diff options
Diffstat (limited to 'REORG.TODO/sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c')
| -rw-r--r-- | REORG.TODO/sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c b/REORG.TODO/sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c new file mode 100644 index 0000000000..0c4508835e --- /dev/null +++ b/REORG.TODO/sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c @@ -0,0 +1,104 @@ +/* s_scalbnl.c -- long double version of s_scalbn.c. + * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz. + */ + +/* @(#)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. + * ==================================================== + */ + +#if defined(LIBM_SCCS) && !defined(lint) +static char rcsid[] = "$NetBSD: $"; +#endif + +/* + * 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> +#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 __scalbnl (long double x, 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; +} |