compiler/mlib/s_tanhf.c

   1 /* s_tanhf.c -- float version of s_tanh.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/s_tanhf.c,v 1.8 2005/12/11 11:40:55 bde Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const float one=1.0, two=2.0, tiny = 1.0e-30, huge = 1.0e30;
  24 float
  25 tanhf(float x)
  26 {
  27         float t,z;
  28         int32_t jx,ix;
  29
  30         GET_FLOAT_WORD(jx,x);
  31         ix = jx&0x7fffffff;
  32
  33     /* x is INF or NaN */
  34         if(ix>=0x7f800000) {
  35             if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
  36             else       return one/x-one;    /* tanh(NaN) = NaN */
  37         }
  38
  39     /* |x| < 9 */
  40         if (ix < 0x41100000) {          /* |x|<9 */
  41             if (ix<0x39800000) {        /* |x|<2**-12 */
  42                 if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */
  43             }
  44             if (ix>=0x3f800000) {       /* |x|>=1  */
  45                 t = expm1f(two*fabsf(x));
  46                 z = one - two/(t+two);
  47             } else {
  48                 t = expm1f(-two*fabsf(x));
  49                 z= -t/(t+two);
  50             }
  51     /* |x| >= 9, return +-1 */
  52         } else {
  53             z = one - tiny;             /* raise inexact flag */
  54         }
  55         return (jx>=0)? z: -z;
  56 }