From 900fb446eb8172c54cdaed85107bc783ee50673a Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Thu, 23 Aug 2018 12:38:16 +0100 Subject: Speedup tanf range reduction Speedup tanf range reduction by using the new sincosf range reduction algorithm. Overall code quality is improved due to inlining, so there is a speedup even if no range reduction is required. tanf throughput gains on Cortex-A72: * |x| < M_PI_4 : 1.1x * |x| < M_PI_2 : 1.2x * |x| < 2 * M_PI: 1.5x * |x| < 120.0 : 1.6x * |x| < Inf : 12.1x * sysdeps/ieee754/flt-32/s_tanf.c (__tanf): Use fast range reduction. --- sysdeps/ieee754/flt-32/s_tanf.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) (limited to 'sysdeps/ieee754') diff --git a/sysdeps/ieee754/flt-32/s_tanf.c b/sysdeps/ieee754/flt-32/s_tanf.c index ba3af54913..fd104103ad 100644 --- a/sysdeps/ieee754/flt-32/s_tanf.c +++ b/sysdeps/ieee754/flt-32/s_tanf.c @@ -21,6 +21,33 @@ static char rcsid[] = "$NetBSD: s_tanf.c,v 1.4 1995/05/10 20:48:20 jtc Exp $"; #include #include #include +#include "s_sincosf.h" + +/* Reduce range of X to a multiple of PI/2. The modulo result is between + -PI/4 and PI/4 and returned as a high part y[0] and a low part y[1]. + The low bit in the return value indicates the first or 2nd half of tanf. */ +static inline int32_t +rem_pio2f (float x, float *y) +{ + double dx = x; + int n; + const sincos_t *p = &__sincosf_table[0]; + + if (__glibc_likely (abstop12 (x) < abstop12 (120.0f))) + dx = reduce_fast (dx, p, &n); + else + { + uint32_t xi = asuint (x); + int sign = xi >> 31; + + dx = reduce_large (xi, &n); + dx = sign ? -dx : dx; + } + + y[0] = dx; + y[1] = dx - y[0]; + return n; +} float __tanf(float x) { @@ -42,7 +69,7 @@ float __tanf(float x) /* argument reduction needed */ else { - n = __ieee754_rem_pio2f(x,y); + n = rem_pio2f(x,y); return __kernel_tanf(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even -1 -- n odd */ } -- cgit 1.4.1