Tag stubs that rely on instance types as MEGAMORPHIC.

BUG=chromium:173974

Review URL: https://chromiumcodereview.appspot.com/12178017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13586 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/builtins.h

@@ -145,7 +145,7 @@ enum BuiltinExtraArguments {
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_Generic,            KEYED_LOAD_IC, GENERIC,             \
                                     Code::kNoExtraICState)              \
-  V(KeyedLoadIC_String,             KEYED_LOAD_IC, MONOMORPHIC,         \
+  V(KeyedLoadIC_String,             KEYED_LOAD_IC, MEGAMORPHIC,         \
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_IndexedInterceptor, KEYED_LOAD_IC, MONOMORPHIC,         \
                                     Code::kNoExtraICState)              \

src/code-stubs.h

@@ -549,7 +549,12 @@ class ICStub: public PlatformCodeStub {
  public:
   explicit ICStub(Code::Kind kind) : kind_(kind) { }
   virtual int GetCodeKind() { return kind_; }
-  virtual InlineCacheState GetICState() { return MONOMORPHIC; }
+  // Currently all IC stubs do not collect explicit type feedback but rather
+  // check the instance type.
+  // TODO(verwaest): These stubs should collect proper type feedback, and should
+  // not check the instance type explicitly (perhaps unless more than
+  // kMaxPolymorphism maps are recorded).
+  virtual InlineCacheState GetICState() { return MEGAMORPHIC; }
 
   bool Describes(Code* code) {
     return GetMajorKey(code) == MajorKey() && code->stub_info() == MinorKey();

test/mjsunit/regress/regress-crbug-173974.js

+// Copyright 2013 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.
+
+// Flags: --allow-natives-syntax
+
+function f() {
+  var count = "";
+  count[0] --;
+}
+f();
+%OptimizeFunctionOnNextCall(f);
+f();