[PATCH] D83013: [LPM] Port CGProfilePass from NPM to LPM

Tue Jul 7 02:16:27 PDT 2020

hans added inline comments.

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Comment at: llvm/lib/Transforms/IPO/PassManagerBuilder.cpp:170

 PassManagerBuilder::PassManagerBuilder() {
     OptLevel = 2;
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Oh, just noticed: I think CallGraphProfile should be initialized along with the other flags here.

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Comment at: llvm/test/Other/opt-O2-pipeline.ll:289
+; CHECK-NEXT:         Branch Probability Analysis
+; CHECK-NEXT:         Block Frequency Analysis
 ; CHECK-NEXT:     FunctionPass Manager
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nikic wrote:
> Is it possible to switch this pass to use LazyBPI / LazyBFA, only fetched if PGO is actually in use?
> 
> PGO functionality that most people don't use adding expensive analysis passes like PDT should be avoided.
I wonder if just switching to LazyBlockFrequencyInfo would help though. It looks to me like the CGProfile would request info about each function anyway.

I was surprised to see that Clang sets Opts.CallGraphProfile solely based on whether the integrated assembler is used. Maybe a better fix is to only set that to true when a profile is actually being used?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83013/new/

https://reviews.llvm.org/D83013