A gcc-cris bug?

[Paolo Bonzini]

Graham Stott wrote:
> All,
> 
> 
>>>One problem is the insn "foo = 0" gets moved after the loop 
>>>end because
>>>loop optimize determines that it's loop invariant but isn't checking 
>>>if the insn would modify the loop termination condition.
> 
> Actually this isn't a problem because the loop optimizer does notice
> that the loop termination condition has been modified.
> 
> int main()
> {
>   int foo = 100;
>   int i;
> 
>   for (i = A; i < foo; i++)
>     foo = B;
> }
> 
> When B > A the loop iterates the correct # of times which is B - A + 1,
> infact the whole loop gets optimized away :-). But when B <= A we end up
> with a decrement-until-zero loop starting at B-A which for some reason
> doesn't get optimized away.

Optimizing away the loop may only paper over the problem.  What happens 
if you add a "if (i != B + 1) abort ();", in the various cases?

I'm sending a patch shortly.

Paolo