[IRSim] Remove early check from similarity matching such that commutative...

[IRSim] Remove early check from similarity matching such that commutative instructions are checked correctly when using the same value.

When the first commutative instruction in a region using the same value in both positions was compared to a corresponding instruction with two different values, there was an early check that determined that since the values were new, it was true that these values acted in the same way structurally. If this was not contradicted later in the program, the regions were marked as similar. This removes that check, so that it is clear that the same value cannot be mapped to two different values.

Reviewer: paquette

Differential Revision: https://reviews.llvm.org/D124775