MSVC编译器甚至不优化使用/ Ox / EHsc的noexcept调用 [英] MSVC compiler does not optimize even noexcept calls with /Ox /EHsc

问题描述

这是一个例子。

#include <cstdlib>

template <typename TInteger>
class range_iterated_helper final
{
public:
    constexpr range_iterated_helper(TInteger from, TInteger to) noexcept
        : m_from(from), m_to(to)
    {
    }

    struct const_iterator final
    {
        const_iterator& operator ++ () noexcept
        {
            ++index;
            return *this;
        }

        const TInteger operator * () noexcept
        {
            return index;
        }

        bool operator == (const_iterator const& other) const noexcept
        {
            return index == other.index;
        }

        bool operator != (const_iterator const& other) const noexcept
        {
            return index != other.index;
        }

        TInteger index;
    };

    constexpr const_iterator begin() const noexcept
    {
        return { m_from };
    }

    constexpr const_iterator end() const noexcept
    {
        return { m_to };
    }

    constexpr const_iterator cbegin() const noexcept
    {
        return { m_from };
    }

    constexpr const_iterator cend() const noexcept
    {
        return { m_to };
    }

private:
    TInteger m_from;
    TInteger m_to;
};

template <typename TInteger>
constexpr range_iterated_helper<TInteger> make_integer_range(TInteger from, TInteger to) noexcept
{
    return { from, to };
}

template <typename TInteger>
constexpr range_iterated_helper<TInteger> make_integer_range_to(TInteger to) noexcept
{
    return { 0, to };
}

constexpr range_iterated_helper<size_t> make_indices(size_t size) noexcept
{
    return { 0, size };
}


size_t f1(size_t n)
{
    size_t result = 0;
    for (auto x : make_indices(n))
        result *= x;
    return result;
}

size_t f2(size_t n)
{
    size_t result = 0;
    for (size_t x = 0; x < n; ++x)
        result *= x;
    return result;
}

https://godbolt.org/g/HUqhpq

https://godbolt.org/g/HUqhpq

我们有一些帮助代码，允许基于范围的语法为[0; n）迭代。使用/ EHsc编译
f1 时，调用（ noexcept ）函数 begin 和 end  保持不变。
是否有解决此问题的方法？

We have some helper code that allows ranged-based for syntax for [0; n) iteration. When f1 is compiled with /EHsc the calls to (noexcept) functions begin and end are kept without any optimizations. Are there any workarounds to this problem?

推荐答案

这看起来像VS聚合初始化的错误。以下添加修复了问题

This looks like a bug of VS aggregate initialization. The following addition fixes the problem

        const_iterator(TInteger index_)
            : index(index_)
        {
            
        }

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