Re: [GCC][PATCH][mid-end] Optimize x * copysign (1.0, y) [Patch (1/2)]

[Andrew Pinski <pinskia@gmail.com>]

On Mon, Jun 12, 2017 at 12:56 AM, Tamar Christina
<Tamar.Christina@arm.com> wrote:
> Hi All,
>
> this patch implements a optimization rewriting
>
> x * copysign (1.0, y) and
> x * copysign (-1.0, y)
>
> to:
>
> x ^ (y & (1 << sign_bit_position))
>
> This is done by creating a special builtin during matching and generate the
> appropriate instructions during expand. This new builtin is called XORSIGN.
>
> The expansion of xorsign depends on if the backend has an appropriate optab
> available. If this is not the case then we use a modified version of the existing
> copysign which does not take the abs value of the first argument as a fall back.
>
> This patch is a revival of a previous patch
> https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00069.html
>
> Bootstrapped on both aarch64-none-linux-gnu and x86_64 with no issues.
> Regression done on aarch64-none-linux-gnu and no regressions.


Note this is also PR 19706.

Thanks,
Andrew

>
> Ok for trunk?
>
> gcc/
> 2017-06-07  Tamar Christina  <tamar.christina@arm.com>
>
>         * builtins.def (BUILT_IN_XORSIGN, BUILT_IN_XORSIGNF): New.
>         (BUILT_IN_XORSIGNL, BUILT_IN_XORSIGN_FLOAT_NX): Likewise.
>         * match.pd (mult (COPYSIGN:s real_onep @0) @1): New simplifier.
>         (mult (COPYSIGN:s real_mus_onep @0) @1): Likewise.
>         (copysigns @0 (negate @1)): Likewise.
>         * builtins.c (expand_builtin_copysign): Promoted local to argument.
>         (expand_builtin): Added CASE_FLT_FN_FLOATN_NX (BUILT_IN_XORSIGN) and
>         CASE_FLT_FN (BUILT_IN_XORSIGN).
>         (BUILT_IN_COPYSIGN): Updated function call.
>         * optabs.h (expand_copysign): New bool.
>         (expand_xorsign): New.
>         * optabs.def (xorsign_optab): New.
>         * optabs.c (expand_copysign): New parameter.
>         * fortran/f95-lang.c (xorsignl, xorsign, xorsignf): New.
>         * fortran/mathbuiltins.def (XORSIGN): New.
>
> gcc/testsuite/
> 2017-06-07  Tamar Christina  <tamar.christina@arm.com>
>
>         * gcc.dg/tree-ssa/xorsign.c: New.
>         * gcc.dg/xorsign_exec.c: New.
>         * gcc.dg/vec-xorsign_exec.c: New.
>         * gcc.dg/tree-ssa/reassoc-39.c (f2, f3): Updated constant to 2.