| /* s_scalbnl.c -- long double version of s_scalbn.c. |
| * Conversion to long double by Ulrich Drepper, |
| * Cygnus Support, drepper@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. |
| * ==================================================== |
| */ |
| |
| /* |
| * scalbnl (long double x, int n) |
| * scalbnl(x,n) returns x* 2**n computed by exponent |
| * manipulation rather than by actually performing an |
| * exponentiation or a multiplication. |
| */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| |
| static const long double |
| two63 = 0x1p63L, |
| twom64 = 0x1p-64L, |
| huge = 1.0e+4900L, |
| tiny = 1.0e-4900L; |
| |
| long double |
| __scalblnl (long double x, long int n) |
| { |
| int32_t k,es,hx,lx; |
| GET_LDOUBLE_WORDS(es,hx,lx,x); |
| k = es&0x7fff; /* extract exponent */ |
| if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */ |
| if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ |
| x *= two63; |
| GET_LDOUBLE_EXP(es,x); |
| k = (es&0x7fff) - 63; |
| } |
| if (__builtin_expect(k==0x7fff, 0)) return x+x; /* NaN or Inf */ |
| if (__builtin_expect(n< -50000, 0)) |
| return tiny*__copysignl(tiny,x); |
| if (__builtin_expect(n> 50000 || k+n > 0x7ffe, 0)) |
| return huge*__copysignl(huge,x); /* overflow */ |
| /* Now k and n are bounded we know that k = k+n does not |
| overflow. */ |
| k = k+n; |
| if (__builtin_expect(k > 0, 1)) /* normal result */ |
| {SET_LDOUBLE_EXP(x,(es&0x8000)|k); return x;} |
| if (k <= -64) |
| return tiny*__copysignl(tiny,x); /*underflow*/ |
| k += 64; /* subnormal result */ |
| SET_LDOUBLE_EXP(x,(es&0x8000)|k); |
| return x*twom64; |
| } |
