1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <algorithm> 18 19 #include "index_bss_mapping.h" 20 21 #include "base/bit_utils.h" 22 #include "base/length_prefixed_array.h" 23 24 namespace art { 25 26 size_t IndexBssMappingEntry::GetBssOffset(size_t index_bits, 27 uint32_t index, 28 size_t slot_size) const { 29 uint32_t diff = GetIndex(index_bits) - index; 30 if (diff == 0u) { 31 return bss_offset; 32 } 33 size_t mask_bits = 32u - index_bits; 34 if (diff > mask_bits) { 35 return IndexBssMappingLookup::npos; 36 } 37 // Shift out the index bits and bits for lower indexes. 38 // Note that `index_bits + (mask_bits - diff) == 32 - diff`. 39 uint32_t mask_from_index = index_and_mask >> (32u - diff); 40 if ((mask_from_index & 1u) != 0u) { 41 return bss_offset - POPCOUNT(mask_from_index) * slot_size; 42 } else { 43 return IndexBssMappingLookup::npos; 44 } 45 } 46 47 constexpr size_t IndexBssMappingLookup::npos; 48 49 size_t IndexBssMappingLookup::GetBssOffset(const IndexBssMapping* mapping, 50 uint32_t index, 51 uint32_t number_of_indexes, 52 size_t slot_size) { 53 DCHECK_LT(index, number_of_indexes); 54 if (mapping == nullptr) { 55 return npos; 56 } 57 size_t index_bits = IndexBssMappingEntry::IndexBits(number_of_indexes); 58 uint32_t index_mask = IndexBssMappingEntry::IndexMask(index_bits); 59 auto it = std::partition_point( 60 mapping->begin(), 61 mapping->end(), 62 [=](const struct IndexBssMappingEntry& entry) { 63 return (entry.index_and_mask & index_mask) < index; 64 }); 65 if (it == mapping->end()) { 66 return npos; 67 } 68 const IndexBssMappingEntry& entry = *it; 69 return entry.GetBssOffset(index_bits, index, slot_size); 70 } 71 72 } // namespace art 73
