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

[Uros Bizjak]

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.