Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 182 insertions, 0 deletions

diff --git a/js/src/jit/JitHints.h b/js/src/jit/JitHints.h
new file mode 100644
index 0000000000..c2f1f1129d
--- /dev/null
+++ b/js/src/jit/JitHints.h
@@ -0,0 +1,182 @@
+/* -*- 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 "mozilla/HashTable.h"
+#include "mozilla/LinkedList.h"
+#include "jit/JitOptions.h"
+#include "vm/BytecodeLocation.h"
+#include "vm/JSScript.h"
+
+namespace js::jit {
+
+/*
+ *
+ * [SMDOC] JitHintsMap
+ *
+ * The Jit hints map is an in process cache used to collect Baseline and Ion
+ * JIT hints to try and skip as much of the warmup as possible and jump
+ * straight into those tiers.  Whenever a script enters one of these tiers
+ * a hint is recorded in this cache using the script's filename+sourceStart
+ * value, and if we ever encounter this script again later, e.g. during a
+ * navigation, then we try to eagerly compile it into baseline and ion
+ * based on its previous execution history.
+ */
+
+class JitHintsMap {
+  // ScriptKey is a hash on the filename+sourceStart.
+  using ScriptKey = HashNumber;
+  ScriptKey getScriptKey(JSScript* script) const;
+
+  /* Ion Hints
+   * -------------------------------------------------------------------------
+   * This implementation uses a combination of a HashMap and PriorityQueue
+   * to store a threshold value for each script that has been Ion compiled.
+   * The PriorityQueue is used to track the least recently used entries so
+   * that the cache does not exceed |IonHintMaxEntries| entries.
+   *
+   * After a script has entered Ion the first time, an eager threshold hint
+   * value is set using the warmup counter of when the last IC stub was
+   * attached, if available. This minimizes the risk that the script will
+   * bailout. If that script is bailout invalidated, the threshold value
+   * is incremented by |InvalidationThresholdIncrement| up to a maximum value of
+   * |JitOptions.normalIonWarmUpThreshold|.
+   *
+   * Each IonHint object also contains a list of bytecode offsets for locations
+   * of monomorphic inline calls that is used as a hint for future compilations.
+   *
+   */
+  class IonHint : public mozilla::LinkedListElement<IonHint> {
+    ScriptKey key_ = 0;
+
+    // We use a value of 0 to indicate that the script has not entered Ion
+    // yet, but has been monomorphically inlined and Ion compiled into
+    // another script and contains bytecode offsets of a nested call.
+    uint32_t threshold_ = 0;
+
+    // List of bytecode offsets that have been successfully inlined with
+    // a state of monomorphic inline.
+    Vector<uint32_t, 0, SystemAllocPolicy> monomorphicInlineOffsets;
+
+   public:
+    explicit IonHint(ScriptKey key) { key_ = key; }
+
+    void initThreshold(uint32_t lastStubCounter) {
+      threshold_ = IonHintEagerThresholdValue(lastStubCounter);
+    }
+
+    uint32_t threshold() { return threshold_; }
+
+    void incThreshold(uint32_t inc) {
+      uint32_t newThreshold = threshold() + inc;
+      threshold_ = (newThreshold > JitOptions.normalIonWarmUpThreshold)
+                       ? JitOptions.normalIonWarmUpThreshold
+                       : newThreshold;
+    }
+
+    bool hasSpaceForMonomorphicInlineEntry() {
+      return monomorphicInlineOffsets.length() < MonomorphicInlineMaxEntries;
+    }
+
+    bool hasMonomorphicInlineOffset(uint32_t offset) {
+      for (uint32_t iterOffset : monomorphicInlineOffsets) {
+        if (iterOffset == offset) {
+          return true;
+        }
+      }
+      return false;
+    }
+
+    bool addMonomorphicInlineOffset(uint32_t newOffset) {
+      MOZ_ASSERT(hasSpaceForMonomorphicInlineEntry());
+
+      if (hasMonomorphicInlineOffset(newOffset)) {
+        return true;
+      }
+      return monomorphicInlineOffsets.append(newOffset);
+    }
+
+    ScriptKey key() {
+      MOZ_ASSERT(key_ != 0, "Should have valid key.");
+      return key_;
+    }
+  };
+
+  using ScriptToHintMap =
+      HashMap<ScriptKey, IonHint*, js::DefaultHasher<ScriptKey>,
+              js::SystemAllocPolicy>;
+  using IonHintPriorityQueue = mozilla::LinkedList<IonHint>;
+
+  static constexpr uint32_t InvalidationThresholdIncrement = 500;
+  static constexpr uint32_t IonHintMaxEntries = 5000;
+  static constexpr uint32_t MonomorphicInlineMaxEntries = 16;
+
+  static uint32_t IonHintEagerThresholdValue(uint32_t lastStubCounter) {
+    // Use the counter when the last IC stub was attached but add 10
+    // for some wiggle room and to safeguard against cases where the
+    // lastStubCounter is 0.
+    uint32_t eagerThreshold = lastStubCounter + 10;
+
+    // Do not exceed the default Ion threshold value set in the options.
+    return std::min(eagerThreshold, JitOptions.normalIonWarmUpThreshold);
+  }
+
+  ScriptToHintMap ionHintMap_;
+  IonHintPriorityQueue ionHintQueue_;
+
+  /* Baseline Hints
+   * --------------------------------------------------------------------------
+   * This implementation uses a BitBloomFilter to track whether or not a script
+   * 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.  Using a bloom filter also
+   * allows us to have many more entries at minimal memory and allocation cost.
+   * 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.
+   */
+  static constexpr uint32_t EagerBaselineCacheSize_ = 16;
+  mozilla::BitBloomFilter<EagerBaselineCacheSize_, ScriptKey> baselineHintMap_;
+
+  /*
+   * 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(EagerBaselineCacheSize_ == 16 && MaxEntries_ == 4281,
+                "MaxEntries should be recalculated for given CacheSize.");
+
+  uint32_t baselineEntryCount_ = 0;
+  void incrementBaselineEntryCount();
+
+  void updateAsRecentlyUsed(IonHint* hint);
+  IonHint* addIonHint(ScriptKey key, ScriptToHintMap::AddPtr& p);
+
+ public:
+  ~JitHintsMap();
+
+  void setEagerBaselineHint(JSScript* script);
+  bool mightHaveEagerBaselineHint(JSScript* script) const;
+
+  bool recordIonCompilation(JSScript* script);
+  bool getIonThresholdHint(JSScript* script, uint32_t& thresholdOut);
+
+  bool addMonomorphicInlineLocation(JSScript* script, BytecodeLocation loc);
+  bool hasMonomorphicInlineHintAtOffset(JSScript* script, uint32_t offset);
+
+  void recordInvalidation(JSScript* script);
+};
+
+}  // namespace js::jit
+#endif /* jit_JitHints_h */