Invoking memories.

[cgyurgyik]

This is a blocker for progress in #369.
Before Invoke, we used memories in a component with the go-done interface in the following manner:

component foo
(go: 1, clk: 1, x_read_data: 32, x_done: 1)
 -> 
(done: 1, x_addr0: 1, x_write_data: 32, x_write_en: 1) { ... }

main() -> () {
  ...
  comp_foo = foo;
  x = std_mem_d1(32, 1, 1);
  ...
    group run_foo {
      // Read from `x`.
      x.addr0 = comp_foo.x_addr0;
      comp_add0.x_read_data = x.read_data;
      
      // Write to `x`
      x.write_data = comp_foo.x_write_data;
      x.write_en = comp_foo.x_write_en;

      comp_foo.x_done = x.done;
      comp_foo.go = 1'd1;
      run_foo[done] = comp_foo.done;
    }
}

To transition to Invoke, the input wires for a memory read is trivial:
invoke comp_foo(x_read_data = x.read_data, x_addr0 = x.addr0)();

So, how do we write to x?

invoke comp_foo(..., x.write_en = x_write_en, x.write_data = x_write_data)(); // Flip-flop CompPort, ThisPort

This is what seems to be discussed in the original Invoke issue. This would mean changing our current implementation in Dahlia and calyx-py to use PortDefs instead of CompVars for both parameters and arguments (which makes sense, since we're using ThisPorts) (fixed in #383 , Dahlia #347).

[sampsyo]

Invokable memories do seem like a good idea. An idea we've discussed elsewhere, but I've lost track of where, is somehow supporting multiple "methods" for components. You'd be able to invoke a memory in two different ways, somehow: like invoke my_mem.read(addr, data) and invoke my_mem.write(addr, data). Perhaps we don't have to go all that way (which would be quite a refactoring!) just to get this effect, but thought I'd mention it here as one possible, high-effort option.

[sampsyo]

@cgyurgyik patiently pointed out to me that I had misunderstood the issue and the above comment is completely irrelevant and should be ignored. 😇

[cgyurgyik]

From today's discussion: Don't use Ports for component port definitions. Just use Strings.

[cgyurgyik]

Dahlia frontend support in Dahlia #349.