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[multimapcache] Change multi-map cache to use a std::function instead of CRTP.

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This makes it so one uses a passed in std::function, instead of an impl class to
map a key to a list of values to be cached.
This commit is contained in:
Michael Gottesman
2020-04-14 22:58:24 -07:00
parent 061c6d0654
commit dd7f780993
2 changed files with 54 additions and 34 deletions
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29
include/swift/Basic/MultiMapCache.h
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@@ -18,15 +18,11 @@
namespace swift {
/// A CRTP write-once multi-map cache that can be small. It uses a DenseMap
/// A write-once multi-map cache that can be small. It uses a DenseMap
/// internally, so it can be used as a cache without needing to be frozen like
/// FrozenMultiMap (which uses only a vector internally). The Impl class
/// implements the method constructValuesForKey that is used to compute the
/// actual cache value.
///
/// NOTE: constructValuesForKeys is assumed to take a KeyTy and a
/// SmallVectorImpl<ValueTy>. It must append all results to that accumulator and
/// not read any contents of the accumulator.
/// FrozenMultiMap (which uses only a vector internally). The cached value is
/// computed by a passed in std::function. The std::function is able to map
/// multiple values to a specific key via the out array.
///
/// NOTE: We store the (size, length) of each ArrayRef<ValueTy> instead of
/// storing the ArrayRef to avoid data invalidation issues caused by SmallVector
@@ -34,24 +30,23 @@ namespace swift {
///
/// For an example of a subclass implementation see:
/// unittests/Basic/MultiMapCacheTest.cpp.
template <typename ImplType, typename KeyTy, typename ValueTy,
template <typename KeyTy, typename ValueTy,
typename MapTy =
llvm::DenseMap<KeyTy, Optional<std::tuple<unsigned, unsigned>>>,
typename VectorTy = std::vector<ValueTy>,
typename VectorTyImpl = VectorTy>
class MultiMapCache {
std::function<bool(const KeyTy &, VectorTyImpl &)> function;
MapTy valueToDataOffsetIndexMap;
VectorTy data;
constexpr static unsigned ArrayStartOffset = 0;
constexpr static unsigned ArrayLengthOffset = 1;
constexpr ImplType &asImpl() const {
auto *self = const_cast<MultiMapCache *>(this);
return reinterpret_cast<ImplType &>(*self);
}
public:
MultiMapCache(std::function<bool(const KeyTy &, VectorTyImpl &)> function)
: function(function) {}
void clear() {
valueToDataOffsetIndexMap.clear();
data.clear();
@@ -81,7 +76,7 @@ public:
// We assume that constructValuesForKey /only/ inserts to the end of data
// and does not inspect any other values in the data array.
if (!asImpl().constructValuesForKey(key, data)) {
if (!function(key, data)) {
return None;
}
@@ -94,9 +89,9 @@ public:
}
};
template <typename ImplType, typename KeyTy, typename ValueTy>
template <typename KeyTy, typename ValueTy>
using SmallMultiMapCache = MultiMapCache<
ImplType, KeyTy, ValueTy,
KeyTy, ValueTy,
llvm::SmallDenseMap<KeyTy, Optional<std::tuple<unsigned, unsigned>>, 8>,
SmallVector<ValueTy, 32>, SmallVectorImpl<ValueTy>>;