[GHC] #7534: allocateRegsAndSpill: Cannot read from uninitialized register

[GHC]

#7534: allocateRegsAndSpill: Cannot read from uninitialized register
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    Reporter:  erikd      |       Owner:  simonmar           
        Type:  bug        |      Status:  new                
    Priority:  normal     |   Milestone:                     
   Component:  Compiler   |     Version:  7.7                
    Keywords:             |          Os:  Linux              
Architecture:  powerpc64  |     Failure:  Building GHC failed
  Difficulty:  Unknown    |    Testcase:                     
   Blockedby:             |    Blocking:                     
     Related:             |  
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Comment(by simonmar):

 So the background is that this panic used to be commented out, but I
 enabled it recently because it makes debugging much easier (with the panic
 commented out, the compiler will happily generate completely bogus code
 that will crash at runtime). However, it adds another invariant, as
 mentioned in the comment: all register must be written before they are
 read (not an unreasonable assumption, I'm sure you'll agree)  I presume
 this invariant is being violated somewhere.

 To debug it you'll need to use `-ddump-cmm` and find out where the bogus
 code comes from.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7534#comment:4>
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