JavaScriptCore-1097.3.tar.gz

[apple/javascriptcore.git] / heap / WriteBarrierSupport.h

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+/*
+ * Copyright (C) 2011 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WriteBarrierSupport_h
+#define WriteBarrierSupport_h
+
+#include "SamplingCounter.h"
+#include <wtf/Assertions.h>
+
+namespace JSC {
+
+// This allows the JIT to distinguish between uses of the barrier for different
+// kinds of writes. This is used by the JIT for profiling, and may be appropriate
+// for allowing the GC implementation to specialize the JIT's write barrier code
+// for different kinds of target objects.
+enum WriteBarrierUseKind {
+    // This allows specialization for access to the property storage (either
+    // array element or property), but not for any other kind of property
+    // accesses (such as writes that are a consequence of setter execution).
+    WriteBarrierForPropertyAccess,
+    
+    // This allows specialization for variable accesses (such as global or
+    // scoped variables).
+    WriteBarrierForVariableAccess,
+    
+    // This captures all other forms of write barriers. It should always be
+    // correct to use a generic access write barrier, even when storing to
+    // properties. Hence, if optimization is not necessary, it is preferable
+    // to just use a generic access.
+    WriteBarrierForGenericAccess
+};
+
+class WriteBarrierCounters {
+private:
+    WriteBarrierCounters() { }
+
+public:
+#if ENABLE(WRITE_BARRIER_PROFILING)
+    static GlobalSamplingCounter usesWithBarrierFromCpp;
+    static GlobalSamplingCounter usesWithoutBarrierFromCpp;
+    static GlobalSamplingCounter usesWithBarrierFromJit;
+    static GlobalSamplingCounter usesForPropertiesFromJit;
+    static GlobalSamplingCounter usesForVariablesFromJit;
+    static GlobalSamplingCounter usesWithoutBarrierFromJit;
+    
+    static void initialize();
+    
+    static GlobalSamplingCounter& jitCounterFor(WriteBarrierUseKind useKind)
+    {
+        switch (useKind) {
+        case WriteBarrierForPropertyAccess:
+            return usesForPropertiesFromJit;
+        case WriteBarrierForVariableAccess:
+            return usesForVariablesFromJit;
+        default:
+            ASSERT(useKind == WriteBarrierForGenericAccess);
+            return usesWithBarrierFromJit;
+        }
+    }
+#else
+    // These are necessary to work around not having conditional exports.
+    JS_EXPORTDATA static char usesWithBarrierFromCpp;
+    JS_EXPORTDATA static char usesWithoutBarrierFromCpp;
+#endif // ENABLE(WRITE_BARRIER_PROFILING)
+
+    static void countWriteBarrier()
+    {
+#if ENABLE(WRITE_BARRIER_PROFILING)
+        WriteBarrierCounters::usesWithBarrierFromCpp.count();
+#endif
+    }
+};
+
+} // namespace JSC
+
+#endif // WriteBarrierSupport_h
+