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

[Alina Sbirlea via llvm-commits]

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@@ -3293,16 +3303,18 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
 public:
   static char ID; // Pass identification, replacement for typeid
 
-  explicit GVNLegacyPass(bool NoMemDepAnalysis = !GVNEnableMemDep)
-      : FunctionPass(ID), Impl(GVNOptions().setMemDep(!NoMemDepAnalysis)) {
+  explicit GVNLegacyPass(bool MemDepAnalysis = GVNEnableMemDep,
+                         bool MemSSAAnalysis = GVNEnableMemorySSA)
+      : FunctionPass(ID), Impl(GVNOptions()
+                                   .setMemDep(MemDepAnalysis)
+                                   .setMemorySSA(MemSSAAnalysis)) {
     initializeGVNLegacyPassPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnFunction(Function &F) override {
     if (skipFunction(F))
       return false;
 
-    auto *MSSAWP = getAnalysisIfAvailable<MemorySSAWrapperPass>();
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alinas wrote:

(legacy pass, but..) Keep getAnalysisIfAvailable here; if it's not already available and isMemorySSAEnabled(), then getAnalysis.

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