Szabolcs Nagy
4cec31fc23
* consistent code style * explicit union instead of typedef for double and float bit access * turn FENV_ACCESS ON to make 0/0.0f raise invalid flag * (untested) ld128 version of ilogbl (used by logbl which has ld128 support)
27 lines
445 B
C
27 lines
445 B
C
#include <limits.h>
|
|
#include "libm.h"
|
|
|
|
int ilogb(double x)
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
union {double f; uint64_t i;} u = {x};
|
|
uint64_t i = u.i;
|
|
int e = i>>52 & 0x7ff;
|
|
|
|
if (!e) {
|
|
i <<= 12;
|
|
if (i == 0) {
|
|
FORCE_EVAL(0/0.0f);
|
|
return FP_ILOGB0;
|
|
}
|
|
/* subnormal x */
|
|
for (e = -0x3ff; i>>63 == 0; e--, i<<=1);
|
|
return e;
|
|
}
|
|
if (e == 0x7ff) {
|
|
FORCE_EVAL(0/0.0f);
|
|
return i<<12 ? FP_ILOGBNAN : INT_MAX;
|
|
}
|
|
return e - 0x3ff;
|
|
}
|