TGSI's conditional discards take float arg and negate it, so GLSL to TGSI
generates a b2f and negates that value. Only, in NIR we want a proper
bool once again, so we compare with 0. This is a lot of pointless extra
instructions.
total instructions in shared programs: 39735 -> 39702 (-0.08%)
instructions in affected programs: 1342 -> 1309 (-2.46%)