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Subject: [Bug target/102224] [9/10 regession] wrong code for `x *
 copysign(1.0, x)` since r9-5298-g33142cf9cf82aa1f
Date: Wed, 11 May 2022 06:22:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102224

--- Comment #18 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:45579f290157b62a36752ed6df4fbcb7c742fb08

commit r9-10098-g45579f290157b62a36752ed6df4fbcb7c742fb08
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Sep 8 11:25:31 2021 +0200

    i386: Fix up @xorsign<mode>3_1 [PR102224]

    As the testcase shows, we miscompile @xorsign<mode>3_1 if both input
    operands are in the same register, because the splitter overwrites op1
    before with op1 & mask before using op0.

    For dest =3D xorsign op0, op0 we can actually simplify it from
    dest =3D (op0 & mask) ^ op0 to dest =3D op0 & ~mask (aka abs).

    The expander change is an optimization improvement, if we at expansion
    time know it is xorsign op0, op0, we can emit abs right away and get be=
tter
    code through that.

    The @xorsign<mode>3_1 is a fix for the case where xorsign wouldn't be k=
nown
    to have same operands during expansion, but during RTL optimizations th=
ey
    would appear.  We need to use earlyclobber, we require dest and op1 to =
be
    the same but op0 must be different because we overwrite
    op1 first.

    2021-09-08  Jakub Jelinek  <jakub@redhat.com>

            PR target/102224
            * config/i386/i386.md (xorsign<mode>3): If operands[1] is equal=
 to
            operands[2], emit abs<mode>2 instead.
            (@xorsign<mode>3_1): Add early-clobber for output operand.

            * gcc.dg/pr102224.c: New test.
            * gcc.target/i386/avx-pr102224.c: New test.

    (cherry picked from commit a7b626d98a9a821ffb33466818d6aa86cac1d6fd)=