diff -r 000000000000 -r 6474c204b198 js/src/yarr/OSAllocator.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/yarr/OSAllocator.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ *
+ * ***** BEGIN LICENSE BLOCK *****
+ * Copyright (C) 2010 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.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef yarr_OSAllocator_h
+#define yarr_OSAllocator_h
+
+#include <stdlib.h>
+#include "yarr/wtfbridge.h"
+#include "assembler/wtf/VMTags.h"
+#include "assembler/wtf/Assertions.h"
+
+namespace WTF {
+
+class OSAllocator {
+public:
+    enum Usage {
+        UnknownUsage = -1,
+        FastMallocPages = VM_TAG_FOR_TCMALLOC_MEMORY,
+        JSGCHeapPages = VM_TAG_FOR_COLLECTOR_MEMORY,
+        JSVMStackPages = VM_TAG_FOR_REGISTERFILE_MEMORY,
+        JSJITCodePages = VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY
+    };
+
+    // These methods are symmetric; reserveUncommitted allocates VM in an uncommitted state,
+    // releaseDecommitted should be called on a region of VM allocated by a single reservation,
+    // the memory must all currently be in a decommitted state.
+    static void* reserveUncommitted(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false);
+    static void releaseDecommitted(void*, size_t);
+
+    // These methods are symmetric; they commit or decommit a region of VM (uncommitted VM should
+    // never be accessed, since the OS may not have attached physical memory for these regions).
+    // Clients should only call commit on uncommitted regions and decommit on committed regions.
+    static void commit(void*, size_t, bool writable, bool executable);
+    static void decommit(void*, size_t);
+
+    // These methods are symmetric; reserveAndCommit allocates VM in an committed state,
+    // decommitAndRelease should be called on a region of VM allocated by a single reservation,
+    // the memory must all currently be in a committed state.
+    static void* reserveAndCommit(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false);
+    static void decommitAndRelease(void* base, size_t size);
+
+    // These methods are akin to reserveAndCommit/decommitAndRelease, above - however rather than
+    // committing/decommitting the entire region additional parameters allow a subregion to be
+    // specified.
+    static void* reserveAndCommit(size_t reserveSize, size_t commitSize, Usage = UnknownUsage, bool writable = true, bool executable = false);
+    static void decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize);
+};
+
+inline void* OSAllocator::reserveAndCommit(size_t reserveSize, size_t commitSize, Usage usage, bool writable, bool executable)
+{
+    void* base = reserveUncommitted(reserveSize, usage, writable, executable);
+    commit(base, commitSize, writable, executable);
+    return base;
+}
+
+inline void OSAllocator::decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize)
+{
+    ASSERT(decommitBase >= releaseBase && (static_cast<char*>(decommitBase) + decommitSize) <= (static_cast<char*>(releaseBase) + releaseSize));
+#if WTF_OS_WINCE || WTF_OS_SYMBIAN
+    // On most platforms we can actually skip this final decommit; releasing the VM will
+    // implicitly decommit any physical memory in the region. This is not true on WINCE.
+    // On Symbian, this makes implementation simpler and better aligned with the RChunk API
+    decommit(decommitBase, decommitSize);
+#endif
+    releaseDecommitted(releaseBase, releaseSize);
+}
+
+inline void OSAllocator::decommitAndRelease(void* base, size_t size)
+{
+    decommitAndRelease(base, size, base, size);
+}
+
+} // namespace WTF
+
+using WTF::OSAllocator;
+
+#endif /* yarr_OSAllocator_h */