Avoid recomputing data references in BB SLP

If the first attempt at applying BB SLP to a region fails, the main loop
in vect_slp_bb recomputes the region's bounds and datarefs for the next
vector size.  AFAICT this isn't needed any more; we should be able
to reuse the datarefs from the first attempt instead.

2019-10-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-slp.c (vect_slp_analyze_bb_1): Call save_datarefs
	when processing the given datarefs for the first time and
	check_datarefs subsequently.
	(vect_slp_bb_region): New function, split out of...
	(vect_slp_bb): ...here.  Don't recompute the region bounds and
	dataref sets when retrying with a different vector size.

From-SVN: r277210

gcc/ChangeLog

+2019-10-20  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* tree-vect-slp.c (vect_slp_analyze_bb_1): Call save_datarefs
+	when processing the given datarefs for the first time and
+	check_datarefs subsequently.
+	(vect_slp_bb_region): New function, split out of...
+	(vect_slp_bb): ...here.  Don't recompute the region bounds and
+	dataref sets when retrying with a different vector size.
+
 2019-10-19  Jakub Jelinek  <jakub@redhat.com>
 	    Uroš Bizjak  <ubizjak@gmail.com>
 

gcc/tree-vect-slp.c

@@ -2852,6 +2852,7 @@ vect_slp_analyze_bb_1 (gimple_stmt_iterator region_begin,
   slp_instance instance;
   int i;
   poly_uint64 min_vf = 2;
+  bool first_time_p = shared->datarefs.is_empty ();
 
   /* The first group of checks is independent of the vector size.  */
   fatal = true;
@@ -2871,7 +2872,10 @@ vect_slp_analyze_bb_1 (gimple_stmt_iterator region_begin,
     return NULL;
 
   BB_VINFO_DATAREFS (bb_vinfo) = datarefs;
-  bb_vinfo->shared->save_datarefs ();
+  if (first_time_p)
+    bb_vinfo->shared->save_datarefs ();
+  else
+    bb_vinfo->shared->check_datarefs ();
 
   /* Analyze the data references.  */
 
@@ -3007,16 +3011,18 @@ vect_slp_analyze_bb_1 (gimple_stmt_iterator region_begin,
   return bb_vinfo;
 }
 
+/* Subroutine of vect_slp_bb.  Try to vectorize the statements between
+   REGION_BEGIN (inclusive) and REGION_END (exclusive), returning true
+   on success.  The region has N_STMTS statements and has the datarefs
+   given by DATAREFS.  */
 
-/* Main entry for the BB vectorizer.  Analyze and transform BB, returns
-   true if anything in the basic-block was vectorized.  */
-
-bool
-vect_slp_bb (basic_block bb)
+static bool
+vect_slp_bb_region (gimple_stmt_iterator region_begin,
+		    gimple_stmt_iterator region_end,
+		    vec<data_reference_p> datarefs,
+		    unsigned int n_stmts)
 {
   bb_vec_info bb_vinfo;
-  gimple_stmt_iterator gsi;
-  bool any_vectorized = false;
   auto_vector_sizes vector_sizes;
 
   /* Autodetect first vector size we try.  */
@@ -3024,46 +3030,15 @@ vect_slp_bb (basic_block bb)
   targetm.vectorize.autovectorize_vector_sizes (&vector_sizes, false);
   unsigned int next_size = 0;
 
-  gsi = gsi_start_bb (bb);
+  vec_info_shared shared;
 
   poly_uint64 autodetected_vector_size = 0;
   while (1)
     {
-      if (gsi_end_p (gsi))
-	break;
-
-      gimple_stmt_iterator region_begin = gsi;
-      vec<data_reference_p> datarefs = vNULL;
-      int insns = 0;
-
-      for (; !gsi_end_p (gsi); gsi_next (&gsi))
-	{
-	  gimple *stmt = gsi_stmt (gsi);
-	  if (is_gimple_debug (stmt))
-	    continue;
-	  insns++;
-
-	  if (gimple_location (stmt) != UNKNOWN_LOCATION)
-	    vect_location = stmt;
-
-	  if (!vect_find_stmt_data_reference (NULL, stmt, &datarefs))
-	    break;
-	}
-
-      /* Skip leading unhandled stmts.  */
-      if (gsi_stmt (region_begin) == gsi_stmt (gsi))
-	{
-	  gsi_next (&gsi);
-	  continue;
-	}
-
-      gimple_stmt_iterator region_end = gsi;
-
       bool vectorized = false;
       bool fatal = false;
-      vec_info_shared shared;
       bb_vinfo = vect_slp_analyze_bb_1 (region_begin, region_end,
-					datarefs, insns, fatal, &shared);
+					datarefs, n_stmts, fatal, &shared);
       if (bb_vinfo
 	  && dbg_cnt (vect_slp))
 	{
@@ -3090,8 +3065,6 @@ vect_slp_bb (basic_block bb)
 	}
       delete bb_vinfo;
 
-      any_vectorized |= vectorized;
-
       if (next_size == 0)
 	autodetected_vector_size = current_vector_size;
 
@@ -3105,33 +3078,68 @@ vect_slp_bb (basic_block bb)
 	  /* If vect_slp_analyze_bb_1 signaled that analysis for all
 	     vector sizes will fail do not bother iterating.  */
 	  || fatal)
+	return vectorized;
+
+      /* Try the next biggest vector size.  */
+      current_vector_size = vector_sizes[next_size++];
+      if (dump_enabled_p ())
 	{
-	  if (gsi_end_p (region_end))
-	    break;
+	  dump_printf_loc (MSG_NOTE, vect_location,
+			   "***** Re-trying analysis with "
+			   "vector size ");
+	  dump_dec (MSG_NOTE, current_vector_size);
+	  dump_printf (MSG_NOTE, "\n");
+	}
+    }
+}
 
-	  /* Skip the unhandled stmt.  */
-	  gsi_next (&gsi);
+/* Main entry for the BB vectorizer.  Analyze and transform BB, returns
+   true if anything in the basic-block was vectorized.  */
 
-	  /* And reset vector sizes.  */
-	  current_vector_size = 0;
-	  next_size = 0;
-	}
-      else
+bool
+vect_slp_bb (basic_block bb)
+{
+  gimple_stmt_iterator gsi;
+  bool any_vectorized = false;
+
+  gsi = gsi_start_bb (bb);
+  while (!gsi_end_p (gsi))
+    {
+      gimple_stmt_iterator region_begin = gsi;
+      vec<data_reference_p> datarefs = vNULL;
+      int insns = 0;
+
+      for (; !gsi_end_p (gsi); gsi_next (&gsi))
 	{
-	  /* Try the next biggest vector size.  */
-	  current_vector_size = vector_sizes[next_size++];
-	  if (dump_enabled_p ())
-	    {
-	      dump_printf_loc (MSG_NOTE, vect_location,
-			       "***** Re-trying analysis with "
-			       "vector size ");
-	      dump_dec (MSG_NOTE, current_vector_size);
-	      dump_printf (MSG_NOTE, "\n");
-	    }
+	  gimple *stmt = gsi_stmt (gsi);
+	  if (is_gimple_debug (stmt))
+	    continue;
+	  insns++;
+
+	  if (gimple_location (stmt) != UNKNOWN_LOCATION)
+	    vect_location = stmt;
+
+	  if (!vect_find_stmt_data_reference (NULL, stmt, &datarefs))
+	    break;
+	}
 
-	  /* Start over.  */
-	  gsi = region_begin;
+      /* Skip leading unhandled stmts.  */
+      if (gsi_stmt (region_begin) == gsi_stmt (gsi))
+	{
+	  gsi_next (&gsi);
+	  continue;
 	}
+
+      gimple_stmt_iterator region_end = gsi;
+
+      if (vect_slp_bb_region (region_begin, region_end, datarefs, insns))
+	any_vectorized = true;
+
+      if (gsi_end_p (region_end))
+	break;
+
+      /* Skip the unhandled stmt.  */
+      gsi_next (&gsi);
     }
 
   return any_vectorized;