void zero_float_fill(float* buffer) { std::fill(buffer, buffer + N, 0.0f); } This simple function is properly optimized into a memset by clang and gcc, but the latest MSVC with /O2 produces this inefficient code. Godbolt link:https://godbolt.org/z/hadjdh4PG ...
long转string java_java中Long类型转换为String类型的两种方法及区别
C++ vector 避免 fill 0 我们在profiler的时候有的时候发现memset占用热点比较高。而且是std::vector::resize 带来的。这个明显是没必要的, 例如: std::vector<int> result;// 这里resize会 fill 0result.resize(input_rows);for(inti =0;i < input_rows; ++i) { result[i] =transfer(input[i]); } ...
gcc has some x86 tuning options for string ops (like -mstringop-strategy=alg and -mmemset-strategy=strategy), but IDK if any of them will get it to actually emit rep movsd for fill(1). Probably not, since I assume the code starts out as a loop, rather than a memset. With more th...
我是在分析vector构造函数构造默认值是分析到了fill_n,为什么不在vector中或者fill_n中处理一些int、long等数字为0时的默认构造过程,可以通过memset优化性能吗?为什么? 有想法欢迎交流。 fill template<typename_ForwardIterator,typename_Tp>inlinetypename__gnu_cxx::__enable_if<!__is_scalar<_Tp>::__value,voi...
> // Specialization: for char types we can use memset. > template<typename _Tp> > @@ -1079,28 +1090,36 @@ _GLIBCXX_END_NAMESPACE_CONTAINER > __size_to_integer(__float128 __n) { return (long long)__n; } > #endif >
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std::uninitialized_fill_n algorithms to directly perform memcpy/memset optimizations instead of dispatching to std::copy/std::fill/std::fill_n. The reasons for this are: - Use 'if constexpr' to simplify and optimize compilation throughput, so ...
一些展开可能会让TLB在商店发生之前就开始更远的解析，因为存储地址uop的吞吐量比存储数据的吞吐量要高。
Tested x86_64-linux. -- >8 -- As noted in the PR, the optimization used for scalar types in std::fill and std::fill_n is non-conforming, because it doesn't consider that assigning a scalar type might have non-trivial side effects which are affected by the optimization. By changing ...