Re: [PATCH v4 22/31] target/ppc: Implement PNOP

[Richard Henderson]

On 5/12/21 1:54 PM, matheus.ferst@eldorado.org.br wrote:
> +### Prefixed No-operation Instruction
> +
> +&PNOP           invalid_suffix:bool
> +@PNOP           000001 11 0000-- 000000000000000000     \
> +                ................................        &PNOP
> +
> +{
> +  ## Invalid suffixes: Branch instruction
> +  # bc[l][a]
> +  PNOP            ................................      \
> +                  010000--------------------------      @PNOP invalid_suffix=1

For other cpus it has often turned out to be helpful to have a trans_INVALID or 
UNDEF or RESERVED or suchlike to use for cases like this.  That way you don't 
need a special argument set, nor to set a flag as you do for each of these.

Also, the invalid suffixes themselves do not overlap, so you can get a slightly 
better decode via nested [], like so:

{
  [
    INVALID ...
    INVALID ...
    ...
  ]
  NOP ...
}


r~