JavaScriptCore-7600.1.4.9.tar.gz

[apple/javascriptcore.git] / runtime / StackAlignment.h

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+/*
+ * Copyright (C) 2013 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. ``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
+ * 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 StackAlignment_h
+#define StackAlignment_h
+
+#include "JSCJSValue.h"
+#include "JSStack.h"
+#include <wtf/MathExtras.h>
+
+namespace JSC {
+
+// NB. Different platforms may have different requirements here. But 16 bytes is very common.
+inline unsigned stackAlignmentBytes() { return 16; }
+
+inline unsigned stackAlignmentRegisters()
+{
+    return stackAlignmentBytes() / sizeof(EncodedJSValue);
+}
+
+// Align argument count taking into account the CallFrameHeaderSize may be
+// an "unaligned" count of registers.
+inline unsigned roundArgumentCountToAlignFrame(unsigned argumentCount)
+{
+    return WTF::roundUpToMultipleOf(stackAlignmentRegisters(), argumentCount + JSStack::CallFrameHeaderSize) - JSStack::CallFrameHeaderSize;
+}
+
+// Align local register count to make the last local end on a stack aligned address given the
+// CallFrame is at an address that is stack aligned minus JSStack::CallerFrameAndPCSize
+inline unsigned roundLocalRegisterCountForFramePointerOffset(unsigned localRegisterCount)
+{
+    return WTF::roundUpToMultipleOf(stackAlignmentRegisters(), localRegisterCount + JSStack::CallerFrameAndPCSize) - JSStack::CallerFrameAndPCSize;
+}
+
+inline unsigned logStackAlignmentRegisters()
+{
+    return WTF::fastLog2(stackAlignmentRegisters());
+}
+
+} // namespace JSC
+
+#endif // StackAlignment_h
+