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Differential D28872 Diff 84490 lib/msun/src/s_scalbnl.c

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lib/msun/src/s_scalbnl.c

/* @(#)s_scalbn.c 5.1 93/09/24 */ #include <math.h>
#include <float.h>
#include "math_private.h"
#include "fpmath.h"
/* /*
* ====================================================
* 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* scalbnl (long double x, int n) * scalbnl (long double x, int n)
* scalbnl(x,n) returns x* 2**n computed by exponent * scalbnl(x,n) returns x* 2**n computed by exponent
* manipulation rather than by actually performing an * manipulation rather than by actually performing an
* exponentiation or a multiplication. * exponentiation or a multiplication.
*/ */
/* #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
* We assume that a long double has a 15-bit exponent. On systems long double scalbnl(long double x, int n)
* where long double is the same as double, scalbnl() is an alias
* for scalbn(), so we don't use this routine.
*/
#include <float.h>
#include <math.h>
#include "fpmath.h"
#if LDBL_MAX_EXP != 0x4000
#error "Unsupported long double format"
#endif
static const long double
huge = 0x1p16000L,
tiny = 0x1p-16000L;
long double
scalbnl (long double x, int n)
{ {
return scalbn(x, n);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
long double scalbnl(long double x, int n)
{
union IEEEl2bits u; union IEEEl2bits u;
int k;
u.e = x; if (n > 16383) {
k = u.bits.exp; /* extract exponent */ x *= 0x1p16383L;
if (k==0) { /* 0 or subnormal x */ n -= 16383;
if ((u.bits.manh|u.bits.manl)==0) return x; /* +-0 */ if (n > 16383) {
u.e *= 0x1p+128; x *= 0x1p16383L;
k = u.bits.exp - 128; n -= 16383;
if (n< -50000) return tiny*x; /*underflow*/ if (n > 16383)
n = 16383;
} }
if (k==0x7fff) return x+x; /* NaN or Inf */ } else if (n < -16382) {
k = k+n; x *= 0x1p-16382L * 0x1p113L;
if (k >= 0x7fff) return huge*copysignl(huge,x); /* overflow */ n += 16382 - 113;
if (k > 0) /* normal result */ if (n < -16382) {
{u.bits.exp = k; return u.e;} x *= 0x1p-16382L * 0x1p113L;
if (k <= -128) { n += 16382 - 113;
if (n > 50000) /* in case integer overflow in n+k */ if (n < -16382)
return huge*copysign(huge,x); /*overflow*/ n = -16382;
else
return tiny*copysign(tiny,x); /*underflow*/
} }
k += 128; /* subnormal result */
u.bits.exp = k;
return u.e*0x1p-128;
} }
u.e = 1.0;
u.xbits.expsign = 0x3fff + n;
return x * u.e;
}
#endif
__strong_reference(scalbnl, ldexpl); __strong_reference(scalbnl, ldexpl);