C++ PATCH: PR 12815

[Mark Mitchell]

This patch fixes a code-gen problem in the C++ front end.  Jason (some
while back) marked as all vtable references as TREE_CONSTANT, which
doesn't make sense.  If the object isn't TREE_CONSTANT, and its
dynamic type is not known, then it's vtable entries are not
TREE_CONSTANT either, although they are TREE_READONLY.  Jason, am I
missing something here?

Also, it's a bid lame to ever return a TREE_CONSTANT vtable entry.  If
we know which vtable entry it is, we should just go find the right
entry in the array and use it; no need to go indexing around at all.
But, that's for another day...

Tested on i686-pc-linux-gnu, applied on the mainline.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com

2004-01-05  Mark Mitchell  <mark@codesourcery.com>

	PR c++/12815
	* class.c (build_vtbl_ref_1): Do not unconditionally mark vtable
	references as constant.

2004-01-05  Mark Mitchell  <mark@codesourcery.com>

	PR c++/12815
	* g++.dg/rtti/typeid4.C: New test.

Index: cp/class.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/class.c,v
retrieving revision 1.591
diff -c -5 -p -r1.591 class.c
*** cp/class.c	25 Dec 2003 16:28:50 -0000	1.591
--- cp/class.c	6 Jan 2004 00:49:27 -0000
*************** build_vtbl_ref_1 (tree instance, tree id
*** 453,463 ****
      vtbl = build_vfield_ref (instance, basetype);
    
    assemble_external (vtbl);
  
    aref = build_array_ref (vtbl, idx);
!   TREE_CONSTANT (aref) = 1;
  
    return aref;
  }
  
  tree
--- 453,463 ----
      vtbl = build_vfield_ref (instance, basetype);
    
    assemble_external (vtbl);
  
    aref = build_array_ref (vtbl, idx);
!   TREE_CONSTANT (aref) |= TREE_CONSTANT (vtbl) && TREE_CONSTANT (idx);
  
    return aref;
  }
  
  tree
Index: testsuite/g++.dg/rtti/typeid4.C
===================================================================
RCS file: testsuite/g++.dg/rtti/typeid4.C
diff -N testsuite/g++.dg/rtti/typeid4.C
*** /dev/null	1 Jan 1970 00:00:00 -0000
--- testsuite/g++.dg/rtti/typeid4.C	6 Jan 2004 00:49:27 -0000
***************
*** 0 ****
--- 1,26 ----
+ // { dg-do run }
+ // { dg-options "-O2" }
+ 
+ #include <typeinfo>
+ #include <iostream>
+ 
+ struct A { virtual ~A () {} };
+ 
+ struct APtr
+ { 
+   APtr (A* p)  : p_ (p) { }
+   A& operator* () const { return *p_; }
+   A* p_;
+ };
+ 
+ int main ()
+ { 
+   APtr ap (new A);
+   std::type_info const* const exp = &typeid (*ap);
+   for (bool cont = true; cont; cont = false)
+     { 
+       std::cout << "inner: cont " << cont << std::endl;
+       if (exp) ;
+     }
+ }
+