acosl.c raw

   1  /* origin: FreeBSD /usr/src/lib/msun/src/e_acosl.c */
   2  /*
   3   * ====================================================
   4   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5   *
   6   * Developed at SunSoft, a Sun Microsystems, Inc. business.
   7   * Permission to use, copy, modify, and distribute this
   8   * software is freely granted, provided that this notice
   9   * is preserved.
  10   * ====================================================
  11   */
  12  /*
  13   * See comments in acos.c.
  14   * Converted to long double by David Schultz <das@FreeBSD.ORG>.
  15   */
  16  
  17  #include "libm.h"
  18  
  19  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
  20  long double acosl(long double x)
  21  {
  22  	return acos(x);
  23  }
  24  #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
  25  #include "__invtrigl.h"
  26  #if LDBL_MANT_DIG == 64
  27  #define CLEARBOTTOM(u) (u.i.m &= -1ULL << 32)
  28  #elif LDBL_MANT_DIG == 113
  29  #define CLEARBOTTOM(u) (u.i.lo = 0)
  30  #endif
  31  
  32  long double acosl(long double x)
  33  {
  34  	union ldshape u = {x};
  35  	long double z, s, c, f;
  36  	uint16_t e = u.i.se & 0x7fff;
  37  
  38  	/* |x| >= 1 or nan */
  39  	if (e >= 0x3fff) {
  40  		if (x == 1)
  41  			return 0;
  42  		if (x == -1)
  43  			return 2*pio2_hi + 0x1p-120f;
  44  		return 0/(x-x);
  45  	}
  46  	/* |x| < 0.5 */
  47  	if (e < 0x3fff - 1) {
  48  		if (e < 0x3fff - LDBL_MANT_DIG - 1)
  49  			return pio2_hi + 0x1p-120f;
  50  		return pio2_hi - (__invtrigl_R(x*x)*x - pio2_lo + x);
  51  	}
  52  	/* x < -0.5 */
  53  	if (u.i.se >> 15) {
  54  		z = (1 + x)*0.5;
  55  		s = sqrtl(z);
  56  		return 2*(pio2_hi - (__invtrigl_R(z)*s - pio2_lo + s));
  57  	}
  58  	/* x > 0.5 */
  59  	z = (1 - x)*0.5;
  60  	s = sqrtl(z);
  61  	u.f = s;
  62  	CLEARBOTTOM(u);
  63  	f = u.f;
  64  	c = (z - f*f)/(s + f);
  65  	return 2*(__invtrigl_R(z)*s + c + f);
  66  }
  67  #endif
  68