re PR c++/23372 (Temporary aggregate copy not elided when passing parameters by value)

	PR c++/23372
	* gimplify.c (gimplify_arg): Strip redundant TARGET_EXPR.

From-SVN: r171146

gcc/ChangeLog

+2011-03-18  Jason Merrill  <jason@redhat.com>
+
+	PR c++/23372
+	* gimplify.c (gimplify_arg): Strip redundant TARGET_EXPR.
+
 2011-03-18  Richard Guenther  <rguenther@suse.de>
 
 	* doc/install.texi (--enable-gold): Remove.

gcc/gimplify.c

@@ -2255,7 +2255,17 @@ gimplify_arg (tree *arg_p, gimple_seq *pre_p, location_t call_location)
   if (is_gimple_reg_type (TREE_TYPE (*arg_p)))
     test = is_gimple_val, fb = fb_rvalue;
   else
-    test = is_gimple_lvalue, fb = fb_either;
+    {
+      test = is_gimple_lvalue, fb = fb_either;
+      /* Also strip a TARGET_EXPR that would force an extra copy.  */
+      if (TREE_CODE (*arg_p) == TARGET_EXPR)
+	{
+	  tree init = TARGET_EXPR_INITIAL (*arg_p);
+	  if (init
+	      && !VOID_TYPE_P (TREE_TYPE (init)))
+	    *arg_p = init;
+	}
+    }
 
   /* If this is a variable sized type, we must remember the size.  */
   maybe_with_size_expr (arg_p);

gcc/testsuite/ChangeLog

 2011-03-18  Jason Merrill  <jason@redhat.com>
 
+	* g++.dg/opt/pr23372.C: New.
+
 	* g++.dg/ext/attrib32.C: Expect errors on the two-names case.
 
 2011-03-18  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

gcc/testsuite/g++.dg/opt/pr23372.C

+// PR c++/23372
+// { dg-options -fdump-tree-gimple }
+
+// There shouldn't be an assignment to a temporary in the GIMPLE,
+// as that represents a redundant copy.
+// { dg-final { scan-tree-dump-not "=" gimple } }
+
+struct A {
+  int a[1000];
+  //A(A const &);
+};
+void f(A);
+void g(A *a) { f(*a); }
+
+// { dg-final { cleanup-tree-dump gimple } }