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  1. /* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
  2. /* e_asinf.c -- float version of e_asin.c.
  3.  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
  4.  */
  5.  
  6. /*
  7.  * ====================================================
  8.  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  9.  *
  10.  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11.  * Permission to use, copy, modify, and distribute this
  12.  * software is freely granted, provided that this notice
  13.  * is preserved.
  14.  * ====================================================
  15.  */
  16.  
  17. #if defined(LIBM_SCCS) && !defined(lint)
  18. static char rcsid[] = "$Id: e_asinf.c,v 1.2 1994/08/18 23:05:05 jtc Exp $";
  19. #endif
  20.  
  21. #include "math.h"
  22. #include "math_private.h"
  23.  
  24. #ifdef __STDC__
  25. static const float
  26. #else
  27. static float
  28. #endif
  29. one =  1.0000000000e+00, /* 0x3F800000 */
  30. huge =  1.000e+30,
  31. pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
  32. pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
  33. pio4_hi =  7.8539818525e-01, /* 0x3f490fdb */
  34.         /* coefficient for R(x^2) */
  35. pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
  36. pS1 = -3.2556581497e-01, /* 0xbea6b090 */
  37. pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
  38. pS3 = -4.0055535734e-02, /* 0xbd241146 */
  39. pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
  40. pS5 =  3.4793309169e-05, /* 0x3811ef08 */
  41. qS1 = -2.4033949375e+00, /* 0xc019d139 */
  42. qS2 =  2.0209457874e+00, /* 0x4001572d */
  43. qS3 = -6.8828397989e-01, /* 0xbf303361 */
  44. qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
  45.  
  46. #ifdef __STDC__
  47.         float __ieee754_asinf(float x)
  48. #else
  49.         float __ieee754_asinf(x)
  50.         float x;
  51. #endif
  52. {
  53.         float t,w,p,q,c,r,s;
  54.         int32_t hx,ix;
  55.         GET_FLOAT_WORD(hx,x);
  56.         ix = hx&0x7fffffff;
  57.         if(ix==0x3f800000) {
  58.                 /* asin(1)=+-pi/2 with inexact */
  59.             return x*pio2_hi+x*pio2_lo;
  60.         } else if(ix> 0x3f800000) {     /* |x|>= 1 */
  61.             return (x-x)/(x-x);         /* asin(|x|>1) is NaN */  
  62.         } else if (ix<0x3f000000) {     /* |x|<0.5 */
  63.             if(ix<0x32000000) {         /* if |x| < 2**-27 */
  64.                 if(huge+x>one) return x;/* return x with inexact if x!=0*/
  65.             } else
  66.                 t = x*x;
  67.                 p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  68.                 q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  69.                 w = p/q;
  70.                 return x+x*w;
  71.         }
  72.         /* 1> |x|>= 0.5 */
  73.         w = one-fabsf(x);
  74.         t = w*(float)0.5;
  75.         p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  76.         q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  77.         s = sqrtf(t);
  78.         if(ix>=0x3F79999A) {    /* if |x| > 0.975 */
  79.             w = p/q;
  80.             t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
  81.         } else {
  82.             int32_t iw;
  83.             w  = s;
  84.             GET_FLOAT_WORD(iw,w);
  85.             SET_FLOAT_WORD(w,iw&0xfffff000);
  86.             c  = (t-w*w)/(s+w);
  87.             r  = p/q;
  88.             p  = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
  89.             q  = pio4_hi-(float)2.0*w;
  90.             t  = pio4_hi-(p-q);
  91.         }    
  92.         if(hx>0) return t; else return -t;    
  93. }
  94.