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Merge commit 28a2b85602a5 from llvm-project (by Kazu Hirata):

Browse source 
[DeadStoreElimination] Use SmallSetVector (NFC) (#79410)

  The use of SmallSetVector saves 0.58% of heap allocations during the
  compilation of a large preprocessed file, namely X86ISelLowering.cpp,
  for the X86 target.  During the experiment, the final size of ToCheck
  was 8 or less 88% of the time.

Merge commit 9e95c4947d31 from llvm-project (by Nikita Popov):

  [DSE] Fix non-determinism due to address reuse (#84943)

  The malloc->calloc fold creates a new MemoryAccess, which may end of at
  the same address as a previously deleted access inside SkipStores.

  To the most part, this is not a problem, because SkipStores is normally
  only used together with MemDefs. Neither the old malloc access nor the
  new calloc access will be part of MemDefs, so there is no problem here.

  However, SkipStores is also used in one more place: In the main DSE
  loop, ToCheck entries are checked against it. Fix this by not using
  SkipStores here, and instead using a separate set to track deletions
  inside this loop. This way it is not affected by the calloc optimization
  that happens outside it.

  This is all pretty ugly, but I haven't found another good way to fix it.
  Suggestions welcome.

  No test case as I don't have a reliable DSE-only test-case for this.

  Fixes https://github.com/llvm/llvm-project/issues/84458.

This fixes another possible difference in output when building i386
object files with a native or cross build of clang. (Specifically, the
file sbin/ipf/ipmon/ipmon.o.)

PR:		276961
Reported by:	cperciva
MFC after:	3 days
This commit is contained in:
Dimitry Andric 2024-07-25 13:13:45 +02:00
parent 9565854ab4
commit 55a2a91c5e
1 changed files with 18 additions and 6 deletions
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24
contrib/llvm-project/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View file

@ -1697,7 +1697,9 @@ struct DSEState {
/// Delete dead memory defs and recursively add their operands to ToRemove if
/// they became dead.
void deleteDeadInstruction(Instruction *SI) {
void
deleteDeadInstruction(Instruction *SI,
SmallPtrSetImpl<MemoryAccess *> *Deleted = nullptr) {
MemorySSAUpdater Updater(&MSSA);
SmallVector<Instruction *, 32> NowDeadInsts;
NowDeadInsts.push_back(SI);
@ -1718,6 +1720,8 @@ struct DSEState {
if (IsMemDef) {
auto *MD = cast<MemoryDef>(MA);
SkipStores.insert(MD);
if (Deleted)
Deleted->insert(MD);
if (auto *SI = dyn_cast<StoreInst>(MD->getMemoryInst())) {
if (SI->getValueOperand()->getType()->isPointerTy()) {
const Value *UO = getUnderlyingObject(SI->getValueOperand());
@ -2111,7 +2115,12 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
unsigned WalkerStepLimit = MemorySSAUpwardsStepLimit;
unsigned PartialLimit = MemorySSAPartialStoreLimit;
// Worklist of MemoryAccesses that may be killed by KillingDef.
SetVector<MemoryAccess *> ToCheck;
SmallSetVector<MemoryAccess *, 8> ToCheck;
// Track MemoryAccesses that have been deleted in the loop below, so we can
// skip them. Don't use SkipStores for this, which may contain reused
// MemoryAccess addresses.
SmallPtrSet<MemoryAccess *, 8> Deleted;
[[maybe_unused]] unsigned OrigNumSkipStores = State.SkipStores.size();
ToCheck.insert(KillingDef->getDefiningAccess());
bool Shortend = false;
@ -2119,7 +2128,7 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
// Check if MemoryAccesses in the worklist are killed by KillingDef.
for (unsigned I = 0; I < ToCheck.size(); I++) {
MemoryAccess *Current = ToCheck[I];
if (State.SkipStores.count(Current))
if (Deleted.contains(Current))
continue;
std::optional<MemoryAccess *> MaybeDeadAccess = State.getDomMemoryDef(
@ -2166,7 +2175,7 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
continue;
LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: " << *DeadI
<< "\n KILLER: " << *KillingI << '\n');
State.deleteDeadInstruction(DeadI);
State.deleteDeadInstruction(DeadI, &Deleted);
++NumFastStores;
MadeChange = true;
} else {
@ -2203,7 +2212,7 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
Shortend = true;
// Remove killing store and remove any outstanding overlap
// intervals for the updated store.
State.deleteDeadInstruction(KillingSI);
State.deleteDeadInstruction(KillingSI, &Deleted);
auto I = State.IOLs.find(DeadSI->getParent());
if (I != State.IOLs.end())
I->second.erase(DeadSI);
@ -2215,13 +2224,16 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
if (OR == OW_Complete) {
LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: " << *DeadI
<< "\n KILLER: " << *KillingI << '\n');
State.deleteDeadInstruction(DeadI);
State.deleteDeadInstruction(DeadI, &Deleted);
++NumFastStores;
MadeChange = true;
}
}
}
assert(State.SkipStores.size() - OrigNumSkipStores == Deleted.size() &&
"SkipStores and Deleted out of sync?");
// Check if the store is a no-op.
if (!Shortend && State.storeIsNoop(KillingDef, KillingUndObj)) {
LLVM_DEBUG(dbgs() << "DSE: Remove No-Op Store:\n DEAD: " << *KillingI