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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/104405] Inefficient register allocation on complex
 arithmetic
Date: Sun, 06 Feb 2022 09:19:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104405

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-02-06
           Keywords|                            |ra
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This has nothing to do with expansion of IMAGPART_EXPR here but rather the
reuturn side.
Note the x86 issue is different from the aarch64 issue

Here is a testcase which shows it is just return side related:
_Complex double=20
 f1 ( double ar, double ai, double br, double bi, double *t)
{
    double _14, _16, _17, _3;
  _14 =3D ai * bi;
  _16 =3D ai * br;
  _17 =3D -(ar*br)+_14;
  _3 =3D (-(ar*bi)-_16);
  return __builtin_complex(_3, _17);
}

Also adding -fno-schedule-insns for the above testcase removes all of the e=
xtra
move instructions.

The big question becomes now is really an issue in real world code or just a
toy benchmark which is testing argument/return passing optimizations?=