[llvm] [ADT] Avoid repeated hash lookups (NFC) (PR #125812)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/125812.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/GenericCycleImpl.h (+3-4) 


``````````diff
diff --git a/llvm/include/llvm/ADT/GenericCycleImpl.h b/llvm/include/llvm/ADT/GenericCycleImpl.h
index 41ba8bf8fde14b..4b2e01bcd9c53e 100644
--- a/llvm/include/llvm/ADT/GenericCycleImpl.h
+++ b/llvm/include/llvm/ADT/GenericCycleImpl.h
@@ -454,7 +454,9 @@ void GenericCycleInfoCompute<ContextT>::dfs(BlockT *EntryBlock) {
     BlockT *Block = TraverseStack.back();
     LLVM_DEBUG(errs() << "DFS visiting block: " << Info.Context.print(Block)
                       << "\n");
-    if (!BlockDFSInfo.count(Block)) {
+    if (BlockDFSInfo.try_emplace(Block, Counter + 1).second) {
+      ++Counter;
+
       // We're visiting the block for the first time. Open its DFSInfo, add
       // successors to the traversal stack, and remember the traversal stack
       // depth at which the block was opened, so that we can correctly record
@@ -465,9 +467,6 @@ void GenericCycleInfoCompute<ContextT>::dfs(BlockT *EntryBlock) {
       DFSTreeStack.emplace_back(TraverseStack.size());
       llvm::append_range(TraverseStack, successors(Block));
 
-      bool Added = BlockDFSInfo.try_emplace(Block, ++Counter).second;
-      (void)Added;
-      assert(Added);
       BlockPreorder.push_back(Block);
       LLVM_DEBUG(errs() << "  preorder number: " << Counter << "\n");
     } else {

``````````

</details>


https://github.com/llvm/llvm-project/pull/125812