[llvm] [GlobalOpt] Handle operators separately when removing GV users (PR #84694)

[Eli Friedman via llvm-commits]

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@@ -318,11 +240,30 @@ static bool CleanupConstantGlobalUsers(GlobalVariable *GV,
         }
       }
     } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
-      // Store must be unreachable or storing Init into the global.
-      EraseFromParent(SI);
-    } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
-      if (getUnderlyingObject(MI->getRawDest()) == GV)
-        EraseFromParent(MI);
+      auto *V = SI->getValueOperand();
+      if (isa<Constant>(V)) {
+        EraseFromParent(SI);
+      } else if (isa<Instruction>(V)) {
+        EraseFromParent(SI);
+        if (isSafeComputationToRemove(V, GetTLI))
+          RecursivelyDeleteTriviallyDeadInstructions(V);
+      } else if (isa<Argument>(V)) {
+        if (!V->getType()->isPointerTy())
+          EraseFromParent(SI);
+      }
+    } else if (auto *MSI = dyn_cast<MemSetInst>(U)) { // memset/cpy/mv
+      if (getUnderlyingObject(MSI->getRawDest()) == GV)
+        EraseFromParent(MSI);
+    } else if (auto *MTI = dyn_cast<MemTransferInst>(U)) {
+      auto *Src = MTI->getRawSource();
+      auto *Dst = MTI->getRawDest();
+      if (getUnderlyingObject(Dst) != GV)
+        continue;
+      if (isa<Instruction, Operator>(Src)) {
+        EraseFromParent(MTI);
+        if (isSafeComputationToRemove(Src, GetTLI))
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efriedma-quic wrote:

I was trying to say that you can just call RecursivelyDeleteTriviallyDeadInstructions without checking if the instruction is dead; it internally checks if the instruction is dead.

But more importantly, it means isSafeComputationToRemove isn't actually doing anything useful, so the end result is that this behaves identically to D69428.

https://github.com/llvm/llvm-project/pull/84694