36 lines
1.2 KiB
C
36 lines
1.2 KiB
C
/* @(#)12 1.5 src/lib/math/ilog2.h, sw.lib, sdk_pub 10/11/05 15:35:56 */
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/* -------------------------------------------------------------- */
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/* (C) Copyright 2001,2005, */
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/* International Business Machines Corporation, */
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/* Sony Computer Entertainment Incorporated, */
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/* Toshiba Corporation. */
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/* */
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/* All Rights Reserved. */
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/* -------------------------------------------------------------- */
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/* PROLOG END TAG zYx */
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#ifndef _ILOG2_H_
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#define _ILOG2_H_ 1
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/*
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* FUNCTION
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* signed int _ilog2(signed int x)
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*
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* DESCRIPTION
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* _ilog2 computes ceiling of log (base 2) of the input value x.
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* The input value, x, must be a non-zero positive value.
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*/
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static __inline signed int _ilog2(signed int x)
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{
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#ifdef __SPU__
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return (32 - spu_extract(spu_cntlz(spu_promote(x - 1, 0)), 0));
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#else
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signed int result;
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for (result=0, x--; x > 0; result++, x>>=1);
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return (result);
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#endif
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}
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#endif /* _ILOG2_H_ */
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