compiler/mlib/e_coshf.c

   1 /* e_coshf.c -- float version of e_cosh.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_coshf.c,v 1.5 1999/08/28 00:06:29 peter Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float one = 1.0, half=0.5, huge = 1.0e30;
  25 #else
  26 static float one = 1.0, half=0.5, huge = 1.0e30;
  27 #endif
  28
  29 #ifdef __STDC__
  30         float __ieee754_coshf(float x)
  31 #else
  32         float __ieee754_coshf(x)
  33         float x;
  34 #endif
  35 {
  36         float t,w;
  37         int32_t ix;
  38
  39         GET_FLOAT_WORD(ix,x);
  40         ix &= 0x7fffffff;
  41
  42     /* x is INF or NaN */
  43         if(ix>=0x7f800000) return x*x;
  44
  45     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
  46         if(ix<0x3eb17218) {
  47             t = expm1f(fabsf(x));
  48             w = one+t;
  49             if (ix<0x24000000) return w;        /* cosh(tiny) = 1 */
  50             return one+(t*t)/(w+w);
  51         }
  52
  53     /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
  54         if (ix < 0x41b00000) {
  55                 t = __ieee754_expf(fabsf(x));
  56                 return half*t+half/t;
  57         }
  58
  59     /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
  60         if (ix < 0x42b17180)  return half*__ieee754_expf(fabsf(x));
  61
  62     /* |x| in [log(maxdouble), overflowthresold] */
  63         if (ix<=0x42b2d4fc) {
  64             w = __ieee754_expf(half*fabsf(x));
  65             t = half*w;
  66             return t*w;
  67         }
  68
  69     /* |x| > overflowthresold, cosh(x) overflow */
  70         return huge*huge;
  71 }