[1/n] PR85694: Allow pattern definition statements to be reused

This patch is the first part of a series to fix to PR85694.
Later patches can make the pattern for a statement S2 reuse the
results of a PATTERN_DEF_SEQ statement attached to an earlier
statement S1.  Although vect_mark_stmts_to_be_vectorized handled
this fine, vect_analyze_stmt and vect_transform_loop both skipped the
PATTERN_DEF_SEQ for S1 if S1's main pattern wasn't live or relevant.

I couldn't wrap my head around the flow in vect_transform_loop,
so ended up moving the per-statement handling into a subroutine.
That makes the patch look bigger than it actually is.

2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-stmts.c (vect_analyze_stmt): Move the handling of pattern
	definition statements before the early exit for statements that aren't
	live or relevant.
	* tree-vect-loop.c (vect_transform_loop_stmt): New function,
	split out from...
	(vect_transform_loop): ...here.  Process pattern definition
	statements without first checking whether the main pattern
	statement is live or relevant.

From-SVN: r261784

gcc/ChangeLog

+2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* tree-vect-stmts.c (vect_analyze_stmt): Move the handling of pattern
+	definition statements before the early exit for statements that aren't
+	live or relevant.
+	* tree-vect-loop.c (vect_transform_loop_stmt): New function,
+	split out from...
+	(vect_transform_loop): ...here.  Process pattern definition
+	statements without first checking whether the main pattern
+	statement is live or relevant.
+
 2018-06-19  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* tree-cfgcleanup.c (tree_forwarder_block_p): Do not return false at

gcc/tree-vect-stmts.c

@@ -9393,6 +9393,34 @@ vect_analyze_stmt (gimple *stmt, bool *need_to_vectorize, slp_tree node,
       return false;
     }
 
+  if (STMT_VINFO_IN_PATTERN_P (stmt_info)
+      && node == NULL
+      && (pattern_def_seq = STMT_VINFO_PATTERN_DEF_SEQ (stmt_info)))
+    {
+      gimple_stmt_iterator si;
+
+      for (si = gsi_start (pattern_def_seq); !gsi_end_p (si); gsi_next (&si))
+	{
+	  gimple *pattern_def_stmt = gsi_stmt (si);
+	  if (STMT_VINFO_RELEVANT_P (vinfo_for_stmt (pattern_def_stmt))
+	      || STMT_VINFO_LIVE_P (vinfo_for_stmt (pattern_def_stmt)))
+	    {
+	      /* Analyze def stmt of STMT if it's a pattern stmt.  */
+	      if (dump_enabled_p ())
+		{
+		  dump_printf_loc (MSG_NOTE, vect_location,
+				   "==> examining pattern def statement: ");
+		  dump_gimple_stmt (MSG_NOTE, TDF_SLIM, pattern_def_stmt, 0);
+		}
+
+	      if (!vect_analyze_stmt (pattern_def_stmt,
+				      need_to_vectorize, node, node_instance,
+				      cost_vec))
+		return false;
+	    }
+	}
+    }
+
   /* Skip stmts that do not need to be vectorized. In loops this is expected
      to include:
      - the COND_EXPR which is the loop exit condition
@@ -9453,34 +9481,6 @@ vect_analyze_stmt (gimple *stmt, bool *need_to_vectorize, slp_tree node,
         return false;
    }
 
-  if (is_pattern_stmt_p (stmt_info)
-      && node == NULL
-      && (pattern_def_seq = STMT_VINFO_PATTERN_DEF_SEQ (stmt_info)))
-    {
-      gimple_stmt_iterator si;
-
-      for (si = gsi_start (pattern_def_seq); !gsi_end_p (si); gsi_next (&si))
-	{
-	  gimple *pattern_def_stmt = gsi_stmt (si);
-	  if (STMT_VINFO_RELEVANT_P (vinfo_for_stmt (pattern_def_stmt))
-	      || STMT_VINFO_LIVE_P (vinfo_for_stmt (pattern_def_stmt)))
-	    {
-	      /* Analyze def stmt of STMT if it's a pattern stmt.  */
-	      if (dump_enabled_p ())
-		{
-		  dump_printf_loc (MSG_NOTE, vect_location,
-                                   "==> examining pattern def statement: ");
-		  dump_gimple_stmt (MSG_NOTE, TDF_SLIM, pattern_def_stmt, 0);
-		}
-
-	      if (!vect_analyze_stmt (pattern_def_stmt,
-				      need_to_vectorize, node, node_instance,
-				      cost_vec))
-		return false;
-	    }
-	}
-    }
-
   switch (STMT_VINFO_DEF_TYPE (stmt_info))
     {
       case vect_internal_def: