Re: [Qemu-devel] [PATCH v7 04/20] target/mips: Add and integrate MXU decoding engine placeholder

[Stefan Markovic]

In that case, I guess this should be OK for now, as MXU support is 
initiated by Craig and this will be

an easy add-on when he provide necessary information.


Reviewed-by: Stefan Markovic <address@hidden>


On 28.10.18. 19:39, Aleksandar Markovic wrote:
>> Subject: Re: [PATCH v7 04/20] target/mips: Add and integrate MXU decoding 
>> engine > placeholder
>>
>>> Is the best way to implement this to include processing of MUL, CLZ,
>>> CLO, SDBBP instructions into decode_opc_mxu as their encodings aren't
>>> overlaid by MXU instructions considering MIPS SPECIAL2 instruction
>>> pool and MXU Instruction Set?
>> The problem is that we don't have the documentation for Ingenic's base
>> instruction set. My understanding is that Craig established necessity of
>> including non-MXU MUL into decode_opc_mxu() by experimentation,
>> or by looking at Ingenic's toolchain source code.
>>
>> Note that CLZ, CLO, SDBBP are moved from SPECIAL2 to another
>> place in opcode space in MIPS R6.
>>
>> Craig, can you offer any insight on CLZ, CLO, SDBBP in Ingenic's base
>> instruction set? They are in SPECIAL2 opcode space for MIPS pre-R6.
>>
>> Worse come to worst, I recommend adding "TODO" comment to an
>> appropriate place in decode_opc_mxu(), and go forward without handling
>> CLZ, CLO, SDBBP - given that all changes in this series are just the first
>> phase of implementing MXU support - they won't affect any production
>> code at this moment.
>>
> I think this comment should be added to the decode_opc_mxu(), within patch 11:
>
>      /*
>       * TODO: Investigate necessity of including handling of
>       * CLZ, CLO, SDBB in this function, as they belong to
>       * SPECIAL2 opcode space for regular pre-R6 MIPS ISAs.
>       */
>
> Thanks,
> Aleksandar