My second quote above actually cover your cases in the case of "overshift". In the case of overshift, the value is zeroed. Empirically I have found that the vast majority of shift factors can be known at compile time (or at least the valid range of integer), meaning it will compile to 1 instruction rather 2/3.

In naïve C, the shift would look like this:

    (y < 8*sizeof(x)) > (x << y) : 0

In practice, the "select" instruction is never needed. This approach to shifting also places never in that it feels more like 2's complement in that `x << y` is now equivalent to `x * (2*y)`.