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Revert "[InstCombine] Check inbounds in load/store of gep null transform (PR48577)" 

This reverts commit 899faa50f2.

Upon further consideration, this does not fix the right issue.
Doing this fold for non-inbounds GEPs is legal, because the
resulting pointer is still based-on null, which has no associated
address range, and as such and access to it is UB.

https://bugs.llvm.org/show_bug.cgi?id=48577#c3
This commit is contained in:
Nikita Popov 2020-12-24 12:34:14 +01:00
parent e0751234ef
commit ef2f843347
3 changed files with 5 additions and 7 deletions
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3
llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -908,7 +908,6 @@ static bool canSimplifyNullStoreOrGEP(StoreInst &SI) {
auto *Ptr = SI.getPointerOperand();
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr))
if (GEPI->isInBounds())
Ptr = GEPI->getOperand(0);
return (isa<ConstantPointerNull>(Ptr) &&
!NullPointerIsDefined(SI.getFunction(), SI.getPointerAddressSpace()));
@ -917,7 +916,7 @@ static bool canSimplifyNullStoreOrGEP(StoreInst &SI) {
static bool canSimplifyNullLoadOrGEP(LoadInst &LI, Value *Op) {
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
const Value *GEPI0 = GEPI->getOperand(0);
if (isa<ConstantPointerNull>(GEPI0) && GEPI->isInBounds() &&
if (isa<ConstantPointerNull>(GEPI0) &&
!NullPointerIsDefined(LI.getFunction(), GEPI->getPointerAddressSpace()))
return true;
}

5
llvm/test/Transforms/InstCombine/load.ll
View File

@ -69,9 +69,8 @@ define i32 @load_gep_null_inbounds(i64 %X) {
define i32 @load_gep_null_not_inbounds(i64 %X) {
; CHECK-LABEL: @load_gep_null_not_inbounds(
; CHECK-NEXT: [[V:%.*]] = getelementptr i32, i32* null, i64 [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = load i32, i32* [[V]], align 4
; CHECK-NEXT: ret i32 [[R]]
; CHECK-NEXT: store i32 undef, i32* null, align 536870912
; CHECK-NEXT: ret i32 undef
;
%V = getelementptr i32, i32* null, i64 %X
%R = load i32, i32* %V

2
llvm/test/Transforms/InstCombine/store.ll
View File

@ -37,7 +37,7 @@ define void @store_at_gep_off_null_inbounds(i64 %offset) {
define void @store_at_gep_off_null_not_inbounds(i64 %offset) {
; CHECK-LABEL: @store_at_gep_off_null_not_inbounds(
; CHECK-NEXT: [[PTR:%.*]] = getelementptr i32, i32* null, i64 [[OFFSET:%.*]]
; CHECK-NEXT: store i32 24, i32* [[PTR]], align 4
; CHECK-NEXT: store i32 undef, i32* [[PTR]], align 4
; CHECK-NEXT: ret void
;
%ptr = getelementptr i32, i32 *null, i64 %offset