mirror of
https://github.com/KhronosGroup/SPIRV-Tools
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a123632ed9
Incrementally compute the hash instead of collecting words Avoids allocating temporary space in a std::vector and std::u32string, and making three passes over all the hashed data. Switch to using std::vector to prevent processing duplicates instead of std::unordered_set: avoids an allocation/deletion every call to ComputeHashValue, and ends up faster due to much better cache behaviour and smaller constant-factor when searching the (generally very small) list. In my test case, made Type::HashValue go from 7.5% of compilation time to .5%
54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
// Copyright (c) 2022 The Khronos Group Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SOURCE_UTIL_HASH_COMBINE_H_
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#define SOURCE_UTIL_HASH_COMBINE_H_
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#include <cstddef>
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#include <functional>
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#include <vector>
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namespace spvtools {
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namespace utils {
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// Helpers for incrementally computing hashes.
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// For reference, see
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// http://open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3876.pdf
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template <typename T>
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inline size_t hash_combine(std::size_t seed, const T& val) {
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return seed ^ (std::hash<T>()(val) + 0x9e3779b9 + (seed << 6) + (seed >> 2));
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}
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template <typename T>
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inline size_t hash_combine(std::size_t hash, const std::vector<T>& vals) {
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for (const T& val : vals) {
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hash = hash_combine(hash, val);
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}
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return hash;
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}
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inline size_t hash_combine(std::size_t hash) { return hash; }
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template <typename T, typename... Types>
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inline size_t hash_combine(std::size_t hash, const T& val,
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const Types&... args) {
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return hash_combine(hash_combine(hash, val), args...);
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}
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} // namespace utils
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} // namespace spvtools
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#endif // SOURCE_UTIL_HASH_COMBINE_H_
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