5 ms·
There's the secondary effects of missed optimisations too: if every operation is checked for overflow, there's much less scope for reordering/collapsing/vectori
by dbaupp 12y ago
There's the secondary effects of missed optimisations too: if every operation is checked for overflow, there's much less scope for reordering/collapsing/vectorising operations, (this is also especially important in tight loops where the core loop can easily be less than 20 instructions, so 2 extra is significant).
- ufo 12y ago> if every operation is checked for overflow, there's much less scope for reordering/collapsing/vectorising operations Lets pretend that instead of "put a conditional jump after every operation", we try to model things as "pretend all integers are infinite precision, blow up if overflow happens at some point". So for example, we would be OK with rewriting int x = MAX_INT int y = (x + 1) - 1 //overflow - BOOM! with int x = MAX_INT int y = x; //no overflow Yes, this means that the program does different things depending on the level of optimization but are there any reordering/vectorizing possibilities that get blocked now?