Bug 927516 - Bump Ion script size limit for DOM workers. r=bhackett

dom/workers/RuntimeService.cpp

@@ -805,6 +805,8 @@ CreateJSContextForWorker(WorkerPrivate* aWorkerPrivate, JSRuntime* aRuntime)
     }
   }
 
+  JS_SetIsWorkerRuntime(aRuntime);
+
   JS_SetNativeStackQuota(aRuntime, WORKER_CONTEXT_NATIVE_STACK_LIMIT);
 
   // Security policy:

js/src/jit/Ion.cpp

@@ -1740,10 +1740,15 @@ CheckScript(JSContext *cx, JSScript *script, bool osr)
 
 // Longer scripts can only be compiled off thread, as these compilations
 // can be expensive and stall the main thread for too long.
-static const uint32_t MAX_OFF_THREAD_SCRIPT_SIZE = 100000;
-static const uint32_t MAX_MAIN_THREAD_SCRIPT_SIZE = 2000;
+static const uint32_t MAX_OFF_THREAD_SCRIPT_SIZE = 100 * 1000;
+static const uint32_t MAX_MAIN_THREAD_SCRIPT_SIZE = 2 * 1000;
 static const uint32_t MAX_MAIN_THREAD_LOCALS_AND_ARGS = 256;
 
+// DOM Worker runtimes don't have off thread compilation, but can also compile
+// larger scripts since this doesn't stall the main thread.
+static const uint32_t MAX_DOM_WORKER_SCRIPT_SIZE = 16 * 1000;
+static const uint32_t MAX_DOM_WORKER_LOCALS_AND_ARGS = 2048;
+
 static MethodStatus
 CheckScriptSize(JSContext *cx, JSScript* script)
 {
@@ -1757,6 +1762,21 @@ CheckScriptSize(JSContext *cx, JSScript* script)
     }
 
     uint32_t numLocalsAndArgs = analyze::TotalSlots(script);
+    if (cx->runtime()->isWorkerRuntime()) {
+        // DOM Workers don't have off thread compilation enabled. Since workers
+        // don't block the browser's event loop, allow them to compile larger
+        // scripts.
+        JS_ASSERT(!OffThreadIonCompilationEnabled(cx->runtime()));
+
+        if (script->length > MAX_DOM_WORKER_SCRIPT_SIZE ||
+            numLocalsAndArgs > MAX_DOM_WORKER_LOCALS_AND_ARGS)
+        {
+            return Method_CantCompile;
+        }
+
+        return Method_Compiled;
+    }
+
     if (script->length > MAX_MAIN_THREAD_SCRIPT_SIZE ||
         numLocalsAndArgs > MAX_MAIN_THREAD_LOCALS_AND_ARGS)
     {

js/src/jsfriendapi.cpp

@@ -73,6 +73,12 @@ JS_GetAnonymousString(JSRuntime *rt)
     return rt->atomState.anonymous;
 }
 
+JS_FRIEND_API(void)
+JS_SetIsWorkerRuntime(JSRuntime *rt)
+{
+    rt->setIsWorkerRuntime();
+}
+
 JS_FRIEND_API(JSObject *)
 JS_FindCompilationScope(JSContext *cx, JSObject *objArg)
 {

js/src/jsfriendapi.h

@@ -48,6 +48,9 @@ JS_SetGrayGCRootsTracer(JSRuntime *rt, JSTraceDataOp traceOp, void *data);
 extern JS_FRIEND_API(JSString *)
 JS_GetAnonymousString(JSRuntime *rt);
 
+extern JS_FRIEND_API(void)
+JS_SetIsWorkerRuntime(JSRuntime *rt);
+
 extern JS_FRIEND_API(JSObject *)
 JS_FindCompilationScope(JSContext *cx, JSObject *obj);
 

js/src/vm/Runtime.cpp

@@ -286,7 +286,8 @@ JSRuntime::JSRuntime(JSUseHelperThreads useHelperThreads)
     useHelperThreads_(useHelperThreads),
     requestedHelperThreadCount(-1),
     useHelperThreadsForIonCompilation_(true),
-    useHelperThreadsForParsing_(true)
+    useHelperThreadsForParsing_(true),
+    isWorkerRuntime_(false)
 #ifdef DEBUG
     , enteredPolicy(nullptr)
 #endif

js/src/vm/Runtime.h

@@ -1695,6 +1695,9 @@ struct JSRuntime : public JS::shadow::Runtime,
     bool useHelperThreadsForIonCompilation_;
     bool useHelperThreadsForParsing_;
 
+    // True iff this is a DOM Worker runtime.
+    bool isWorkerRuntime_;
+
   public:
 
     bool useHelperThreads() const {
@@ -1735,6 +1738,12 @@ struct JSRuntime : public JS::shadow::Runtime,
     bool useHelperThreadsForParsing() const {
         return useHelperThreadsForParsing_;
     }
+    void setIsWorkerRuntime() {
+        isWorkerRuntime_ = true;
+    }
+    bool isWorkerRuntime() const {
+        return isWorkerRuntime_;
+    }
 
 #ifdef DEBUG
   public: