| /* 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 const float |
| pi = 3.1415927410e+00, /* 0x40490fdb */ |
| pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ |
| |
| float atan2f(float y, float x) |
| { |
| float z; |
| uint32_t m,ix,iy; |
| |
| if (isnan(x) || isnan(y)) |
| return x+y; |
| GET_FLOAT_WORD(ix, x); |
| GET_FLOAT_WORD(iy, y); |
| if (ix == 0x3f800000) /* x=1.0 */ |
| return atanf(y); |
| m = ((iy>>31)&1) | ((ix>>30)&2); /* 2*sign(x)+sign(y) */ |
| ix &= 0x7fffffff; |
| iy &= 0x7fffffff; |
| |
| /* when y = 0 */ |
| if (iy == 0) { |
| switch (m) { |
| case 0: |
| case 1: return y; /* atan(+-0,+anything)=+-0 */ |
| case 2: return pi; /* atan(+0,-anything) = pi */ |
| case 3: return -pi; /* atan(-0,-anything) =-pi */ |
| } |
| } |
| /* when x = 0 */ |
| if (ix == 0) |
| return m&1 ? -pi/2 : pi/2; |
| /* when x is INF */ |
| if (ix == 0x7f800000) { |
| if (iy == 0x7f800000) { |
| switch (m) { |
| case 0: return pi/4; /* atan(+INF,+INF) */ |
| case 1: return -pi/4; /* atan(-INF,+INF) */ |
| case 2: return 3*pi/4; /*atan(+INF,-INF)*/ |
| case 3: return -3*pi/4; /*atan(-INF,-INF)*/ |
| } |
| } else { |
| switch (m) { |
| case 0: return 0.0f; /* atan(+...,+INF) */ |
| case 1: return -0.0f; /* atan(-...,+INF) */ |
| case 2: return pi; /* atan(+...,-INF) */ |
| case 3: return -pi; /* atan(-...,-INF) */ |
| } |
| } |
| } |
| /* |y/x| > 0x1p26 */ |
| if (ix+(26<<23) < iy || iy == 0x7f800000) |
| return m&1 ? -pi/2 : pi/2; |
| |
| /* z = atan(|y/x|) with correct underflow */ |
| if ((m&2) && iy+(26<<23) < ix) /*|y/x| < 0x1p-26, x < 0 */ |
| z = 0.0; |
| else |
| 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(-,-) */ |
| } |
| } |
