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diff --git a/js/src/vm/RegExpShared.h b/js/src/vm/RegExpShared.h
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+/* -*- 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/. */
+
+/**
+ * The compiled representation of a RegExp, potentially shared among RegExp
+ * instances created during separate evaluations of a single RegExp literal in
+ * source code.
+ */
+
+#ifndef vm_RegExpShared_h
+#define vm_RegExpShared_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/MemoryReporting.h"
+
+#include "gc/Barrier.h"
+#include "gc/Policy.h"
+#include "gc/ZoneAllocator.h"
+#include "irregexp/RegExpTypes.h"
+#include "jit/JitCode.h"
+#include "jit/JitOptions.h"
+#include "js/AllocPolicy.h"
+#include "js/RegExpFlags.h"  // JS::RegExpFlag, JS::RegExpFlags
+#include "js/UbiNode.h"
+#include "js/Vector.h"
+#include "vm/ArrayObject.h"
+
+namespace js {
+
+class ArrayObject;
+class PlainObject;
+class RegExpRealm;
+class RegExpShared;
+class RegExpStatics;
+class VectorMatchPairs;
+
+using RootedRegExpShared = JS::Rooted<RegExpShared*>;
+using HandleRegExpShared = JS::Handle<RegExpShared*>;
+using MutableHandleRegExpShared = JS::MutableHandle<RegExpShared*>;
+
+enum RegExpRunStatus : int32_t {
+  RegExpRunStatus_Error = -1,
+  RegExpRunStatus_Success = 1,
+  RegExpRunStatus_Success_NotFound = 0,
+};
+
+inline bool IsNativeRegExpEnabled() {
+  return jit::HasJitBackend() && jit::JitOptions.nativeRegExp;
+}
+
+/*
+ * A RegExpShared is the compiled representation of a regexp. A RegExpShared is
+ * potentially pointed to by multiple RegExpObjects. Additionally, C++ code may
+ * have pointers to RegExpShareds on the stack. The RegExpShareds are kept in a
+ * table so that they can be reused when compiling the same regex string.
+ *
+ * To save memory, a RegExpShared is not created for a RegExpObject until it is
+ * needed for execution. When a RegExpShared needs to be created, it is looked
+ * up in a per-compartment table to allow reuse between objects.
+ *
+ * During a GC, RegExpShared instances are marked and swept like GC things.
+ * Usually, RegExpObjects clear their pointers to their RegExpShareds rather
+ * than explicitly tracing them, so that the RegExpShared and any jitcode can
+ * be reclaimed quicker. However, the RegExpShareds are traced through by
+ * objects when we are preserving jitcode in their zone, to avoid the same
+ * recompilation inefficiencies as normal Ion and baseline compilation.
+ */
+class RegExpShared
+    : public gc::CellWithTenuredGCPointer<gc::TenuredCell, JSAtom> {
+  friend class js::gc::CellAllocator;
+
+ public:
+  enum class Kind { Unparsed, Atom, RegExp };
+  enum class CodeKind { Bytecode, Jitcode, Any };
+
+  using ByteCode = js::irregexp::ByteArrayData;
+  using JitCodeTable = js::irregexp::ByteArray;
+  using JitCodeTables = Vector<JitCodeTable, 0, SystemAllocPolicy>;
+
+ private:
+  friend class RegExpStatics;
+  friend class RegExpZone;
+
+  struct RegExpCompilation {
+    HeapPtr<jit::JitCode*> jitCode;
+    ByteCode* byteCode = nullptr;
+
+    bool compiled(CodeKind kind = CodeKind::Any) const {
+      switch (kind) {
+        case CodeKind::Bytecode:
+          return !!byteCode;
+        case CodeKind::Jitcode:
+          return !!jitCode;
+        case CodeKind::Any:
+          return !!byteCode || !!jitCode;
+      }
+      MOZ_CRASH("Unreachable");
+    }
+
+    size_t byteCodeLength() const {
+      MOZ_ASSERT(byteCode);
+      return byteCode->length;
+    }
+  };
+
+ public:
+  /* Source to the RegExp, for lazy compilation. Stored in the cell header. */
+  JSAtom* getSource() const { return headerPtr(); }
+
+ private:
+  RegExpCompilation compilationArray[2];
+
+  uint32_t pairCount_;
+  JS::RegExpFlags flags;
+
+  RegExpShared::Kind kind_ = Kind::Unparsed;
+  GCPtr<JSAtom*> patternAtom_;
+  uint32_t maxRegisters_ = 0;
+  uint32_t ticks_ = 0;
+
+  uint32_t numNamedCaptures_ = {};
+  uint32_t* namedCaptureIndices_ = {};
+  GCPtr<PlainObject*> groupsTemplate_ = {};
+
+  static int CompilationIndex(bool latin1) { return latin1 ? 0 : 1; }
+
+  // Tables referenced by JIT code.
+  JitCodeTables tables;
+
+  /* Internal functions. */
+  RegExpShared(JSAtom* source, JS::RegExpFlags flags);
+
+  const RegExpCompilation& compilation(bool latin1) const {
+    return compilationArray[CompilationIndex(latin1)];
+  }
+
+  RegExpCompilation& compilation(bool latin1) {
+    return compilationArray[CompilationIndex(latin1)];
+  }
+
+ public:
+  ~RegExpShared() = delete;
+
+  static bool compileIfNecessary(JSContext* cx, MutableHandleRegExpShared res,
+                                 Handle<JSLinearString*> input, CodeKind code);
+
+  static RegExpRunStatus executeAtom(MutableHandleRegExpShared re,
+                                     Handle<JSLinearString*> input,
+                                     size_t start, VectorMatchPairs* matches);
+
+  // Execute this RegExp on input starting from searchIndex, filling in matches.
+  static RegExpRunStatus execute(JSContext* cx, MutableHandleRegExpShared res,
+                                 Handle<JSLinearString*> input,
+                                 size_t searchIndex, VectorMatchPairs* matches);
+
+  // Register a table with this RegExpShared, and take ownership.
+  bool addTable(JitCodeTable table) { return tables.append(std::move(table)); }
+
+  /* Accessors */
+
+  size_t pairCount() const {
+    MOZ_ASSERT(kind() != Kind::Unparsed);
+    return pairCount_;
+  }
+
+  RegExpShared::Kind kind() const { return kind_; }
+
+  // Use simple string matching for this regexp.
+  void useAtomMatch(Handle<JSAtom*> pattern);
+
+  // Use the regular expression engine for this regexp.
+  void useRegExpMatch(size_t parenCount);
+
+  static void InitializeNamedCaptures(JSContext* cx, HandleRegExpShared re,
+                                      uint32_t numNamedCaptures,
+                                      Handle<PlainObject*> templateObject,
+                                      uint32_t* captureIndices);
+  PlainObject* getGroupsTemplate() { return groupsTemplate_; }
+
+  void tierUpTick();
+  bool markedForTierUp() const;
+
+  void setByteCode(ByteCode* code, bool latin1) {
+    compilation(latin1).byteCode = code;
+  }
+  ByteCode* getByteCode(bool latin1) const {
+    return compilation(latin1).byteCode;
+  }
+  void setJitCode(jit::JitCode* code, bool latin1) {
+    compilation(latin1).jitCode = code;
+  }
+  jit::JitCode* getJitCode(bool latin1) const {
+    return compilation(latin1).jitCode;
+  }
+  uint32_t getMaxRegisters() const { return maxRegisters_; }
+  void updateMaxRegisters(uint32_t numRegisters) {
+    maxRegisters_ = std::max(maxRegisters_, numRegisters);
+  }
+
+  uint32_t numNamedCaptures() const { return numNamedCaptures_; }
+  int32_t getNamedCaptureIndex(uint32_t idx) const {
+    MOZ_ASSERT(idx < numNamedCaptures());
+    MOZ_ASSERT(namedCaptureIndices_);
+    return namedCaptureIndices_[idx];
+  }
+
+  JSAtom* patternAtom() const { return patternAtom_; }
+
+  JS::RegExpFlags getFlags() const { return flags; }
+
+  bool hasIndices() const { return flags.hasIndices(); }
+  bool global() const { return flags.global(); }
+  bool ignoreCase() const { return flags.ignoreCase(); }
+  bool multiline() const { return flags.multiline(); }
+  bool dotAll() const { return flags.dotAll(); }
+  bool unicode() const { return flags.unicode(); }
+  bool sticky() const { return flags.sticky(); }
+
+  bool isCompiled(bool latin1, CodeKind codeKind = CodeKind::Any) const {
+    return compilation(latin1).compiled(codeKind);
+  }
+  bool isCompiled() const { return isCompiled(true) || isCompiled(false); }
+
+  void traceChildren(JSTracer* trc);
+  void discardJitCode();
+  void finalize(JS::GCContext* gcx);
+
+  static size_t offsetOfSource() { return offsetOfHeaderPtr(); }
+
+  static size_t offsetOfPatternAtom() {
+    return offsetof(RegExpShared, patternAtom_);
+  }
+
+  static size_t offsetOfFlags() { return offsetof(RegExpShared, flags); }
+
+  static size_t offsetOfPairCount() {
+    return offsetof(RegExpShared, pairCount_);
+  }
+
+  static size_t offsetOfJitCode(bool latin1) {
+    return offsetof(RegExpShared, compilationArray) +
+           (CompilationIndex(latin1) * sizeof(RegExpCompilation)) +
+           offsetof(RegExpCompilation, jitCode);
+  }
+
+  static size_t offsetOfGroupsTemplate() {
+    return offsetof(RegExpShared, groupsTemplate_);
+  }
+
+  size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf);
+
+#ifdef DEBUG
+  static bool dumpBytecode(JSContext* cx, MutableHandleRegExpShared res,
+                           Handle<JSLinearString*> input);
+#endif
+
+ public:
+  static const JS::TraceKind TraceKind = JS::TraceKind::RegExpShared;
+};
+
+class RegExpZone {
+  struct Key {
+    JSAtom* atom = nullptr;
+    JS::RegExpFlags flags = JS::RegExpFlag::NoFlags;
+
+    Key() = default;
+    Key(JSAtom* atom, JS::RegExpFlags flags) : atom(atom), flags(flags) {}
+    MOZ_IMPLICIT Key(const WeakHeapPtr<RegExpShared*>& shared)
+        : atom(shared.unbarrieredGet()->getSource()),
+          flags(shared.unbarrieredGet()->getFlags()) {}
+
+    using Lookup = Key;
+    static HashNumber hash(const Lookup& l) {
+      HashNumber hash = DefaultHasher<JSAtom*>::hash(l.atom);
+      return mozilla::AddToHash(hash, l.flags.value());
+    }
+    static bool match(Key l, Key r) {
+      return l.atom == r.atom && l.flags == r.flags;
+    }
+  };
+
+  /*
+   * The set of all RegExpShareds in the zone. On every GC, every RegExpShared
+   * that was not marked is deleted and removed from the set.
+   */
+  using Set = JS::WeakCache<
+      JS::GCHashSet<WeakHeapPtr<RegExpShared*>, Key, ZoneAllocPolicy>>;
+  Set set_;
+
+ public:
+  explicit RegExpZone(Zone* zone);
+
+  ~RegExpZone() { MOZ_ASSERT(set_.empty()); }
+
+  bool empty() const { return set_.empty(); }
+
+  RegExpShared* maybeGet(JSAtom* source, JS::RegExpFlags flags) const {
+    Set::Ptr p = set_.lookup(Key(source, flags));
+    return p ? *p : nullptr;
+  }
+
+  RegExpShared* get(JSContext* cx, Handle<JSAtom*> source,
+                    JS::RegExpFlags flags);
+
+#ifdef DEBUG
+  void clear() { set_.clear(); }
+#endif
+
+  size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
+};
+
+class RegExpRealm {
+ public:
+  enum ResultTemplateKind { Normal, WithIndices, Indices, NumKinds };
+
+ private:
+  /*
+   * The template objects that the result of re.exec() is based on, if
+   * there is a result. These are used in CreateRegExpMatchResult.
+   * There are three template objects, each of which is an ArrayObject
+   * with some additional properties. We decide which to use based on
+   * the |hasIndices| (/d) flag.
+   *
+   *  Normal: Has |index|, |input|, and |groups| properties.
+   *          Used for the result object if |hasIndices| is not set.
+   *
+   *  WithIndices: Has |index|, |input|, |groups|, and |indices| properties.
+   *               Used for the result object if |hasIndices| is set.
+   *
+   *  Indices: Has a |groups| property. If |hasIndices| is set, used
+   *           for the |.indices| property of the result object.
+   */
+  WeakHeapPtr<ArrayObject*>
+      matchResultTemplateObjects_[ResultTemplateKind::NumKinds];
+
+  /*
+   * The shape of RegExp.prototype object that satisfies following:
+   *   * RegExp.prototype.flags getter is not modified
+   *   * RegExp.prototype.global getter is not modified
+   *   * RegExp.prototype.ignoreCase getter is not modified
+   *   * RegExp.prototype.multiline getter is not modified
+   *   * RegExp.prototype.dotAll getter is not modified
+   *   * RegExp.prototype.sticky getter is not modified
+   *   * RegExp.prototype.unicode getter is not modified
+   *   * RegExp.prototype.exec is an own data property
+   *   * RegExp.prototype[@@match] is an own data property
+   *   * RegExp.prototype[@@search] is an own data property
+   */
+  WeakHeapPtr<Shape*> optimizableRegExpPrototypeShape_;
+
+  /*
+   * The shape of RegExp instance that satisfies following:
+   *   * lastProperty is lastIndex
+   *   * prototype is RegExp.prototype
+   */
+  WeakHeapPtr<Shape*> optimizableRegExpInstanceShape_;
+
+  ArrayObject* createMatchResultTemplateObject(JSContext* cx,
+                                               ResultTemplateKind kind);
+
+ public:
+  explicit RegExpRealm();
+
+  void traceWeak(JSTracer* trc);
+
+  static const size_t MatchResultObjectIndexSlot = 0;
+  static const size_t MatchResultObjectInputSlot = 1;
+  static const size_t MatchResultObjectGroupsSlot = 2;
+  static const size_t MatchResultObjectIndicesSlot = 3;
+
+  static const size_t IndicesGroupsSlot = 0;
+
+  static size_t offsetOfMatchResultObjectIndexSlot() {
+    return sizeof(Value) * MatchResultObjectIndexSlot;
+  }
+  static size_t offsetOfMatchResultObjectInputSlot() {
+    return sizeof(Value) * MatchResultObjectInputSlot;
+  }
+  static size_t offsetOfMatchResultObjectGroupsSlot() {
+    return sizeof(Value) * MatchResultObjectGroupsSlot;
+  }
+  static size_t offsetOfMatchResultObjectIndicesSlot() {
+    return sizeof(Value) * MatchResultObjectIndicesSlot;
+  }
+
+  /* Get or create template object used to base the result of .exec() on. */
+  ArrayObject* getOrCreateMatchResultTemplateObject(
+      JSContext* cx, ResultTemplateKind kind = ResultTemplateKind::Normal) {
+    if (matchResultTemplateObjects_[kind]) {
+      return matchResultTemplateObjects_[kind];
+    }
+    return createMatchResultTemplateObject(cx, kind);
+  }
+
+  Shape* getOptimizableRegExpPrototypeShape() {
+    return optimizableRegExpPrototypeShape_;
+  }
+  void setOptimizableRegExpPrototypeShape(Shape* shape) {
+    optimizableRegExpPrototypeShape_ = shape;
+  }
+  Shape* getOptimizableRegExpInstanceShape() {
+    return optimizableRegExpInstanceShape_;
+  }
+  void setOptimizableRegExpInstanceShape(Shape* shape) {
+    optimizableRegExpInstanceShape_ = shape;
+  }
+
+  static size_t offsetOfOptimizableRegExpPrototypeShape() {
+    return offsetof(RegExpRealm, optimizableRegExpPrototypeShape_);
+  }
+  static size_t offsetOfOptimizableRegExpInstanceShape() {
+    return offsetof(RegExpRealm, optimizableRegExpInstanceShape_);
+  }
+};
+
+RegExpRunStatus ExecuteRegExpAtomRaw(RegExpShared* re, JSLinearString* input,
+                                     size_t start, MatchPairs* matchPairs);
+
+} /* namespace js */
+
+namespace JS {
+namespace ubi {
+
+template <>
+class Concrete<js::RegExpShared> : TracerConcrete<js::RegExpShared> {
+ protected:
+  explicit Concrete(js::RegExpShared* ptr)
+      : TracerConcrete<js::RegExpShared>(ptr) {}
+
+ public:
+  static void construct(void* storage, js::RegExpShared* ptr) {
+    new (storage) Concrete(ptr);
+  }
+
+  CoarseType coarseType() const final { return CoarseType::Other; }
+
+  Size size(mozilla::MallocSizeOf mallocSizeOf) const override;
+
+  const char16_t* typeName() const override { return concreteTypeName; }
+  static const char16_t concreteTypeName[];
+};
+
+}  // namespace ubi
+}  // namespace JS
+
+#endif /* vm_RegExpShared_h */