/*
+ * 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.
*
* 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>
+#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.
+ * 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;
+ 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
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
/**
* Mask off the given bits in place like bits() but without shifting.
* msb = 63, lsb = 0
+ *
+ * @ingroup api_bitfield
*/
template <class T>
inline
return val & (mask(first+1) & ~mask(last));
}
+/**
+ * @ingroup api_bitfield
+ */
inline uint64_t
mask(int first, int last)
{
/**
* Sign-extend an N-bit value to 64 bits.
+ *
+ * @ingroup api_bitfield
*/
template <int N>
inline
-int64_t
+uint64_t
sext(uint64_t val)
{
int sign_bit = bits(val, N-1, N-1);
}
/**
- * Return val with bits first to last set to bit_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
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
/**
* A convenience function to replace bits first to last of val with bit_val
- * in place.
+ * 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
val = insertBits(val, first, last, bit_val);
}
-/** Overloaded function to allow to access only 1 bit*/
+/**
+ * Overloaded function to allow to access only 1 bit
+ *
+ * @ingroup api_bitfield
+ */
template <class T, class B>
inline
void
{
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
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__
projects / gem5.git / blobdiff