diff options
Diffstat (limited to 'sysdeps/libm-ieee754/e_expf.c')
| -rw-r--r-- | sysdeps/libm-ieee754/e_expf.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/sysdeps/libm-ieee754/e_expf.c b/sysdeps/libm-ieee754/e_expf.c new file mode 100644 index 0000000000..80af17918f --- /dev/null +++ b/sysdeps/libm-ieee754/e_expf.c @@ -0,0 +1,104 @@ +/* e_expf.c -- float version of e_exp.c. + * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. + */ + +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunPro, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +#if defined(LIBM_SCCS) && !defined(lint) +static char rcsid[] = "$NetBSD: e_expf.c,v 1.5 1995/05/10 20:45:05 jtc Exp $"; +#endif + +#include "math.h" +#include "math_private.h" + +static const volatile float huge = 1.0e+30; + +#ifdef __STDC__ +static const float +#else +static float +#endif +one = 1.0, +halF[2] = {0.5,-0.5,}, +twom100 = 7.8886090522e-31, /* 2**-100=0x0d800000 */ +o_threshold= 8.8721679688e+01, /* 0x42b17180 */ +u_threshold= -1.0397208405e+02, /* 0xc2cff1b5 */ +ln2HI[2] ={ 6.9313812256e-01, /* 0x3f317180 */ + -6.9313812256e-01,}, /* 0xbf317180 */ +ln2LO[2] ={ 9.0580006145e-06, /* 0x3717f7d1 */ + -9.0580006145e-06,}, /* 0xb717f7d1 */ +invln2 = 1.4426950216e+00, /* 0x3fb8aa3b */ +P1 = 1.6666667163e-01, /* 0x3e2aaaab */ +P2 = -2.7777778450e-03, /* 0xbb360b61 */ +P3 = 6.6137559770e-05, /* 0x388ab355 */ +P4 = -1.6533901999e-06, /* 0xb5ddea0e */ +P5 = 4.1381369442e-08; /* 0x3331bb4c */ + +#ifdef __STDC__ + float __ieee754_expf(float x) /* default IEEE double exp */ +#else + float __ieee754_expf(x) /* default IEEE double exp */ + float x; +#endif +{ + float y,hi,lo,c,t; + int32_t k,xsb; + u_int32_t hx; + + GET_FLOAT_WORD(hx,x); + xsb = (hx>>31)&1; /* sign bit of x */ + hx &= 0x7fffffff; /* high word of |x| */ + + /* filter out non-finite argument */ + if(hx >= 0x42b17218) { /* if |x|>=88.721... */ + if(hx>0x7f800000) + return x+x; /* NaN */ + if(hx==0x7f800000) + return (xsb==0)? x:0.0; /* exp(+-inf)={inf,0} */ + if(x > o_threshold) return huge*huge; /* overflow */ + if(x < u_threshold) return twom100*twom100; /* underflow */ + } + + /* argument reduction */ + if(hx > 0x3eb17218) { /* if |x| > 0.5 ln2 */ + if(hx < 0x3F851592) { /* and |x| < 1.5 ln2 */ + hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb; + } else { + k = invln2*x+halF[xsb]; + t = k; + hi = x - t*ln2HI[0]; /* t*ln2HI is exact here */ + lo = t*ln2LO[0]; + } + x = hi - lo; + } + else if(hx < 0x31800000) { /* when |x|<2**-28 */ + if(huge+x>one) return one+x;/* trigger inexact */ + } + else k = 0; + + /* x is now in primary range */ + t = x*x; + c = x - t*(P1+t*(P2+t*(P3+t*(P4+t*P5)))); + if(k==0) return one-((x*c)/(c-(float)2.0)-x); + else y = one-((lo-(x*c)/((float)2.0-c))-hi); + if(k >= -125) { + u_int32_t hy; + GET_FLOAT_WORD(hy,y); + SET_FLOAT_WORD(y,hy+(k<<23)); /* add k to y's exponent */ + return y; + } else { + u_int32_t hy; + GET_FLOAT_WORD(hy,y); + SET_FLOAT_WORD(y,hy+((k+100)<<23)); /* add k to y's exponent */ + return y*twom100; + } +} |