Fix cost-centre-stacks bug (#5654)
This fixes some cases of wrong stacks being generated by the profiler. For background and details on the fix see `Note [Evaluating functions with profiling]` in `rts/Apply.cmm`. This does have an impact on allocations for some programs when profiling. nofib results: ``` k-nucleotide +0.0% +8.8% +11.0% +11.0% 0.0% puzzle +0.0% +12.5% 0.244 0.246 0.0% typecheck 0.0% +8.7% +16.1% +16.2% 0.0% ------------------------------------------------------------------------ -------- Min -0.0% -0.0% -34.4% -35.5% -25.0% Max +0.0% +12.5% +48.9% +49.4% +10.6% Geometric Mean +0.0% +0.6% +2.0% +1.8% -0.3% ``` But runtimes don't seem to be affected much, and the examples I looked at were completely legitimate. For example, in puzzle we have this: ``` position :: ItemType -> StateType -> BankType position Bono = bonoPos position Edge = edgePos position Larry = larryPos position Adam = adamPos ``` where the identifiers on the rhs are all record selectors. Previously the profiler gave a stack that looked like ``` position bonoPos ... ``` i.e. `bonoPos` was at the same level of the call stack as `position`, but now it looks like ``` position bonoPos ... ``` I used the normaliser from the testsuite to diff the profiling output from other nofib programs and they all looked better. Test Plan: * the broken test passes * validate * compiled and ran all of nofib, measured perf, diff'd several .prof files Reviewers: niteria, erikd, austin, scpmw, bgamari Reviewed By: bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2804 GHC Trac Issues: #5654, #10007
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- compiler/codeGen/StgCmmClosure.hs 4 additions, 2 deletionscompiler/codeGen/StgCmmClosure.hs
- includes/Cmm.h 6 additions, 0 deletionsincludes/Cmm.h
- rts/Apply.cmm 107 additions, 0 deletionsrts/Apply.cmm
- testsuite/tests/profiling/should_run/T5654-O0.hs 0 additions, 0 deletionstestsuite/tests/profiling/should_run/T5654-O0.hs
- testsuite/tests/profiling/should_run/T5654-O0.prof.sample 28 additions, 0 deletionstestsuite/tests/profiling/should_run/T5654-O0.prof.sample
- testsuite/tests/profiling/should_run/T5654-O1.hs 14 additions, 0 deletionstestsuite/tests/profiling/should_run/T5654-O1.hs
- testsuite/tests/profiling/should_run/T5654-O1.prof.sample 27 additions, 0 deletionstestsuite/tests/profiling/should_run/T5654-O1.prof.sample
- testsuite/tests/profiling/should_run/T5654.prof.sample 0 additions, 28 deletionstestsuite/tests/profiling/should_run/T5654.prof.sample
- testsuite/tests/profiling/should_run/T680.prof.sample 25 additions, 25 deletionstestsuite/tests/profiling/should_run/T680.prof.sample
- testsuite/tests/profiling/should_run/all.T 3 additions, 1 deletiontestsuite/tests/profiling/should_run/all.T
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