Introduce "optimized_out" oddball marker for compilers.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 2311 matching lines @@
     ALLOCATE_MAP(FOREIGN_TYPE, Foreign::kSize, foreign)
 
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, the_hole);
     ALLOCATE_PRIMITIVE_MAP(ODDBALL_TYPE, Oddball::kSize, boolean,
                            Context::BOOLEAN_FUNCTION_INDEX);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, uninitialized);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, arguments_marker);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, no_interceptor_result_sentinel);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, exception);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, termination_exception);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, optimized_out);
 
     for (unsigned i = 0; i < arraysize(string_type_table); i++) {
       const StringTypeTable& entry = string_type_table[i];
       {
         AllocationResult allocation = AllocateMap(entry.type, entry.size);
         if (!allocation.To(&obj)) return false;
       }
       Map* map = Map::cast(obj);
       map->SetConstructorFunctionIndex(Context::STRING_FUNCTION_INDEX);
       // Mark cons string maps as unstable, because their objects can change
@@ skipping 351 matching lines @@
 
   set_termination_exception(*factory->NewOddball(
       factory->termination_exception_map(), "termination_exception",
       handle(Smi::FromInt(-3), isolate()), false, "undefined",
       Oddball::kOther));
 
   set_exception(*factory->NewOddball(factory->exception_map(), "exception",
                                      handle(Smi::FromInt(-5), isolate()), false,
                                      "undefined", Oddball::kException));
 
+  set_optimized_out(
+      *factory->NewOddball(factory->optimized_out_map(), "optimized_out",
+                           handle(Smi::FromInt(-6), isolate()), false,
+                           "undefined", Oddball::kOptimizedOut));
+
   for (unsigned i = 0; i < arraysize(constant_string_table); i++) {
     Handle<String> str =
         factory->InternalizeUtf8String(constant_string_table[i].contents);
     roots_[constant_string_table[i].index] = *str;
   }
 
   // Create the code_stubs dictionary. The initial size is set to avoid
   // expanding the dictionary during bootstrapping.
   set_code_stubs(*UnseededNumberDictionary::New(isolate(), 128));
 
@@ skipping 3684 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8