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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [sf_logb.c] - Blame information for rev 207

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1 207 jeremybenn
/* 2009 for Newlib:  Sun's sf_ilogb.c converted to be sf_logb.c.  */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/* float logb(float x)
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 * return the binary exponent of non-zero x
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 * logbf(0) = -inf, raise divide-by-zero floating point exception
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 * logbf(+inf|-inf) = +inf (no signal is raised)
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 * logbf(NaN) = NaN (no signal is raised)
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 * Per C99 recommendation, a NaN argument is returned unchanged.
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 */
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#include "fdlibm.h"
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float
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#ifdef __STDC__
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logbf(float x)
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#else
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logbf(x)
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float x;
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#endif
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{
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        __int32_t hx,ix;
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        GET_FLOAT_WORD(hx,x);
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        hx &= 0x7fffffff;
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        if(FLT_UWORD_IS_ZERO(hx))  {
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                float  xx;
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                /* arg==0:  return -inf and raise divide-by-zero exception */
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                SET_FLOAT_WORD(xx,hx);  /* +0.0 */
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                return -1./xx;  /* logbf(0) = -inf */
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                }
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        if(FLT_UWORD_IS_SUBNORMAL(hx)) {
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            for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
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            return (float) ix;
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        }
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        else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF;   /* x==+|-inf */
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        else if (FLT_UWORD_IS_NAN(hx)) return x;
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        else return (float) ((hx>>23)-127);
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}
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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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        double logb(double x)
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#else
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        double logb(x)
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        double x;
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#endif
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{
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        return (double) logbf((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */

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