This is relevant for float comparisons. Some of them will start as something like: Equal(EqualOrUnordered(left, right), 0) Then we will canonicalize this to: BitXor(EqualOrUnordered(left, right), 1) But then the code generator will emit the BitXor separately, so we'll have some nasty code to perform the comparison followed by a xor. That's goofy. Note that this problem goes away if we also do branch fusion. For example both of these are fine: Branch(BitXor(EqualOrUnordered(left, right), 1)) Check(BitXor(EqualOrUnordered(left, right), 1)) We won't see the Branch case because of strength reduction, but we will see the Check case, and that's OK - we'll chew through the BitXor.