Fix for issue 171:

- Make sure to not destroy the instance type by slightly rearranging the code.
- Added regression test.

Review URL: http://codereview.chromium.org/16594

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1042 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/stub-cache-arm.cc

@@ -312,20 +312,24 @@ static void GenerateStringCheck(MacroAssembler* masm,
 }
 
 
+// Generate code to load the length from a string object and return the length.
+// If the receiver object is not a string or a wrapped string object the
+// execution continues at the miss label. The register containing the
+// receiver is potentially clobbered.
 void StubCompiler::GenerateLoadStringLength2(MacroAssembler* masm,
                                              Register receiver,
                                              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 +342,9 @@ void StubCompiler::GenerateLoadStringLength2(MacroAssembler* masm,
   __ 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);
 }
 
 

test/mjsunit/regress/regress-171.js

+// 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);