The arm64 JIT applied the plain prefix rules to every op. Several ops
don't follow them, and the interpreter and IR frontend know which:
- vabs and vneg are vmov with the abs/negate bit forced, so a negate in
the S prefix doesn't negate twice.
- vsat1 doesn't apply the D saturation.
- vrcp, vrsq, vsqrt, vnrcp (and the rest of that group) apply S and D to
the last lane only, from prefix position 0.
- vzero, vone and vidt are changed by a pending S prefix.
- vdiv, vscl, vfad/vavg and vrot each have their own rule.
- vuc2i and friends with an S prefix.
Hand these to the interpreter, exactly where the IR frontend does. Also
mask what mtvc writes to a control register (the low 20 bits of a prefix,
12 of the D prefix), as the IR already did.
Goes from 19 ops differing from hardware in cpu/vfpu/prefix_consume to
the 3 that differ on every core, and clears cpu/vfpu/prefix_ctrl.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
