[GHC] #11668: SPEC has a runtime cost
#11668: SPEC has a runtime cost -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As far as I know, `SPEC` is merely intended to help the compiler identify calls for which constructor specialization may be help. Yet it's not erased! In fact, it has a runtime representation which we need to construct and pass around to so-marked calls. This likely isn't killing the performance of anyone's programs but surely we can do better than this. Really, the whole scheme of marking functions with `SPEC` (which as far as I know isn't even properly documented) seems quite odd. What is stopping us from simply attaching pragmas to equations? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11668 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11668: SPEC has a runtime cost if constructor specialization isn't performed -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): It seems that SPEC is correctly eliminated if `-fspec-constr` is used so this should only be a problem for code expecting constructor specialization that gets compiled with `-O1`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11668#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11668: SPEC has a runtime cost if constructor specialization isn't performed -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): See `Note [Forcing specialisation]` in `SpecConstr`. The whole `SPEC` or `ForceSpecConstr` business (to force specialisation) is very unsatisfactory. It's just awaiting some bright person to have a better idea. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11668#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11668: SPEC has a runtime cost if constructor specialization isn't performed -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: SpecConstr Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => SpecConstr -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11668#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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