[llvm] [ObjCARC] Delete empty autoreleasepools with no autoreleases in them (PR #144788)

[Jon Roelofs via llvm-commits]

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@@ -2485,6 +2490,197 @@ bool ObjCARCOpt::run(Function &F, AAResults &AA) {
   return Changed;
 }
 
+/// Helper function to recursively check if a value eventually leads to the
+/// target instruction through pointer casts and uses, up to a specified depth.
+static bool checkLeadsToTarget(Value *Val, User *Target, unsigned MaxDepth,
+                               SmallPtrSet<Value *, 8> &Visited) {
+  if (MaxDepth == 0)
+    return false;
+
+  // Avoid infinite recursion by tracking visited values
+  if (!Visited.insert(Val).second)
+    return false;
+
+  for (User *U : Val->users()) {
+    if (U == Target)
+      return true;
+
+    // For pointer casts, recursively check their users
+    if (isa<CastInst>(U)) {
+      if (checkLeadsToTarget(cast<Value>(U), Target, MaxDepth - 1, Visited)) {
+        return true;
+      }
----------------
jroelofs wrote:

no need for `{}`s on one-liner `if`s. (which you should do that pretty much everywhere)

also, `User` inherits from `Value`, so the cast is just noise.

that said, as a higher-level comment, if I'm reading this correctly, I think it would be much more efficient to look from the target, strip pointer casts from it, and see if that points at the `PendingPush`.

https://github.com/llvm/llvm-project/pull/144788