modimo added a comment.
In D86156#2242872 <https://reviews.llvm.org/D86156#2242872>, @asbirlea wrote:
> As a general note, it may make sense to include BFI in the set of loop passes
> always preserved (`getLoopPassPreservedAnalyses()`), if its nature is to
> always be preserved (with some potential info loss) due to the callbacks
> deleting blocks. But since we're only looking at LICM effect for now, this
> can be a follow up when/if needed.
Certainly, that makes a lot of sense and makes it easier for any other loop
optimization to take advantage of this data. I definitely want to make that
happen, process-wise agreed that following up makes sense instead of tacking
this on in addition.
================
Comment at: llvm/lib/Transforms/Scalar/LICM.cpp:220
&getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
+ &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI(),
&getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(
----------------
nikic wrote:
> I believe that to make this actually lazy the getBFI() call needs to be
> guarded by some other check for presence of profiling data, otherwise it will
> be computed unconditionally at this point. Typically something like
> F.hasProfileData() or PSI.hasProfileSummary().
Appreciate the diligence here-your website is great!
Your assessment is correct, the ".getBFI()" call for lazy will calculate BFI.
I've guarded it under hasProfileData now.
I see in the "about" section that I can use your setup to test TP changes
myself, here's my fork of llvm-project if that option is still available:
https://github.com/modiking/llvm-project
================
Comment at: llvm/test/Other/opt-O2-pipeline.ll:281
; CHECK-NEXT: Loop Invariant Code Motion
; CHECK-NEXT: Lazy Branch Probability Analysis
; CHECK-NEXT: Lazy Block Frequency Analysis
----------------
asbirlea wrote:
> Mark LICM to preserve these passes so they get moved above LICM rather than
> recomputed here (same as they are preserved in unswitch).
Marked, these are no longer calculated again.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D86156/new/
https://reviews.llvm.org/D86156
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