class.c (update_vtable_entry_for_fn): Add index parameter.

cp:
	* class.c (update_vtable_entry_for_fn): Add index parameter.
	Generate vcall thunk for covariant overriding from a virtual
	primary base.
	(dfs_modify_vtables): Adjust.
testsuite:
	* g++.dg/abi/covariant1.C: New test.

From-SVN: r61906

gcc/cp/ChangeLog

@@ -1,3 +1,10 @@
+2003-01-27  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* class.c (update_vtable_entry_for_fn): Add index parameter.
+	Generate vcall thunk for covariant overriding from a virtual
+	primary base.
+	(dfs_modify_vtables): Adjust.
+
 2003-01-25  Nathan Sidwell  <nathan@codesourcery.com>
 
 	PR c++/9403

gcc/cp/class.c

@@ -190,7 +190,7 @@ static void mark_primary_bases (tree);
 static tree mark_primary_virtual_base (tree, tree);
 static void clone_constructors_and_destructors (tree);
 static tree build_clone (tree, tree);
-static void update_vtable_entry_for_fn (tree, tree, tree, tree *);
+static void update_vtable_entry_for_fn (tree, tree, tree, tree *, unsigned);
 static tree copy_virtuals (tree);
 static void build_ctor_vtbl_group (tree, tree);
 static void build_vtt (tree);
@@ -2395,7 +2395,8 @@ get_vcall_index (tree fn, tree type)
    corresponding position in the BINFO_VIRTUALS list.  */
 
 static void
-update_vtable_entry_for_fn (tree t, tree binfo, tree fn, tree* virtuals)
+update_vtable_entry_for_fn (tree t, tree binfo, tree fn, tree* virtuals,
+			    unsigned ix)
 {
   tree b;
   tree overrider;
@@ -2479,7 +2480,7 @@ update_vtable_entry_for_fn (tree t, tree binfo, tree fn, tree* virtuals)
 	      
 		  virtual_offset = binfo_for_vbase (BINFO_TYPE (thunk_binfo),
 						    TREE_TYPE (over_return));
-		  offset = size_diffop (offset,
+		  offset = size_binop (MINUS_EXPR, offset,
 					BINFO_OFFSET (virtual_offset));
 		}
 	      if (fixed_offset)
@@ -2523,6 +2524,38 @@ update_vtable_entry_for_fn (tree t, tree binfo, tree fn, tree* virtuals)
 	virtual_base = b;
     }
 
+  if (overrider_fn != overrider_target && !virtual_base)
+    {
+      /* The ABI specifies that a covariant thunk includes a mangling
+   	 for a this pointer adjustment.  This-adjusting thunks that
+   	 override a function from a virtual base have a vcall
+   	 adjustment.  When the virtual base in question is a primary
+   	 virtual base, we know the adjustments are zero, (and in the
+   	 non-covariant case, we would not use the thunk).
+   	 Unfortunately we didn't notice this could happen, when
+   	 designing the ABI and so never mandated that such a covariant
+   	 thunk should be emitted.  Because we must use the ABI mandated
+   	 name, we must continue searching from the binfo where we
+   	 found the most recent definition of the function, towards the
+   	 primary binfo which first introduced the function into the
+   	 vtable.  If that enters a virtual base, we must use a vcall
+   	 this-adjusting thunk.  Bleah! */
+      tree probe;
+      
+      for (probe = first_defn; (probe = get_primary_binfo (probe));)
+	{
+	  if (TREE_VIA_VIRTUAL (probe))
+	    virtual_base = probe;
+	  if ((unsigned) list_length (BINFO_VIRTUALS (probe)) <= ix)
+	    break;
+	}
+      if (virtual_base)
+	/* Even if we find a virtual base, the correct delta is
+	   between the overrider and the binfo we're building a vtable
+	   for.  */
+	goto virtual_covariant;
+    }
+  
   /* Compute the constant adjustment to the `this' pointer.  The
      `this' pointer, when this function is called, will point at BINFO
      (or one of its primary bases, which are at the same offset).  */
@@ -2541,6 +2574,7 @@ update_vtable_entry_for_fn (tree t, tree binfo, tree fn, tree* virtuals)
     /* The `this' pointer needs to be adjusted from pointing to
        BINFO to pointing at the base where the final overrider
        appears.  */
+    virtual_covariant:
     delta = size_diffop (BINFO_OFFSET (TREE_VALUE (overrider)),
 			 BINFO_OFFSET (binfo));
 
@@ -2564,26 +2598,25 @@ dfs_modify_vtables (tree binfo, void* data)
       /* Similarly, a base without a vtable needs no modification.  */
       && CLASSTYPE_VFIELDS (BINFO_TYPE (binfo)))
     {
-      tree t;
+      tree t = (tree) data;
       tree virtuals;
       tree old_virtuals;
-
-      t = (tree) data;
+      unsigned ix;
       
       make_new_vtable (t, binfo);
       
       /* Now, go through each of the virtual functions in the virtual
 	 function table for BINFO.  Find the final overrider, and
 	 update the BINFO_VIRTUALS list appropriately.  */
-      for (virtuals = BINFO_VIRTUALS (binfo),
+      for (ix = 0, virtuals = BINFO_VIRTUALS (binfo),
 	     old_virtuals = BINFO_VIRTUALS (TYPE_BINFO (BINFO_TYPE (binfo)));
 	   virtuals;
-	   virtuals = TREE_CHAIN (virtuals),
+	   ix++, virtuals = TREE_CHAIN (virtuals),
 	     old_virtuals = TREE_CHAIN (old_virtuals))
 	update_vtable_entry_for_fn (t, 
 				    binfo, 
 				    BV_FN (old_virtuals),
-				    &virtuals);
+				    &virtuals, ix);
     }
 
   SET_BINFO_MARKED (binfo);

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2003-01-27  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* g++.dg/abi/covariant1.C: New test.
+
 2003-01-25  Ulrich Weigand  <uweigand@de.ibm.com>
 
 	* gcc.dg/20030123-1.c: New test.

gcc/testsuite/g++.dg/abi/covariant1.C

@@ -0,0 +1,21 @@
+// { dg-do compile }
+// { dg-options "-w" }
+
+// We don't want to use a covariant thunk to have a virtual
+// primary base
+
+struct c4 {};
+
+struct c6 : c4 { virtual c4* f17(); };
+
+c4* c6::f17() { return 0; }
+
+struct c11 : virtual c6 { int i; };
+
+struct c12 : c11 { };
+
+struct c14 : 
+  virtual c12,
+  virtual c11 { virtual c12* f17(); };
+
+// { dg-final { scan-assembler-not "\n_ZTch0_v0_n16_N3c143f17Ev\[: \t\n\]" } }