expr.c (cplus_expand_expr): Preserve temporaries when expanding STMT_EXPRs.

	* expr.c (cplus_expand_expr): Preserve temporaries when expanding
	STMT_EXPRs.
	* optimize.c (struct inline_data): Add target_exprs field.
	(declare_return_variable): When a function returns an aggregate,
	use the variable declared in the TARGET_EXPR as the remapped
	DECL_RESULT.
	(expand_call_inline): Update the pending target_exprs stack.
	(optimize_function): Initialize the stack.

From-SVN: r33561

gcc/cp/ChangeLog

 2000-04-30  Mark Mitchell  <mark@codesourcery.com>
 
+	* expr.c (cplus_expand_expr): Preserve temporaries when expanding
+	STMT_EXPRs.
+	* optimize.c (struct inline_data): Add target_exprs field.
+	(declare_return_variable): When a function returns an aggregate,
+	use the variable declared in the TARGET_EXPR as the remapped
+	DECL_RESULT.
+	(expand_call_inline): Update the pending target_exprs stack.
+	(optimize_function): Initialize the stack.
+	
 	* decl2.c (finish_file): Fix typo in comment.
 
 	* method.c (emit_thunk): Don't try to return a `void' value.

gcc/cp/expr.c

@@ -143,10 +143,21 @@ cplus_expand_expr (exp, target, tmode, modifier)
 
     case STMT_EXPR:
       {
-	tree rtl_expr = expand_start_stmt_expr ();
+	tree rtl_expr;
+	rtx result;
+
+	/* Since expand_expr_stmt calls free_temp_slots after every
+	   expression statement, we must call push_temp_slots here.
+	   Otherwise, any temporaries in use now would be considered
+	   out-of-scope after the first EXPR_STMT from within the
+	   STMT_EXPR.  */
+	push_temp_slots ();
+	rtl_expr = expand_start_stmt_expr ();
 	expand_stmt (STMT_EXPR_STMT (exp));
 	expand_end_stmt_expr (rtl_expr);
-	return expand_expr (rtl_expr, target, tmode, modifier);
+	result = expand_expr (rtl_expr, target, tmode, modifier);
+	pop_temp_slots ();
+	return result;
       }
       break;
 

gcc/cp/optimize.c

@@ -60,6 +60,8 @@ typedef struct inline_data
   /* Nonzero if we are currently within the cleanup for a
      TARGET_EXPR.  */
   int in_target_cleanup_p;
+  /* A stack of the TARGET_EXPRs that we are currently processing.  */
+  varray_type target_exprs;
 } inline_data;
 
 /* Prototypes.  */
@@ -462,6 +464,7 @@ declare_return_variable (id, use_stmt)
   tree fn = VARRAY_TOP_TREE (id->fns);
   tree result = DECL_RESULT (fn);
   tree var;
+  int aggregate_return_p;
 
   /* We don't need to do anything for functions that don't return
      anything.  */
@@ -472,8 +475,29 @@ declare_return_variable (id, use_stmt)
       return NULL_TREE;
     }
 
-  /* Make an appropriate copy.  */
-  var = copy_decl_for_inlining (result, fn, VARRAY_TREE (id->fns, 0));
+  /* Figure out whether or not FN returns an aggregate.  */
+  aggregate_return_p = IS_AGGR_TYPE (TREE_TYPE (result));
+
+  /* If FN returns an aggregate then the caller will always create the
+     temporary (using a TARGET_EXPR) and the call will be the
+     initializing expression for the TARGET_EXPR.  If we were just to
+     create a new VAR_DECL here, then the result of this function
+     would be copied (bitwise) into the variable initialized by the
+     TARGET_EXPR.  That's incorrect, so we must transform any
+     references to the RESULT into references to the target.  */
+  if (aggregate_return_p)
+    {
+      my_friendly_assert (id->target_exprs->elements_used != 0,
+			  20000430);
+      var = TREE_OPERAND (VARRAY_TOP_TREE (id->target_exprs), 0);
+      my_friendly_assert (same_type_p (TREE_TYPE (var), 
+				       TREE_TYPE (result)),
+			  20000430);
+    }
+  /* Otherwise, make an appropriate copy.  */
+  else
+    var = copy_decl_for_inlining (result, fn, VARRAY_TREE (id->fns, 0));
+
   /* Register the VAR_DECL as the equivalent for the RESULT_DECL; that
      way, when the RESULT_DECL is encountered, it will be
      automatically replaced by the VAR_DECL.  */
@@ -484,8 +508,14 @@ declare_return_variable (id, use_stmt)
   /* Build the USE_STMT.  */
   *use_stmt = build_min_nt (EXPR_STMT, var);
 
-  /* Build the declaration statement.  */
-  return build_min_nt (DECL_STMT, var);
+  /* Build the declaration statement if FN does not return an
+     aggregate.  */
+  if (!aggregate_return_p)
+    return build_min_nt (DECL_STMT, var);
+  /* If FN does return an aggregate, there's no need to declare the
+     return variable; we're using a variable in our caller's frame.  */
+  else
+    return NULL_TREE;
 }
 
 /* Returns non-zero if FN is a function that can be inlined.  */
@@ -586,6 +616,9 @@ expand_call_inline (tp, walk_subtrees, data)
       /* We're walking our own subtrees.  */
       *walk_subtrees = 0;
 
+      /* Push *TP on the stack of pending TARGET_EXPRs.  */
+      VARRAY_PUSH_TREE (id->target_exprs, *tp);
+
       /* Actually walk over them.  This loop is the body of
 	 walk_trees, omitting the case where the TARGET_EXPR
 	 itself is handled.  */
@@ -598,6 +631,9 @@ expand_call_inline (tp, walk_subtrees, data)
 	    --id->in_target_cleanup_p;
 	}
 
+      /* We're done with this TARGET_EXPR now.  */
+      VARRAY_POP (id->target_exprs);
+
       return NULL_TREE;
     }
 
@@ -780,12 +816,16 @@ optimize_function (fn)
 	    prev_fn = s->function_decl;
 	  }
 
+      /* Create the stack of TARGET_EXPRs.  */
+      VARRAY_TREE_INIT (id.target_exprs, 32, "target_exprs");
+
       /* Replace all calls to inline functions with the bodies of those
 	 functions.  */
       expand_calls_inline (&DECL_SAVED_TREE (fn), &id);
 
       /* Clean up.  */
       VARRAY_FREE (id.fns);
+      VARRAY_FREE (id.target_exprs);
     }
 }
 

gcc/testsuite/g++.old-deja/g++.other/dtor8.C

+// Special g++ Options: -O1
+// Origin: Mark Mitchell <mark@codesourcery.com>
+
+int result;
+
+struct S
+{
+  S ();
+  S (const S&);
+  ~S ();
+  
+  int i;
+  double d[18];
+};
+
+S* s;
+
+S::S ()
+{
+  s = this;
+}
+
+S::~S ()
+{
+  if (s != this)
+    result = 1;
+}
+
+inline S f ()
+{
+  return S ();
+}
+
+int main ()
+{
+  f ();
+  return result;
+}