[Mesa-dev] i965 handling of ubo_load

[Eric Anholt]

Dave Airlie <airlied at gmail.com> writes:

> Hi Eric,
>
> so I've been playing around with gallium/ubos a bit more,
>
> I noticed something I wasn't sure abuot between the i965 vs and fs backends
>
> FS does
>      ir_constant *offset = ir->operands[1]->as_constant();
> fs_inst *pull = emit(fs_inst(FS_OPCODE_PULL_CONSTANT_LOAD,
>                                    packed_consts,
>                                    surf_index,
>                                    fs_reg(offset->value.u[0])));
>
> so it gets offset and derefs it later,
>
>      ir_constant *const_offset_ir = ir->operands[1]->as_constant();
>       unsigned const_offset = const_offset_ir ? const_offset_ir->value.u[0] : 0;
>
> does a check around it.
>
> What are the different ways ubo_load can get used?  I think I need to
> create a tgsi IR equivalent of it, since I don't think I can resolve
> the offset into the constant buffer at the glsl->tgsi translation
> stage.

Ah, I understand the question now.  Yeah, I think you need a TGSI
equivalent because you need to be able to pass which ubo is being
dereferenced from, even if you still decide to use the weird old
ARL/offset+ADDR pattern for loading constants with a varying index.
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