optimize.c (copy_body_r): If MODIFY_EXPR has both arguments identical and they…

optimize.c (copy_body_r): If MODIFY_EXPR has both arguments identical and they would be replaced with...

	* optimize.c (copy_body_r): If MODIFY_EXPR has both arguments
	identical and they would be replaced with constant, remove
	MODIFY_EXPR from the tree.

	* g++.old-deja/g++.other/inline18.C: New test.

From-SVN: r39317

gcc/cp/ChangeLog

+2001-01-28  Jakub Jelinek  <jakub@redhat.com>
+
+	* optimize.c (copy_body_r): If MODIFY_EXPR has both arguments
+	identical and they would be replaced with constant, remove
+	MODIFY_EXPR from the tree.
+
 2001-01-27  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* Make-lang.in: Remove all dependencies on defaults.h.

gcc/cp/optimize.c

@@ -338,6 +338,26 @@ copy_body_r (tp, walk_subtrees, data)
 	  TREE_OPERAND (*tp, 1) = TREE_OPERAND (*tp, 3);
 	  TREE_OPERAND (*tp, 3) = NULL_TREE;
 	}
+      else if (TREE_CODE (*tp) == MODIFY_EXPR
+	       && TREE_OPERAND (*tp, 0) == TREE_OPERAND (*tp, 1)
+	       && nonstatic_local_decl_p (TREE_OPERAND (*tp, 0))
+	       && DECL_CONTEXT (TREE_OPERAND (*tp, 0)) == fn)
+	{
+	  /* Assignments like a = a; don't generate any rtl code
+	     and don't count as variable modification.  Avoid
+	     keeping bogosities like 0 = 0.  */
+	  tree decl = TREE_OPERAND (*tp, 0), value;
+	  splay_tree_node n;
+
+	  n = splay_tree_lookup (id->decl_map, (splay_tree_key) decl);
+	  if (n)
+	    {
+	      value = (tree) n->value;
+	      STRIP_TYPE_NOPS (value);
+	      if (TREE_CONSTANT (value) || TREE_READONLY_DECL_P (value))
+		*tp = value;
+	    }
+	}
     }
 
   /* Keep iterating.  */

gcc/testsuite/ChangeLog

+2001-01-28  Jakub Jelinek  <jakub@redhat.com>
+
+	* g++.old-deja/g++.other/inline18.C: New test.
+
 2001-01-27  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* gcc.c-torture/execute/stdio-opt-2.c: Also test __builtin_puts

gcc/testsuite/g++.old-deja/g++.other/inline18.C

+// Build don't link:
+// Origin: Jakub Jelinek <jakub@redhat.com>
+// Special g++ Options: -O3
+
+static void foo (int a)
+{
+  a = a;
+}
+
+static void bar (void)
+{
+  foo (-1);
+}