[llvm-branch-commits] [llvm] [LICM] Drop per-iteration AA tags (PR #223530)

[Zach Goldthorpe via llvm-branch-commits]

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@@ -2361,13 +2389,31 @@ collectStoresWithInvariantAATags(MemorySSA *MSSA, DominatorTree *DT, Loop *L) {
       StoresByLoc[MemoryLocation::get(SI)].push_back(SI);
   });
 
+  // A scope declared inside the loop denotes a different scope on each
+  // iteration, so it cannot support the cross-iteration check below.
+  std::optional<SmallPtrSet<const MDNode *, 4>> LoopLocalAliasScopes;
+  auto HasLoopLocalAliasScope = [&](const AAMDNodes &AATags) {
+    if (!AATags.Scope && !AATags.NoAlias)
+      return false;
+    if (!LoopLocalAliasScopes)
+      LoopLocalAliasScopes = collectLoopLocalAliasScopes(L);
+    return hasAnyOperandsFrom(AATags.Scope, *LoopLocalAliasScopes) ||
+           hasAnyOperandsFrom(AATags.NoAlias, *LoopLocalAliasScopes);
+  };
+
   // This only looks at explicit exiting blocks. If we ever start sinking
   // stores into unwind edges, this will break.
   SmallVector<BasicBlock *, 4> ExitingBlocks;
   L->getExitingBlocks(ExitingBlocks);
 
   SmallPtrSet<const StoreInst *, 8> StoresWithInvariantAATags;
-  for (const auto &Stores : llvm::make_second_range(StoresByLoc)) {
+  for (const auto &Pair : StoresByLoc) {
+    const MemoryLocation &Loc = Pair.first;
+    const SmallVector<const StoreInst *, 1> &Stores = Pair.second;
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zGoldthorpe wrote:

Unfortunately, using a structured binding within a lambda is a C++20 extension, so this was the best I could do instead...

https://github.com/llvm/llvm-project/pull/223530