[llvm] [DAGCombiner] cache negative result from getMergeStoreCandidates() (PR #106949)

[Princeton Ferro via llvm-commits]

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@@ -191,6 +191,11 @@ namespace {
     // AA - Used for DAG load/store alias analysis.
     AliasAnalysis *AA;
 
+    /// This caches all chains that have already been processed in
+    /// DAGCombiner::getStoreMergeCandidates() and found to have no mergeable
+    /// stores candidates.
+    SmallSet<SDNode *, 32> ChainsWithoutMergeableStores;
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Prince781 wrote:

Okay. Maybe 4 or 8 would be better?

https://github.com/llvm/llvm-project/pull/106949