Use of MOZ_ARRAY_LENGTH for static constants?

Sun, 23 Feb 2014 16:11:06 -0800

Both ArrayLength and MOZ_ARRAY_LENGTH are typesafe when compiled as C++, however ArrayLength has the disadvantage that it's not a constant expression in MSVC. In unoptimised builds this is direly slow as the templated function does not even get inlined, but even in optimised builds the MSVC compiler is unable to completely optimise away static variables. In particular, the variable is treated as if it is forward-declared: the value is fetched from memory in each function that uses it. (In my simple test there were enough registers to avoid fetching the value more than once, but I don't know what happens if this is not the case. And at least the optimiser was able to avoid creating any static constructors.) Would it therefore be preferable to use MOZ_ARRAY_LENGTH in such cases? 

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