Introduce intrinsic to expose debug state to generated code.

src/hydrogen.cc

 // Copyright 2013 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.
 
 #include "src/hydrogen.h"
 
 #include <algorithm>
 
 #include "src/v8.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 11690 matching lines @@
 }
 
 
 void HOptimizedGraphBuilder::GenerateDebugBreakInOptimizedCode(
     CallRuntime* call) {
   Add<HDebugBreak>();
   return ast_context()->ReturnValue(graph()->GetConstant0());
 }
 
 
-void HOptimizedGraphBuilder::GenerateDebugCallbackSupportsStepping(
-    CallRuntime* call) {
-  ASSERT(call->arguments()->length() == 1);
-  // Debugging is not supported in optimized code.
-  return ast_context()->ReturnValue(graph()->GetConstantFalse());
+void HOptimizedGraphBuilder::GenerateDebugIsActive(CallRuntime* call) {
+  ASSERT(call->arguments()->length() == 0);
+  HValue* ref =
+      Add<HConstant>(ExternalReference::debug_is_active_address(isolate()));
+  HValue* value = Add<HLoadNamedField>(
+      ref, static_cast<HValue*>(NULL), HObjectAccess::ForExternalUInteger8());
+  return ast_context()->ReturnValue(value);
 }
 
 
 #undef CHECK_BAILOUT
 #undef CHECK_ALIVE
 
 
 HEnvironment::HEnvironment(HEnvironment* outer,
                            Scope* scope,
                            Handle<JSFunction> closure,
@@ skipping 618 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal