Re: [PATCH GCC][11/13]Annotate partition by its parallelism execution type

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Jun 20, 2017 at 11:18 AM, Bin.Cheng <amker.cheng@gmail.com> wrote:
> On Fri, Jun 16, 2017 at 11:10 AM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Mon, Jun 12, 2017 at 7:03 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>>> Hi,
>>> This patch checks and records if partition can be executed in parallel by
>>> looking if there exists data dependence cycles.  The information is needed
>>> for distribution because the idea is to distribute parallel type partitions
>>> away from sequential ones.  I believe current distribution doesn't work
>>> very well because it does blind distribution/fusion.
>>> Bootstrap and test on x86_64 and AArch64.  Is it OK?
>>
>> +  /* In case of no data dependence.  */
>> +  if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
>> +    return false;
>> +  /* Or the data dependence can be resolved by compilation time alias
>> +     check.  */
>> +  else if (!alias_sets_conflict_p (get_alias_set (DR_REF (dr1)),
>> +                                  get_alias_set (DR_REF (dr2))))
>> +    return false;
>>
>> dependence analysis should use TBAA already, in which cases do you need this?
>> It seems to fall foul of the easy mistake of not honoring GCCs memory model
>> as well ... see dr_may_alias_p.
> I see.  Patch updated with this branch removed.
>
>>
>> +  /* Further check if any data dependence prevents us from executing the
>> +     partition parallelly.  */
>> +  EXECUTE_IF_SET_IN_BITMAP (partition->reads, 0, i, bi)
>> +    {
>> +      dr1 = (*datarefs_vec)[i];
>> +      EXECUTE_IF_SET_IN_BITMAP (partition->writes, 0, j, bj)
>> +       {
>>
>> what about write-write dependences?
>>
>> +  EXECUTE_IF_SET_IN_BITMAP (partition->reads, 0, i, bi)
>> +    {
>> +      dr1 = (*datarefs_vec)[i];
>> +      EXECUTE_IF_SET_IN_BITMAP (partition->writes, i + 1, j, bj)
>> +       {
>> +         dr2 = (*datarefs_vec)[j];
>> +         /* Partition can only be executed sequentially if there is any
>> +            data dependence cycle.  */
>>
>> exact copy of the loop nest follows?!  Maybe you meant to iterate
>> over writes in the first loop.
> Yes, this is a copy-paste typo.  Patch is also simplified because
> read/write are recorded together now.  Is it OK?

Ok.

Thanks,
Richard.

> Thanks,
> bin
> 2017-06-07  Bin Cheng  <bin.cheng@arm.com>
>
>     * tree-loop-distribution.c (enum partition_type): New.
>     (struct partition): New field type.
>     (partition_merge_into): Update partition type.
>     (data_dep_in_cycle_p): New function.
>     (build_rdg_partition_for_vertex): Compute partition type.
>     (rdg_build_partitions): Dump partition type.