SRA bit-field optimization

[Eric Botcazou]

> It's not really introduced, it's just made explicit earlier, in the
> tree level, such that we can better optimize it.  I'll give you that
> this isn't the simplest way to model operations on 32-bit words in
> 64-bit variables, but in the end we'd get the same code either way, at
> least for variables that are not pushed to memory.

OK, thanks for the clarification.

Could you install the aforementioned patchlet?  FWIW it has successfully 
passed a complete bootstrap + Ada regression testing on x86-64.

-- 
Eric Botcazou