# R600 shader from NIR

This code is an attempt to implement a NIR backend for r600.

## State

piglits gpu passes mostly like with TGSI, there are some fixes but also a few regressions.

CTS gles
 - 2 passes like with TGSI
 - 3 no regressions, a few fixes compared to TGSI
 - 31
    * a few fixes with interpolation specifiers
    * a few regressiones with seperate_shader.random
    * syncronization has some unstable tests, this might be because global syncronization is missing (in both)

## Currently missing features w.r.t. TGSI:

 - struct support

## Needed optimizations:

  - Register allocator and scheduler (Could the sb allocator and scheduler
    be ported?)

  - peepholes:
    - compare + set predicate

  - copy propagation:
    - Moves from inputs are usually not required, they could be forwarded
    - texture operations often move additional parameters in extra registers
      but they are actually needed in the same registes they come from and
      could just be swizzled into the right place
      (lower in NIR like it is done in e.g. in ETNAVIV)


## Problems

  - struct IO is not lowered. lower_io would need a rewrite of most IO in
    VS, GS, and FS
  - fp64 needs additional lowering to replace load, split and merge with vec2 ops
    nir_to_tgsi has some stuff there

## Work plan

The implementation uses C++ to separate the code for the different
shader types and the byte code generation backends. The initial attempt
will use the already available r600_asm code