recent troubles with float vectors & bitwise ops

[Paolo Bonzini]

> The IA-32 instruction set does distignuish between integer and
> floating point bitiwse operations.  In addition to the single-precision
> floating-point bitwise instructions that tbp mentioned (ORPS, ANDPS,
> ANDNPS and XORPS) there are both distinct double-precision floating-point
> bitwise instructions (ORPD, ANDPD, ANDNPD and XORPD) and integer bitwise
> instructions (POR, PAND, PANDN and PXOR).  While these operations all do
> the same thing, they can differ in performance depending on the context.

Oops, I only remembered PS vs. PD (I remembered POR as MMX instructions 
only).  I believe that optimizing this should be a task for the x86 
machine dependent reorg.

Paolo