Remove fixed contant pool entries by caching some global constants in Thread

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index ba6db93eacd7aeb166d49bbcbba0c59c8719d911..f460ee99bb8aa70448942898e922fe64288a14e3 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -5,8 +5,10 @@
 #include "vm/thread.h"
 
 #include "vm/isolate.h"
+#include "vm/object.h"
 #include "vm/os_thread.h"
 #include "vm/profiler.h"
+#include "vm/stub_code.h"
 #include "vm/thread_interrupter.h"
 
 
@@ -23,10 +25,21 @@ static void DeleteThread(void* thread) {
 }
 
 
-void Thread::InitOnce() {
+void Thread::InitOnceBeforeIsolate() {
   ASSERT(thread_key_ == OSThread::kUnsetThreadLocalKey);
   thread_key_ = OSThread::CreateThreadLocal(DeleteThread);
   ASSERT(thread_key_ != OSThread::kUnsetThreadLocalKey);
+  ASSERT(Thread::Current() == NULL);
+  // Postpone initialization of VM constants for this first thread.
+  SetCurrent(new Thread(false));
+}
+
+
+void Thread::InitOnceAfterObjectAndStubCode() {
+  Thread* thread = Thread::Current();
+  ASSERT(thread != NULL);
+  ASSERT(thread->isolate() == Dart::vm_isolate());
+  thread->InitVMConstants();
 }
 
 
@@ -53,6 +66,31 @@ void Thread::CleanUp() {
 #endif
 
 
+Thread::Thread(bool init_vm_constants)
+    : isolate_(NULL),
+      store_buffer_block_(NULL),
+      object_null_(NULL),
+      bool_true_(NULL),
+      bool_false_(NULL),
+      update_store_buffer_entry_point_(0) {
+  if (init_vm_constants) {
+    InitVMConstants();
+  }
+}
+
+
+void Thread::InitVMConstants() {
+  ASSERT(object_null_ == NULL);
+  object_null_ = Object::null();
+  ASSERT(bool_true_ == NULL);
+  bool_true_ = Object::bool_true().raw();
+  ASSERT(bool_false_ == NULL);
+  bool_false_ = Object::bool_false().raw();
+  ASSERT(update_store_buffer_entry_point_ == 0);
+  update_store_buffer_entry_point_ = StubCode::UpdateStoreBufferEntryPoint();
+}
+
+
 void Thread::EnterIsolate(Isolate* isolate) {
   Thread* thread = Thread::Current();
   ASSERT(thread != NULL);
@@ -168,4 +206,25 @@ void Thread::set_cha(CHA* value) {
   isolate_->cha_ = value;
 }
 
+
+bool Thread::CanLoadFromThread(const Object& object) {
+  return (object.raw() == Object::null())
+      || (object.raw() == Bool::True().raw())

[koda, 2015/07/07 13:43:57]

It would be safer to connect this with the code that initializes the cache.
Perhaps making this a non-static method that compares to the actual fields
instead?

Or, if we expect to add more of these in the future, a visitor macro pattern
(type + field name + value expression, for each constant). That would minimize
risk of copy-paste errors, but might be overkill though.

At least, please use same expression for each value (Bool::True vs
Object::bool_true, etc.) in this file.

[Florian Schneider, 2015/07/08 09:28:09]

Macro sounds good since there are a few of places to keep in sync.

+      || (object.raw() == Bool::False().raw());
+}
+
+
+intptr_t Thread::OffsetFromThread(const Object& object) {

[koda, 2015/07/07 13:43:57]

ASSERT(CanLoadFromThread)

[Florian Schneider, 2015/07/08 09:28:09]

Done.

+  if (object.raw() == Object::null()) {
+    return Thread::object_null_offset();
+  } else if (object.raw() == Bool::True().raw()) {
+    return Thread::bool_true_offset();
+  } else if (object.raw() == Bool::False().raw()) {
+    return Thread::bool_false_offset();
+  } else {
+    UNREACHABLE();
+    return -1;
+  }
+}
+
 }  // namespace dart