[GHC] #10083: ghc: panic! (the 'impossible' happened)

[GHC]

#10083: ghc: panic! (the 'impossible' happened)
-------------------------------------+-------------------------------------
        Reporter:  hedayaty          |                   Owner:
            Type:  bug               |                  Status:  infoneeded
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by simonpj):

 Actually comment:17 does '''not''' fix #10083, because I found that the
 fix made the compiler go slower:
 {{{
 Unexpected stat failures:
    perf/compiler  T1969 [stat not good enough] (normal)
    perf/compiler  T9872a [stat not good enough] (normal)
    perf/compiler  T9872b [stat not good enough] (normal)
    perf/compiler  T9872c [stat not good enough] (normal)
    perf/compiler  T9872d [stat not good enough] (normal)

 bytes allocated value is too high:
     Deviation   T1969(normal) bytes allocated:       7.5 %
     Deviation   T9872d(normal) bytes allocated:      9.3 %
     Deviation   T9872c(normal) bytes allocated:      8.4 %
 }}}
 by about 8% allocation overall. So the patch has all the code, but the key
 bit is commented out.

 See `Note [Inlining and hs-boot files]` in `TcBinds`.   Presumably
 disabling inlining of functions exported by a `hs-boot` file really kills
 GHC's performance somewhere, implausible though it sounds.  I suppose the
 next thing to do is to find out why, but I just don't have time to do that
 now, so I'm parking the whole thing.  Sigh.  Does anyone want to help?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10083#comment:18>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler