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[ConstantFold] Fix GEP of GEP fold with opaque pointers

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This was previously combining indices even though they operate on
different types. For non-opaque pointers, the condition is
automatically satisfied based on the pointer types being equal.
This commit is contained in:
Nikita Popov 2021-07-23 23:56:41 +02:00
parent 140985f91f
commit c2a36153e1
2 changed files with 12 additions and 2 deletions
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7
lib/IR/ConstantFold.cpp
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@ -2347,8 +2347,11 @@ static bool isIndexInRangeOfArrayType(uint64_t NumElements,
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
static Constant *foldGEPOfGEP(GEPOperator *GEP, bool InBounds,
static Constant *foldGEPOfGEP(GEPOperator *GEP, Type *PointeeTy, bool InBounds,
ArrayRef<Value *> Idxs) {
if (PointeeTy != GEP->getResultElementType())
return nullptr;
Constant *Idx0 = cast<Constant>(Idxs[0]);
if (Idx0->isNullValue()) {
// Handle the simple case of a zero index.
@ -2491,7 +2494,7 @@ Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (auto *GEP = dyn_cast<GEPOperator>(CE))
if (Constant *C = foldGEPOfGEP(GEP, InBounds, Idxs))
if (Constant *C = foldGEPOfGEP(GEP, PointeeTy, InBounds, Idxs))
return C;
// Attempt to fold casts to the same type away. For example, folding:

7
test/Other/force-opaque-ptrs.ll
View File

@ -64,6 +64,13 @@ define void @remangle_intrinsic() {
ret void
}
define i32* @constexpr_gep() {
; CHECK-LABEL: define {{[^@]+}}@constexpr_gep() {
; CHECK-NEXT: ret ptr getelementptr (i32, ptr getelementptr (i8, ptr null, i64 4), i64 1)
;
ret i32* getelementptr(i32, i32* bitcast (i8* getelementptr (i8, i8* null, i64 4) to i32*), i64 1)
}
declare i8* @llvm.stacksave()
declare void @llvm.stackprotector(i8*, i8**)
declare <2 x i64> @llvm.masked.expandload.v2i64(i64*, <2 x i1>, <2 x i64>)