, V1TBAAInfo),
Location(V2, V2Size, V2TBAAInfo));
}
-
-// Make sure that anything that uses AliasAnalysis pulls in this file.
-DEFINING_FILE_FOR(BasicAliasAnalysis)
Copied: llvm/trunk/lib/Analysis/NoAliasAnalysis.cpp (from r116875, llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp)
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/NoAliasAnalysis.cpp?p2=llvm/trunk/lib/Analysis/NoAliasAnalysis.cpp&p1=llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp&r1=116875&r2=116876&rev=116876&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/NoAliasAnalysis.cpp Tue Oct 19 18:09:08 2010
@@ -1,4 +1,4 @@
-//===- BasicAliasAnalysis.cpp - Local Alias Analysis Impl -----------------===//
+//===- NoAliasAnalysis.cpp - Minimal Alias Analysis Impl ------------------===//
//
// The LLVM Compiler Infrastructure
//
@@ -8,130 +8,16 @@
//===----------------------------------------------------------------------===//
//
// This file defines the default implementation of the Alias Analysis interface
-// that simply implements a few identities (two different globals cannot alias,
-// etc), but otherwise does no analysis.
+// that simply returns "I don't know" for all queries.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Function.h"
-#include "llvm/GlobalAlias.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Operator.h"
#include "llvm/Pass.h"
-#include "llvm/Analysis/CaptureTracking.h"
-#include "llvm/Analysis/MemoryBuiltins.h"
-#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
-#include <algorithm>
using namespace llvm;
-//===----------------------------------------------------------------------===//
-// Useful predicates
-//===----------------------------------------------------------------------===//
-
-/// isKnownNonNull - Return true if we know that the specified value is never
-/// null.
-static bool isKnownNonNull(const Value *V) {
- // Alloca never returns null, malloc might.
- if (isa<AllocaInst>(V)) return true;
-
- // A byval argument is never null.
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasByValAttr();
-
- // Global values are not null unless extern weak.
- if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
- return !GV->hasExternalWeakLinkage();
- return false;
-}
-
-/// isNonEscapingLocalObject - Return true if the pointer is to a function-local
-/// object that never escapes from the function.
-static bool isNonEscapingLocalObject(const Value *V) {
- // If this is a local allocation, check to see if it escapes.
- if (isa<AllocaInst>(V) || isNoAliasCall(V))
- // Set StoreCaptures to True so that we can assume in our callers that the
- // pointer is not the result of a load instruction. Currently
- // PointerMayBeCaptured doesn't have any special analysis for the
- // StoreCaptures=false case; if it did, our callers could be refined to be
- // more precise.
- return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
-
- // If this is an argument that corresponds to a byval or noalias argument,
- // then it has not escaped before entering the function. Check if it escapes
- // inside the function.
- if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr() || A->hasNoAliasAttr()) {
- // Don't bother analyzing arguments already known not to escape.
- if (A->hasNoCaptureAttr())
- return true;
- return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
- }
- 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.
-static bool isObjectSmallerThan(const Value *V, uint64_t Size,
- const TargetData &TD) {
- const Type *AccessTy;
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
- AccessTy = GV->getType()->getElementType();
- } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
- if (!AI->isArrayAllocation())
- AccessTy = AI->getType()->getElementType();
- else
- return false;
- } 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->getArgOperand(0)))
- return (C->getZExtValue() < Size);
- return false;
- } else if (const Argument *A = dyn_cast<Argument>(V)) {
- if (A->hasByValAttr())
- AccessTy = cast<PointerType>(A->getType())->getElementType();
- else
- return false;
- } else {
- return false;
- }
-
- if (AccessTy->isSized())
- return TD.getTypeAllocSize(AccessTy) < Size;
- return false;
-}
-
-//===----------------------------------------------------------------------===//
-// NoAA Pass
-//===----------------------------------------------------------------------===//
-
namespace {
/// NoAA - This class implements the -no-aa pass, which always returns "I
/// don't know" for alias queries. NoAA is unlike other alias analysis
@@ -143,12 +29,13 @@
NoAA() : ImmutablePass(ID) {
initializeNoAAPass(*PassRegistry::getPassRegistry());
}
- explicit NoAA(char &PID) : ImmutablePass(PID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
}
virtual void initializePass() {
+ // Note: NoAA does not call InitializeAliasAnalysis because it's
+ // special and does not support chaining.
TD = getAnalysisIfAvailable<TargetData>();
}
@@ -195,936 +82,3 @@
true, true, true)
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
-
-//===----------------------------------------------------------------------===//
-// GetElementPtr Instruction Decomposition and Analysis
-//===----------------------------------------------------------------------===//
-
-namespace {
- enum ExtensionKind {
- EK_NotExtended,
- EK_SignExt,
- EK_ZeroExt
- };
-
- struct VariableGEPIndex {
- const Value *V;
- ExtensionKind Extension;
- int64_t Scale;
- };
-}
-
-
-/// GetLinearExpression - Analyze the specified value as a linear expression:
-/// "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,
- 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))) {
- switch (BOp->getOpcode()) {
- default: break;
- 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))
- break;
- // FALL THROUGH.
- case Instruction::Add:
- V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
- TD, Depth+1);
- Offset += RHSC->getValue();
- return V;
- 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;
-}
-
-/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
-/// 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.
-///
-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;
- do {
- // See if this is a bitcast or GEP.
- const Operator *Op = dyn_cast<Operator>(V);
- if (Op == 0) {
- // The only non-operator case we can handle are GlobalAliases.
- if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
- if (!GA->mayBeOverridden()) {
- V = GA->getAliasee();
- continue;
- }
- }
- return V;
- }
-
- if (Op->getOpcode() == Instruction::BitCast) {
- V = Op->getOperand(0);
- continue;
- }
-
- const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
- if (GEPOp == 0)
- return V;
-
- // Don't attempt to analyze GEPs over unsized objects.
- if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
- ->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 == 0) {
- if (!GEPOp->hasAllZeroIndices())
- return V;
- V = GEPOp->getOperand(0);
- continue;
- }
-
- // 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 = GEPOp->op_begin()+1,
- E = GEPOp->op_end(); I != E; ++I) {
- Value *Index = *I;
- // Compute the (potentially symbolic) offset in bytes for this index.
- if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
- // For a struct, add the member offset.
- unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
- if (FieldNo == 0) continue;
-
- BaseOffs += TD->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();
- continue;
- }
-
- 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, Extension,
- *TD, 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.
- BaseOffs += IndexOffset.getSExtValue()*Scale;
- Scale *= IndexScale.getSExtValue();
-
-
- // If we already had an occurrance of this index variable, merge this
- // scale into it. For example, we want to handle:
- // 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) {
- 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-TD->getPointerSizeInBits()) {
- Scale <<= ShiftBits;
- Scale = (int64_t)Scale >> ShiftBits;
- }
-
- 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;
-}
-
-/// 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 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].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].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].Scale != Scale)
- Dest[j].Scale -= Scale;
- else
- Dest.erase(Dest.begin()+j);
- Scale = 0;
- break;
- }
-
- // If we didn't consume this entry, add it to the end of the Dest list.
- 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) {
- initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
- }
-
- virtual void initializePass() {
- InitializeAliasAnalysis(this);
- }
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<AliasAnalysis>();
- }
-
- virtual AliasResult alias(const Location &LocA,
- const Location &LocB) {
- assert(Visited.empty() && "Visited must be cleared after use!");
- assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
- "BasicAliasAnalysis doesn't support interprocedural queries.");
- AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.TBAATag,
- LocB.Ptr, LocB.Size, LocB.TBAATag);
- Visited.clear();
- return Alias;
- }
-
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
- const Location &Loc);
-
- 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 Location &Loc);
-
- /// 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);
-
- /// 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, uint64_t V1Size,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo,
- 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, uint64_t PNSize,
- const MDNode *PNTBAAInfo,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo);
-
- /// aliasSelect - Disambiguate a Select instruction against another value.
- AliasResult aliasSelect(const SelectInst *SI, uint64_t SISize,
- const MDNode *SITBAAInfo,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo);
-
- AliasResult aliasCheck(const Value *V1, uint64_t V1Size,
- const MDNode *V1TBAATag,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAATag);
- };
-} // 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, false)
-
-ImmutablePass *llvm::createBasicAliasAnalysisPass() {
- return new BasicAliasAnalysis();
-}
-
-
-/// pointsToConstantMemory - Chase pointers until we find a (constant
-/// global) or not.
-bool BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc) {
- if (const GlobalVariable *GV =
- dyn_cast<GlobalVariable>(Loc.Ptr->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 AliasAnalysis::pointsToConstantMemory(Loc);
-}
-
-/// 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 AliasAnalysis::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 Location &Loc) {
- assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
- "AliasAnalysis query involving multiple functions!");
-
- const Value *Object = Loc.Ptr->getUnderlyingObject();
-
- // 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.
- // 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(Location(cast<Value>(CI)), Loc)) {
- 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: {
- uint64_t 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(Location(Dest, Len), Loc)) {
- if (isNoAlias(Location(Src, Len), Loc))
- 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))) {
- uint64_t Len = LenCI->getZExtValue();
- Value *Dest = II->getArgOperand(0);
- if (isNoAlias(Location(Dest, Len), Loc))
- 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);
- uint64_t Op1Size = TD->getTypeStoreSize(Op1->getType());
- MDNode *Tag = II->getMetadata(LLVMContext::MD_tbaa);
- if (isNoAlias(Location(Op1, Op1Size, Tag), Loc))
- return NoModRef;
- }
- break;
- case Intrinsic::lifetime_start:
- case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start: {
- uint64_t PtrSize =
- cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
- if (isNoAlias(Location(II->getArgOperand(1),
- PtrSize,
- II->getMetadata(LLVMContext::MD_tbaa)),
- Loc))
- return NoModRef;
- break;
- }
- case Intrinsic::invariant_end: {
- uint64_t PtrSize =
- cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
- if (isNoAlias(Location(II->getArgOperand(2),
- PtrSize,
- II->getMetadata(LLVMContext::MD_tbaa)),
- Loc))
- return NoModRef;
- break;
- }
- }
-
- // The AliasAnalysis base class has some smarts, lets use them.
- return AliasAnalysis::getModRefInfo(CS, Loc);
-}
-
-/// 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 GEP1->getUnderlyingObject(),
-/// UnderlyingV2 is the same for V2.
-///
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo,
- 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<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, UnknownSize, 0,
- UnderlyingV2, UnknownSize, 0);
-
- // If we get a No or May, then return it immediately, no amount of analysis
- // will improve this situation.
- if (BaseAlias != MustAlias) return BaseAlias;
-
- // Otherwise, we have a MustAlias. Since the base pointers alias each other
- // 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);
-
- int64_t GEP2BaseOffset;
- SmallVector<VariableGEPIndex, 4> GEP2VariableIndices;
- const Value *GEP2BasePtr =
- DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
-
- // If DecomposeGEPExpression isn't able to look all the way through the
- // addressing operation, we must not have TD and this is too complex for us
- // to handle without it.
- if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
- assert(TD == 0 &&
- "DecomposeGEPExpression and getUnderlyingObject disagree!");
- return MayAlias;
- }
-
- // Subtract the GEP2 pointer from the GEP1 pointer to find out their
- // symbolic difference.
- GEP1BaseOffset -= GEP2BaseOffset;
- 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.
-
- // If both accesses are unknown size, we can't do anything useful here.
- if (V1Size == UnknownSize && V2Size == UnknownSize)
- return MayAlias;
-
- AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, 0,
- V2, V2Size, V2TBAAInfo);
- 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
- // cannot alias per GEP semantics: "A pointer value formed from a
- // getelementptr instruction is associated with the addresses associated
- // with the first operand of the getelementptr".
- return R;
-
- const Value *GEP1BasePtr =
- DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
-
- // If DecomposeGEPExpression isn't able to look all the way through the
- // addressing operation, we must not have TD and this is too complex for us
- // to handle without it.
- if (GEP1BasePtr != UnderlyingV1) {
- assert(TD == 0 &&
- "DecomposeGEPExpression and getUnderlyingObject disagree!");
- return MayAlias;
- }
- }
-
- // In the two GEP Case, if there is no difference in the offsets of the
- // computed pointers, the resultant pointers are a must alias. This
- // hapens when we have two lexically identical GEP's (for example).
- //
- // In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
- // must aliases the GEP, the end result is a must alias also.
- if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty())
- return MustAlias;
-
- // If we have a known constant offset, see if this offset is larger than the
- // access size being queried. If so, and if no variable indices can remove
- // pieces of this constant, then we know we have a no-alias. For example,
- // &A[100] != &A.
-
- // In order to handle cases like &A[100][i] where i is an out of range
- // subscript, we have to ignore all constant offset pieces that are a multiple
- // of a scaled index. Do this by removing constant offsets that are a
- // multiple of any of our variable indices. This allows us to transform
- // things like &A[i][1] because i has a stride of (e.g.) 8 bytes but the 1
- // 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].Scale)
- GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].Scale;
-
- // If our known offset is bigger than the access size, we know we don't have
- // an alias.
- if (GEP1BaseOffset) {
- if (GEP1BaseOffset >= 0 ?
- (V2Size != UnknownSize && (uint64_t)GEP1BaseOffset >= V2Size) :
- (V1Size != UnknownSize && -(uint64_t)GEP1BaseOffset >= V1Size &&
- GEP1BaseOffset != INT64_MIN))
- return NoAlias;
- }
-
- return MayAlias;
-}
-
-/// aliasSelect - Provide a bunch of ad-hoc rules to disambiguate a Select
-/// instruction against another.
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::aliasSelect(const SelectInst *SI, uint64_t SISize,
- const MDNode *SITBAAInfo,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo) {
- // 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 (SI->getCondition() == SI2->getCondition()) {
- AliasResult Alias =
- aliasCheck(SI->getTrueValue(), SISize, SITBAAInfo,
- SI2->getTrueValue(), V2Size, V2TBAAInfo);
- if (Alias == MayAlias)
- return MayAlias;
- AliasResult ThisAlias =
- aliasCheck(SI->getFalseValue(), SISize, SITBAAInfo,
- SI2->getFalseValue(), V2Size, V2TBAAInfo);
- if (ThisAlias != Alias)
- return MayAlias;
- return Alias;
- }
-
- // If both arms of the Select node NoAlias or MustAlias V2, then returns
- // NoAlias / MustAlias. Otherwise, returns MayAlias.
- AliasResult Alias =
- aliasCheck(V2, V2Size, V2TBAAInfo, SI->getTrueValue(), SISize, SITBAAInfo);
- 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(V2, V2Size, V2TBAAInfo, SI->getFalseValue(), SISize, SITBAAInfo);
- if (ThisAlias != Alias)
- return MayAlias;
- return Alias;
-}
-
-// aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI instruction
-// against another.
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
- const MDNode *PNTBAAInfo,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo) {
- // The PHI node has already been visited, avoid recursion any further.
- if (!Visited.insert(PN))
- return MayAlias;
-
- // If the values are PHIs in the same block, we can do a more precise
- // as well as efficient check: just check for aliases between the values
- // on corresponding edges.
- if (const PHINode *PN2 = dyn_cast<PHINode>(V2))
- if (PN2->getParent() == PN->getParent()) {
- AliasResult Alias =
- aliasCheck(PN->getIncomingValue(0), PNSize, PNTBAAInfo,
- PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)),
- V2Size, V2TBAAInfo);
- if (Alias == MayAlias)
- return MayAlias;
- for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
- AliasResult ThisAlias =
- aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo,
- PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
- V2Size, V2TBAAInfo);
- if (ThisAlias != Alias)
- return MayAlias;
- }
- return Alias;
- }
-
- SmallPtrSet<Value*, 4> UniqueSrc;
- SmallVector<Value*, 4> V1Srcs;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- Value *PV1 = PN->getIncomingValue(i);
- if (isa<PHINode>(PV1))
- // If any of the source itself is a PHI, return MayAlias conservatively
- // to avoid compile time explosion. The worst possible case is if both
- // sides are PHI nodes. In which case, this is O(m x n) time where 'm'
- // and 'n' are the number of PHI sources.
- return MayAlias;
- if (UniqueSrc.insert(PV1))
- V1Srcs.push_back(PV1);
- }
-
- AliasResult Alias = aliasCheck(V2, V2Size, V2TBAAInfo,
- V1Srcs[0], PNSize, PNTBAAInfo);
- // Early exit if the check of the first PHI source against V2 is MayAlias.
- // Other results are not possible.
- if (Alias == MayAlias)
- return MayAlias;
-
- // If all sources of the PHI node NoAlias or MustAlias V2, then returns
- // NoAlias / MustAlias. Otherwise, returns MayAlias.
- for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
- Value *V = V1Srcs[i];
-
- // 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(V2, V2Size, V2TBAAInfo,
- V, PNSize, PNTBAAInfo);
- if (ThisAlias != Alias || ThisAlias == MayAlias)
- return MayAlias;
- }
-
- return Alias;
-}
-
-// aliasCheck - Provide a bunch of ad-hoc rules to disambiguate in common cases,
-// such as array references.
-//
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size,
- const MDNode *V1TBAAInfo,
- const Value *V2, uint64_t V2Size,
- const MDNode *V2TBAAInfo) {
- // 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 (!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.
- const Value *O1 = V1->getUnderlyingObject();
- const Value *O2 = V2->getUnderlyingObject();
-
- // Null values in the default address space don't point to any object, so they
- // don't alias any other pointer.
- if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1))
- if (CPN->getType()->getAddressSpace() == 0)
- return NoAlias;
- if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2))
- if (CPN->getType()->getAddressSpace() == 0)
- return NoAlias;
-
- if (O1 != O2) {
- // If V1/V2 point to two different objects we know that we have no alias.
- if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
- return NoAlias;
-
- // Constant pointers can't alias with non-const isIdentifiedObject objects.
- if ((isa<Constant>(O1) && isIdentifiedObject(O2) && !isa<Constant>(O2)) ||
- (isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
- return NoAlias;
-
- // 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>(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 != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD)) ||
- (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD)))
- 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)) {
- std::swap(V1, V2);
- std::swap(V1Size, V2Size);
- std::swap(O1, O2);
- }
- if (const GEPOperator *GV1 = dyn_cast<GEPOperator>(V1)) {
- AliasResult Result = aliasGEP(GV1, V1Size, V2, V2Size, V2TBAAInfo, O1, O2);
- if (Result != MayAlias) return Result;
- }
-
- if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
- std::swap(V1, V2);
- std::swap(V1Size, V2Size);
- }
- if (const PHINode *PN = dyn_cast<PHINode>(V1)) {
- AliasResult Result = aliasPHI(PN, V1Size, V1TBAAInfo,
- V2, V2Size, V2TBAAInfo);
- if (Result != MayAlias) return Result;
- }
-
- if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
- std::swap(V1, V2);
- std::swap(V1Size, V2Size);
- }
- if (const SelectInst *S1 = dyn_cast<SelectInst>(V1)) {
- AliasResult Result = aliasSelect(S1, V1Size, V1TBAAInfo,
- V2, V2Size, V2TBAAInfo);
- if (Result != MayAlias) return Result;
- }
-
- return AliasAnalysis::alias(Location(V1, V1Size, V1TBAAInfo),
- Location(V2, V2Size, V2TBAAInfo));
-}
-
-// Make sure that anything that uses AliasAnalysis pulls in this file.
-DEFINING_FILE_FOR(BasicAliasAnalysis)
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