7041100: The load in String.equals intrinsic executed before null check

Summary: Remove control from loads in String.equals intrinsic and cast argument to not-null.
Reviewed-by: never

src/share/vm/opto/library_call.cpp

@@ -867,12 +867,10 @@ Node* LibraryCallKit::make_string_method_node(int opcode, Node* str1, Node* cnt1
   Node* str1_offset  = make_load(no_ctrl, str1_offseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
   Node* str1_start   = array_element_address(str1_value, str1_offset, T_CHAR);
 
-  // Pin loads from String::equals() argument since it could be NULL.
-  Node* str2_ctrl = (opcode == Op_StrEquals) ? control() : no_ctrl;
   Node* str2_valuea  = basic_plus_adr(str2, str2, value_offset);
-  Node* str2_value   = make_load(str2_ctrl, str2_valuea, value_type, T_OBJECT, string_type->add_offset(value_offset));
+  Node* str2_value   = make_load(no_ctrl, str2_valuea, value_type, T_OBJECT, string_type->add_offset(value_offset));
   Node* str2_offseta = basic_plus_adr(str2, str2, offset_offset);
-  Node* str2_offset  = make_load(str2_ctrl, str2_offseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
+  Node* str2_offset  = make_load(no_ctrl, str2_offseta, TypeInt::INT, T_INT, string_type->add_offset(offset_offset));
   Node* str2_start   = array_element_address(str2_value, str2_offset, T_CHAR);
 
   Node* result = NULL;
@@ -1012,14 +1010,15 @@ bool LibraryCallKit::inline_string_equals() {
   if (!stopped()) {
     // Properly cast the argument to String
     argument = _gvn.transform(new (C, 2) CheckCastPPNode(control(), argument, string_type));
+    // This path is taken only when argument's type is String:NotNull.
+    argument = cast_not_null(argument, false);
 
     // Get counts for string and argument
     Node* receiver_cnta = basic_plus_adr(receiver, receiver, count_offset);
     receiver_cnt  = make_load(no_ctrl, receiver_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
 
-    // Pin load from argument string since it could be NULL.
     Node* argument_cnta = basic_plus_adr(argument, argument, count_offset);
-    argument_cnt  = make_load(control(), argument_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
+    argument_cnt  = make_load(no_ctrl, argument_cnta, TypeInt::INT, T_INT, string_type->add_offset(count_offset));
 
     // Check for receiver count != argument count
     Node* cmp = _gvn.transform( new(C, 3) CmpINode(receiver_cnt, argument_cnt) );

test/compiler/7041100/Test7041100.java

+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+/**
+ * @test
+ * @bug 7041100
+ * @summary The load in String.equals intrinsic executed before null check
+ *
+ * @run main/othervm -Xbatch Test7041100 abc def
+ */
+
+public class Test7041100 {
+
+    static String n = null;
+    public static void main(String[] args) throws Exception {
+        for (int i = 0; i < 10000; i++) {
+            stringEQ(args[0], args[1]);
+            stringEQ(args[0], args[0]);
+            stringEQ(args[0], n);
+            stringEQ(n, args[0]);
+        }
+    }
+
+    public static boolean stringEQ(String a, String b) {
+        if (a == b)
+            return true;
+        if (a == null || b == null)
+            return false;
+        else
+            return a.equals(b);
+    }
+}