| /* |
| * 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. |
| * |
| * Authors: Steve Reinhardt |
| * Nathan Binkert |
| * Giacomo Travaglini |
| */ |
| |
| #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. |
| */ |
| 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); |
| } |
| |
| /** |
| * Extract the bit from this position from 'val' and right justify it. |
| */ |
| 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 |
| */ |
| 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 |
| 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 |
| */ |
| template <class T, class B> |
| inline |
| T |
| insertBits(T val, int first, int last, B bit_val) |
| { |
| T t_bit_val = bit_val; |
| T bmask = mask(first - last + 1) << last; |
| return ((t_bit_val << last) & bmask) | (val & ~bmask); |
| } |
| |
| /** |
| * Overloaded for access to only one bit in value |
| */ |
| 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. |
| */ |
| 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*/ |
| 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 |
| */ |
| 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 |
| */ |
| 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 |
| */ |
| 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. |
| */ |
| 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 |
| */ |
| 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 |
| */ |
| 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. |
| */ |
| 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. |
| */ |
| inline int ctz64(uint64_t value) |
| { |
| return value ? __builtin_ctzll(value) : 64; |
| } |
| |
| #endif // __BASE_BITFIELD_HH__ |