2014-11-03 Marc Glisse <marc.glisse@inria.fr>

	PR tree-optimization/60770
gcc/
	* tree-into-ssa.c (rewrite_update_stmt): Return whether the
	statement should be removed.
	(maybe_register_def): Likewise. Replace clobbers with default
	definitions.
	(rewrite_dom_walker::before_dom_children): Remove statement if
	rewrite_update_stmt says so.
	* tree-ssa-live.c: Include tree-ssa.h.
	(set_var_live_on_entry): Do not mark undefined variables as live.
	(verify_live_on_entry): Do not check undefined variables.
	* tree-ssa.h (ssa_undefined_value_p): New parameter for the case
	of partially undefined variables.
	* tree-ssa.c (ssa_undefined_value_p): Likewise.
	(execute_update_addresses_taken): Do not drop clobbers.

gcc/testsuite/
	* gcc.dg/tree-ssa/pr60770-1.c: New file.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@217034 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 30 insertions, 12 deletions

diff --git a/gcc/tree-into-ssa.c b/gcc/tree-into-ssa.c
index bf99160deea..d86efe47504 100644
--- a/gcc/tree-into-ssa.c
+++ b/gcc/tree-into-ssa.c
@@ -1833,14 +1833,15 @@ maybe_replace_use_in_debug_stmt (use_operand_p use_p)
 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
    or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
    register it as the current definition for the names replaced by
-   DEF_P.  */
+   DEF_P.  Returns whether the statement should be removed.  */
 
-static inline void
+static inline bool
 maybe_register_def (def_operand_p def_p, gimple stmt,
 		    gimple_stmt_iterator gsi)
 {
   tree def = DEF_FROM_PTR (def_p);
   tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
+  bool to_delete = false;
 
   /* If DEF is a naked symbol that needs renaming, create a new
      name for it.  */
@@ -1848,12 +1849,21 @@ maybe_register_def (def_operand_p def_p, gimple stmt,
     {
       if (DECL_P (def))
 	{
-	  tree tracked_var;
-
-	  def = make_ssa_name (def, stmt);
+	  if (gimple_clobber_p (stmt) && is_gimple_reg (sym))
+	    {
+	      gcc_checking_assert (TREE_CODE (sym) == VAR_DECL);
+	      /* Replace clobber stmts with a default def. This new use of a
+		 default definition may make it look like SSA_NAMEs have
+		 conflicting lifetimes, so we need special code to let them
+		 coalesce properly.  */
+	      to_delete = true;
+	      def = get_or_create_ssa_default_def (cfun, sym);
+	    }
+	  else
+	    def = make_ssa_name (def, stmt);
 	  SET_DEF (def_p, def);
 
-	  tracked_var = target_for_debug_bind (sym);
+	  tree tracked_var = target_for_debug_bind (sym);
 	  if (tracked_var)
 	    {
 	      gimple note = gimple_build_debug_bind (tracked_var, def, stmt);
@@ -1911,6 +1921,8 @@ maybe_register_def (def_operand_p def_p, gimple stmt,
       if (is_old_name (def))
 	register_new_update_single (def, def);
     }
+
+  return to_delete;
 }
 
 
@@ -1919,9 +1931,9 @@ maybe_register_def (def_operand_p def_p, gimple stmt,
    OLD_SSA_NAMES used by SI will be updated to their current reaching
    definition.  Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
    will be registered as a new definition for their corresponding name
-   in OLD_SSA_NAMES.  */
+   in OLD_SSA_NAMES.  Returns whether STMT should be removed.  */
 
-static void
+static bool
 rewrite_update_stmt (gimple stmt, gimple_stmt_iterator gsi)
 {
   use_operand_p use_p;
@@ -1930,7 +1942,7 @@ rewrite_update_stmt (gimple stmt, gimple_stmt_iterator gsi)
 
   /* Only update marked statements.  */
   if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
-    return;
+    return false;
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     {
@@ -1981,9 +1993,12 @@ rewrite_update_stmt (gimple stmt, gimple_stmt_iterator gsi)
   /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
      Also register definitions for names whose underlying symbol is
      marked for renaming.  */
+  bool to_delete = false;
   if (register_defs_p (stmt))
     FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
-      maybe_register_def (def_p, stmt, gsi);
+      to_delete |= maybe_register_def (def_p, stmt, gsi);
+
+  return to_delete;
 }
 
 
@@ -2149,8 +2164,11 @@ rewrite_update_dom_walker::before_dom_children (basic_block bb)
   if (bitmap_bit_p (interesting_blocks, bb->index))
     {
       gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
-      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
-        rewrite_update_stmt (gsi_stmt (gsi), gsi);
+      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
+	if (rewrite_update_stmt (gsi_stmt (gsi), gsi))
+	  gsi_remove (&gsi, true);
+	else
+	  gsi_next (&gsi);
     }
 
   /* Step 3.  Update PHI nodes.  */