c++: [[no_unique_address]] and virtual base [PR104139]

Fixing a thinko in my patch for 103681: when computing the size of a virtual
base, it would help to use its binfo instead of the one for the derived
class.

	PR c++/104139
	PR c++/103681

gcc/cp/ChangeLog:

	* class.cc (end_of_class): Use base_binfo.

gcc/testsuite/ChangeLog:

	* g++.dg/abi/no_unique_address2.C: Adjust to detect this on x86-64.

gcc/cp/class.cc

@@ -6414,8 +6414,8 @@ end_of_class (tree t, eoc_mode mode)
       {
 	if (mode == eoc_nv_or_dsize)
 	  /* For dsize, don't count trailing empty bases.  */
-	  offset = size_binop (PLUS_EXPR, BINFO_OFFSET (binfo),
-			       CLASSTYPE_SIZE_UNIT (BINFO_TYPE (binfo)));
+	  offset = size_binop (PLUS_EXPR, BINFO_OFFSET (base_binfo),
+			       CLASSTYPE_SIZE_UNIT (BINFO_TYPE (base_binfo)));
 	else
 	  offset = end_of_base (base_binfo);
 	if (tree_int_cst_lt (result, offset))

gcc/testsuite/g++.dg/abi/no_unique_address2.C

@@ -41,3 +41,30 @@ struct B4
 #define SA(X) static_assert ((X), #X)
 SA (sizeof (B2) == sizeof (B1));
 SA (sizeof (B3) == sizeof (B4));
+
+namespace N2
+{
+  // C as big as _vptr to test PR c++/104139
+  struct C
+  {
+    long c;
+  };
+
+  struct D: virtual C
+  {
+    virtual void f();
+  };
+
+  struct B3: D
+  {
+    char c2;
+  };
+
+  struct B4
+  {
+    D d [[no_unique_address]];
+    char c2;
+  };
+
+  SA (sizeof (B3) == sizeof (B4));
+}