!UPSTREAM: i965/vec4: if register allocation fails, don't try to schedule.

Otherwise the scheduler would be invoked with prog_data->total_grf ==
0, causing havoc.

In a future patch, this will allow us to try compiling a geometry
shader in DUAL_OBJECT mode with spilling disabled, and then fall back
to DUAL_INSTANCED mode if that failed.

TODO:
- Move earlier.
!UPSTREAM: i965/vec4: Allow MOV from vec4 or vec8 into vec4.

This can only happen when doing the vertex reordering workaround on
DUAL_INSTANCED geometry shaders.  For vec8 to vec4 moves, we
arbitrarily move the first half of the vec8 into the vec4.  The vertex
reordering workaround takes care to ensure that this doesn't cause a
problem.

TODO:
- Fold into vertex reordering code.
squash! !UPSTREAM: i965/gs: If a DUAL_OBJECT gs would spill, fall back to DUAL_INSTANCED.

Change DEBUG flag to "nodualobj"
!UPSTREAM: i965/vec4: fix up primitive ID workaround for DUAL_INSTANCE dispatch.

TODO:

- Add better explanatory comments in generate_vec4_instruction.

- Modify the patch that does similar things to
  generate_vec4_instruction's MOV case and add better explanatory
  comments to it too.