recent troubles with float vectors & bitwise ops

[Tim Prince]

Paolo Bonzini wrote:
>
> 2) selection operations on vectors, kind of (v1 <= v2 ? v3 : v4).  These
> can be written for example like this:
>
>      cmpleps xmm1, xmm2   ; xmm1 = xmm1 <= xmm2 ? all-ones : 0
>      andnps  xmm4, xmm1   ; xmm4 = xmm1 <= xmm2 ? 0 : xmm4
>      andps   xmm1, xmm3   ; xmm1 = xmm1 <= xmm2 ? xmm3 : 0
>      orps    xmm1, xmm4   ; xmm1 = xmm1 <= xmm2 ? xmm3 : xmm4
SSE4 introduces specific instruction support, with a shorter sequence 
for this purpose.  It seems to be quite difficult to persuade gcc to use it.