mirror/glibc
2
0
Fork 0
mirror of git://sourceware.org/git/glibc.git synced 2025-02-23 13:09:58 +08:00
Code Issues Packages Projects Releases Wiki Activity

x86_64: Add log1p with FMA

Browse Source 
On Skylake, it changes log1p bench performance by:

        Before       After     Improvement
max     63.349       58.347       8%
min     4.448        5.651        -30%
mean    12.0674      10.336       14%

The minimum code path is

 if (hx < 0x3FDA827A)                          /* x < 0.41422  */
    {
      if (__glibc_unlikely (ax >= 0x3ff00000))           /* x <= -1.0 */
        {
	   ...
        }
      if (__glibc_unlikely (ax < 0x3e200000))           /* |x| < 2**-29 */
        {
          math_force_eval (two54 + x);          /* raise inexact */
          if (ax < 0x3c900000)                  /* |x| < 2**-54 */
            {
	      ...
            }
          else
            return x - x * x * 0.5;

FMA and non-FMA code sequences look similar.  Non-FMA version is slightly
faster.  Since log1p is called by asinh and atanh, it improves asinh
performance by:

        Before       After     Improvement
max     75.645       63.135       16%
min     10.074       10.071       0%
mean    15.9483      14.9089      6%

and improves atanh performance by:

        Before       After     Improvement
max     91.768       75.081       18%
min     15.548       13.883       10%
mean    18.3713      16.8011      8%

(cherry picked from commit a8ecb126d4)
This commit is contained in:
H.J. Lu 2023-08-17 09:42:29 -07:00 committed by Sunil K Pandey
parent c0cae389fb
commit f2947239b6
4 changed files with 40 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
sysdeps/ieee754/dbl-64/s_log1p.c
View File

@ -99,6 +99,11 @@ static const double
static const double zero = 0.0;
#ifndef SECTION
# define SECTION
#endif
SECTION
double
__log1p (double x)
{

2
sysdeps/x86_64/fpu/multiarch/Makefile
View File

@ -38,6 +38,7 @@ libm-sysdep_routines += \
e_pow-fma \
s_atan-fma \
s_expm1-fma \
s_log1p-fma \
s_sin-fma \
s_sincos-fma \
s_tan-fma \
@ -51,6 +52,7 @@ CFLAGS-e_log2-fma.c = -mfma -mavx2
CFLAGS-e_pow-fma.c = -mfma -mavx2
CFLAGS-s_atan-fma.c = -mfma -mavx2
CFLAGS-s_expm1-fma.c = -mfma -mavx2
CFLAGS-s_log1p-fma.c = -mfma -mavx2
CFLAGS-s_sin-fma.c = -mfma -mavx2
CFLAGS-s_tan-fma.c = -mfma -mavx2
CFLAGS-s_sincos-fma.c = -mfma -mavx2

4
sysdeps/x86_64/fpu/multiarch/s_log1p-fma.c Normal file
View File

@ -0,0 +1,4 @@
#define __log1p __log1p_fma
#define SECTION __attribute__ ((section (".text.fma")))
#include <sysdeps/ieee754/dbl-64/s_log1p.c>

29
sysdeps/x86_64/fpu/multiarch/s_log1p.c Normal file
View File

@ -0,0 +1,29 @@
/* Multiple versions of log1p.
Copyright (C) 2023 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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <libm-alias-double.h>
extern double __redirect_log1p (double);
#define SYMBOL_NAME log1p
#include "ifunc-fma.h"
libc_ifunc_redirected (__redirect_log1p, __log1p, IFUNC_SELECTOR ());
#define __log1p __log1p_sse2
#include <sysdeps/ieee754/dbl-64/s_log1p.c>