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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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55
libc/math/ilogbl.c Normal file
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#include "libc/limits.h"
#include "libc/math/libm.h"
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
int ilogbl(long double x)
{
return ilogb(x);
}
#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
int ilogbl(long double x)
{
#pragma STDC FENV_ACCESS ON
union ldshape u = {x};
uint64_t m = u.i.m;
int e = u.i.se & 0x7fff;
if (!e) {
if (m == 0) {
FORCE_EVAL(0/0.0f);
return FP_ILOGB0;
}
/* subnormal x */
for (e = -0x3fff+1; m>>63 == 0; e--, m<<=1);
return e;
}
if (e == 0x7fff) {
FORCE_EVAL(0/0.0f);
return m<<1 ? FP_ILOGBNAN : INT_MAX;
}
return e - 0x3fff;
}
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
int ilogbl(long double x)
{
#pragma STDC FENV_ACCESS ON
union ldshape u = {x};
int e = u.i.se & 0x7fff;
if (!e) {
if (x == 0) {
FORCE_EVAL(0/0.0f);
return FP_ILOGB0;
}
/* subnormal x */
x *= 0x1p120;
return ilogbl(x) - 120;
}
if (e == 0x7fff) {
FORCE_EVAL(0/0.0f);
u.i.se = 0;
return u.f ? FP_ILOGBNAN : INT_MAX;
}
return e - 0x3fff;
}
#endif