[Bug target/102224] [9/10 regession] wrong code for `x * copysign(1.0, x)` since r9-5298-g33142cf9cf82aa1f

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102224

--- 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 = xorsign op0, op0 we can actually simplify it from
    dest = (op0 & mask) ^ op0 to dest = 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 better
    code through that.

    The @xorsign<mode>3_1 is a fix for the case where xorsign wouldn't be known
    to have same operands during expansion, but during RTL optimizations they
    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)