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73 lines
2.4 KiB
73 lines
2.4 KiB
/*
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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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#include <algorithm>
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#include "index_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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size_t IndexBssMappingEntry::GetBssOffset(size_t index_bits,
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uint32_t index,
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size_t slot_size) const {
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uint32_t diff = GetIndex(index_bits) - index;
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if (diff == 0u) {
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return bss_offset;
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}
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size_t mask_bits = 32u - index_bits;
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if (diff > mask_bits) {
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return IndexBssMappingLookup::npos;
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}
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// Shift out the index bits and bits for lower indexes.
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// Note that `index_bits + (mask_bits - diff) == 32 - diff`.
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uint32_t mask_from_index = index_and_mask >> (32u - diff);
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if ((mask_from_index & 1u) != 0u) {
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return bss_offset - POPCOUNT(mask_from_index) * slot_size;
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} else {
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return IndexBssMappingLookup::npos;
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}
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}
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constexpr size_t IndexBssMappingLookup::npos;
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size_t IndexBssMappingLookup::GetBssOffset(const IndexBssMapping* mapping,
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uint32_t index,
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uint32_t number_of_indexes,
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size_t slot_size) {
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DCHECK_LT(index, number_of_indexes);
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if (mapping == nullptr) {
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return npos;
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}
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size_t index_bits = IndexBssMappingEntry::IndexBits(number_of_indexes);
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uint32_t index_mask = IndexBssMappingEntry::IndexMask(index_bits);
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auto it = std::partition_point(
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mapping->begin(),
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mapping->end(),
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[=](const struct IndexBssMappingEntry& entry) {
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return (entry.index_and_mask & index_mask) < index;
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});
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if (it == mapping->end()) {
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return npos;
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}
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const IndexBssMappingEntry& entry = *it;
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return entry.GetBssOffset(index_bits, index, slot_size);
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}
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} // namespace art
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