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[DSE] Use same logic as legacy impl to check if free kills a location.

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This patch updates DSE + MemorySSA to use the same check as the legacy
implementation to determine if a location is killed by a free call.

This changes the existing behavior so that a free does not kill
locations before the start of the freed pointer.

This should fix PR48036.
This commit is contained in:
Florian Hahn 2020-10-31 19:30:19 +00:00
parent cdee713390
commit dc7616bd85
2 changed files with 9 additions and 2 deletions
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8
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -1857,9 +1857,13 @@ struct DSEState {
getUnderlyingObject(MaybeTermLoc->first.Ptr))
return false;
auto TermLoc = MaybeTermLoc->first;
if (MaybeTermLoc->second) {
const Value *LocUO = getUnderlyingObject(Loc.Ptr);
return BatchAA.isMustAlias(TermLoc.Ptr, LocUO);
}
int64_t InstWriteOffset, DepWriteOffset;
return MaybeTermLoc->second ||
isOverwrite(MaybeTerm, AccessI, MaybeTermLoc->first, Loc, DL, TLI,
return isOverwrite(MaybeTerm, AccessI, TermLoc, Loc, DL, TLI,
DepWriteOffset, InstWriteOffset, BatchAA,
&F) == OW_Complete;
}

3
test/Transforms/DeadStoreElimination/MSSA/free.ll
View File

@ -90,9 +90,12 @@ bb:
; Test case inspired by PR48036.
define void @delete_field_after(%struct* %ptr) {
;
; CHECK-LABEL: @delete_field_after(
; CHECK-NEXT: [[PTR_F0:%.*]] = getelementptr [[STRUCT:%.*]], %struct* [[PTR:%.*]], i32 1
; CHECK-NEXT: [[BC:%.*]] = bitcast %struct* [[PTR_F0]] to i8*
; CHECK-NEXT: [[PTR_F1:%.*]] = getelementptr [[STRUCT]], %struct* [[PTR]], i32 0, i32 1
; CHECK-NEXT: store i32 0, i32* [[PTR_F1]], align 4
; CHECK-NEXT: call void @free(i8* [[BC]])
; CHECK-NEXT: ret void
;