[GHC] #5652: T3016 takes long time to compile with LLVM

[GHC]

#5652: T3016 takes long time to compile with LLVM
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    Reporter:  dterei            |       Owner:  dterei                      
        Type:  bug               |      Status:  new                         
    Priority:  normal            |   Component:  Compiler (LLVM)             
     Version:  7.3               |    Keywords:                              
    Testcase:                    |   Blockedby:                              
          Os:  Unknown/Multiple  |    Blocking:                              
Architecture:  Unknown/Multiple  |     Failure:  Compile-time performance bug
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Comment(by dterei):

 Quick check.

 T3016 takes 30s to compile with -fasm, 2m to compile with -fllvm both at
 O0.

 T3016 takes 8 min to compile with -fasm at -O2, haven't timed -fllvm yet.

 Using -v2 and annotate-ouput command 1 min of the 2 min for llvm seems to
 be spent in the code generator (so either bad performance in actual llvm
 backend or in the mangler) and 1 min in the llc tool. (so bad performance
 by llvm).

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5652#comment:1>
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