LLVM has trouble compiling the old implementation, (presumably) because `leading_zeros` is thought to be a `u7` rather than a `u6`, which means `63 - clz` is not equivalent to `63 ^ clz`, which means it can't deduce that the final condition can simply be flipped. (I am assuming `usize` is a `u64` here for ease of understanding, but it's the same for any power of 2)
https://zig.godbolt.org/z/Pbj4P7ob3
The new version is slightly better too because `isMinLayer(maxInt(usize))` is now well-defined behavior.
ff5850183e