Use a root array register for constant loads and stack guards on x64....

src/heap.h

 // Copyright 2006-2008 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
@@ skipping 17 matching lines @@
 #ifndef V8_HEAP_H_
 #define V8_HEAP_H_
 
 #include "zone-inl.h"
 
 namespace v8 {
 namespace internal {
 
 // Defines all the roots in Heap.
 #define STRONG_ROOT_LIST(V)                                                    \
+  /* Cluster the most popular ones in a few cache lines here at the top. */    \
+  V(Smi, stack_limit, StackLimit)                                              \
+  V(Object, undefined_value, UndefinedValue)                                   \
+  V(Object, the_hole_value, TheHoleValue)                                      \
+  V(Object, null_value, NullValue)                                             \
+  V(Object, true_value, TrueValue)                                             \
+  V(Object, false_value, FalseValue)                                           \
+  V(Map, heap_number_map, HeapNumberMap)                                       \
+  V(Map, global_context_map, GlobalContextMap)                                 \
+  V(Map, fixed_array_map, FixedArrayMap)                                       \
+  V(Object, no_interceptor_result_sentinel, NoInterceptorResultSentinel)       \
   V(Map, meta_map, MetaMap)                                                    \
-  V(Map, heap_number_map, HeapNumberMap)                                       \
+  V(Object, termination_exception, TerminationException)                       \
+  V(Map, hash_table_map, HashTableMap)                                         \
+  V(FixedArray, empty_fixed_array, EmptyFixedArray)                            \
   V(Map, short_string_map, ShortStringMap)                                     \
   V(Map, medium_string_map, MediumStringMap)                                   \
   V(Map, long_string_map, LongStringMap)                                       \
   V(Map, short_ascii_string_map, ShortAsciiStringMap)                          \
   V(Map, medium_ascii_string_map, MediumAsciiStringMap)                        \
   V(Map, long_ascii_string_map, LongAsciiStringMap)                            \
   V(Map, short_symbol_map, ShortSymbolMap)                                     \
   V(Map, medium_symbol_map, MediumSymbolMap)                                   \
   V(Map, long_symbol_map, LongSymbolMap)                                       \
   V(Map, short_ascii_symbol_map, ShortAsciiSymbolMap)                          \
@@ skipping 38 matching lines @@
   V(Map, undetectable_short_string_map, UndetectableShortStringMap)            \
   V(Map, undetectable_medium_string_map, UndetectableMediumStringMap)          \
   V(Map, undetectable_long_string_map, UndetectableLongStringMap)              \
   V(Map, undetectable_short_ascii_string_map, UndetectableShortAsciiStringMap) \
   V(Map,                                                                       \
     undetectable_medium_ascii_string_map,                                      \
     UndetectableMediumAsciiStringMap)                                          \
   V(Map, undetectable_long_ascii_string_map, UndetectableLongAsciiStringMap)   \
   V(Map, byte_array_map, ByteArrayMap)                                         \
   V(Map, pixel_array_map, PixelArrayMap)                                       \
-  V(Map, fixed_array_map, FixedArrayMap)                                       \
-  V(Map, hash_table_map, HashTableMap)                                         \
   V(Map, context_map, ContextMap)                                              \
   V(Map, catch_context_map, CatchContextMap)                                   \
-  V(Map, global_context_map, GlobalContextMap)                                 \
   V(Map, code_map, CodeMap)                                                    \
   V(Map, oddball_map, OddballMap)                                              \
   V(Map, global_property_cell_map, GlobalPropertyCellMap)                      \
   V(Map, boilerplate_function_map, BoilerplateFunctionMap)                     \
   V(Map, shared_function_info_map, SharedFunctionInfoMap)                      \
   V(Map, proxy_map, ProxyMap)                                                  \
   V(Map, one_pointer_filler_map, OnePointerFillerMap)                          \
   V(Map, two_pointer_filler_map, TwoPointerFillerMap)                          \
   V(Object, nan_value, NanValue)                                               \
-  V(Object, undefined_value, UndefinedValue)                                   \
-  V(Object, no_interceptor_result_sentinel, NoInterceptorResultSentinel)       \
-  V(Object, termination_exception, TerminationException)                       \
   V(Object, minus_zero_value, MinusZeroValue)                                  \
-  V(Object, null_value, NullValue)                                             \
-  V(Object, true_value, TrueValue)                                             \
-  V(Object, false_value, FalseValue)                                           \
   V(String, empty_string, EmptyString)                                         \
-  V(FixedArray, empty_fixed_array, EmptyFixedArray)                            \
   V(DescriptorArray, empty_descriptor_array, EmptyDescriptorArray)             \
-  V(Object, the_hole_value, TheHoleValue)                                      \
   V(Map, neander_map, NeanderMap)                                              \
   V(JSObject, message_listeners, MessageListeners)                             \
   V(Proxy, prototype_accessors, PrototypeAccessors)                            \
   V(NumberDictionary, code_stubs, CodeStubs)                                   \
   V(NumberDictionary, non_monomorphic_cache, NonMonomorphicCache)              \
   V(Code, js_entry_code, JsEntryCode)                                          \
   V(Code, js_construct_entry_code, JsConstructEntryCode)                       \
   V(Code, c_entry_code, CEntryCode)                                            \
   V(Code, c_entry_debug_break_code, CEntryDebugBreakCode)                      \
   V(FixedArray, number_string_cache, NumberStringCache)                        \
   V(FixedArray, single_character_string_cache, SingleCharacterStringCache)     \
   V(FixedArray, natives_source_cache, NativesSourceCache)                      \
   V(Object, last_script_id, LastScriptId)                                      \
-  V(Smi, stack_limit, StackLimit)
 
 
 #define ROOT_LIST(V)                                  \
   STRONG_ROOT_LIST(V)                                 \
   V(SymbolTable, symbol_table, SymbolTable)
 
 #define SYMBOL_LIST(V)                                                   \
   V(Array_symbol, "Array")                                               \
   V(Object_symbol, "Object")                                             \
   V(Proto_symbol, "__proto__")                                           \
@@ skipping 1358 matching lines @@
   int marked_count_;
 
   // The count from the end of the previous full GC.  Will be zero if there
   // was no previous full GC.
   int previous_marked_count_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_