2011-10-18 Tom de Vries <tom@codesourcery.com>

	PR tree-optimization/50672
	* tree-ssa-dce.c (mark_virtual_operand_for_renaming): New function,
	factored out of ...
	(mark_virtual_phi_result_for_renaming): Use
	mark_virtual_operand_for_renaming.
	* tree-flow.h (mark_virtual_operand_for_renaming): Declare.
	* tree-ssa-tail-merge.c (release_last_vdef): New function.
	(purge_bbs): Add update_vops parameter.  Call release_last_vdef for each
	deleted basic block.
	(tail_merge_optimize): Add argument to call to purge_bbs.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@180126 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 41 insertions, 3 deletions

diff --git a/gcc/tree-ssa-tail-merge.c b/gcc/tree-ssa-tail-merge.c
index 611a30f23a4..529388c1b22 100644
--- a/gcc/tree-ssa-tail-merge.c
+++ b/gcc/tree-ssa-tail-merge.c
@@ -773,18 +773,56 @@ same_succ_flush_bbs (bitmap bbs)
     }
 }
 
+/* Release the last vdef in BB, either normal or phi result.  */
+
+static void
+release_last_vdef (basic_block bb)
+{
+  gimple_stmt_iterator i;
+
+  for (i = gsi_last_bb (bb); !gsi_end_p (i); gsi_prev_nondebug (&i))
+    {
+      gimple stmt = gsi_stmt (i);
+      if (gimple_vdef (stmt) == NULL_TREE)
+	continue;
+
+      mark_virtual_operand_for_renaming (gimple_vdef (stmt));
+      return;
+    }
+
+  for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
+    {
+      gimple phi = gsi_stmt (i);
+      tree res = gimple_phi_result (phi);
+
+      if (is_gimple_reg (res))
+	continue;
+
+      mark_virtual_phi_result_for_renaming (phi);
+      return;
+    }
+  
+}
+
 /* Delete all deleted_bbs.  */
 
 static void
-purge_bbs (void)
+purge_bbs (bool update_vops)
 {
   unsigned int i;
   bitmap_iterator bi;
+  basic_block bb;
 
   same_succ_flush_bbs (deleted_bbs);
 
   EXECUTE_IF_SET_IN_BITMAP (deleted_bbs, 0, i, bi)
-    delete_basic_block (BASIC_BLOCK (i));
+    {
+      bb = BASIC_BLOCK (i);
+      if (!update_vops)
+	release_last_vdef (bb);
+
+      delete_basic_block (bb);
+    }
 
   bitmap_and_compl_into (deleted_bb_preds, deleted_bbs);
   bitmap_clear (deleted_bbs);
@@ -1665,7 +1703,7 @@ tail_merge_optimize (unsigned int todo)
 	break;
 
       free_dominance_info (CDI_DOMINATORS);
-      purge_bbs ();
+      purge_bbs (update_vops);
 
       if (iteration_nr == max_iterations)
 	break;