On Wed, Dec 16, 2015 at 3:36 PM, Yuri Rumyantsev <ysrum...@gmail.com> wrote:
> Richard,
>
> Here is updated patch which includes (1) a test on exit proposed by
> you and (2) another test from PR68021 which is caught by new check on
> counted loop. Outer-loop unswitching is not performed for both new
> tests.
As said I don't think
/* If the loop is not expected to iterate, there is no need
for unswitching. */
- iterations = estimated_loop_iterations_int (loop);
- if (iterations >= 0 && iterations <= 1)
+ niters = number_of_latch_executions (loop);
+ if (!niters || chrec_contains_undetermined (niters))
{
is good. We do want to retain the estimated_loop_iterations check
as it takes into account profile data while yours lets through all
counted loops.
Also I don't see why SCEV needs to be able to analyze the IV to check
for validity.
Can you please split the patch into the part I suggested (which is ok)
and the rest?
Thanks,
Richard.
>
> Bootstrapping and regression testing did not show any new failures.
>
> Is it OK for trunk.
>
> ChangeLog:
> 2014-12-16 Yuri Rumyantsev <ysrum...@gmail.com>
>
> PR tree-optimization/68021
> PR tree-optimization/68906
> * tree-ssa-loop-unswitch.c : Include couple header files.
> (tree_unswitch_outer_loop): Add check that an exit is not inside inner
> loop, use number_of_latch_executions to detect non-iterated loops.
>
> gcc/testsuite/ChangeLog
> * gcc.dg/torture/pr68021.c: New test.
> * gcc.dg/torture/pr68906.c: Likewise.
>
> 2015-12-16 15:51 GMT+03:00 Richard Biener <richard.guent...@gmail.com>:
>> On Wed, Dec 16, 2015 at 1:14 PM, Yuri Rumyantsev <ysrum...@gmail.com> wrote:
>>> Hi All,
>>>
>>> Here is simple patch which cures the issue with outer-loop unswitching
>>> - added invocation of number_of_latch_executions() to reject
>>> unswitching for non-iterated loops.
>>>
>>> Bootstrapping and regression testing did not show any new failures.
>>> Is it OK for trunk?
>>
>> No, that looks like just papering over the issue.
>>
>> The issue (with the 2nd testcase at least) is that single_exit () accepts
>> an exit from the inner loop.
>>
>> Index: gcc/tree-ssa-loop-unswitch.c
>> ===================================================================
>> --- gcc/tree-ssa-loop-unswitch.c (revision 231686)
>> +++ gcc/tree-ssa-loop-unswitch.c (working copy)
>> @@ -431,7 +431,7 @@ tree_unswitch_outer_loop (struct loop *l
>> return false;
>> /* Accept loops with single exit only. */
>> exit = single_exit (loop);
>> - if (!exit)
>> + if (!exit || exit->src->loop_father != loop)
>> return false;
>> /* Check that phi argument of exit edge is not defined inside loop. */
>> if (!check_exit_phi (loop))
>>
>> fixes the runtime testcase for me (not suitable for the testsuite due
>> to the infinite
>> looping though).
>>
>> Can you please bootstrap/test the above with your testcase? The above patch
>> is
>> ok if it passes testing (no time myself right now)
>>
>> Thanks,
>> Richard.
>>
>>> ChangeLog:
>>>
>>> 2014-12-16 Yuri Rumyantsev <ysrum...@gmail.com>
>>>
>>> PR tree-optimization/68906
>>> * tree-ssa-loop-unswitch.c : Include couple header files.
>>> (tree_unswitch_outer_loop): Use number_of_latch_executions
>>> to reject non-iterated loops.
>>>
>>> gcc/testsuite/ChangeLog
>>> * gcc.dg/torture/pr68906.c: New test.
