path: root/js/src/wasm/WasmCode.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 *
 * Copyright 2016 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef wasm_code_h
#define wasm_code_h

#include "gc/Memory.h"
#include "jit/JitOptions.h"
#include "jit/shared/Assembler-shared.h"
#include "js/HashTable.h"
#include "threading/ExclusiveData.h"
#include "util/Memory.h"
#include "vm/MutexIDs.h"
#include "wasm/WasmGC.h"
#include "wasm/WasmTypes.h"

namespace js {

struct AsmJSMetadata;

namespace wasm {

struct MetadataTier;
struct Metadata;

// LinkData contains all the metadata necessary to patch all the locations
// that depend on the absolute address of a ModuleSegment. This happens in a
// "linking" step after compilation and after the module's code is serialized.
// The LinkData is serialized along with the Module but does not (normally, see
// Module::debugLinkData_ comment) persist after (de)serialization, which
// distinguishes it from Metadata, which is stored in the Code object.

struct LinkDataCacheablePod {
  uint32_t trapOffset = 0;

  LinkDataCacheablePod() = default;
};

struct LinkData : LinkDataCacheablePod {
  const Tier tier;

  explicit LinkData(Tier tier) : tier(tier) {}

  LinkDataCacheablePod& pod() { return *this; }
  const LinkDataCacheablePod& pod() const { return *this; }

  struct InternalLink {
    uint32_t patchAtOffset;
    uint32_t targetOffset;
#ifdef JS_CODELABEL_LINKMODE
    uint32_t mode;
#endif
  };
  typedef Vector<InternalLink, 0, SystemAllocPolicy> InternalLinkVector;

  struct SymbolicLinkArray
      : EnumeratedArray<SymbolicAddress, SymbolicAddress::Limit, Uint32Vector> {
    WASM_DECLARE_SERIALIZABLE(SymbolicLinkArray)
  };

  InternalLinkVector internalLinks;
  SymbolicLinkArray symbolicLinks;

  WASM_DECLARE_SERIALIZABLE(LinkData)
};

using UniqueLinkData = UniquePtr<LinkData>;

// Executable code must be deallocated specially.

struct FreeCode {
  uint32_t codeLength;
  FreeCode() : codeLength(0) {}
  explicit FreeCode(uint32_t codeLength) : codeLength(codeLength) {}
  void operator()(uint8_t* codeBytes);
};

using UniqueCodeBytes = UniquePtr<uint8_t, FreeCode>;

class Code;
class CodeTier;
class ModuleSegment;
class LazyStubSegment;

// CodeSegment contains common helpers for determining the base and length of a
// code segment and if a pc belongs to this segment. It is inherited by:
// - ModuleSegment, i.e. the code segment of a Module, generated
// eagerly when a Module is instanciated.
// - LazyStubSegment, i.e. the code segment of entry stubs that are lazily
// generated.

class CodeSegment {
 protected:
  static UniqueCodeBytes AllocateCodeBytes(uint32_t codeLength);

  enum class Kind { LazyStubs, Module };

  CodeSegment(UniqueCodeBytes bytes, uint32_t length, Kind kind)
      : bytes_(std::move(bytes)),
        length_(length),
        kind_(kind),
        codeTier_(nullptr),
        unregisterOnDestroy_(false) {}

  bool initialize(const CodeTier& codeTier);

 private:
  const UniqueCodeBytes bytes_;
  const uint32_t length_;
  const Kind kind_;
  const CodeTier* codeTier_;
  bool unregisterOnDestroy_;

 public:
  bool initialized() const { return !!codeTier_; }
  ~CodeSegment();

  bool isLazyStubs() const { return kind_ == Kind::LazyStubs; }
  bool isModule() const { return kind_ == Kind::Module; }
  const ModuleSegment* asModule() const {
    MOZ_ASSERT(isModule());
    return (ModuleSegment*)this;
  }
  const LazyStubSegment* asLazyStub() const {
    MOZ_ASSERT(isLazyStubs());
    return (LazyStubSegment*)this;
  }

  uint8_t* base() const { return bytes_.get(); }
  uint32_t length() const {
    MOZ_ASSERT(length_ != UINT32_MAX);
    return length_;
  }

  bool containsCodePC(const void* pc) const {
    return pc >= base() && pc < (base() + length_);
  }

  const CodeTier& codeTier() const {
    MOZ_ASSERT(initialized());
    return *codeTier_;
  }
  const Code& code() const;

  void addSizeOfMisc(MallocSizeOf mallocSizeOf, size_t* code) const;
};

// A wasm ModuleSegment owns the allocated executable code for a wasm module.

using UniqueModuleSegment = UniquePtr<ModuleSegment>;

enum IsTier2 { Tier2, NotTier2 };

class ModuleSegment : public CodeSegment {
  const Tier tier_;
  uint8_t* const trapCode_;

 public:
  ModuleSegment(Tier tier, UniqueCodeBytes codeBytes, uint32_t codeLength,
                const LinkData& linkData);

  static UniqueModuleSegment create(Tier tier, jit::MacroAssembler& masm,
                                    const LinkData& linkData);
  static UniqueModuleSegment create(Tier tier, const Bytes& unlinkedBytes,
                                    const LinkData& linkData);

  bool initialize(IsTier2 compileMode, const CodeTier& codeTier,
                  const LinkData& linkData, const Metadata& metadata,
                  const MetadataTier& metadataTier);

  Tier tier() const { return tier_; }

  // Pointers to stubs to which PC is redirected from the signal-handler.

  uint8_t* trapCode() const { return trapCode_; }

  // Structured clone support:

  size_t serializedSize() const;
  uint8_t* serialize(uint8_t* cursor, const LinkData& linkData) const;
  static const uint8_t* deserialize(const uint8_t* cursor,
                                    const LinkData& linkData,
                                    UniqueModuleSegment* segment);

  const CodeRange* lookupRange(const void* pc) const;

  void addSizeOfMisc(mozilla::MallocSizeOf mallocSizeOf, size_t* code,
                     size_t* data) const;
};

// A FuncExport represents a single function definition inside a wasm Module
// that has been exported one or more times. A FuncExport represents an
// internal entry point that can be called via function definition index by
// Instance::callExport(). To allow O(log(n)) lookup of a FuncExport by
// function definition index, the FuncExportVector is stored sorted by
// function definition index.

class FuncExport {
  FuncType funcType_;
  MOZ_INIT_OUTSIDE_CTOR struct CacheablePod {
    uint32_t funcIndex_;
    uint32_t eagerInterpEntryOffset_;  // Machine code offset
    bool hasEagerStubs_;
  } pod;

 public:
  FuncExport() = default;
  explicit FuncExport(FuncType&& funcType, uint32_t funcIndex,
                      bool hasEagerStubs)
      : funcType_(std::move(funcType)) {
    pod.funcIndex_ = funcIndex;
    pod.eagerInterpEntryOffset_ = UINT32_MAX;
    pod.hasEagerStubs_ = hasEagerStubs;
  }
  void initEagerInterpEntryOffset(uint32_t entryOffset) {
    MOZ_ASSERT(pod.eagerInterpEntryOffset_ == UINT32_MAX);
    MOZ_ASSERT(hasEagerStubs());
    pod.eagerInterpEntryOffset_ = entryOffset;
  }

  bool hasEagerStubs() const { return pod.hasEagerStubs_; }
  const FuncType& funcType() const { return funcType_; }
  uint32_t funcIndex() const { return pod.funcIndex_; }
  uint32_t eagerInterpEntryOffset() const {
    MOZ_ASSERT(pod.eagerInterpEntryOffset_ != UINT32_MAX);
    MOZ_ASSERT(hasEagerStubs());
    return pod.eagerInterpEntryOffset_;
  }

  bool canHaveJitEntry() const {
    return !funcType_.hasUnexposableArgOrRet() &&
           !funcType_.temporarilyUnsupportedReftypeForEntry() &&
           !funcType_.temporarilyUnsupportedResultCountForJitEntry() &&
           JitOptions.enableWasmJitEntry;
  }

  bool clone(const FuncExport& src) {
    mozilla::PodAssign(&pod, &src.pod);
    return funcType_.clone(src.funcType_);
  }

  WASM_DECLARE_SERIALIZABLE(FuncExport)
};

typedef Vector<FuncExport, 0, SystemAllocPolicy> FuncExportVector;

// An FuncImport contains the runtime metadata needed to implement a call to an
// imported function. Each function import has two call stubs: an optimized path
// into JIT code and a slow path into the generic C++ js::Invoke and these
// offsets of these stubs are stored so that function-import callsites can be
// dynamically patched at runtime.

class FuncImport {
  FuncType funcType_;
  struct CacheablePod {
    uint32_t tlsDataOffset_;
    uint32_t interpExitCodeOffset_;  // Machine code offset
    uint32_t jitExitCodeOffset_;     // Machine code offset
  } pod;

 public:
  FuncImport() { memset(&pod, 0, sizeof(CacheablePod)); }

  FuncImport(FuncType&& funcType, uint32_t tlsDataOffset)
      : funcType_(std::move(funcType)) {
    pod.tlsDataOffset_ = tlsDataOffset;
    pod.interpExitCodeOffset_ = 0;
    pod.jitExitCodeOffset_ = 0;
  }

  void initInterpExitOffset(uint32_t off) {
    MOZ_ASSERT(!pod.interpExitCodeOffset_);
    pod.interpExitCodeOffset_ = off;
  }
  void initJitExitOffset(uint32_t off) {
    MOZ_ASSERT(!pod.jitExitCodeOffset_);
    pod.jitExitCodeOffset_ = off;
  }

  const FuncType& funcType() const { return funcType_; }
  uint32_t tlsDataOffset() const { return pod.tlsDataOffset_; }
  uint32_t interpExitCodeOffset() const { return pod.interpExitCodeOffset_; }
  uint32_t jitExitCodeOffset() const { return pod.jitExitCodeOffset_; }

  bool clone(const FuncImport& src) {
    mozilla::PodAssign(&pod, &src.pod);
    return funcType_.clone(src.funcType_);
  }

  WASM_DECLARE_SERIALIZABLE(FuncImport)
};

typedef Vector<FuncImport, 0, SystemAllocPolicy> FuncImportVector;

// Metadata holds all the data that is needed to describe compiled wasm code
// at runtime (as opposed to data that is only used to statically link or
// instantiate a module).
//
// Metadata is built incrementally by ModuleGenerator and then shared immutably
// between modules.
//
// The Metadata structure is split into tier-invariant and tier-variant parts;
// the former points to instances of the latter.  Additionally, the asm.js
// subsystem subclasses the Metadata, adding more tier-invariant data, some of
// which is serialized.  See AsmJS.cpp.

struct MetadataCacheablePod {
  ModuleKind kind;
  MemoryUsage memoryUsage;
  uint64_t minMemoryLength;
  uint32_t globalDataLength;
  Maybe<uint64_t> maxMemoryLength;
  Maybe<uint32_t> startFuncIndex;
  Maybe<uint32_t> nameCustomSectionIndex;
  bool filenameIsURL;
  bool v128Enabled;
  bool omitsBoundsChecks;
  bool usesDuplicateImports;

  explicit MetadataCacheablePod(ModuleKind kind)
      : kind(kind),
        memoryUsage(MemoryUsage::None),
        minMemoryLength(0),
        globalDataLength(0),
        filenameIsURL(false),
        v128Enabled(false),
        omitsBoundsChecks(false),
        usesDuplicateImports(false) {}
};

typedef uint8_t ModuleHash[8];
typedef Vector<ValTypeVector, 0, SystemAllocPolicy> FuncArgTypesVector;
typedef Vector<ValTypeVector, 0, SystemAllocPolicy> FuncReturnTypesVector;

struct Metadata : public ShareableBase<Metadata>, public MetadataCacheablePod {
  TypeDefWithIdVector types;
  GlobalDescVector globals;
  TableDescVector tables;
#ifdef ENABLE_WASM_EXCEPTIONS
  EventDescVector events;
#endif
  CacheableChars filename;
  CacheableChars sourceMapURL;

  // namePayload points at the name section's CustomSection::payload so that
  // the Names (which are use payload-relative offsets) can be used
  // independently of the Module without duplicating the name section.
  SharedBytes namePayload;
  Maybe<Name> moduleName;
  NameVector funcNames;

  // Debug-enabled code is not serialized.
  bool debugEnabled;
  FuncArgTypesVector debugFuncArgTypes;
  FuncReturnTypesVector debugFuncReturnTypes;
  ModuleHash debugHash;

  explicit Metadata(ModuleKind kind = ModuleKind::Wasm)
      : MetadataCacheablePod(kind), debugEnabled(false), debugHash() {}
  virtual ~Metadata() = default;

  MetadataCacheablePod& pod() { return *this; }
  const MetadataCacheablePod& pod() const { return *this; }

  bool usesMemory() const { return memoryUsage != MemoryUsage::None; }
  bool usesSharedMemory() const { return memoryUsage == MemoryUsage::Shared; }

  // Invariant: The result of getFuncResultType can only be used as long as
  // MetaData is live, because the returned ResultType may encode a pointer to
  // debugFuncReturnTypes.
  ResultType getFuncResultType(uint32_t funcIndex) const {
    return ResultType::Vector(debugFuncReturnTypes[funcIndex]);
  };

  // AsmJSMetadata derives Metadata iff isAsmJS(). Mostly this distinction is
  // encapsulated within AsmJS.cpp, but the additional virtual functions allow
  // asm.js to override wasm behavior in the handful of cases that can't be
  // easily encapsulated by AsmJS.cpp.

  bool isAsmJS() const { return kind == ModuleKind::AsmJS; }
  const AsmJSMetadata& asAsmJS() const {
    MOZ_ASSERT(isAsmJS());
    return *(const AsmJSMetadata*)this;
  }
  virtual bool mutedErrors() const { return false; }
  virtual const char16_t* displayURL() const { return nullptr; }
  virtual ScriptSource* maybeScriptSource() const { return nullptr; }

  // The Developer-Facing Display Conventions section of the WebAssembly Web
  // API spec defines two cases for displaying a wasm function name:
  //  1. the function name stands alone
  //  2. the function name precedes the location

  enum NameContext { Standalone, BeforeLocation };

  virtual bool getFuncName(NameContext ctx, uint32_t funcIndex,
                           UTF8Bytes* name) const;

  bool getFuncNameStandalone(uint32_t funcIndex, UTF8Bytes* name) const {
    return getFuncName(NameContext::Standalone, funcIndex, name);
  }
  bool getFuncNameBeforeLocation(uint32_t funcIndex, UTF8Bytes* name) const {
    return getFuncName(NameContext::BeforeLocation, funcIndex, name);
  }

  WASM_DECLARE_SERIALIZABLE(Metadata);
};

using MutableMetadata = RefPtr<Metadata>;
using SharedMetadata = RefPtr<const Metadata>;

struct MetadataTier {
  explicit MetadataTier(Tier tier) : tier(tier) {}

  const Tier tier;

  Uint32Vector funcToCodeRange;
  CodeRangeVector codeRanges;
  CallSiteVector callSites;
  TrapSiteVectorArray trapSites;
  FuncImportVector funcImports;
  FuncExportVector funcExports;
  StackMaps stackMaps;

  // Debug information, not serialized.
  Uint32Vector debugTrapFarJumpOffsets;

  FuncExport& lookupFuncExport(uint32_t funcIndex,
                               size_t* funcExportIndex = nullptr);
  const FuncExport& lookupFuncExport(uint32_t funcIndex,
                                     size_t* funcExportIndex = nullptr) const;

  const CodeRange& codeRange(const FuncExport& funcExport) const {
    return codeRanges[funcToCodeRange[funcExport.funcIndex()]];
  }

  bool clone(const MetadataTier& src);

  WASM_DECLARE_SERIALIZABLE(MetadataTier);
};

using UniqueMetadataTier = UniquePtr<MetadataTier>;

// LazyStubSegment is a code segment lazily generated for function entry stubs
// (both interpreter and jit ones).
//
// Because a stub is usually small (a few KiB) and an executable code segment
// isn't (64KiB), a given stub segment can contain entry stubs of many
// functions.

using UniqueLazyStubSegment = UniquePtr<LazyStubSegment>;
using LazyStubSegmentVector =
    Vector<UniqueLazyStubSegment, 0, SystemAllocPolicy>;

class LazyStubSegment : public CodeSegment {
  CodeRangeVector codeRanges_;
  size_t usedBytes_;

 public:
  LazyStubSegment(UniqueCodeBytes bytes, size_t length)
      : CodeSegment(std::move(bytes), length, CodeSegment::Kind::LazyStubs),
        usedBytes_(0) {}

  static UniqueLazyStubSegment create(const CodeTier& codeTier,
                                      size_t codeLength);

  static size_t AlignBytesNeeded(size_t bytes) {
    return AlignBytes(bytes, gc::SystemPageSize());
  }

  bool hasSpace(size_t bytes) const;
  bool addStubs(size_t codeLength, const Uint32Vector& funcExportIndices,
                const FuncExportVector& funcExports,
                const CodeRangeVector& codeRanges, uint8_t** codePtr,
                size_t* indexFirstInsertedCodeRange);

  const CodeRangeVector& codeRanges() const { return codeRanges_; }
  const CodeRange* lookupRange(const void* pc) const;

  void addSizeOfMisc(MallocSizeOf mallocSizeOf, size_t* code,
                     size_t* data) const;
};

// LazyFuncExport helps to efficiently lookup a CodeRange from a given function
// index. It is inserted in a vector sorted by function index, to perform
// binary search on it later.

struct LazyFuncExport {
  size_t funcIndex;
  size_t lazyStubSegmentIndex;
  size_t funcCodeRangeIndex;
  LazyFuncExport(size_t funcIndex, size_t lazyStubSegmentIndex,
                 size_t funcCodeRangeIndex)
      : funcIndex(funcIndex),
        lazyStubSegmentIndex(lazyStubSegmentIndex),
        funcCodeRangeIndex(funcCodeRangeIndex) {}
};

using LazyFuncExportVector = Vector<LazyFuncExport, 0, SystemAllocPolicy>;

// LazyStubTier contains all the necessary information for lazy function entry
// stubs that are generated at runtime. None of its data is ever serialized.
//
// It must be protected by a lock, because the main thread can both read and
// write lazy stubs at any time while a background thread can regenerate lazy
// stubs for tier2 at any time.

class LazyStubTier {
  LazyStubSegmentVector stubSegments_;
  LazyFuncExportVector exports_;
  size_t lastStubSegmentIndex_;

  bool createMany(const Uint32Vector& funcExportIndices,
                  const CodeTier& codeTier, bool flushAllThreadsIcaches,
                  size_t* stubSegmentIndex);

 public:
  LazyStubTier() : lastStubSegmentIndex_(0) {}

  bool empty() const { return stubSegments_.empty(); }
  bool hasStub(uint32_t funcIndex) const;

  // Returns a pointer to the raw interpreter entry of a given function which
  // stubs have been lazily generated.
  void* lookupInterpEntry(uint32_t funcIndex) const;

  // Creates one lazy stub for the exported function, for which the jit entry
  // will be set to the lazily-generated one.
  bool createOne(uint32_t funcExportIndex, const CodeTier& codeTier);

  // Create one lazy stub for all the functions in funcExportIndices, putting
  // them in a single stub. Jit entries won't be used until
  // setJitEntries() is actually called, after the Code owner has committed
  // tier2.
  bool createTier2(const Uint32Vector& funcExportIndices,
                   const CodeTier& codeTier, Maybe<size_t>* stubSegmentIndex);
  void setJitEntries(const Maybe<size_t>& stubSegmentIndex, const Code& code);

  void addSizeOfMisc(MallocSizeOf mallocSizeOf, size_t* code,
                     size_t* data) const;
};

// CodeTier contains all the data related to a given compilation tier. It is
// built during module generation and then immutably stored in a Code.

using UniqueCodeTier = UniquePtr<CodeTier>;
using UniqueConstCodeTier = UniquePtr<const CodeTier>;

class CodeTier {
  const Code* code_;

  // Serialized information.
  const UniqueMetadataTier metadata_;
  const UniqueModuleSegment segment_;

  // Lazy stubs, not serialized.
  ExclusiveData<LazyStubTier> lazyStubs_;

  static const MutexId& mutexForTier(Tier tier) {
    if (tier == Tier::Baseline) {
      return mutexid::WasmLazyStubsTier1;
    }
    MOZ_ASSERT(tier == Tier::Optimized);
    return mutexid::WasmLazyStubsTier2;
  }

 public:
  CodeTier(UniqueMetadataTier metadata, UniqueModuleSegment segment)
      : code_(nullptr),
        metadata_(std::move(metadata)),
        segment_(std::move(segment)),
        lazyStubs_(mutexForTier(segment_->tier())) {}

  bool initialized() const { return !!code_ && segment_->initialized(); }
  bool initialize(IsTier2 isTier2, const Code& code, const LinkData& linkData,
                  const Metadata& metadata);

  Tier tier() const { return segment_->tier(); }
  const ExclusiveData<LazyStubTier>& lazyStubs() const { return lazyStubs_; }
  const MetadataTier& metadata() const { return *metadata_.get(); }
  const ModuleSegment& segment() const { return *segment_.get(); }
  const Code& code() const {
    MOZ_ASSERT(initialized());
    return *code_;
  }

  const CodeRange* lookupRange(const void* pc) const;

  size_t serializedSize() const;
  uint8_t* serialize(uint8_t* cursor, const LinkData& linkData) const;
  static const uint8_t* deserialize(const uint8_t* cursor,
                                    const LinkData& linkData,
                                    UniqueCodeTier* codeTier);
  void addSizeOfMisc(MallocSizeOf mallocSizeOf, size_t* code,
                     size_t* data) const;
};

// Jump tables to take tiering into account, when calling either from wasm to
// wasm (through rabaldr) or from jit to wasm (jit entry).

class JumpTables {
  using TablePointer = mozilla::UniquePtr<void*[], JS::FreePolicy>;

  CompileMode mode_;
  TablePointer tiering_;
  TablePointer jit_;
  size_t numFuncs_;

 public:
  bool init(CompileMode mode, const ModuleSegment& ms,
            const CodeRangeVector& codeRanges);

  void setJitEntry(size_t i, void* target) const {
    // Make sure that write is atomic; see comment in wasm::Module::finishTier2
    // to that effect.
    MOZ_ASSERT(i < numFuncs_);
    jit_.get()[i] = target;
  }
  void setJitEntryIfNull(size_t i, void* target) const {
    // Make sure that compare-and-write is atomic; see comment in
    // wasm::Module::finishTier2 to that effect.
    MOZ_ASSERT(i < numFuncs_);
    void* expected = nullptr;
    (void)__atomic_compare_exchange_n(&jit_.get()[i], &expected, target,
                                      /*weak=*/false, __ATOMIC_RELAXED,
                                      __ATOMIC_RELAXED);
  }
  void** getAddressOfJitEntry(size_t i) const {
    MOZ_ASSERT(i < numFuncs_);
    MOZ_ASSERT(jit_.get()[i]);
    return &jit_.get()[i];
  }
  size_t funcIndexFromJitEntry(void** target) const {
    MOZ_ASSERT(target >= &jit_.get()[0]);
    MOZ_ASSERT(target <= &(jit_.get()[numFuncs_ - 1]));
    return (intptr_t*)target - (intptr_t*)&jit_.get()[0];
  }

  void setTieringEntry(size_t i, void* target) const {
    MOZ_ASSERT(i < numFuncs_);
    // See comment in wasm::Module::finishTier2.
    if (mode_ == CompileMode::Tier1) {
      tiering_.get()[i] = target;
    }
  }
  void** tiering() const { return tiering_.get(); }

  size_t sizeOfMiscExcludingThis() const {
    // 2 words per function for the jit entry table, plus maybe 1 per
    // function if we're tiering.
    return sizeof(void*) * (2 + (tiering_ ? 1 : 0)) * numFuncs_;
  }
};

// Code objects own executable code and the metadata that describe it. A single
// Code object is normally shared between a module and all its instances.
//
// profilingLabels_ is lazily initialized, but behind a lock.

using SharedCode = RefPtr<const Code>;
using MutableCode = RefPtr<Code>;

class Code : public ShareableBase<Code> {
  UniqueCodeTier tier1_;
  mutable UniqueConstCodeTier tier2_;  // Access only when hasTier2() is true
  mutable Atomic<bool> hasTier2_;
  SharedMetadata metadata_;
  ExclusiveData<CacheableCharsVector> profilingLabels_;
  JumpTables jumpTables_;

 public:
  Code(UniqueCodeTier tier1, const Metadata& metadata,
       JumpTables&& maybeJumpTables);
  bool initialized() const { return tier1_->initialized(); }

  bool initialize(const LinkData& linkData);

  void setTieringEntry(size_t i, void* target) const {
    jumpTables_.setTieringEntry(i, target);
  }
  void** tieringJumpTable() const { return jumpTables_.tiering(); }

  void setJitEntry(size_t i, void* target) const {
    jumpTables_.setJitEntry(i, target);
  }
  void setJitEntryIfNull(size_t i, void* target) const {
    jumpTables_.setJitEntryIfNull(i, target);
  }
  void** getAddressOfJitEntry(size_t i) const {
    return jumpTables_.getAddressOfJitEntry(i);
  }
  uint32_t getFuncIndex(JSFunction* fun) const;

  bool setTier2(UniqueCodeTier tier2, const LinkData& linkData) const;
  void commitTier2() const;

  bool hasTier2() const { return hasTier2_; }
  Tiers tiers() const;
  bool hasTier(Tier t) const;

  Tier stableTier() const;  // This is stable during a run
  Tier bestTier()
      const;  // This may transition from Baseline -> Ion at any time

  const CodeTier& codeTier(Tier tier) const;
  const Metadata& metadata() const { return *metadata_; }

  const ModuleSegment& segment(Tier iter) const {
    return codeTier(iter).segment();
  }
  const MetadataTier& metadata(Tier iter) const {
    return codeTier(iter).metadata();
  }

  // Metadata lookup functions:

  const CallSite* lookupCallSite(void* returnAddress) const;
  const CodeRange* lookupFuncRange(void* pc) const;
  const StackMap* lookupStackMap(uint8_t* nextPC) const;
  bool containsCodePC(const void* pc) const;
  bool lookupTrap(void* pc, Trap* trap, BytecodeOffset* bytecode) const;

  // To save memory, profilingLabels_ are generated lazily when profiling mode
  // is enabled.

  void ensureProfilingLabels(bool profilingEnabled) const;
  const char* profilingLabel(uint32_t funcIndex) const;

  // about:memory reporting:

  void addSizeOfMiscIfNotSeen(MallocSizeOf mallocSizeOf,
                              Metadata::SeenSet* seenMetadata,
                              Code::SeenSet* seenCode, size_t* code,
                              size_t* data) const;

  // A Code object is serialized as the length and bytes of the machine code
  // after statically unlinking it; the Code is then later recreated from the
  // machine code and other parts.

  size_t serializedSize() const;
  uint8_t* serialize(uint8_t* cursor, const LinkData& linkData) const;
  static const uint8_t* deserialize(const uint8_t* cursor,
                                    const LinkData& linkData,
                                    Metadata& metadata, SharedCode* code);
};

void PatchDebugSymbolicAccesses(uint8_t* codeBase, jit::MacroAssembler& masm);

}  // namespace wasm
}  // namespace js

#endif  // wasm_code_h