[Synth] Add a folder/canonicalization for synth.xor_inv

[uenoku]

Add a folder/canonicalization for xor_inv. Generally same to comb.xor but no flatten.

xor_inv(a, not a, b) -> xnor_inv(not b)
xor_inv(a, 1111111) -> xor_inv(not a)
xor_inv(a, 0000000) -> a 
xor_inv(a, c0, c1) -> xor_inv(a, c0^c1) 
xor_inv(a, not c0) -> xor_inv (x, ~c0)
xor_inv(a, not (xor_inv/aig_inv not b)) -> xor_inv(a, b)

[okekayode]

Hi @uenoku, can i take / be assigned this issue please. Thanks

[uenoku]

Thank you!

[okekayode]

Thank you!

For the first rule: xor_inv(a, not a, b) -> b can you explain to me why its b and not ~b?

[uenoku]

Thank you for catching it, ~b is correct.