AuroraMiddleware/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-01-10 19:30:10 +00:00
Code Issues Packages Projects Releases Wiki Activity

math: Use sign as double for reduced case in sinf

Browse Source 
This patch avoid an extra floating point to integer conversion in
reduced internal function for generic sinf by defining the sign as
double instead of integers.

There is no much difference on Haswell with GCC 7.2.1:

           Before        After
min          9.11        9.108
mean       21.982      21.9224

However H.J. Lu reported gains on Skylake:

Before:

  "sinf": {
   "": {
    "duration": 3.4044e+10,
    "iterations": 1.9942e+09,
    "max": 141.106,
    "min": 7.704,
    "mean": 17.0715
   }
  }

After:

  "sinf": {
   "": {
    "duration": 3.40665e+10,
    "iterations": 2.03199e+09,
    "max": 95.994,
    "min": 7.704,
    "mean": 16.765
   }
  }

Checked on x86_64-linux-gnu.

	* sysdeps/ieee754/flt-32/s_sinf.c (ones): Define as double.
	(reduced): Use ones as double instead of integer.
This commit is contained in:
Adhemerval Zanella 2017-12-05 15:27:03 -02:00
parent 00d54af7c8
commit 94d80dfc73
2 changed files with 7 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
ChangeLog
View File

@ -1,3 +1,8 @@
2017-12-05 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* sysdeps/ieee754/flt-32/s_sinf.c (ones): Define as double.
(reduced): Use ones as double instead of integer.
2017-12-05 Szabolcs Nagy <szabolcs.nagy@arm.com>
* sysdeps/ieee754/flt-32/s_sinf.c (sinf): Use isless.

4
sysdeps/ieee754/flt-32/s_sinf.c
View File

@ -75,7 +75,7 @@ static const double invpio4_table[] = {
0x1.0e4107cp-169
};
static const int ones[] = { +1, -1 };
static const double ones[] = { 1.0, -1.0 };
/* Compute the sine value using Chebyshev polynomials where
THETA is the range reduced absolute value of the input
@ -92,7 +92,7 @@ reduced (const double theta, const unsigned int n,
const double theta2 = theta * theta;
/* We are operating on |x|, so we need to add back the original
signbit for sinf. */
int sign;
double sign;
/* Determine positive or negative primary interval. */
sign = ones[((n >> 2) & 1) ^ signbit];
/* Are we in the primary interval of sin or cos? */