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diff --git a/clang-r353983/include/llvm/Support/CachePruning.h b/clang-r353983/include/llvm/Support/CachePruning.h
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+//=- CachePruning.h - Helper to manage the pruning of a cache dir -*- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements pruning of a directory intended for cache storage, using
+// various policies.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CACHE_PRUNING_H
+#define LLVM_SUPPORT_CACHE_PRUNING_H
+
+#include "llvm/ADT/StringRef.h"
+#include <chrono>
+
+namespace llvm {
+
+template <typename T> class Expected;
+
+/// Policy for the pruneCache() function. A default constructed
+/// CachePruningPolicy provides a reasonable default policy.
+struct CachePruningPolicy {
+  /// The pruning interval. This is intended to be used to avoid scanning the
+  /// directory too often. It does not impact the decision of which file to
+  /// prune. A value of 0 forces the scan to occur. A value of None disables
+  /// pruning.
+  llvm::Optional<std::chrono::seconds> Interval = std::chrono::seconds(1200);
+
+  /// The expiration for a file. When a file hasn't been accessed for Expiration
+  /// seconds, it is removed from the cache. A value of 0 disables the
+  /// expiration-based pruning.
+  std::chrono::seconds Expiration = std::chrono::hours(7 * 24); // 1w
+
+  /// The maximum size for the cache directory, in terms of percentage of the
+  /// available space on the disk. Set to 100 to indicate no limit, 50 to
+  /// indicate that the cache size will not be left over half the available disk
+  /// space. A value over 100 will be reduced to 100. A value of 0 disables the
+  /// percentage size-based pruning.
+  unsigned MaxSizePercentageOfAvailableSpace = 75;
+
+  /// The maximum size for the cache directory in bytes. A value over the amount
+  /// of available space on the disk will be reduced to the amount of available
+  /// space. A value of 0 disables the absolute size-based pruning.
+  uint64_t MaxSizeBytes = 0;
+
+  /// The maximum number of files in the cache directory. A value of 0 disables
+  /// the number of files based pruning.
+  ///
+  /// This defaults to 1000000 because with that many files there are
+  /// diminishing returns on the effectiveness of the cache. Some systems have a
+  /// limit on total number of files, and some also limit the number of files
+  /// per directory, such as Linux ext4, with the default setting (block size is
+  /// 4096 and large_dir disabled), there is a per-directory entry limit of
+  /// 508*510*floor(4096/(40+8))~=20M for average filename length of 40.
+  uint64_t MaxSizeFiles = 1000000;
+};
+
+/// Parse the given string as a cache pruning policy. Defaults are taken from a
+/// default constructed CachePruningPolicy object.
+/// For example: "prune_interval=30s:prune_after=24h:cache_size=50%"
+/// which means a pruning interval of 30 seconds, expiration time of 24 hours
+/// and maximum cache size of 50% of available disk space.
+Expected<CachePruningPolicy> parseCachePruningPolicy(StringRef PolicyStr);
+
+/// Peform pruning using the supplied policy, returns true if pruning
+/// occurred, i.e. if Policy.Interval was expired.
+///
+/// As a safeguard against data loss if the user specifies the wrong directory
+/// as their cache directory, this function will ignore files not matching the
+/// pattern "llvmcache-*".
+bool pruneCache(StringRef Path, CachePruningPolicy Policy);
+
+} // namespace llvm
+
+#endif