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powerpc: Remove modff optimization 

The generic implementation is slight more optimized than the powerpc
one, where it has a more optimized inf/nan check (by not using FP
unit checks, along with branch prediction hints), and removed one
branch by issuing trunc instead of a combination of floor/ceil (which
also generated less code).

On power10 with gcc 14.2.1:

reciprocal-throughput        master        patch        difference
workload-0_1                 1.5210       1.3942             8.34%
workload-1_maxint            2.0926       1.3940            33.38%
workload-maxint_maxfloat     1.7851       1.3940            21.91%
workload-integral            1.5216       1.3941             8.37%

latency                      master        patch        difference
workload-0_1                 1.5928       2.6337           -65.35%
workload-1_maxint            3.2929       2.6337            20.02%
workload-maxint_maxfloat     1.9697       2.6341           -33.73%
workload-integral            2.0597       2.6337           -27.87%

Checked on powerpc64le-linux-gnu.
Reviewed-by: Sachin Monga <smonga@linux.ibm.com>
This commit is contained in:
Adhemerval Zanella 2025-06-16 10:17:35 -03:00
parent b2a8d19f4a
commit 5c2b21c478
5 changed files with 12 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sysdeps/ieee754/flt-32/s_modff.c
View File

@ -64,4 +64,6 @@ __modff (float x, float *iptr)
return asfloat (t & SIGN_MASK);
#endif
}
#ifndef __modff
libm_alias_float (__modf, modf)
#endif

8
sysdeps/powerpc/fpu/math-use-builtins-trunc.h Normal file
View File

@ -0,0 +1,8 @@
#define USE_TRUNC_BUILTIN 0
#ifdef _ARCH_PWR5X
# define USE_TRUNCF_BUILTIN 1
#else
# define USE_TRUNCF_BUILTIN 0
#endif
#define USE_TRUNCL_BUILTIN 0
#define USE_TRUNCF128_BUILTIN 0

55
sysdeps/powerpc/fpu/s_modff.c
View File

@ -1,55 +0,0 @@
/* Copyright (C) 2013-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
/* ISA 2.07 provides fast GPR to FP instruction (mfvsr{d,wz}) which make
generic implementation faster. Also disables for old ISAs that do not
have ceil/floor instructions. */
#if defined(_ARCH_PWR8) || !defined(_ARCH_PWR5X)
# include <sysdeps/ieee754/flt-32/s_modff.c>
#else
# include <math.h>
# include <libm-alias-float.h>
float
__modff (float x, float *iptr)
{
if (__builtin_isinff (x))
{
*iptr = x;
return copysignf (0.0, x);
}
else if (__builtin_isnanf (x))
{
*iptr = NAN;
return NAN;
}
if (x >= 0.0)
{
*iptr = floorf (x);
return copysignf (x - *iptr, x);
}
else
{
*iptr = ceilf (x);
return copysignf (x - *iptr, x);
}
}
# ifndef __modff
libm_alias_float (__modf, modf)
# endif
#endif

2
sysdeps/powerpc/powerpc32/power4/fpu/multiarch/s_modff-power5+.c
View File

@ -17,4 +17,4 @@
<https://www.gnu.org/licenses/>. */
#define __modff __modff_power5plus
#include <sysdeps/powerpc/fpu/s_modff.c>
#include <sysdeps/ieee754/flt-32/s_modff.c>

2
sysdeps/powerpc/powerpc64/be/fpu/multiarch/s_modff-power5+.c
View File

@ -17,4 +17,4 @@
<https://www.gnu.org/licenses/>. */
#define __modff __modff_power5plus
#include <sysdeps/powerpc/fpu/s_modff.c>
#include <sysdeps/ieee754/flt-32/s_modff.c>