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https://github.com/KhronosGroup/SPIRV-Tools
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d42f65e7c1
The unordered_set in ADCE that holds all of the live instructions takes a very long time to be destroyed. In some shaders, it takes over 40% of the time. If we look at the unique ids of the live instructions, I believe they are dense enough make a simple bit vector a good choice for to hold that data. When I check the density of the bit vector for larger shaders, we are usually using less than 4 bytes per element in the vector, and almost always less than 16. So, in this commit, I introduce a simple bit vector class, and use it in ADCE. This help improve the compile time for some shaders on windows by the 40% mentioned above. Contributes to https://github.com/KhronosGroup/SPIRV-Tools/issues/1328.
103 lines
2.8 KiB
C++
103 lines
2.8 KiB
C++
// Copyright (c) 2018 Google LLC
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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 LIBSPIRV_UTILS_BIT_VECTOR_H_
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#define LIBSPIRV_UTILS_BIT_VECTOR_H_
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#include <cstdint>
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#include <iosfwd>
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#include <vector>
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namespace spvtools {
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namespace utils {
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// Implements a bit vector class.
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//
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// All bits default to zero, and the upper bound is 2^32-1.
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class BitVector {
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private:
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using BitContainer = uint64_t;
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enum { kBitContainerSize = 64 };
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enum { kInitialNumBits = 1024 };
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public:
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// Creates a bit vector contianing 0s.
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BitVector() : bits_(kInitialNumBits / kBitContainerSize, 0) {}
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// Sets the |i|th bit to 1. Returns the |i|th bit before it was set.
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bool Set(uint32_t i) {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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bits_.resize(element_index + 1, 0);
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}
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BitContainer original = bits_[element_index];
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BitContainer ith_bit = static_cast<BitContainer>(1) << bit_in_element;
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if ((original & ith_bit) != 0) {
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return true;
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} else {
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bits_[element_index] = original | ith_bit;
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return false;
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}
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}
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// Sets the |i|th bit to 0. Return the |i|th bit before it was cleared.
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bool Clear(uint32_t i) {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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return false;
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}
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BitContainer original = bits_[element_index];
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BitContainer ith_bit = static_cast<BitContainer>(1) << bit_in_element;
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if ((original & ith_bit) == 0) {
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return false;
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} else {
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bits_[element_index] = original & (~ith_bit);
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return true;
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}
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}
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// Returns the |i|th bit.
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bool Get(uint32_t i) const {
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uint32_t element_index = i / kBitContainerSize;
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uint32_t bit_in_element = i % kBitContainerSize;
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if (element_index >= bits_.size()) {
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return false;
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}
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return (bits_[element_index] &
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(static_cast<BitContainer>(1) << bit_in_element)) != 0;
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}
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// Print a report on the densicy of the bit vector, number of 1 bits, number
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// of bytes, and average bytes for 1 bit, to |out|.
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void ReportDensity(std::ostream& out);
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private:
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std::vector<BitContainer> bits_;
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};
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} // namespace utils
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} // namespace spvtools
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#endif // LIBSPIRV_UTILS_BIT_VECTOR_H_
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