How hard would it be to create a new backend in D?

[rempas]

On Saturday, 6 August 2022 at 07:10:43 UTC, user1234 wrote:
>
> I suggested to experiment MIR like that, it was not a proposal 
> on the final design.
> Experimenting using LLVM IR could be useful to determine if 
> working seriously on the project is worth.
>
> Anyway if you want to put your hand in the hard stuff from the 
> start I think you have two options.
>
> 1. Create an AST visitor that generate MIR format after DMDFE 
> semantics
> 2. Create the MIR representation after the part of the backend 
> that generate DMD IR (s2ir, e2ir, etc.) has run.
>
> The second option might be easier because the production will 
> most of the time map 1:1 to a MIR equivalent.
>
> The first option is IMO would be harder because of forward 
> references and imports. and even without that, that would 
> require to split visiting in several passes (decls, aggregate 
> members, function headers, function bodies)
>
Thank you for the info! The thing is (and why I make the question 
originally)
how do I find info about how to get started? I don't even know 
how DMD
works and how it's IR works. Does DMD's frontend parses the text 
and then
outputs something like LLVM-IR (but for DMD) which we can take 
and then
translate it to the final backend that we need (in our case mir) 
or something
else? That's what I want to know. So yeah, is there a legit 
documentation or
something or do backend developers have to guess how things work 
and do
"hacking"?

> About the "how hard" I think that compiler programming is not 
> hard but that takes time. I estimate that this could take you 
> from 1 month to 3 months to finish however you 'd get results 
> much earlier, e.g if you handle just a few constructs.
That's actually pretty nice! I don't mind about putting the work 
but I
mind the work to be strain-forward and make sense. I would expect 
to
see actual documentation and info about how things work in 
detail. If
not, then I would probably spend the time to design and implement 
my
own language.