commit 653977c4a31643497655600688ff238b734f7512
author H.J. Lu <hjl.tools@gmail.com> Sun Oct 19 09:13:52 2025 +0800
committer H.J. Lu <hjl.tools@gmail.com> Fri Oct 24 09:54:24 2025 +0800
tree 6cfdecbd167d31d43707a56dcfc1f38bb47e0b0b
parent 0ec0def9de8a50f545bad3f24ddf01d86720ea57

x86: Optimize copysign (x, const_double)

After

commit 3f176e1adc6bc9cc2c21222d776b51d9f43cb66b
Author: Tamar Christina <tamar.christina@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.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit c3b0ecf04f8c14360cc02c737446c029038a95f7)