Re: [PATCH] decodetree: Allow 'dot' in opcode names

[Eduardo Habkost]

On Tue, Jan 12, 2021 at 11:15:38PM +0100, Philippe Mathieu-Daudé wrote:
> On 1/12/21 9:44 PM, Richard Henderson wrote:
> > On 1/12/21 8:41 AM, Philippe Mathieu-Daudé wrote:
> >> Some ISA use a dot in their opcodes. Allow the decodetree
> >> script to process them. The dot is replaced by an underscore
> >> in the generated code.
> > 
> > Given that you then have to remember to use '_' on the C side, what 
> > advantage
> > does this give?
> 
> The direct advantage is you can copy/paste the opcode in a PDF viewer
> without having to edit it :)
> 
> See i.e. some Loongson opcodes [*]:
> 
> MULT.G          011100 ..... ..... ..... 00000 010000   @rs_rt_rd
> DMULT.G         011100 ..... ..... ..... 00000 010001   @rs_rt_rd
> MULTU.G         011100 ..... ..... ..... 00000 010010   @rs_rt_rd
> DMULTU.G        011100 ..... ..... ..... 00000 010011   @rs_rt_rd
> 
> DIV.G           011100 ..... ..... ..... 00000 010100   @rs_rt_rd
> DDIV.G          011100 ..... ..... ..... 00000 010101   @rs_rt_rd
> DIVU.G          011100 ..... ..... ..... 00000 010110   @rs_rt_rd
> DDIVU.G         011100 ..... ..... ..... 00000 010111   @rs_rt_rd
> 
> MOD.G           011100 ..... ..... ..... 00000 011100   @rs_rt_rd
> DMOD.G          011100 ..... ..... ..... 00000 011101   @rs_rt_rd
> MODU.G          011100 ..... ..... ..... 00000 011110   @rs_rt_rd
> DMODU.G         011100 ..... ..... ..... 00000 011111   @rs_rt_rd
> 
> The other - remote - advantage I see is when using a disassembler
> based on decodetree (as AVR does), the opcode displayed also matches
> the specs. We are not yet there with MIPS, but I have something in
> progress...

Interesting.  So, the decodetree format is not used exclusively
inside the QEMU source tree, but also by other projects?  Is
there a specification somewhere else?

> 
> [*] https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg02509.html
> 

-- 
Eduardo