pan/mdg: Precolour blend inputs

Instead of requiring an explicit unoptimized move, we can implicitly colour the blend input intrinsic to r0, where it will be preloaded; this is a simple task for RA, and does not conflict with anything. If there are multiple duplicate loads, the latter ones can just be simple moves which will be copypropped.

We don't need to include a explicit synthetic load, since (scanning backwards) the read will cause the input to become live at the right time and the lack of an explicit write will keep it live from the beginning of the shader. So no need to make it more complicated than it needs to be.

Saves a cycle in blend shaders.

Signed-off-by: Alyssa Rosenzweig alyssa.rosenzweig@collabora.com