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/*
* ====================================================
* 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.
* ====================================================
*/
/* ilogb(double x)
* return the binary exponent of x
* ilogb(+-0) = FP_ILOGB0
* ilogb(+-inf) = INT_MAX
* ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
*/
#include "math.h"
#include "math_private.h"
int ilogb(double x)
{
int32_t hx,lx,ix;
GET_HIGH_WORD(hx, x);
hx &= 0x7fffffff;
if (hx < 0x00100000) {
GET_LOW_WORD(lx, x);
if ((hx|lx)==0) /* +-0, ilogb(0) = FP_ILOGB0 */
return FP_ILOGB0;
/* subnormal x */
ix = -1043;
if (hx != 0) {
ix = -1022;
lx = (hx << 11);
}
/* each leading zero mantissa bit makes exponent smaller */
for (; lx > 0; lx <<= 1)
ix--;
return ix;
}
if (hx < 0x7ff00000) /* normal x */
return (hx>>20) - 1023;
if (FP_ILOGBNAN != (~0U >> 1)) {
GET_LOW_WORD(lx, x);
if (hx == 0x7ff00000 && lx == 0) /* +-inf */
return ~0U >> 1; /* = INT_MAX */
}
/* NAN. ilogb(NAN) = FP_ILOGBNAN */
return FP_ILOGBNAN;
}
libm_hidden_def(ilogb)
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