[PATCH v3 2/2] math: Optimize flt-32 remainder implementation

[Wilco Dijkstra]

Hi Adhemerval,

> With same micro-optimization done for the double variant:
>
>  * Combine the |y| zero check.
>  * Rework the check to adjust result and call fmod.
>  * Remove one check after fmod.
>  * Remove float-int-float roundtrip on return.
>
> Also use math_config.h macros and indent the code.  The resulting
> strategy is different in many places that I think requires a
> different Copyright.
>
> I see the following performance improvements using remainder benchtests
> (using reciprocal-throughput metric):
>
> Architecture     | Input           |   master |   patch  | Improvemnt
> -----------------|-----------------|----------|-----------------------
> x86_64           | subnormals      |  20.4176 |  19.6144 |      3.93%
> x86_64           | normal          |  54.0939 |  52.2343 |      3.44%
> x86_64           | close-exponent  |  23.9120 |  22.3768 |      6.42%
> aarch64          | subnormals      |   9.2423 |   8.3825 |      9.30%
> aarch64          | normal          |  30.5393 |   29.244 |      4.24%
> aarch64          | close-exponent  |  15.5405 |  13.9256 |     10.39%
>
> The aarch64 used as Neoverse-N1, gcc 15.1.1; while the x86_64 was
> a AMD Ryzen 9 5900X, gcc 15.2.1.
>
> Checked on x86_64-linux-gnu and aarch64-linux-gnu.

Looks good to me now. One nit for both double and float:

+      /* |x| not finite, |y| equal 0 is handled by fmod.  */
+      if (hx >= EXPONENT_MASK)
+	return (x * p) / (x * p);

This should have a __glibc_unlikely. OK with that.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco