Add an intrinsified early out path for Dart timeline calls

runtime/vm/intrinsifier_ia32.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // The intrinsic code below is executed before a method has built its frame.
 // The return address is on the stack and the arguments below it.
 // Registers EDX (arguments descriptor) and ECX (function) must be preserved.
 // Each intrinsification method returns true if the corresponding
 // Dart method was intrinsified.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/os.h"
 #include "vm/regexp_assembler.h"
 #include "vm/symbols.h"
+#include "vm/timeline.h"
 
 namespace dart {
 
 // When entering intrinsics code:
 // ECX: IC Data
 // EDX: Arguments descriptor
 // TOS: Return address
 // The ECX, EDX registers can be destroyed only if there is no slow-path, i.e.
 // if the intrinsified method always executes a return.
 // The EBP register should not be modified, because it is used by the profiler.
@@ skipping 2090 matching lines @@
   __ ret();
 }
 
 
 void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
   __ LoadIsolate(EAX);
   __ movl(EAX, Address(EAX, Isolate::current_tag_offset()));
   __ ret();
 }
 
+
+void Intrinsifier::Timeline_isDartStreamEnabled(Assembler* assembler) {
+  if (!FLAG_support_timeline) {
+    __ LoadObject(EAX, Bool::False());
+    __ ret();
+    return;
+  }
+  Label true_label;
+  // Load TimelineStream*.
+  __ movl(EAX, Address(THR, Thread::dart_stream_offset()));
+  // Load uintptr_t from TimelineStream*.
+  __ movl(EAX, Address(EAX, TimelineStream::enabled_offset()));
+  __ cmpl(EAX, Immediate(0));
+  __ j(NOT_ZERO, &true_label, Assembler::kNearJump);
+  // Not enabled.
+  __ LoadObject(EAX, Bool::False());
+  __ ret();
+  // Enabled.
+  __ Bind(&true_label);
+  __ LoadObject(EAX, Bool::True());
+  __ ret();
+}
+
 #undef __
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32