You're not wrong. The processor has a perfectly good zero/notzero check. There was absolutely no reason for the compiler to check if x^1==0.
You're not wrong. The processor has a perfectly good zero/notzero check. There was absolutely no reason for the compiler to check if x^1==0.
The (minor, but still) optimization that is enabled by assuming _Bool can contain only 1 or 0 is that negating a boolean value can be with x^1, without requiring a conditional.
That being said, for just testing the value, using the zero/nonzero test that every (?) cpu has is enough; I'm not sure what is achieved here with this more complex test.