102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
/* ef_atan2.c -- float version of e_atan2.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 "fdlibm.h"
|
|
|
|
#ifdef __STDC__
|
|
static const float
|
|
#else
|
|
static float
|
|
#endif
|
|
tiny = 1.0e-30,
|
|
zero = 0.0,
|
|
pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
|
|
pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
|
|
pi = 3.1415925026e+00, /* 0x40490fda */
|
|
pi_lo = 1.5099578832e-07; /* 0x34222168 */
|
|
|
|
#ifdef __STDC__
|
|
float __ieee754_atan2f(float y, float x)
|
|
#else
|
|
float __ieee754_atan2f(y,x)
|
|
float y,x;
|
|
#endif
|
|
{
|
|
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(FLT_UWORD_IS_NAN(ix)||
|
|
FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */
|
|
return x+y;
|
|
if(hx==0x3f800000) return atanf(y); /* x=1.0 */
|
|
m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
|
|
|
|
/* when y = 0 */
|
|
if(FLT_UWORD_IS_ZERO(iy)) {
|
|
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(FLT_UWORD_IS_ZERO(ix)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
|
|
|
|
/* when x is INF */
|
|
if(FLT_UWORD_IS_INFINITE(ix)) {
|
|
if(FLT_UWORD_IS_INFINITE(iy)) {
|
|
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(FLT_UWORD_IS_INFINITE(iy)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
|
|
|
|
/* compute y/x */
|
|
k = (iy-ix)>>23;
|
|
if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
|
|
else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
|
|
else z=atanf(fabsf(y/x)); /* safe to do y/x */
|
|
switch (m) {
|
|
case 0: return z ; /* atan(+,+) */
|
|
case 1: {
|
|
__uint32_t zh;
|
|
GET_FLOAT_WORD(zh,z);
|
|
SET_FLOAT_WORD(z,zh ^ 0x80000000);
|
|
}
|
|
return z ; /* atan(-,+) */
|
|
case 2: return pi-(z-pi_lo);/* atan(+,-) */
|
|
default: /* case 3 */
|
|
return (z-pi_lo)-pi;/* atan(-,-) */
|
|
}
|
|
}
|