HLSL offsetting

[Zebediah Figura]

On 6/9/22 17:38, Matteo Bruni wrote:
>> My current vision of SMxIR is that it should be a one-to-one
>> representation of actual instructions, writable without any lowering
>> passes (and hence any passes that are done on it should be optimization
>> only, with the *possible* exception of RA.) In a sense, it's what we
>> have already with sm4_instruction and such, except that we'd be storing
>> it and doing passes on it rather than just writing it directly.
> 
> Right, I agree with the general idea. In practice it might turn out to
> be useful to relax the 1:1 requirements a bit and introduce some
> "extra" instructions (that would be quickly lowered to real ones) if
> that makes the HIR->SMxIR conversion easier.
> 
> Something related we already discussed: SM1IR and SM4IR are going to
> be different, obviously, but we want to try and architect them so that
> the optimization passes machinery and most of the actual passes can be
> shared between the two.

Hmm, I don't remember that discussion. My take is that if there's only 
two backends it probably makes more sense not to (over-)engineer any 
common framework, but rather just make them look similar enough that we 
can copy-paste things from one to the other. (It's an unpopular opinion, 
perhaps, but I think that code duplication is an important and often the 
best method of code deduplication.)

Of course, I don't know what the sm6 backend will look like, when and if 
we add it.