intel-graphics-compiler/visa/BitSet.cpp

/*========================== begin_copyright_notice ============================

Copyright (C) 2017-2021 Intel Corporation

SPDX-License-Identifier: MIT

============================= end_copyright_notice ===========================*/

#include "Assertions.h"
#include "BitSet.h"

void BitSet::create(unsigned size) {
  const unsigned newArraySize =
      (size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  const unsigned oldArraySize =
      (m_Size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  const unsigned numBitsLeft = size % NUM_BITS_PER_ELT;

  if (size == 0) {
    free(m_BitSetArray);
    m_BitSetArray = nullptr;
    m_Size = 0;
    return;
  }

  if (newArraySize == oldArraySize) {
    // same array size, zero out the unused bits if necessary
    m_Size = size;
    if (newArraySize && numBitsLeft != 0) {
      m_BitSetArray[newArraySize - 1] &= _BIT(numBitsLeft) - 1;
    }
  } else {
    BITSET_ARRAY_TYPE *ptr =
        (BITSET_ARRAY_TYPE *)malloc(newArraySize * sizeof(BITSET_ARRAY_TYPE));

    if (ptr) {
      if (m_BitSetArray) {
        if (newArraySize > oldArraySize) {
          // copy entire old array over, set uninitialized bits to zero
          memcpy_s(ptr, newArraySize * sizeof(BITSET_ARRAY_TYPE), m_BitSetArray,
                   oldArraySize * sizeof(BITSET_ARRAY_TYPE));
          memset(ptr + oldArraySize, 0,
                 (newArraySize - oldArraySize) * sizeof(BITSET_ARRAY_TYPE));
        } else {
          // copy old array up to the size of new array, zero out the unused
          // bits
          memcpy_s(ptr, newArraySize * sizeof(BITSET_ARRAY_TYPE), m_BitSetArray,
                   newArraySize * sizeof(BITSET_ARRAY_TYPE));
          if (numBitsLeft != 0) {
            ptr[newArraySize - 1] &= _BIT(numBitsLeft) - 1;
          }
        }
      } else {
        memset(ptr, 0, newArraySize * sizeof(BITSET_ARRAY_TYPE));
      }

      free(m_BitSetArray);

      m_BitSetArray = ptr;
      m_Size = size;
    } else {
      vASSERT(false);
    }
  }
}

void BitSet::setAll(void) {
  if (m_BitSetArray) {
    unsigned index = m_Size / NUM_BITS_PER_ELT;
    std::fill_n(m_BitSetArray, index, ~(BITSET_ARRAY_TYPE)0);

    // do the leftover bits, make sure we don't change the values of the unused
    // bits, so isEmpty() can be implemented faster
    int numBitsLeft = m_Size % NUM_BITS_PER_ELT;
    if (numBitsLeft) {
      m_BitSetArray[index] = _BIT(numBitsLeft) - 1;
    }
  }
}

void BitSet::invert(void) {
  if (m_BitSetArray) {
    unsigned index;
    for (index = 0; index < m_Size / NUM_BITS_PER_ELT; index++) {
      m_BitSetArray[index] = ~m_BitSetArray[index];
    }

    // do the leftover bits
    int numBitsLeft = m_Size % NUM_BITS_PER_ELT;
    if (numBitsLeft) {
      m_BitSetArray[index] = ~m_BitSetArray[index] & (_BIT(numBitsLeft) - 1);
    }
  }
}

template <typename T>
void vector_and(T *__restrict p1, const T *const p2, unsigned n) {
  for (unsigned i = 0; i < n; ++i) {
    p1[i] &= p2[i];
  }
}

template <typename T>
void vector_or(T *__restrict p1, const T *const p2, unsigned n) {
  for (unsigned i = 0; i < n; ++i) {
    p1[i] |= p2[i];
  }
}

template <typename T>
void vector_minus(T *__restrict p1, const T *const p2, unsigned n) {
  for (unsigned i = 0; i < n; ++i) {
    p1[i] &= ~p2[i];
  }
}

BitSet &BitSet::operator|=(const BitSet &other) {
  unsigned size = other.m_Size;

  // grow the set to the size of the other set if necessary
  if (m_Size < other.m_Size) {
    create(other.m_Size);
    size = m_Size;
  }

  unsigned arraySize = (size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  vector_or(m_BitSetArray, other.m_BitSetArray, arraySize);

  return *this;
}

BitSet &BitSet::operator-=(const BitSet &other) {
  // do not grow the set for subtract
  unsigned size = m_Size < other.m_Size ? m_Size : other.m_Size;
  unsigned arraySize = (size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  vector_minus(m_BitSetArray, other.m_BitSetArray, arraySize);
  return *this;
}

BitSet &BitSet::operator&=(const BitSet &other) {
  // do not grow the set for and
  unsigned size = m_Size < other.m_Size ? m_Size : other.m_Size;
  unsigned arraySize = (size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  vector_and(m_BitSetArray, other.m_BitSetArray, arraySize);

  // zero out the leftover bits if there are any
  unsigned myArraySize = (m_Size + NUM_BITS_PER_ELT - 1) / NUM_BITS_PER_ELT;
  for (unsigned i = arraySize; i < myArraySize; i++) {
    m_BitSetArray[i] = 0;
  }

  return *this;
}

// Create a bitmask with the N right-most bits set to 1, and all other bits set
// to 0.
static BITSET_ARRAY_TYPE maskTrailingOnes(unsigned n) {
  vASSERT(n <= NUM_BITS_PER_ELT);
  return n == 0 ? 0 : (BITSET_ARRAY_TYPE(-1) >> (NUM_BITS_PER_ELT - n));
}

// Create a bitmask with the N right-most bits set to 0, and all other bits set
// to 1.
static BITSET_ARRAY_TYPE maskTrailingZeros(unsigned n) {
  return ~maskTrailingOnes(n);
}

// TODO: Use c++20 bit manipulation utility functions.
static unsigned countTrailingZeros(BITSET_ARRAY_TYPE val) {
  vASSERT(val != 0);
  unsigned count = 0;
  while ((val & 1) == 0) {
    val >>= 1;
    ++count;
  }
  return count;
}

static unsigned countLeadingZeros(BITSET_ARRAY_TYPE val) {
  vASSERT(val != 0);
  unsigned count = 0;
  while ((val & (1 << (NUM_BITS_PER_ELT - 1))) == 0) {
    val <<= 1;
    ++count;
  }
  return count;
}

int BitSet::findFirstIn(unsigned begin, unsigned end) const {
  vASSERT(begin <= end && end <= m_Size);
  if (begin == end)
    return -1;

  unsigned firstElt = begin / NUM_BITS_PER_ELT;
  unsigned lastElt = (end - 1) / NUM_BITS_PER_ELT;

  for (unsigned i = firstElt; i <= lastElt; ++i) {
    auto elt = getElt(i);

    if (i == firstElt) {
      unsigned firstBit = begin % NUM_BITS_PER_ELT;
      elt &= maskTrailingZeros(firstBit);
    }

    if (i == lastElt) {
      unsigned lastBit = (end - 1) % NUM_BITS_PER_ELT;
      elt &= maskTrailingOnes(lastBit + 1);
    }

    if (elt != 0)
      return i * NUM_BITS_PER_ELT + countTrailingZeros(elt);
  }

  return -1;
}

int BitSet::findLastIn(unsigned begin, unsigned end) const {
  vASSERT(begin <= end && end <= m_Size);
  if (begin == end)
    return -1;

  unsigned lastElt = (end - 1) / NUM_BITS_PER_ELT;
  unsigned firstElt = begin / NUM_BITS_PER_ELT;

  for (unsigned i = lastElt + 1; i >= firstElt + 1; --i) {
    unsigned currentElt = i - 1;
    auto elt = getElt(currentElt);

    if (currentElt == lastElt) {
      unsigned lastBit = (end - 1) % NUM_BITS_PER_ELT;
      elt &= maskTrailingOnes(lastBit + 1);
    }

    if (currentElt == firstElt) {
      unsigned firstBit = begin % NUM_BITS_PER_ELT;
      elt &= maskTrailingZeros(firstBit);
    }

    if (elt != 0)
      return (currentElt + 1) * NUM_BITS_PER_ELT - countLeadingZeros(elt) - 1;
  }

  return -1;
}