re PR libmudflap/19319 (Mudflap produce many violations on simple, correct c++ program)

        PR mudflap/19319
        * gimplify.c (gimplify_modify_expr_rhs) [CALL_EXPR]: Make return
        slot explicit.

        PR c++/16405
        * fold-const.c (fold_indirect_ref_1): Split out from...
        (build_fold_indirect_ref): Here.
        (fold_indirect_ref): New fn.
        * tree.h: Declare it.
        * gimplify.c (gimplify_compound_lval): Call fold_indirect_ref.
        (gimplify_modify_expr_rhs): Likewise.
        (gimplify_expr): Likewise.

From-SVN: r94979

gcc/ChangeLog

+2005-02-13  Jason Merrill  <jason@redhat.com>
+
+	PR mudflap/19319
+	* gimplify.c (gimplify_modify_expr_rhs) [CALL_EXPR]: Make return
+	slot explicit.
+
+	PR c++/16405
+	* fold-const.c (fold_indirect_ref_1): Split out from...
+	(build_fold_indirect_ref): Here.
+	(fold_indirect_ref): New fn.
+	* tree.h: Declare it.
+	* gimplify.c (gimplify_compound_lval): Call fold_indirect_ref.
+	(gimplify_modify_expr_rhs): Likewise.
+	(gimplify_expr): Likewise.
+
 2005-02-13  James A. Morrison  <phython@gcc.gnu.org>
 
 	PR tree-optimization/14303

gcc/fold-const.c

@@ -11217,17 +11217,21 @@ build_fold_addr_expr (tree t)
   return build_fold_addr_expr_with_type (t, build_pointer_type (TREE_TYPE (t)));
 }
 
-/* Builds an expression for an indirection through T, simplifying some
-   cases.  */
+/* Given a pointer value T, return a simplified version of an indirection
+   through T, or NULL_TREE if no simplification is possible.  */
 
-tree
-build_fold_indirect_ref (tree t)
+static tree
+fold_indirect_ref_1 (tree t)
 {
   tree type = TREE_TYPE (TREE_TYPE (t));
   tree sub = t;
   tree subtype;
 
   STRIP_NOPS (sub);
+  subtype = TREE_TYPE (sub);
+  if (!POINTER_TYPE_P (subtype))
+    return NULL_TREE;
+
   if (TREE_CODE (sub) == ADDR_EXPR)
     {
       tree op = TREE_OPERAND (sub, 0);
@@ -11242,7 +11246,6 @@ build_fold_indirect_ref (tree t)
     }
 
   /* *(foo *)fooarrptr => (*fooarrptr)[0] */
-  subtype = TREE_TYPE (sub);
   if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE
       && lang_hooks.types_compatible_p (type, TREE_TYPE (TREE_TYPE (subtype))))
     {
@@ -11250,7 +11253,34 @@ build_fold_indirect_ref (tree t)
       return build4 (ARRAY_REF, type, sub, size_zero_node, NULL_TREE, NULL_TREE);
     }
 
-  return build1 (INDIRECT_REF, type, t);
+  return NULL_TREE;
+}
+
+/* Builds an expression for an indirection through T, simplifying some
+   cases.  */
+
+tree
+build_fold_indirect_ref (tree t)
+{
+  tree sub = fold_indirect_ref_1 (t);
+
+  if (sub)
+    return sub;
+  else
+    return build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (t)), t);
+}
+
+/* Given an INDIRECT_REF T, return either T or a simplified version.  */
+
+tree
+fold_indirect_ref (tree t)
+{
+  tree sub = fold_indirect_ref_1 (TREE_OPERAND (t, 0));
+
+  if (sub)
+    return sub;
+  else
+    return t;
 }
 
 /* Strip non-trapping, non-side-effecting tree nodes from an expression

gcc/gimplify.c

@@ -1433,8 +1433,15 @@ gimplify_compound_lval (tree *expr_p, tree *pre_p,
   VARRAY_GENERIC_PTR_NOGC_INIT (stack, 10, "stack");
 
   /* We can handle anything that get_inner_reference can deal with.  */
-  for (p = expr_p; handled_component_p (*p); p = &TREE_OPERAND (*p, 0))
-    VARRAY_PUSH_GENERIC_PTR_NOGC (stack, *p);
+  for (p = expr_p; ; p = &TREE_OPERAND (*p, 0))
+    {
+      /* Fold INDIRECT_REFs now to turn them into ARRAY_REFs.  */
+      if (TREE_CODE (*p) == INDIRECT_REF)
+	*p = fold_indirect_ref (*p);
+      if (!handled_component_p (*p))
+	break;
+      VARRAY_PUSH_GENERIC_PTR_NOGC (stack, *p);
+    }
 
   gcc_assert (VARRAY_ACTIVE_SIZE (stack));
 
@@ -2845,16 +2852,10 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
 	     This kind of code arises in C++ when an object is bound
 	     to a const reference, and if "x" is a TARGET_EXPR we want
 	     to take advantage of the optimization below.  */
-	  tree pointer;
-
-	  pointer = TREE_OPERAND (*from_p, 0);
-	  STRIP_NOPS (pointer);
-	  if (TREE_CODE (pointer) == ADDR_EXPR
-	      && (lang_hooks.types_compatible_p 
-		  (TREE_TYPE (TREE_OPERAND (pointer, 0)),
-		   TREE_TYPE (*from_p))))
+	  tree t = fold_indirect_ref (*from_p);
+	  if (t != *from_p)
 	    {
-	      *from_p = TREE_OPERAND (pointer, 0); 
+	      *from_p = t;
 	      ret = GS_OK;
 	    }
 	  else
@@ -2912,6 +2913,55 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
 	  ret = GS_UNHANDLED;
 	break;
 
+      case CALL_EXPR:
+	/* For calls that return in memory, give *to_p as the CALL_EXPR's
+	   return slot so that we don't generate a temporary.  */
+	if (aggregate_value_p (*from_p, *from_p))
+	  {
+	    tree init = *from_p;
+	    tree fn = TREE_OPERAND (init, 0);
+	    tree args = TREE_OPERAND (init, 1);
+	    tree rettype = TREE_TYPE (TREE_TYPE (TREE_TYPE (fn)));
+	    tree arg = *to_p;
+	    tree type;
+
+	    /* Only use the original target if *to_p isn't already
+	       addressable; if its address escapes, and the called function
+	       uses the NRV optimization, a conforming program could see
+	       *to_p change before the called function returns.  */
+	    bool use_temp = !is_gimple_non_addressable (*to_p);
+	    if (use_temp)
+	      {
+		arg = create_tmp_var (rettype, "ret");
+		*from_p = arg;
+	      }
+
+	    type = TREE_TYPE (arg);
+	    /* FIXME: Mark the address as not escaping.  */
+	    lang_hooks.mark_addressable (arg);
+	    arg = build1 (ADDR_EXPR, build_pointer_type (type), arg);
+	    /* The return type might have different cv-quals from arg.  */
+	    arg = convert (build_pointer_type (rettype), arg);
+	    args = tree_cons (NULL_TREE, arg, args);
+	    init = build3 (CALL_EXPR, rettype, fn, args, NULL_TREE);
+	    CALL_EXPR_HAS_RETURN_SLOT_ADDR (init) = 1;
+	    TREE_USED (init) = 1;
+
+	    if (use_temp)
+	      gimplify_and_add (init, pre_p);
+	    else if (want_value)
+	      {
+		gimplify_and_add (init, pre_p);
+		*expr_p = *to_p;
+	      }
+	    else
+	      *expr_p = init;
+	    ret = GS_OK;
+	  }
+	else
+	  ret = GS_UNHANDLED;
+	break;
+
       default:
 	ret = GS_UNHANDLED;
 	break;
@@ -3544,7 +3594,7 @@ gimplify_target_expr (tree *expr_p, tree *pre_p, tree *post_p)
 	  ret = GS_OK;
           if (TREE_CODE (init) == BIND_EXPR)
 	    gimplify_bind_expr (&init, temp, pre_p);
-          if (init != temp)
+	  if (init != temp)
 	    {
 	      init = build (MODIFY_EXPR, void_type_node, temp, init);
 	      ret = gimplify_expr (&init, pre_p, post_p, is_gimple_stmt,
@@ -3795,9 +3845,13 @@ gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p,
 	  recalculate_side_effects (*expr_p);
 	  break;
 
+	case INDIRECT_REF:
+	  *expr_p = fold_indirect_ref (*expr_p);
+	  if (*expr_p != save_expr)
+	    break;
+	  /* else fall through.  */
 	case ALIGN_INDIRECT_REF:
 	case MISALIGNED_INDIRECT_REF:
-	case INDIRECT_REF:
 	  ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p, post_p,
 			       is_gimple_reg, fb_rvalue);
 	  recalculate_side_effects (*expr_p);

gcc/tree.h

@@ -3546,6 +3546,7 @@ extern tree fold_build_cleanup_point_expr (tree type, tree expr);
 extern tree fold_strip_sign_ops (tree);
 extern tree build_fold_addr_expr_with_type (tree, tree);
 extern tree build_fold_indirect_ref (tree);
+extern tree fold_indirect_ref (tree);
 extern tree constant_boolean_node (int, tree);
 extern tree build_low_bits_mask (tree, unsigned);