Re: [PING][PATCH][PR65443] Add transform_to_exit_first_loop_alt

[Tom de Vries <Tom_deVries@mentor.com>]

On 08/06/15 17:55, Thomas Schwinge wrote:
> Hi Tom!
>
> On Mon, 8 Jun 2015 12:43:01 +0200, Tom de Vries <Tom_deVries@mentor.com> wrote:
>> There are two problems in try_transform_to_exit_first_loop_alt:
>> 1. In case the latch is not a singleton bb, the function should return
>>      false rather than true.
>> 2. The check for singleton bb should ignore debug-insns.
>>
>> Attached patch fixes these problems.
>
>> Fix try_transform_to_exit_first_loop_alt
>
>> 	PR tree-optimization/66442
>> 	* gimple-iterator.h (gimple_seq_nondebug_singleton_p): Add function.
>> 	* tree-parloops.c (try_transform_to_exit_first_loop_alt): Return false
>> 	if the loop latch is not a singleton.  Use
>> 	gimple_seq_nondebug_singleton_p instead of gimple_seq_singleton_p.
>
> Per my testing, the backport of this patch that you committed to
> gomp-4_0-branch, r224219, introduces a number of regressions in your
> OpenACC kernels test cases, specifically the »scan-tree-dump-times
> parloops_oacc_kernels "(?n)pragma omp target
> oacc_parallel.*num_gangs\\(32\\)" 1« tests.  Would you please have a
> look?
>
>

Hi Thomas,

I seem to have committed (to both trunk and gomp-4_0-branch) an older 
version of the patch, which contained an incorrect version of 
gimple_seq_nondebug_singleton_p.

I'll correct the mistake tomorrow morning.

Thanks,
- Tom

> Grüße,
>   Thomas
>
>
>>   gcc/gimple-iterator.h | 29 +++++++++++++++++++++++++++++
>>   gcc/tree-parloops.c   |  4 ++--
>>   2 files changed, 31 insertions(+), 2 deletions(-)
>>
>> diff --git a/gcc/gimple-iterator.h b/gcc/gimple-iterator.h
>> index 87e943a..76fa456 100644
>> --- a/gcc/gimple-iterator.h
>> +++ b/gcc/gimple-iterator.h
>> @@ -345,4 +345,33 @@ gsi_seq (gimple_stmt_iterator i)
>>     return *i.seq;
>>   }
>>
>> +/* Determine whether SEQ is a nondebug singleton.  */
>> +
>> +static inline bool
>> +gimple_seq_nondebug_singleton_p (gimple_seq seq)
>> +{
>> +  gimple_stmt_iterator gsi;
>> +
>> +  /* Find a nondebug gimple.  */
>> +  gsi.ptr = gimple_seq_first (seq);
>> +  gsi.seq = &seq;
>> +  gsi.bb = NULL;
>> +  while (!gsi_end_p (gsi)
>> +	 && is_gimple_debug (gsi_stmt (gsi)))
>> +    gsi_next (&gsi);
>> +
>> +  /* No nondebug gimple found, not a singleton.  */
>> +  if (gsi_end_p (gsi))
>> +    return false;
>> +
>> +  /* Find a next nondebug gimple.  */
>> +  gsi_next (&gsi);
>> +  while (!gsi_end_p (gsi)
>> +	 && is_gimple_debug (gsi_stmt (gsi)))
>> +    gsi_next (&gsi);
>> +
>> +  /* Only a singleton if there's no next nondebug gimple.  */
>> +  return gsi_end_p (gsi);
>> +}
>> +
>>   #endif /* GCC_GIMPLE_ITERATOR_H */
>> diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
>> index 02f44eb..c4b83fe 100644
>> --- a/gcc/tree-parloops.c
>> +++ b/gcc/tree-parloops.c
>> @@ -1769,8 +1769,8 @@ try_transform_to_exit_first_loop_alt (struct loop *loop,
>>   				      tree nit)
>>   {
>>     /* Check whether the latch contains a single statement.  */
>> -  if (!gimple_seq_singleton_p (bb_seq (loop->latch)))
>> -    return true;
>> +  if (!gimple_seq_nondebug_singleton_p (bb_seq (loop->latch)))
>> +    return false;
>>
>>     /* Check whether the latch contains the loop iv increment.  */
>>     edge back = single_succ_edge (loop->latch);
>> --
>> 1.9.1
>>