Add rewrite_virtuals_into_loop_closed_ssa

2015-07-07  Tom de Vries  <tom@codesourcery.com>

	* tree-cfg.c (get_virtual_phi): New function.
	* tree-cfg.h (get_virtual_phi): Declare.
	* tree-ssa-loop-manip.c (replace_uses_in_dominated_bbs)
	(rewrite_virtuals_into_loop_closed_ssa): New function.
	* tree-ssa-loop-manip.h (rewrite_virtuals_into_loop_closed_ssa):
	Declare.
	* tree-parloops.c (replace_uses_in_bbs_by): Remove.
	(transform_to_exit_first_loop_alt): Use
	rewrite_virtuals_into_loop_closed_ssa.

From-SVN: r225520

gcc/ChangeLog

+2015-07-07  Tom de Vries  <tom@codesourcery.com>
+
+	* tree-cfg.c (get_virtual_phi): New function.
+	* tree-cfg.h (get_virtual_phi): Declare.
+	* tree-ssa-loop-manip.c (replace_uses_in_dominated_bbs)
+	(rewrite_virtuals_into_loop_closed_ssa): New function.
+	* tree-ssa-loop-manip.h (rewrite_virtuals_into_loop_closed_ssa):
+	Declare.
+	* tree-parloops.c (replace_uses_in_bbs_by): Remove.
+	(transform_to_exit_first_loop_alt): Use
+	rewrite_virtuals_into_loop_closed_ssa.
+
 2015-07-07  Richard Biener  <rguenther@suse.de>
 
 	* fold-const.c (fold_binary_loc): Move

gcc/tree-cfg.c

@@ -2623,6 +2623,23 @@ delete_tree_cfg_annotations (void)
   vec_free (label_to_block_map_for_fn (cfun));
 }
 
+/* Return the virtual phi in BB.  */
+
+gphi *
+get_virtual_phi (basic_block bb)
+{
+  for (gphi_iterator gsi = gsi_start_phis (bb);
+       !gsi_end_p (gsi);
+       gsi_next (&gsi))
+    {
+      gphi *phi = gsi.phi ();
+
+      if (virtual_operand_p (PHI_RESULT (phi)))
+	return phi;
+    }
+
+  return NULL;
+}
 
 /* Return the first statement in basic block BB.  */
 

gcc/tree-cfg.h

@@ -59,6 +59,7 @@ extern bool simple_goto_p (gimple);
 extern bool stmt_ends_bb_p (gimple);
 extern bool assert_unreachable_fallthru_edge_p (edge);
 extern void delete_tree_cfg_annotations (void);
+extern gphi *get_virtual_phi (basic_block);
 extern gimple first_stmt (basic_block);
 extern gimple last_stmt (basic_block);
 extern gimple last_and_only_stmt (basic_block);

gcc/tree-parloops.c

@@ -1492,25 +1492,6 @@ replace_uses_in_bb_by (tree name, tree val, basic_block bb)
     }
 }
 
-/* Replace uses of NAME by VAL in blocks BBS.  */
-
-static void
-replace_uses_in_bbs_by (tree name, tree val, bitmap bbs)
-{
-  gimple use_stmt;
-  imm_use_iterator imm_iter;
-
-  FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, name)
-    {
-      if (!bitmap_bit_p (bbs, gimple_bb (use_stmt)->index))
-	continue;
-
-      use_operand_p use_p;
-      FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
-	SET_USE (use_p, val);
-    }
-}
-
 /* Do transformation from:
 
      <bb preheader>:
@@ -1631,18 +1612,11 @@ transform_to_exit_first_loop_alt (struct loop *loop,
   tree control = gimple_cond_lhs (cond_stmt);
   edge e;
 
-  /* Gather the bbs dominated by the exit block.  */
-  bitmap exit_dominated = BITMAP_ALLOC (NULL);
-  bitmap_set_bit (exit_dominated, exit_block->index);
-  vec<basic_block> exit_dominated_vec
-    = get_dominated_by (CDI_DOMINATORS, exit_block);
-
-  int i;
-  basic_block dom_bb;
-  FOR_EACH_VEC_ELT (exit_dominated_vec, i, dom_bb)
-    bitmap_set_bit (exit_dominated, dom_bb->index);
-
-  exit_dominated_vec.release ();
+  /* Rewriting virtuals into loop-closed ssa normal form makes this
+     transformation simpler.  It also ensures that the virtuals are in
+     loop-closed ssa normal from after the transformation, which is required by
+     create_parallel_loop.  */
+  rewrite_virtuals_into_loop_closed_ssa (loop);
 
   /* Create the new_header block.  */
   basic_block new_header = split_block_before_cond_jump (exit->src);
@@ -1675,6 +1649,7 @@ transform_to_exit_first_loop_alt (struct loop *loop,
   vec<edge_var_map> *v = redirect_edge_var_map_vector (post_inc_edge);
   edge_var_map *vm;
   gphi_iterator gsi;
+  int i;
   for (gsi = gsi_start_phis (header), i = 0;
        !gsi_end_p (gsi) && v->iterate (i, &vm);
        gsi_next (&gsi), i++)
@@ -1692,10 +1667,9 @@ transform_to_exit_first_loop_alt (struct loop *loop,
       /* Replace ivtmp/sum_b with ivtmp/sum_c in header phi.  */
       add_phi_arg (phi, res_c, post_cond_edge, UNKNOWN_LOCATION);
 
-      /* Replace sum_b with sum_c in exit phi.  Loop-closed ssa does not hold
-	 for virtuals, so we cannot get away with exit_block only.  */
+      /* Replace sum_b with sum_c in exit phi.  */
       tree res_b = redirect_edge_var_map_def (vm);
-      replace_uses_in_bbs_by (res_b, res_c, exit_dominated);
+      replace_uses_in_bb_by (res_b, res_c, exit_block);
 
       struct reduction_info *red = reduction_phi (reduction_list, phi);
       gcc_assert (virtual_operand_p (res_a)
@@ -1710,7 +1684,6 @@ transform_to_exit_first_loop_alt (struct loop *loop,
 	}
     }
   gcc_assert (gsi_end_p (gsi) && !v->iterate (i, &vm));
-  BITMAP_FREE (exit_dominated);
 
   /* Set the preheader argument of the new phis to ivtmp/sum_init.  */
   flush_pending_stmts (entry);

gcc/tree-ssa-loop-manip.c

@@ -560,6 +560,57 @@ rewrite_into_loop_closed_ssa (bitmap changed_bbs, unsigned update_flag)
   free (use_blocks);
 }
 
+/* Replace uses of OLD_VAL with NEW_VAL in bbs dominated by BB.  */
+
+static void
+replace_uses_in_dominated_bbs (tree old_val, tree new_val, basic_block bb)
+{
+  gimple use_stmt;
+  imm_use_iterator imm_iter;
+
+  FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, old_val)
+    {
+      if (!dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb))
+	  continue;
+
+      use_operand_p use_p;
+      FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
+	SET_USE (use_p, new_val);
+    }
+}
+
+/* Ensure a virtual phi is present in the exit block, if LOOP contains a vdef.
+   In other words, ensure loop-closed ssa normal form for virtuals.  Handles
+   only loops with a single exit that dominates the latch.  */
+
+void
+rewrite_virtuals_into_loop_closed_ssa (struct loop *loop)
+{
+  gphi *phi;
+  /* TODO: Handle !single_dom_exit loops.  */
+  edge exit = single_dom_exit (loop);
+  gcc_assert (exit != NULL);
+
+  phi = get_virtual_phi (loop->header);
+  if (phi == NULL)
+    return;
+
+  tree final_loop = PHI_ARG_DEF_FROM_EDGE (phi, single_succ_edge (loop->latch));
+
+  phi = get_virtual_phi (exit->dest);
+  if (phi != NULL)
+    {
+      tree final_exit = PHI_ARG_DEF_FROM_EDGE (phi, exit);
+      gcc_assert (operand_equal_p (final_loop, final_exit, 0));
+      return;
+    }
+
+  tree res_new = copy_ssa_name (final_loop, NULL);
+  gphi *nphi = create_phi_node (res_new, exit->dest);
+  replace_uses_in_dominated_bbs (final_loop, res_new, exit->dest);
+  add_phi_arg (nphi, final_loop, exit, UNKNOWN_LOCATION);
+}
+
 /* Check invariants of the loop closed ssa form for the USE in BB.  */
 
 static void

gcc/tree-ssa-loop-manip.h

@@ -25,6 +25,7 @@ typedef void (*transform_callback)(struct loop *, void *);
 extern void create_iv (tree, tree, tree, struct loop *, gimple_stmt_iterator *,
 		       bool, tree *, tree *);
 extern void rewrite_into_loop_closed_ssa (bitmap, unsigned);
+extern void rewrite_virtuals_into_loop_closed_ssa (struct loop *);
 extern void verify_loop_closed_ssa (bool);
 extern basic_block split_loop_exit_edge (edge);
 extern basic_block ip_end_pos (struct loop *);