57 lines
2 KiB
C++
57 lines
2 KiB
C++
/*
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* Copyright (C) 2017 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_RUNTIME_METHOD_BSS_MAPPING_H_
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#define ART_RUNTIME_METHOD_BSS_MAPPING_H_
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#include "base/bit_utils.h"
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#include "base/length_prefixed_array.h"
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namespace art {
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// MethodBssMappingEntry describes a mapping of up to 17 method indexes to their offsets
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// in the .bss. The highest index and its associated .bss offset are stored in plain form
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// as `method_index` and `bss_offset`, respectively, while the additional indexes can be
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// stored in compressed form if their associated .bss entries are consecutive and in the
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// method index order. Each of the 16 bits of the `index_mask` corresponds to one of the
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// previous 16 method indexes and indicates whether there is a .bss entry for that index.
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//
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struct MethodBssMappingEntry {
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bool CoversIndex(uint32_t method_idx) const {
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uint32_t diff = method_index - method_idx;
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return (diff == 0) || (diff <= 16 && ((index_mask >> (16u - diff)) & 1u) != 0);
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}
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uint32_t GetBssOffset(uint32_t method_idx, size_t entry_size) const {
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DCHECK(CoversIndex(method_idx));
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uint32_t diff = method_index - method_idx;
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if (diff == 0) {
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return bss_offset;
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} else {
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return bss_offset - POPCOUNT(index_mask >> (16u - diff)) * entry_size;
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}
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}
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uint16_t method_index;
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uint16_t index_mask;
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uint32_t bss_offset;
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};
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using MethodBssMapping = LengthPrefixedArray<MethodBssMappingEntry>;
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} // namespace art
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#endif // ART_RUNTIME_METHOD_BSS_MAPPING_H_
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