> Physically, a computer is imperative, has mutating state, and is filled with all kinds of possible race conditions. Those are too difficult for compiler writ

> Physically, a computer is imperative, has mutating state, and is filled with all kinds of possible race conditions. Those are too difficult for compiler writers to reason about. While you're mutating the finite set of registers in your high-level C code - just like a real computer does - clang is swapping those out for operations on an infinite number of immutable registers.