/// fold the result. If not, this returns null.
Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
const TargetData *TD, const DominatorTree *) {
+ // The type of the GEP pointer operand.
+ const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType());
+
// getelementptr P -> P.
if (NumOps == 1)
return Ops[0];
- // TODO.
- //if (isa<UndefValue>(Ops[0]))
- // return UndefValue::get(GEP.getType());
+ if (isa<UndefValue>(Ops[0])) {
+ // Compute the (pointer) type returned by the GEP instruction.
+ const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1],
+ NumOps-1);
+ const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
+ return UndefValue::get(GEPTy);
+ }
if (NumOps == 2) {
// getelementptr P, 0 -> P.
return Ops[0];
// getelementptr P, N -> P if P points to a type of zero size.
if (TD) {
- const Type *Ty = cast<PointerType>(Ops[0]->getType())->getElementType();
+ const Type *Ty = PtrTy->getElementType();
if (Ty->isSized() && !TD->getTypeAllocSize(Ty))
return Ops[0];
}
Value *PtrOp = GEP.getOperand(0);
- if (isa<UndefValue>(GEP.getOperand(0)))
- return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
-
// Eliminate unneeded casts for indices.
if (TD) {
bool MadeChange = false;