void generate_get_buffer_size(fs_inst *inst, struct brw_reg dst,
                                  struct brw_reg src,
                                  struct brw_reg surf_index);
-   void generate_ddx(enum opcode op, struct brw_reg dst, struct brw_reg src);
-   void generate_ddy(enum opcode op, struct brw_reg dst, struct brw_reg src);
+   void generate_ddx(const fs_inst *inst,
+                     struct brw_reg dst, struct brw_reg src);
+   void generate_ddy(const fs_inst *inst,
+                     struct brw_reg dst, struct brw_reg src);
    void generate_scratch_write(fs_inst *inst, struct brw_reg src);
    void generate_scratch_read(fs_inst *inst, struct brw_reg dst);
    void generate_scratch_read_gen7(fs_inst *inst, struct brw_reg dst);
 
  * appropriate swizzling.
  */
 void
-fs_generator::generate_ddx(enum opcode opcode,
+fs_generator::generate_ddx(const fs_inst *inst,
                            struct brw_reg dst, struct brw_reg src)
 {
    unsigned vstride, width;
 
-   if (opcode == FS_OPCODE_DDX_FINE) {
+   if (inst->opcode == FS_OPCODE_DDX_FINE) {
       /* produce accurate derivatives */
       vstride = BRW_VERTICAL_STRIDE_2;
       width = BRW_WIDTH_2;
  * left.
  */
 void
-fs_generator::generate_ddy(enum opcode opcode,
+fs_generator::generate_ddy(const fs_inst *inst,
                            struct brw_reg dst, struct brw_reg src)
 {
-   if (opcode == FS_OPCODE_DDY_FINE) {
+   if (inst->opcode == FS_OPCODE_DDY_FINE) {
       /* produce accurate derivatives */
       struct brw_reg src0 = brw_reg(src.file, src.nr, 0,
                                     src.negate, src.abs,
         break;
       case FS_OPCODE_DDX_COARSE:
       case FS_OPCODE_DDX_FINE:
-         generate_ddx(inst->opcode, dst, src[0]);
+         generate_ddx(inst, dst, src[0]);
          break;
       case FS_OPCODE_DDY_COARSE:
       case FS_OPCODE_DDY_FINE:
-         generate_ddy(inst->opcode, dst, src[0]);
+         generate_ddy(inst, dst, src[0]);
         break;
 
       case SHADER_OPCODE_GEN4_SCRATCH_WRITE: