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Fixed fdlibm[+cygnus] logbf() and logb() on denormals. Adjustment

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according to the highest nonzero bit in a denormal was missing.

fdlibm ilogbf() and ilogb() have always had the adjustment, but only
use a small part of their method for handling denormals; use the
normalization method in log[f]() for the main part.
This commit is contained in:
Bruce Evans 2005-12-03 11:57:19 +00:00
parent 4b66957aa4
commit 00b1756b1e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=153049
2 changed files with 20 additions and 8 deletions
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14
lib/msun/src/s_logb.c
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@ -23,6 +23,9 @@ static char rcsid[] = "$FreeBSD$";
#include "math.h"
#include "math_private.h"
static const double
two54 = 1.80143985094819840000e+16; /* 43500000 00000000 */
double
logb(double x)
{
@ -31,8 +34,11 @@ logb(double x)
ix &= 0x7fffffff; /* high |x| */
if((ix|lx)==0) return -1.0/fabs(x);
if(ix>=0x7ff00000) return x*x;
if((ix>>=20)==0) /* IEEE 754 logb */
return -1022.0;
else
return (double) (ix-1023);
if(ix<0x00100000) {
x *= two54; /* convert subnormal x to normal */
GET_FLOAT_WORD(ix,x);
ix &= 0x7fffffff;
return (float) ((ix>>20)-1023-54);
} else
return (double) ((ix>>20)-1023);
}

14
lib/msun/src/s_logbf.c
View file

@ -20,6 +20,9 @@ static char rcsid[] = "$FreeBSD$";
#include "math.h"
#include "math_private.h"
static const float
two25 = 3.355443200e+07; /* 0x4c000000 */
float
logbf(float x)
{
@ -28,8 +31,11 @@ logbf(float x)
ix &= 0x7fffffff; /* high |x| */
if(ix==0) return (float)-1.0/fabsf(x);
if(ix>=0x7f800000) return x*x;
if((ix>>=23)==0) /* IEEE 754 logb */
return -126.0;
else
return (float) (ix-127);
if(ix<0x00800000) {
x *= two25; /* convert subnormal x to normal */
GET_FLOAT_WORD(ix,x);
ix &= 0x7fffffff;
return (float) ((ix>>23)-127-25);
} else
return (float) ((ix>>23)-127);
}