1 files changed, 95 insertions, 0 deletions
diff --git a/js/src/gc/AtomMarking-inl.h b/js/src/gc/AtomMarking-inl.h
new file mode 100644
index 0000000000..908a11e7da
--- /dev/null
+++ b/js/src/gc/AtomMarking-inl.h
@@ -0,0 +1,95 @@
+/* -*- 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/. */
+
+#include "gc/AtomMarking.h"
+
+#include "mozilla/Assertions.h"
+
+#include <type_traits>
+
+#include "vm/JSContext.h"
+#include "vm/StringType.h"
+#include "vm/SymbolType.h"
+
+#include "gc/Heap-inl.h"
+
+namespace js {
+namespace gc {
+
+inline size_t GetAtomBit(TenuredCell* thing) {
+  MOZ_ASSERT(thing->zoneFromAnyThread()->isAtomsZone());
+  Arena* arena = thing->arena();
+  size_t arenaBit = (reinterpret_cast<uintptr_t>(thing) - arena->address()) /
+                    CellBytesPerMarkBit;
+  return arena->atomBitmapStart() * JS_BITS_PER_WORD + arenaBit;
+}
+
+template <typename T, bool Fallible>
+MOZ_ALWAYS_INLINE bool AtomMarkingRuntime::inlinedMarkAtomInternal(
+    JSContext* cx, T* thing) {
+  static_assert(std::is_same_v<T, JSAtom> || std::is_same_v<T, JS::Symbol>,
+                "Should only be called with JSAtom* or JS::Symbol* argument");
+
+  MOZ_ASSERT(cx->zone());
+  MOZ_ASSERT(!cx->zone()->isAtomsZone());
+
+  MOZ_ASSERT(thing);
+  js::gc::TenuredCell* cell = &thing->asTenured();
+  MOZ_ASSERT(cell->zoneFromAnyThread()->isAtomsZone());
+
+  // This doesn't check for pinned atoms since that might require taking a
+  // lock. This is not required for correctness.
+  if (thing->isPermanentAndMayBeShared()) {
+    return true;
+  }
+
+  size_t bit = GetAtomBit(cell);
+  MOZ_ASSERT(bit / JS_BITS_PER_WORD < allocatedWords);
+
+  if (Fallible) {
+    if (!cx->zone()->markedAtoms().setBitFallible(bit)) {
+      return false;
+    }
+  } else {
+    cx->zone()->markedAtoms().setBit(bit);
+  }
+
+  // Trigger a read barrier on the atom, in case there is an incremental
+  // GC in progress. This is necessary if the atom is being marked
+  // because a reference to it was obtained from another zone which is
+  // not being collected by the incremental GC.
+  ReadBarrier(thing);
+
+  // Children of the thing also need to be marked in the context's zone.
+  // We don't have a JSTracer for this so manually handle the cases in which
+  // an atom can reference other atoms.
+  markChildren(cx, thing);
+
+  return true;
+}
+
+void AtomMarkingRuntime::markChildren(JSContext* cx, JSAtom*) {}
+
+void AtomMarkingRuntime::markChildren(JSContext* cx, JS::Symbol* symbol) {
+  if (JSAtom* description = symbol->description()) {
+    markAtom(cx, description);
+  }
+}
+
+template <typename T>
+MOZ_ALWAYS_INLINE void AtomMarkingRuntime::inlinedMarkAtom(JSContext* cx,
+                                                           T* thing) {
+  MOZ_ALWAYS_TRUE((inlinedMarkAtomInternal<T, false>(cx, thing)));
+}
+
+template <typename T>
+MOZ_ALWAYS_INLINE bool AtomMarkingRuntime::inlinedMarkAtomFallible(
+    JSContext* cx, T* thing) {
+  return inlinedMarkAtomInternal<T, true>(cx, thing);
+}
+
+}  // namespace gc
+}  // namespace js