Reviewers: Feng Qian,

Description:
Fix for issue 171:
- Make sure to not destroy the instance type by slightly rearranging the
code.
- Added regression test.


Please review this at http://codereview.chromium.org/16594

SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/

Affected files:
   M     src/stub-cache-arm.cc
   A     test/mjsunit/regress/regress-171.js


Index: test/mjsunit/regress/regress-171.js
===================================================================
--- test/mjsunit/regress/regress-171.js (revision 0)
+++ test/mjsunit/regress/regress-171.js (revision 0)
@@ -0,0 +1,41 @@
+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+function f(s) { return s.length; }
+function g(s, key) { return s[key]; }
+
+assertEquals(f(new String("a")), 1);
+assertEquals(f(new String("a")), 1);
+assertEquals(f(new String("a")), 1);
+assertEquals(f("a"), 1);
+assertEquals(f(new String("a")), 1);
+
+assertEquals(g(new String("a"), "length"), 1);
+assertEquals(g(new String("a"), "length"), 1);
+assertEquals(g(new String("a"), "length"), 1);
+assertEquals(g("a", "length"), 1);
+assertEquals(g(new String("a"), "length"), 1);

Property changes on: test/mjsunit/regress/regress-171.js
___________________________________________________________________
Name: svn:eol-style
    + native

Index: src/stub-cache-arm.cc
===================================================================
--- src/stub-cache-arm.cc       (revision 1041)
+++ src/stub-cache-arm.cc       (working copy)
@@ -317,15 +317,15 @@
                                               Register scratch1,
                                               Register scratch2,
                                               Label* miss) {
-  Label load_length, check_wrapper;
+  Label check_string, check_wrapper;

+  __ bind(&check_string);
    // Check if the object is a string leaving the instance type in the
    // scratch1 register.
    GenerateStringCheck(masm, receiver, scratch1, scratch2,
                        miss, &check_wrapper);

    // Load length directly from the string.
-  __ bind(&load_length);
    __ and_(scratch1, scratch1, Operand(kStringSizeMask));
    __ add(scratch1, scratch1, Operand(String::kHashShift));
    __ ldr(r0, FieldMemOperand(receiver, String::kLengthOffset));
@@ -338,11 +338,9 @@
    __ cmp(scratch1, Operand(JS_VALUE_TYPE));
    __ b(ne, miss);

-  // Check if the wrapped value is a string and load the length
-  // directly if it is.
-  __ ldr(r0, FieldMemOperand(receiver, JSValue::kValueOffset));
-  GenerateStringCheck(masm, receiver, scratch1, scratch1, miss, miss);
-  __ b(&load_length);
+  // Unwrap the value in place and check if the wrapped value is a string.
+  __ ldr(receiver, FieldMemOperand(receiver, JSValue::kValueOffset));
+  __ b(&check_string);
  }





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