104 lines
3.5 KiB
C++
104 lines
3.5 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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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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*/
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#ifndef ART_COMPILER_GC_MAP_BUILDER_H_
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#define ART_COMPILER_GC_MAP_BUILDER_H_
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#include <vector>
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#include "gc_map.h"
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#include "utils.h"
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namespace art {
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class GcMapBuilder {
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public:
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GcMapBuilder(std::vector<uint8_t>* table, size_t entries, uint32_t max_native_offset,
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size_t references_width)
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: entries_(entries), references_width_(entries != 0u ? references_width : 0u),
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native_offset_width_(entries != 0 && max_native_offset != 0
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? sizeof(max_native_offset) - CLZ(max_native_offset) / 8u
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: 0u),
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in_use_(entries), table_(table) {
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// Resize table and set up header.
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table->resize((EntryWidth() * entries) + sizeof(uint32_t));
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CHECK_LT(native_offset_width_, 1U << 3);
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(*table)[0] = native_offset_width_ & 7;
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CHECK_LT(references_width_, 1U << 13);
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(*table)[0] |= (references_width_ << 3) & 0xFF;
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(*table)[1] = (references_width_ >> 5) & 0xFF;
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CHECK_LT(entries, 1U << 16);
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(*table)[2] = entries & 0xFF;
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(*table)[3] = (entries >> 8) & 0xFF;
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}
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void AddEntry(uint32_t native_offset, const uint8_t* references) {
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size_t table_index = TableIndex(native_offset);
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while (in_use_[table_index]) {
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table_index = (table_index + 1) % entries_;
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}
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in_use_[table_index] = true;
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SetCodeOffset(table_index, native_offset);
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DCHECK_EQ(native_offset, GetCodeOffset(table_index));
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SetReferences(table_index, references);
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}
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private:
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size_t TableIndex(uint32_t native_offset) {
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return NativePcOffsetToReferenceMap::Hash(native_offset) % entries_;
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}
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uint32_t GetCodeOffset(size_t table_index) {
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uint32_t native_offset = 0;
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size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
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for (size_t i = 0; i < native_offset_width_; i++) {
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native_offset |= (*table_)[table_offset + i] << (i * 8);
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}
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return native_offset;
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}
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void SetCodeOffset(size_t table_index, uint32_t native_offset) {
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size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
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for (size_t i = 0; i < native_offset_width_; i++) {
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(*table_)[table_offset + i] = (native_offset >> (i * 8)) & 0xFF;
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}
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}
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void SetReferences(size_t table_index, const uint8_t* references) {
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size_t table_offset = (table_index * EntryWidth()) + sizeof(uint32_t);
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memcpy(&(*table_)[table_offset + native_offset_width_], references, references_width_);
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}
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size_t EntryWidth() const {
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return native_offset_width_ + references_width_;
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}
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// Number of entries in the table.
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const size_t entries_;
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// Number of bytes used to encode the reference bitmap.
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const size_t references_width_;
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// Number of bytes used to encode a native offset.
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const size_t native_offset_width_;
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// Entries that are in use.
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std::vector<bool> in_use_;
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// The table we're building.
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std::vector<uint8_t>* const table_;
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};
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} // namespace art
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#endif // ART_COMPILER_GC_MAP_BUILDER_H_
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