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bit_util: std::bitset-based BitCount implementation

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Suggestion by @lioncash.
This commit is contained in:
MerryMage 2016-09-02 21:57:50 +01:00
parent 5aa4f753b6
commit cc3e7e71aa
1 changed files with 4 additions and 6 deletions
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10
src/common/bit_util.h
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@ -6,6 +6,7 @@
#pragma once
#include <bitset>
#include <climits>
#include "common/assert.h"
@ -71,12 +72,9 @@ inline T SignExtend(const T value) {
return value;
}
inline size_t BitCount(u32 value) {
// Portable SWAR algorithm for population count
value = value - ((value >> 1) & 0x55555555); // Two-bit count
value = (value & 0x33333333) + ((value >> 2) & 0x33333333); // Nybble count
value = (value + (value >> 4)) & 0x0F0F0F0F; // Byte count
return ((value * 0x01010101) >> 24) & 0xFF; // Summate the byte counts
template <typename Integral>
inline size_t BitCount(Integral value) {
return std::bitset<BitSize<Integral>()>(value).count();
}
} // namespace Common