nikic added inline comments.
================ Comment at: llvm/test/Other/opt-O2-pipeline.ll:289 +; CHECK-NEXT: Branch Probability Analysis +; CHECK-NEXT: Block Frequency Analysis ; CHECK-NEXT: FunctionPass Manager ---------------- hans wrote: > 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? > I wonder if just switching to LazyBlockFrequencyInfo would help though. It > looks to me like the CGProfile would request info about each function anyway. It would only help if there is some way to only fetch the analysis conditionally. I believe many PGO passes use something like PSI.hasProfileSummary() or F.hasProfileData() for that. > 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? Right, just disabling this by default in clang/opt would also work. For reference, the current compile-time numbers for this patch: https://llvm-compile-time-tracker.com/compare.php?from=516ff1d4baee28b1911737e47b42973567adf8ff&to=8df840660bb764b6653fcfd9ac7a72cc6adebde6&stat=instructions Not huge, but it adds up (some similar regressions have been introduced in LLVM 10). Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D83013/new/ https://reviews.llvm.org/D83013 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
