Re: [PATCH] x86: Optimize copysign (x, const_double)

[H.J. Lu]

On Mon, Oct 20, 2025 at 2:12 PM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Sun, Oct 19, 2025 at 11:35 PM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > After
> >
> > commit 3f176e1adc6bc9cc2c21222d776b51d9f43cb66b
> > Author: Tamar Christina <tamar.christ...@arm.com>
> > Date:   Thu Nov 9 13:59:39 2023 +0000
> >
> >     middle-end: optimize fneg (fabs (x)) to copysign (x, -1) [PR109154]
> >
> > fneg (fabs (x)) is expanded to copysign (x, -1).  Swap constraints for
> > operands[1] and operands[2] in copysign<mode>3 pattern to optimize
> >
> >   y = copysign (x, const_double)
> >
> > instead of
> >
> >   y = copysign (const_double, x)
> >
> > Simplify
> >
> >   y = copysign (x, positive_const_double)
> >
> > to
> >
> >   y = ~signbit_mask & x
> >
> > and
> >
> >   y = copysign (x, negative_const_double)
> >
> > to
> >
> >   y = signbit_mask | x
> >
> > gcc/
> >
> > PR target/99930
> > PR target/122323
> > * config/i386/i386-expand.cc (ix86_expand_copysign): Swap
> > operands[1] with operands[2].  Optimize copysign (x, const_double)
> > instead of copysign (const_double, x).
> > * config/i386/i386.md (copysign<mode>3): Swap constraints for
> > operands[1] and operands[2].
> >
> > gcc/testsuite/
> >
> > PR target/99930
> > PR target/122323
> > * gcc.target/i386/builtin-copysign-2.c: New test.
> > * gcc.target/i386/builtin-copysign-3.c: Likewise.
> > * gcc.target/i386/builtin-copysign-4.c: Likewise.
> > * gcc.target/i386/builtin-copysign-5.c: Likewise.
> > * gcc.target/i386/builtin-copysign-6.c: Likewise.
> > * gcc.target/i386/builtin-copysign-7.c: Likewise.
> > * gcc.target/i386/builtin-copysign-8a.c: Likewise.
> > * gcc.target/i386/builtin-copysign-8b.c: Likewise.
> > * gcc.target/i386/builtin-fabs-1.c: Likewise.
> > * gcc.target/i386/builtin-fabs-2.c: Likewise.
>
> OK.
>
> Thanks,
> Uros.

OK to backport it to release branches?

-- 
H.J.