re PR c++/70272 (-flifetime-dse miscompilation starting with r217967)

	PR c++/70272
	* decl.c (begin_destructor_body): Don't insert clobber if
	is_empty_class (current_class_type).

	* g++.dg/opt/flifetime-dse5.C (main): Remove extra semicolon.
	* g++.dg/opt/flifetime-dse6.C: New test.
	* g++.dg/tree-ssa/ehcleanup-1.C: Adjust unreachable count.

From-SVN: r234296

gcc/cp/ChangeLog

+2016-03-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/70272
+	* decl.c (begin_destructor_body): Don't insert clobber if
+	is_empty_class (current_class_type).
+
 2016-03-17  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/70194

gcc/cp/decl.c

@@ -14354,7 +14354,9 @@ begin_destructor_body (void)
       initialize_vtbl_ptrs (current_class_ptr);
       finish_compound_stmt (compound_stmt);
 
-      if (flag_lifetime_dse)
+      if (flag_lifetime_dse
+	  /* Clobbering an empty base is harmful if it overlays real data.  */
+	  && !is_empty_class (current_class_type))
 	{
 	  /* Insert a cleanup to let the back end know that the object is dead
 	     when we exit the destructor, either normally or via exception.  */

gcc/testsuite/ChangeLog

+2016-03-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/70272
+	* g++.dg/opt/flifetime-dse5.C (main): Remove extra semicolon.
+	* g++.dg/opt/flifetime-dse6.C: New test.
+	* g++.dg/tree-ssa/ehcleanup-1.C: Adjust unreachable count.
+
 2016-03-17  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR driver/70192

gcc/testsuite/g++.dg/opt/flifetime-dse5.C

@@ -10,4 +10,4 @@ int main() {
   C c;
   if ( c.a == false )
     __builtin_abort();
-};
+}

gcc/testsuite/g++.dg/opt/flifetime-dse6.C

+// PR c++/70272
+// { dg-options -O2 }
+// { dg-do run }
+
+struct Empty { };
+struct A { A() : a(true) { } bool a; ~A() { if (!a) __builtin_abort(); } };
+struct B : Empty { B() : Empty() { } ~B() { } };
+struct C : A, B { C() : A(), B() { } ~C() { } };
+int main() {
+  C c;
+}

gcc/testsuite/g++.dg/tree-ssa/ehcleanup-1.C

@@ -26,5 +26,5 @@ t (void)
 // { dg-final { scan-tree-dump-times "Empty EH handler" 2 "ehcleanup1" } }
 //
 // And as a result also contained control flow.
-// { dg-final { scan-tree-dump-times "Removing unreachable" 6 "ehcleanup1" } }
+// { dg-final { scan-tree-dump-times "Removing unreachable" 4 "ehcleanup1" } }
 //