Bitwise rotate of integral

[Reimer Behrends]

On Tuesday, 8 January 2019 at 09:15:09 UTC, Patrick Schluter 
wrote:
> Are you sure it's dmd looking for the pattern. Playing with the 
> godbolt link shows that dmd doesn't generate the rol code (gdc 
> 4.8.2 neither).

Looking at the dmd compiler source code, it requires the value to 
be rotated to be of a type no larger than an int and the amount 
that the value is rotated by to be a constant.

Example: https://d.godbolt.org/z/m3HiPq

Interestingly, if you rotate by exactly 16 bits, it will generate 
less optimal code.