re PR c++/34949 (Dead code in empty destructors.)

PR c++/34949
	* tree-cfg.c (verify_gimple_assign_single): Allow lhs
	of gimple_clobber_p to be MEM_REF.
	* gimplify.c (gimplify_modify_expr): Gimplify *to_p of
	an assignment from TREE_CLOBBER_P.  Allow it to be MEM_REF
	after gimplification.
	* asan.c (get_mem_ref_of_assignment): Don't instrument
	gimple_clobber_p stmts.
	* tree-ssa-dse.c (dse_optimize_stmt): Allow DSE of
	gimple_clobber_p stmt if they have MEM_REF lhs and
	are dead because of another gimple_clobber_p stmt.
	* tree-ssa-live.c (clear_unused_block_pointer): Treat
	gimple_clobber_p stmts like debug stmts.
	(remove_unused_locals): Remove clobbers with MEM_REF lhs
	that refer to unused VAR_DECLs or uninitialized values.
	* tree-sra.c (sra_ipa_reset_debug_stmts): Also remove
	gimple_clobber_p stmts if they refer to removed parameters.
	(get_repl_default_def_ssa_name, sra_ipa_modify_expr): Fix up
	formatting.

From-SVN: r197369

gcc/ChangeLog

@@ -1,3 +1,25 @@
+2013-04-02  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/34949
+	* tree-cfg.c (verify_gimple_assign_single): Allow lhs
+	of gimple_clobber_p to be MEM_REF.
+	* gimplify.c (gimplify_modify_expr): Gimplify *to_p of
+	an assignment from TREE_CLOBBER_P.  Allow it to be MEM_REF
+	after gimplification.
+	* asan.c (get_mem_ref_of_assignment): Don't instrument
+	gimple_clobber_p stmts.
+	* tree-ssa-dse.c (dse_optimize_stmt): Allow DSE of
+	gimple_clobber_p stmt if they have MEM_REF lhs and
+	are dead because of another gimple_clobber_p stmt.
+	* tree-ssa-live.c (clear_unused_block_pointer): Treat
+	gimple_clobber_p stmts like debug stmts.
+	(remove_unused_locals): Remove clobbers with MEM_REF lhs
+	that refer to unused VAR_DECLs or uninitialized values.
+	* tree-sra.c (sra_ipa_reset_debug_stmts): Also remove
+	gimple_clobber_p stmts if they refer to removed parameters.
+	(get_repl_default_def_ssa_name, sra_ipa_modify_expr): Fix up
+	formatting.
+
 2013-04-02  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.md (*testqi_ext_3): Merge with *testqi_ext_3_rex64

gcc/asan.c

@@ -412,7 +412,8 @@ get_mem_ref_of_assignment (const gimple assignment,
 {
   gcc_assert (gimple_assign_single_p (assignment));
 
-  if (gimple_store_p (assignment))
+  if (gimple_store_p (assignment)
+      && !gimple_clobber_p (assignment))
     {
       ref->start = gimple_assign_lhs (assignment);
       *ref_is_store = true;

gcc/gimplify.c

@@ -4840,7 +4840,12 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
      so handle it here.  */
   if (TREE_CLOBBER_P (*from_p))
     {
-      gcc_assert (!want_value && TREE_CODE (*to_p) == VAR_DECL);
+      ret = gimplify_expr (to_p, pre_p, post_p, is_gimple_lvalue, fb_lvalue);
+      if (ret == GS_ERROR)
+	return ret;
+      gcc_assert (!want_value
+		  && (TREE_CODE (*to_p) == VAR_DECL
+		      || TREE_CODE (*to_p) == MEM_REF));
       gimplify_seq_add_stmt (pre_p, gimple_build_assign (*to_p, *from_p));
       *expr_p = NULL;
       return GS_ALL_DONE;

gcc/tree-cfg.c

@@ -3815,9 +3815,9 @@ verify_gimple_assign_single (gimple stmt)
     }
 
   if (gimple_clobber_p (stmt)
-      && !DECL_P (lhs))
+      && !(DECL_P (lhs) || TREE_CODE (lhs) == MEM_REF))
     {
-      error ("non-decl LHS in clobber statement");
+      error ("non-decl/MEM_REF LHS in clobber statement");
       debug_generic_expr (lhs);
       return true;
     }

gcc/tree-sra.c

@@ -2965,8 +2965,8 @@ sra_modify_constructor_assign (gimple *stmt, gimple_stmt_iterator *gsi)
 static tree
 get_repl_default_def_ssa_name (struct access *racc)
 {
-  gcc_checking_assert (!racc->grp_to_be_replaced &&
+  gcc_checking_assert (!racc->grp_to_be_replaced
-		       !racc->grp_to_be_debug_replaced);
+		       && !racc->grp_to_be_debug_replaced);
   if (!racc->replacement_decl)
     racc->replacement_decl = create_access_replacement (racc);
   return get_or_create_ssa_default_def (cfun, racc->replacement_decl);
@@ -4462,8 +4462,8 @@ sra_ipa_modify_expr (tree *expr, bool convert,
     {
       adj = &adjustments[i];
 
-      if (adj->base == base &&
+      if (adj->base == base
-	  (adj->offset == offset || adj->remove_param))
+	  && (adj->offset == offset || adj->remove_param))
 	{
 	  cand = adj;
 	  break;
@@ -4676,6 +4676,14 @@ sra_ipa_reset_debug_stmts (ipa_parm_adjustment_vec adjustments)
       if (name)
 	FOR_EACH_IMM_USE_STMT (stmt, ui, name)
 	  {
+	    if (gimple_clobber_p (stmt))
+	      {
+		gimple_stmt_iterator cgsi = gsi_for_stmt (stmt);
+		unlink_stmt_vdef (stmt);
+		gsi_remove (&cgsi, true);
+		release_defs (stmt);
+		continue;
+	      }
 	    /* All other users must have been removed by
 	       ipa_sra_modify_function_body.  */
 	    gcc_assert (is_gimple_debug (stmt));

gcc/tree-ssa-dse.c

@@ -218,7 +218,10 @@ dse_optimize_stmt (gimple_stmt_iterator *gsi)
   if (is_gimple_call (stmt) && gimple_call_fndecl (stmt))
     return;
 
-  if (gimple_has_volatile_ops (stmt))
+  /* Don't return early on *this_2(D) ={v} {CLOBBER}.  */
+  if (gimple_has_volatile_ops (stmt)
+      && (!gimple_clobber_p (stmt)
+	  || TREE_CODE (gimple_assign_lhs (stmt)) != MEM_REF))
     return;
 
   if (is_gimple_assign (stmt))
@@ -228,6 +231,12 @@ dse_optimize_stmt (gimple_stmt_iterator *gsi)
       if (!dse_possible_dead_store_p (stmt, &use_stmt))
 	return;
 
+      /* But only remove *this_2(D) ={v} {CLOBBER} if killed by
+	 another clobber stmt.  */
+      if (gimple_clobber_p (stmt)
+	  && !gimple_clobber_p (use_stmt))
+	return;
+
       /* If we have precisely one immediate use at this point and the
 	 stores are to the same memory location or there is a chain of
 	 virtual uses from stmt and the stmt which stores to that same

gcc/tree-ssa-live.c

@@ -623,8 +623,8 @@ clear_unused_block_pointer_1 (tree *tp, int *, void *)
   return NULL_TREE;
 }
 
-/* Set all block pointer in debug stmt to NULL if the block is unused,
+/* Set all block pointer in debug or clobber stmt to NULL if the block
-   so that they will not be streamed out.  */
+   is unused, so that they will not be streamed out.  */
 
 static void
 clear_unused_block_pointer (void)
@@ -639,7 +639,7 @@ clear_unused_block_pointer (void)
 	tree b;
 	gimple stmt = gsi_stmt (gsi);
 
-	if (!is_gimple_debug (stmt))
+	if (!is_gimple_debug (stmt) && !gimple_clobber_p (stmt))
 	  continue;
 	b = gimple_block (stmt);
 	if (b && !TREE_USED (b))
@@ -827,7 +827,15 @@ remove_unused_locals (void)
 	    if (gimple_clobber_p (stmt))
 	      {
 		tree lhs = gimple_assign_lhs (stmt);
-		if (TREE_CODE (lhs) == VAR_DECL && !is_used_p (lhs))
+		tree base = get_base_address (lhs);
+		/* Remove clobbers referencing unused vars, or clobbers
+		   with MEM_REF lhs referencing uninitialized pointers.  */
+		if ((TREE_CODE (base) == VAR_DECL && !is_used_p (base))
+		    || (TREE_CODE (lhs) == MEM_REF
+			&& TREE_CODE (TREE_OPERAND (lhs, 0)) == SSA_NAME
+			&& SSA_NAME_IS_DEFAULT_DEF (TREE_OPERAND (lhs, 0))
+			&& (TREE_CODE (SSA_NAME_VAR (TREE_OPERAND (lhs, 0)))
+			    != PARM_DECL)))
 		  {
 		    unlink_stmt_vdef (stmt);
 		    gsi_remove (&gsi, true);