Segher Boessenkool <seg...@kernel.crashing.org> writes: >> Although this looks/sounds complicated, the advantage is that everything >> remains up-to-date. If we instead added a second attribute and only >> defined it for instructions like *add_<shift>_<mode>, other instructions >> (including config/arm instructions) would still have type alu_shift_imm >> but would have a shift_imm_value of "none". > > I would make an attribute for the mode (or data size really), and one > that says the insn uses shifted data (since many arm insns have that, > just like record form on PowerPC is everywhere). And you can have that > one filled "by magic" usually!
I don't think this is really answering my point above though. What I meant is: we currently have several instructions in config/arm and config/aarch64 that have type alu_shift_imm. If we add some new on-the-side attributes A, but only update *some* of the alu_shift_imm instructions to define A (either directly or indirectly), then the other alu_shift_imm instructions will have the default values for A. This probably isn't the intended effect. Ideally, every alu_shift_imm instruction would specify correct attribute values for A (specifically, to indicate whether the shift value is in [1, 4] or not). In contrast, one advantage of replacing the existing alu_shift_imm type with two new types is that any existing reference to the old type will cause a build failure. So keeping everything in a single type attributes gives us static type checking that the information for each (former) alu_shift_imm instruction is complete. Similarly for any other type that needs to be split in the same way. I realise this won't convince you, and I'm not trying to. :-) Thanks, Richard
