compiler/stdc/math/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 1.11 2008/08/03 17:39:54 das Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const float
  24 one =  1.0000000000e+00, /* 0x3F800000 */
  25 pi =  3.1415925026e+00, /* 0x40490fda */
  26 pio2_hi =  1.5707962513e+00; /* 0x3fc90fda */
  27 static const volatile float
  28 pio2_lo __attribute__ ((__section__(".rodata,\"a\" " SECTIONCOMMENT))) =  7.5497894159e-08; /* 0x33a22168 */
  29 static const float
  30 pS0 =  1.6666586697e-01,
  31 pS1 = -4.2743422091e-02,
  32 pS2 = -8.6563630030e-03,
  33 qS1 = -7.0662963390e-01;
  34
  35 float
  36 __ieee754_acosf(float x)
  37 {
  38         float z,p,q,r,w,s,c,df;
  39         int32_t hx,ix;
  40         GET_FLOAT_WORD(hx,x);
  41         ix = hx&0x7fffffff;
  42         if(ix>=0x3f800000) {            /* |x| >= 1 */
  43             if(ix==0x3f800000) {        /* |x| == 1 */
  44                 if(hx>0) return 0.0;    /* acos(1) = 0 */
  45                 else return pi+(float)2.0*pio2_lo;      /* acos(-1)= pi */
  46             }
  47             return (x-x)/(x-x);         /* acos(|x|>1) is NaN */
  48         }
  49         if(ix<0x3f000000) {     /* |x| < 0.5 */
  50             if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
  51             z = x*x;
  52             p = z*(pS0+z*(pS1+z*pS2));
  53             q = one+z*qS1;
  54             r = p/q;
  55             return pio2_hi - (x - (pio2_lo-x*r));
  56         } else  if (hx<0) {             /* x < -0.5 */
  57             z = (one+x)*(float)0.5;
  58             p = z*(pS0+z*(pS1+z*pS2));
  59             q = one+z*qS1;
  60             s = sqrtf(z);
  61             r = p/q;
  62             w = r*s-pio2_lo;
  63             return pi - (float)2.0*(s+w);
  64         } else {                        /* x > 0.5 */
  65             int32_t idf;
  66             z = (one-x)*(float)0.5;
  67             s = sqrtf(z);
  68             df = s;
  69             GET_FLOAT_WORD(idf,df);
  70             SET_FLOAT_WORD(df,idf&0xfffff000);
  71             c  = (z-df*df)/(s+df);
  72             p = z*(pS0+z*(pS1+z*pS2));
  73             q = one+z*qS1;
  74             r = p/q;
  75             w = r*s+c;
  76             return (float)2.0*(df+w);
  77         }
  78 }