[Mesa-dev] killing off the address reg in tgsi

[Jose Fonseca]

On 29/01/15 21:20, Roland Scheidegger wrote:
> Hi,
>
> the address reg in tgsi is quite a nuisance. glsl-to-tgsi code assumes
> that indirections can only be done through the address reg and has quite
> some extra code to deal with this. Even though hardware and apis which
> worked like that are definitely old by now.
> Thus, I'm proposing the address reg be nuked. I am however not quite
> sure what the implications for drivers are, other than I'm certain
> llvmpipe can handle that already.
> For that reason, I suspect at least initially a new cap bit would be
> required so glsl-to-tgsi would skip the extra code.

A new cap might not be necessary -- supporting integer opcodes 
(PIPE_SHADER_CAP_INTEGERS) might suffice.

glsl-to-tgsi already varies its output depending on it.

> I tend to think
> longer term it would be great if it could be nuked completely, I am
> however not sure if that is easily done with drivers for old hw (such as
> r300) - I guess if necessary we could keep operations such as ARL (or
> even ARR though clearly not UARL!) and just define them to be usable
> with temp regs.
>
> Opinions?
>
> Roland

Jose