Summary:
This PR adds machinery to cache the schema in an IR node, and allows lookups of (possibly) constant inputs by their names (instead of position). The new methods are:

- `at::optional<T> get<T>(Symbol name)` - if the argument called name is a constant, then casts it to type `T` and returns it. If it's not constant returns `nullopt`. Raises an error if there's no argument with that name.
- `at::optional<IValue> get<T>(Symbol name)` - like above, but packs the result in an IValue
- `Value* getValue(Symbol name)` - retrieves a `Value*` for an argument (no need to know its position).

All above functions currently inspect the attributes as well, but that's only so that I could start using them in other places in the JIT without disrupting our current functionality. I wanted this diff to be a preparation that doesn't change the semantics too much, and so both the tracer and script create nodes with attributes. The next PR will put that to a stop, and hopefully the changes we need to make to other components will be simpler thanks to what I did here.

One more thing I'd like to do before actually stopping creating the non-attributed nodes is to have a convenient way of creating a schema programmatically, matching nodes against it, and creating them without having to pack inputs into flat argument lists (which is quite error prone).

zdevito
Pull Request resolved: pytorch#9505

Reviewed By: ezyang

Differential Revision: D8915496

Pulled By: apaszke

fbshipit-source-id: 39d14fc9a9d73d8494f128367bf70357dbba83f5

Summary:
This PR adds machinery to cache the schema in an IR node, and allows lookups of (possibly) constant inputs by their names (instead of position). The new methods are:

- `at::optional<T> get<T>(Symbol name)` - if the argument called name is a constant, then casts it to type `T` and returns it. If it's not constant returns `nullopt`. Raises an error if there's no argument with that name.
- `at::optional<IValue> get<T>(Symbol name)` - like above, but packs the result in an IValue
- `Value* getValue(Symbol name)` - retrieves a `Value*` for an argument (no need to know its position).

All above functions currently inspect the attributes as well, but that's only so that I could start using them in other places in the JIT without disrupting our current functionality. I wanted this diff to be a preparation that doesn't change the semantics too much, and so both the tracer and script create nodes with attributes. The next PR will put that to a stop, and hopefully the changes we need to make to other components will be simpler thanks to what I did here.

One more thing I'd like to do before actually stopping creating the non-attributed nodes is to have a convenient way of creating a schema programmatically, matching nodes against it, and creating them without having to pack inputs into flat argument lists (which is quite error prone).

zdevito
Pull Request resolved: pytorch#9505

Reviewed By: ezyang

Differential Revision: D8915496

Pulled By: apaszke

fbshipit-source-id: 39d14fc9a9d73d8494f128367bf70357dbba83f5