#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
-#include "llvm/ParameterAttributes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.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/ADT/STLExtras.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
-#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/ErrorHandling.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;
+}
+
+
+/// isObjectSmallerThan - Return true if we can prove that the object specified
+/// by V is smaller than Size.
+static bool isObjectSmallerThan(const Value *V, unsigned 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->getOperand(1)))
+ 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
/// 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 VISIBILITY_HIDDEN NoAA : public ImmutablePass, public AliasAnalysis {
+ struct 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) { }
+ NoAA() : ImmutablePass(&ID) {}
+ explicit NoAA(void *PID) : ImmutablePass(PID) { }
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<TargetData>();
}
virtual void initializePass() {
- TD = &getAnalysis<TargetData>();
+ TD = getAnalysisIfAvailable<TargetData>();
}
virtual AliasResult alias(const Value *V1, unsigned V1Size,
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!");
+ llvm_unreachable("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 ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
return ModRef;
virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
return ModRef;
}
- virtual bool hasNoModRefInfoForCalls() const { return true; }
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
+//===----------------------------------------------------------------------===//
+// BasicAA Pass
+//===----------------------------------------------------------------------===//
+
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 VISIBILITY_HIDDEN BasicAliasAnalysis : public NoAA {
+ struct BasicAliasAnalysis : public NoAA {
static char ID; // Class identification, replacement for typeinfo
- BasicAliasAnalysis() : NoAA((intptr_t)&ID) { }
+ BasicAliasAnalysis() : NoAA(&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);
+ 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;
}
- /// hasNoModRefInfoForCalls - We can provide mod/ref information against
- /// non-escaping allocations.
- virtual bool hasNoModRefInfoForCalls() const { return false; }
+ 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:
- // 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,
- Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1Size,
- const Type *BasePtr2Ty,
- Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size);
+ // 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);
};
} // End of anonymous namespace
return new BasicAliasAnalysis();
}
-/// getUnderlyingObject - This traverses the use chain to figure out what object
-/// the specified value points to. If the value points to, or is derived from,
-/// a unique object or an argument, return it. This returns:
-/// Arguments, GlobalVariables, Functions, Allocas, Mallocs.
-static const Value *getUnderlyingObject(const Value *V) {
- if (!isa<PointerType>(V->getType())) 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<BitCastInst>(I) || isa<GetElementPtrInst>(I))
- return getUnderlyingObject(I->getOperand(0));
- } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::BitCast ||
- CE->getOpcode() == Instruction::GetElementPtr)
- return getUnderlyingObject(CE->getOperand(0));
- }
- return V;
-}
-
-static const User *isGEP(const Value *V) {
- if (isa<GetElementPtrInst>(V) ||
- (isa<ConstantExpr>(V) &&
- cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
- return cast<User>(V);
- return 0;
-}
-
-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());
-
- // Accumulate all of the chained indexes into the operand array
- V = cast<User>(V)->getOperand(0);
-
- while (const User *G = isGEP(V)) {
- if (!isa<Constant>(GEPOps[0]) || isa<GlobalValue>(GEPOps[0]) ||
- !cast<Constant>(GEPOps[0])->isNullValue())
- break; // Don't handle folding arbitrary pointer offsets yet...
- GEPOps.erase(GEPOps.begin()); // Drop the zero index
- GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end());
- V = G->getOperand(0);
- }
- return V;
-}
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
if (const GlobalVariable *GV =
- dyn_cast<GlobalVariable>(getUnderlyingObject(P)))
+ 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;
}
-// 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; //next use.
- case Instruction::Store:
- if (I->getOperand(0) == V)
- return true; // Escapes if the pointer is stored.
- break; // next use.
- case Instruction::GetElementPtr:
- if (AddressMightEscape(I))
- return true;
- break; // next use.
- case Instruction::BitCast:
- 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; // next use
- case Instruction::Call:
- // If the call is to a few known safe intrinsics, we know that it does
- // not escape
- if (!isa<MemIntrinsic>(I))
- return true;
- break; // next use
- default:
- return true;
- }
- }
- 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.
-//
+/// 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) {
- if (!isa<Constant>(P)) {
- const Value *Object = getUnderlyingObject(P);
-
- // 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;
+ 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;
+ }
+ }
- // Allocations and byval arguments are "new" objects.
- if (isa<AllocationInst>(Object) || isa<Argument>(Object)) {
- // Okay, the pointer is to a stack allocated (or effectively so, for
- // for noalias parameters) object. If the address of this object doesn't
- // escape from this function body to a callee, then we know that no
- // callees can mod/ref it unless they are actually passed it.
- if (isa<AllocationInst>(Object) ||
- cast<Argument>(Object)->hasByValAttr() ||
- cast<Argument>(Object)->hasNoAliasAttr())
- if (!AddressMightEscape(Object)) {
- bool passedAsArg = false;
- for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
- CI != CE; ++CI)
- if (isa<PointerType>((*CI)->getType()) &&
- (getUnderlyingObject(*CI) == P ||
- alias(cast<Value>(CI), ~0U, P, ~0U) != NoAlias))
- passedAsArg = true;
-
- if (!passedAsArg)
- return NoModRef;
- }
+ 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);
}
-/// isIdentifiedObject - Return true if this pointer refers to a distinct and
-/// identifiable object. This returns true for:
-/// Global Variables and Functions
-/// Allocas and Mallocs
-/// ByVal and NoAlias Arguments
-///
-static bool isIdentifiedObject(const Value *V) {
- if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
- return true;
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasNoAliasAttr() || A->hasByValAttr();
- return false;
-}
-/// 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;
+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;
- // 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;
+ 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);
}
-/// 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<AllocationInst>(V))
- return !AddressMightEscape(V);
+/// GetIndiceDifference - 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) {
+ 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;
+
+ // 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 this is an argument that corresponds to a byval or noalias argument,
- // it can't escape either.
- if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr() || A->hasNoAliasAttr())
- return !AddressMightEscape(V);
- return false;
+ // 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;
+ 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)
+ Dest.push_back(std::make_pair(V, -Scale));
+ }
}
+/// 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, unsigned V1Size,
+ const Value *V2, unsigned V2Size,
+ const Value *UnderlyingV1,
+ const Value *UnderlyingV2) {
+ int64_t GEP1BaseOffset;
+ SmallVector<std::pair<const Value*, int64_t>, 4> GEP1VariableIndices;
-/// isObjectSmallerThan - Return true if we can prove that the object specified
-/// by V is smaller than Size.
-static bool isObjectSmallerThan(const Value *V, unsigned Size,
- const TargetData &TD) {
- const Type *AccessTy = 0;
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
- AccessTy = GV->getType()->getElementType();
-
- if (const AllocationInst *AI = dyn_cast<AllocationInst>(V))
- if (!AI->isArrayAllocation())
- AccessTy = AI->getType()->getElementType();
+ // 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);
+
+ // 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<std::pair<const Value*, int64_t>, 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;
+ GetIndiceDifference(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 (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr())
- AccessTy = cast<PointerType>(A->getType())->getElementType();
+ // If both accesses are unknown size, we can't do anything useful here.
+ if (V1Size == ~0U && V2Size == ~0U)
+ return MayAlias;
+
+ AliasResult R = aliasCheck(UnderlyingV1, ~0U, 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
+ // 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;
+ }
+ }
- if (AccessTy && AccessTy->isSized())
- return TD.getABITypeSize(AccessTy) < Size;
- return false;
+ // 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].second)
+ GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].second;
+
+ // If our known offset is bigger than the access size, we know we don't have
+ // an alias.
+ if (GEP1BaseOffset) {
+ if (GEP1BaseOffset >= (int64_t)V2Size ||
+ GEP1BaseOffset <= -(int64_t)V1Size)
+ return NoAlias;
+ }
+
+ return MayAlias;
}
-// 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. :)
+/// aliasSelect - Provide a bunch of ad-hoc rules to disambiguate a Select
+/// instruction against another.
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::aliasSelect(const SelectInst *SI, unsigned SISize,
+ const Value *V2, unsigned V2Size) {
+ // 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,
+ SI2->getTrueValue(), V2Size);
+ if (Alias == MayAlias)
+ return MayAlias;
+ AliasResult ThisAlias =
+ aliasCheck(SI->getFalseValue(), SISize,
+ SI2->getFalseValue(), V2Size);
+ 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(SI->getTrueValue(), SISize, V2, V2Size);
+ if (Alias == MayAlias)
+ return MayAlias;
+ AliasResult ThisAlias =
+ aliasCheck(SI->getFalseValue(), SISize, V2, V2Size);
+ 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, unsigned PNSize,
+ const Value *V2, unsigned V2Size) {
+ // The PHI node has already been visited, avoid recursion any further.
+ if (!VisitedPHIs.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,
+ PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)),
+ V2Size);
+ if (Alias == MayAlias)
+ return MayAlias;
+ for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
+ AliasResult ThisAlias =
+ aliasCheck(PN->getIncomingValue(i), PNSize,
+ PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
+ V2Size);
+ 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, V1Srcs[0], PNSize);
+ // 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 a PHI, 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);
+
+ AliasResult ThisAlias = aliasCheck(V2, V2Size, V, PNSize);
+ 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::alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- // Strip off any constant expression casts if they exist
- if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V1))
- if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
- V1 = CE->getOperand(0);
- if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V2))
- if (CE->isCast() && isa<PointerType>(CE->getOperand(0)->getType()))
- V2 = CE->getOperand(0);
+BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ // 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())) &&
- V1->getType() != Type::Int64Ty && V2->getType() != Type::Int64Ty)
+ if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
return NoAlias; // Scalars cannot alias each other
- // Strip off cast instructions...
- 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 = V1->getUnderlyingObject();
+ const Value *O2 = V2->getUnderlyingObject();
- // Figure out what objects these things are pointing to if we can...
- const Value *O1 = getUnderlyingObject(V1);
- const Value *O2 = getUnderlyingObject(V2);
+ // 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;
-
- // Incoming argument cannot alias locally allocated object!
- if ((isa<Argument>(O1) && isa<AllocationInst>(O2)) ||
- (isa<Argument>(O2) && isa<AllocationInst>(O1)))
+
+ // 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.
+ 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 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.
- const TargetData &TD = getTargetData();
- if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, TD)) ||
- (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, TD)))
- return NoAlias;
+ if (TD)
+ if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, *TD)) ||
+ (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, *TD)))
+ return NoAlias;
- // If one pointer is the result of a call/invoke and the other is a
+ // 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.
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
- isNonEscapingLocalObject(O2))
- return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
- isNonEscapingLocalObject(O1))
- return NoAlias;
-
- // 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.
- // Note that we also handle chains of getelementptr instructions as well as
- // constant expression getelementptrs here.
- //
- if (isGEP(V1) && isGEP(V2)) {
- // Drill down into the first non-gep value, to test for must-aliasing of
- // the base pointers.
- const User *G = cast<User>(V1);
- while (isGEP(G->getOperand(0)) &&
- G->getOperand(1) ==
- Constant::getNullValue(G->getOperand(1)->getType()))
- G = cast<User>(G->getOperand(0));
- const Value *BasePtr1 = G->getOperand(0);
-
- G = cast<User>(V2);
- while (isGEP(G->getOperand(0)) &&
- G->getOperand(1) ==
- Constant::getNullValue(G->getOperand(1)->getType()))
- G = cast<User>(G->getOperand(0));
- const Value *BasePtr2 = G->getOperand(0);
-
- // Do the base pointers alias?
- 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
- // figure out anything about the resultant pointers, to try to prove
- // non-aliasing.
-
- // Collect all of the chained GEP operands together into one simple place
- SmallVector<Value*, 16> GEP1Ops, GEP2Ops;
- BasePtr1 = GetGEPOperands(V1, GEP1Ops);
- BasePtr2 = GetGEPOperands(V2, GEP2Ops);
-
- // 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;
- }
- }
+ // 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;
}
- // Check to see if these two pointers are related by a getelementptr
- // instruction. If one pointer is a GEP with a non-zero index of the other
- // pointer, we know they cannot alias.
- //
- if (isGEP(V2)) {
+ // 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))
+ return aliasGEP(GV1, V1Size, V2, V2Size, O1, O2);
- if (V1Size != ~0U && V2Size != ~0U)
- if (isGEP(V1)) {
- SmallVector<Value*, 16> GEPOperands;
- const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
-
- AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
- if (R == MustAlias) {
- // If there is at least one non-zero constant index, we know they cannot
- // alias.
- bool ConstantFound = false;
- bool AllZerosFound = true;
- for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
- if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
- if (!C->isNullValue()) {
- ConstantFound = true;
- AllZerosFound = false;
- break;
- }
- } else {
- AllZerosFound = false;
- }
-
- // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
- // the ptr, the end result is a must alias also.
- if (AllZerosFound)
- return MustAlias;
-
- 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...
- 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;
-}
-
-// 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, 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, 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 PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
-
- // Find the (possibly empty) initial sequence of equal values... which are not
- // necessarily constants.
- unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
- unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
- unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
- unsigned UnequalOper = 0;
- while (UnequalOper != MinOperands &&
- IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
- // Advance through the type as we go...
- ++UnequalOper;
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
- BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[UnequalOper-1]);
- else {
- // If all operands equal each other, then the derived pointers must
- // alias each other...
- BasePtr1Ty = 0;
- assert(UnequalOper == NumGEP1Operands && UnequalOper == NumGEP2Operands &&
- "Ran out of type nesting, but not out of operands?");
- return MustAlias;
- }
- }
-
- // If we have seen all constant operands, and run out of indexes on one of the
- // getelementptrs, check to see if the tail of the leftover one is all zeros.
- // If so, return mustalias.
- if (UnequalOper == MinOperands) {
- 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]) ||
- !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.
-
- // Scan for the first operand that is constant and unequal in the
- // two getelementptrs...
- unsigned FirstConstantOper = UnequalOper;
- 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<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.
- 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) {
- // 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.
- // However, one GEP may have more operands than the other. If this is the
- // 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 (NumGEP1Ops < NumGEP2Ops) {
- std::swap(GEP1Ops, GEP2Ops);
- std::swap(NumGEP1Ops, NumGEP2Ops);
- }
-
- // Is there anything to check?
- if (NumGEP1Ops > MinOperands) {
- for (unsigned i = FirstConstantOper; i != MaxOperands; ++i)
- 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 suitable for
- // TargetData::getIndexedOffset.
- for (i = 0; i != MaxOperands; ++i)
- if (!isa<ConstantInt>(GEP1Ops[i]))
- GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
- // 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,
- NumGEP1Ops);
-
- // Now check without any constants at the end.
- int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
- MinOperands);
-
- // Make sure we compare the absolute difference.
- if (Offset1 > Offset2)
- std::swap(Offset1, Offset2);
-
- // If the tail provided a bit enough offset, return noalias!
- if ((uint64_t)(Offset2-Offset1) >= SizeMax)
- return NoAlias;
- // Otherwise break - we don't look for another constant in the tail.
- break;
- }
- }
-
- // Couldn't find anything useful.
- return MayAlias;
- }
-
- // If there are non-equal constants arguments, then we can figure
- // out a minimum known delta between the two index expressions... at
- // this point we know that the first constant index of GEP1 is less
- // 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]);
-
- // 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 sequence of array subscripts into constant zeros to start with.
- const Type *ZeroIdxTy = GEPPointerTy;
- for (unsigned i = 0; i != FirstConstantOper; ++i) {
- 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]);
+ if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
}
+ if (const PHINode *PN = dyn_cast<PHINode>(V1))
+ return aliasPHI(PN, V1Size, V2, V2Size);
- // 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 < 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<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->getZExtValue() >= AT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- } else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty)) {
- if (Op1C->getZExtValue() >= VT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- }
-
- } else {
- // GEP1 is known to produce a value less than GEP2. To be
- // conservatively correct, we must assume the largest possible
- // constant is used in this position. This cannot be the initial
- // index to the GEP instructions (because we know we have at least one
- // element before this one with the different constant arguments), so
- // we know that the current index must be into either a struct or
- // array. Because we know it's not constant, this cannot be a
- // structure index. Because of this, we can calculate the maximum
- // value possible.
- //
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
- 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>(BasePtr2Ty)) {
- if (Op2C->getZExtValue() >= AT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- } else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr2Ty)) {
- 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());
- }
- }
- }
-
- if (BasePtr1Ty && Op1) {
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
- BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[i]);
- else
- BasePtr1Ty = 0;
- }
-
- if (BasePtr2Ty && Op2) {
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr2Ty))
- BasePtr2Ty = CT->getTypeAtIndex(GEP2Ops[i]);
- else
- BasePtr2Ty = 0;
- }
+ if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
}
+ if (const SelectInst *S1 = dyn_cast<SelectInst>(V1))
+ return aliasSelect(S1, V1Size, V2, V2Size);
- 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;
}
-// Make sure that anything that uses AliasAnalysis pulls in this file...
+// Make sure that anything that uses AliasAnalysis pulls in this file.
DEFINING_FILE_FOR(BasicAliasAnalysis)