In order to compute centroid varyings correctly, the fragment shader
needs to be able to load the current pixel/sample mask into a flag
register. This patch adds an opcode to the fragment shader back-end
to do this; the opcode gets translated into the instruction
mov(1) f0<1>UW g1.14<0,1,0>UW { align1 WE_all }
Since this instruction clobbers f0, instruction scheduling has to
treat it the same as instructions that have a conditional modifier.
Reviewed-by: Eric Anholt <eric@anholt.net>
Paul Berry
3f929efa28