[llvm] [GVN] Look through select/phi when determining underlying object (PR #99509)

[via llvm-commits]

================
@@ -6609,6 +6609,46 @@ void llvm::getUnderlyingObjects(const Value *V,
   } while (!Worklist.empty());
 }
 
+const Value *llvm::getUnderlyingObjectAggressive(const Value *V) {
+  const unsigned MaxVisited = 8;
+
+  SmallPtrSet<const Value *, 8> Visited;
+  SmallVector<const Value *, 8> Worklist;
+  Worklist.push_back(V);
+  const Value *Object = nullptr, *FirstObject = nullptr;
+  do {
+    const Value *P = Worklist.pop_back_val();
+    P = getUnderlyingObject(P);
+
+    if (!FirstObject)
+      FirstObject = P;
----------------
goldsteinn wrote:

Not the nicest but:
```
 auto SetNextP = [&]() -> bool {
    if(Worklist.empty())
       return false;
    P = getUnderlyingObject(Worklist.pop_back_val());
    return true;
 };
 FirstObject = P = getUnderlyingObject(V);
 do {
     if (!Visited.insert(P).second)
     ...
  } while(SetNextP());
```

https://github.com/llvm/llvm-project/pull/99509