The Tor Browser / file comparison
comparison: js/src/jit/PcScriptCache.h
js/src/jit/PcScriptCache.h
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
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| -1:000000000000 | 0:2b4619fdf18f |
|---|---|
| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- | |
| 2 * vim: set ts=8 sts=4 et sw=4 tw=99: | |
| 3 * This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 #ifndef jit_PcScriptCache_h | |
| 8 #define jit_PcScriptCache_h | |
| 9 | |
| 10 // Defines a fixed-size hash table solely for the purpose of caching jit::GetPcScript(). | |
| 11 // One cache is attached to each JSRuntime; it functions as if cleared on GC. | |
| 12 | |
| 13 struct JSRuntime; | |
| 14 | |
| 15 namespace js { | |
| 16 namespace jit { | |
| 17 | |
| 18 struct PcScriptCacheEntry | |
| 19 { | |
| 20 uint8_t *returnAddress; // Key into the hash table. | |
| 21 jsbytecode *pc; // Cached PC. | |
| 22 JSScript *script; // Cached script. | |
| 23 }; | |
| 24 | |
| 25 struct PcScriptCache | |
| 26 { | |
| 27 static const uint32_t Length = 73; | |
| 28 | |
| 29 // GC number at the time the cache was filled or created. | |
| 30 // Storing and checking against this number allows us to not bother | |
| 31 // clearing this cache on every GC -- only when actually necessary. | |
| 32 uint64_t gcNumber; | |
| 33 | |
| 34 // List of cache entries. | |
| 35 mozilla::Array<PcScriptCacheEntry, Length> entries; | |
| 36 | |
| 37 void clear(uint64_t gcNumber) { | |
| 38 for (uint32_t i = 0; i < Length; i++) | |
| 39 entries[i].returnAddress = nullptr; | |
| 40 this->gcNumber = gcNumber; | |
| 41 } | |
| 42 | |
| 43 // Get a value from the cache. May perform lazy allocation. | |
| 44 bool get(JSRuntime *rt, uint32_t hash, uint8_t *addr, | |
| 45 JSScript **scriptRes, jsbytecode **pcRes) | |
| 46 { | |
| 47 // If a GC occurred, lazily clear the cache now. | |
| 48 if (gcNumber != rt->gcNumber) { | |
| 49 clear(rt->gcNumber); | |
| 50 return false; | |
| 51 } | |
| 52 | |
| 53 if (entries[hash].returnAddress != addr) | |
| 54 return false; | |
| 55 | |
| 56 *scriptRes = entries[hash].script; | |
| 57 if (pcRes) | |
| 58 *pcRes = entries[hash].pc; | |
| 59 | |
| 60 return true; | |
| 61 } | |
| 62 | |
| 63 void add(uint32_t hash, uint8_t *addr, jsbytecode *pc, JSScript *script) { | |
| 64 entries[hash].returnAddress = addr; | |
| 65 entries[hash].pc = pc; | |
| 66 entries[hash].script = script; | |
| 67 } | |
| 68 | |
| 69 static uint32_t Hash(uint8_t *addr) { | |
| 70 uint32_t key = (uint32_t)((uintptr_t)addr); | |
| 71 return ((key >> 3) * 2654435761u) % Length; | |
| 72 } | |
| 73 }; | |
| 74 | |
| 75 } // namespace jit | |
| 76 } // namespace js | |
| 77 | |
| 78 #endif /* jit_PcScriptCache_h */ |
