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[DSE,MSSA] Check if Def is removable only wen we try to remove it.

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Non-removable MemoryDefs can still eliminate other defs. Update the
isRemovable checks to only candidates for removal.
This commit is contained in:
Florian Hahn 2020-06-25 13:31:11 +01:00
parent 6927c576ff
commit d5068f51ec
2 changed files with 4 additions and 5 deletions
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7
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -1535,7 +1535,7 @@ struct DSEState {
auto *MD = dyn_cast_or_null<MemoryDef>(MA);
if (MD && State.MemDefs.size() < MemorySSADefsPerBlockLimit &&
State.getLocForWriteEx(&I) && isRemovable(&I))
State.getLocForWriteEx(&I))
State.MemDefs.push_back(MD);
// Track whether alloca and alloca-like objects are visible in the
@ -1980,7 +1980,8 @@ struct DSEState {
<< "Trying to eliminate MemoryDefs at the end of the function\n");
for (int I = MemDefs.size() - 1; I >= 0; I--) {
MemoryDef *Def = MemDefs[I];
if (SkipStores.find(Def) != SkipStores.end())
if (SkipStores.find(Def) != SkipStores.end() ||
!isRemovable(Def->getMemoryInst()))
continue;
// TODO: Consider doing the underlying object check first, if it is
@ -2069,7 +2070,7 @@ bool eliminateDeadStoresMemorySSA(Function &F, AliasAnalysis &AA,
const Value *SILocUnd = GetUnderlyingObject(SILoc.Ptr, DL);
// Check if the store is a no-op.
if (State.storeIsNoop(KillingDef, SILoc, SILocUnd)) {
if (isRemovable(SI) && State.storeIsNoop(KillingDef, SILoc, SILocUnd)) {
LLVM_DEBUG(dbgs() << "DSE: Remove No-Op Store:\n DEAD: " << *SI << '\n');
State.deleteDeadInstruction(SI);
NumNoopStores++;

2
test/Transforms/DeadStoreElimination/MSSA/simple.ll
View File

@ -700,7 +700,6 @@ define void @test44_volatile(i32* %P) {
define void @test45_volatile(i32* %P) {
; CHECK-LABEL: @test45_volatile(
; CHECK-NEXT: store i32 1, i32* [[P:%.*]], align 4
; CHECK-NEXT: store volatile i32 2, i32* [[P]], align 4
; CHECK-NEXT: store volatile i32 3, i32* [[P]], align 4
; CHECK-NEXT: ret void
@ -714,7 +713,6 @@ define void @test45_volatile(i32* %P) {
define void @test46_volatile(i32* %P) {
; CHECK-LABEL: @test46_volatile(
; CHECK-NEXT: store volatile i32 2, i32* [[P:%.*]], align 4
; CHECK-NEXT: store i32 1, i32* [[P]], align 4
; CHECK-NEXT: store volatile i32 3, i32* [[P]], align 4
; CHECK-NEXT: ret void
;