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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /js/src/jit/PcScriptCache.h
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'js/src/jit/PcScriptCache.h')
-rw-r--r--js/src/jit/PcScriptCache.h88
1 files changed, 88 insertions, 0 deletions
diff --git a/js/src/jit/PcScriptCache.h b/js/src/jit/PcScriptCache.h
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+/* -*- 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 */