Comment by lelanthran
7 hours ago
> Being able to assume certain things don't happen is powerful when you're writing optimisations, not doing that would have a real performance cost
A few of those are significant performance gains, the majority are not.
Emitting the instruction for a NULL pointer dereference is effectively no more costly than not emitting that instruction.
It's the code removal that's killing me.
What if the compiler is able to use that to determine that a whole code path is dead, and then significantly improve the surrounding function because of that?
Compilers optimise in multiple passes and removing things earlier can expose optimisation opportunities later that can affect other parts of the code too
> What if the compiler is able to use that to determine that a whole code path is dead,
Then it should warn "unreachable code".
> and then significantly improve the surrounding function because of that?
It's not simply the removal that is the problem, it's that the code is silently removed.