[llvm] [GVN] MemorySSA for GVN: add optional `AllowMemorySSA` (PR #120982)

[Nikita Popov via llvm-commits]

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@@ -832,7 +838,10 @@ PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
   auto *MemDep =
       isMemDepEnabled() ? &AM.getResult<MemoryDependenceAnalysis>(F) : nullptr;
   auto &LI = AM.getResult<LoopAnalysis>(F);
-  auto *MSSA = AM.getCachedResult<MemorySSAAnalysis>(F);
+  auto *MSSA =
+      isMemorySSAEnabled() ? &AM.getResult<MemorySSAAnalysis>(F) : nullptr;
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nikic wrote:

The change here means that we no longer try to update and preserve an already computed MSSA instance. I've reverted this patch for now.

https://github.com/llvm/llvm-project/pull/120982