[GHC] #13629: sqrt should use machine instruction on x86_64

[GHC]

#13629: sqrt should use machine instruction on x86_64
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler (NCG)    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime           |            Test Case:
  performance bug                    |  numeric/num009
      Blocked By:                    |             Blocking:
 Related Tickets:  #13570            |  Differential Rev(s):  Phab:D3508
       Wiki Page:                    |
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Comment (by bgamari):

 For the record, `sqrtf` is the following on my machine,
 {{{#!asm
    0x00007ffff78892c0 <+0>:     pxor   %xmm1,%xmm1
    0x00007ffff78892c4 <+4>:     ucomiss %xmm0,%xmm1
    0x00007ffff78892c7 <+7>:     ja     0x7ffff78892d0 <__sqrtf+16>
    0x00007ffff78892c9 <+9>:     sqrtss %xmm0,%xmm0
    0x00007ffff78892cd <+13>:    retq
    0x00007ffff78892ce <+14>:    xchg   %ax,%ax
    0x00007ffff78892d0 <+16>:    mov    0x2cccf9(%rip),%rax        #
 0x7ffff7b55fd0
    0x00007ffff78892d7 <+23>:    cmpl   $0xffffffff,(%rax)
    0x00007ffff78892da <+26>:    je     0x7ffff78892c9 <__sqrtf+9>
    0x00007ffff78892dc <+28>:    movaps %xmm0,%xmm1
    0x00007ffff78892df <+31>:    mov    $0x7e,%edi
    0x00007ffff78892e4 <+36>:    jmpq   0x7ffff788ed50
 <__kernel_standard_f>
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13629#comment:19>
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