re PR middle-end/38851 (Compiler warns about uninitialized variable that is an…

re PR middle-end/38851 (Compiler warns about uninitialized variable that is an object with a constructor)

2009-01-26  Richard Guenther  <rguenther@suse.de>

	PR middle-end/38851
	* Makefile.in (tree-ssa-dse.o): Add langhooks.h.
	* tree-ssa-dse.c: Include langhooks.h
	(execute_simple_dse): Remove stores with zero size.

	* g++.dg/warn/Wuninitialized-1.C: New testcase.

From-SVN: r143672

gcc/ChangeLog

+2009-01-26  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/38851
+	* Makefile.in (tree-ssa-dse.o): Add langhooks.h.
+	* tree-ssa-dse.c: Include langhooks.h
+	(execute_simple_dse): Remove stores with zero size.
+
 2009-01-24  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/38957

gcc/Makefile.in

@@ -2110,7 +2110,7 @@ tree-outof-ssa.o : tree-outof-ssa.c $(TREE_FLOW_H) $(CONFIG_H) $(SYSTEM_H) \
 tree-ssa-dse.o : tree-ssa-dse.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
    $(TM_H) $(GGC_H) $(TREE_H) $(RTL_H) $(TM_P_H) $(BASIC_BLOCK_H) \
    $(TREE_FLOW_H) tree-pass.h $(TREE_DUMP_H) domwalk.h $(FLAGS_H) \
-   $(DIAGNOSTIC_H) $(TIMEVAR_H)
+   $(DIAGNOSTIC_H) $(TIMEVAR_H) langhooks.h
 tree-ssa-forwprop.o : tree-ssa-forwprop.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
    $(TM_H) $(GGC_H) $(TREE_H) $(RTL_H) $(TM_P_H) $(BASIC_BLOCK_H) \
    $(TREE_FLOW_H) tree-pass.h $(TREE_DUMP_H) $(DIAGNOSTIC_H) $(TIMEVAR_H) \

gcc/testsuite/ChangeLog

+2009-01-26  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/38851
+	* g++.dg/warn/Wuninitialized-1.C: New testcase.
+
 2009-01-25  Hans-Peter Nilsson  <hp@axis.com>
 
 	* gcc.dg/bitfld-15.c: Gate warning on target

gcc/testsuite/g++.dg/warn/Wuninitialized-1.C

+/* { dg-options "-O2 -Wuninitialized" } */
+
+struct Empty { Empty() {} }; /* { dg-bogus "uninitialized" } */
+struct Other {
+    Other(const Empty& e_) : e(e_) {}
+    Empty e;
+};
+void bar(Other&);
+void foo()
+{
+  Empty e;
+  Other o(e);
+  bar(o);
+}
+

gcc/tree-ssa-dse.c

@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-dump.h"
 #include "domwalk.h"
 #include "flags.h"
+#include "langhooks.h"
 
 /* This file implements dead store elimination.
 
@@ -660,20 +661,35 @@ execute_simple_dse (void)
         tree op;
 	bool removed = false;
         ssa_op_iter iter;
+	tree size;
 
-	if (gimple_stored_syms (stmt)
-	    && !bitmap_empty_p (gimple_stored_syms (stmt))
-            && (is_gimple_assign (stmt)
-	        || (is_gimple_call (stmt)
-                    && gimple_call_lhs (stmt)))
-	    && !bitmap_intersect_p (gimple_stored_syms (stmt), variables_loaded))
+	if (is_gimple_assign (stmt)
+	    && AGGREGATE_TYPE_P (TREE_TYPE (gimple_assign_lhs (stmt)))
+	    && (size = lang_hooks.expr_size (gimple_assign_lhs (stmt)))
+	    && integer_zerop (size))
+	  {
+	    if (dump_file && (dump_flags & TDF_DETAILS))
+	      {
+		fprintf (dump_file, "  Deleted zero-sized store '");
+		print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+		fprintf (dump_file, "'\n");
+	      }
+	    removed = true;
+	    gsi_remove (&gsi, true);
+	    todo |= TODO_cleanup_cfg;
+	  }
+	else if (gimple_stored_syms (stmt)
+		 && !bitmap_empty_p (gimple_stored_syms (stmt))
+		 && (is_gimple_assign (stmt)
+		     || (is_gimple_call (stmt)
+			 && gimple_call_lhs (stmt)))
+		 && !bitmap_intersect_p (gimple_stored_syms (stmt),
+					 variables_loaded))
 	  {
 	    unsigned int i;
 	    bitmap_iterator bi;
 	    bool dead = true;
 
-
-
 	    /* See if STMT only stores to write-only variables and
 	       verify that there are no volatile operands.  tree-ssa-operands
 	       sets has_volatile_ops flag for all statements involving