On Wed, Jul 8, 2015 at 5:51 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Wed, Jul 8, 2015 at 8:52 AM, Bin.Cheng <amker.ch...@gmail.com> wrote:
>> Hi,
>> Function fill_always_executed_in_1 computes basic blocks' always
>> executed information, and it has below code and comment:
>>
>> /* In a loop that is always entered we may proceed anyway.
>> But record that we entered it and stop once we leave it. */
>> inn_loop = bb->loop_father;
>>
>> Then in following iterations, it breaks the loop if basic block not
>> belonging to the inner loop is encountered. This means basic blocks
>> after inner loop won't have always executed information computed, even
>> they dominates the original loop's latch.
>>
>> Am I missing something? Why is that?
>
> To improve here it would need to verify that all exits of the inner loop
> exit to the same BB of the outer loop and that no exit skips any blocks
> in the outer loop. Like for
But we are working on dominating tree anyway. Won't dominating latch be enough?
Thanks,
bin
>
> for (;;)
> {
> for (;;) { if (x) goto skip; if (y) break }
> foo();
> skip:
> }
>
> so it is just a simple and conservative algorithm it seems. It's also
> quadratic in the number of BBs of the outermost loop.
>
>> Thanks,
>> bin
