#14068: Loopification using join points -------------------------------------+------------------------------------- Reporter: nomeata | Owner: nomeata Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: JoinPoints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13966 #14067 | Differential Rev(s): Phab:D3811 Wiki Page: | -------------------------------------+------------------------------------- Changes (by nomeata): * cc: sanjitk@… (added) Comment: Loopification per se works, but it causes huge performance swings in both directions; not because of loopification itself, but because other parts of the compiler now treat the code differently. The current (disheartening) stats are at https://perf.haskell.org/ghc/#compare/af0aea9c3d5f68f2694bd7b6380788764aa3f1... (this URL might stop working in the future when `wip/T14068` is rebased.) Without “Prevent inlining of loopified programs”, we now start inlining stuff that used to be recursive, which is not always a win, it seems. With this patch, we prevent that, but now other things don’t work as well as they used to. I lost steam in the fall tracking down all the regressions, but I now have a master student at Penn, Sanjit Kalapatapu, who is helping to track down them. Currently, he is looking into `SpecConstr`, which seems to stopped doing its thing (maybe because of the no-inline marker that we add…). I hope that with him there will be progress again, but I expect it to be slow progress. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14068#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler