Subversion Repositories openrisc_2011-10-31

/* 2009 for Newlib:  Sun's sf_ilogb.c converted to be sf_logb.c.  */

/*

 * ====================================================

 * 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.

 * ====================================================

 */

/* float logb(float x)

 * return the binary exponent of non-zero x

 * logbf(0) = -inf, raise divide-by-zero floating point exception

 * logbf(+inf|-inf) = +inf (no signal is raised)

 * logbf(NaN) = NaN (no signal is raised)

 * Per C99 recommendation, a NaN argument is returned unchanged.

 */

#include "fdlibm.h"

float

#ifdef __STDC__

logbf(float x)

#else

logbf(x)

float x;

#endif

{

        __int32_t hx,ix;

        GET_FLOAT_WORD(hx,x);

        hx &= 0x7fffffff;

        if(FLT_UWORD_IS_ZERO(hx))  {

                float  xx;

                /* arg==0:  return -inf and raise divide-by-zero exception */

                SET_FLOAT_WORD(xx,hx);  /* +0.0 */

                return -1./xx;  /* logbf(0) = -inf */

                }

        if(FLT_UWORD_IS_SUBNORMAL(hx)) {

            for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;

            return (float) ix;

        }

        else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF;   /* x==+|-inf */

        else if (FLT_UWORD_IS_NAN(hx)) return x;

        else return (float) ((hx>>23)-127);

}

#ifdef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double logb(double x)

#else

        double logb(x)

        double x;

#endif

{

        return (double) logbf((float) x);

}

#endif /* defined(_DOUBLE_IS_32BITS) */