[llvm] Reapply "[GVN] MemorySSA for GVN: add optional AllowMemorySSA" (PR #122482)

[Antonio Frighetto via llvm-commits]

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@@ -833,6 +839,8 @@ PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
       isMemDepEnabled() ? &AM.getResult<MemoryDependenceAnalysis>(F) : nullptr;
   auto &LI = AM.getResult<LoopAnalysis>(F);
   auto *MSSA = AM.getCachedResult<MemorySSAAnalysis>(F);
+  if (isMemorySSAEnabled() && !MSSA)
+    MSSA = &AM.getResult<MemorySSAAnalysis>(F);
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antoniofrighetto wrote:

That makes sense, updated, thanks!

https://github.com/llvm/llvm-project/pull/122482