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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/102737] [9/10/11/12 Regression] extra mov with
 int->double conversion and addition (incoming arguments and return)
Date: Wed, 13 Oct 2021 21:25:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102737

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |9.5
      Known to fail|                            |10.1.0, 9.1.0
           Severity|normal                      |enhancement
      Known to work|                            |5.1.0, 8.1.0, 8.5.0
            Summary|[x86] Failure to optimize   |[9/10/11/12 Regression]
                   |out bad register usage      |extra mov with int->double
                   |involving int->double       |conversion and addition
                   |conversion                  |(incoming arguments and
                   |                            |return)

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 8.5.0 (and before) would do:
        pxor    %xmm1, %xmm1
        cvtsi2sd        %edi, %xmm1
        addsd   %xmm1, %xmm0
        ret

So this is a regression.

Even with AVX, gcc has an extra move even if inputs don't have to be tied to
the output:
        vmovsd  %xmm0, %xmm0, %xmm1
        vxorps  %xmm0, %xmm0, %xmm0
        vcvtsi2sdl      %edi, %xmm0, %xmm0
        vaddsd  %xmm1, %xmm0, %xmm0
        ret=