blob: 98a93d4fa4bbf1b427d90622e92615ee03fda8e5 [file] [log] [blame]
/*
* Copyright (c) 2017, 2019 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* 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.
*/
#ifndef __BASE_BITFIELD_HH__
#define __BASE_BITFIELD_HH__
#include <inttypes.h>
#include <cassert>
#include <cstddef>
#include <type_traits>
/** Lookup table used for High Speed bit reversing */
extern const uint8_t reverseLookUpTable[];
/**
* Generate a 64-bit mask of 'nbits' 1s, right justified. If a number of bits
* greater than 64 is given, it is truncated to 64.
*
* @param nbits The number of bits set in the mask.
*
* @ingroup api_bitfield
*/
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.
*
* @ingroup api_bitfield
*/
template <class T>
inline
T
bits(T val, int first, int last)
{
int nbits = first - last + 1;
assert((first - last) >= 0);
return (val >> last) & mask(nbits);
}
/**
* Extract the bit from this position from 'val' and right justify it.
*
* @ingroup api_bitfield
*/
template <class T>
inline
T
bits(T val, int bit)
{
return bits(val, bit, bit);
}
/**
* Mask off the given bits in place like bits() but without shifting.
* msb = 63, lsb = 0
*
* @ingroup api_bitfield
*/
template <class T>
inline
T
mbits(T val, int first, int last)
{
return val & (mask(first+1) & ~mask(last));
}
/**
* @ingroup api_bitfield
*/
inline uint64_t
mask(int first, int last)
{
return mbits((uint64_t)-1LL, first, last);
}
/**
* Sign-extend an N-bit value to 64 bits.
*
* @ingroup api_bitfield
*/
template <int N>
inline
uint64_t
sext(uint64_t val)
{
int sign_bit = bits(val, N-1, N-1);
return sign_bit ? (val | ~mask(N)) : val;
}
/**
* Returns val with bits first to last set to the LSBs of bit_val
*
* E.g.:
* first: 7
* last: 4
* val: 0xFFFF
* bit_val: 0x0000
* returned: 0xFF0F
*
* @ingroup api_bitfield
*/
template <class T, class B>
inline
T
insertBits(T val, int first, int last, B bit_val)
{
T t_bit_val = bit_val;
assert((first - last) >= 0);
T bmask = mask(first - last + 1) << last;
return ((t_bit_val << last) & bmask) | (val & ~bmask);
}
/**
* Overloaded for access to only one bit in value
*
* @ingroup api_bitfield
*/
template <class T, class B>
inline
T
insertBits(T val, int bit, B bit_val)
{
return insertBits(val, bit, bit, bit_val);
}
/**
* A convenience function to replace bits first to last of val with bit_val
* in place. It is functionally equivalent to insertBits.
*
* \note "first" is the MSB and "last" is the LSB. "first" >= "last"
*
* @ingroup api_bitfield
*/
template <class T, class B>
inline
void
replaceBits(T& val, int first, int last, B bit_val)
{
val = insertBits(val, first, last, bit_val);
}
/**
* Overloaded function to allow to access only 1 bit
*
* @ingroup api_bitfield
*/
template <class T, class B>
inline
void
replaceBits(T& val, int bit, B bit_val)
{
val = insertBits(val, bit, bit, bit_val);
}
/**
* Takes a variable lenght word and returns the mirrored version
* (Bit by bit, LSB=>MSB).
*
* algorithm from
* http://graphics.stanford.edu/~seander/bithacks.html
* #ReverseBitsByLookupTable
*
* @param val: variable lenght word
* @param size: number of bytes to mirror
* @return mirrored word
*
* @ingroup api_bitfield
*/
template <class T>
T
reverseBits(T val, std::size_t size = sizeof(T))
{
static_assert(std::is_integral<T>::value, "Expecting an integer type");
assert(size <= sizeof(T));
T output = 0;
for (auto byte = 0; byte < size; byte++, val = static_cast<T>(val >> 8)) {
output = (output << 8) | reverseLookUpTable[val & 0xFF];
}
return output;
}
/**
* Returns the bit position of the MSB that is set in the input
*
* @ingroup api_bitfield
*/
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;
}
/**
* Returns the bit position of the LSB that is set in the input
*
* @ingroup api_bitfield
*/
inline int
findLsbSet(uint64_t val) {
int lsb = 0;
if (!val)
return sizeof(val) * 8;
if (!bits(val, 31,0)) { lsb += 32; val >>= 32; }
if (!bits(val, 15,0)) { lsb += 16; val >>= 16; }
if (!bits(val, 7,0)) { lsb += 8; val >>= 8; }
if (!bits(val, 3,0)) { lsb += 4; val >>= 4; }
if (!bits(val, 1,0)) { lsb += 2; val >>= 2; }
if (!bits(val, 0,0)) { lsb += 1; }
return lsb;
}
/**
* Checks if a number is a power of two, or zero.
*
* @ingroup api_bitfield
*/
template <class T>
inline bool
isPow2(T v) {
return (v & (v - 1)) == (T)0;
}
/**
* Returns the number of set ones in the provided value.
* PD algorithm from
* http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
*
* @ingroup api_bitfield
*/
inline int
popCount(uint64_t val) {
#ifndef __has_builtin
#define __has_builtin(foo) 0
#endif
#if defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
return __builtin_popcountl(val);
#else
const uint64_t m1 = 0x5555555555555555; // ..010101b
const uint64_t m2 = 0x3333333333333333; // ..110011b
const uint64_t m4 = 0x0f0f0f0f0f0f0f0f; // ..001111b
const uint64_t sum = 0x0101010101010101;
val -= (val >> 1) & m1; // 2 bits count -> 2 bits
val = (val & m2) + ((val >> 2) & m2); // 4 bits count -> 4 bits
val = (val + (val >> 4)) & m4; // 8 bits count -> 8 bits
return (val * sum) >> 56; // horizontal sum
#endif // defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
}
/**
* Align to the next highest power of two.
*
* The number passed in is aligned to the next highest power of two,
* if it is not already a power of two. Please note that if 0 is
* passed in, 0 is returned.
*
* This code has been modified from the following:
* http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
*
* @ingroup api_bitfield
*/
inline uint64_t alignToPowerOfTwo(uint64_t val)
{
val--;
val |= val >> 1;
val |= val >> 2;
val |= val >> 4;
val |= val >> 8;
val |= val >> 16;
val |= val >> 32;
val++;
return val;
};
/**
* Count trailing zeros in a 32-bit value.
*
* @param An input value
* @return The number of trailing zeros or 32 if the value is zero.
*
* @ingroup api_bitfield
*/
inline int ctz32(uint32_t value)
{
return value ? __builtin_ctzl(value) : 32;
}
/**
* Count trailing zeros in a 64-bit value.
*
* @param An input value
* @return The number of trailing zeros or 64 if the value is zero.
*
* @ingroup api_bitfield
*/
inline int ctz64(uint64_t value)
{
return value ? __builtin_ctzll(value) : 64;
}
#endif // __BASE_BITFIELD_HH__