1/*
2 * Copyright (c) 2017, 2019 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Steve Reinhardt
41 *          Nathan Binkert
42 *          Giacomo Travaglini
43 */
44
45#ifndef __BASE_BITFIELD_HH__
46#define __BASE_BITFIELD_HH__
47
48#include <inttypes.h>
49#include <cassert>
50#include <cstddef>
51#include <type_traits>
52
53/** Lookup table used for High Speed bit reversing */
54extern const uint8_t reverseLookUpTable[];
55
56/**
57 * Generate a 64-bit mask of 'nbits' 1s, right justified.
58 */
59inline uint64_t
60mask(int nbits)
61{
62    return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
63}
64
65/**
66 * Extract the bitfield from position 'first' to 'last' (inclusive)
67 * from 'val' and right justify it.  MSB is numbered 63, LSB is 0.
68 */
69template <class T>
70inline
71T
72bits(T val, int first, int last)
73{
74    int nbits = first - last + 1;
75    return (val >> last) & mask(nbits);
76}
77
78/**
79 * Extract the bit from this position from 'val' and right justify it.
80 */
81template <class T>
82inline
83T
84bits(T val, int bit)
85{
86    return bits(val, bit, bit);
87}
88
89/**
90 * Mask off the given bits in place like bits() but without shifting.
91 * msb = 63, lsb = 0
92 */
93template <class T>
94inline
95T
96mbits(T val, int first, int last)
97{
98    return val & (mask(first+1) & ~mask(last));
99}
100
101inline uint64_t
102mask(int first, int last)
103{
104    return mbits((uint64_t)-1LL, first, last);
105}
106
107/**
108 * Sign-extend an N-bit value to 64 bits.
109 */
110template <int N>
111inline
112uint64_t
113sext(uint64_t val)
114{
115    int sign_bit = bits(val, N-1, N-1);
116    return sign_bit ? (val | ~mask(N)) : val;
117}
118
119/**
120 * Return val with bits first to last set to bit_val
121 */
122template <class T, class B>
123inline
124T
125insertBits(T val, int first, int last, B bit_val)
126{
127    T t_bit_val = bit_val;
128    T bmask = mask(first - last + 1) << last;
129    return ((t_bit_val << last) & bmask) | (val & ~bmask);
130}
131
132/**
133 * Overloaded for access to only one bit in value
134 */
135template <class T, class B>
136inline
137T
138insertBits(T val, int bit, B bit_val)
139{
140    return insertBits(val, bit, bit, bit_val);
141}
142
143/**
144 * A convenience function to replace bits first to last of val with bit_val
145 * in place.
146 */
147template <class T, class B>
148inline
149void
150replaceBits(T& val, int first, int last, B bit_val)
151{
152    val = insertBits(val, first, last, bit_val);
153}
154
155/** Overloaded function to allow to access only 1 bit*/
156template <class T, class B>
157inline
158void
159replaceBits(T& val, int bit, B bit_val)
160{
161    val = insertBits(val, bit, bit, bit_val);
162}
163
164/**
165 * Takes a variable lenght word and returns the mirrored version
166 * (Bit by bit, LSB=>MSB).
167 *
168 * algorithm from
169 * http://graphics.stanford.edu/~seander/bithacks.html
170 * #ReverseBitsByLookupTable
171 *
172 * @param val: variable lenght word
173 * @param size: number of bytes to mirror
174 * @return mirrored word
175 */
176template <class T>
177T
178reverseBits(T val, std::size_t size = sizeof(T))
179{
180    static_assert(std::is_integral<T>::value, "Expecting an integer type");
181
182    assert(size <= sizeof(T));
183
184    T output = 0;
185    for (auto byte = 0; byte < size; byte++, val = static_cast<T>(val >> 8)) {
186        output = (output << 8) | reverseLookUpTable[val & 0xFF];
187    }
188
189    return output;
190}
191
192/**
193 * Returns the bit position of the MSB that is set in the input
194 */
195inline
196int
197findMsbSet(uint64_t val) {
198    int msb = 0;
199    if (!val)
200        return 0;
201    if (bits(val, 63,32)) { msb += 32; val >>= 32; }
202    if (bits(val, 31,16)) { msb += 16; val >>= 16; }
203    if (bits(val, 15,8))  { msb += 8;  val >>= 8;  }
204    if (bits(val, 7,4))   { msb += 4;  val >>= 4;  }
205    if (bits(val, 3,2))   { msb += 2;  val >>= 2;  }
206    if (bits(val, 1,1))   { msb += 1; }
207    return msb;
208}
209
210/**
211 * Returns the bit position of the LSB that is set in the input
212 */
213inline int
214findLsbSet(uint64_t val) {
215    int lsb = 0;
216    if (!val)
217        return sizeof(val) * 8;
218    if (!bits(val, 31,0)) { lsb += 32; val >>= 32; }
219    if (!bits(val, 15,0)) { lsb += 16; val >>= 16; }
220    if (!bits(val, 7,0))  { lsb += 8;  val >>= 8;  }
221    if (!bits(val, 3,0))  { lsb += 4;  val >>= 4;  }
222    if (!bits(val, 1,0))  { lsb += 2;  val >>= 2;  }
223    if (!bits(val, 0,0))  { lsb += 1; }
224    return lsb;
225}
226
227/**
228 * Checks if a number is a power of two, or zero.
229 */
230template <class T>
231inline bool
232isPow2(T v) {
233   return (v & (v - 1)) == (T)0;
234}
235
236/**
237 * Returns the number of set ones in the provided value.
238 * PD algorithm from
239 * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
240 */
241inline int
242popCount(uint64_t val) {
243#ifndef __has_builtin
244    #define __has_builtin(foo) 0
245#endif
246#if defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
247    return __builtin_popcountl(val);
248#else
249    const uint64_t m1 = 0x5555555555555555;  // ..010101b
250    const uint64_t m2 = 0x3333333333333333;  // ..110011b
251    const uint64_t m4 = 0x0f0f0f0f0f0f0f0f;  // ..001111b
252    const uint64_t sum = 0x0101010101010101;
253
254    val -= (val >> 1) & m1;               // 2 bits count -> 2 bits
255    val = (val & m2) + ((val >> 2) & m2); // 4 bits count -> 4 bits
256    val = (val + (val >> 4)) & m4;        // 8 bits count -> 8 bits
257    return (val * sum) >> 56;             // horizontal sum
258#endif // defined(__GNUC__) || (defined(__clang__) && __has_builtin(__builtin_popcountl))
259}
260
261/**
262 * Align to the next highest power of two.
263 *
264 * The number passed in is aligned to the next highest power of two,
265 * if it is not already a power of two. Please note that if 0 is
266 * passed in, 0 is returned.
267 *
268 * This code has been modified from the following:
269 * http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
270 */
271inline uint64_t alignToPowerOfTwo(uint64_t val)
272{
273    val--;
274    val |= val >> 1;
275    val |= val >> 2;
276    val |= val >> 4;
277    val |= val >> 8;
278    val |= val >> 16;
279    val |= val >> 32;
280    val++;
281
282    return val;
283};
284
285/**
286 * Count trailing zeros in a 32-bit value.
287 *
288 * @param An input value
289 * @return The number of trailing zeros or 32 if the value is zero.
290 */
291inline int ctz32(uint32_t value)
292{
293    return value ? __builtin_ctzl(value) : 32;
294}
295
296/**
297 * Count trailing zeros in a 64-bit value.
298 *
299 * @param An input value
300 * @return The number of trailing zeros or 64 if the value is zero.
301 */
302inline int ctz64(uint64_t value)
303{
304    return value ? __builtin_ctzll(value) : 64;
305}
306
307#endif // __BASE_BITFIELD_HH__
308