lib/msun/src/e_acosf.c

   1 /* e_acosf.c -- float version of e_acos.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #ifndef lint
  17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_acosf.c,v 1.6 1999/08/28 00:06:27 peter Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float
  25 #else
  26 static float
  27 #endif
  28 one =  1.0000000000e+00, /* 0x3F800000 */
  29 pi =  3.1415925026e+00, /* 0x40490fda */
  30 pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
  31 pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
  32 pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
  33 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
  34 pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
  35 pS3 = -4.0055535734e-02, /* 0xbd241146 */
  36 pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
  37 pS5 =  3.4793309169e-05, /* 0x3811ef08 */
  38 qS1 = -2.4033949375e+00, /* 0xc019d139 */
  39 qS2 =  2.0209457874e+00, /* 0x4001572d */
  40 qS3 = -6.8828397989e-01, /* 0xbf303361 */
  41 qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
  42
  43 #ifdef __STDC__
  44         float __ieee754_acosf(float x)
  45 #else
  46         float __ieee754_acosf(x)
  47         float x;
  48 #endif
  49 {
  50         float z,p,q,r,w,s,c,df;
  51         int32_t hx,ix;
  52         GET_FLOAT_WORD(hx,x);
  53         ix = hx&0x7fffffff;
  54         if(ix==0x3f800000) {            /* |x|==1 */
  55             if(hx>0) return 0.0;        /* acos(1) = 0  */
  56             else return pi+(float)2.0*pio2_lo;  /* acos(-1)= pi */
  57         } else if(ix>0x3f800000) {      /* |x| >= 1 */
  58             return (x-x)/(x-x);         /* acos(|x|>1) is NaN */
  59         }
  60         if(ix<0x3f000000) {     /* |x| < 0.5 */
  61             if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
  62             z = x*x;
  63             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
  64             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
  65             r = p/q;
  66             return pio2_hi - (x - (pio2_lo-x*r));
  67         } else  if (hx<0) {             /* x < -0.5 */
  68             z = (one+x)*(float)0.5;
  69             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
  70             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
  71             s = __ieee754_sqrtf(z);
  72             r = p/q;
  73             w = r*s-pio2_lo;
  74             return pi - (float)2.0*(s+w);
  75         } else {                        /* x > 0.5 */
  76             int32_t idf;
  77             z = (one-x)*(float)0.5;
  78             s = __ieee754_sqrtf(z);
  79             df = s;
  80             GET_FLOAT_WORD(idf,df);
  81             SET_FLOAT_WORD(df,idf&0xfffff000);
  82             c  = (z-df*df)/(s+df);
  83             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
  84             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
  85             r = p/q;
  86             w = r*s+c;
  87             return (float)2.0*(df+w);
  88         }
  89 }