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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [s_scalbln.c] - Rev 298
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/* @(#)s_scalbn.c 5.1 93/09/24 */ /* * ==================================================== * 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. * ==================================================== */ /* * scalbn (double x, int n) * scalbn(x,n) returns x* 2**n computed by exponent * manipulation rather than by actually performing an * exponentiation or a multiplication. */ #include "fdlibm.h" #ifndef _DOUBLE_IS_32BITS #ifdef __STDC__ static const double #else static double #endif two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; #ifdef __STDC__ double scalbln (double x, long int n) #else double scalbln (x,n) double x; long int n; #endif { __int32_t k,hx,lx; EXTRACT_WORDS(hx,lx,x); k = (hx&0x7ff00000)>>20; /* extract exponent */ if (k==0) { /* 0 or subnormal x */ if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ x *= two54; GET_HIGH_WORD(hx,x); k = ((hx&0x7ff00000)>>20) - 54; } if (k==0x7ff) return x+x; /* NaN or Inf */ k = k+n; if (n> 50000 || k > 0x7fe) return huge*copysign(huge,x); /* overflow */ if (n< -50000) return tiny*copysign(tiny,x); /*underflow*/ if (k > 0) /* normal result */ {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;} if (k <= -54) return tiny*copysign(tiny,x); /*underflow*/ k += 54; /* subnormal result */ SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x*twom54; } #endif /* _DOUBLE_IS_32BITS */
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