From a8ecb126d4c26c52f4ad828c566afe4043a28155 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Thu, 17 Aug 2023 09:42:29 -0700 Subject: x86_64: Add log1p with FMA 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% --- sysdeps/ieee754/dbl-64/s_log1p.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'sysdeps/ieee754/dbl-64') diff --git a/sysdeps/ieee754/dbl-64/s_log1p.c b/sysdeps/ieee754/dbl-64/s_log1p.c index e6476a8260..eeb0af859f 100644 --- a/sysdeps/ieee754/dbl-64/s_log1p.c +++ b/sysdeps/ieee754/dbl-64/s_log1p.c @@ -99,6 +99,11 @@ static const double static const double zero = 0.0; +#ifndef SECTION +# define SECTION +#endif + +SECTION double __log1p (double x) { -- cgit 1.4.1