#11095: -O0 -g slows GHC down on list literals (compared to -O0 without -g) -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by slyfox): Replying to [comment:2 carter]:
What c compiler is being invoked. There's known issues with using clang and profiling build way when there's large numbers of literals in a source file. What does gcc --version and ghc --info tell you?
The build of a Bug.hs is not a -prof build. GHC was built as a "prof" flavour to pinpoint what it does. All GHC's I tried are affected: - ghc-HEAD (7.11.20151115, 7.11.20151114) - ghc-7.10.2 (7.10.2.20151030) ghc -v shows the slowdown is not in a C part, but in CorePrep: {{{ $ ghc -v -O0 -g Bug.hs ... [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size of Desugar (after optimization) = {terms: 2,707, types: 1,360, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 2,707, types: 1,360, coercions: 0} *** Tidy Core: Result size of Tidy Core = {terms: 2,707, types: 1,360, coercions: 0} writeBinIface: 1 Names writeBinIface: 3 dict entries *** CorePrep: Result size of CorePrep <hangs here for a minute> ... }}} {{{ $ LANG=C gcc --version gcc (Gentoo 5.2.0 p1.0, pie-0.6.3) 5.2.0 Copyright (C) 2015 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11095#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler