A compiler inlines a tiny accessor and then, under the as-if rule, hoists a load of a non-volatile global out of a loop because nothing in the loop body writes it. Another thread mutates that global concurrently. Why is this hoist legal from the standard's point of view?
// global, plain int (not atomic, not volatile)
int g = 0;
long sum(int n) {
long s = 0;
for (int i = 0; i < n; ++i) s += g; // g re-read each iter?
return s;
}