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/*
* Copyright (c) 2003-2005 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Steve Reinhardt
* Nathan Binkert
*/
#ifndef __BASE_BITFIELD_HH__
#define __BASE_BITFIELD_HH__
#include <inttypes.h>
/**
* Generate a 64-bit mask of 'nbits' 1s, right justified.
*/
inline uint64_t
mask(int nbits)
{
return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
}
/**
* Extract the bitfield from position 'first' to 'last' (inclusive)
* from 'val' and right justify it. MSB is numbered 63, LSB is 0.
*/
template <class T>
inline
T
bits(T val, int first, int last)
{
int nbits = first - last + 1;
return (val >> last) & mask(nbits);
}
/**
* Mask off the given bits in place like bits() but without shifting.
* msb = 63, lsb = 0
*/
template <class T>
inline
T
mbits(T val, int first, int last)
{
return val & (mask(first+1) & ~mask(last));
}
inline uint64_t
mask(int first, int last)
{
return mbits((uint64_t)-1LL, first, last);
}
/**
* Sign-extend an N-bit value to 64 bits.
*/
template <int N>
inline
int64_t
sext(uint64_t val)
{
int sign_bit = bits(val, N-1, N-1);
return sign_bit ? (val | ~mask(N)) : val;
}
/**
* Return val with bits first to last set to bit_val
*/
template <class T, class B>
inline
T
insertBits(T val, int first, int last, B bit_val)
{
T bmask = mask(first - last + 1) << last;
return ((bit_val << last) & bmask) | (val & ~bmask);
}
/**
* A convenience function to replace bits first to last of val with bit_val
* in place.
*/
template <class T, class B>
inline
void
replaceBits(T& val, int first, int last, B bit_val)
{
val = insertBits(val, first, last, bit_val);
}
/**
* Returns the bit position of the MSB that is set in the input
*/
inline
int
findMsbSet(uint64_t val) {
int msb = 0;
if (!val)
return 0;
if (bits(val, 63,32)) { msb += 32; val >>= 32; }
if (bits(val, 31,16)) { msb += 16; val >>= 16; }
if (bits(val, 15,8)) { msb += 8; val >>= 8; }
if (bits(val, 7,4)) { msb += 4; val >>= 4; }
if (bits(val, 3,2)) { msb += 2; val >>= 2; }
if (bits(val, 1,1)) { msb += 1; }
return msb;
}
#endif // __BASE_BITFIELD_HH__
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