i965/nir/vec4: Implement single-element "mov" operations

Adds NIR ALU operations:
   * nir_op_imov
   * nir_op_fmov

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

src/mesa/drivers/dri/i965/brw_vec4_nir.cpp

@@ -655,6 +655,8 @@ brw_swizzle_for_nir_swizzle(uint8_t swizzle[4])
 void
 vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
 {
+   vec4_instruction *inst;
+
    dst_reg dst = get_nir_dest(instr->dest.dest,
                               nir_op_infos[instr->op].output_type);
    dst.writemask = instr->dest.write_mask;
@@ -667,6 +669,17 @@ vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
       op[i].abs = instr->src[i].abs;
       op[i].negate = instr->src[i].negate;
    }
+
+   switch (instr->op) {
+   case nir_op_imov:
+   case nir_op_fmov:
+      inst = emit(MOV(dst, op[0]));
+      inst->saturate = instr->dest.saturate;
+      break;
+
+   default:
+      unreachable("Unimplemented ALU operation");
+   }
 }
 
 void