> Any function that uses both of these violates strict aliasing rules

More specifically, any function that uses both of these to access the same data violates strict aliasing rules. But this would imply that the data is being loaded redundantly, which seems unlikely in an implementation where speed is a top priority.

For example, I do not believe the following function violates strict aliasing rules:

    void foo(char *p) {
      bar(UNALIAGNED_LOAD64(p), UNALIGNED_LOAD32(p+8));
    }