[PATCH] D99249: [PassManager] Run additional LICM before LoopRotate

[Thomas Preud'homme via Phabricator via llvm-commits]

thopre added inline comments.


================
Comment at: llvm/lib/Passes/PassBuilder.cpp:579
   // TODO: Investigate promotion cap for O1.
   LPM1.addPass(LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap));
   LPM1.addPass(SimpleLoopUnswitchPass());
----------------
lebedev.ri wrote:
> thopre wrote:
> > mkazantsev wrote:
> > > Theroretically LICM should move all invariants out of loop, and loop rotation should not create any new invariants. Do we really need this again?
> > Load of size >4 whose base pointer is derived from the `this` pointer fail the isSafeToExecuteUnconditionally() in LICM because the alignment of the `this` is 1.
> > Theroretically LICM should move all invariants out of loop, and loop rotation should not create any new invariants. Do we really need this again?
> 
> I think the numbers speak for themselves, see 3'rd table in the description i just added
> that shows improvements when going from `LICM before LoopRotate` to `LICM after LoopRotate`.
> Especially, note the `licm.NumSunk` (+30%), and note that there was no such regression
> when just moving the LICM to before LoopRotate.
> 
Sorry I misread, you meant **moving** LICM before rather than **adding** a new LICM pass before.


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  https://reviews.llvm.org/D99249/new/

https://reviews.llvm.org/D99249