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/* origin: FreeBSD /usr/src/lib/msun/src/e_atan2f.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* 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.
* ====================================================
*/
#include "libm.h"
static volatile float
tiny = 1.0e-30;
static const float
zero = 0.0,
pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
pi = 3.1415927410e+00; /* 0x40490fdb */
static volatile float
pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */
float atan2f(float y, float x)
{
float z;
int32_t k,m,hx,hy,ix,iy;
GET_FLOAT_WORD(hx, x);
ix = hx & 0x7fffffff;
GET_FLOAT_WORD(hy, y);
iy = hy & 0x7fffffff;
if (ix > 0x7f800000 || iy > 0x7f800000) /* x or y is NaN */
return x+y;
if (hx == 0x3f800000) /* x=1.0 */
return atanf(y);
m = ((hy>>31)&1) | ((hx>>30)&2); /* 2*sign(x)+sign(y) */
/* when y = 0 */
if (iy == 0) {
switch (m) {
case 0:
case 1: return y; /* atan(+-0,+anything)=+-0 */
case 2: return pi+tiny; /* atan(+0,-anything) = pi */
case 3: return -pi-tiny; /* atan(-0,-anything) =-pi */
}
}
/* when x = 0 */
if (ix == 0)
return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
/* when x is INF */
if (ix == 0x7f800000) {
if (iy == 0x7f800000) {
switch (m) {
case 0: return pi_o_4+tiny; /* atan(+INF,+INF) */
case 1: return -pi_o_4-tiny; /* atan(-INF,+INF) */
case 2: return (float)3.0*pi_o_4+tiny; /*atan(+INF,-INF)*/
case 3: return (float)-3.0*pi_o_4-tiny; /*atan(-INF,-INF)*/
}
} else {
switch (m) {
case 0: return zero; /* atan(+...,+INF) */
case 1: return -zero; /* atan(-...,+INF) */
case 2: return pi+tiny; /* atan(+...,-INF) */
case 3: return -pi-tiny; /* atan(-...,-INF) */
}
}
}
/* when y is INF */
if (iy == 0x7f800000)
return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
/* compute y/x */
k = (iy-ix)>>23;
if (k > 26) { /* |y/x| > 2**26 */
z = pi_o_2+(float)0.5*pi_lo;
m &= 1;
} else if (k < -26 && hx < 0) /* 0 > |y|/x > -2**-26 */
z = 0.0;
else /* safe to do y/x */
z = atanf(fabsf(y/x));
switch (m) {
case 0: return z; /* atan(+,+) */
case 1: return -z; /* atan(-,+) */
case 2: return pi - (z-pi_lo); /* atan(+,-) */
default: /* case 3 */
return (z-pi_lo) - pi; /* atan(-,-) */
}
}
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