On 10/06/2011 07:24 PM, Ulf Magnusson wrote:
> bool overflow_unsafe(unsigned int a, unsigned int b) {
> const unsigned int sum = (int8_t)a + (int8_t)b;
> return (int8_t)sum != sum;
> }
>
> bool overflow_safe(unsigned int a, unsigned int b) {
> const int sum = as_signed_8(a) + as_signed_8(b);
> return as_signed_8(sum) != sum;
> }
I get this:
overflow:
sxtb r1, r1
sxtab r1, r1, r0
sxtb r0, r1
subs r0, r0, r1
it ne
movne r0, #1
bx lr
It's not obvious to me how you'd improve on it.
Andrew.
