| /* ef_exp.c -- float version of e_exp.c. |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected]. |
| */ |
| |
| /* |
| * ==================================================== |
| * 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 = 0,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 */ |
| } |
| |
| /* 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; |
| } |
| } |
