Reg2const arithmetic and tracking previously set ssa vars

[RolandMacDoland]

This PR addresses the addition of two functionalities:

• reg2const arithmetic: this requires to keep track of registers set with a constant value through the SetBitsOp for potential later reuse.
• Keep track of ssa variables: in the same line as above, there is now functionality to keep track of previously created ssa vars for later reuse.

This work also encompasses an architectural re-design of the package in three main parts:

• A QIR parser
• A QIR generator
• A module that extends the pyqir SimpleModule to handle custom define quantum functions.

[cqc-alec]

Agree about the first; not quite sure about the second: can we assume a ClassicalExpBox has no classical wires?

[cqc-alec]

Have you tried with latest pytket? This error was removed in CQCL/tket#589 .

[cqc-alec]

Could you please create a (low-priority) task to make SetBits and ClassicalExpBox support the trivial no-wires case? Ideally we should support this but maybe there are issues with pytket that prevent it.

[RolandMacDoland]

Could you please create a (low-priority) task to make SetBits and ClassicalExpBox support the trivial no-wires case? Ideally we should support this but maybe there are issues with pytket that prevent it.

Sure. But don't they already support it ? I thought from the examples above that setting them with empty registers was valid. Or, am I getting confused ?

Thanks for the review.

[cqc-alec]

Could you please create a (low-priority) task to make SetBits and ClassicalExpBox support the trivial no-wires case? Ideally we should support this but maybe there are issues with pytket that prevent it.

Sure. But don't they already support it ? I thought from the examples above that setting them with empty registers was valid. Or, am I getting confused ?

E.g. e0c46da

I still don't get why we have to raise an exception here (I mean, I get it in terms of how the code works currently, but I don't see why it has to be that way).

Anyway this is low-priority and shouldn't block merging this!

[RolandMacDoland]

Could you please create a (low-priority) task to make SetBits and ClassicalExpBox support the trivial no-wires case? Ideally we should support this but maybe there are issues with pytket that prevent it.

Sure. But don't they already support it ? I thought from the examples above that setting them with empty registers was valid. Or, am I getting confused ?

E.g. e0c46da

I still don't get why we have to raise an exception here (I mean, I get it in terms of how the code works currently, but I don't see why it has to be that way).

Anyway this is low-priority and shouldn't block merging this!

Tbf, I don't understand very clearly either what you are expecting. I am a little confused between the new behaviour of the ops and handling it in the context of correctness here. Maybe best to discuss that in Slack ?