| 1 | /* e_atan2f.c -- float version of e_atan2.c.
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| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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| 3 | */
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| 4 |
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| 5 | /*
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| 6 | * ====================================================
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 8 | *
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 10 | * Permission to use, copy, modify, and distribute this
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| 11 | * software is freely granted, provided that this notice
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| 12 | * is preserved.
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| 13 | * ====================================================
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| 14 | */
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| 15 |
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| 16 | #ifndef lint
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| 17 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_atan2f.c,v 1.7 2004/06/02 17:09:05 bde Exp $";
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| 18 | #endif
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| 19 |
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| 20 | #include "math.h"
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| 21 | #include "math_private.h"
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| 22 |
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| 23 | static const float
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| 24 | tiny = 1.0e-30,
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| 25 | zero = 0.0,
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| 26 | pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
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| 27 | pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
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| 28 | pi = 3.1415927410e+00, /* 0x40490fdb */
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| 29 | pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */
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| 30 |
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| 31 | float
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| 32 | __ieee754_atan2f(float y, float x)
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| 33 | {
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| 34 | float z;
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| 35 | int32_t k,m,hx,hy,ix,iy;
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| 36 |
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| 37 | GET_FLOAT_WORD(hx,x);
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| 38 | ix = hx&0x7fffffff;
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| 39 | GET_FLOAT_WORD(hy,y);
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| 40 | iy = hy&0x7fffffff;
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| 41 | if((ix>0x7f800000)||
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| 42 | (iy>0x7f800000)) /* x or y is NaN */
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| 43 | return x+y;
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| 44 | if(hx==0x3f800000) return atanf(y); /* x=1.0 */
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| 45 | m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
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| 46 |
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| 47 | /* when y = 0 */
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| 48 | if(iy==0) {
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| 49 | switch(m) {
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| 50 | case 0:
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| 51 | case 1: return y; /* atan(+-0,+anything)=+-0 */
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| 52 | case 2: return pi+tiny;/* atan(+0,-anything) = pi */
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| 53 | case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
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| 54 | }
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| 55 | }
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| 56 | /* when x = 0 */
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| 57 | if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
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| 58 |
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| 59 | /* when x is INF */
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| 60 | if(ix==0x7f800000) {
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| 61 | if(iy==0x7f800000) {
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| 62 | switch(m) {
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| 63 | case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
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| 64 | case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
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| 65 | case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
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| 66 | case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
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| 67 | }
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| 68 | } else {
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| 69 | switch(m) {
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| 70 | case 0: return zero ; /* atan(+...,+INF) */
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| 71 | case 1: return -zero ; /* atan(-...,+INF) */
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| 72 | case 2: return pi+tiny ; /* atan(+...,-INF) */
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| 73 | case 3: return -pi-tiny ; /* atan(-...,-INF) */
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| 74 | }
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| 75 | }
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| 76 | }
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| 77 | /* when y is INF */
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| 78 | if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
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| 79 |
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| 80 | /* compute y/x */
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| 81 | k = (iy-ix)>>23;
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| 82 | if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
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| 83 | else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
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| 84 | else z=atanf(fabsf(y/x)); /* safe to do y/x */
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| 85 | switch (m) {
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| 86 | case 0: return z ; /* atan(+,+) */
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| 87 | case 1: {
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| 88 | u_int32_t zh;
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| 89 | GET_FLOAT_WORD(zh,z);
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| 90 | SET_FLOAT_WORD(z,zh ^ 0x80000000);
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| 91 | }
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| 92 | return z ; /* atan(-,+) */
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| 93 | case 2: return pi-(z-pi_lo);/* atan(+,-) */
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| 94 | default: /* case 3 */
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| 95 | return (z-pi_lo)-pi;/* atan(-,-) */
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| 96 | }
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| 97 | }
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