Hello Everyone, I'm looking for a mentor for a GSoC Project/Proposal. The whole idea revolves around: * Getting hot path information from static analysis and user annotations. * Making sure it's not destroyed by optimization passes. * Using it to generate better code where applicable. See also: #14672: Make likelihood of branches/conditions available throughout the compiler. Towards these goals I would like for GSoC: * Land https://phabricator.haskell.org/D4327(Branchweights in STG and Cmm) + It might be ready before then. But it's a prerequisite so worth listing here. * Design and implement a way for users to: + Mark hot paths in Haskell code. + Push the information through the passes (up to STG) on a best effort basis. STG and beyond is part of the diff above. + The current backend already uses this information in some places, so this alone should lead to small but consistent gains. + I don't plan to add additional optimizations unless there is time left at the end. Where I think I will need help/experience from a mentor is: * Frontend questions: I haven't looked at GHC's parser/renamer yet so while this is surmountable I expect some questions to arise there. * Design questions/feedback: Things like: + How should the user be able to give this information. + What should be flag controlled? What always on? + Things like compile time/executable speed tradeoffs. ... * Potentially the simplifier: I've looked into it briefly as originally D4327 was aimed at the core stage instead of stg. There doesn't seem to be a lot that could mess with hot path information/branchweights. But I haven't worked on the simplifier before and it seems like a good place for unexpected issues to arise. * If this involves the proposal process then also guidance there. For myself: * I'm studying at TU Vienna (Software & Information Engineering) and am close to finishing my undergrad. Located in Austria (UTC+1) * I have contributed a few small changes to GHC throughout last year. See AndreasK on Phab/Trac. * If you want to know more contact me! If you are interested in mentoring me or looking for more details feel free to contact me at klebinger.andreas@gmx.at mailto:klebinger.andreas@gmx.ator look for AndreasK in #ghc Best Regards Andreas