[llvm] [SimplifyCFG][NFC] Renumber blocks when changing func (PR #186666)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alexis Engelke (aengelke)

<details>
<summary>Changes</summary>

Keep numbering dense when changing the function. SimplifyCFG is a good candidate, because it is likely to remove blocks and preserves few analyses.

[stage2-O3 -0.07%](http://llvm-compile-time-tracker.com/compare.php?from=a7aebd809d49fd1c8205e8f0fcdc8d97777e5103&to=d77a3d37a5d16025371c3b407838d011cbcc6da9&stat=instructions:u)

---
Full diff: https://github.com/llvm/llvm-project/pull/186666.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp (+5-1) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index e790ab8ac1df5..debf033c70c41 100644
--- a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -380,9 +380,13 @@ PreservedAnalyses SimplifyCFGPass::run(Function &F,
     DT = &AM.getResult<DominatorTreeAnalysis>(F);
   if (!simplifyFunctionCFG(F, TTI, DT, Options))
     return PreservedAnalyses::all();
+  // If we removed some blocks, update block numbers to keep dense numbering.
+  F.renumberBlocks();
   PreservedAnalyses PA;
-  if (RequireAndPreserveDomTree)
+  if (RequireAndPreserveDomTree) {
+    DT->updateBlockNumbers();
     PA.preserve<DominatorTreeAnalysis>();
+  }
   return PA;
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/186666