#8901: (very) bad inline heuristics -------------------------------------+------------------------------------ Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by trommler): Replying to [ticket:8901 heisenbug]:

The problem is so bad that the PowerPC32 assembler cannot resolve cross- routine references. (I have no error message at hand, but could try to get one.) FWIW The powerpc issue in the time library (#7830) was fixed by @erikd.

-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8901: (very) bad inline heuristics -------------------------------------+------------------------------------ Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by heisenbug): Replying to [comment:3 simonpj]:

Can you explain what the bug in GHC is? And (as Ashley asks) why you believe it's a bug in GHC and not the library?

It is hard to pinpoint. There has been some rope-pulling between me and Ashley (on the dev list/in private) as he has not been keen of accepting my patch (so far) asking whether it could be a GHC bug. I tend to agree, as a quality inliner should not attempt to inline (e.g.) `formatTime` which has 8 alternatives and is called from 10+ sites. It would be interesting to see whether any bloat-controlling measures failed detecting this case, esp. as `Format.hs` appears to be a relatively benign source file. Some lessons might be learnt from this. OTOH, a library author should keep in eye how popular compilers digest the lib. I am ending up stuck between a rock and a hard place. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8901: (very) bad inline heuristics -------------------------------------+------------------------------------ Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonpj): Not necessarily. It's not hard to give GHC a heart attack by inlining too aggressively. If you can exhibit a case where you think GHC is inlining where it shouldn't I'll gladly look at it. For example you mention `formatTime`; can you give a test case? Eg a test file with 10+ calls, that all inline when they shouldn't? Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8901: (very) bad inline heuristics -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: infoneeded Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by heisenbug): Replying to [comment:2 trommler]:

Replying to [ticket:8901 heisenbug]:

...

The problem is so bad that the PowerPC32 assembler cannot resolve cross-routine references. (I have no error message at hand, but could try to get one.) FWIW The powerpc issue in the time library (#7830) was fixed by @erikd.

But that bug (#7830) is not closed yet! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8901: (very) bad inline heuristics -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: invalid | 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: | -------------------------------------+------------------------------------- Changes (by mpickering): * status: infoneeded => closed * resolution: => invalid Comment: Please reopen if you plan on reinvestigating, it doesn't seem like any more progress is going to be made. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8901: (very) bad inline heuristics -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: invalid | Keywords: Inlining 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 heisenbug): * keywords: => Inlining -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8901#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler