121 lines
3.5 KiB
C
121 lines
3.5 KiB
C
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/* @(#)e_atan2.c 1.3 95/01/18 */
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/* FreeBSD: head/lib/msun/src/e_atan2.c 176451 2008-02-22 02:30:36Z das */
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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 SunSoft, 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 "cdefs-compat.h"
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//__FBSDID("$FreeBSD: src/lib/msun/src/e_atan2l.c,v 1.3 2008/08/02 19:17:00 das Exp $");
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/*
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* See comments in e_atan2.c.
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* Converted to long double by David Schultz <das@FreeBSD.ORG>.
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*/
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#include <float.h>
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#include <openlibm_math.h>
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#include "invtrig.h"
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#include "math_private.h"
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static volatile long double
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tiny = 1.0e-300;
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static const long double
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zero = 0.0;
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#ifdef __i386__
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/* XXX Work around the fact that gcc truncates long double constants on i386 */
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static volatile double
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pi1 = 3.14159265358979311600e+00, /* 0x1.921fb54442d18p+1 */
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pi2 = 1.22514845490862001043e-16; /* 0x1.1a80000000000p-53 */
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#define pi ((long double)pi1 + pi2)
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#else
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static const long double
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pi = 3.14159265358979323846264338327950280e+00L;
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#endif
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OLM_DLLEXPORT long double
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atan2l(long double y, long double x)
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{
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union IEEEl2bits ux, uy;
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long double z;
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int32_t k,m;
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int16_t exptx, expsignx, expty, expsigny;
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uy.e = y;
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expsigny = uy.xbits.expsign;
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expty = expsigny & 0x7fff;
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ux.e = x;
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expsignx = ux.xbits.expsign;
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exptx = expsignx & 0x7fff;
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if ((exptx==BIAS+LDBL_MAX_EXP &&
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((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)!=0) || /* x is NaN */
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(expty==BIAS+LDBL_MAX_EXP &&
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((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* y is NaN */
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return x+y;
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if (expsignx==BIAS && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
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return atanl(y); /* x=1.0 */
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m = ((expsigny>>15)&1)|((expsignx>>14)&2); /* 2*sign(x)+sign(y) */
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/* when y = 0 */
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if(expty==0 && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)==0) {
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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(exptx==0 && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)==0)
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return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
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/* when x is INF */
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if(exptx==BIAS+LDBL_MAX_EXP) {
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if(expty==BIAS+LDBL_MAX_EXP) {
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switch(m) {
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case 0: return pio2_hi*0.5+tiny;/* atan(+INF,+INF) */
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case 1: return -pio2_hi*0.5-tiny;/* atan(-INF,+INF) */
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case 2: return 1.5*pio2_hi+tiny;/*atan(+INF,-INF)*/
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case 3: return -1.5*pio2_hi-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(expty==BIAS+LDBL_MAX_EXP)
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return (expsigny<0)? -pio2_hi-tiny: pio2_hi+tiny;
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/* compute y/x */
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k = expty-exptx;
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if(k > LDBL_MANT_DIG+2) { /* |y/x| huge */
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z=pio2_hi+pio2_lo;
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m&=1;
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}
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else if(expsignx<0&&k<-LDBL_MANT_DIG-2) z=0.0; /* |y/x| tiny, x<0 */
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else z=atanl(fabsl(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: 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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