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Implement 128 bits Unsigned Integer Multiplication and Division.

This commit is contained in:
Fernando Sahmkow 2019-02-15 19:26:41 -04:00 committed by FernandoS27
parent 5b7ec71fb7
commit 3ea48e8ebe
3 changed files with 50 additions and 0 deletions

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@ -113,6 +113,8 @@ add_library(common STATIC
threadsafe_queue.h
timer.cpp
timer.h
uint128.cpp
uint128.h
vector_math.h
web_result.h
)

18
src/common/uint128.cpp Normal file
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@ -0,0 +1,18 @@
namespace Common {
std::pair<u64, u64> udiv128(u128 dividend, u64 divisor) {
u64 remainder = dividend[0] % divisor;
u64 accum = dividend[0] / divisor;
if (dividend[1] == 0)
return {accum, remainder};
// We ignore dividend[1] / divisor as that overflows
u64 first_segment = (dividend[1] % divisor) << 32;
accum += (first_segment / divisor) << 32;
u64 second_segment = (first_segment % divisor) << 32;
accum += (second_segment / divisor);
remainder += second_segment % divisor;
return {accum, remainder};
}
} // namespace Common

30
src/common/uint128.h Normal file
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@ -0,0 +1,30 @@
#include <array>
#include <cstdint>
#include <utility>
#include <cstring>
#include "common/common_types.h"
namespace Common {
#ifdef _MSC_VER
#include <intrin.h>
#pragma intrinsic(_umul128)
#endif
inline u128 umul128(u64 a, u64 b) {
#ifdef _MSC_VER
u128 result;
result[0] = _umul128(a, b, &result[1]);
#else
unsigned __int128 tmp = a;
tmp *= b;
u128 result;
std::memcpy(&result, &tmp, sizeof(u128));
#endif
return result;
}
std::pair<u64, u64> udiv128(u128 dividend, u64 divisor);
} // namespace Common