No vector ops as yet. SSE only has direct support for 8- and 16-bit
saturation; handling 32- and 64-bit saturation is much more expensive.
Backports commit f49b12c6e6a75a5bd109bcbbda072b24e5fb8dfd from qemu
Opcodes are added for scalar and vector shifts, but considering the
varied semantics of these do not expose them to the front ends. Do
go ahead and provide them in case they are needed for backend expansion.
Backports commit d0ec97967f940bbc11dced83422b39c224127f1e from qemu
