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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libm/] [math/] [ef_exp.c] - Rev 859
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/* ef_exp.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. * ==================================================== */ #include "fdlibm.h" #ifdef __v810__ #define const #endif #ifdef __STDC__ static const float #else static float #endif one = 1.0, halF[2] = {0.5,-0.5,}, huge = 1.0e+30, twom100 = 7.8886090522e-31, /* 2**-100=0x0d800000 */ 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,sx; __uint32_t hx; GET_FLOAT_WORD(sx,x); xsb = (sx>>31)&1; /* sign bit of x */ hx = sx & 0x7fffffff; /* high word of |x| */ /* filter out non-finite argument */ if(FLT_UWORD_IS_NAN(hx)) return x+x; /* NaN */ if(FLT_UWORD_IS_INFINITE(hx)) return (xsb==0)? x:0.0; /* exp(+-inf)={inf,0} */ if(sx > FLT_UWORD_LOG_MAX) return huge*huge; /* overflow */ if(sx < 0 && hx > FLT_UWORD_LOG_MIN) 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) { __uint32_t hy; GET_FLOAT_WORD(hy,y); SET_FLOAT_WORD(y,hy+(k<<23)); /* add k to y's exponent */ return y; } else { __uint32_t hy; GET_FLOAT_WORD(hy,y); SET_FLOAT_WORD(y,hy+((k+100)<<23)); /* add k to y's exponent */ return y*twom100; } }
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