[GHC] #13417: piResultTys1

[GHC]

#13417: piResultTys1
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        Reporter:  ralf              |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"82b40598ea7a9c00abdeae37bc47896f880fbbdc/ghc" 82b4059/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="82b40598ea7a9c00abdeae37bc47896f880fbbdc"
 Fix CaseIdentity optimisation AGAIN

 In this commit
     commit 02ac2974ce8e537372bff8d9e0a6efb461ed2c59
     Author: Simon Peyton Jones <simonpj at microsoft.com>
     Date:   Wed Nov 16 10:37:47 2011 +0000

     Fix CaseIdentity optimisaion

     In fixing one bug I'd introduced another;
        case x of { T -> T; F -> F }
     wasn't getting optmised!  Trivial to fix.

 I introduced yet another!  This line of code in SimplUtils.mkCase1

     check_eq (Var v)    (DataAlt con) []   = v == dataConWorkId con
                                              -- Optimisation only

 is patently false when arg_tys is non-empty.  Astonishing that it
 has not shown up before now.

 Easily fixed though.  This was all shown up by Trac #13417, which is
 now fixed.

 Merge to 8.0, 8.2.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13417#comment:9>
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