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902cbd259a
makeArrayRef was being included through an import an DenseMap.h ->
DenseMapInfo.h -> ArrayRef.h. That was broken fairly recently.
(cherry picked from commit fe2b3c6021)
102 lines
3.8 KiB
C++
102 lines
3.8 KiB
C++
//===--- MultiMapCache.h --------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_BASIC_MULTIMAPCACHE_H
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#define SWIFT_BASIC_MULTIMAPCACHE_H
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#include "swift/Basic/LLVM.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/DenseMap.h"
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namespace swift {
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/// A write-once multi-map cache that can be small. It uses a DenseMap
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/// internally, so it can be used as a cache without needing to be frozen like
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/// FrozenMultiMap (which uses only a vector internally). The cached value is
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/// computed by a passed in std::function. The std::function is able to map
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/// multiple values to a specific key via the out array.
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///
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/// NOTE: We store the (size, length) of each ArrayRef<ValueTy> instead of
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/// storing the ArrayRef to avoid data invalidation issues caused by SmallVector
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/// switching from small to large representations.
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///
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/// For an example of a subclass implementation see:
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/// unittests/Basic/MultiMapCacheTest.cpp.
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template <typename KeyTy, typename ValueTy,
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typename MapTy =
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llvm::DenseMap<KeyTy, Optional<std::tuple<unsigned, unsigned>>>,
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typename VectorTy = std::vector<ValueTy>,
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typename VectorTyImpl = VectorTy>
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class MultiMapCache {
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std::function<bool(const KeyTy &, VectorTyImpl &)> function;
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MapTy valueToDataOffsetIndexMap;
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VectorTy data;
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constexpr static unsigned ArrayStartOffset = 0;
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constexpr static unsigned ArrayLengthOffset = 1;
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public:
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MultiMapCache(std::function<bool(const KeyTy &, VectorTyImpl &)> function)
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: function(function) {}
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void clear() {
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valueToDataOffsetIndexMap.clear();
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data.clear();
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}
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bool empty() const { return valueToDataOffsetIndexMap.empty(); }
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unsigned size() const { return valueToDataOffsetIndexMap.size(); }
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Optional<ArrayRef<ValueTy>> get(const KeyTy &key) {
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auto iter = valueToDataOffsetIndexMap.try_emplace(key, None);
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// If we already have a cached value, just return the cached value.
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if (!iter.second) {
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return iter.first->second.map(
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[&](std::tuple<unsigned, unsigned> startLengthRange) {
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return llvm::makeArrayRef(data).slice(
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std::get<ArrayStartOffset>(startLengthRange),
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std::get<ArrayLengthOffset>(startLengthRange));
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});
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}
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// Otherwise, try to compute the value. If we failed conservatively, return
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// None. The iter value already had None by default set to it, this just
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// makes it so that we do not need to have a memory dependency and can just
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// exit.
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unsigned initialOffset = data.size();
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// We assume that constructValuesForKey /only/ inserts to the end of data
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// and does not inspect any other values in the data array.
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if (!function(key, data)) {
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return None;
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}
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// Otherwise, compute our our length, compute our initial ArrayRef<ValueTy>,
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// update the map with the start, length, and return the resulting ArrayRef.
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unsigned length = data.size() - initialOffset;
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iter.first->second = std::make_tuple(initialOffset, length);
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auto result = llvm::makeArrayRef(data).slice(initialOffset, length);
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return result;
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}
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};
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template <typename KeyTy, typename ValueTy>
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using SmallMultiMapCache = MultiMapCache<
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KeyTy, ValueTy,
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llvm::SmallDenseMap<KeyTy, Optional<std::tuple<unsigned, unsigned>>, 8>,
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SmallVector<ValueTy, 32>, SmallVectorImpl<ValueTy>>;
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} // namespace swift
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#endif
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