[_a_a_a_]

to the downvoter: I thought this was a reasonable question? Semantic equivalence is IIRC undecidable in general. Some languages (Backus' FL?) try to deal with that but I dunno.

[tyingq]

> Semantic equivalence is IIRC undecidable in general.

They did mention code, and said "similarity" rather than equivalence.

But, as a trivial example, two different pieces of code can compile down to the same AST, or bytecode, or assembler.