ilogb.c File Reference

#include <limits.h>
#include "libm.h"

Include dependency graph for ilogb.c:

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Functions
int	ilogb (double x)

Function Documentation

ilogb()

int ilogb

(

double

x

)

Definition at line 14 of file ilogb.c.

{
    #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(fp_barrierf(0.0f)/0.0f);
            return FP_ILOGB0;
        }
        /* subnormal x */
        for (e = -0x3ff; i>>63 == 0; e--, i<<=1);
        return e;
    }
    if (e == 0x7ff) {
        FORCE_EVAL(fp_barrierf(0.0f)/0.0f);
        return i<<12 ? FP_ILOGBNAN : INT_MAX;
    }
    return e - 0x3ff;
}

Referenced by logb().