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Re: [PATCH GCC8][31/33]Set range information for niter bound of vectorized loop


On Fri, May 19, 2017 at 1:51 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Mon, May 15, 2017 at 5:58 PM, Bin.Cheng <amker.cheng@gmail.com> wrote:
>> On Thu, May 11, 2017 at 12:02 PM, Richard Biener
>> <richard.guenther@gmail.com> wrote:
>>> On Tue, Apr 18, 2017 at 12:54 PM, Bin Cheng <Bin.Cheng@arm.com> wrote
>>>> Hi,
>>>> Based on vect_peeling algorithm, we know for sure that vectorized loop must iterates at least once.
>>>> This patch sets range information for niter bounds of vectorized loop.  This helps niter analysis,
>>>> so iv elimination too.
>>>> Is it OK?
>>>
>>>        niters_vector = force_gimple_operand (niters_vector, &stmts, true, var);
>>>        gsi_insert_seq_on_edge_immediate (pe, stmts);
>>> +      /* Peeling algorithm guarantees that vector loop bound is at least ONE,
>>> +        we set range information to make niters analyzer's life easier.  */
>>> +      if (TREE_CODE (niters_vector) == SSA_NAME)
>>> +       set_range_info (niters_vector, VR_RANGE, build_int_cst (type, 1),
>>> +                       fold_build2 (RSHIFT_EXPR, type,
>>> +                                    TYPE_MAX_VALUE (type), log_vf));
>>>
>>> if all of niters_vector folds to an original SSA name then
>>> niters_vector after gimplification
>>> is not a new SSA name and thus you can't set range-info on it.
>>>
>>> Likewise for the other case where LOOP_VINFO_NITERS is just an SSA name.
>> Hi,
>> This is updated patch.  It checks whether the result ssa name is newly
>> created tmp and only sets range information if so.
>>
>> Is it OK?
>
> A better way to check whether the SSA name is new is to see if 'stmts'
> filled by force_gimple_operand is non-empty.
Hi,
Here is updated patch checking empty gimple_seq.  Is it OK?

Thanks,
bin
>
> Richard.
>
>> Thanks,
>> bin
>>
>> 2017-04-11  Bin Cheng  <bin.cheng@arm.com>
>>
>>     * tree-vectorizer.h (vect_build_loop_niters): New parameter.
>>     * tree-vect-loop-manip.c (vect_build_loop_niters): New parameter.
>>     Set true to new parameter if new ssa variable is defined.
>>     (vect_gen_vector_loop_niters): Refactor.  Set range information
>>     for the new vector loop bound variable.
>>     (vect_do_peeling): Ditto.
>>
>>>
>>> Richard.
>>>
>>>> Thanks,
>>>> bin
>>>> 2017-04-11  Bin Cheng  <bin.cheng@arm.com>
>>>>
>>>>         * tree-vect-loop-manip.c (vect_gen_vector_loop_niters): Refactor.
>>>>         Set range information for vector loop bound variable.
>>>>         (vect_do_peeling): Ditto.
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index f48336b..93c1542 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -1095,10 +1095,11 @@ vect_update_inits_of_drs (loop_vec_info loop_vinfo, tree niters)
 
 
 /* This function builds ni_name = number of iterations.  Statements
-   are emitted on the loop preheader edge.  */
+   are emitted on the loop preheader edge.  If NEW_VAR_P is not NULL, set
+   it to TRUE if new ssa_var is generated.  */
 
 tree
-vect_build_loop_niters (loop_vec_info loop_vinfo)
+vect_build_loop_niters (loop_vec_info loop_vinfo, bool *new_var_p)
 {
   tree ni = unshare_expr (LOOP_VINFO_NITERS (loop_vinfo));
   if (TREE_CODE (ni) == INTEGER_CST)
@@ -1112,7 +1113,11 @@ vect_build_loop_niters (loop_vec_info loop_vinfo)
       var = create_tmp_var (TREE_TYPE (ni), "niters");
       ni_name = force_gimple_operand (ni, &stmts, false, var);
       if (stmts)
-	gsi_insert_seq_on_edge_immediate (pe, stmts);
+	{
+	  gsi_insert_seq_on_edge_immediate (pe, stmts);
+	  if (new_var_p != NULL)
+	    *new_var_p = true;
+	}
 
       return ni_name;
     }
@@ -1177,22 +1182,21 @@ vect_gen_vector_loop_niters (loop_vec_info loop_vinfo, tree niters,
 			     tree *niters_vector_ptr, bool niters_no_overflow)
 {
   tree ni_minus_gap, var;
-  tree niters_vector;
+  tree niters_vector, type = TREE_TYPE (niters);
   int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
   edge pe = loop_preheader_edge (LOOP_VINFO_LOOP (loop_vinfo));
-  tree log_vf = build_int_cst (TREE_TYPE (niters), exact_log2 (vf));
+  tree log_vf = build_int_cst (type, exact_log2 (vf));
 
   /* If epilogue loop is required because of data accesses with gaps, we
      subtract one iteration from the total number of iterations here for
      correct calculation of RATIO.  */
   if (LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo))
     {
-      ni_minus_gap = fold_build2 (MINUS_EXPR, TREE_TYPE (niters),
-				  niters,
-				  build_one_cst (TREE_TYPE (niters)));
+      ni_minus_gap = fold_build2 (MINUS_EXPR, type, niters,
+				  build_one_cst (type));
       if (!is_gimple_val (ni_minus_gap))
 	{
-	  var = create_tmp_var (TREE_TYPE (niters), "ni_gap");
+	  var = create_tmp_var (type, "ni_gap");
 	  gimple *stmts = NULL;
 	  ni_minus_gap = force_gimple_operand (ni_minus_gap, &stmts,
 					       true, var);
@@ -1208,25 +1212,28 @@ vect_gen_vector_loop_niters (loop_vec_info loop_vinfo, tree niters,
      (niters - vf) >> log2(vf) + 1 by using the fact that we know ratio
      will be at least one.  */
   if (niters_no_overflow)
-    niters_vector = fold_build2 (RSHIFT_EXPR, TREE_TYPE (niters),
-				 ni_minus_gap, log_vf);
+    niters_vector = fold_build2 (RSHIFT_EXPR, type, ni_minus_gap, log_vf);
   else
     niters_vector
-      = fold_build2 (PLUS_EXPR, TREE_TYPE (niters),
-		     fold_build2 (RSHIFT_EXPR, TREE_TYPE (niters),
-				  fold_build2 (MINUS_EXPR, TREE_TYPE (niters),
-					       ni_minus_gap,
-					       build_int_cst
-						 (TREE_TYPE (niters), vf)),
+      = fold_build2 (PLUS_EXPR, type,
+		     fold_build2 (RSHIFT_EXPR, type,
+				  fold_build2 (MINUS_EXPR, type, ni_minus_gap,
+					       build_int_cst (type, vf)),
 				  log_vf),
-		     build_int_cst (TREE_TYPE (niters), 1));
+		     build_int_cst (type, 1));
 
   if (!is_gimple_val (niters_vector))
     {
-      var = create_tmp_var (TREE_TYPE (niters), "bnd");
-      gimple *stmts = NULL;
+      var = create_tmp_var (type, "bnd");
+      gimple_seq stmts = NULL;
       niters_vector = force_gimple_operand (niters_vector, &stmts, true, var);
       gsi_insert_seq_on_edge_immediate (pe, stmts);
+      /* Peeling algorithm guarantees that vector loop bound is at least ONE,
+	 we set range information to make niters analyzer's life easier.  */
+      if (stmts != NULL)
+	set_range_info (niters_vector, VR_RANGE, build_int_cst (type, 1),
+			fold_build2 (RSHIFT_EXPR, type,
+				     TYPE_MAX_VALUE (type), log_vf));
     }
   *niters_vector_ptr = niters_vector;
 
@@ -1771,7 +1778,13 @@ vect_do_peeling (loop_vec_info loop_vinfo, tree niters, tree nitersm1,
       LOOP_VINFO_NITERSM1 (loop_vinfo)
 	= fold_build2 (MINUS_EXPR, type,
 		       LOOP_VINFO_NITERSM1 (loop_vinfo), niters_prolog);
-      niters = vect_build_loop_niters (loop_vinfo);
+      bool new_var_p = false;
+      niters = vect_build_loop_niters (loop_vinfo, &new_var_p);
+      /* It's guaranteed that vector loop bound before vectorization is at
+	 least VF, so set range information for newly generated var.  */
+      if (new_var_p)
+	set_range_info (niters, VR_RANGE,
+			build_int_cst (type, vf), TYPE_MAX_VALUE (type));
 
       /* Prolog iterates at most bound_prolog times, latch iterates at
 	 most bound_prolog - 1 times.  */
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 12bb904..f72a1d5 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -1168,7 +1168,7 @@ extern gimple *vect_force_simple_reduction (loop_vec_info, gimple *, bool,
 					    bool *, bool);
 /* Drive for loop analysis stage.  */
 extern loop_vec_info vect_analyze_loop (struct loop *, loop_vec_info);
-extern tree vect_build_loop_niters (loop_vec_info);
+extern tree vect_build_loop_niters (loop_vec_info, bool * = NULL);
 extern void vect_gen_vector_loop_niters (loop_vec_info, tree, tree *, bool);
 /* Drive for loop transformation stage.  */
 extern struct loop *vect_transform_loop (loop_vec_info);

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