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GH-48591: [C++] Use C++20 standard functions in bit_util.h #48611

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GH-48591: [C++] Use C++20 standard functions in bit_util.h #48611

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103 changes: 7 additions & 96 deletions cpp/src/arrow/util/bit_util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,20 +17,7 @@

#pragma once

#if defined(_MSC_VER)
# if defined(_M_AMD64) || defined(_M_X64)
# include <intrin.h> // IWYU pragma: keep
# endif

# pragma intrinsic(_BitScanReverse)
# pragma intrinsic(_BitScanForward)
# define ARROW_POPCOUNT64 __popcnt64
# define ARROW_POPCOUNT32 __popcnt
#else
# define ARROW_POPCOUNT64 __builtin_popcountll
# define ARROW_POPCOUNT32 __builtin_popcount
#endif

#include <bit>
#include <cstdint>
#include <type_traits>

Expand Down Expand Up @@ -66,8 +53,8 @@ static constexpr uint8_t kBytePopcount[] = {
5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6,
4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};

static inline uint64_t PopCount(uint64_t bitmap) { return ARROW_POPCOUNT64(bitmap); }
static inline uint32_t PopCount(uint32_t bitmap) { return ARROW_POPCOUNT32(bitmap); }
static inline uint64_t PopCount(uint64_t bitmap) { return static_cast<uint64_t>(std::popcount(bitmap)); }
static inline uint32_t PopCount(uint32_t bitmap) { return static_cast<uint32_t>(std::popcount(bitmap)); }

//
// Bit-related computations on integer values
Expand Down Expand Up @@ -181,95 +168,19 @@ static inline uint64_t TrailingBits(uint64_t v, int num_bits) {

/// \brief Count the number of leading zeros in an unsigned integer.
static inline int CountLeadingZeros(uint32_t value) {
#if defined(__clang__) || defined(__GNUC__)
if (value == 0) return 32;
return static_cast<int>(__builtin_clz(value));
#elif defined(_MSC_VER)
unsigned long index; // NOLINT
if (_BitScanReverse(&index, static_cast<unsigned long>(value))) { // NOLINT
return 31 - static_cast<int>(index);
} else {
return 32;
}
#else
int bitpos = 0;
while (value != 0) {
value >>= 1;
++bitpos;
}
return 32 - bitpos;
#endif
return std::countl_zero(value);
}

static inline int CountLeadingZeros(uint64_t value) {
#if defined(__clang__) || defined(__GNUC__)
if (value == 0) return 64;
return static_cast<int>(__builtin_clzll(value));
#elif defined(_MSC_VER)
unsigned long index; // NOLINT
if (_BitScanReverse64(&index, value)) { // NOLINT
return 63 - static_cast<int>(index);
} else {
return 64;
}
#else
int bitpos = 0;
while (value != 0) {
value >>= 1;
++bitpos;
}
return 64 - bitpos;
#endif
return std::countl_zero(value);
}

static inline int CountTrailingZeros(uint32_t value) {
#if defined(__clang__) || defined(__GNUC__)
if (value == 0) return 32;
return static_cast<int>(__builtin_ctzl(value));
#elif defined(_MSC_VER)
unsigned long index; // NOLINT
if (_BitScanForward(&index, value)) {
return static_cast<int>(index);
} else {
return 32;
}
#else
int bitpos = 0;
if (value) {
while (value & 1 == 0) {
value >>= 1;
++bitpos;
}
} else {
bitpos = 32;
}
return bitpos;
#endif
return std::countr_zero(value);
}

static inline int CountTrailingZeros(uint64_t value) {
#if defined(__clang__) || defined(__GNUC__)
if (value == 0) return 64;
return static_cast<int>(__builtin_ctzll(value));
#elif defined(_MSC_VER)
unsigned long index; // NOLINT
if (_BitScanForward64(&index, value)) {
return static_cast<int>(index);
} else {
return 64;
}
#else
int bitpos = 0;
if (value) {
while (value & 1 == 0) {
value >>= 1;
++bitpos;
}
} else {
bitpos = 64;
}
return bitpos;
#endif
return std::countr_zero(value);
}

// Returns the minimum number of bits needed to represent an unsigned value
Expand Down