/* 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 "libc/math/libm.h" #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1 #define EPS DBL_EPSILON #elif FLT_EVAL_METHOD==2 #define EPS LDBL_EPSILON #endif /* * invpio2: 53 bits of 2/pi * pio2_1: first 25 bits of pi/2 * pio2_1t: pi/2 - pio2_1 */ static const double toint = 1.5/EPS, 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]; double_t 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 = (double_t)x*invpio2 + toint - toint; 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; }