1 /* s_tanhf.c -- float version of s_tanh.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian (at) 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 __FBSDID("$FreeBSD$"); 18 19 #include "math.h" 20 #include "math_private.h" 21 22 static const volatile float tiny = 1.0e-30; 23 static const float one=1.0, two=2.0, huge = 1.0e30; 24 25 float 26 tanhf(float x) 27 { 28 float t,z; 29 int32_t jx,ix; 30 31 GET_FLOAT_WORD(jx,x); 32 ix = jx&0x7fffffff; 33 34 /* x is INF or NaN */ 35 if(ix>=0x7f800000) { 36 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 37 else return one/x-one; /* tanh(NaN) = NaN */ 38 } 39 40 /* |x| < 9 */ 41 if (ix < 0x41100000) { /* |x|<9 */ 42 if (ix<0x39800000) { /* |x|<2**-12 */ 43 if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */ 44 } 45 if (ix>=0x3f800000) { /* |x|>=1 */ 46 t = expm1f(two*fabsf(x)); 47 z = one - two/(t+two); 48 } else { 49 t = expm1f(-two*fabsf(x)); 50 z= -t/(t+two); 51 } 52 /* |x| >= 9, return +-1 */ 53 } else { 54 z = one - tiny; /* raise inexact flag */ 55 } 56 return (jx>=0)? z: -z; 57 } 58
