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Add support for constant folding the 'offsetof' pattern even if the

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base is not zero.  This fixes test/C++Frontend/2008-05-07-CrazyOffsetOf.cpp


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50840 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-05-08 04:54:43 +00:00
parent 7e2ff77ef0
commit 268e7d7a94
1 changed files with 23 additions and 16 deletions
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39
lib/Analysis/ConstantFolding.cpp
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@ -122,25 +122,32 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
const Type *ResultTy,
const TargetData *TD) {
Constant *Ptr = Ops[0];
if (!cast<PointerType>(Ptr->getType())->getElementType()->isSized())
if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
return 0;
if (TD && Ptr->isNullValue()) {
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
bool isFoldableGEP = true;
for (unsigned i = 1; i != NumOps; ++i)
if (!isa<ConstantInt>(Ops[i])) {
isFoldableGEP = false;
break;
}
if (isFoldableGEP) {
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1);
Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset);
return ConstantExpr::getIntToPtr(C, ResultTy);
}
uint64_t BasePtr = 0;
if (!Ptr->isNullValue()) {
// If this is a inttoptr from a constant int, we can fold this as the base,
// otherwise we can't.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::IntToPtr)
if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
BasePtr = Base->getZExtValue();
if (BasePtr == 0)
return 0;
}
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
for (unsigned i = 1; i != NumOps; ++i)
if (!isa<ConstantInt>(Ops[i]))
return false;
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1);
Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset+BasePtr);
return ConstantExpr::getIntToPtr(C, ResultTy);
return 0;
}