[MIPS] Add new virtualization instructions

[Chao-Ying Fu]

Maciej W. Rozycki wrote:
>  Thanks, I can see what you mean now -- essentially VIRT64 is 
> the first 
> strictly microMIPS64 feature we're going to support.  The 
> issue looks to 
> me like the outcome of a previous decision to make -mips3 
> switch microMIPS 
> assembly into the 64-bit mode.  I believe this was your own 
> decision too, 
> :) that we accepted.  I think we can stick to it and just as 
> we already 
> enable all the optional microMIPS32 features for -mips1 
> assembly we do the 
> same for microMIPS64 and -mips3 assembly.
> 
>  Given the above how about:
> 
> #define ISA_SUPPORTS_VIRT64_ASE (mips_opts.isa == ISA_MIPS64R2
> 				 || (mips_opts.micromips
> 				     && ISA_HAS_64BIT_REGS 
> (mips_opts.isa)))
> 
> ?  We'll then do the same if e.g. DSP64 is added to the microMIPS 
> instruction set.

  I am ok with your proposal.  Let Richard and others respond, as Richard
approved my first patch already.

  Thanks!

Regards,
Chao-ying