More precompiled snapshotting.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index a0f8584168dfbe011c6d4cb3eb835c5d8fb3d1f3..267702aa081345700e78f2f69ae315272245ccfb 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -119,12 +119,14 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
     ASSERT(vm_isolate_ == NULL);
     ASSERT(Flags::Initialized());
     const bool is_vm_isolate = true;
+    const bool precompiled = instructions_snapshot != NULL;
 
     // Setup default flags for the VM isolate.
     Isolate::Flags vm_flags;
     Dart_IsolateFlags api_flags;
     vm_flags.CopyTo(&api_flags);
     vm_isolate_ = Isolate::Init("vm-isolate", api_flags, is_vm_isolate);
+    vm_isolate_->set_compilation_allowed(!precompiled);
     // Verify assumptions about executing in the VM isolate.
     ASSERT(vm_isolate_ == Isolate::Current());
     ASSERT(vm_isolate_ == Thread::Current()->isolate());
@@ -136,10 +138,11 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
     TargetCPUFeatures::InitOnce();
     Object::InitOnce(vm_isolate_);
     ArgumentsDescriptor::InitOnce();
-    StubCode::InitOnce();
-    Thread::InitOnceAfterObjectAndStubCode();
-    // Now that the needed stub has been generated, set the stack limit.
-    vm_isolate_->InitializeStackLimit();
+    if (precompiled) {
+      // Stub code loaded from snapshot.
+    } else {
+      StubCode::InitOnce();
+    }

[siva, 2015/09/14 20:32:59]

Would read better as:

// When precompiling the stub code is initialized from the snapshot.
if (!precompiled) {
  StubCode::InitOnce();
}

[rmacnak, 2015/09/15 17:56:42]

Done.

     if (vm_isolate_snapshot != NULL) {
       const Snapshot* snapshot = Snapshot::SetupFromBuffer(vm_isolate_snapshot);
       if (snapshot == NULL) {
@@ -168,6 +171,9 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
     } else {
       Symbols::InitOnce(vm_isolate_);

[siva, 2015/09/14 20:32:59]

Maybe the if (!precompiled) check from above should go here, isn;t it true that
if precompiling (vm_isolate_snapshot != NULL) should be true.

[rmacnak, 2015/09/15 17:56:42]

Yes, precompiled implies there is a vm isolate snapshot.

     }
+    Thread::InitOnceAfterObjectAndStubCode();
+    // Now that the needed stub has been generated, set the stack limit.
+    vm_isolate_->InitializeStackLimit();
     Scanner::InitOnce();
 #if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
     // Dart VM requires at least SSE2.