[Bug target/89071] AVX vcvtsd2ss lets us avoid PXOR dependency breaking for scalar float<->double and other scalar xmm,xmm instructions

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89071

--- Comment #18 from Uroš Bizjak <ubizjak at gmail dot com> ---
The only remaining question is on cvtsd2ss mem->xmm, where ICC goes with the
same strategy as with other non-conversion SSE unops:

   vmovsd    d(%rip), %xmm0
   vcvtsd2ss %xmm0, %xmm0, %xmm0

but with cvtss2sd:

   vxorpd    %xmm0, %xmm0, %xmm0
   vcvtss2sd f(%rip), %xmm0, %xmm0

Do we need XOR for cvtsd2ss mem->xmm?