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powerpc: Remove modf 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                 1.1351        0.9067            20.12%
workload-1_maxint            1.4230        0.9040            36.47%
workload-maxint_maxfloat     1.5038        0.9076            39.65%
workload-integral            1.1280        0.9111            19.23%

latency                      master         patch        difference
workload-0_1                 1.1440        2.7117          -137.03%
workload-1_maxint            4.0556        2.7070            33.25%
workload-maxint_maxfloat     3.2122        2.7164            15.43%
workload-integral            3.2381        2.7281            15.75%

Checked on powerpc64le-linux-gnu.
Reviewed-by: Sachin Monga <smonga@linux.ibm.com>
This commit is contained in:
Adhemerval Zanella 2025-06-16 10:17:36 -03:00
parent 5c2b21c478
commit 79bfbc93de
4 changed files with 4 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
sysdeps/powerpc/fpu/math-use-builtins-trunc.h
View File

@ -1,8 +1,9 @@
#define USE_TRUNC_BUILTIN 0
#ifdef _ARCH_PWR5X
# define USE_TRUNCF_BUILTIN 1
# define USE_TRUNC_BUILTIN 1
#else
# define USE_TRUNCF_BUILTIN 0
# define USE_TRUNC_BUILTIN 0
#endif
#define USE_TRUNCL_BUILTIN 0
#define USE_TRUNCF128_BUILTIN 0

59
sysdeps/powerpc/fpu/s_modf.c
View File

@ -1,59 +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/ldbl-opt/s_modf.c>
#else
# include <math.h>
# include <math_ldbl_opt.h>
# include <libm-alias-double.h>
double
__modf (double x, double *iptr)
{
if (__builtin_isinf (x))
{
*iptr = x;
return copysign (0.0, x);
}
else if (__builtin_isnan (x))
{
*iptr = NAN;
return NAN;
}
if (x >= 0.0)
{
*iptr = floor (x);
return copysign (x - *iptr, x);
}
else
{
*iptr = ceil (x);
return copysign (x - *iptr, x);
}
}
# ifndef __modf
libm_alias_double (__modf, modf)
# if LONG_DOUBLE_COMPAT (libc, GLIBC_2_0)
compat_symbol (libc, __modf, modfl, GLIBC_2_0);
# endif
# endif
#endif

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

@ -17,4 +17,4 @@
<https://www.gnu.org/licenses/>. */
#define __modf __modf_power5plus
#include <sysdeps/powerpc/fpu/s_modf.c>
#include <sysdeps/ieee754/dbl-64/s_modf.c>

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

@ -17,4 +17,4 @@
<https://www.gnu.org/licenses/>. */
#define __modf __modf_power5plus
#include <sysdeps/powerpc/fpu/s_modf.c>
#include <sysdeps/ieee754/dbl-64/s_modf.c>