# HG changeset patch
# User thartmann
# Date 1465316444 -7200
# Node ID d139a133ba270086ecf4dc863663b3841c470dd6
# Parent  ec2d5ec5571cdd74525cc94bf20555874824bde8
8158228: C1 incorrectly folds mismatched loads from stable arrays
Summary: Disable constant folding for mismatched loads from stable arrays.
Reviewed-by: vlivanov

diff -r ec2d5ec5571c -r d139a133ba27 hotspot/src/share/vm/c1/c1_Canonicalizer.cpp
--- a/hotspot/src/share/vm/c1/c1_Canonicalizer.cpp	Tue Jun 07 09:11:32 2016 +0000
+++ b/hotspot/src/share/vm/c1/c1_Canonicalizer.cpp	Tue Jun 07 18:20:44 2016 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2016, 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
@@ -264,7 +264,7 @@
   assert(array == NULL || FoldStableValues, "not enabled");
 
   // Constant fold loads from stable arrays.
-  if (array != NULL && index != NULL) {
+  if (!x->mismatched() && array != NULL && index != NULL) {
     jint idx = index->value();
     if (idx < 0 || idx >= array->value()->length()) {
       // Leave the load as is. The range check will handle it.
@@ -310,8 +310,6 @@
       return;
     }
   }
-
-
 }
 
 
diff -r ec2d5ec5571c -r d139a133ba27 hotspot/src/share/vm/c1/c1_GraphBuilder.cpp
--- a/hotspot/src/share/vm/c1/c1_GraphBuilder.cpp	Tue Jun 07 09:11:32 2016 +0000
+++ b/hotspot/src/share/vm/c1/c1_GraphBuilder.cpp	Tue Jun 07 18:20:44 2016 +0200
@@ -4227,11 +4227,11 @@
   Value index = args->at(1);
   if (is_store) {
     Value value = args->at(2);
-    Instruction* store = append(new StoreIndexed(array, index, NULL, T_CHAR, value, state_before, false));
+    Instruction* store = append(new StoreIndexed(array, index, NULL, T_CHAR, value, state_before, false, true));
     store->set_flag(Instruction::NeedsRangeCheckFlag, false);
     _memory->store_value(value);
   } else {
-    Instruction* load = append(new LoadIndexed(array, index, NULL, T_CHAR, state_before));
+    Instruction* load = append(new LoadIndexed(array, index, NULL, T_CHAR, state_before, true));
     load->set_flag(Instruction::NeedsRangeCheckFlag, false);
     push(load->type(), load);
   }
diff -r ec2d5ec5571c -r d139a133ba27 hotspot/src/share/vm/c1/c1_Instruction.hpp
--- a/hotspot/src/share/vm/c1/c1_Instruction.hpp	Tue Jun 07 09:11:32 2016 +0000
+++ b/hotspot/src/share/vm/c1/c1_Instruction.hpp	Tue Jun 07 18:20:44 2016 +0200
@@ -912,14 +912,16 @@
   Value     _index;
   Value     _length;
   BasicType _elt_type;
+  bool      _mismatched;
 
  public:
   // creation
-  AccessIndexed(Value array, Value index, Value length, BasicType elt_type, ValueStack* state_before)
+  AccessIndexed(Value array, Value index, Value length, BasicType elt_type, ValueStack* state_before, bool mismatched)
   : AccessArray(as_ValueType(elt_type), array, state_before)
   , _index(index)
   , _length(length)
   , _elt_type(elt_type)
+  , _mismatched(mismatched)
   {
     set_flag(Instruction::NeedsRangeCheckFlag, true);
     ASSERT_VALUES
@@ -929,6 +931,7 @@
   Value index() const                            { return _index; }
   Value length() const                           { return _length; }
   BasicType elt_type() const                     { return _elt_type; }
+  bool mismatched() const                        { return _mismatched; }
 
   void clear_length()                            { _length = NULL; }
   // perform elimination of range checks involving constants
@@ -945,8 +948,8 @@
 
  public:
   // creation
-  LoadIndexed(Value array, Value index, Value length, BasicType elt_type, ValueStack* state_before)
-  : AccessIndexed(array, index, length, elt_type, state_before)
+  LoadIndexed(Value array, Value index, Value length, BasicType elt_type, ValueStack* state_before, bool mismatched = false)
+  : AccessIndexed(array, index, length, elt_type, state_before, mismatched)
   , _explicit_null_check(NULL) {}
 
   // accessors
@@ -974,8 +977,9 @@
 
  public:
   // creation
-  StoreIndexed(Value array, Value index, Value length, BasicType elt_type, Value value, ValueStack* state_before, bool check_boolean)
-  : AccessIndexed(array, index, length, elt_type, state_before)
+  StoreIndexed(Value array, Value index, Value length, BasicType elt_type, Value value, ValueStack* state_before,
+               bool check_boolean, bool mismatched = false)
+  : AccessIndexed(array, index, length, elt_type, state_before, mismatched)
   , _value(value), _profiled_method(NULL), _profiled_bci(0), _check_boolean(check_boolean)
   {
     set_flag(NeedsWriteBarrierFlag, (as_ValueType(elt_type)->is_object()));
diff -r ec2d5ec5571c -r d139a133ba27 hotspot/test/compiler/stable/TestStableMismatched.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/compiler/stable/TestStableMismatched.java	Tue Jun 07 18:20:44 2016 +0200
@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016, 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 TestStableMismatched
+ * @bug 8158228
+ * @summary Tests if mismatched char load from stable byte[] returns correct result
+ * @run main/othervm -XX:-CompactStrings -XX:TieredStopAtLevel=1 -Xcomp
+ *                   -XX:CompileOnly=TestStableMismatched::test,::charAt
+ *                   TestStableMismatched
+ * @run main/othervm -XX:-CompactStrings -XX:-TieredCompilation -Xcomp
+ *                   -XX:CompileOnly=TestStableMismatched::test,::charAt
+ *                   TestStableMismatched
+ */
+public class TestStableMismatched {
+    public static void main(String args[]) {
+        test();
+    }
+
+    public static void test() {
+        String text = "abcdefg";
+        // Mismatched char load from @Stable byte[] String.value field
+        char returned = text.charAt(6);
+        if (returned != 'g') {
+            throw new RuntimeException("failed: charAt(6) returned '" + returned + "' instead of 'g'");
+        }
+    }
+}
+