[GHC] #14790: eqTypeRep does not inline

[GHC]

#14790: eqTypeRep does not inline
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.1-alpha2
      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:                    |
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Comment (by dfeuer):

 No, not yet. I'll do that later today if you like. But I also don't really
 understand what that will accomplish. `INLINABLE` tells GHC to make an
 unfolding. But GHC already makes an unfolding; it just doesn't use it.
 Does `INLINABLE` change what unfolding it makes? The purpose of the
 wrapper is to use the fact that we know more about what information will
 be available/useful at typical `eqTypeRep` call sites than the compiler
 does; we therefore have a better sense of which part will actually be
 useful to inline. If we inline the whole thing as it stands, then the call
 site will get two calls to `typeRepFingerprint` and a call to `==`. That's
 certainly larger than a call to `sameTypeRep`; is it also better in enough
 cases to matter? I don't know. On the other hand, I know that in virtually
 all realistic cases we want to use inlining to eliminate the `Maybe`
 business.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14790#comment:14>
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