[llvm] [ObjCARC] Move autorelease-to-release conversion to pool pop site instead of converting in place (PR #152353)

[Akira Hatanaka via llvm-commits]

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@@ -2592,64 +2685,80 @@ void ObjCARCOpt::OptimizeAutoreleasePools(Function &F) {
       case ARCInstKind::AutoreleasepoolPush: {
         // Start tracking a new autorelease pool scope
         auto *Push = cast<CallInst>(&Inst);
-        PoolStack.push_back(
-            {Push, false}); // {push_inst, has_autorelease_in_scope}
+        PoolStack.push_back({Push, false});
         LLVM_DEBUG(dbgs() << "Found autorelease pool push: " << *Push << "\n");
         break;
       }
 
       case ARCInstKind::AutoreleasepoolPop: {
         auto *Pop = cast<CallInst>(&Inst);
 
+        // Skip if no matching push found
         if (PoolStack.empty())
           break;
 
-        auto &TopPool = PoolStack.back();
-        CallInst *PendingPush = TopPool.first;
-        bool HasAutoreleaseInScope = TopPool.second;
+        // Get the matching push and whether autoreleases were present
+        CallInst *MatchingPush = PoolStack.back().first;
+        bool HadAutoreleaseInScope = PoolStack.back().second;
+
+        // Verify this pop matches the push (handle pointer casts).
+        // The pop's argument should be the push result, possibly cast.
+        if (Pop->getArgOperand(0)->stripPointerCasts() != MatchingPush) {
+          // Mismatched pop.
+          // We can't trust the stack anymore, invalidating optimization for
+          // this block.
+          PoolStack.clear();
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ahatanak wrote:

It seems that the changes made to `ObjCARCOpt::OptimizeAutoreleasePools` aren't needed for the autorelease-to-release conversion. Is that correct? Can you split it out to a separate PR?

https://github.com/llvm/llvm-project/pull/152353