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[DSE,MSSA] Fix crash when using tryToMergePartialOverlappingStores. 

We are re-using tryToMergePartialOverlappingStores, which requires
earlier to domiante Later. In the long run,
tryToMergeParialOverlappingStores should be re-written using MemorySSA.

Fixes PR46513.
This commit is contained in:
Florian Hahn 2020-08-13 11:56:40 +01:00
parent 02e2bd8c4b
commit 3b0878a370
2 changed files with 49 additions and 14 deletions
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33
llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -2249,22 +2249,27 @@ bool eliminateDeadStoresMemorySSA(Function &F, AliasAnalysis &AA,
if (EnablePartialStoreMerging && OR == OW_PartialEarlierWithFullLater) {
auto *Earlier = dyn_cast<StoreInst>(NI);
auto *Later = dyn_cast<StoreInst>(SI);
if (Constant *Merged = tryToMergePartialOverlappingStores(
Earlier, Later, InstWriteOffset, DepWriteOffset, DL, &AA,
&DT)) {
// We are re-using tryToMergePartialOverlappingStores, which requires
// Earlier to domiante Later.
// TODO: implement tryToMergeParialOverlappingStores using MemorySSA.
if (Earlier && Later && DT.dominates(Earlier, Later)) {
if (Constant *Merged = tryToMergePartialOverlappingStores(
Earlier, Later, InstWriteOffset, DepWriteOffset, DL, &AA,
&DT)) {
// Update stored value of earlier store to merged constant.
Earlier->setOperand(0, Merged);
++NumModifiedStores;
MadeChange = true;
// Update stored value of earlier store to merged constant.
Earlier->setOperand(0, Merged);
++NumModifiedStores;
MadeChange = true;
// Remove later store and remove any outstanding overlap intervals
// for the updated store.
State.deleteDeadInstruction(Later);
auto I = State.IOLs.find(Earlier->getParent());
if (I != State.IOLs.end())
I->second.erase(Earlier);
break;
// Remove later store and remove any outstanding overlap intervals
// for the updated store.
State.deleteDeadInstruction(Later);
auto I = State.IOLs.find(Earlier->getParent());
if (I != State.IOLs.end())
I->second.erase(Earlier);
break;
}
}
}

30
llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-overlap.ll
View File

@ -110,3 +110,33 @@ bb9: ; preds = %bb8, %bb7
store double 6.0, double* %tmp3, align 8
ret void
}
; Test case from PR46513. Make sure we do not crash.
; TODO: we should be able to shorten store i32 844283136, i32* %cast.i32 to a
; store of i16.
define void @overlap_no_dominance([4 x i8]* %arg, i1 %c) {
; CHECK-LABEL: @overlap_no_dominance(
; CHECK-NEXT: bb:
; CHECK-NEXT: br i1 [[C:%.*]], label [[BB13:%.*]], label [[BB9:%.*]]
; CHECK: bb9:
; CHECK-NEXT: [[CAST_I32:%.*]] = bitcast [4 x i8]* [[ARG:%.*]] to i32*
; CHECK-NEXT: store i32 844283136, i32* [[CAST_I32]], align 4
; CHECK-NEXT: br label [[BB13]]
; CHECK: bb13:
; CHECK-NEXT: [[CAST_I16:%.*]] = bitcast [4 x i8]* [[ARG]] to i16*
; CHECK-NEXT: store i16 0, i16* [[CAST_I16]], align 4
; CHECK-NEXT: ret void
;
bb:
br i1 %c, label %bb13, label %bb9
bb9: ; preds = %bb
%cast.i32 = bitcast [4 x i8]* %arg to i32*
store i32 844283136, i32* %cast.i32, align 4
br label %bb13
bb13: ; preds = %bb9, %bb
%cast.i16 = bitcast [4 x i8]* %arg to i16*
store i16 0, i16* %cast.i16, align 4
ret void
}