On 2017.05.25 at 11:55 +0200, Martin Liška wrote: > Hi. > > As I spoke about the PGO with Honza and Richi, current 3-stage is not ideal > for following > 2 reasons: > > 1) stageprofile compiler is train just on libraries that are built during > stage2 > 2) apart from that, as the compiler is also used to build the final compiler, > profile > is being updated during the build. So the stage2 compiler is making different > decisions. > > Both problems can be resolved by adding another step in between current > stage2 and stage3 > where we train stage2 compiler by building compiler with default options.
Another issue that I've noticed is that LTO doesn't get used in the final stage (stagefeedback) with "bootstrap-O3 bootstrap-lto". It only is used during training. So either move -flto to stagefeedback, or use -flto both during training and during the final stage. -- Markus
