/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
* Debugged and optimized by Bruce D. Evans.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/* __rem_pio2f(x,y)
*
* return the remainder of x rem pi/2 in *y
* use double precision for everything except passing x
* use __rem_pio2_large() for large x
*/
#include "libm.h"
/*
* invpio2: 53 bits of 2/pi
* pio2_1: first 25 bits of pi/2
* pio2_1t: pi/2 - pio2_1
*/
static const double
invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
pio2_1 = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
int __rem_pio2f(float x, double *y)
{
union {float f; uint32_t i;} u = {x};
double tx[1],ty[1],fn;
uint32_t ix;
int n, sign, e0;
ix = u.i & 0x7fffffff;
/* 25+53 bit pi is good enough for medium size */
if (ix < 0x4dc90fdb) { /* |x| ~< 2^28*(pi/2), medium size */
/* Use a specialized rint() to get fn. Assume round-to-nearest. */
fn = x*invpio2 + 0x1.8p52;
fn = fn - 0x1.8p52;
n = (int32_t)fn;
*y = x - fn*pio2_1 - fn*pio2_1t;
return n;
}
if(ix>=0x7f800000) { /* x is inf or NaN */
*y = x-x;
return 0;
}
/* scale x into [2^23, 2^24-1] */
sign = u.i>>31;
e0 = (ix>>23) - (0x7f+23); /* e0 = ilogb(|x|)-23, positive */
u.i = ix - (e0<<23);
tx[0] = u.f;
n = __rem_pio2_large(tx,ty,e0,1,0);
if (sign) {
*y = -ty[0];
return -n;
}
*y = ty[0];
return n;
}
