Re: [PATCH, AARCH64] support s2_<op1>_<Cn>_<Cm>_<op2> sys reg

[Yufeng Zhang <Yufeng dot Zhang at arm dot com>]

Hi Zhenqiang,

On 11/12/13 06:12, Zhenqiang Chen wrote:
> Hi,
>
> Current parse_sys_reg only supports s3_<op1>_<Cn>_<Cm>_<op2>. But
> according to the document,
>
>    integer sys_op0 = 2 + UInt(o0)
>
> o0 is bit-19.
>
> So sys_op0 can be 2 or 3.
>
> This patch changes GAS to to add s2_<op1>_<Cn>_<Cm>_<op2>  support.
> OK for trunk?

For MSR/MRS instruction, it is correct that sys_op0 can be 2 or 3. 
However, it doesn't necessarily mean that the encoding space of 
sys_op0==2 contains reserved area for implementation defined system 
registers.

The ARMARMv8 mentions in section C4.2.6 "Op0==0b11, Moves to and from 
non-debug System registers and special-purpose registers" that:

"The instructions that move data to and from non-debug system registers 
are encoded with Op0==0b11, except that some of this encoding space is 
reserved for IMPLEMENTATION DEFINED functionality."

The document however doesn't mention about the implementation defined 
functionality in section C4.2.5 "Op0==0b10, Moves to and from debug, 
qtrace, and Execution environment System registers".

Is there any named system register in the op0==0b10 encoding space that 
you would like to add support for, by extending the syntax?

Also if we go head with the patch, please also add some tests to 
gas/testsuite/gas/aarch64/sysreg.[d|s].


Thanks,
Yufeng