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Improve product of 64 bits unsigned integers on x64

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Laurent GIORELLO 2023-11-10 02:36:47 +00:00
parent 6b0082e6c7
commit 00412e6bf8
1 changed files with 7 additions and 1 deletions
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include/fmt/format.h
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@ -1486,7 +1486,13 @@ template <typename WChar, typename Buffer = memory_buffer> class to_utf8 {
// Computes 128-bit result of multiplication of two 64-bit unsigned integers. // Computes 128-bit result of multiplication of two 64-bit unsigned integers.
inline uint128_fallback umul128(uint64_t x, uint64_t y) noexcept { inline uint128_fallback umul128(uint64_t x, uint64_t y) noexcept {
#if FMT_USE_INT128 #if __x86_64__
uint64_t hi, lo;
__asm__( "mulq %[y] \n"
: "=a"(lo), "=d"(hi)
: [y] "r"(y), "a"(x), "d"(0));
return {hi, lo};
#elif FMT_USE_INT128
auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y); auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)}; return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)};
#elif defined(_MSC_VER) && defined(_M_X64) #elif defined(_MSC_VER) && defined(_M_X64)