Vladimir Marko | 0eb882b | 2017-05-15 13:39:18 +0100 | [diff] [blame] | 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_ |