C++: Why pass-by-value is generally more efficient than pass-by-reference for built-in (i.e., C-like...

转载于 2013-07-02 15:19:00 发布 · 76 阅读

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原文链接：http://www.cnblogs.com/DebugMe/p/3167045.html

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#c/c++

本文探讨了编译器供应商如何实现引用作为指针的方式，并讨论了在传递内置类型时使用指针与引用之间的区别。此外，文章还分析了在某些情况下，编译器可能忽略const引用。

A compiler vendor would typically implement a reference as a pointer. Pointers tend to be the same size as or larger than many of the built-in types. For these built-in types the same amount of data would be passed whether you passed by value or by reference. In the function, in order to get the actual data, you would however need to dereference this internal pointer. This can add an instruction to the generated code, and you will also have two memory locations that may not be in cache. The difference won't be much - but it could be measured in tight loops.

A compiler vendor could choose to disregard const references (and sometimes also non-const references) when they're used on built-in types - all depending on the information available to the compiler when it deals with the function and its callers.

转载于:https://www.cnblogs.com/DebugMe/p/3167045.html