[GHC] #8971: Native Code Generator 7.8.1 RC2 is not as optimized as 7.6.3...

[GHC]

#8971: Native Code Generator 7.8.1 RC2 is not as optimized as 7.6.3...
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        Reporter:  GordonBGood              |            Owner:
            Type:  bug                      |           Status:  new
        Priority:  normal                   |        Milestone:
       Component:  Compiler (NCG)           |          Version:  7.8.1-rc2
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  Runtime performance bug  |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Comment (by ezyang):

 Doesn't seem to be a problem on 64-bit:

 {{{
 .Lc4cz:
         cmpq %r8,%rbx
         jg .Lc4cJ
 .Lc4cK:
         movq %rbx,%rdx
         sarq $6,%rdx
         movl $1,%edi
         movq %rcx,%r9
         movq %rbx,%rcx
         andq $63,%rcx
         shlq %cl,%rdi
         xorq $-1,%rdi
         leaq 16(%rax),%rcx
         movq (%rcx,%rdx,8),%rcx
         andq %rdi,%rcx
         leaq 16(%rax),%rdi
         movq %rcx,(%rdi,%rdx,8)
         addq %r9,%rbx
 .Ln4g8:
         movq %r9,%rcx
         jmp .Lc4cz
 }}}

 What happens if you use `-freg-graph`? If you could post C-- dumps that
 would also be helpful.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8971#comment:3>
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