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Re: [PATCH] decodetree: Allow 'dot' in opcode names
From: |
Eduardo Habkost |
Subject: |
Re: [PATCH] decodetree: Allow 'dot' in opcode names |
Date: |
Tue, 12 Jan 2021 17:28:09 -0500 |
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