compiler/stdc/math/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 1.9 2008/02/22 02:30:36 das Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const volatile float tiny __attribute__ ((__section__(".rodata,\"a\" " SECTIONCOMMENT))) = 1.0e-30;
  24 static const float one=1.0, two=2.0, huge = 1.0e30;
  25
  26 float
  27 tanhf(float x)
  28 {
  29         float t,z;
  30         int32_t jx,ix;
  31
  32         GET_FLOAT_WORD(jx,x);
  33         ix = jx&0x7fffffff;
  34
  35     /* x is INF or NaN */
  36         if(ix>=0x7f800000) {
  37             if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
  38             else       return one/x-one;    /* tanh(NaN) = NaN */
  39         }
  40
  41     /* |x| < 9 */
  42         if (ix < 0x41100000) {          /* |x|<9 */
  43             if (ix<0x39800000) {        /* |x|<2**-12 */
  44                 if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */
  45             }
  46             if (ix>=0x3f800000) {       /* |x|>=1  */
  47                 t = expm1f(two*fabsf(x));
  48                 z = one - two/(t+two);
  49             } else {
  50                 t = expm1f(-two*fabsf(x));
  51                 z= -t/(t+two);
  52             }
  53     /* |x| >= 9, return +-1 */
  54         } else {
  55             z = one - tiny;             /* raise inexact flag */
  56         }
  57         return (jx>=0)? z: -z;
  58 }