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taiyang-li 2024-01-31 11:48:02 +08:00
parent 49fc8a7099
commit 818fb9802a
1 changed files with 12 additions and 4 deletions
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16
src/Functions/if.cpp
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@ -25,8 +25,6 @@
#include <Functions/FunctionFactory.h>
#include <type_traits>
#pragma clang diagnostic ignored "-Wundefined-reinterpret-cast"
namespace DB
{
namespace ErrorCodes
@ -59,7 +57,11 @@ concept is_native_int_or_decimal_v
auto mask = static_cast<UIntType>(static_cast<IntType>(vc) - 1); \
auto new_a = static_cast<ResultType>(va); \
auto new_b = static_cast<ResultType>(vb); \
auto tmp = (~mask & (*reinterpret_cast<UIntType *>(&new_a))) | (mask & (*reinterpret_cast<UIntType *>(&new_b))); \
UIntType uint_a; \
std::memcpy(&uint_a, &new_a, sizeof(UIntType)); \
UIntType uint_b; \
std::memcpy(&uint_b, &new_b, sizeof(UIntType)); \
UIntType tmp = (~mask & uint_a) | (mask & uint_b); \
(vr) = *(reinterpret_cast<ResultType *>(&tmp));
template <typename ArrayCond, typename ArrayA, typename ArrayB, typename ArrayResult, typename ResultType>
@ -220,12 +222,18 @@ template <typename ArrayCond, typename A, typename B, typename ArrayResult, type
inline void fillConstantConstant(const ArrayCond & cond, A a, B b, ArrayResult & res)
{
size_t size = cond.size();
/// Int8(alias type of uint8_t) has special aliasing properties that prevents compiler from auto-vectorizing for below codes, refer to https://gist.github.com/alexei-zaripov/dcc14c78819c5f1354afe8b70932007c
///
/// for (size_t i = 0; i < size; ++i)
/// res[i] = cond[i] ? static_cast<Int8>(a) : static_cast<Int8>(b);
///
/// Therefore, we manually optimize it by avoiding branch miss when ResultType is Int8. Other types like (U)Int128|256 or Decimal128/256 also benefit from this optimization.
if constexpr (std::is_same_v<ResultType, Int8> || is_over_big_int<ResultType>)
{
alignas(64) const ResultType ab[2] = {static_cast<ResultType>(a), static_cast<ResultType>(b)};
for (size_t i = 0; i < size; ++i)
{
/// Introduce memory access to avoid branch miss
res[i] = ab[!cond[i]];
}
}