[llvm] [MemorySSA] Handle MemoryDef optimized away during cloning (PR #117883)

[Alina Sbirlea via llvm-commits]

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@@ -565,24 +565,26 @@ static MemoryAccess *onlySingleValue(MemoryPhi *MP) {
   return MA;
 }
 
-static MemoryAccess *getNewDefiningAccessForClone(MemoryAccess *MA,
-                                                  const ValueToValueMapTy &VMap,
-                                                  PhiToDefMap &MPhiMap,
-                                                  MemorySSA *MSSA) {
+static MemoryAccess *getNewDefiningAccessForClone(
+    MemoryAccess *MA, const ValueToValueMapTy &VMap, PhiToDefMap &MPhiMap,
+    MemorySSA *MSSA, function_ref<bool(BasicBlock *BB)> IsInClonedRegion) {
   MemoryAccess *InsnDefining = MA;
   if (MemoryDef *DefMUD = dyn_cast<MemoryDef>(InsnDefining)) {
-    if (!MSSA->isLiveOnEntryDef(DefMUD)) {
-      Instruction *DefMUDI = DefMUD->getMemoryInst();
-      assert(DefMUDI && "Found MemoryUseOrDef with no Instruction.");
-      if (Instruction *NewDefMUDI =
-              cast_or_null<Instruction>(VMap.lookup(DefMUDI))) {
-        InsnDefining = MSSA->getMemoryAccess(NewDefMUDI);
-        if (!InsnDefining || isa<MemoryUse>(InsnDefining)) {
-          // The clone was simplified, it's no longer a MemoryDef, look up.
-          InsnDefining = getNewDefiningAccessForClone(
-              DefMUD->getDefiningAccess(), VMap, MPhiMap, MSSA);
-        }
-      }
+    if (MSSA->isLiveOnEntryDef(DefMUD))
+      return DefMUD;
+
+    // If the MemoryDef is not part of the cloned region, leave it alone.
+    Instruction *DefMUDI = DefMUD->getMemoryInst();
+    assert(DefMUDI && "Found MemoryUseOrDef with no Instruction.");
+    if (!IsInClonedRegion(DefMUDI->getParent()))
+      return DefMUD;
+
+    auto *NewDefMUDI = cast_or_null<Instruction>(VMap.lookup(DefMUDI));
+    InsnDefining = NewDefMUDI ? MSSA->getMemoryAccess(NewDefMUDI) : nullptr;
----------------
alinas wrote:

Based on the old implementation this should be:
`InsnDefining = NewDefMUDI ? MSSA->getMemoryAccess(NewDefMUDI) : MA;`

https://github.com/llvm/llvm-project/pull/117883