Run Crankshaft on a separate thread.

src/runtime-profiler.cc

Index: src/runtime-profiler.cc
diff --git a/src/runtime-profiler.cc b/src/runtime-profiler.cc
index 568e48e412c03f4151f6fb9ae30323efd0a0182b..eaf0735c4aa6b02d3c493cf308b5397e7c4660e4 100644
--- a/src/runtime-profiler.cc
+++ b/src/runtime-profiler.cc
@@ -131,6 +131,13 @@ static void GetICCounts(JSFunction* function,
 
 void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
   ASSERT(function->IsOptimizable());
+
+  if (FLAG_concurrent_crankshaft && !(isolate_->context() == NULL ||

[danno, 2012/05/22 10:32:19]

I don't see why this is necessary, can you explain in more detail?

[sanjoy, 2012/05/22 11:38:55]

Sometimes this function is called with the context slot set to a non-context. 
You can check this by putting ASSERT(!isolate_->context() ||
isolate_->context()->IsContext()); here and running the unit tests in debug
mode.

I'll put in a more detailed comment in the second iteration.

+                                      isolate_->context()->IsContext())) {
+    // This confuses the compiler thread
+    return;
+  }
+
   if (FLAG_trace_opt) {
     PrintF("[marking ");
     function->PrintName();
@@ -144,8 +151,10 @@ void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
     PrintF("]\n");
   }
 
-  // The next call to the function will trigger optimization.
-  function->MarkForLazyRecompilation();
+  if (FLAG_concurrent_crankshaft)
+    function->CompileConcurrently();
+  else
+    function->MarkForLazyRecompilation();
 }