blob: c83c479c853a9d5b85def5a3e1174ef325c49a71 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef jit_PcScriptCache_h
#define jit_PcScriptCache_h
#include "mozilla/Array.h"
#include "js/TypeDecls.h"
#include "vm/Runtime.h"
// Defines a fixed-size hash table solely for the purpose of caching
// jit::GetPcScript(). One cache is attached to each JSRuntime; it functions as
// if cleared on GC.
namespace js {
namespace jit {
struct PcScriptCacheEntry {
uint8_t* returnAddress; // Key into the hash table.
jsbytecode* pc; // Cached PC.
JSScript* script; // Cached script.
};
struct PcScriptCache {
private:
static const uint32_t Length = 73;
// GC number at the time the cache was filled or created.
// Storing and checking against this number allows us to not bother
// clearing this cache on every GC -- only when actually necessary.
uint64_t gcNumber;
// List of cache entries.
mozilla::Array<PcScriptCacheEntry, Length> entries;
public:
explicit PcScriptCache(uint64_t gcNumber) { clear(gcNumber); }
void clear(uint64_t gcNumber) {
for (uint32_t i = 0; i < Length; i++) {
entries[i].returnAddress = nullptr;
}
this->gcNumber = gcNumber;
}
// Get a value from the cache. May perform lazy allocation.
[[nodiscard]] bool get(JSRuntime* rt, uint32_t hash, uint8_t* addr,
JSScript** scriptRes, jsbytecode** pcRes) {
// If a GC occurred, lazily clear the cache now.
if (gcNumber != rt->gc.gcNumber()) {
clear(rt->gc.gcNumber());
return false;
}
if (entries[hash].returnAddress != addr) {
return false;
}
*scriptRes = entries[hash].script;
if (pcRes) {
*pcRes = entries[hash].pc;
}
return true;
}
void add(uint32_t hash, uint8_t* addr, jsbytecode* pc, JSScript* script) {
MOZ_ASSERT(addr);
MOZ_ASSERT(pc);
MOZ_ASSERT(script);
entries[hash].returnAddress = addr;
entries[hash].pc = pc;
entries[hash].script = script;
}
static uint32_t Hash(uint8_t* addr) {
uint32_t key = (uint32_t)((uintptr_t)addr);
return ((key >> 3) * 2654435761u) % Length;
}
};
} // namespace jit
} // namespace js
#endif /* jit_PcScriptCache_h */
|
