Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 413 insertions, 0 deletions

diff --git a/js/src/gc/WeakMap-inl.h b/js/src/gc/WeakMap-inl.h
new file mode 100644
index 0000000000..1b5626211f
--- /dev/null
+++ b/js/src/gc/WeakMap-inl.h
@@ -0,0 +1,413 @@
+/* -*- 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 gc_WeakMap_inl_h
+#define gc_WeakMap_inl_h
+
+#include "gc/WeakMap.h"
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Maybe.h"
+
+#include <algorithm>
+#include <type_traits>
+
+#include "gc/GCLock.h"
+#include "gc/Marking.h"
+#include "gc/Zone.h"
+#include "js/TraceKind.h"
+#include "vm/JSContext.h"
+
+#include "gc/StableCellHasher-inl.h"
+
+namespace js {
+namespace gc {
+
+namespace detail {
+
+// Return the effective cell color given the current marking state.
+// This must be kept in sync with ShouldMark in Marking.cpp.
+template <typename T>
+static CellColor GetEffectiveColor(GCMarker* marker, const T& item) {
+  Cell* cell = ToMarkable(item);
+  if (!cell->isTenured()) {
+    return CellColor::Black;
+  }
+  const TenuredCell& t = cell->asTenured();
+  if (!t.zoneFromAnyThread()->shouldMarkInZone(marker->markColor())) {
+    return CellColor::Black;
+  }
+  MOZ_ASSERT(t.runtimeFromAnyThread() == marker->runtime());
+  return t.color();
+}
+
+// Only objects have delegates, so default to returning nullptr. Note that some
+// compilation units will only ever use the object version.
+static MOZ_MAYBE_UNUSED JSObject* GetDelegateInternal(gc::Cell* key) {
+  return nullptr;
+}
+
+static MOZ_MAYBE_UNUSED JSObject* GetDelegateInternal(JSObject* key) {
+  JSObject* delegate = UncheckedUnwrapWithoutExpose(key);
+  return (key == delegate) ? nullptr : delegate;
+}
+
+// Use a helper function to do overload resolution to handle cases like
+// Heap<ObjectSubclass*>: find everything that is convertible to JSObject* (and
+// avoid calling barriers).
+template <typename T>
+static inline JSObject* GetDelegate(const T& key) {
+  return GetDelegateInternal(key);
+}
+
+template <>
+inline JSObject* GetDelegate(gc::Cell* const&) = delete;
+
+} /* namespace detail */
+} /* namespace gc */
+
+// Weakmap entry -> value edges are only visible if the map is traced, which
+// only happens if the map zone is being collected. If the map and the value
+// were in different zones, then we could have a case where the map zone is not
+// collecting but the value zone is, and incorrectly free a value that is
+// reachable solely through weakmaps.
+template <class K, class V>
+void WeakMap<K, V>::assertMapIsSameZoneWithValue(const V& v) {
+#ifdef DEBUG
+  gc::Cell* cell = gc::ToMarkable(v);
+  if (cell) {
+    Zone* cellZone = cell->zoneFromAnyThread();
+    MOZ_ASSERT(zone() == cellZone || cellZone->isAtomsZone());
+  }
+#endif
+}
+
+template <class K, class V>
+WeakMap<K, V>::WeakMap(JSContext* cx, JSObject* memOf)
+    : WeakMap(cx->zone(), memOf) {}
+
+template <class K, class V>
+WeakMap<K, V>::WeakMap(JS::Zone* zone, JSObject* memOf)
+    : Base(zone), WeakMapBase(memOf, zone) {
+  using ElemType = typename K::ElementType;
+  using NonPtrType = std::remove_pointer_t<ElemType>;
+
+  // The object's TraceKind needs to be added to CC graph if this object is
+  // used as a WeakMap key, otherwise the key is considered to be pointed from
+  // somewhere unknown, and results in leaking the subgraph which contains the
+  // key. See the comments in NoteWeakMapsTracer::trace for more details.
+  static_assert(JS::IsCCTraceKind(NonPtrType::TraceKind),
+                "Object's TraceKind should be added to CC graph.");
+
+  zone->gcWeakMapList().insertFront(this);
+  if (zone->gcState() > Zone::Prepare) {
+    mapColor = CellColor::Black;
+  }
+}
+
+// If the entry is live, ensure its key and value are marked. Also make sure the
+// key is at least as marked as min(map, delegate), so it cannot get discarded
+// and then recreated by rewrapping the delegate.
+//
+// Optionally adds edges to the ephemeron edges table for any keys (or
+// delegates) where future changes to their mark color would require marking the
+// value (or the key).
+template <class K, class V>
+bool WeakMap<K, V>::markEntry(GCMarker* marker, K& key, V& value,
+                              bool populateWeakKeysTable) {
+#ifdef DEBUG
+  MOZ_ASSERT(mapColor);
+  if (marker->isParallelMarking()) {
+    marker->runtime()->gc.assertCurrentThreadHasLockedGC();
+  }
+#endif
+
+  bool marked = false;
+  CellColor markColor = marker->markColor();
+  CellColor keyColor = gc::detail::GetEffectiveColor(marker, key);
+  JSObject* delegate = gc::detail::GetDelegate(key);
+  JSTracer* trc = marker->tracer();
+
+  if (delegate) {
+    CellColor delegateColor = gc::detail::GetEffectiveColor(marker, delegate);
+    // The key needs to stay alive while both the delegate and map are live.
+    CellColor proxyPreserveColor = std::min(delegateColor, mapColor);
+    if (keyColor < proxyPreserveColor) {
+      MOZ_ASSERT(markColor >= proxyPreserveColor);
+      if (markColor == proxyPreserveColor) {
+        TraceWeakMapKeyEdge(trc, zone(), &key,
+                            "proxy-preserved WeakMap entry key");
+        MOZ_ASSERT(key->color() >= proxyPreserveColor);
+        marked = true;
+        keyColor = proxyPreserveColor;
+      }
+    }
+  }
+
+  gc::Cell* cellValue = gc::ToMarkable(value);
+  if (keyColor) {
+    if (cellValue) {
+      CellColor targetColor = std::min(mapColor, keyColor);
+      CellColor valueColor = gc::detail::GetEffectiveColor(marker, cellValue);
+      if (valueColor < targetColor) {
+        MOZ_ASSERT(markColor >= targetColor);
+        if (markColor == targetColor) {
+          TraceEdge(trc, &value, "WeakMap entry value");
+          MOZ_ASSERT(cellValue->color() >= targetColor);
+          marked = true;
+        }
+      }
+    }
+  }
+
+  if (populateWeakKeysTable) {
+    // Note that delegateColor >= keyColor because marking a key marks its
+    // delegate, so we only need to check whether keyColor < mapColor to tell
+    // this.
+
+    if (keyColor < mapColor) {
+      MOZ_ASSERT(trc->weakMapAction() == JS::WeakMapTraceAction::Expand);
+      // The final color of the key is not yet known. Record this weakmap and
+      // the lookup key in the list of weak keys. If the key has a delegate,
+      // then the lookup key is the delegate (because marking the key will end
+      // up marking the delegate and thereby mark the entry.)
+      gc::TenuredCell* tenuredValue = nullptr;
+      if (cellValue && cellValue->isTenured()) {
+        tenuredValue = &cellValue->asTenured();
+      }
+
+      if (!this->addImplicitEdges(key, delegate, tenuredValue)) {
+        marker->abortLinearWeakMarking();
+      }
+    }
+  }
+
+  return marked;
+}
+
+template <class K, class V>
+void WeakMap<K, V>::trace(JSTracer* trc) {
+  MOZ_ASSERT(isInList());
+
+  TraceNullableEdge(trc, &memberOf, "WeakMap owner");
+
+  if (trc->isMarkingTracer()) {
+    MOZ_ASSERT(trc->weakMapAction() == JS::WeakMapTraceAction::Expand);
+    auto marker = GCMarker::fromTracer(trc);
+
+    // Lock if we are marking in parallel to synchronize updates to:
+    //  - the weak map's color
+    //  - the ephemeron edges table
+    mozilla::Maybe<AutoLockGC> lock;
+    if (marker->isParallelMarking()) {
+      lock.emplace(marker->runtime());
+    }
+
+    // Don't downgrade the map color from black to gray. This can happen when a
+    // barrier pushes the map object onto the black mark stack when it's
+    // already present on the gray mark stack, which is marked later.
+    if (mapColor < marker->markColor()) {
+      mapColor = marker->markColor();
+      (void)markEntries(marker);
+    }
+    return;
+  }
+
+  if (trc->weakMapAction() == JS::WeakMapTraceAction::Skip) {
+    return;
+  }
+
+  // Trace keys only if weakMapAction() says to.
+  if (trc->weakMapAction() == JS::WeakMapTraceAction::TraceKeysAndValues) {
+    for (Enum e(*this); !e.empty(); e.popFront()) {
+      TraceWeakMapKeyEdge(trc, zone(), &e.front().mutableKey(),
+                          "WeakMap entry key");
+    }
+  }
+
+  // Always trace all values (unless weakMapAction() is Skip).
+  for (Range r = Base::all(); !r.empty(); r.popFront()) {
+    TraceEdge(trc, &r.front().value(), "WeakMap entry value");
+  }
+}
+
+bool WeakMapBase::addImplicitEdges(gc::Cell* key, gc::Cell* delegate,
+                                   gc::TenuredCell* value) {
+  if (delegate) {
+    auto& edgeTable = delegate->zone()->gcEphemeronEdges(delegate);
+    auto* p = edgeTable.get(delegate);
+
+    gc::EphemeronEdgeVector newVector;
+    gc::EphemeronEdgeVector& edges = p ? p->value : newVector;
+
+    // Add a <weakmap, delegate> -> key edge: the key must be preserved for
+    // future lookups until either the weakmap or the delegate dies.
+    gc::EphemeronEdge keyEdge{mapColor, key};
+    if (!edges.append(keyEdge)) {
+      return false;
+    }
+
+    if (value) {
+      gc::EphemeronEdge valueEdge{mapColor, value};
+      if (!edges.append(valueEdge)) {
+        return false;
+      }
+    }
+
+    if (!p) {
+      return edgeTable.put(delegate, std::move(newVector));
+    }
+
+    return true;
+  }
+
+  // No delegate. Insert just the key -> value edge.
+
+  if (!value) {
+    return true;
+  }
+
+  auto& edgeTable = key->zone()->gcEphemeronEdges(key);
+  auto* p = edgeTable.get(key);
+  gc::EphemeronEdge valueEdge{mapColor, value};
+  if (p) {
+    return p->value.append(valueEdge);
+  } else {
+    gc::EphemeronEdgeVector edges;
+    MOZ_ALWAYS_TRUE(edges.append(valueEdge));
+    return edgeTable.put(key, std::move(edges));
+  }
+}
+
+template <class K, class V>
+bool WeakMap<K, V>::markEntries(GCMarker* marker) {
+  // This method is called whenever the map's mark color changes. Mark values
+  // (and keys with delegates) as required for the new color and populate the
+  // ephemeron edges if we're in incremental marking mode.
+
+#ifdef DEBUG
+  if (marker->isParallelMarking()) {
+    marker->runtime()->gc.assertCurrentThreadHasLockedGC();
+  }
+#endif
+
+  MOZ_ASSERT(mapColor);
+  bool markedAny = false;
+
+  // If we don't populate the weak keys table now then we do it when we enter
+  // weak marking mode.
+  bool populateWeakKeysTable =
+      marker->incrementalWeakMapMarkingEnabled || marker->isWeakMarking();
+
+  for (Enum e(*this); !e.empty(); e.popFront()) {
+    if (markEntry(marker, e.front().mutableKey(), e.front().value(),
+                  populateWeakKeysTable)) {
+      markedAny = true;
+    }
+  }
+
+  return markedAny;
+}
+
+template <class K, class V>
+void WeakMap<K, V>::traceWeakEdges(JSTracer* trc) {
+  // Remove all entries whose keys remain unmarked.
+  for (Enum e(*this); !e.empty(); e.popFront()) {
+    if (!TraceWeakEdge(trc, &e.front().mutableKey(), "WeakMap key")) {
+      e.removeFront();
+    }
+  }
+
+#if DEBUG
+  // Once we've swept, all remaining edges should stay within the known-live
+  // part of the graph.
+  assertEntriesNotAboutToBeFinalized();
+#endif
+}
+
+// memberOf can be nullptr, which means that the map is not part of a JSObject.
+template <class K, class V>
+void WeakMap<K, V>::traceMappings(WeakMapTracer* tracer) {
+  for (Range r = Base::all(); !r.empty(); r.popFront()) {
+    gc::Cell* key = gc::ToMarkable(r.front().key());
+    gc::Cell* value = gc::ToMarkable(r.front().value());
+    if (key && value) {
+      tracer->trace(memberOf, JS::GCCellPtr(r.front().key().get()),
+                    JS::GCCellPtr(r.front().value().get()));
+    }
+  }
+}
+
+template <class K, class V>
+bool WeakMap<K, V>::findSweepGroupEdges() {
+  // For weakmap keys with delegates in a different zone, add a zone edge to
+  // ensure that the delegate zone finishes marking before the key zone.
+  JS::AutoSuppressGCAnalysis nogc;
+  for (Range r = all(); !r.empty(); r.popFront()) {
+    const K& key = r.front().key();
+
+    // If the key type doesn't have delegates, then this will always return
+    // nullptr and the optimizer can remove the entire body of this function.
+    JSObject* delegate = gc::detail::GetDelegate(key);
+    if (!delegate) {
+      continue;
+    }
+
+    // Marking a WeakMap key's delegate will mark the key, so process the
+    // delegate zone no later than the key zone.
+    Zone* delegateZone = delegate->zone();
+    Zone* keyZone = key->zone();
+    if (delegateZone != keyZone && delegateZone->isGCMarking() &&
+        keyZone->isGCMarking()) {
+      if (!delegateZone->addSweepGroupEdgeTo(keyZone)) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+template <class K, class V>
+size_t WeakMap<K, V>::sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) {
+  return mallocSizeOf(this) + shallowSizeOfExcludingThis(mallocSizeOf);
+}
+
+#if DEBUG
+template <class K, class V>
+void WeakMap<K, V>::assertEntriesNotAboutToBeFinalized() {
+  for (Range r = Base::all(); !r.empty(); r.popFront()) {
+    UnbarrieredKey k = r.front().key();
+    MOZ_ASSERT(!gc::IsAboutToBeFinalizedUnbarriered(k));
+    JSObject* delegate = gc::detail::GetDelegate(k);
+    if (delegate) {
+      MOZ_ASSERT(!gc::IsAboutToBeFinalizedUnbarriered(delegate),
+                 "weakmap marking depends on a key tracing its delegate");
+    }
+    MOZ_ASSERT(!gc::IsAboutToBeFinalized(r.front().value()));
+  }
+}
+#endif
+
+#ifdef JS_GC_ZEAL
+template <class K, class V>
+bool WeakMap<K, V>::checkMarking() const {
+  bool ok = true;
+  for (Range r = Base::all(); !r.empty(); r.popFront()) {
+    gc::Cell* key = gc::ToMarkable(r.front().key());
+    gc::Cell* value = gc::ToMarkable(r.front().value());
+    if (key && value) {
+      if (!gc::CheckWeakMapEntryMarking(this, key, value)) {
+        ok = false;
+      }
+    }
+  }
+  return ok;
+}
+#endif
+
+} /* namespace js */
+
+#endif /* gc_WeakMap_inl_h */