re PR c++/86763 (Wrong code comparing member of copy of a 237 byte object with…

re PR c++/86763 (Wrong code comparing member of copy of a 237 byte object with nontrivial default constructor on x86-64 arch)

2018-08-02  Richard Biener  <rguenther@suse.de>

	PR c++/86763
	* class.c (layout_class_type): Copy TYPE_TYPELESS_STORAGE
	to the CLASSTYPE_AS_BASE.

	* g++.dg/torture/pr86763.C: New testcase.

From-SVN: r263261

gcc/ChangeLog

 2018-08-02  Richard Biener  <rguenther@suse.de>
 
+	PR c++/86763
+	* class.c (layout_class_type): Copy TYPE_TYPELESS_STORAGE
+	to the CLASSTYPE_AS_BASE.
+
+2018-08-02  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/86816
 	* tree-ssa-tail-merge.c (tail_merge_valueize): New function
 	which checks for value availability before querying it.

gcc/cp/class.c

@@ -6279,6 +6279,7 @@ layout_class_type (tree t, tree *virtuals_p)
 				  bitsize_int (BITS_PER_UNIT)));
       SET_TYPE_ALIGN (base_t, rli->record_align);
       TYPE_USER_ALIGN (base_t) = TYPE_USER_ALIGN (t);
+      TYPE_TYPELESS_STORAGE (base_t) = TYPE_TYPELESS_STORAGE (t);
 
       /* Copy the non-static data members of T. This will include its
 	 direct non-virtual bases & vtable.  */

gcc/testsuite/ChangeLog

 2018-08-02  Richard Biener  <rguenther@suse.de>
 
+	PR c++/86763
+	* g++.dg/torture/pr86763.C: New testcase.
+
+2018-08-02  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/86816
 	* g++.dg/torture/pr86816.C: New testcase.
 

gcc/testsuite/g++.dg/torture/pr86763.C

+// { dg-do run }
+// { dg-additional-options "-fschedule-insns2 -fstrict-aliasing" }
+
+#include <cstdint>
+#include <cassert>
+#include <time.h>
+struct ID {
+  uint64_t value;
+};
+uint64_t value(ID id) { return id.value; }
+uint64_t gen { 1000 };
+struct Msg {
+  uint64_t time;
+  ID id;
+};
+struct V {
+  V() { }
+  V(Msg const & msg) : msg(msg) { }
+  Msg & get() { return msg; }
+  Msg msg;
+  char pad[237 - sizeof(Msg)];
+};
+struct T : V { using V::V; };
+Msg init_msg() {
+  Msg msg;
+  timespec t;
+  clock_gettime(CLOCK_REALTIME, &t);
+  msg.time = t.tv_sec + t.tv_nsec;
+  msg.id.value = ++gen;
+  return msg;
+}
+int main() {
+  T t;
+  t = init_msg();
+  assert(value(t.get().id) == 1001);
+}