ARM first & default LDC

[Iain Buclaw]

On Wednesday, 30 December 2020 at 16:03:56 UTC, Max Haughton 
wrote:
> On Wednesday, 30 December 2020 at 15:56:49 UTC, Ola Fosheim 
> Grøstad wrote:
>> On Wednesday, 30 December 2020 at 15:00:15 UTC, Max Haughton 
>> wrote:
>>> Cranelift already has basic ARM support too; I can't comment 
>>> on the quality of code generated.
>>
>> Are you thinking porting?
>
> No, just guessing how much work it would be. I would quite like 
> to get a basic backend going but it's much easier said than 
> done (i.e. most optimisations are fairly simple but generating 
> proper code and debug info at the end takes ages to test let 
> alone write)

The dmd back-end is surprisingly more segregated than you think, 
there are a bunch of entrypoint methods you can override (class 
Obj if I remember correctly), and from there, modules can act as 
their own encapsulation for emitting code for different CPUs - 
just swap the x87 modules for ARM modules in a hypothetical build.

Someone already did 70% of the work in untangling the back-end 
and made a toy ARMv4 backend several years ago.  Though it may 
not be in a salvageable state now, especially if the ultimate aim 
is to generate code for the Apple M1.