| /* s_scalblnl.c -- long double version of s_scalbln.c. |
| * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz. |
| */ |
| |
| /* @(#)s_scalbln.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. |
| * ==================================================== |
| */ |
| |
| #if defined(LIBM_SCCS) && !defined(lint) |
| static char rcsid[] = "$NetBSD: $"; |
| #endif |
| |
| /* |
| * scalblnl (long double x, long int n) |
| * scalblnl(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> |
| #include <math_ldbl_opt.h> |
| |
| static const long double |
| twolm54 = 5.55111512312578270212e-17, /* 0x3C90000000000000, 0 */ |
| huge = 1.0E+300L, |
| tiny = 1.0E-300L; |
| static const double |
| two54 = 1.80143985094819840000e+16, /* 0x4350000000000000 */ |
| twom54 = 5.55111512312578270212e-17; /* 0x3C90000000000000 */ |
| |
| long double __scalblnl (long double x, long int n) |
| { |
| int64_t k,l,hx,lx; |
| union { int64_t i; double d; } u; |
| double xhi, xlo; |
| |
| ldbl_unpack (x, &xhi, &xlo); |
| EXTRACT_WORDS64 (hx, xhi); |
| EXTRACT_WORDS64 (lx, xlo); |
| k = (hx>>52)&0x7ff; /* extract exponent */ |
| l = (lx>>52)&0x7ff; |
| if (k==0) { /* 0 or subnormal x */ |
| if ((hx&0x7fffffffffffffffULL)==0) return x; /* +-0 */ |
| u.i = hx; |
| u.d *= two54; |
| hx = u.i; |
| k = ((hx>>52)&0x7ff) - 54; |
| } |
| else if (k==0x7ff) return x+x; /* NaN or Inf */ |
| if (n< -50000) return tiny*__copysignl(tiny,x); /*underflow */ |
| if (n> 50000 || k+n > 0x7fe) |
| 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 (k > 0) { /* normal result */ |
| hx = (hx&0x800fffffffffffffULL)|(k<<52); |
| if ((lx & 0x7fffffffffffffffULL) == 0) { /* low part +-0 */ |
| INSERT_WORDS64 (xhi, hx); |
| INSERT_WORDS64 (xlo, lx); |
| x = ldbl_pack (xhi, xlo); |
| return x; |
| } |
| if (l == 0) { /* low part subnormal */ |
| u.i = lx; |
| u.d *= two54; |
| lx = u.i; |
| l = ((lx>>52)&0x7ff) - 54; |
| } |
| l = l + n; |
| if (l > 0) |
| lx = (lx&0x800fffffffffffffULL)|(l<<52); |
| else if (l <= -54) |
| lx = (lx&0x8000000000000000ULL); |
| else { |
| l += 54; |
| u.i = (lx&0x800fffffffffffffULL)|(l<<52); |
| u.d *= twom54; |
| lx = u.i; |
| } |
| INSERT_WORDS64 (xhi, hx); |
| INSERT_WORDS64 (xlo, lx); |
| x = ldbl_pack (xhi, xlo); |
| return x; |
| } |
| if (k <= -54) |
| return tiny*__copysignl(tiny,x); /*underflow*/ |
| k += 54; /* subnormal result */ |
| lx &= 0x8000000000000000ULL; |
| hx &= 0x800fffffffffffffULL; |
| INSERT_WORDS64 (xhi, hx|(k<<52)); |
| INSERT_WORDS64 (xlo, lx); |
| x = ldbl_pack (xhi, xlo); |
| return x*twolm54; |
| } |
| long_double_symbol (libm, __scalblnl, scalblnl); |
