Different code depends on different optimizations. A loop on an int** might benefit a lot from aliasing optimizations, because the compiler will assume that a[i

Different code depends on different optimizations. A loop on an int** might benefit a lot from aliasing optimizations, because the compiler will assume that a[i] will remain the same after writing to a[i][j]. Other code may not benefit at all. Likewise that loop may not benefit from signed overflow; instead an initialization loop that, by way of multiple level of macros, ends up doing a[i]=b[i]*1000/100, might become twice as fast if signed overflow rules let the compiler rewrite the assignment as a[i]=b[i]*10.