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 #ifndef ART_RUNTIME_METHOD_BSS_MAPPING_H_ 18 #define ART_RUNTIME_METHOD_BSS_MAPPING_H_ 19 20 #include "base/bit_utils.h" 21 #include "base/length_prefixed_array.h" 22 23 namespace art { 24 25 // MethodBssMappingEntry describes a mapping of up to 17 method indexes to their offsets 26 // in the .bss. The highest index and its associated .bss offset are stored in plain form 27 // as `method_index` and `bss_offset`, respectively, while the additional indexes can be 28 // stored in compressed form if their associated .bss entries are consecutive and in the 29 // method index order. Each of the 16 bits of the `index_mask` corresponds to one of the 30 // previous 16 method indexes and indicates whether there is a .bss entry for that index. 31 // 32 struct MethodBssMappingEntry { 33 bool CoversIndex(uint32_t method_idx) const { 34 uint32_t diff = method_index - method_idx; 35 return (diff == 0) || (diff <= 16 && ((index_mask >> (16u - diff)) & 1u) != 0); 36 } 37 38 uint32_t GetBssOffset(uint32_t method_idx, size_t entry_size) const { 39 DCHECK(CoversIndex(method_idx)); 40 uint32_t diff = method_index - method_idx; 41 if (diff == 0) { 42 return bss_offset; 43 } else { 44 return bss_offset - POPCOUNT(index_mask >> (16u - diff)) * entry_size; 45 } 46 } 47 48 uint16_t method_index; 49 uint16_t index_mask; 50 uint32_t bss_offset; 51 }; 52 53 using MethodBssMapping = LengthPrefixedArray<MethodBssMappingEntry>; 54 55 } // namespace art 56 57 #endif // ART_RUNTIME_METHOD_BSS_MAPPING_H_ 58
