recent troubles with float vectors & bitwise ops

[Paul Brook]

> > I'm partly worried about cross-platform compatibility, and what this
> > imples for other SIMD targets.
>
> Yes.  Here's a proposed definition:

<snip>

I agree this is the only sane definition.

I probably wasn't clear: My main concern is that if we do support this 
extension the internals should be implemented and documented in such a way 
that target maintainers (i.e. me) can figure out how to make it work on their 
favourite target. We should not just quietly flip some bit in the x86 
backend.

Paul