[DeadStoreElimination] Use SmallSetVector (NFC)

[kazutakahirata]

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.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Kazu Hirata (kazutakahirata)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/79410.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp (+1-1)

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 11a91bfbe5baff..663c06ebafb5f4 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -2096,7 +2096,7 @@ 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;
     ToCheck.insert(KillingDef->getDefiningAccess());
 
     bool Shortend = false;

[fhahn]

LGTM, thanks!