I didn’t know that SetErrorMode(SEM_NOALIGNMENTFAULTEXCEPT) was a thing, until I wrote a bad test that wouldn’t crash.
Digging into it, I found that a movaps instruction was being rewritten as movups, which was a thoroughly confusing thing to see.
The one clue I had was that a fault due to an unaligned load had been observed in non-test code, but did not reproduce when written as a test using the google-test framework. A short hunt later (including a failed attempt at writing a small repro case), I found an explanation: google test suppresses this class of failure.
The code below will successfully demonstrate the behavior, printing out the SIMD load instruction before and after calling the function with an unaligned pointer.