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

1 files changed, 51 insertions, 0 deletions

diff --git a/gcc/tree-ssa-loop-manip.c b/gcc/tree-ssa-loop-manip.c
index a72b779..3fbb456 100644
--- a/gcc/tree-ssa-loop-manip.c
+++ b/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