[llvm] [StructurizeCFG] Avoid repeated hash lookups (NFC) (PR #107797)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/107797.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/StructurizeCFG.cpp (+1-2) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
index a6ed58ac9d47f2..aca8225cebb3fd 100644
--- a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -697,10 +697,9 @@ void StructurizeCFG::findUndefBlocks(
   // undefined value for the PHI being reconstructed.
   while (!Stack.empty()) {
     BasicBlock *Current = Stack.pop_back_val();
-    if (VisitedBlock.contains(Current))
+    if (!VisitedBlock.insert(Current).second)
       continue;
 
-    VisitedBlock.insert(Current);
     if (FlowSet.contains(Current)) {
       for (auto P : predecessors(Current))
         Stack.push_back(P);

``````````

</details>


https://github.com/llvm/llvm-project/pull/107797