Comment # 7 on bug 55256 from Alex Deucher

There are some asic specific shader instruction behaviors for r6xx/r7xx chips
that need to be ported to the LLVM backend.  A couple that come to mind:
- Trig functions (see tgsi_setup_trig() in r600_shader.c)
- AR register handling (see load_ar() in r600_asm.c)