Bug 1645845 - Add ParserAtomsTable, parser atoms types, common parser names table, and base parser atoms implementation. r=mgaudet,tcampbell

Differential Revision: https://phabricator.services.mozilla.com/D79714

js/moz.configure

@@ -62,6 +62,12 @@ set_define('JS_64BIT', depends(target)(lambda t: t.bitness == 64 or None))
 set_define('JS_PUNBOX64', depends(target)(lambda t: t.bitness == 64 or None))
 set_define('JS_NUNBOX32', depends(target)(lambda t: t.bitness == 32 or None))
 
+# Bits of Stencil-related parser-atoms work are being landed before
+# being enabled.  This define controls that code, and will be removed,
+# along with guard code in ParserAtoms.cpp, when the final transition
+# to parser atoms lands.
+set_define('JS_PARSER_ATOMS', None)
+
 
 # SpiderMonkey as a shared library, and how its symbols are exported
 # ==================================================================

js/public/Utility.h

@@ -21,6 +21,7 @@
 
 #include "jstypes.h"
 #include "mozmemory.h"
+#include "js/TypeDecls.h"
 
 /* The public JS engine namespace. */
 namespace JS {}
@@ -650,6 +651,7 @@ struct FreePolicy {
 
 typedef mozilla::UniquePtr<char[], JS::FreePolicy> UniqueChars;
 typedef mozilla::UniquePtr<char16_t[], JS::FreePolicy> UniqueTwoByteChars;
+typedef mozilla::UniquePtr<JS::Latin1Char[], JS::FreePolicy> UniqueLatin1Chars;
 
 }  // namespace JS
 

js/src/NamespaceImports.h

@@ -74,6 +74,7 @@ using JS::Latin1CharsZ;
 using JS::TwoByteChars;
 using JS::TwoByteCharsZ;
 using JS::UniqueChars;
+using JS::UniqueLatin1Chars;
 using JS::UniqueTwoByteChars;
 using JS::UTF8Chars;
 using JS::UTF8CharsZ;

js/src/frontend/CompilationInfo.h

@@ -12,6 +12,7 @@
 #include "mozilla/Variant.h"
 
 #include "ds/LifoAlloc.h"
+#include "frontend/ParserAtom.h"
 #include "frontend/SharedContext.h"
 #include "frontend/Stencil.h"
 #include "frontend/UsedNameTracker.h"
@@ -75,6 +76,9 @@ struct MOZ_RAII CompilationInfo : public JS::CustomAutoRooter {
   // onto them.
   AutoKeepAtoms keepAtoms;
 
+  // Table of parser atoms for this compilation.
+  ParserAtomsTable parserAtoms;
+
   Directives directives;
 
   ScopeContext scopeContext;
@@ -142,6 +146,7 @@ struct MOZ_RAII CompilationInfo : public JS::CustomAutoRooter {
         cx(cx),
         options(options),
         keepAtoms(cx),
+        parserAtoms(cx),
         directives(options.forceStrictMode()),
         scopeContext(enclosingScope, enclosingEnv),
         script(cx),

js/src/frontend/ParserAtom.cpp

@@ -0,0 +1,442 @@
+/* -*- 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 "frontend/ParserAtom.h"
+
+#include <type_traits>
+
+#include "jsnum.h"
+
+#include "frontend/NameCollections.h"
+#include "vm/JSContext.h"
+#include "vm/Printer.h"
+#include "vm/Runtime.h"
+#include "vm/StringType.h"
+
+//
+// Parser-Atoms should be disabled for now.  This check ensures that.
+// NOTE: This will be removed when the final transition patches from
+//   JS-atoms to parser-atoms lands.
+//
+#ifdef JS_PARSER_ATOMS
+#  error "Parser atoms define should remain disabled until this is removed."
+#endif
+
+using namespace js;
+using namespace js::frontend;
+
+namespace js {
+namespace frontend {
+
+static JS::OOM PARSER_ATOMS_OOM;
+
+mozilla::GenericErrorResult<OOM&> RaiseParserAtomsOOMError(JSContext* cx) {
+  js::ReportOutOfMemory(cx);
+  return mozilla::Err(PARSER_ATOMS_OOM);
+}
+
+bool ParserAtomEntry::equalsJSAtom(JSAtom* other) const {
+  // Compare hashes first.
+  if (hash_ != other->hash()) {
+    return false;
+  }
+  if (length_ != other->length()) {
+    return false;
+  }
+
+  JS::AutoCheckCannotGC nogc;
+
+  if (hasTwoByteChars()) {
+    // Compare heap-allocated 16-bit chars to atom.
+    return other->hasLatin1Chars()
+               ? EqualChars(twoByteChars(), other->latin1Chars(nogc), length_)
+               : EqualChars(twoByteChars(), other->twoByteChars(nogc), length_);
+  }
+
+  MOZ_ASSERT(hasLatin1Chars());
+  return other->hasLatin1Chars()
+             ? EqualChars(latin1Chars(), other->latin1Chars(nogc), length_)
+             : EqualChars(latin1Chars(), other->twoByteChars(nogc), length_);
+}
+
+UniqueChars ParserAtomToPrintableString(JSContext* cx, ParserAtomId atom) {
+  const ParserAtomEntry* entry = atom.entry();
+  Sprinter sprinter(cx);
+  if (!sprinter.init()) {
+    return nullptr;
+  }
+  size_t length = entry->length();
+  if (entry->hasLatin1Chars()) {
+    if (!QuoteString<QuoteTarget::String>(
+            &sprinter, mozilla::Range(entry->latin1Chars(), length))) {
+      return nullptr;
+    }
+  } else {
+    if (!QuoteString<QuoteTarget::String>(
+            &sprinter, mozilla::Range(entry->twoByteChars(), length))) {
+      return nullptr;
+    }
+  }
+  return sprinter.release();
+}
+
+bool ParserAtomEntry::isIndex(uint32_t* indexp) const {
+  if (hasLatin1Chars()) {
+    return js::CheckStringIsIndex(latin1Chars(), length(), indexp);
+  }
+  return js::CheckStringIsIndex(twoByteChars(), length(), indexp);
+}
+
+JS::Result<JSAtom*, OOM&> ParserAtomEntry::toJSAtom(JSContext* cx) const {
+  if (jsatom_) {
+    return jsatom_;
+  }
+
+  if (hasLatin1Chars()) {
+    jsatom_ = AtomizeChars(cx, latin1Chars(), length());
+  } else {
+    jsatom_ = AtomizeChars(cx, twoByteChars(), length());
+  }
+  if (!jsatom_) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  return jsatom_;
+}
+
+bool ParserAtomEntry::toNumber(JSContext* cx, double* result) const {
+  return hasLatin1Chars() ? CharsToNumber(cx, latin1Chars(), length(), result)
+                          : CharsToNumber(cx, twoByteChars(), length(), result);
+}
+
+ParserAtomsTable::ParserAtomsTable(JSContext* cx)
+    : entrySet_(cx), wellKnownTable_(*cx->runtime()->commonParserNames) {}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::addEntry(
+    JSContext* cx, EntrySet::AddPtr addPtr, ParserAtomEntry&& entry) {
+  UniquePtr<ParserAtomEntry> uniqueEntry(
+      cx->new_<ParserAtomEntry>(std::move(entry)));
+  if (!uniqueEntry) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  ParserAtomEntry* entryPtr = uniqueEntry.get();
+
+  if (!entrySet_.add(addPtr, std::move(uniqueEntry))) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  ParserAtomId id(entryPtr);
+
+  return id;
+}
+
+static const uint16_t MAX_LATIN1_CHAR = 0xff;
+
+template <typename CharT, typename InCharT>
+static void DrainChar16Seq(CharT* buf, InflatedChar16Sequence<InCharT> seq) {
+  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);
+    }
+    *cur = ch;
+    cur++;
+  }
+}
+
+template <typename AtomCharT, typename SeqCharT>
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internChar16Seq(
+    JSContext* cx, EntrySet::AddPtr add, InflatedChar16Sequence<SeqCharT> seq,
+    uint32_t length, HashNumber hash) {
+  using UniqueCharsT = mozilla::UniquePtr<AtomCharT[], JS::FreePolicy>;
+  UniqueCharsT copy(cx->pod_malloc<AtomCharT>(length));
+  if (!copy) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  DrainChar16Seq<AtomCharT, SeqCharT>(copy.get(), seq);
+  ParserAtomEntry ent = ParserAtomEntry::make(std::move(copy), length, hash);
+  return addEntry(cx, add, std::move(ent));
+}
+
+template <typename CharT>
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::lookupOrInternChar16Seq(
+    JSContext* cx, InflatedChar16Sequence<CharT> seq) {
+  // Check against well-known.
+  ParserAtomId wk = wellKnownTable_.lookupChar16Seq(seq);
+  if (wk) {
+    return wk;
+  }
+
+  // Check for existing atom.
+  SpecificParserAtomLookup<CharT> lookup(seq);
+  EntrySet::AddPtr add = entrySet_.lookupForAdd(lookup);
+  if (add) {
+    return ParserAtomId(add->get());
+  }
+
+  // Compute the total length and the storage requirements.
+  bool wide = false;
+  uint32_t length = 0;
+  InflatedChar16Sequence<CharT> seqCopy = seq;
+  while (seqCopy.hasMore()) {
+    char16_t ch = seqCopy.next();
+    wide = wide || (ch > MAX_LATIN1_CHAR);
+    length += 1;
+  }
+
+  HashNumber hash = lookup.hash();
+  return wide ? internChar16Seq<char16_t>(cx, add, seq, length, hash)
+              : internChar16Seq<Latin1Char>(cx, add, seq, length, hash);
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internChar16(
+    JSContext* cx, const char16_t* char16Ptr, uint32_t length) {
+  InflatedChar16Sequence<char16_t> seq(char16Ptr, length);
+
+  return lookupOrInternChar16Seq(cx, seq);
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internAscii(
+    JSContext* cx, const char* asciiPtr, uint32_t length) {
+  const Latin1Char* latin1Ptr = reinterpret_cast<const Latin1Char*>(asciiPtr);
+  return internLatin1(cx, latin1Ptr, length);
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internLatin1(
+    JSContext* cx, const Latin1Char* latin1Ptr, uint32_t length) {
+  // ASCII strings are strict subsets of Latin1 strings, an so can be used
+  // in the same (const) ways.
+  InflatedChar16Sequence<Latin1Char> seq(latin1Ptr, length);
+
+  // Check against well-known.
+  ParserAtomId wk = wellKnownTable_.lookupChar16Seq(seq);
+  if (wk) {
+    return wk;
+  }
+
+  // Look up.
+  SpecificParserAtomLookup<Latin1Char> lookup(seq);
+  EntrySet::AddPtr add = entrySet_.lookupForAdd(lookup);
+  if (add) {
+    return ParserAtomId(add->get());
+  }
+
+  // Existing entry not found, heap-allocate a copy and add it to the table.
+  UniqueLatin1Chars copy = js::DuplicateString(cx, latin1Ptr, length);
+  if (!copy) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  ParserAtomEntry ent =
+      ParserAtomEntry::make(std::move(copy), length, lookup.hash());
+  return addEntry(cx, add, std::move(ent));
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internUtf8(
+    JSContext* cx, const mozilla::Utf8Unit* utf8Ptr, uint32_t length) {
+  // If source text is ASCII, then the length of the target char buffer
+  // is the same as the length of the UTF8 input.  Convert it to a Latin1
+  // encoded string on the heap.
+  UTF8Chars utf8(utf8Ptr, length);
+  if (FindSmallestEncoding(utf8) == JS::SmallestEncoding::ASCII) {
+    // As ascii strings are a subset of Latin1 strings, and each encoding
+    // unit is the same size, we can reliably cast this `Utf8Unit*`
+    // to a `Latin1Char*`.
+    const Latin1Char* latin1Ptr = reinterpret_cast<const Latin1Char*>(utf8Ptr);
+    return internLatin1(cx, latin1Ptr, length);
+  }
+
+  InflatedChar16Sequence<mozilla::Utf8Unit> seq(utf8Ptr, length);
+
+  // Otherwise, slowpath lookup/interning path that identifies the
+  // proper target encoding.
+  return lookupOrInternChar16Seq(cx, seq);
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::internJSAtom(JSContext* cx,
+                                                              JSAtom* atom) {
+  JS::AutoCheckCannotGC nogc;
+
+  auto result =
+      atom->hasLatin1Chars()
+          ? internLatin1(cx, atom->latin1Chars(nogc), atom->length())
+          : internChar16(cx, atom->twoByteChars(nogc), atom->length());
+  if (result.isErr()) {
+    return result;
+  }
+  ParserAtomId id = result.unwrap();
+  id.entry()->setAtom(atom);
+  return id;
+}
+
+static void FillChar16Buffer(char16_t* buf, const ParserAtomEntry* ent) {
+  if (ent->hasLatin1Chars()) {
+    std::copy(ent->latin1Chars(), ent->latin1Chars() + ent->length(), buf);
+  } else {
+    std::copy(ent->twoByteChars(), ent->twoByteChars() + ent->length(), buf);
+  }
+}
+
+JS::Result<ParserAtomId, OOM&> ParserAtomsTable::concatAtoms(
+    JSContext* cx, ParserAtomId prefix, ParserAtomId suffix) {
+  const ParserAtomEntry* prefixEntry = prefix.entry();
+  const ParserAtomEntry* suffixEntry = suffix.entry();
+
+  bool latin1 = prefixEntry->hasLatin1Chars() && suffixEntry->hasLatin1Chars();
+  size_t prefixLength = prefixEntry->length();
+  size_t suffixLength = suffixEntry->length();
+  size_t concatLength = prefixLength + suffixLength;
+
+  if (latin1) {
+    // Concatenate a latin1 string and add it to the table.
+    UniqueLatin1Chars copy(cx->pod_malloc<Latin1Char>(concatLength));
+    if (!copy) {
+      return RaiseParserAtomsOOMError(cx);
+    }
+    mozilla::PodCopy(copy.get(), prefixEntry->latin1Chars(), prefixLength);
+    mozilla::PodCopy(copy.get() + prefixLength, suffixEntry->latin1Chars(),
+                     suffixLength);
+
+    InflatedChar16Sequence<Latin1Char> seq(copy.get(), concatLength);
+
+    // Check against well-known.
+    ParserAtomId wk = wellKnownTable_.lookupChar16Seq(seq);
+    if (wk) {
+      return wk;
+    }
+
+    SpecificParserAtomLookup<Latin1Char> lookup(seq);
+    EntrySet::AddPtr add = entrySet_.lookupForAdd(lookup);
+    if (add) {
+      return ParserAtomId(add->get());
+    }
+
+    ParserAtomEntry ent =
+        ParserAtomEntry::make(std::move(copy), concatLength, lookup.hash());
+
+    return addEntry(cx, add, std::move(ent));
+  }
+
+  // Concatenate a char16 string and add it to the table.
+  UniqueTwoByteChars copy(cx->pod_malloc<char16_t>(concatLength));
+  if (!copy) {
+    return RaiseParserAtomsOOMError(cx);
+  }
+  FillChar16Buffer(copy.get(), prefixEntry);
+  FillChar16Buffer(copy.get() + prefixLength, suffixEntry);
+
+  InflatedChar16Sequence<char16_t> seq(copy.get(), concatLength);
+
+  // Check against well-known.
+  ParserAtomId wk = wellKnownTable_.lookupChar16Seq(seq);
+  if (wk) {
+    return wk;
+  }
+
+  SpecificParserAtomLookup<char16_t> lookup(seq);
+  EntrySet::AddPtr add = entrySet_.lookupForAdd(lookup);
+  if (add) {
+    return ParserAtomId(add->get());
+  }
+
+  ParserAtomEntry ent =
+      ParserAtomEntry::make(std::move(copy), concatLength, lookup.hash());
+
+  return addEntry(cx, add, std::move(ent));
+}
+
+template <typename CharT>
+ParserAtomId WellKnownParserAtoms::lookupChar16Seq(
+    InflatedChar16Sequence<CharT> seq) const {
+  SpecificParserAtomLookup<CharT> lookup(seq);
+  EntrySet::Ptr get = entrySet_.readonlyThreadsafeLookup(lookup);
+  if (get) {
+    return ParserAtomId(get->get());
+  }
+  return ParserAtomId::Invalid();
+}
+
+bool WellKnownParserAtoms::initSingle(JSContext* cx, ParserNameId* name,
+                                      const char* str) {
+  MOZ_ASSERT(name != nullptr);
+
+  unsigned int len = strlen(str);
+
+  MOZ_ASSERT(FindSmallestEncoding(UTF8Chars(str, len)) ==
+             JS::SmallestEncoding::ASCII);
+
+  UniqueLatin1Chars copy(cx->pod_malloc<Latin1Char>(len));
+  if (!copy) {
+    return false;
+  }
+  mozilla::PodCopy(copy.get(), reinterpret_cast<const Latin1Char*>(str), len);
+
+  InflatedChar16Sequence<Latin1Char> seq(copy.get(), len);
+  SpecificParserAtomLookup<Latin1Char> lookup(seq);
+
+  ParserAtomEntry ent =
+      ParserAtomEntry::make(std::move(copy), len, lookup.hash());
+
+  UniquePtr<ParserAtomEntry> uniqueEntry(
+      cx->new_<ParserAtomEntry>(std::move(ent)));
+  if (!uniqueEntry) {
+    return false;
+  }
+  ParserNameId nm(uniqueEntry.get());
+
+  if (!entrySet_.putNew(lookup, std::move(uniqueEntry))) {
+    return false;
+  }
+
+  *name = nm;
+  return true;
+}
+
+bool WellKnownParserAtoms::init(JSContext* cx) {
+#define COMMON_NAME_INIT(idpart, id, text) \
+  if (!initSingle(cx, &(id), text)) {      \
+    return false;                          \
+  }
+  FOR_EACH_COMMON_PROPERTYNAME(COMMON_NAME_INIT)
+#undef COMMON_NAME_INIT
+  return true;
+}
+
+} /* namespace frontend */
+} /* namespace js */
+
+bool JSRuntime::initializeParserAtoms(JSContext* cx) {
+#ifdef JS_PARSER_ATOMS
+  MOZ_ASSERT(!commonParserNames);
+
+  if (parentRuntime) {
+    commonParserNames = parentRuntime->commonParserNames;
+    return true;
+  }
+
+  UniquePtr<js::frontend::WellKnownParserAtoms> names(
+      js_new<js::frontend::WellKnownParserAtoms>(cx));
+  if (!names || !names->init(cx)) {
+    return false;
+  }
+
+  commonParserNames = names.release();
+#else
+  commonParserNames = nullptr;
+#endif  // JS_PARSER_ATOMS
+  return true;
+}
+
+void JSRuntime::finishParserAtoms() {
+#ifdef JS_PARSER_ATOMS
+  if (!parentRuntime) {
+    js_delete(commonParserNames.ref());
+  }
+#else
+  MOZ_ASSERT(!commonParserNames);
+#endif  // JS_PARSER_ATOMS
+}

js/src/frontend/ParserAtom.h

@@ -0,0 +1,360 @@
+/* -*- 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/HashFunctions.h"  // HashString
+#include "mozilla/Variant.h"        // mozilla::Variant
+
+#include "ds/LifoAlloc.h"  // LifoAlloc
+#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 {
+
+class ParserNameId;
+
+template <typename CharT>
+class SpecificParserAtomLookup;
+
+class ParserAtomsTable;
+
+mozilla::GenericErrorResult<OOM&> RaiseParserAtomsOOMError(JSContext* cx);
+
+/**
+ * A ParserAtomEntry is an in-parser representation of an interned atomic
+ * string.  It mostly mirrors the information carried by a JSAtom*.
+ *
+ * ParserAtomEntry structs are individually heap-allocated and own their
+ * heap-allocated contents.
+ */
+class ParserAtomEntry {
+  friend class ParserAtomsTable;
+
+ public:
+  // Owned characters, either 8-bit Latin1, or 16-bit Char16
+  mozilla::Variant<JS::UniqueLatin1Chars, JS::UniqueTwoByteChars> chars_;
+
+  // The length of the buffer in chars_.
+  uint32_t length_;
+
+  // The JSAtom-compatible hash of the string.
+  HashNumber hash_;
+
+  // Used to dynamically optimize the mapping of ParserAtoms to JSAtom*s.
+  // If the entry comes from an atom or has been mapped to an
+  // atom previously, the atom reference is kept here.
+  mutable JSAtom* jsatom_ = nullptr;
+
+  template <typename CharsT>
+  ParserAtomEntry(CharsT&& chars, uint32_t length, HashNumber hash)
+      : chars_(std::forward<CharsT&&>(chars)), length_(length), hash_(hash) {}
+
+ public:
+  // ParserAtomEntries own their content buffers in chars_, and thus cannot
+  // be copy-constructed - as a new chars would need to be allocated.
+  ParserAtomEntry(const ParserAtomEntry&) = delete;
+
+  ParserAtomEntry(ParserAtomEntry&& other) = default;
+
+  template <typename CharT>
+  static ParserAtomEntry make(mozilla::UniquePtr<CharT[], JS::FreePolicy>&& ptr,
+                              uint32_t length, HashNumber hash) {
+    return ParserAtomEntry(std::move(ptr), length, hash);
+  }
+
+  bool hasLatin1Chars() const { return chars_.is<UniqueLatin1Chars>(); }
+  bool hasTwoByteChars() const { return chars_.is<UniqueTwoByteChars>(); }
+
+  const Latin1Char* latin1Chars() const {
+    MOZ_ASSERT(hasLatin1Chars());
+    return chars_.as<UniqueLatin1Chars>().get();
+  }
+  const char16_t* twoByteChars() const {
+    MOZ_ASSERT(hasTwoByteChars());
+    return chars_.as<UniqueTwoByteChars>().get();
+  }
+
+  bool isIndex(uint32_t* indexp) const;
+
+  HashNumber hash() const { return hash_; }
+  uint32_t length() const { return length_; }
+
+  bool equalsJSAtom(JSAtom* other) const;
+
+  template <typename CharT>
+  bool equalsSeq(HashNumber hash, InflatedChar16Sequence<CharT> seq) const;
+
+  void setAtom(JSAtom* atom) const {
+    MOZ_ASSERT(atom != nullptr);
+    if (jsatom_ != nullptr) {
+      MOZ_ASSERT(jsatom_ == atom);
+      return;
+    }
+    MOZ_ASSERT(equalsJSAtom(atom));
+    jsatom_ = atom;
+  }
+
+  // Convert this entry to a js-atom.  The first time this method is called
+  // the entry will cache the JSAtom pointer to return later.
+  JS::Result<JSAtom*, OOM&> toJSAtom(JSContext* cx) const;
+
+  // Convert this entry to a number.
+  bool toNumber(JSContext* cx, double* result) const;
+};
+
+class ParserAtomId {
+ protected:
+  const ParserAtomEntry* entry_;
+
+  struct InitInvalid {};
+
+  explicit ParserAtomId(InitInvalid) : entry_(nullptr) {}
+
+ public:
+  explicit ParserAtomId(const ParserAtomEntry* entry) : entry_(entry) {
+    MOZ_ASSERT(entry_ != nullptr);
+  }
+  ParserAtomId() = default;
+
+  bool isValid() const { return entry_ != nullptr; }
+  const ParserAtomEntry* entry() const {
+    MOZ_ASSERT(isValid());
+    return entry_;
+  }
+  MOZ_IMPLICIT operator bool() const { return isValid(); }
+
+  static ParserAtomId Invalid() { return ParserAtomId(InitInvalid{}); }
+
+  // As the "unchecked" tag signifies, this method should only be called
+  // after it has been confirmed that this atom is a name and not an index.
+  inline ParserNameId toNameIdUnchecked() const;
+
+  bool operator==(const ParserAtomId& other) { return entry_ == other.entry_; }
+  bool operator!=(const ParserAtomId& other) { return !(*this == other); }
+
+  bool isIndex(uint32_t* indexp) const { return entry()->isIndex(indexp); }
+  bool equalsJSAtom(JSAtom* other) const {
+    return entry()->equalsJSAtom(other);
+  }
+
+  size_t length() const { return entry()->length(); }
+  size_t empty() const { return length() == 0; }
+
+  struct Hasher {
+    using Lookup = ParserAtomId;
+
+    static inline HashNumber hash(const Lookup& l) {
+      return DefaultHasher<const ParserAtomEntry*>::hash(l.entry());
+    }
+    static inline bool match(const ParserAtomId& entry,
+                             const ParserAtomId& lookup) {
+      return lookup == entry;
+    }
+  };
+};
+
+class ParserNameId : public ParserAtomId {
+  explicit ParserNameId(InitInvalid) : ParserAtomId(InitInvalid{}) {}
+
+ public:
+  ParserNameId() = default;
+  explicit ParserNameId(const ParserAtomEntry* entry) : ParserAtomId(entry) {}
+  ParserNameId(const ParserNameId& other) = default;
+
+  static ParserNameId Invalid() { return ParserNameId(InitInvalid{}); }
+};
+
+inline ParserNameId ParserAtomId::toNameIdUnchecked() const {
+  return ParserNameId(entry_);
+}
+
+UniqueChars ParserAtomToPrintableString(JSContext* cx, ParserAtomId atom);
+
+/**
+ * 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 UniquePtr<ParserAtomEntry>& entry,
+                           const Lookup& l) {
+    return l.equalsEntry(entry.get());
+  }
+};
+
+/**
+ * WellKnown maintains a well-structured reference to common names.
+ * A single instance of it is held on the main Runtime, and allows
+ * for the looking up of names, but not addition after initialization.
+ */
+class WellKnownParserAtoms {
+ public:
+  /* Various built-in or commonly-used names. */
+#define PROPERTYNAME_FIELD(idpart, id, text) ParserNameId id{};
+  FOR_EACH_COMMON_PROPERTYNAME(PROPERTYNAME_FIELD)
+#undef PROPERTYNAME_FIELD
+
+ private:
+  using EntrySet = HashSet<UniquePtr<ParserAtomEntry>, ParserAtomLookupHasher,
+                           TempAllocPolicy>;
+  EntrySet entrySet_;
+
+  bool initSingle(JSContext* cx, ParserNameId* name, const char* str);
+
+ public:
+  explicit WellKnownParserAtoms(JSContext* cx) : entrySet_(cx) {}
+
+  bool init(JSContext* cx);
+
+  template <typename CharT>
+  ParserAtomId lookupChar16Seq(InflatedChar16Sequence<CharT> seq) const;
+};
+
+/**
+ * A ParserAtomsTable owns and manages the vector of ParserAtom entries
+ * associated with a given compile session.
+ */
+class ParserAtomsTable {
+ private:
+  using EntrySet = HashSet<UniquePtr<ParserAtomEntry>, ParserAtomLookupHasher,
+                           TempAllocPolicy>;
+  EntrySet entrySet_;
+  const WellKnownParserAtoms& wellKnownTable_;
+
+ public:
+  explicit ParserAtomsTable(JSContext* cx);
+
+ private:
+  JS::Result<ParserAtomId, OOM&> addEntry(JSContext* cx,
+                                          EntrySet::AddPtr addPtr,
+                                          ParserAtomEntry&& entry);
+
+  template <typename AtomCharT, typename SeqCharT>
+  JS::Result<ParserAtomId, OOM&> internChar16Seq(
+      JSContext* cx, EntrySet::AddPtr add, InflatedChar16Sequence<SeqCharT> seq,
+      uint32_t length, HashNumber hash);
+
+  template <typename CharT>
+  JS::Result<ParserAtomId, OOM&> lookupOrInternChar16Seq(
+      JSContext* cx, InflatedChar16Sequence<CharT> seq);
+
+ public:
+  JS::Result<ParserAtomId, OOM&> internChar16(JSContext* cx,
+                                              const char16_t* char16Ptr,
+                                              uint32_t length);
+
+  JS::Result<ParserAtomId, OOM&> internAscii(JSContext* cx,
+                                             const char* asciiPtr,
+                                             uint32_t length);
+
+  JS::Result<ParserAtomId, OOM&> internLatin1(JSContext* cx,
+                                              const Latin1Char* latin1Ptr,
+                                              uint32_t length);
+
+  JS::Result<ParserAtomId, OOM&> internUtf8(JSContext* cx,
+                                            const mozilla::Utf8Unit* utf8Ptr,
+                                            uint32_t length);
+
+  JS::Result<ParserAtomId, OOM&> internJSAtom(JSContext* cx, JSAtom* atom);
+
+  JS::Result<ParserAtomId, OOM&> concatAtoms(JSContext* cx, ParserAtomId prefix,
+                                             ParserAtomId suffix);
+
+  // Lift this code
+  // Once all the parser code has been changed to use a ParserAtomId, these
+  // can go away.
+  JS::Result<JSAtom*, OOM&> toJSAtom(JSContext* cx, ParserAtomId id) const {
+    return id.entry()->toJSAtom(cx);
+  }
+};
+
+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, computeHash(seq)) {}
+
+  SpecificParserAtomLookup(const InflatedChar16Sequence<CharT>& seq,
+                           HashNumber hash)
+      : ParserAtomLookup(hash), seq_(seq) {
+    MOZ_ASSERT(computeHash(seq_) == hash);
+  }
+
+  virtual bool equalsEntry(const ParserAtomEntry* entry) const override {
+    return entry->equalsSeq<CharT>(hash_, seq_);
+  }
+
+ private:
+  static HashNumber computeHash(InflatedChar16Sequence<CharT> seq) {
+    HashNumber hash = 0;
+    while (seq.hasMore()) {
+      hash = mozilla::AddToHash(hash, seq.next());
+    }
+    return hash;
+  }
+};
+
+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;
+      }
+    }
+    if (seq.hasMore()) {
+      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;
+      }
+    }
+    if (seq.hasMore()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif  // frontend_ParserAtom_h

js/src/frontend/TokenStream.cpp

@@ -2231,7 +2231,7 @@ MOZ_MUST_USE bool TokenStreamSpecific<Unit, AnyCharsAccess>::identifierName(
       return false;
     }
 
-    atom = drainCharBufferIntoAtom(anyCharsAccess().cx);
+    atom = drainCharBufferIntoAtom();
   } else {
     // Escape-free identifiers can be created directly from sourceUnits.
     const Unit* chars = identStart;
@@ -2247,7 +2247,7 @@ MOZ_MUST_USE bool TokenStreamSpecific<Unit, AnyCharsAccess>::identifierName(
       }
     }
 
-    atom = atomizeSourceChars(anyCharsAccess().cx, MakeSpan(chars, length));
+    atom = atomizeSourceChars(MakeSpan(chars, length));
   }
   if (!atom) {
     return false;
@@ -3668,7 +3668,7 @@ bool TokenStreamSpecific<Unit, AnyCharsAccess>::getStringOrTemplateToken(
     }
   }
 
-  JSAtom* atom = drainCharBufferIntoAtom(anyCharsAccess().cx);
+  JSAtom* atom = drainCharBufferIntoAtom();
   if (!atom) {
     return false;
   }

js/src/frontend/TokenStream.h

@@ -1537,8 +1537,22 @@ class TokenStreamCharsShared {
     return mozilla::IsAscii(static_cast<char32_t>(unit));
   }
 
-  JSAtom* drainCharBufferIntoAtom(JSContext* cx) {
-    JSAtom* atom = AtomizeChars(cx, charBuffer.begin(), charBuffer.length());
+  JSAtom* drainCharBufferIntoAtom() {
+    JSAtom* atom = AtomizeChars(this->compilationInfo->cx, charBuffer.begin(),
+                                charBuffer.length());
+    if (!atom) {
+      return nullptr;
+    }
+
+    // Add to parser atoms table.
+#ifdef JS_PARSER_ATOMS
+    auto maybeId = this->compilationInfo->parserAtoms.internChar16(
+        this->compilationInfo->cx, charBuffer.begin(), charBuffer.length());
+    if (maybeId.isErr()) {
+      return nullptr;
+    }
+#endif  // JS_PARSER_ATOMS
+
     charBuffer.clear();
     return atom;
   }
@@ -1602,8 +1616,7 @@ class TokenStreamCharsBase : public TokenStreamCharsShared {
     sourceUnits.ungetCodeUnit();
   }
 
-  static MOZ_ALWAYS_INLINE JSAtom* atomizeSourceChars(
-      JSContext* cx, mozilla::Span<const Unit> units);
+  MOZ_ALWAYS_INLINE JSAtom* atomizeSourceChars(mozilla::Span<const Unit> units);
 
   /**
    * Try to match a non-LineTerminator ASCII code point.  Return true iff it
@@ -1689,18 +1702,45 @@ inline void TokenStreamCharsBase<Unit>::consumeKnownCodeUnit(int32_t unit) {
 }
 
 template <>
-/* static */ MOZ_ALWAYS_INLINE JSAtom*
-TokenStreamCharsBase<char16_t>::atomizeSourceChars(
-    JSContext* cx, mozilla::Span<const char16_t> units) {
-  return AtomizeChars(cx, units.data(), units.size());
+MOZ_ALWAYS_INLINE JSAtom* TokenStreamCharsBase<char16_t>::atomizeSourceChars(
+    mozilla::Span<const char16_t> units) {
+  JSAtom* atom =
+      AtomizeChars(this->compilationInfo->cx, units.data(), units.size());
+  if (!atom) {
+    return nullptr;
+  }
+
+#ifdef JS_PARSER_ATOMS
+  auto maybeId = this->compilationInfo->parserAtoms.internChar16(
+      this->compilationInfo->cx, units.data(), units.size());
+  if (maybeId.isErr()) {
+    return nullptr;
+  }
+#endif  // JS_PARSER_ATOMS
+
+  return atom;
 }
 
 template <>
 /* static */ MOZ_ALWAYS_INLINE JSAtom*
 TokenStreamCharsBase<mozilla::Utf8Unit>::atomizeSourceChars(
-    JSContext* cx, mozilla::Span<const mozilla::Utf8Unit> units) {
+    mozilla::Span<const mozilla::Utf8Unit> units) {
   auto chars = ToCharSpan(units);
-  return AtomizeUTF8Chars(cx, chars.data(), chars.size());
+  JSAtom* atom =
+      AtomizeUTF8Chars(this->compilationInfo->cx, chars.data(), chars.size());
+  if (!atom) {
+    return nullptr;
+  }
+
+#ifdef JS_PARSER_ATOMS
+  auto maybeId = this->compilationInfo->parserAtoms.internUtf8(
+      this->compilationInfo->cx, units.data(), units.size());
+  if (maybeId.isErr()) {
+    return nullptr;
+  }
+#endif  // JS_PARSER_ATOMS
+
+  return atom;
 }
 
 template <typename Unit>
@@ -2141,7 +2181,7 @@ class GeneralTokenStreamChars : public SpecializedTokenStreamCharsBase<Unit> {
       return nullptr;
     }
 
-    return drainCharBufferIntoAtom(anyChars.cx);
+    return drainCharBufferIntoAtom();
   }
 };
 

js/src/frontend/moz.build

@@ -58,6 +58,7 @@ UNIFIED_SOURCES += [
     'ParseContext.cpp',
     'ParseNode.cpp',
     'ParseNodeVerify.cpp',
+    'ParserAtom.cpp',
     'PropOpEmitter.cpp',
     'SharedContext.cpp',
     'SourceNotes.cpp',

js/src/jsapi.cpp

@@ -464,6 +464,10 @@ JS_PUBLIC_API bool JS::InitSelfHostedCode(JSContext* cx) {
     return false;
   }
 
+  if (!rt->initializeParserAtoms(cx)) {
+    return false;
+  }
+
 #ifndef JS_CODEGEN_NONE
   if (!rt->createJitRuntime(cx)) {
     return false;

js/src/jsnum.cpp

@@ -1661,7 +1661,7 @@ bool JS_FASTCALL js::NumberValueToStringBuffer(JSContext* cx, const Value& v,
 }
 
 template <typename CharT>
-static bool CharsToNumber(JSContext* cx, const CharT* chars, size_t length,
+static bool CharsToNumberImpl(JSContext* cx, const CharT* chars, size_t length,
                               double* result) {
   if (length == 1) {
     CharT c = chars[0];
@@ -1731,6 +1731,16 @@ static bool CharsToNumber(JSContext* cx, const CharT* chars, size_t length,
   return true;
 }
 
+bool js::CharsToNumber(JSContext* cx, const Latin1Char* chars, size_t length,
+                       double* result) {
+  return CharsToNumberImpl(cx, chars, length, result);
+}
+
+bool js::CharsToNumber(JSContext* cx, const char16_t* chars, size_t length,
+                       double* result) {
+  return CharsToNumberImpl(cx, chars, length, result);
+}
+
 bool js::StringToNumber(JSContext* cx, JSString* str, double* result) {
   AutoCheckCannotGC nogc;
   JSLinearString* linearStr = str->ensureLinear(cx);

js/src/jsnum.h

@@ -176,6 +176,11 @@ template <typename CharT>
 extern MOZ_MUST_USE bool GetDecimalNonInteger(JSContext* cx, const CharT* start,
                                               const CharT* end, double* dp);
 
+bool CharsToNumber(JSContext* cx, const Latin1Char* chars, size_t length,
+                   double* result);
+bool CharsToNumber(JSContext* cx, const char16_t* chars, size_t length,
+                   double* result);
+
 extern MOZ_MUST_USE bool StringToNumber(JSContext* cx, JSString* str,
                                         double* result);
 

js/src/util/Text.cpp

@@ -73,6 +73,19 @@ UniqueChars js::DuplicateStringToArena(arena_id_t destArenaId, JSContext* cx,
   return ret;
 }
 
+UniqueLatin1Chars js::DuplicateStringToArena(arena_id_t destArenaId,
+                                             JSContext* cx,
+                                             const JS::Latin1Char* s,
+                                             size_t n) {
+  auto ret = cx->make_pod_arena_array<Latin1Char>(destArenaId, n + 1);
+  if (!ret) {
+    return nullptr;
+  }
+  PodCopy(ret.get(), s, n);
+  ret[n] = '\0';
+  return ret;
+}
+
 UniqueTwoByteChars js::DuplicateStringToArena(arena_id_t destArenaId,
                                               JSContext* cx,
                                               const char16_t* s) {
@@ -106,6 +119,19 @@ UniqueChars js::DuplicateStringToArena(arena_id_t destArenaId, const char* s,
   return ret;
 }
 
+UniqueLatin1Chars js::DuplicateStringToArena(arena_id_t destArenaId,
+                                             const JS::Latin1Char* s,
+                                             size_t n) {
+  UniqueLatin1Chars ret(
+      js_pod_arena_malloc<JS::Latin1Char>(destArenaId, n + 1));
+  if (!ret) {
+    return nullptr;
+  }
+  PodCopy(ret.get(), s, n);
+  ret[n] = '\0';
+  return ret;
+}
+
 UniqueTwoByteChars js::DuplicateStringToArena(arena_id_t destArenaId,
                                               const char16_t* s) {
   return DuplicateStringToArena(destArenaId, s, js_strlen(s));
@@ -130,6 +156,11 @@ UniqueChars js::DuplicateString(JSContext* cx, const char* s) {
   return DuplicateStringToArena(js::MallocArena, cx, s);
 }
 
+UniqueLatin1Chars js::DuplicateString(JSContext* cx, const JS::Latin1Char* s,
+                                      size_t n) {
+  return DuplicateStringToArena(js::MallocArena, cx, s, n);
+}
+
 UniqueTwoByteChars js::DuplicateString(JSContext* cx, const char16_t* s) {
   return DuplicateStringToArena(js::MallocArena, cx, s);
 }
@@ -147,6 +178,10 @@ UniqueChars js::DuplicateString(const char* s, size_t n) {
   return DuplicateStringToArena(js::MallocArena, s, n);
 }
 
+UniqueLatin1Chars js::DuplicateString(const JS::Latin1Char* s, size_t n) {
+  return DuplicateStringToArena(js::MallocArena, s, n);
+}
+
 UniqueTwoByteChars js::DuplicateString(const char16_t* s) {
   return DuplicateStringToArena(js::MallocArena, s);
 }

js/src/util/Text.h

@@ -108,6 +108,10 @@ extern UniqueChars DuplicateStringToArena(arena_id_t destArenaId, JSContext* cx,
 extern UniqueChars DuplicateStringToArena(arena_id_t destArenaId, JSContext* cx,
                                           const char* s, size_t n);
 
+extern UniqueLatin1Chars DuplicateStringToArena(arena_id_t destArenaId,
+                                                JSContext* cx,
+                                                const Latin1Char* s, size_t n);
+
 extern UniqueTwoByteChars DuplicateStringToArena(arena_id_t destArenaId,
                                                  JSContext* cx,
                                                  const char16_t* s);
@@ -126,6 +130,10 @@ extern UniqueChars DuplicateStringToArena(arena_id_t destArenaId,
 extern UniqueChars DuplicateStringToArena(arena_id_t destArenaId, const char* s,
                                           size_t n);
 
+extern UniqueLatin1Chars DuplicateStringToArena(arena_id_t destArenaId,
+                                                const JS::Latin1Char* s,
+                                                size_t n);
+
 extern UniqueTwoByteChars DuplicateStringToArena(arena_id_t destArenaId,
                                                  const char16_t* s);
 
@@ -136,6 +144,9 @@ extern UniqueChars DuplicateString(JSContext* cx, const char* s);
 
 extern UniqueChars DuplicateString(JSContext* cx, const char* s, size_t n);
 
+extern UniqueLatin1Chars DuplicateString(JSContext* cx, const JS::Latin1Char* s,
+                                         size_t n);
+
 extern UniqueTwoByteChars DuplicateString(JSContext* cx, const char16_t* s);
 
 extern UniqueTwoByteChars DuplicateString(JSContext* cx, const char16_t* s,
@@ -149,6 +160,8 @@ extern UniqueChars DuplicateString(const char* s);
 
 extern UniqueChars DuplicateString(const char* s, size_t n);
 
+extern UniqueLatin1Chars DuplicateString(const JS::Latin1Char* s, size_t n);
+
 extern UniqueTwoByteChars DuplicateString(const char16_t* s);
 
 extern UniqueTwoByteChars DuplicateString(const char16_t* s, size_t n);

js/src/vm/JSContext.h

@@ -40,6 +40,10 @@ class AutoAllocInAtomsZone;
 class AutoMaybeLeaveAtomsZone;
 class AutoRealm;
 
+namespace frontend {
+class WellKnownParserAtoms;
+}  // namespace frontend
+
 namespace jit {
 class JitActivation;
 class JitContext;
@@ -265,6 +269,9 @@ struct JS_PUBLIC_API JSContext : public JS::RootingContext,
 
   // Accessors for immutable runtime data.
   JSAtomState& names() { return *runtime_->commonNames; }
+  js::frontend::WellKnownParserAtoms& parserNames() {
+    return *runtime_->commonParserNames;
+  }
   js::StaticStrings& staticStrings() { return *runtime_->staticStrings; }
   js::SharedImmutableStringsCache& sharedImmutableStrings() {
     return runtime_->sharedImmutableStrings();

js/src/vm/Runtime.h

@@ -109,6 +109,10 @@ class Simulator;
 #endif
 }  // namespace jit
 
+namespace frontend {
+class WellKnownParserAtoms;
+}  // namespace frontend
+
 // [SMDOC] JS Engine Threading
 //
 // Threads interacting with a runtime are divided into two categories:
@@ -742,7 +746,9 @@ struct JSRuntime {
 
  public:
   bool initializeAtoms(JSContext* cx);
+  bool initializeParserAtoms(JSContext* cx);
   void finishAtoms();
+  void finishParserAtoms();
   bool atomsAreFinished() const {
     return !atoms_ && !permanentAtomsDuringInit_;
   }
@@ -783,6 +789,7 @@ struct JSRuntime {
 
   // Cached pointers to various permanent property names.
   js::WriteOnceData<JSAtomState*> commonNames;
+  js::WriteOnceData<js::frontend::WellKnownParserAtoms*> commonParserNames;
 
   // All permanent atoms in the runtime, other than those in staticStrings.
   // Access to this does not require a lock because it is frozen and thus

js/src/vm/StringType.cpp

@@ -1152,9 +1152,7 @@ bool js::StringEqualsAscii(JSLinearString* str, const char* asciiBytes,
 }
 
 template <typename CharT>
-/* static */
-bool JSLinearString::isIndexSlow(const CharT* s, size_t length,
-                                 uint32_t* indexp) {
+bool js::CheckStringIsIndex(const CharT* s, size_t length, uint32_t* indexp) {
   MOZ_ASSERT(length > 0);
   MOZ_ASSERT(length <= UINT32_CHAR_BUFFER_LENGTH);
   MOZ_ASSERT(IsAsciiDigit(*s),
@@ -1194,6 +1192,18 @@ bool JSLinearString::isIndexSlow(const CharT* s, size_t length,
   return false;
 }
 
+template bool js::CheckStringIsIndex(const Latin1Char* s, size_t length,
+                                     uint32_t* indexp);
+template bool js::CheckStringIsIndex(const char16_t* s, size_t length,
+                                     uint32_t* indexp);
+
+template <typename CharT>
+/* static */
+bool JSLinearString::isIndexSlow(const CharT* s, size_t length,
+                                 uint32_t* indexp) {
+  return js::CheckStringIsIndex(s, length, indexp);
+}
+
 template bool JSLinearString::isIndexSlow(const Latin1Char* s, size_t length,
                                           uint32_t* indexp);
 

js/src/vm/StringType.h

@@ -1259,6 +1259,9 @@ MOZ_ALWAYS_INLINE JSAtom* JSLinearString::morphAtomizedStringIntoPermanentAtom(
 
 namespace js {
 
+template <typename CharT>
+bool CheckStringIsIndex(const CharT* s, size_t length, uint32_t* indexp);
+
 /**
  * An indexable characters class exposing unaligned, little-endian encoded
  * char16_t data.