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 #include <sys/cdefs.h> 17 #include "math.h" 18 #include "math_private.h" 19 20 static const volatile float tiny = 1.0e-30; 21 static const float one=1.0, two=2.0, huge = 1.0e30; 22 23 float 24 tanhf(float x) 25 { 26 float t,z; 27 int32_t jx,ix; 28 29 GET_FLOAT_WORD(jx,x); 30 ix = jx&0x7fffffff; 31 32 /* x is INF or NaN */ 33 if(ix>=0x7f800000) { 34 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 35 else return one/x-one; /* tanh(NaN) = NaN */ 36 } 37 38 /* |x| < 9 */ 39 if (ix < 0x41100000) { /* |x|<9 */ 40 if (ix<0x39800000) { /* |x|<2**-12 */ 41 if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */ 42 } 43 if (ix>=0x3f800000) { /* |x|>=1 */ 44 t = expm1f(two*fabsf(x)); 45 z = one - two/(t+two); 46 } else { 47 t = expm1f(-two*fabsf(x)); 48 z= -t/(t+two); 49 } 50 /* |x| >= 9, return +-1 */ 51 } else { 52 z = one - tiny; /* raise inexact flag */ 53 } 54 return (jx>=0)? z: -z; 55 } 56