Merge pull request #5781 from lioncash/bits
bit_util: Unify implementations of MostSignificantBit32/MostSignificantBit64
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2c4c7aea8a
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@ -7,10 +7,6 @@
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#include <climits>
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#include <cstddef>
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#ifdef _MSC_VER
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#include <intrin.h>
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#endif
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#include "common/common_types.h"
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namespace Common {
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@ -21,48 +17,30 @@ template <typename T>
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return sizeof(T) * CHAR_BIT;
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}
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#ifdef _MSC_VER
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[[nodiscard]] inline u32 MostSignificantBit32(const u32 value) {
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unsigned long result;
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_BitScanReverse(&result, value);
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return static_cast<u32>(result);
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[[nodiscard]] constexpr u32 MostSignificantBit32(const u32 value) {
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return 31U - static_cast<u32>(std::countl_zero(value));
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}
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[[nodiscard]] inline u32 MostSignificantBit64(const u64 value) {
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unsigned long result;
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_BitScanReverse64(&result, value);
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return static_cast<u32>(result);
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[[nodiscard]] constexpr u32 MostSignificantBit64(const u64 value) {
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return 63U - static_cast<u32>(std::countl_zero(value));
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}
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#else
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[[nodiscard]] inline u32 MostSignificantBit32(const u32 value) {
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return 31U - static_cast<u32>(__builtin_clz(value));
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}
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[[nodiscard]] inline u32 MostSignificantBit64(const u64 value) {
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return 63U - static_cast<u32>(__builtin_clzll(value));
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}
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#endif
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[[nodiscard]] inline u32 Log2Floor32(const u32 value) {
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[[nodiscard]] constexpr u32 Log2Floor32(const u32 value) {
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return MostSignificantBit32(value);
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}
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[[nodiscard]] inline u32 Log2Ceil32(const u32 value) {
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const u32 log2_f = Log2Floor32(value);
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return log2_f + ((value ^ (1U << log2_f)) != 0U);
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}
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[[nodiscard]] inline u32 Log2Floor64(const u64 value) {
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[[nodiscard]] constexpr u32 Log2Floor64(const u64 value) {
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return MostSignificantBit64(value);
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}
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[[nodiscard]] inline u32 Log2Ceil64(const u64 value) {
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const u64 log2_f = static_cast<u64>(Log2Floor64(value));
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return static_cast<u32>(log2_f + ((value ^ (1ULL << log2_f)) != 0ULL));
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[[nodiscard]] constexpr u32 Log2Ceil32(const u32 value) {
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const u32 log2_f = Log2Floor32(value);
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return log2_f + static_cast<u32>((value ^ (1U << log2_f)) != 0U);
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}
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[[nodiscard]] constexpr u32 Log2Ceil64(const u64 value) {
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const u64 log2_f = Log2Floor64(value);
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return static_cast<u32>(log2_f + static_cast<u64>((value ^ (1ULL << log2_f)) != 0ULL));
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}
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} // namespace Common
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