Re: [Qemu-devel] [sw-dev] [RFC] RISC-V Decoder generator

[Bastian Koppelmann <kbastian@mail.uni-paderborn.de>]

Hi Richard,

On 10/21/2017 08:44 AM, Richard W.M. Jones wrote:
> On Fri, Oct 20, 2017 at 03:46:54PM +0200, Bastian Koppelmann wrote:
>> I asked you for feedback some while ago regarding a modular RISC-V QEMU
>> target (see discussion [1]). I tried getting it to work with the good
>> old C preprocessor and quickly realized that it is too limiting. Instead
>> I created a data-driven decoder generator written in python (see the
>> code on github [2]) using YAML as a description language.
>>
>> I'd like to get some feedback whether this is acceptable to be
>> upstreamed to QEMU or if you have any suggestions for improvements.
>> Right now only RV32I instruction are implemented in this scheme.
> 
> My suggestion would be to reimplement (part of) the s390x decoder
> using this scheme.  That would give us a direct comparison of how your
> scheme is better or worse than the existing macros.

Yeah that would be a great test. However I'm not sure if it's worth the
effort. AFAIK s390x will not be extended with new instructions, so there
is no need for a new scheme unless it helps making the code better
maintainable. But that's up to the s390x maintainers.

> 
> Will you be at the KVM Forum next week?

No, sorry. I'm at the verge of graduating from University, so my time is
very limited right now :(

Cheers,
Bastian