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Revert "[DSE] Eliminate noop store even through has clobbering between LoadI and StoreI" 

This reverts commit cd8f3e7581.

Causes miscompiles, see D132657
This commit is contained in:
Arthur Eubanks 2022-10-06 10:29:46 -07:00
parent 5922b92060
commit ae5733346f
3 changed files with 5 additions and 16 deletions
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17
llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -1874,23 +1874,8 @@ struct DSEState {
// We are searching for the definition of the store's destination.
// So, if that is the same definition as the load, then this is a
// noop. Otherwise, fail.
if (LoadAccess != Current) {
// This is a potentially clobbering store, but it writes the same
// value, so we can safely ignore it if alignment is as expected.
if (auto *CurrentDef = cast<MemoryDef>(Current))
if (auto *CurrentStoreI =
dyn_cast_or_null<StoreInst>(CurrentDef->getMemoryInst()))
// Check alignment to ensure load or store does not access at an
// offset.
if (CurrentStoreI->getValueOperand() == LoadI) {
TypeSize StoreSize = DL.getTypeStoreSize(LoadI->getType());
if (!StoreSize.isScalable() &&
std::min(CurrentStoreI->getAlign(), LoadI->getAlign()) >=
StoreSize)
continue;
}
if (LoadAccess != Current)
return false;
}
}
return true;
}

3
llvm/test/Transforms/DeadStoreElimination/noop-stores.ll
View File

@ -672,6 +672,7 @@ define void @store_same_i32_to_mayalias_loc(ptr %q, ptr %p) {
; CHECK-LABEL: @store_same_i32_to_mayalias_loc(
; CHECK-NEXT: [[V:%.*]] = load i32, ptr [[P:%.*]], align 4
; CHECK-NEXT: store i32 [[V]], ptr [[Q:%.*]], align 4
; CHECK-NEXT: store i32 [[V]], ptr [[P]], align 4
; CHECK-NEXT: ret void
;
%v = load i32, ptr %p, align 4
@ -697,6 +698,7 @@ define void @store_same_i12_to_mayalias_loc(ptr %q, ptr %p) {
; CHECK-LABEL: @store_same_i12_to_mayalias_loc(
; CHECK-NEXT: [[V:%.*]] = load i12, ptr [[P:%.*]], align 2
; CHECK-NEXT: store i12 [[V]], ptr [[Q:%.*]], align 2
; CHECK-NEXT: store i12 [[V]], ptr [[P]], align 2
; CHECK-NEXT: ret void
;
%v = load i12, ptr %p, align 2
@ -722,6 +724,7 @@ define void @store_same_ptr_to_mayalias_loc(ptr %q, ptr %p) {
; CHECK-LABEL: @store_same_ptr_to_mayalias_loc(
; CHECK-NEXT: [[V:%.*]] = load ptr, ptr [[P:%.*]], align 8
; CHECK-NEXT: store ptr [[V]], ptr [[Q:%.*]], align 8
; CHECK-NEXT: store ptr [[V]], ptr [[P]], align 8
; CHECK-NEXT: ret void
;
%v = load ptr, ptr %p, align 8

1
llvm/test/Transforms/DeadStoreElimination/stores-of-existing-values.ll
View File

@ -594,6 +594,7 @@ define void @pr49927(ptr %q, ptr %p) {
; CHECK-LABEL: @pr49927(
; CHECK-NEXT: [[V:%.*]] = load i32, ptr [[P:%.*]], align 4
; CHECK-NEXT: store i32 [[V]], ptr [[Q:%.*]], align 4
; CHECK-NEXT: store i32 [[V]], ptr [[P]], align 4
; CHECK-NEXT: ret void
;
%v = load i32, ptr %p, align 4