mirror of
https://github.com/fluencelabs/musl
synced 2025-05-29 07:31:53 +00:00
0cbb654791
zero, one, two, half are replaced by const literals The policy was to use the f suffix for float consts (1.0f), but don't use suffix for long double consts (these consts can be exactly represented as double).
119 lines
3.7 KiB
C
119 lines
3.7 KiB
C
/* origin: FreeBSD /usr/src/lib/msun/src/e_atan2.c */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*
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*/
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/* atan2(y,x)
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* Method :
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* 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x).
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* 2. Reduce x to positive by (if x and y are unexceptional):
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* ARG (x+iy) = arctan(y/x) ... if x > 0,
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* ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0,
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*
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* Special cases:
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*
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* ATAN2((anything), NaN ) is NaN;
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* ATAN2(NAN , (anything) ) is NaN;
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* ATAN2(+-0, +(anything but NaN)) is +-0 ;
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* ATAN2(+-0, -(anything but NaN)) is +-pi ;
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* ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2;
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* ATAN2(+-(anything but INF and NaN), +INF) is +-0 ;
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* ATAN2(+-(anything but INF and NaN), -INF) is +-pi;
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* ATAN2(+-INF,+INF ) is +-pi/4 ;
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* ATAN2(+-INF,-INF ) is +-3pi/4;
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* ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2;
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*
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* Constants:
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* The hexadecimal values are the intended ones for the following
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* constants. The decimal values may be used, provided that the
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* compiler will convert from decimal to binary accurately enough
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* to produce the hexadecimal values shown.
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*/
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#include "libm.h"
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static const volatile double
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tiny = 1.0e-300;
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static const double
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pi_o_4 = 7.8539816339744827900E-01, /* 0x3FE921FB, 0x54442D18 */
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pi_o_2 = 1.5707963267948965580E+00, /* 0x3FF921FB, 0x54442D18 */
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pi = 3.1415926535897931160E+00; /* 0x400921FB, 0x54442D18 */
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static const volatile double
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pi_lo = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
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double atan2(double y, double x)
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{
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double z;
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int32_t k,m,hx,hy,ix,iy;
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uint32_t lx,ly;
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EXTRACT_WORDS(hx, lx, x);
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ix = hx & 0x7fffffff;
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EXTRACT_WORDS(hy, ly, y);
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iy = hy & 0x7fffffff;
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if ((ix|((lx|-lx)>>31)) > 0x7ff00000 ||
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(iy|((ly|-ly)>>31)) > 0x7ff00000) /* x or y is NaN */
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return x+y;
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if ((hx-0x3ff00000 | lx) == 0) /* x = 1.0 */
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return atan(y);
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m = ((hy>>31)&1) | ((hx>>30)&2); /* 2*sign(x)+sign(y) */
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/* when y = 0 */
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if ((iy|ly) == 0) {
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switch(m) {
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case 0:
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case 1: return y; /* atan(+-0,+anything)=+-0 */
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case 2: return pi+tiny; /* atan(+0,-anything) = pi */
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case 3: return -pi-tiny; /* atan(-0,-anything) =-pi */
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}
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}
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/* when x = 0 */
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if ((ix|lx) == 0)
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return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
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/* when x is INF */
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if (ix == 0x7ff00000) {
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if (iy == 0x7ff00000) {
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switch(m) {
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case 0: return pi_o_4+tiny; /* atan(+INF,+INF) */
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case 1: return -pi_o_4-tiny; /* atan(-INF,+INF) */
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case 2: return 3.0*pi_o_4+tiny; /* atan(+INF,-INF) */
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case 3: return -3.0*pi_o_4-tiny; /* atan(-INF,-INF) */
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}
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} else {
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switch(m) {
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case 0: return 0.0; /* atan(+...,+INF) */
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case 1: return -0.0; /* atan(-...,+INF) */
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case 2: return pi+tiny; /* atan(+...,-INF) */
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case 3: return -pi-tiny; /* atan(-...,-INF) */
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}
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}
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}
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/* when y is INF */
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if (iy == 0x7ff00000)
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return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
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/* compute y/x */
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k = (iy-ix)>>20;
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if (k > 60) { /* |y/x| > 2**60 */
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z = pi_o_2+0.5*pi_lo;
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m &= 1;
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} else if (hx < 0 && k < -60) /* 0 > |y|/x > -2**-60 */
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z = 0.0;
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else /* safe to do y/x */
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z = atan(fabs(y/x));
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switch (m) {
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case 0: return z; /* atan(+,+) */
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case 1: return -z; /* atan(-,+) */
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case 2: return pi - (z-pi_lo); /* atan(+,-) */
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default: /* case 3 */
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return (z-pi_lo) - pi; /* atan(-,-) */
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}
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}
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