[PATCH] D148877: [PGO]Implement metadata combine for 'branch_weights' of direct callsites

[Mingming Liu via Phabricator via llvm-commits]

mingmingl planned changes to this revision.
mingmingl marked an inline comment as done.
mingmingl added a comment.

plan changes as suggested.



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Comment at: llvm/lib/Transforms/Utils/Local.cpp:2721
+      case LLVMContext::MD_prof:
+        K->setMetadata(Kind, MDNode::getMergedProfMetadata(KMD, JMD, K, J));
+        break;
----------------
davidxl wrote:
> nikic wrote:
> > This should probably be behind a DoesKMove check? If we're CSEing with a dominating call, it doesn't make sense to add the branch weights, as the second call is being removed.
> > 
> > I'd suggest adding a test with a readonly/nounwind/willreturn call being GVNed to cover that case.
> good catch.
thanks for the catch!

Just to confirm I'm getting the point (not particular to a specific pass yet), in https://gcc.godbolt.org/z/nGa6YqWdP, two calls to 'func1' in line 11 and line14 should keep one branch weight (rather than the sum of two). So that is the case when unifying (not merge) is correct.


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  https://reviews.llvm.org/D148877/new/

https://reviews.llvm.org/D148877