Adding upstream version 86.0.1.upstream/86.0.1upstream

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

1 files changed, 810 insertions, 0 deletions

diff --git a/js/src/frontend/ParserAtom.h b/js/src/frontend/ParserAtom.h
new file mode 100644
index 0000000000..a1f0b2318f
--- /dev/null
+++ b/js/src/frontend/ParserAtom.h
@@ -0,0 +1,810 @@
+/* -*- 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 frontend_ParserAtom_h
+#define frontend_ParserAtom_h
+
+#include "mozilla/DebugOnly.h"      // mozilla::DebugOnly
+#include "mozilla/HashFunctions.h"  // HashString
+#include "mozilla/Range.h"          // mozilla::Range
+#include "mozilla/Span.h"           // mozilla::Span
+#include "mozilla/Variant.h"        // mozilla::Variant
+
+#include "ds/LifoAlloc.h"         // LifoAlloc
+#include "frontend/TypedIndex.h"  // TypedIndex
+#include "js/HashTable.h"         // HashSet
+#include "js/UniquePtr.h"         // js::UniquePtr
+#include "js/Vector.h"            // Vector
+#include "vm/CommonPropertyNames.h"
+#include "vm/StringType.h"  // CompareChars, StringEqualsAscii
+
+namespace js {
+namespace frontend {
+
+struct CompilationAtomCache;
+struct CompilationStencil;
+class ParserAtom;
+class ParserName;
+
+template <typename CharT>
+class SpecificParserAtomLookup;
+
+class ParserAtomsTable;
+
+// An index to map WellKnownParserAtoms to cx->names().
+// This is consistent across multiple compilation.
+//
+// GetWellKnownAtom in ParserAtom.cpp relies on the fact that
+// JSAtomState fields and this enum variants use the same order.
+enum class WellKnownAtomId : uint32_t {
+#define ENUM_ENTRY_(_, name, _2) name,
+  FOR_EACH_COMMON_PROPERTYNAME(ENUM_ENTRY_)
+#undef ENUM_ENTRY_
+
+#define ENUM_ENTRY_(name, _) name,
+      JS_FOR_EACH_PROTOTYPE(ENUM_ENTRY_)
+#undef ENUM_ENTRY_
+          Limit,
+};
+
+// These types correspond into indices in the StaticStrings arrays.
+enum class StaticParserString1 : uint8_t;
+enum class StaticParserString2 : uint16_t;
+
+class ParserAtom;
+using ParserAtomIndex = TypedIndex<ParserAtom>;
+
+// ParserAtomIndex, WellKnownAtomId, StaticParserString1, StaticParserString2,
+// or null.
+//
+// 0x0000_0000  Null atom
+//
+// 0x1YYY_YYYY  28-bit ParserAtom
+//
+// 0x2000_YYYY  Well-known atom ID
+// 0x2001_YYYY  Static length-1 atom
+// 0x2002_YYYY  Static length-2 atom
+class TaggedParserAtomIndex {
+  uint32_t data_;
+
+ public:
+  static constexpr size_t IndexBit = 28;
+  static constexpr size_t IndexMask = BitMask(IndexBit);
+
+  static constexpr size_t TagShift = IndexBit;
+  static constexpr size_t TagBit = 4;
+  static constexpr size_t TagMask = BitMask(TagBit) << TagShift;
+
+  enum class Kind : uint32_t {
+    Null = 0,
+    ParserAtomIndex,
+    WellKnown,
+  };
+
+ private:
+  static constexpr size_t SmallIndexBit = 16;
+  static constexpr size_t SmallIndexMask = BitMask(SmallIndexBit);
+
+  static constexpr size_t SubTagShift = SmallIndexBit;
+  static constexpr size_t SubTagBit = 2;
+  static constexpr size_t SubTagMask = BitMask(SubTagBit) << SubTagShift;
+
+ public:
+  static constexpr uint32_t NullTag = uint32_t(Kind::Null) << TagShift;
+  static constexpr uint32_t ParserAtomIndexTag = uint32_t(Kind::ParserAtomIndex)
+                                                 << TagShift;
+  static constexpr uint32_t WellKnownTag = uint32_t(Kind::WellKnown)
+                                           << TagShift;
+
+ private:
+  static constexpr uint32_t WellKnownSubTag = 0 << SubTagShift;
+  static constexpr uint32_t Static1SubTag = 1 << SubTagShift;
+  static constexpr uint32_t Static2SubTag = 2 << SubTagShift;
+
+ public:
+  static constexpr uint32_t IndexLimit = Bit(IndexBit);
+  static constexpr uint32_t SmallIndexLimit = Bit(SmallIndexBit);
+
+ private:
+  explicit TaggedParserAtomIndex(uint32_t data) : data_(data) {}
+
+ public:
+  constexpr TaggedParserAtomIndex() : data_(NullTag) {}
+
+  explicit constexpr TaggedParserAtomIndex(ParserAtomIndex index)
+      : data_(index.index | ParserAtomIndexTag) {
+    MOZ_ASSERT(index.index < IndexLimit);
+  }
+  explicit constexpr TaggedParserAtomIndex(WellKnownAtomId index)
+      : data_(uint32_t(index) | WellKnownTag | WellKnownSubTag) {
+    MOZ_ASSERT(uint32_t(index) < SmallIndexLimit);
+
+    // Static1/Static2 string shouldn't use WellKnownAtomId.
+#define CHECK_(_, name, _2) MOZ_ASSERT(index != WellKnownAtomId::name);
+    FOR_EACH_NON_EMPTY_TINY_PROPERTYNAME(CHECK_)
+#undef CHECK_
+  }
+  explicit constexpr TaggedParserAtomIndex(StaticParserString1 index)
+      : data_(uint32_t(index) | WellKnownTag | Static1SubTag) {}
+  explicit constexpr TaggedParserAtomIndex(StaticParserString2 index)
+      : data_(uint32_t(index) | WellKnownTag | Static2SubTag) {}
+
+  static TaggedParserAtomIndex star() {
+    return TaggedParserAtomIndex(StaticParserString1('*'));
+  }
+  static TaggedParserAtomIndex arguments() {
+    return TaggedParserAtomIndex(WellKnownAtomId::arguments);
+  }
+  static TaggedParserAtomIndex dotThis() {
+    return TaggedParserAtomIndex(WellKnownAtomId::dotThis);
+  }
+  static TaggedParserAtomIndex dotGenerator() {
+    return TaggedParserAtomIndex(WellKnownAtomId::dotGenerator);
+  }
+  static TaggedParserAtomIndex null() { return TaggedParserAtomIndex(); }
+
+#ifdef DEBUG
+  void validateRaw();
+#endif
+
+  static TaggedParserAtomIndex fromRaw(uint32_t data) {
+    auto result = TaggedParserAtomIndex(data);
+#ifdef DEBUG
+    result.validateRaw();
+#endif
+    return result;
+  }
+
+  bool isParserAtomIndex() const {
+    return (data_ & TagMask) == ParserAtomIndexTag;
+  }
+  bool isWellKnownAtomId() const {
+    return (data_ & (TagMask | SubTagMask)) == (WellKnownTag | WellKnownSubTag);
+  }
+  bool isStaticParserString1() const {
+    return (data_ & (TagMask | SubTagMask)) == (WellKnownTag | Static1SubTag);
+  }
+  bool isStaticParserString2() const {
+    return (data_ & (TagMask | SubTagMask)) == (WellKnownTag | Static2SubTag);
+  }
+  bool isNull() const {
+    bool result = !data_;
+    MOZ_ASSERT_IF(result, (data_ & TagMask) == NullTag);
+    return result;
+  }
+
+  ParserAtomIndex toParserAtomIndex() const {
+    MOZ_ASSERT(isParserAtomIndex());
+    return ParserAtomIndex(data_ & IndexMask);
+  }
+  WellKnownAtomId toWellKnownAtomId() const {
+    MOZ_ASSERT(isWellKnownAtomId());
+    return WellKnownAtomId(data_ & SmallIndexMask);
+  }
+  StaticParserString1 toStaticParserString1() const {
+    MOZ_ASSERT(isStaticParserString1());
+    return StaticParserString1(data_ & SmallIndexMask);
+  }
+  StaticParserString2 toStaticParserString2() const {
+    MOZ_ASSERT(isStaticParserString2());
+    return StaticParserString2(data_ & SmallIndexMask);
+  }
+
+  uint32_t* rawData() { return &data_; }
+
+  bool operator==(const TaggedParserAtomIndex& rhs) const {
+    return data_ == rhs.data_;
+  }
+
+  explicit operator bool() const { return !isNull(); }
+};
+
+/**
+ * A ParserAtomEntry is an in-parser representation of an interned atomic
+ * string.  It mostly mirrors the information carried by a JSAtom*.
+ *
+ * The atom contents are stored in one of two locations:
+ *  1. Inline Latin1Char storage (immediately after the ParserAtomEntry memory).
+ *  2. Inline char16_t storage (immediately after the ParserAtomEntry memory).
+ */
+class alignas(alignof(uint32_t)) ParserAtomEntry {
+  friend class ParserAtomsTable;
+  friend class WellKnownParserAtoms;
+  friend class WellKnownParserAtoms_ROM;
+
+  static const uint16_t MAX_LATIN1_CHAR = 0xff;
+
+  // Bit flags inside flags_.
+  static constexpr uint32_t HasTwoByteCharsFlag = 1 << 0;
+  static constexpr uint32_t UsedByStencilFlag = 1 << 1;
+
+  // Helper routine to read some sequence of two-byte chars, and write them
+  // into a target buffer of a particular character width.
+  //
+  // The characters in the sequence must have been verified prior
+  template <typename CharT, typename SeqCharT>
+  static void drainChar16Seq(CharT* buf, InflatedChar16Sequence<SeqCharT> seq,
+                             uint32_t length) {
+    static_assert(
+        std::is_same_v<CharT, char16_t> || std::is_same_v<CharT, Latin1Char>,
+        "Invalid target buffer type.");
+    CharT* cur = buf;
+    while (seq.hasMore()) {
+      char16_t ch = seq.next();
+      if constexpr (std::is_same_v<CharT, Latin1Char>) {
+        MOZ_ASSERT(ch <= MAX_LATIN1_CHAR);
+      }
+      MOZ_ASSERT(cur < (buf + length));
+      *cur = ch;
+      cur++;
+    }
+  }
+
+ private:
+  // The JSAtom-compatible hash of the string.
+  HashNumber hash_ = 0;
+
+  // The length of the buffer in chars_.
+  uint32_t length_ = 0;
+
+  TaggedParserAtomIndex index_;
+
+  uint32_t flags_ = 0;
+
+  // End of fields.
+
+  static const uint32_t MAX_LENGTH = JSString::MAX_LENGTH;
+
+  ParserAtomEntry(uint32_t length, HashNumber hash, bool hasTwoByteChars)
+      : hash_(hash),
+        length_(length),
+        flags_(hasTwoByteChars ? HasTwoByteCharsFlag : 0) {}
+
+ public:
+  // The constexpr constructor is used by StaticParserAtomEntry and XDR
+  constexpr ParserAtomEntry() = default;
+
+  // ParserAtomEntries may own their content buffers in variant_, and thus
+  // cannot be copy-constructed - as a new chars would need to be allocated.
+  ParserAtomEntry(const ParserAtomEntry&) = delete;
+  ParserAtomEntry(ParserAtomEntry&& other) = delete;
+
+  template <typename CharT, typename SeqCharT>
+  static ParserAtomEntry* allocate(JSContext* cx, LifoAlloc& alloc,
+                                   InflatedChar16Sequence<SeqCharT> seq,
+                                   uint32_t length, HashNumber hash);
+
+  static ParserAtomEntry* allocateRaw(JSContext* cx, LifoAlloc& alloc,
+                                      const uint8_t* srcRaw,
+                                      size_t totalLength);
+
+  ParserAtom* asAtom() { return reinterpret_cast<ParserAtom*>(this); }
+  const ParserAtom* asAtom() const {
+    return reinterpret_cast<const ParserAtom*>(this);
+  }
+
+  inline ParserName* asName();
+  inline const ParserName* asName() const;
+
+  bool hasLatin1Chars() const { return !(flags_ & HasTwoByteCharsFlag); }
+  bool hasTwoByteChars() const { return flags_ & HasTwoByteCharsFlag; }
+
+  template <typename CharT>
+  const CharT* chars() const {
+    MOZ_ASSERT(sizeof(CharT) == (hasTwoByteChars() ? 2 : 1));
+    return reinterpret_cast<const CharT*>(this + 1);
+  }
+
+  template <typename CharT>
+  CharT* chars() {
+    MOZ_ASSERT(sizeof(CharT) == (hasTwoByteChars() ? 2 : 1));
+    return reinterpret_cast<CharT*>(this + 1);
+  }
+
+  const Latin1Char* latin1Chars() const { return chars<Latin1Char>(); }
+  const char16_t* twoByteChars() const { return chars<char16_t>(); }
+  mozilla::Range<const Latin1Char> latin1Range() const {
+    return mozilla::Range(latin1Chars(), length_);
+  }
+  mozilla::Range<const char16_t> twoByteRange() const {
+    return mozilla::Range(twoByteChars(), length_);
+  }
+
+  bool isIndex(uint32_t* indexp) const;
+  bool isIndex() const {
+    uint32_t index;
+    return isIndex(&index);
+  }
+
+  bool isAscii() const {
+    if (hasTwoByteChars()) {
+      return false;
+    }
+    for (Latin1Char ch : latin1Range()) {
+      if (!mozilla::IsAscii(ch)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  HashNumber hash() const { return hash_; }
+  uint32_t length() const { return length_; }
+
+  bool isUsedByStencil() const { return flags_ & UsedByStencilFlag; }
+  void markUsedByStencil() const {
+    if (isParserAtomIndex()) {
+      // Use const method + const_cast here to avoid marking static strings'
+      // field mutable.
+      const_cast<ParserAtomEntry*>(this)->flags_ |= UsedByStencilFlag;
+    }
+  }
+
+  bool equalsJSAtom(JSAtom* other) const;
+
+  template <typename CharT>
+  bool equalsSeq(HashNumber hash, InflatedChar16Sequence<CharT> seq) const;
+
+  TaggedParserAtomIndex toIndex() const { return index_; }
+
+  ParserAtomIndex toParserAtomIndex() const {
+    return index_.toParserAtomIndex();
+  }
+  WellKnownAtomId toWellKnownAtomId() const {
+    return index_.toWellKnownAtomId();
+  }
+  StaticParserString1 toStaticParserString1() const {
+    return index_.toStaticParserString1();
+  }
+  StaticParserString2 toStaticParserString2() const {
+    return index_.toStaticParserString2();
+  }
+
+  bool isParserAtomIndex() const { return index_.isParserAtomIndex(); }
+  bool isWellKnownAtomId() const { return index_.isWellKnownAtomId(); }
+  bool isStaticParserString1() const { return index_.isStaticParserString1(); }
+  bool isStaticParserString2() const { return index_.isStaticParserString2(); }
+
+  void setParserAtomIndex(ParserAtomIndex index) {
+    index_ = TaggedParserAtomIndex(index);
+  }
+
+ private:
+  constexpr void setWellKnownAtomId(WellKnownAtomId atomId) {
+    index_ = TaggedParserAtomIndex(atomId);
+  }
+  constexpr void setStaticParserString1(StaticParserString1 s) {
+    index_ = TaggedParserAtomIndex(s);
+  }
+  constexpr void setStaticParserString2(StaticParserString2 s) {
+    index_ = TaggedParserAtomIndex(s);
+  }
+  constexpr void setHashAndLength(HashNumber hash, uint32_t length) {
+    hash_ = hash;
+    length_ = length;
+  }
+
+ public:
+  // Convert this entry to a js-atom.  The first time this method is called
+  // the entry will cache the JSAtom pointer to return later.
+  JSAtom* toJSAtom(JSContext* cx, CompilationAtomCache& atomCache) const;
+
+  // Same as toJSAtom, but this is guaranteed to be instantiated.
+  JSAtom* toExistingJSAtom(JSContext* cx,
+                           CompilationAtomCache& atomCache) const;
+
+  // Convert NotInstantiated and usedByStencil entry to a js-atom.
+  JSAtom* instantiate(JSContext* cx, CompilationAtomCache& atomCache) const;
+
+  // Convert this entry to a number.
+  bool toNumber(JSContext* cx, double* result) const;
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+  void dump() const;
+  void dumpCharsNoQuote(js::GenericPrinter& out) const;
+#endif
+};
+
+class ParserAtom : public ParserAtomEntry {
+  ParserAtom() = delete;
+  ParserAtom(const ParserAtom&) = delete;
+};
+
+class ParserName : public ParserAtom {
+  ParserName() = delete;
+  ParserName(const ParserName&) = delete;
+};
+
+UniqueChars ParserAtomToPrintableString(JSContext* cx, const ParserAtom* atom);
+
+inline ParserName* ParserAtomEntry::asName() {
+  MOZ_ASSERT(!isIndex());
+  return static_cast<ParserName*>(this);
+}
+inline const ParserName* ParserAtomEntry::asName() const {
+  MOZ_ASSERT(!isIndex());
+  return static_cast<const ParserName*>(this);
+}
+
+// A ParserAtomEntry with explicit inline storage. This is compatible with
+// constexpr to have builtin atoms. Care must be taken to ensure these atoms are
+// unique.
+template <size_t Length>
+class StaticParserAtomEntry : public ParserAtomEntry {
+  alignas(alignof(ParserAtomEntry)) char storage_[Length] = {};
+
+ public:
+  constexpr StaticParserAtomEntry() = default;
+
+  constexpr char* storage() {
+    static_assert(
+        offsetof(StaticParserAtomEntry, storage_) == sizeof(ParserAtomEntry),
+        "StaticParserAtomEntry storage should follow ParserAtomEntry");
+    return storage_;
+  }
+};
+
+template <>
+class StaticParserAtomEntry<0> : public ParserAtomEntry {
+ public:
+  constexpr StaticParserAtomEntry() = default;
+};
+
+/**
+ * A lookup structure that allows for querying ParserAtoms in
+ * a hashtable using a flexible input type that supports string
+ * representations of various forms.
+ */
+class ParserAtomLookup {
+ protected:
+  HashNumber hash_;
+
+  ParserAtomLookup(HashNumber hash) : hash_(hash) {}
+
+ public:
+  HashNumber hash() const { return hash_; }
+
+  virtual bool equalsEntry(const ParserAtomEntry* entry) const = 0;
+};
+
+struct ParserAtomLookupHasher {
+  using Lookup = ParserAtomLookup;
+
+  static inline HashNumber hash(const Lookup& l) { return l.hash(); }
+  static inline bool match(const ParserAtomEntry* entry, const Lookup& l) {
+    return l.equalsEntry(entry);
+  }
+};
+
+// We use this class to build a read-only constexpr table of ParserAtoms for the
+// well-known atoms set. This should be resolved at compile-time (including hash
+// computation) thanks to C++ constexpr.
+class WellKnownParserAtoms_ROM {
+  // NOTE: While the well-known strings are all Latin1, we must use char16_t in
+  //       some places in order to have constexpr mozilla::HashString.
+  using CharTraits = std::char_traits<char>;
+  using Char16Traits = std::char_traits<char16_t>;
+
+ public:
+  static const size_t ASCII_STATIC_LIMIT = 128U;
+  static const size_t NUM_SMALL_CHARS = StaticStrings::NUM_SMALL_CHARS;
+  static const size_t NUM_LENGTH2_ENTRIES = NUM_SMALL_CHARS * NUM_SMALL_CHARS;
+
+  StaticParserAtomEntry<0> emptyAtom;
+  StaticParserAtomEntry<1> length1Table[ASCII_STATIC_LIMIT];
+  StaticParserAtomEntry<2> length2Table[NUM_LENGTH2_ENTRIES];
+
+#define PROPERTYNAME_FIELD_(_, name, text) \
+  StaticParserAtomEntry<CharTraits::length(text)> name;
+  FOR_EACH_NONTINY_COMMON_PROPERTYNAME(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+
+#define PROPERTYNAME_FIELD_(name, _) \
+  StaticParserAtomEntry<CharTraits::length(#name)> name;
+  JS_FOR_EACH_PROTOTYPE(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+
+ public:
+  constexpr WellKnownParserAtoms_ROM() {
+    // Empty atom
+    emptyAtom.setHashAndLength(mozilla::HashString(u""), 0);
+    emptyAtom.setWellKnownAtomId(WellKnownAtomId::empty);
+
+    // Length-1 static atoms
+    for (size_t i = 0; i < ASCII_STATIC_LIMIT; ++i) {
+      init(length1Table[i], i);
+    }
+
+    // Length-2 static atoms
+    for (size_t i = 0; i < NUM_LENGTH2_ENTRIES; ++i) {
+      init(length2Table[i], i);
+    }
+
+    // Initialize each well-known property atoms
+#define PROPERTYNAME_FIELD_(_, name, text) \
+  init(name, name.storage(), u"" text, WellKnownAtomId::name);
+    FOR_EACH_NONTINY_COMMON_PROPERTYNAME(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+
+    // Initialize each well-known prototype atoms
+#define PROPERTYNAME_FIELD_(name, _) \
+  init(name, name.storage(), u"" #name, WellKnownAtomId::name);
+    JS_FOR_EACH_PROTOTYPE(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+  }
+
+ private:
+  // Initialization moved out of the constructor to workaround bug 1668238.
+  static constexpr void init(StaticParserAtomEntry<1>& entry, size_t i) {
+    size_t len = 1;
+    char16_t buf[] = {static_cast<char16_t>(i),
+                      /* null-terminator */ 0};
+    entry.setHashAndLength(mozilla::HashString(buf), len);
+    entry.setStaticParserString1(StaticParserString1(i));
+    entry.storage()[0] = buf[0];
+  }
+
+  static constexpr void init(StaticParserAtomEntry<2>& entry, size_t i) {
+    size_t len = 2;
+    char16_t buf[] = {StaticStrings::fromSmallChar(i >> 6),
+                      StaticStrings::fromSmallChar(i & 0x003F),
+                      /* null-terminator */ 0};
+    entry.setHashAndLength(mozilla::HashString(buf), len);
+    entry.setStaticParserString2(StaticParserString2(i));
+    entry.storage()[0] = buf[0];
+    entry.storage()[1] = buf[1];
+  }
+
+  static constexpr void init(ParserAtomEntry& entry, char* storage,
+                             const char16_t* text, WellKnownAtomId id) {
+    size_t len = Char16Traits::length(text);
+    entry.setHashAndLength(mozilla::HashString(text), len);
+    entry.setWellKnownAtomId(id);
+    for (size_t i = 0; i < len; ++i) {
+      storage[i] = text[i];
+    }
+  }
+
+ public:
+  // Fast-path tiny strings since they are abundant in minified code.
+  template <typename CharsT>
+  const ParserAtom* lookupTiny(CharsT chars, size_t length) const {
+    static_assert(std::is_same_v<CharsT, const Latin1Char*> ||
+                      std::is_same_v<CharsT, const char16_t*> ||
+                      std::is_same_v<CharsT, const char*> ||
+                      std::is_same_v<CharsT, char16_t*> ||
+                      std::is_same_v<CharsT, LittleEndianChars>,
+                  "This assert mostly explicitly documents the calling types, "
+                  "and forces that to be updated if new types show up.");
+    switch (length) {
+      case 0:
+        return emptyAtom.asAtom();
+
+      case 1: {
+        if (char16_t(chars[0]) < ASCII_STATIC_LIMIT) {
+          size_t index = static_cast<size_t>(chars[0]);
+          return length1Table[index].asAtom();
+        }
+        break;
+      }
+
+      case 2:
+        if (StaticStrings::fitsInSmallChar(chars[0]) &&
+            StaticStrings::fitsInSmallChar(chars[1])) {
+          size_t index = StaticStrings::getLength2Index(chars[0], chars[1]);
+          return length2Table[index].asAtom();
+        }
+        break;
+    }
+
+    // No match on tiny Atoms
+    return nullptr;
+  }
+};
+
+using ParserAtomVector = Vector<ParserAtomEntry*, 0, js::SystemAllocPolicy>;
+using ParserAtomSpan = mozilla::Span<ParserAtomEntry*>;
+
+/**
+ * WellKnownParserAtoms reserves a set of common ParserAtoms on the JSRuntime
+ * in a read-only format to be used by parser. These reserved atoms can be
+ * translated to equivalent JSAtoms in constant time.
+ *
+ * The common-names set allows the parser to lookup up specific atoms in
+ * constant time.
+ *
+ * We also reserve tiny (length 1/2) parser-atoms for fast lookup similar to
+ * the js::StaticStrings mechanism. This speeds up parsing minified code.
+ */
+class WellKnownParserAtoms {
+ public:
+  // Named fields allow quickly finding an atom if it is known at compile time.
+  // This is particularly useful for the Parser.
+#define PROPERTYNAME_FIELD_(_, name, _2) const ParserName* name{};
+  FOR_EACH_COMMON_PROPERTYNAME(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+
+#define PROPERTYNAME_FIELD_(name, _) const ParserName* name{};
+  JS_FOR_EACH_PROTOTYPE(PROPERTYNAME_FIELD_)
+#undef PROPERTYNAME_FIELD_
+
+  // The ParserAtomEntry of all well-known and tiny ParserAtoms are generated at
+  // compile-time into a ROM that is computed using constexpr. This results in
+  // the data being in the .rodata section of binary and easily shared by
+  // multiple JS processes.
+  static constexpr WellKnownParserAtoms_ROM rom_ = {};
+
+  // Common property and prototype names are tracked in a hash table. This table
+  // does not key for any items already in a direct-indexing tiny atom table.
+  using EntrySet = HashSet<const ParserAtomEntry*, ParserAtomLookupHasher,
+                           js::SystemAllocPolicy>;
+  EntrySet wellKnownSet_;
+
+  bool initTinyStringAlias(JSContext* cx, const ParserName** name,
+                           const char* str);
+  bool initSingle(JSContext* cx, const ParserName** name,
+                  const ParserAtomEntry& romEntry);
+
+ public:
+  bool init(JSContext* cx);
+
+  // Maximum length of any well known atoms. This can be increased if needed.
+  static constexpr size_t MaxWellKnownLength = 32;
+
+  template <typename CharT>
+  const ParserAtom* lookupChar16Seq(
+      const SpecificParserAtomLookup<CharT>& lookup) const;
+
+  template <typename CharsT>
+  const ParserAtom* lookupTiny(CharsT chars, size_t length) const {
+    return rom_.lookupTiny(chars, length);
+  }
+
+  const ParserAtom* getWellKnown(WellKnownAtomId atomId) const;
+  static const ParserAtom* getStatic1(StaticParserString1 s);
+  static const ParserAtom* getStatic2(StaticParserString2 s);
+};
+
+bool InstantiateMarkedAtoms(JSContext* cx, const ParserAtomSpan& entries,
+                            CompilationAtomCache& atomCache);
+
+/**
+ * A ParserAtomsTable owns and manages the vector of ParserAtom entries
+ * associated with a given compile session.
+ */
+class ParserAtomsTable {
+ private:
+  const WellKnownParserAtoms& wellKnownTable_;
+
+  LifoAlloc& alloc_;
+
+  // The ParserAtomEntry are owned by the LifoAlloc.
+  using EntrySet = HashSet<const ParserAtomEntry*, ParserAtomLookupHasher,
+                           js::SystemAllocPolicy>;
+  EntrySet entrySet_;
+  ParserAtomVector entries_;
+
+ public:
+  ParserAtomsTable(JSRuntime* rt, LifoAlloc& alloc);
+  ParserAtomsTable(ParserAtomsTable&&) = default;
+
+ private:
+  // Internal APIs for interning to the table after well-known atoms cases have
+  // been tested.
+  const ParserAtom* addEntry(JSContext* cx, EntrySet::AddPtr& addPtr,
+                             ParserAtomEntry* entry);
+  template <typename AtomCharT, typename SeqCharT>
+  const ParserAtom* internChar16Seq(JSContext* cx, EntrySet::AddPtr& addPtr,
+                                    HashNumber hash,
+                                    InflatedChar16Sequence<SeqCharT> seq,
+                                    uint32_t length);
+
+ public:
+  const ParserAtom* internAscii(JSContext* cx, const char* asciiPtr,
+                                uint32_t length);
+
+  const ParserAtom* internLatin1(JSContext* cx, const JS::Latin1Char* latin1Ptr,
+                                 uint32_t length);
+
+  const ParserAtom* internUtf8(JSContext* cx, const mozilla::Utf8Unit* utf8Ptr,
+                               uint32_t nbyte);
+
+  const ParserAtom* internChar16(JSContext* cx, const char16_t* char16Ptr,
+                                 uint32_t length);
+
+  const ParserAtom* internJSAtom(JSContext* cx, CompilationStencil& stencil,
+                                 JSAtom* atom);
+
+  const ParserAtom* concatAtoms(JSContext* cx,
+                                mozilla::Range<const ParserAtom*> atoms);
+
+  const ParserAtom* getWellKnown(WellKnownAtomId atomId) const;
+  const ParserAtom* getStatic1(StaticParserString1 s) const;
+  const ParserAtom* getStatic2(StaticParserString2 s) const;
+  const ParserAtom* getParserAtom(ParserAtomIndex index) const;
+  const ParserAtom* getParserAtom(TaggedParserAtomIndex index) const;
+
+  const ParserAtomVector& entries() const { return entries_; }
+};
+
+// Lightweight version of ParserAtomsTable.
+// This doesn't support deduplication.
+// Used while decoding XDR.
+class ParserAtomSpanBuilder {
+ private:
+  const WellKnownParserAtoms& wellKnownTable_;
+  ParserAtomSpan& entries_;
+
+ public:
+  ParserAtomSpanBuilder(JSRuntime* rt, ParserAtomSpan& entries);
+
+  bool allocate(JSContext* cx, LifoAlloc& alloc, size_t count);
+  size_t size() const { return entries_.size(); }
+
+  void set(ParserAtomIndex index, const ParserAtomEntry* atom) {
+    entries_[index] = const_cast<ParserAtomEntry*>(atom);
+  }
+
+ public:
+  const ParserAtom* getWellKnown(WellKnownAtomId atomId) const;
+  const ParserAtom* getStatic1(StaticParserString1 s) const;
+  const ParserAtom* getStatic2(StaticParserString2 s) const;
+  const ParserAtom* getParserAtom(ParserAtomIndex index) const;
+  const ParserAtom* getParserAtom(TaggedParserAtomIndex index) const;
+};
+
+template <typename CharT>
+class SpecificParserAtomLookup : public ParserAtomLookup {
+  // The sequence of characters to look up.
+  InflatedChar16Sequence<CharT> seq_;
+
+ public:
+  explicit SpecificParserAtomLookup(const InflatedChar16Sequence<CharT>& seq)
+      : SpecificParserAtomLookup(seq, seq.computeHash()) {}
+
+  SpecificParserAtomLookup(const InflatedChar16Sequence<CharT>& seq,
+                           HashNumber hash)
+      : ParserAtomLookup(hash), seq_(seq) {
+    MOZ_ASSERT(seq_.computeHash() == hash);
+  }
+
+  virtual bool equalsEntry(const ParserAtomEntry* entry) const override {
+    return entry->equalsSeq<CharT>(hash_, seq_);
+  }
+};
+
+template <typename CharT>
+inline bool ParserAtomEntry::equalsSeq(
+    HashNumber hash, InflatedChar16Sequence<CharT> seq) const {
+  // Compare hashes first.
+  if (hash_ != hash) {
+    return false;
+  }
+
+  if (hasTwoByteChars()) {
+    const char16_t* chars = twoByteChars();
+    for (uint32_t i = 0; i < length_; i++) {
+      if (!seq.hasMore() || chars[i] != seq.next()) {
+        return false;
+      }
+    }
+  } else {
+    const Latin1Char* chars = latin1Chars();
+    for (uint32_t i = 0; i < length_; i++) {
+      if (!seq.hasMore() || char16_t(chars[i]) != seq.next()) {
+        return false;
+      }
+    }
+  }
+  return !seq.hasMore();
+}
+
+JSAtom* GetWellKnownAtom(JSContext* cx, WellKnownAtomId atomId);
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif  // frontend_ParserAtom_h