//===- BasicAliasAnalysis.cpp - Local Alias Analysis Impl -----------------===//
-//
+//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+//
//===----------------------------------------------------------------------===//
//
// This file defines the default implementation of the Alias Analysis interface
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/Passes.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
+#include "llvm/ParameterAttributes.h"
#include "llvm/GlobalVariable.h"
-#include "llvm/iOther.h"
-#include "llvm/iMemory.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Compiler.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/ManagedStatic.h"
+#include <algorithm>
using namespace llvm;
-// Make sure that anything that uses AliasAnalysis pulls in this file...
-void llvm::BasicAAStub() {}
-
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 {
+ struct VISIBILITY_HIDDEN NoAA : public ImmutablePass, public AliasAnalysis {
+ static char ID; // Class identification, replacement for typeinfo
+ NoAA() : ImmutablePass((intptr_t)&ID) {}
+ explicit NoAA(intptr_t PID) : ImmutablePass(PID) { }
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
}
-
+
virtual void initializePass() {
TD = &getAnalysis<TargetData>();
}
return MayAlias;
}
+ virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> *Info) {
+ return UnknownModRefBehavior;
+ }
+
+ virtual void getArgumentAccesses(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> &Info) {
+ assert(0 && "This method may not be called on this function!");
+ }
+
virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals) { }
virtual bool pointsToConstantMemory(const Value *P) { return false; }
- virtual bool doesNotAccessMemory(Function *F) { return false; }
- virtual bool onlyReadsMemory(Function *F) { return false; }
virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
return ModRef;
}
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
};
-
+
// Register this pass...
- RegisterOpt<NoAA>
+ char NoAA::ID = 0;
+ RegisterPass<NoAA>
U("no-aa", "No Alias Analysis (always returns 'may' alias)");
// Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis, NoAA> V;
+ RegisterAnalysisGroup<AliasAnalysis> V(U);
} // End of anonymous namespace
+ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
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 {
+ struct VISIBILITY_HIDDEN BasicAliasAnalysis : public NoAA {
+ static char ID; // Class identification, replacement for typeinfo
+ BasicAliasAnalysis() : NoAA((intptr_t)&ID) { }
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
+ ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
+ return NoAA::getModRefInfo(CS1,CS2);
+ }
/// hasNoModRefInfoForCalls - We can provide mod/ref information against
/// non-escaping allocations.
/// global) or not.
bool pointsToConstantMemory(const Value *P);
- virtual bool doesNotAccessMemory(Function *F);
- virtual bool onlyReadsMemory(Function *F);
+ virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> *Info);
private:
// CheckGEPInstructions - Check two GEP instructions with known
// must-aliasing base pointers. This checks to see if the index expressions
// preclude the pointers from aliasing...
AliasResult
- CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
- unsigned G1Size,
- const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
- unsigned G2Size);
+ CheckGEPInstructions(const Type* BasePtr1Ty,
+ Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1Size,
+ const Type *BasePtr2Ty,
+ Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size);
};
-
+
// Register this pass...
- RegisterOpt<BasicAliasAnalysis>
+ char BasicAliasAnalysis::ID = 0;
+ RegisterPass<BasicAliasAnalysis>
X("basicaa", "Basic Alias Analysis (default AA impl)");
// Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis, BasicAliasAnalysis, true> Y;
+ RegisterAnalysisGroup<AliasAnalysis, true> Y(X);
} // End of anonymous namespace
-// hasUniqueAddress - Return true if the specified value points to something
-// with a unique, discernable, address.
-static inline bool hasUniqueAddress(const Value *V) {
- return isa<GlobalValue>(V) || isa<AllocationInst>(V);
+ImmutablePass *llvm::createBasicAliasAnalysisPass() {
+ return new BasicAliasAnalysis();
}
// getUnderlyingObject - This traverses the use chain to figure out what object
static const Value *getUnderlyingObject(const Value *V) {
if (!isa<PointerType>(V->getType())) return 0;
- // If we are at some type of object... return it.
- if (hasUniqueAddress(V) || isa<Argument>(V)) return V;
-
+ // If we are at some type of object, return it. GlobalValues and Allocations
+ // have unique addresses.
+ if (isa<GlobalValue>(V) || isa<AllocationInst>(V) || isa<Argument>(V))
+ return V;
+
// Traverse through different addressing mechanisms...
if (const Instruction *I = dyn_cast<Instruction>(V)) {
- if (isa<CastInst>(I) || isa<GetElementPtrInst>(I))
+ if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I))
return getUnderlyingObject(I->getOperand(0));
} else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::Cast ||
+ if (CE->getOpcode() == Instruction::BitCast ||
CE->getOpcode() == Instruction::GetElementPtr)
return getUnderlyingObject(CE->getOperand(0));
- } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
- return GV;
}
return 0;
}
return 0;
}
-static const Value *GetGEPOperands(const Value *V, std::vector<Value*> &GEPOps){
+static const Value *GetGEPOperands(const Value *V,
+ SmallVector<Value*, 16> &GEPOps){
assert(GEPOps.empty() && "Expect empty list to populate!");
GEPOps.insert(GEPOps.end(), cast<User>(V)->op_begin()+1,
cast<User>(V)->op_end());
return false;
}
+// Determine if an AllocationInst instruction escapes from the function it is
+// contained in. If it does not escape, there is no way for another function to
+// mod/ref it. We do this by looking at its uses and determining if the uses
+// can escape (recursively).
static bool AddressMightEscape(const Value *V) {
for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
UI != E; ++UI) {
const Instruction *I = cast<Instruction>(*UI);
switch (I->getOpcode()) {
- case Instruction::Load: break;
+ case Instruction::Load:
+ break; //next use.
case Instruction::Store:
if (I->getOperand(0) == V)
return true; // Escapes if the pointer is stored.
- break;
+ break; // next use.
case Instruction::GetElementPtr:
- if (AddressMightEscape(I)) return true;
- break;
- case Instruction::Cast:
+ if (AddressMightEscape(I))
+ return true;
+ break; // next use.
+ case Instruction::BitCast:
if (!isa<PointerType>(I->getType()))
return true;
- if (AddressMightEscape(I)) return true;
- break;
+ if (AddressMightEscape(I))
+ return true;
+ break; // next use
case Instruction::Ret:
// If returned, the address will escape to calling functions, but no
// callees could modify it.
- break;
+ break; // next use
default:
return true;
}
// because it simply can't get its address.
if (!AddressMightEscape(AI))
return NoModRef;
+
+ // 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.
+ if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
+ if (CI->isTailCall() && isa<AllocaInst>(AI))
+ return NoModRef;
}
// The AliasAnalysis base class has some smarts, lets use them.
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
+static bool isNoAliasArgument(const Argument *Arg) {
+ const Function *Func = Arg->getParent();
+ const ParamAttrsList *Attr = Func->getFunctionType()->getParamAttrs();
+ if (Attr) {
+ unsigned Idx = 1;
+ for (Function::const_arg_iterator I = Func->arg_begin(),
+ E = Func->arg_end(); I != E; ++I, ++Idx) {
+ if (&(*I) == Arg &&
+ Attr->paramHasAttr(Idx, ParamAttr::NoAlias))
+ return true;
+ }
+ }
+ return false;
+}
+
// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
// as array references. Note that this function is heavily tail recursive.
// Hopefully we have a smart C++ compiler. :)
const Value *V2, unsigned V2Size) {
// Strip off any constant expression casts if they exist
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V1))
- if (CE->getOpcode() == Instruction::Cast &&
- isa<PointerType>(CE->getOperand(0)->getType()))
+ if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
V1 = CE->getOperand(0);
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V2))
- if (CE->getOpcode() == Instruction::Cast &&
- isa<PointerType>(CE->getOperand(0)->getType()))
+ if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
V2 = CE->getOperand(0);
// Are we checking for alias of the same value?
if (V1 == V2) return MustAlias;
if ((!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType())) &&
- V1->getType() != Type::LongTy && V2->getType() != Type::LongTy)
+ V1->getType() != Type::Int64Ty && V2->getType() != Type::Int64Ty)
return NoAlias; // Scalars cannot alias each other
// Strip off cast instructions...
- if (const Instruction *I = dyn_cast<CastInst>(V1))
- if (isa<PointerType>(I->getOperand(0)->getType()))
- return alias(I->getOperand(0), V1Size, V2, V2Size);
- if (const Instruction *I = dyn_cast<CastInst>(V2))
- if (isa<PointerType>(I->getOperand(0)->getType()))
- return alias(V1, V1Size, I->getOperand(0), V2Size);
+ if (const BitCastInst *I = dyn_cast<BitCastInst>(V1))
+ return alias(I->getOperand(0), V1Size, V2, V2Size);
+ if (const BitCastInst *I = dyn_cast<BitCastInst>(V2))
+ return alias(V1, V1Size, I->getOperand(0), V2Size);
// Figure out what objects these things are pointing to if we can...
const Value *O1 = getUnderlyingObject(V1);
const Value *O2 = getUnderlyingObject(V2);
// Pointing at a discernible object?
- if (O1 && O2) {
- if (isa<Argument>(O1)) {
- // Incoming argument cannot alias locally allocated object!
- if (isa<AllocationInst>(O2)) return NoAlias;
- // Otherwise, nothing is known...
- } else if (isa<Argument>(O2)) {
- // Incoming argument cannot alias locally allocated object!
- if (isa<AllocationInst>(O1)) return NoAlias;
- // Otherwise, nothing is known...
- } else {
- // If they are two different objects, we know that we have no alias...
- if (O1 != O2) return NoAlias;
+ if (O1) {
+ if (O2) {
+ if (const Argument *O1Arg = dyn_cast<Argument>(O1)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O2)) return NoAlias;
+
+ // If they are two different objects, and one is a noalias argument
+ // then they do not alias.
+ if (O1 != O2 && isNoAliasArgument(O1Arg))
+ return NoAlias;
+
+ // Otherwise, nothing is known...
+ }
+
+ if (const Argument *O2Arg = dyn_cast<Argument>(O2)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O1)) return NoAlias;
+
+ // If they are two different objects, and one is a noalias argument
+ // then they do not alias.
+ if (O1 != O2 && isNoAliasArgument(O2Arg))
+ return NoAlias;
+
+ // Otherwise, nothing is known...
+
+ } else if (O1 != O2) {
+ if (!isa<Argument>(O1))
+ // If they are two different objects, and neither is an argument,
+ // we know that we have no alias...
+ return NoAlias;
+ }
+
+ // If they are the same object, they we can look at the indexes. If they
+ // index off of the object is the same for both pointers, they must alias.
+ // If they are provably different, they must not alias. Otherwise, we
+ // can't tell anything.
}
- // If they are the same object, they we can look at the indexes. If they
- // index off of the object is the same for both pointers, they must alias.
- // If they are provably different, they must not alias. Otherwise, we can't
- // tell anything.
- } else if (O1 && !isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) {
- return NoAlias; // Unique values don't alias null
- } else if (O2 && !isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) {
- return NoAlias; // Unique values don't alias null
+
+ if (!isa<Argument>(O1) && isa<ConstantPointerNull>(V2))
+ return NoAlias; // Unique values don't alias null
+
+ if (isa<GlobalVariable>(O1) ||
+ (isa<AllocationInst>(O1) &&
+ !cast<AllocationInst>(O1)->isArrayAllocation()))
+ if (cast<PointerType>(O1->getType())->getElementType()->isSized()) {
+ // If the size of the other access is larger than the total size of the
+ // global/alloca/malloc, it cannot be accessing the global (it's
+ // undefined to load or store bytes before or after an object).
+ const Type *ElTy = cast<PointerType>(O1->getType())->getElementType();
+ unsigned GlobalSize = getTargetData().getABITypeSize(ElTy);
+ if (GlobalSize < V2Size && V2Size != ~0U)
+ return NoAlias;
+ }
+ }
+
+ if (O2) {
+ if (!isa<Argument>(O2) && isa<ConstantPointerNull>(V1))
+ return NoAlias; // Unique values don't alias null
+
+ if (isa<GlobalVariable>(O2) ||
+ (isa<AllocationInst>(O2) &&
+ !cast<AllocationInst>(O2)->isArrayAllocation()))
+ if (cast<PointerType>(O2->getType())->getElementType()->isSized()) {
+ // If the size of the other access is larger than the total size of the
+ // global/alloca/malloc, it cannot be accessing the object (it's
+ // undefined to load or store bytes before or after an object).
+ const Type *ElTy = cast<PointerType>(O2->getType())->getElementType();
+ unsigned GlobalSize = getTargetData().getABITypeSize(ElTy);
+ if (GlobalSize < V1Size && V1Size != ~0U)
+ return NoAlias;
+ }
}
// If we have two gep instructions with must-alias'ing base pointers, figure
do {
BasePtr1 = cast<User>(BasePtr1)->getOperand(0);
} while (isGEP(BasePtr1) &&
- cast<User>(BasePtr1)->getOperand(1) ==
+ cast<User>(BasePtr1)->getOperand(1) ==
Constant::getNullValue(cast<User>(BasePtr1)->getOperand(1)->getType()));
do {
BasePtr2 = cast<User>(BasePtr2)->getOperand(0);
} while (isGEP(BasePtr2) &&
- cast<User>(BasePtr2)->getOperand(1) ==
+ cast<User>(BasePtr2)->getOperand(1) ==
Constant::getNullValue(cast<User>(BasePtr2)->getOperand(1)->getType()));
// Do the base pointers alias?
- AliasResult BaseAlias = alias(BasePtr1, V1Size, BasePtr2, V2Size);
+ AliasResult BaseAlias = alias(BasePtr1, ~0U, BasePtr2, ~0U);
if (BaseAlias == NoAlias) return NoAlias;
if (BaseAlias == MustAlias) {
// If the base pointers alias each other exactly, check to see if we can
// non-aliasing.
// Collect all of the chained GEP operands together into one simple place
- std::vector<Value*> GEP1Ops, GEP2Ops;
+ SmallVector<Value*, 16> GEP1Ops, GEP2Ops;
BasePtr1 = GetGEPOperands(V1, GEP1Ops);
BasePtr2 = GetGEPOperands(V2, GEP2Ops);
- AliasResult GAlias =
- CheckGEPInstructions(BasePtr1->getType(), GEP1Ops, V1Size,
- BasePtr2->getType(), GEP2Ops, V2Size);
- if (GAlias != MayAlias)
- return GAlias;
+ // If GetGEPOperands were able to fold to the same must-aliased pointer,
+ // do the comparison.
+ if (BasePtr1 == BasePtr2) {
+ AliasResult GAlias =
+ CheckGEPInstructions(BasePtr1->getType(),
+ &GEP1Ops[0], GEP1Ops.size(), V1Size,
+ BasePtr2->getType(),
+ &GEP2Ops[0], GEP2Ops.size(), V2Size);
+ if (GAlias != MayAlias)
+ return GAlias;
+ }
}
}
}
if (V1Size != ~0U && V2Size != ~0U)
- if (const User *GEP = isGEP(V1)) {
- std::vector<Value*> GEPOperands;
+ if (isGEP(V1)) {
+ SmallVector<Value*, 16> GEPOperands;
const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
if (ConstantFound) {
if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
return NoAlias;
-
+
// Otherwise we have to check to see that the distance is more than
// the size of the argument... build an index vector that is equal to
// the arguments provided, except substitute 0's for any variable
// indexes we find...
- for (unsigned i = 0; i != GEPOperands.size(); ++i)
- if (!isa<Constant>(GEPOperands[i]) || isa<GlobalValue>(GEPOperands[i]) ||
- isa<ConstantExpr>(GEPOperands[i]))
- GEPOperands[i] =Constant::getNullValue(GEPOperands[i]->getType());
- int64_t Offset = getTargetData().getIndexedOffset(BasePtr->getType(),
- GEPOperands);
- if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
- return NoAlias;
+ if (cast<PointerType>(
+ BasePtr->getType())->getElementType()->isSized()) {
+ for (unsigned i = 0; i != GEPOperands.size(); ++i)
+ if (!isa<ConstantInt>(GEPOperands[i]))
+ GEPOperands[i] =
+ Constant::getNullValue(GEPOperands[i]->getType());
+ int64_t Offset =
+ getTargetData().getIndexedOffset(BasePtr->getType(),
+ &GEPOperands[0],
+ GEPOperands.size());
+
+ if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
+ return NoAlias;
+ }
}
}
}
-
+
return MayAlias;
}
-static bool ValuesEqual(Value *V1, Value *V2) {
+// This function is used to determin if the indices of two GEP instructions are
+// equal. V1 and V2 are the indices.
+static bool IndexOperandsEqual(Value *V1, Value *V2) {
if (V1->getType() == V2->getType())
return V1 == V2;
if (Constant *C1 = dyn_cast<Constant>(V1))
if (Constant *C2 = dyn_cast<Constant>(V2)) {
- // Sign extend the constants to long types.
- C1 = ConstantExpr::getSignExtend(C1, Type::LongTy);
- C2 = ConstantExpr::getSignExtend(C2, Type::LongTy);
+ // Sign extend the constants to long types, if necessary
+ if (C1->getType() != Type::Int64Ty)
+ C1 = ConstantExpr::getSExt(C1, Type::Int64Ty);
+ if (C2->getType() != Type::Int64Ty)
+ C2 = ConstantExpr::getSExt(C2, Type::Int64Ty);
return C1 == C2;
}
return false;
/// CheckGEPInstructions - Check two GEP instructions with known must-aliasing
/// base pointers. This checks to see if the index expressions preclude the
/// pointers from aliasing...
-AliasAnalysis::AliasResult BasicAliasAnalysis::
-CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
- unsigned G1S,
- const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
- unsigned G2S) {
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::CheckGEPInstructions(
+ const Type* BasePtr1Ty, Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1S,
+ const Type *BasePtr2Ty, Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2S) {
// We currently can't handle the case when the base pointers have different
// primitive types. Since this is uncommon anyway, we are happy being
// extremely conservative.
if (BasePtr1Ty != BasePtr2Ty)
return MayAlias;
- const Type *GEPPointerTy = BasePtr1Ty;
+ const PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
// Find the (possibly empty) initial sequence of equal values... which are not
// necessarily constants.
- unsigned NumGEP1Operands = GEP1Ops.size(), NumGEP2Operands = GEP2Ops.size();
+ unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
unsigned UnequalOper = 0;
while (UnequalOper != MinOperands &&
- ValuesEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
+ IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
// Advance through the type as we go...
++UnequalOper;
if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
// getelementptrs, check to see if the tail of the leftover one is all zeros.
// If so, return mustalias.
if (UnequalOper == MinOperands) {
- if (GEP1Ops.size() < GEP2Ops.size()) std::swap(GEP1Ops, GEP2Ops);
-
+ if (NumGEP1Ops < NumGEP2Ops) {
+ std::swap(GEP1Ops, GEP2Ops);
+ std::swap(NumGEP1Ops, NumGEP2Ops);
+ }
+
bool AllAreZeros = true;
for (unsigned i = UnequalOper; i != MaxOperands; ++i)
- if (!isa<Constant>(GEP1Ops[i]) ||
+ if (!isa<Constant>(GEP1Ops[i]) ||
!cast<Constant>(GEP1Ops[i])->isNullValue()) {
AllAreZeros = false;
break;
if (AllAreZeros) return MustAlias;
}
-
+
// So now we know that the indexes derived from the base pointers,
// which are known to alias, are different. We can still determine a
// no-alias result if there are differing constant pairs in the index
// chain. For example:
// A[i][0] != A[j][1] iff (&A[0][1]-&A[0][0] >= std::max(G1S, G2S))
//
+ // We have to be careful here about array accesses. In particular, consider:
+ // A[1][0] vs A[0][i]
+ // In this case, we don't *know* that the array will be accessed in bounds:
+ // the index could even be negative. Because of this, we have to
+ // conservatively *give up* and return may alias. We disregard differing
+ // array subscripts that are followed by a variable index without going
+ // through a struct.
+ //
unsigned SizeMax = std::max(G1S, G2S);
- if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work...
+ if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work.
// Scan for the first operand that is constant and unequal in the
// two getelementptrs...
for (; FirstConstantOper != MinOperands; ++FirstConstantOper) {
const Value *G1Oper = GEP1Ops[FirstConstantOper];
const Value *G2Oper = GEP2Ops[FirstConstantOper];
-
+
if (G1Oper != G2Oper) // Found non-equal constant indexes...
- if (Constant *G1OC = dyn_cast<Constant>(const_cast<Value*>(G1Oper)))
- if (Constant *G2OC = dyn_cast<Constant>(const_cast<Value*>(G2Oper))) {
+ if (Constant *G1OC = dyn_cast<ConstantInt>(const_cast<Value*>(G1Oper)))
+ if (Constant *G2OC = dyn_cast<ConstantInt>(const_cast<Value*>(G2Oper))){
if (G1OC->getType() != G2OC->getType()) {
// Sign extend both operands to long.
- G1OC = ConstantExpr::getSignExtend(G1OC, Type::LongTy);
- G2OC = ConstantExpr::getSignExtend(G2OC, Type::LongTy);
+ if (G1OC->getType() != Type::Int64Ty)
+ G1OC = ConstantExpr::getSExt(G1OC, Type::Int64Ty);
+ if (G2OC->getType() != Type::Int64Ty)
+ G2OC = ConstantExpr::getSExt(G2OC, Type::Int64Ty);
GEP1Ops[FirstConstantOper] = G1OC;
GEP2Ops[FirstConstantOper] = G2OC;
}
-
+
if (G1OC != G2OC) {
- // Make sure they are comparable (ie, not constant expressions)...
- // and make sure the GEP with the smaller leading constant is GEP1.
- Constant *Compare = ConstantExpr::getSetGT(G1OC, G2OC);
- if (ConstantBool *CV = dyn_cast<ConstantBool>(Compare)) {
- if (CV->getValue()) // If they are comparable and G2 > G1
- std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2
- break;
+ // Handle the "be careful" case above: if this is an array/vector
+ // subscript, scan for a subsequent variable array index.
+ if (isa<SequentialType>(BasePtr1Ty)) {
+ const Type *NextTy =
+ cast<SequentialType>(BasePtr1Ty)->getElementType();
+ bool isBadCase = false;
+
+ for (unsigned Idx = FirstConstantOper+1;
+ Idx != MinOperands && isa<SequentialType>(NextTy); ++Idx) {
+ const Value *V1 = GEP1Ops[Idx], *V2 = GEP2Ops[Idx];
+ if (!isa<Constant>(V1) || !isa<Constant>(V2)) {
+ isBadCase = true;
+ break;
+ }
+ NextTy = cast<SequentialType>(NextTy)->getElementType();
+ }
+
+ if (isBadCase) G1OC = 0;
+ }
+
+ // Make sure they are comparable (ie, not constant expressions), and
+ // make sure the GEP with the smaller leading constant is GEP1.
+ if (G1OC) {
+ Constant *Compare = ConstantExpr::getICmp(ICmpInst::ICMP_SGT,
+ G1OC, G2OC);
+ if (ConstantInt *CV = dyn_cast<ConstantInt>(Compare)) {
+ if (CV->getZExtValue()) { // If they are comparable and G2 > G1
+ std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2
+ std::swap(NumGEP1Ops, NumGEP2Ops);
+ }
+ break;
+ }
}
}
}
BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(G1Oper);
}
-
+
// No shared constant operands, and we ran out of common operands. At this
// point, the GEP instructions have run through all of their operands, and we
// haven't found evidence that there are any deltas between the GEP's.
// case, there may still be hope. Check this now.
if (FirstConstantOper == MinOperands) {
// Make GEP1Ops be the longer one if there is a longer one.
- if (GEP1Ops.size() < GEP2Ops.size())
+ if (NumGEP1Ops < NumGEP2Ops) {
std::swap(GEP1Ops, GEP2Ops);
+ std::swap(NumGEP1Ops, NumGEP2Ops);
+ }
// Is there anything to check?
- if (GEP1Ops.size() > MinOperands) {
+ if (NumGEP1Ops > MinOperands) {
for (unsigned i = FirstConstantOper; i != MaxOperands; ++i)
- if (isa<ConstantInt>(GEP1Ops[i]) &&
- !cast<Constant>(GEP1Ops[i])->isNullValue()) {
+ if (isa<ConstantInt>(GEP1Ops[i]) &&
+ !cast<ConstantInt>(GEP1Ops[i])->isZero()) {
// Yup, there's a constant in the tail. Set all variables to
// constants in the GEP instruction to make it suiteable for
// TargetData::getIndexedOffset.
// Okay, now get the offset. This is the relative offset for the full
// instruction.
const TargetData &TD = getTargetData();
- int64_t Offset1 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
+ int64_t Offset1 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
+ NumGEP1Ops);
+
+ // Now check without any constants at the end.
+ int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
+ MinOperands);
- // Now crop off any constants from the end...
- GEP1Ops.resize(MinOperands);
- int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
-
// If the tail provided a bit enough offset, return noalias!
if ((uint64_t)(Offset2-Offset1) >= SizeMax)
return NoAlias;
}
}
-
+
// Couldn't find anything useful.
return MayAlias;
}
// than the first constant index of GEP2.
// Advance BasePtr[12]Ty over this first differing constant operand.
- BasePtr2Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP2Ops[FirstConstantOper]);
- BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP1Ops[FirstConstantOper]);
-
+ BasePtr2Ty = cast<CompositeType>(BasePtr1Ty)->
+ getTypeAtIndex(GEP2Ops[FirstConstantOper]);
+ BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->
+ getTypeAtIndex(GEP1Ops[FirstConstantOper]);
+
// We are going to be using TargetData::getIndexedOffset to determine the
// offset that each of the GEP's is reaching. To do this, we have to convert
// all variable references to constant references. To do this, we convert the
- // initial equal sequence of variables into constant zeros to start with.
+ // initial sequence of array subscripts into constant zeros to start with.
+ const Type *ZeroIdxTy = GEPPointerTy;
for (unsigned i = 0; i != FirstConstantOper; ++i) {
- if (!isa<Constant>(GEP1Ops[i]) || isa<ConstantExpr>(GEP1Ops[i]) ||
- !isa<Constant>(GEP2Ops[i]) || isa<ConstantExpr>(GEP2Ops[i]))
- GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Type::UIntTy);
+ if (!isa<StructType>(ZeroIdxTy))
+ GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Type::Int32Ty);
+
+ if (const CompositeType *CT = dyn_cast<CompositeType>(ZeroIdxTy))
+ ZeroIdxTy = CT->getTypeAtIndex(GEP1Ops[i]);
}
// We know that GEP1Ops[FirstConstantOper] & GEP2Ops[FirstConstantOper] are ok
-
+
// Loop over the rest of the operands...
for (unsigned i = FirstConstantOper+1; i != MaxOperands; ++i) {
- const Value *Op1 = i < GEP1Ops.size() ? GEP1Ops[i] : 0;
- const Value *Op2 = i < GEP2Ops.size() ? GEP2Ops[i] : 0;
+ const Value *Op1 = i < NumGEP1Ops ? GEP1Ops[i] : 0;
+ const Value *Op2 = i < NumGEP2Ops ? GEP2Ops[i] : 0;
// If they are equal, use a zero index...
if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) {
- if (!isa<Constant>(Op1) || isa<ConstantExpr>(Op1))
+ if (!isa<ConstantInt>(Op1))
GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType());
// Otherwise, just keep the constants we have.
} else {
if (Op1) {
if (const ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
// If this is an array index, make sure the array element is in range.
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
- if (Op1C->getRawValue() >= AT->getNumElements())
+ if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty)) {
+ if (Op1C->getZExtValue() >= AT->getNumElements())
+ return MayAlias; // Be conservative with out-of-range accesses
+ } else if (const VectorType *PT = dyn_cast<VectorType>(BasePtr1Ty)) {
+ if (Op1C->getZExtValue() >= PT->getNumElements())
return MayAlias; // Be conservative with out-of-range accesses
+ }
} else {
// GEP1 is known to produce a value less than GEP2. To be
// value possible.
//
if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
- GEP1Ops[i] = ConstantSInt::get(Type::LongTy,AT->getNumElements()-1);
+ GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,AT->getNumElements()-1);
+ else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty))
+ GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,VT->getNumElements()-1);
}
}
-
+
if (Op2) {
if (const ConstantInt *Op2C = dyn_cast<ConstantInt>(Op2)) {
// If this is an array index, make sure the array element is in range.
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
- if (Op2C->getRawValue() >= AT->getNumElements())
+ if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty)) {
+ if (Op2C->getZExtValue() >= AT->getNumElements())
+ return MayAlias; // Be conservative with out-of-range accesses
+ } else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty)) {
+ if (Op2C->getZExtValue() >= VT->getNumElements())
return MayAlias; // Be conservative with out-of-range accesses
+ }
} else { // Conservatively assume the minimum value for this index
GEP2Ops[i] = Constant::getNullValue(Op2->getType());
}
BasePtr2Ty = 0;
}
}
-
- int64_t Offset1 = getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops);
- int64_t Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops);
- assert(Offset1 < Offset2 &&"There is at least one different constant here!");
-
- if ((uint64_t)(Offset2-Offset1) >= SizeMax) {
- //std::cerr << "Determined that these two GEP's don't alias ["
- // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2;
- return NoAlias;
+
+ if (GEPPointerTy->getElementType()->isSized()) {
+ int64_t Offset1 =
+ getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops);
+ int64_t Offset2 =
+ getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops);
+ assert(Offset1 != Offset2 &&
+ "There is at least one different constant here!");
+
+ // Make sure we compare the absolute difference.
+ if (Offset1 > Offset2)
+ std::swap(Offset1, Offset2);
+
+ if ((uint64_t)(Offset2-Offset1) >= SizeMax) {
+ //cerr << "Determined that these two GEP's don't alias ["
+ // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2;
+ return NoAlias;
+ }
}
return MayAlias;
}
namespace {
- struct StringCompare {
+ struct VISIBILITY_HIDDEN StringCompare {
bool operator()(const char *LHS, const char *RHS) {
return strcmp(LHS, RHS) < 0;
}
// Note that this list cannot contain libm functions (such as acos and sqrt)
// that set errno on a domain or other error.
-static const char *DoesntAccessMemoryTable[] = {
- // LLVM intrinsics:
- "llvm.frameaddress", "llvm.returnaddress", "llvm.readport", "llvm.isunordered",
-
+static const char *DoesntAccessMemoryFns[] = {
"abs", "labs", "llabs", "imaxabs", "fabs", "fabsf", "fabsl",
"trunc", "truncf", "truncl", "ldexp",
-
+
"atan", "atanf", "atanl", "atan2", "atan2f", "atan2l",
"cbrt",
- "cos", "cosf", "cosl", "cosh", "coshf", "coshl",
- "exp", "expf", "expl",
+ "cos", "cosf", "cosl",
+ "exp", "expf", "expl",
"hypot",
- "sin", "sinf", "sinl", "sinh", "sinhf", "sinhl",
+ "sin", "sinf", "sinl",
"tan", "tanf", "tanl", "tanh", "tanhf", "tanhl",
+
+ "floor", "floorf", "floorl", "ceil", "ceilf", "ceill",
// ctype.h
"isalnum", "isalpha", "iscntrl", "isdigit", "isgraph", "islower", "isprint"
"iswalnum", "iswalpha", "iswcntrl", "iswdigit", "iswgraph", "iswlower",
"iswprint", "iswpunct", "iswspace", "iswupper", "iswxdigit",
- "iswctype", "towctrans", "towlower", "towupper",
+ "iswctype", "towctrans", "towlower", "towupper",
- "btowc", "wctob",
+ "btowc", "wctob",
"isinf", "isnan", "finite",
"nexttoward", "nexttowardf", "nexttowardd",
"nextafter", "nextafterf", "nextafterd",
- // glibc functions:
- "__fpclassify", "__fpclassifyf", "__fpclassifyl",
+ // ISO C99:
"__signbit", "__signbitf", "__signbitl",
};
-static const unsigned DAMTableSize =
- sizeof(DoesntAccessMemoryTable)/sizeof(DoesntAccessMemoryTable[0]);
-
-/// doesNotAccessMemory - Return true if we know that the function does not
-/// access memory at all. Since basicaa does no analysis, we can only do simple
-/// things here. In particular, if we have an external function with the name
-/// of a standard C library function, we are allowed to assume it will be
-/// resolved by libc, so we can hardcode some entries in here.
-bool BasicAliasAnalysis::doesNotAccessMemory(Function *F) {
- if (!F->isExternal()) return false;
-
- static bool Initialized = false;
- if (!Initialized) {
- // Sort the table the first time through.
- std::sort(DoesntAccessMemoryTable, DoesntAccessMemoryTable+DAMTableSize,
- StringCompare());
- Initialized = true;
- }
-
- const char **Ptr = std::lower_bound(DoesntAccessMemoryTable,
- DoesntAccessMemoryTable+DAMTableSize,
- F->getName().c_str(), StringCompare());
- return Ptr != DoesntAccessMemoryTable+DAMTableSize && *Ptr == F->getName();
-}
-
-static const char *OnlyReadsMemoryTable[] = {
+static const char *OnlyReadsMemoryFns[] = {
"atoi", "atol", "atof", "atoll", "atoq", "a64l",
- "bcmp", "memcmp", "memchr", "memrchr", "wmemcmp", "wmemchr",
+ "bcmp", "memcmp", "memchr", "memrchr", "wmemcmp", "wmemchr",
// Strings
"strcmp", "strcasecmp", "strcoll", "strncmp", "strncasecmp",
- "strchr", "strcspn", "strlen", "strpbrk", "strrchr", "strspn", "strstr",
+ "strchr", "strcspn", "strlen", "strpbrk", "strrchr", "strspn", "strstr",
"index", "rindex",
// Wide char strings
"wcschr", "wcscmp", "wcscoll", "wcscspn", "wcslen", "wcsncmp", "wcspbrk",
- "wcsrchr", "wcsspn", "wcsstr",
+ "wcsrchr", "wcsspn", "wcsstr",
// glibc
"alphasort", "alphasort64", "versionsort", "versionsort64",
"feof_unlocked", "ferror_unlocked", "fileno_unlocked"
};
-static const unsigned ORMTableSize =
- sizeof(OnlyReadsMemoryTable)/sizeof(OnlyReadsMemoryTable[0]);
+static ManagedStatic<std::vector<const char*> > NoMemoryTable;
+static ManagedStatic<std::vector<const char*> > OnlyReadsMemoryTable;
+
+static ManagedStatic<BitVector> NoMemoryIntrinsics;
+static ManagedStatic<BitVector> OnlyReadsMemoryIntrinsics;
+
-bool BasicAliasAnalysis::onlyReadsMemory(Function *F) {
- if (doesNotAccessMemory(F)) return true;
- if (!F->isExternal()) return false;
+AliasAnalysis::ModRefBehavior
+BasicAliasAnalysis::getModRefBehavior(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> *Info) {
+ if (!F->isDeclaration()) return UnknownModRefBehavior;
static bool Initialized = false;
if (!Initialized) {
+ NoMemoryTable->insert(NoMemoryTable->end(),
+ DoesntAccessMemoryFns,
+ array_endof(DoesntAccessMemoryFns));
+
+ OnlyReadsMemoryTable->insert(OnlyReadsMemoryTable->end(),
+ OnlyReadsMemoryFns,
+ array_endof(OnlyReadsMemoryFns));
+
// Sort the table the first time through.
- std::sort(OnlyReadsMemoryTable, OnlyReadsMemoryTable+ORMTableSize,
+ std::sort(NoMemoryTable->begin(), NoMemoryTable->end(), StringCompare());
+ std::sort(OnlyReadsMemoryTable->begin(), OnlyReadsMemoryTable->end(),
StringCompare());
+
+ NoMemoryIntrinsics->resize(Intrinsic::num_intrinsics);
+ OnlyReadsMemoryIntrinsics->resize(Intrinsic::num_intrinsics);
+#define GET_MODREF_BEHAVIOR
+#include "llvm/Intrinsics.gen"
+#undef GET_MODREF_BEHAVIOR
+
Initialized = true;
}
- const char **Ptr = std::lower_bound(OnlyReadsMemoryTable,
- OnlyReadsMemoryTable+ORMTableSize,
- F->getName().c_str(), StringCompare());
- return Ptr != OnlyReadsMemoryTable+ORMTableSize && *Ptr == F->getName();
-}
+ // If this is an intrinsic, we can use lookup tables
+ if (unsigned id = F->getIntrinsicID()) {
+ if (NoMemoryIntrinsics->test(id))
+ return DoesNotAccessMemory;
+ if (OnlyReadsMemoryIntrinsics->test(id))
+ return OnlyReadsMemory;
+ return UnknownModRefBehavior;
+ }
+
+ ValueName *Name = F->getValueName();
+ unsigned NameLen = Name->getKeyLength();
+ const char *NamePtr = Name->getKeyData();
+
+ // If there is an embedded nul character in the function name, we can never
+ // match it.
+ if (strlen(NamePtr) != NameLen)
+ return UnknownModRefBehavior;
+
+ std::vector<const char*>::iterator Ptr =
+ std::lower_bound(NoMemoryTable->begin(), NoMemoryTable->end(),
+ NamePtr, StringCompare());
+ if (Ptr != NoMemoryTable->end() && strcmp(*Ptr, NamePtr) == 0)
+ return DoesNotAccessMemory;
+
+ Ptr = std::lower_bound(OnlyReadsMemoryTable->begin(),
+ OnlyReadsMemoryTable->end(),
+ NamePtr, StringCompare());
+ if (Ptr != OnlyReadsMemoryTable->end() && strcmp(*Ptr, NamePtr) == 0)
+ return OnlyReadsMemory;
+
+ return UnknownModRefBehavior;
+}
+// Make sure that anything that uses AliasAnalysis pulls in this file...
+DEFINING_FILE_FOR(BasicAliasAnalysis)
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