Unify the IsShortcutCandidate predicate.

src/objects.h

 // 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/builtins.h"
@@ skipping 601 matching lines @@
 const uint32_t kOneByteDataHintMask = 0x08;
 const uint32_t kOneByteDataHintTag = 0x08;
 
 // If bit 7 is clear and string representation indicates an external string,
 // then bit 4 indicates whether the data pointer is cached.
 const uint32_t kShortExternalStringMask = 0x10;
 const uint32_t kShortExternalStringTag = 0x10;
 
 
 // A ConsString with an empty string as the right side is a candidate
-// for being shortcut by the garbage collector unless it is internalized.
-// It's not common to have non-flat internalized strings, so we do not
-// shortcut them thereby avoiding turning internalized strings into strings.
-// See heap.cc and mark-compact.cc.
+// for being shortcut by the garbage collector. We don't allocate any
+// non-flat internalized strings, so we do not shortcut them thereby
+// avoiding turning internalized strings into strings. The bit-masks
+// below contain the internalized bit as additional safety.
+// See heap.cc, mark-compact.cc and objects-visiting.cc.
 const uint32_t kShortcutTypeMask =
     kIsNotStringMask |
     kIsNotInternalizedMask |
     kStringRepresentationMask;
 const uint32_t kShortcutTypeTag = kConsStringTag | kNotInternalizedTag;
 
+static inline bool IsShortcutCandidate(int type) {
+  return ((type & kShortcutTypeMask) == kShortcutTypeTag);
+}
+
 
 enum InstanceType {
   // String types.
   INTERNALIZED_STRING_TYPE = kTwoByteStringTag | kSeqStringTag
       | kInternalizedTag,
   ASCII_INTERNALIZED_STRING_TYPE = kOneByteStringTag | kSeqStringTag
       | kInternalizedTag,
   EXTERNAL_INTERNALIZED_STRING_TYPE = kTwoByteStringTag | kExternalStringTag
       | kInternalizedTag,
   EXTERNAL_ASCII_INTERNALIZED_STRING_TYPE = kOneByteStringTag
@@ skipping 10587 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_