Use Compile-Time Constexpr If

[leimao]

This runtime if can be removed at compile-time.

[ccecka]

If size<2>(tCrA) is known at compile-time, this will already be elided by the compiler.

The only thing this does is require that it is known at compile-time, which may be attractive but is certainly overly restrictive.

[d-k-b]

@leimao, is this fixing a failure you were seeing? If so, please elaborate. If not, the recommendation would be to allow the compiler to do its thing with the code as-is which is slightly more flexible.

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