typeck.c (build_ptrmemfunc): Handle PTRMEM_CSTs carefully to reveal optimization opportunities.

	* typeck.c (build_ptrmemfunc): Handle PTRMEM_CSTs carefully to
	reveal optimization opportunities.

From-SVN: r27084

gcc/cp/ChangeLog

 1999-05-21  Mark Mitchell  <mark@codesourcery.com>
 
+	* typeck.c (build_ptrmemfunc): Handle PTRMEM_CSTs carefully to
+	reveal optimization opportunities.
+
 	* pt.c (tsubst): Don't issue error messages when we're not
 	complaining, even if we see a qualified function type.
 	(check_cv_quals_for_unify): Don't allow a qualified function

gcc/cp/typeck.c

@@ -6515,15 +6515,15 @@ build_ptrmemfunc (type, pfn, force)
      tree type, pfn;
      int force;
 {
-  tree idx = integer_zero_node;
-  tree delta = integer_zero_node;
-  tree delta2 = integer_zero_node;
-  tree npfn = NULL_TREE;
   tree fn;
   
   /* Handle multiple conversions of pointer to member functions.  */
   if (TYPE_PTRMEMFUNC_P (TREE_TYPE (pfn)))
     {
+      tree idx = integer_zero_node;
+      tree delta = integer_zero_node;
+      tree delta2 = integer_zero_node;
+      tree npfn = NULL_TREE;
       tree ndelta, ndelta2;
       tree e1, e2, e3, n;
       tree pfn_type;
@@ -6537,18 +6537,42 @@ build_ptrmemfunc (type, pfn, force)
 	  && comp_target_types (type, pfn_type, 1) != 1)
 	cp_error ("conversion to `%T' from `%T'", type, pfn_type);
 
-      ndelta = cp_convert (ptrdiff_type_node, build_component_ref (pfn, delta_identifier, NULL_TREE, 0));
-      ndelta2 = cp_convert (ptrdiff_type_node, DELTA2_FROM_PTRMEMFUNC (pfn));
-      idx = build_component_ref (pfn, index_identifier, NULL_TREE, 0);
+      if (TREE_CODE (pfn) == PTRMEM_CST)
+	{
+	  /* We could just build the resulting CONSTRUCTOR now, but we
+	     don't, relying on the general machinery below, together
+	     with constant-folding, to do the right thing.  We don't
+	     want to return a PTRMEM_CST here, even though we could,
+	     because a pointer-to-member constant ceases to be a
+	     constant (from the point of view of the language) when it
+	     is cast to another type.  */
+
+	  expand_ptrmemfunc_cst (pfn, &ndelta, &idx, &npfn, &ndelta2);
+	  if (npfn)
+	    /* This constant points to a non-virtual function.
+	       NDELTA2 will be NULL, but it's value doesn't really
+	       matter since we won't use it anyhow.  */
+	    ndelta2 = integer_zero_node;
+	}
+      else
+	{
+	  ndelta = cp_convert (ptrdiff_type_node, 
+			       build_component_ref (pfn, 
+						    delta_identifier, 
+						    NULL_TREE, 0));
+	  ndelta2 = cp_convert (ptrdiff_type_node, 
+				DELTA2_FROM_PTRMEMFUNC (pfn));
+	  idx = build_component_ref (pfn, index_identifier, NULL_TREE, 0);
+	}
 
       n = get_delta_difference (TYPE_METHOD_BASETYPE (TREE_TYPE (pfn_type)),
 				TYPE_METHOD_BASETYPE (TREE_TYPE (type)),
 				force);
-
       delta = build_binary_op (PLUS_EXPR, ndelta, n);
       delta2 = build_binary_op (PLUS_EXPR, ndelta2, n);
       e1 = fold (build (GT_EXPR, boolean_type_node, idx, integer_zero_node));
 	  
+      /* If it's a virtual function, this is what we want.  */
       e2 = build_ptrmemfunc1 (TYPE_GET_PTRMEMFUNC_TYPE (type), delta, idx,
 			      NULL_TREE, delta2);
 
@@ -6556,8 +6580,10 @@ build_ptrmemfunc (type, pfn, force)
       npfn = build1 (NOP_EXPR, type, pfn);
       TREE_CONSTANT (npfn) = TREE_CONSTANT (pfn);
 
-      e3 = build_ptrmemfunc1 (TYPE_GET_PTRMEMFUNC_TYPE (type), delta, idx, npfn,
-			      NULL_TREE);
+      /* But if it's a non-virtual function, or NULL, we use this
+	 instead.  */
+      e3 = build_ptrmemfunc1 (TYPE_GET_PTRMEMFUNC_TYPE (type), delta,
+			      idx, npfn, NULL_TREE);
       return build_conditional_expr (e1, e2, e3);
     }