Clarify assembly review

[sonti-lurker]

subtle/src/lib.rs

Lines 332 to 338 in 6b6a81a

	// This loop shouldn't be shortcircuitable, since the compiler
	// shouldn't be able to reason about the value of the `u8`
	// unwrapped from the `ct_eq` result.
	let mut x = 1u8;
	for (ai, bi) in self.iter().zip(_rhs.iter()) {
	x &= ai.ct_eq(bi).unwrap_u8();
	}

Doesn't really rule out a simple if x == 0 goto end optimization. I assume the assembly was inspected but that should probably be annotated because it would have to be repeated when the compiler does smarter things.