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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_JitHints_h
+#define jit_JitHints_h
+
+#include "mozilla/BloomFilter.h"
+#include "vm/JSScript.h"
+
+namespace js::jit {
+
+/*
+ * The JitHintsMap implements a BitBloomFilter to track whether or not a script,
+ * identified by filename+sourceStart, has been baseline compiled before in the
+ * same process. This can occur frequently during navigations.
+ *
+ * The bloom filter allows us to have very efficient storage and lookup costs,
+ * at the expense of occasional false positives. The number of entries added
+ * to the bloom filter is monitored in order to try and keep the false
+ * positivity rate below 1%. If the entry count exceeds MaxEntries_, which
+ * indicates the false positivity rate may exceed 1.5%, then the filter is
+ * completely cleared to reset the cache.
+ */
+
+class JitHintsMap {
+ // ScriptKey is a hash on the filename+sourceStart.
+ using ScriptKey = HashNumber;
+
+ static constexpr uint32_t CacheSize_ = 16;
+ mozilla::BitBloomFilter<CacheSize_, ScriptKey> map_;
+
+ /*
+ * MaxEntries_ is the approximate entry count for which the
+ * false positivity rate will exceed p=0.015 using k=2 and m=2**CacheSize.
+ * Formula is as follows:
+ * MaxEntries_ = floor(m / (-k / ln(1-exp(ln(p) / k))))
+ */
+ static constexpr uint32_t MaxEntries_ = 4281;
+ static_assert(CacheSize_ == 16 && MaxEntries_ == 4281,
+ "MaxEntries should be recalculated for given CacheSize.");
+
+ uint32_t entryCount_ = 0;
+
+ ScriptKey getScriptKey(JSScript* script) const;
+ void incrementEntryCount();
+
+ public:
+ void setEagerBaselineHint(JSScript* script);
+ bool mightHaveEagerBaselineHint(JSScript* script) const;
+};
+
+} // namespace js::jit
+#endif /* jit_JitHints_h */