Re: [PATCH GCC][4/4]Better handle store-stores chain if eliminated stores only store loop invariant

["Bin.Cheng" <amker dot cheng at gmail dot com>]

On Tue, Jul 25, 2017 at 12:48 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Mon, Jul 10, 2017 at 10:24 AM, Bin.Cheng <amker.cheng@gmail.com> wrote:
>> On Tue, Jun 27, 2017 at 11:49 AM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>>> Hi,
>>> This is a followup patch better handling below case:
>>>      for (i = 0; i < n; i++)
>>>        {
>>>          a[i] = 1;
>>>          a[i+2] = 2;
>>>        }
>>> Instead of generating root variables by loading from memory and propagating with PHI
>>> nodes, like:
>>>      t0 = a[0];
>>>      t1 = a[1];
>>>      for (i = 0; i < n; i++)
>>>        {
>>>          a[i] = 1;
>>>          t2 = 2;
>>>          t0 = t1;
>>>          t1 = t2;
>>>        }
>>>      a[n] = t0;
>>>      a[n+1] = t1;
>>> We can simply store loop invariant values after loop body if we know loop iterates more
>>> than chain->length times, like:
>>>      for (i = 0; i < n; i++)
>>>        {
>>>          a[i] = 1;
>>>        }
>>>      a[n] = 2;
>>>      a[n+1] = 2;
>>>
>>> Bootstrap(O2/O3) in patch series on x86_64 and AArch64.  Is it OK?
>> Update patch wrto changes in previous patch.
>> Bootstrap and test on x86_64 and AArch64.  Is it OK?
>
> +      if (TREE_CODE (val) == INTEGER_CST || TREE_CODE (val) == REAL_CST)
> +       continue;
>
> Please use CONSTANT_CLASS_P (val) instead.  I suppose VECTOR_CST or
> FIXED_CST would be ok as well for example.
>
> Ok with that change.  Did we eventually optimize this in followup
Patch revised as suggested.  I retested whole patch set and applied as
250665 ~ 250670.  Will keep eyes on possible breakage in next couple
weeks.

Thanks,
bin
> passes previously?
>
> Richard.
>
>> Thanks,
>> bin
>>>
>>> Thanks,
>>> bin
>>> 2017-06-21  Bin Cheng  <bin.cheng@arm.com>
>>>
>>>         * tree-predcom.c: (struct chain): Handle store-store chain in which
>>>         stores for elimination only store loop invariant values.
>>>         (execute_pred_commoning_chain): Ditto.
>>>         (prepare_initializers_chain_store_elim): Ditto.
>>>         (prepare_finalizers): Ditto.
>>>         (is_inv_store_elimination_chain): New function.
>>>         (initialize_root_vars_store_elim_1): New function.