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

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Jun 23, 2017 at 12:25 PM, Bin.Cheng <amker.cheng@gmail.com> wrote:
> And the patch.
>
> On Fri, Jun 23, 2017 at 11:24 AM, Bin.Cheng <amker.cheng@gmail.com> wrote:
>> On Tue, Jun 20, 2017 at 12:34 PM, Richard Biener
>> <richard.guenther@gmail.com> wrote:
>>> 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.
>> Sorry I have to update this patch because one of my mistake.  I didn't
>> update partition type when fusing them.  For some partition fusion,
>> the update is necessary otherwise we end up with inaccurate type and
>> inaccurate fusion later.  Is it Ok?

Ok.

>> Thanks,
>> bin
>> 2017-06-20  Bin Cheng  <bin.cheng@arm.com>
>>
>>     * tree-loop-distribution.c (enum partition_type): New.
>>     (struct partition): New field type.
>>     (partition_merge_into): Add parameter.  Update partition type.
>>     (data_dep_in_cycle_p, update_type_for_merge): New functions.
>>     (build_rdg_partition_for_vertex): Compute partition type.
>>     (rdg_build_partitions): Dump partition type.
>>     (distribute_loop): Update calls to partition_merge_into.