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use ValueTracking's GetPointerBaseWithConstantOffset() function instead of a local implementation 

llvm-svn: 171307
This commit is contained in:
Nuno Lopes 2012-12-31 17:42:11 +00:00
parent 556b7de2c0
commit 69dcc7deec
1 changed files with 8 additions and 36 deletions
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44
llvm/lib/Analysis/Loads.cpp
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@ -13,6 +13,7 @@
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/DataLayout.h"
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
@ -48,48 +49,19 @@ static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
return false;
}
/// getUnderlyingObjectWithOffset - Strip off up to MaxLookup GEPs and
/// bitcasts to get back to the underlying object being addressed, keeping
/// track of the offset in bytes from the GEPs relative to the result.
/// This is closely related to GetUnderlyingObject but is located
/// here to avoid making VMCore depend on DataLayout.
static Value *getUnderlyingObjectWithOffset(Value *V, const DataLayout *TD,
uint64_t &ByteOffset,
unsigned MaxLookup = 6) {
if (!V->getType()->isPointerTy())
return V;
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
if (!GEP->hasAllConstantIndices())
return V;
SmallVector<Value*, 8> Indices(GEP->op_begin() + 1, GEP->op_end());
ByteOffset += TD->getIndexedOffset(GEP->getPointerOperandType(),
Indices);
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->mayBeOverridden())
return V;
V = GA->getAliasee();
} else {
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
}
return V;
}
/// isSafeToLoadUnconditionally - Return true if we know that executing a load
/// from this value cannot trap. If it is not obviously safe to load from the
/// specified pointer, we do a quick local scan of the basic block containing
/// ScanFrom, to determine if the address is already accessed.
bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
unsigned Align, const DataLayout *TD) {
uint64_t ByteOffset = 0;
int64_t ByteOffset = 0;
Value *Base = V;
if (TD)
Base = getUnderlyingObjectWithOffset(V, TD, ByteOffset);
Base = GetPointerBaseWithConstantOffset(V, ByteOffset, *TD);
if (ByteOffset < 0) // out of bounds
return false;
Type *BaseType = 0;
unsigned BaseAlign = 0;
@ -97,10 +69,10 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
// An alloca is safe to load from as load as it is suitably aligned.
BaseType = AI->getAllocatedType();
BaseAlign = AI->getAlignment();
} else if (const GlobalValue *GV = dyn_cast<GlobalValue>(Base)) {
} else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
// Global variables are safe to load from but their size cannot be
// guaranteed if they are overridden.
if (!isa<GlobalAlias>(GV) && !GV->mayBeOverridden()) {
if (!GV->mayBeOverridden()) {
BaseType = GV->getType()->getElementType();
BaseAlign = GV->getAlignment();
}