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

[via llvm-commits]

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@@ -601,6 +606,57 @@ class ObjCARCOpt {
 };
 } // end anonymous namespace
 
+/// Find the autoreleasePoolPop that will drain the given autorelease
+/// instruction in the same basic block, skipping over nested pools.
+///
+/// Since objc_autorelease does not change the refcount (it only registers the
+/// object for a deferred release at pool drain), we can move the release to
+/// just before the pool pop instead of converting in place. This avoids the
+/// need to check for uses of the pointer between the autorelease and the pop.
+Instruction *
+ObjCARCOpt::FindFollowingAutoreleasePoolPop(Instruction *AutoreleaseInst) {
+  assert(GetBasicARCInstKind(AutoreleaseInst) == ARCInstKind::Autorelease);
+
+  auto It = FollowingPoolPopCache.find(AutoreleaseInst);
+  if (It != FollowingPoolPopCache.end())
+    return It->second;
+
+  BasicBlock *BB = AutoreleaseInst->getParent();
+  Instruction *Result = nullptr;
+
+  SmallVector<Instruction *, 4> ScopeSiblings;
+
+  int Depth = 0;
+  for (BasicBlock::iterator I = std::next(AutoreleaseInst->getIterator()),
+                            E = BB->end();
+       I != E; ++I) {
+    ARCInstKind Class = GetBasicARCInstKind(&*I);
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AZero13 wrote:

You are right. So I fixed that!

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