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diff --git a/js/src/gc/Memory.h b/js/src/gc/Memory.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef gc_Memory_h
+#define gc_Memory_h
+
+#include "mozilla/Attributes.h"
+
+#include <stddef.h>
+
+namespace js {
+namespace gc {
+
+// Sanity check that our compiled configuration matches the currently
+// running instance and initialize any runtime data needed for allocation.
+void InitMemorySubsystem();
+
+// The page size as reported by the operating system.
+size_t SystemPageSize();
+
+// The number of bits that may be set in a valid address, as
+// reported by the operating system or measured at startup.
+size_t SystemAddressBits();
+
+// The number of bytes of virtual memory that may be allocated or mapped, as
+// reported by the operating system on certain platforms. If no limit was able
+// to be determined, then it will be size_t(-1).
+size_t VirtualMemoryLimit();
+
+// The scattershot allocator is used on platforms that have a large address
+// range. On these platforms we allocate at random addresses.
+bool UsingScattershotAllocator();
+
+// Allocate or deallocate pages from the system with the given alignment.
+// Pages will be read/write-able.
+void* MapAlignedPages(size_t length, size_t alignment);
+void UnmapPages(void* region, size_t length);
+
+// Tell the OS that the given pages are not in use, so they should not be
+// written to a paging file. This may be a no-op on some platforms.
+bool MarkPagesUnusedSoft(void* region, size_t length);
+
+// Tell the OS that the given pages are not in use and it can decommit them
+// immediately. This may defer to MarkPagesUnusedSoft and must be paired with
+// MarkPagesInUse to use the pages again.
+bool MarkPagesUnusedHard(void* region, size_t length);
+
+// Undo |MarkPagesUnusedSoft|: tell the OS that the given pages are of interest
+// and should be paged in and out normally. This may be a no-op on some
+// platforms.  May make pages read/write-able.
+void MarkPagesInUseSoft(void* region, size_t length);
+
+// Undo |MarkPagesUnusedHard|: tell the OS that the given pages are of interest
+// and should be paged in and out normally. This may be a no-op on some
+// platforms. Callers must check the result, false could mean that the pages
+// are not available.  May make pages read/write.
+MOZ_MUST_USE bool MarkPagesInUseHard(void* region, size_t length);
+
+// Returns #(hard faults) + #(soft faults)
+size_t GetPageFaultCount();
+
+// Allocate memory mapped content.
+// The offset must be aligned according to alignment requirement.
+void* AllocateMappedContent(int fd, size_t offset, size_t length,
+                            size_t alignment);
+
+// Deallocate memory mapped content.
+void DeallocateMappedContent(void* region, size_t length);
+
+void* TestMapAlignedPagesLastDitch(size_t size, size_t alignment);
+
+void ProtectPages(void* region, size_t length);
+void MakePagesReadOnly(void* region, size_t length);
+void UnprotectPages(void* region, size_t length);
+
+}  // namespace gc
+}  // namespace js
+
+#endif /* gc_Memory_h */