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Re: New GCC options for loop vectorization


On Fri, Sep 13, 2013 at 6:56 PM, Xinliang David Li <davidxl@google.com> wrote:
> Updated patch implementing the logic that more specific option wins.
>
> Ok for trunk?

@@ -2305,8 +2305,8 @@ omp_max_vf (void)
 {
   if (!optimize
       || optimize_debug
-      || (!flag_tree_vectorize
-  && global_options_set.x_flag_tree_vectorize))
+      || (!flag_tree_loop_vectorize
+  && global_options_set.x_flag_tree_loop_vectorize))
     return 1;

Not sure what is the intent here, but it looks like
-fno-tree-vectorize will no longer disable this.  So it would
need to check (global_options_set.x_flag_tree_vectorize ||
global_options_set.x_flag_tree_loop_vectorize)?  Jakub?

   int vs = targetm.vectorize.autovectorize_vector_sizes ();
@@ -5684,10 +5684,10 @@ expand_omp_simd (struct omp_region *regi
   loop->simduid = OMP_CLAUSE__SIMDUID__DECL (simduid);
   cfun->has_simduid_loops = true;
  }
-      /* If not -fno-tree-vectorize, hint that we want to vectorize
+      /* If not -fno-tree-loop-vectorize, hint that we want to vectorize
  the loop.  */
-      if ((flag_tree_vectorize
-   || !global_options_set.x_flag_tree_vectorize)
+      if ((flag_tree_loop_vectorize
+   || !global_options_set.x_flag_tree_loop_vectorize)
   && loop->safelen > 1)
  {
   loop->force_vect = true;

similar.

-      if (!opts_set->x_flag_tree_vectorize)
- opts->x_flag_tree_vectorize = value;
+      if (!opts_set->x_flag_tree_loop_vectorize)
+ opts->x_flag_tree_loop_vectorize = value;
+      if (!opts_set->x_flag_tree_slp_vectorize)
+ opts->x_flag_tree_slp_vectorize = value;

similar - if I use -fprofile-use -fno-tree-vecotorize you override this choice.
This case should be wrapped in if (!opts_set->x_flag_tree_vectorize)

 @item -ftree-vectorize
 @opindex ftree-vectorize
+Perform vectorization on trees. This flag enables
@option{-ftree-loop-vectorize}
+and @option{-ftree-slp-vectorize} if neither option is explicitly specified.

"if neither option is explicitely specified" doesn't correctly document
-ftree-loop-vectorize -ftree-vectorize behavior, no? (-ftree-slp-vectorize
is still enabled here)

I'm not a native speaker so I cannot suggest a clearer wording here
but maybe just say "if not explicitely specified".

Ok with the -fprofile-use change I suggested and whatever resolution Jakub
suggests and the doc adjustment.

Thanks,
Richard.

> thanks,
>
> David
>
> On Fri, Sep 13, 2013 at 9:48 AM, Xinliang David Li <davidxl@google.com> wrote:
>> Ok -- then my updated patch is wrong then. The implementation in the
>> first version matches the requirement.
>>
>> thanks,
>>
>> David
>>
>>
>> On Fri, Sep 13, 2013 at 9:45 AM, Joseph S. Myers
>> <joseph@codesourcery.com> wrote:
>>> On Fri, 13 Sep 2013, Richard Biener wrote:
>>>
>>>> @@ -1691,6 +1695,12 @@ common_handle_option (struct gcc_options
>>>>          opts->x_flag_ipa_reference = false;
>>>>        break;
>>>>
>>>> +    case OPT_ftree_vectorize:
>>>> +      if (!opts_set->x_flag_tree_loop_vectorize)
>>>> + opts->x_flag_tree_loop_vectorize = value;
>>>> +      if (!opts_set->x_flag_tree_slp_vectorize)
>>>> + opts->x_flag_tree_slp_vectorize = value;
>>>> +      break;
>>>>
>>>> doesn't look obviously correct.  Does that handle
>>>
>>> It looks right to me.  The general principle is that the more specific
>>> option takes precedence over the less specific one, whatever the order on
>>> the command line.
>>>
>>>>   -ftree-vectorize -fno-tree-loop-vectorize -ftree-vectorize
>>>
>>> Should mean -ftree-slp-vectorize.
>>>
>>>>   -ftree-loop-vectorize -fno-tree-vectorize
>>>
>>> Should mean -ftree-loop-vectorize.
>>>
>>>>   -ftree-slp-vectorize -fno-tree-vectorize
>>>
>>> Should mean -ftree-slp-vectorize.
>>>
>>> --
>>> Joseph S. Myers
>>> joseph@codesourcery.com


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