Verifying vectorized Rust revisited

Research is characterized by allowing yourself to make mistakes: performing experiments; drawing conclusions; later, realizing that your experiment was not sufficient and you got it wrong; and trying again. Back in March, we thought that we knew how to deal with vectorized Rust: tell the compiler not to auto-vectorize code; tell the compiler not to use vector instructions; and use existing conditional compilation feature flags to disable hand-vectorized code. Unfortunately, two of those three ideas don’t work – but we think we have a viable approach now.