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102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
/* ef_atan2.c -- float version of e_atan2.c.
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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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 SunPro, 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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#include "fdlibm.h"
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#ifdef __STDC__
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static const float
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#else
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static float
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#endif
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tiny = 1.0e-30,
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zero = 0.0,
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pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
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pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
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pi = 3.1415927410e+00, /* 0x40490fdb */
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pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */
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#ifdef __STDC__
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float __ieee754_atan2f(float y, float x)
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#else
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float __ieee754_atan2f(y,x)
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float y,x;
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#endif
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{
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float z;
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__int32_t k,m,hx,hy,ix,iy;
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GET_FLOAT_WORD(hx,x);
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ix = hx&0x7fffffff;
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GET_FLOAT_WORD(hy,y);
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iy = hy&0x7fffffff;
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if(FLT_UWORD_IS_NAN(ix)||
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FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */
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return x+y;
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if(hx==0x3f800000) return atanf(y); /* x=1.0 */
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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(FLT_UWORD_IS_ZERO(iy)) {
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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(FLT_UWORD_IS_ZERO(ix)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
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/* when x is INF */
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if(FLT_UWORD_IS_INFINITE(ix)) {
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if(FLT_UWORD_IS_INFINITE(iy)) {
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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 (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
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case 3: return (float)-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 zero ; /* atan(+...,+INF) */
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case 1: return -zero ; /* 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(FLT_UWORD_IS_INFINITE(iy)) 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)>>23;
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if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
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else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
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else z=atanf(fabsf(y/x)); /* safe to do y/x */
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switch (m) {
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case 0: return z ; /* atan(+,+) */
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case 1: {
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__uint32_t zh;
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GET_FLOAT_WORD(zh,z);
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SET_FLOAT_WORD(z,zh ^ 0x80000000);
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}
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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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