emit_op2(p, OPCODE_DP3, spot, 0, negate(VPpli), spot_dir_norm);
emit_op2(p, OPCODE_SLT, slt, 0, swizzle1(spot_dir_norm,W), spot);
emit_op2(p, OPCODE_DP3, spot, 0, negate(VPpli), spot_dir_norm);
emit_op2(p, OPCODE_SLT, slt, 0, swizzle1(spot_dir_norm,W), spot);