tor-browser

WasmModuleTypes.h (29251B)

---

/* -*- 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 2021 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_module_types_h
#define wasm_module_types_h

#include "mozilla/RefPtr.h"
#include "mozilla/Span.h"

#include "js/AllocPolicy.h"
#include "js/HashTable.h"
#include "js/RefCounted.h"
#include "js/Utility.h"
#include "js/Vector.h"

#include "wasm/WasmCompileArgs.h"
#include "wasm/WasmConstants.h"
#include "wasm/WasmExprType.h"
#include "wasm/WasmInitExpr.h"
#include "wasm/WasmMemory.h"
#include "wasm/WasmSerialize.h"
#include "wasm/WasmShareable.h"
#include "wasm/WasmTypeDecls.h"
#include "wasm/WasmValType.h"
#include "wasm/WasmValue.h"

namespace js {
namespace wasm {

class FuncType;

// A Module can either be asm.js or wasm.

enum ModuleKind { Wasm, AsmJS };

// CacheableChars is used to cacheably store UniqueChars.

struct CacheableChars : UniqueChars {
 CacheableChars() = default;
 explicit CacheableChars(char* ptr) : UniqueChars(ptr) {}
 MOZ_IMPLICIT CacheableChars(UniqueChars&& rhs)
     : UniqueChars(std::move(rhs)) {}
 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using CacheableCharsVector = Vector<CacheableChars, 0, SystemAllocPolicy>;

// CacheableName is used to cacheably store a UTF-8 string that may contain
// null terminators in sequence.

struct CacheableName {
private:
 UTF8Bytes bytes_;

 const char* begin() const { return (const char*)bytes_.begin(); }
 size_t length() const { return bytes_.length(); }

public:
 CacheableName() = default;
 MOZ_IMPLICIT CacheableName(UTF8Bytes&& rhs) : bytes_(std::move(rhs)) {}

 bool isEmpty() const { return bytes_.length() == 0; }

 mozilla::Span<char> utf8Bytes() { return mozilla::Span<char>(bytes_); }
 mozilla::Span<const char> utf8Bytes() const {
   return mozilla::Span<const char>(bytes_);
 }

 [[nodiscard]] bool clone(CacheableName* name) const {
   UTF8Bytes bytesCopy;
   if (!bytesCopy.appendAll(bytes_)) {
     return false;
   }
   *name = CacheableName(std::move(bytesCopy));
   return true;
 }

 static CacheableName fromUTF8Chars(UniqueChars&& utf8Chars);
 [[nodiscard]] static bool fromUTF8Chars(const char* utf8Chars,
                                         CacheableName* name);

 [[nodiscard]] JSString* toJSString(JSContext* cx) const;
 [[nodiscard]] JSAtom* toAtom(JSContext* cx) const;
 [[nodiscard]] bool toPropertyKey(JSContext* cx,
                                  MutableHandleId propertyKey) const;
 [[nodiscard]] UniqueChars toQuotedString(JSContext* cx) const;

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 WASM_DECLARE_FRIEND_SERIALIZE(CacheableName);
};

using CacheableNameVector = Vector<CacheableName, 0, SystemAllocPolicy>;

// A hash policy for names.
struct NameHasher {
 using Key = mozilla::Span<const char>;
 using Lookup = mozilla::Span<const char>;

 static HashNumber hash(const Lookup& aLookup) {
   return mozilla::HashString(aLookup.data(), aLookup.Length());
 }

 static bool match(const Key& aKey, const Lookup& aLookup) {
   return aKey == aLookup;
 }
};

// Import describes a single wasm import. An ImportVector describes all
// of a single module's imports.
//
// ImportVector is built incrementally by ModuleGenerator and then stored
// immutably by Module.

struct Import {
 CacheableName module;
 CacheableName field;
 DefinitionKind kind;

 Import() = default;
 Import(CacheableName&& module, CacheableName&& field, DefinitionKind kind)
     : module(std::move(module)), field(std::move(field)), kind(kind) {}

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using ImportVector = Vector<Import, 0, SystemAllocPolicy>;

// Export describes the export of a definition in a Module to a field in the
// export object. The Export stores the index of the exported item in the
// appropriate type-specific module data structure (function table, global
// table, table table, and - eventually - memory table).
//
// Note a single definition can be exported by multiple Exports in the
// ExportVector.
//
// ExportVector is built incrementally by ModuleGenerator and then stored
// immutably by Module.

class Export {
public:
 struct CacheablePod {
   DefinitionKind kind_;
   uint32_t index_;

   WASM_CHECK_CACHEABLE_POD(kind_, index_);
 };

private:
 CacheableName fieldName_;
 CacheablePod pod;

public:
 Export() = default;
 explicit Export(CacheableName&& fieldName, uint32_t index,
                 DefinitionKind kind);

 const CacheableName& fieldName() const { return fieldName_; }

 DefinitionKind kind() const { return pod.kind_; }
 uint32_t funcIndex() const;
 uint32_t tagIndex() const;
 uint32_t memoryIndex() const;
 uint32_t globalIndex() const;
 uint32_t tableIndex() const;

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 WASM_DECLARE_FRIEND_SERIALIZE(Export);
};

WASM_DECLARE_CACHEABLE_POD(Export::CacheablePod);

using ExportVector = Vector<Export, 0, SystemAllocPolicy>;

// FuncFlags provides metadata for a function definition.

enum class FuncFlags : uint8_t {
 None = 0x0,
 // The function maybe be accessible by JS and needs thunks generated for it.
 // See `[SMDOC] Exported wasm functions and the jit-entry stubs` in
 // WasmJS.cpp for more information.
 Exported = 0x1,
 // The function should have thunks generated upon instantiation, not upon
 // first call. May only be set if `Exported` is set.
 Eager = 0x2,
 // The function can be the target of a ref.func instruction in the code
 // section. May only be set if `Exported` is set.
 CanRefFunc = 0x4,
};

// A FuncDesc describes a single function definition.

struct FuncDesc {
 // Bit pack to keep this struct small on 32-bit systems
 uint32_t typeIndex : 24;
 FuncFlags flags : 8;

 WASM_CHECK_CACHEABLE_POD(typeIndex, flags);

 // Assert that the bit packing scheme is viable
 static_assert(MaxTypes <= (1 << 24) - 1);
 static_assert(sizeof(FuncFlags) == sizeof(uint8_t));

 FuncDesc() = default;
 explicit FuncDesc(uint32_t typeIndex)
     : typeIndex(typeIndex), flags(FuncFlags::None) {}

 void declareFuncExported(bool eager, bool canRefFunc) {
   // Set the `Exported` flag, if not set.
   flags = FuncFlags(uint8_t(flags) | uint8_t(FuncFlags::Exported));

   // Merge in the `Eager` and `CanRefFunc` flags, if they're set. Be sure
   // to not unset them if they've already been set.
   if (eager) {
     flags = FuncFlags(uint8_t(flags) | uint8_t(FuncFlags::Eager));
   }
   if (canRefFunc) {
     flags = FuncFlags(uint8_t(flags) | uint8_t(FuncFlags::CanRefFunc));
   }
 }

 bool isExported() const {
   return uint8_t(flags) & uint8_t(FuncFlags::Exported);
 }
 bool isEager() const { return uint8_t(flags) & uint8_t(FuncFlags::Eager); }
 bool canRefFunc() const {
   return uint8_t(flags) & uint8_t(FuncFlags::CanRefFunc);
 }
};

WASM_DECLARE_CACHEABLE_POD(FuncDesc);

using FuncDescVector = Vector<FuncDesc, 0, SystemAllocPolicy>;

struct CallRefMetricsRange {
 explicit CallRefMetricsRange() {}
 explicit CallRefMetricsRange(uint32_t begin, uint32_t length)
     : begin(begin), length(length) {}

 uint32_t begin = 0;
 uint32_t length = 0;

 void offsetBy(uint32_t offset) { begin += offset; }

 WASM_CHECK_CACHEABLE_POD(begin, length);
};

struct AllocSitesRange {
 explicit AllocSitesRange() {}
 explicit AllocSitesRange(uint32_t begin, uint32_t length)
     : begin(begin), length(length) {}

 uint32_t begin = 0;
 uint32_t length = 0;

 void offsetBy(uint32_t offset) { begin += offset; }

 WASM_CHECK_CACHEABLE_POD(begin, length);
};

// A compact plain data summary of CallRefMetrics for use by our function
// compilers. See CallRefMetrics in WasmInstanceData.h for more information.
//
// We cannot allow the metrics collected by an instance to directly be read
// from our function compilers because they contain thread-local data and are
// written into without any synchronization.
//
// Instead, CodeMetadata contains an array of CallRefHint that every instance
// writes into when it has a function that requests a tier-up. This array is
// 1:1 with the non-threadsafe CallRefMetrics that is stored on the instance.
//
// This class must be thread safe, as it's read and written from different
// threads.  It is an array of up to 3 function indices, and the entire array
// can be read/written atomically.  Each function index is represented in 20
// bits, and 2 of the remaining 4 bits are used to indicate the array's current
// size.
//
// Although unstated and unenforced here, it is expected that -- in the case
// where more than one function index is stored -- the func index at `.get(0)`
// is the "most important" in terms of inlining, that at `.get(1)` is the
// second most important, etc.
//
// Note that the fact that this array has 3 elements is unrelated to the value
// of CallRefMetrics::NUM_TRACKED.  The target-collection mechanism will work
// properly even if CallRefMetrics::NUM_TRACKED is greater than 3, in which
// case at most only 3 targets (probably the hottest ones) will get baked into
// the CallRefHint.
class CallRefHint {
public:
 using Repr = uint64_t;
 static constexpr size_t NUM_ENTRIES = 3;

private:
 // Representation is:
 //
 // 63  61   42  41   22  21    2  1    0
 // |   |     |  |     |  |     |  |    |
 // 00  index#2  index#1  index#0  length
 static constexpr uint32_t ElemBits = 20;
 static constexpr uint32_t LengthBits = 2;
 static constexpr uint64_t Mask = (uint64_t(1) << ElemBits) - 1;
 static_assert(js::wasm::MaxFuncs <= Mask);
 static_assert(3 * ElemBits + LengthBits <= 8 * sizeof(Repr));

 Repr state_ = 0;

 bool valid() const {
   // Shift out the length field and all of the entries that the length field
   // implies are occupied.  What remains should be all zeroes.
   return (state_ >> (length() * ElemBits + LengthBits)) == 0;
 }

public:
 // We omit the obvious single-argument constructor that takes a `Repr`,
 // because that is too easily confused with one that takes a function index,
 // and in any case it is not necessary.

 uint32_t length() const { return state_ & 3; }
 bool empty() const { return length() == 0; }
 bool full() const { return length() == 3; }

 uint32_t get(uint32_t index) const {
   MOZ_ASSERT(index < length());
   uint64_t res = (state_ >> (index * ElemBits + LengthBits)) & Mask;
   return uint32_t(res);
 }
 void set(uint32_t index, uint32_t funcIndex) {
   MOZ_ASSERT(index < length());
   MOZ_ASSERT(funcIndex <= Mask);
   uint32_t shift = index * ElemBits + LengthBits;
   uint64_t c = uint64_t(Mask) << shift;
   uint64_t s = uint64_t(funcIndex) << shift;
   state_ = (state_ & ~c) | s;
 }

 void append(uint32_t funcIndex) {
   MOZ_RELEASE_ASSERT(!full());
   // We know the lowest two bits of `state_` are not 0b11, so we can
   // increment the length field by incrementing `state_` as a whole.
   state_++;
   set(length() - 1, funcIndex);
 }

 static CallRefHint fromRepr(Repr repr) {
   CallRefHint res;
   res.state_ = repr;
   MOZ_ASSERT(res.valid());
   return res;
 }
 Repr toRepr() const { return state_; }
};

static_assert(sizeof(CallRefHint) == sizeof(CallRefHint::Repr));

using MutableCallRefHint = mozilla::Atomic<CallRefHint::Repr>;
using MutableCallRefHints =
   mozilla::UniquePtr<MutableCallRefHint[], JS::FreePolicy>;

WASM_DECLARE_CACHEABLE_POD(CallRefMetricsRange);

using CallRefMetricsRangeVector =
   Vector<CallRefMetricsRange, 0, SystemAllocPolicy>;

WASM_DECLARE_CACHEABLE_POD(AllocSitesRange);

using AllocSitesRangeVector = Vector<AllocSitesRange, 0, SystemAllocPolicy>;

enum class BranchHint : uint8_t { Unlikely = 0, Likely = 1, Invalid = 2 };

// Stores pairs of <BranchOffset, BranchHint>
struct BranchHintEntry {
 uint32_t branchOffset;
 BranchHint value;

 BranchHintEntry() = default;
 BranchHintEntry(uint32_t branchOffset, BranchHint value)
     : branchOffset(branchOffset), value(value) {}
};

// Branch hint sorted vector for a function,
// stores tuples of <BranchOffset, BranchHint>
using BranchHintVector = Vector<BranchHintEntry, 0, SystemAllocPolicy>;
using BranchHintFuncMap = HashMap<uint32_t, BranchHintVector,
                                 DefaultHasher<uint32_t>, SystemAllocPolicy>;

struct BranchHintCollection {
private:
 // Used for lookups into the collection if a function
 // doesn't contain any hints.
 static BranchHintVector invalidVector_;

 // Map from function index to their collection of branch hints
 BranchHintFuncMap branchHintsMap_;
 // Whether the module had branch hints, but we failed to parse them. This
 // is not semantically visible to user code, but used for internal testing.
 bool failedParse_ = false;

public:
 // Add all the branch hints for a function
 [[nodiscard]] bool addHintsForFunc(uint32_t functionIndex,
                                    BranchHintVector&& branchHints) {
   return branchHintsMap_.put(functionIndex, std::move(branchHints));
 }

 // Return the vector with branch hints for a funcIndex.
 // If this function doesn't contain any hints, return an empty vector.
 BranchHintVector& getHintVector(uint32_t funcIndex) const {
   if (auto hintsVector =
           branchHintsMap_.readonlyThreadsafeLookup(funcIndex)) {
     return hintsVector->value();
   }

   // If not found, return the empty invalid Vector
   return invalidVector_;
 }

 bool isEmpty() const { return branchHintsMap_.empty(); }

 void setFailedAndClear() {
   failedParse_ = true;
   branchHintsMap_.clearAndCompact();
 }
 bool failedParse() const { return failedParse_; }
};

enum class GlobalKind { Import, Constant, Variable };

// A GlobalDesc describes a single global variable.
//
// wasm can import and export mutable and immutable globals.
//
// asm.js can import mutable and immutable globals, but a mutable global has a
// location that is private to the module, and its initial value is copied into
// that cell from the environment.  asm.js cannot export globals.
class GlobalDesc {
 GlobalKind kind_;
 // Stores the value type of this global for all kinds, and the initializer
 // expression when `constant` or `variable`.
 InitExpr initial_;
 // Metadata for the global when `variable` or `import`.
 unsigned offset_;
 bool isMutable_;
 bool isWasm_;
 bool isExport_;
 // Metadata for the global when `import`.
 uint32_t importIndex_;

 // Private, as they have unusual semantics.

 bool isExport() const { return !isConstant() && isExport_; }
 bool isWasm() const { return !isConstant() && isWasm_; }

public:
 GlobalDesc() = default;

 explicit GlobalDesc(InitExpr&& initial, bool isMutable,
                     ModuleKind kind = ModuleKind::Wasm)
     : kind_((!isMutable && initial.isLiteral()) ? GlobalKind::Constant
                                                 : GlobalKind::Variable) {
   initial_ = std::move(initial);
   if (isVariable()) {
     isMutable_ = isMutable;
     isWasm_ = kind == Wasm;
     isExport_ = false;
     offset_ = UINT32_MAX;
   }
 }

 explicit GlobalDesc(ValType type, bool isMutable, uint32_t importIndex,
                     ModuleKind kind = ModuleKind::Wasm)
     : kind_(GlobalKind::Import) {
   initial_ = InitExpr(LitVal(type));
   importIndex_ = importIndex;
   isMutable_ = isMutable;
   isWasm_ = kind == Wasm;
   isExport_ = false;
   offset_ = UINT32_MAX;
 }

 void setOffset(unsigned offset) {
   MOZ_ASSERT(!isConstant());
   MOZ_ASSERT(offset_ == UINT32_MAX);
   offset_ = offset;
 }
 unsigned offset() const {
   MOZ_ASSERT(!isConstant());
   MOZ_ASSERT(offset_ != UINT32_MAX);
   return offset_;
 }

 void setIsExport() {
   if (!isConstant()) {
     isExport_ = true;
   }
 }

 GlobalKind kind() const { return kind_; }
 bool isVariable() const { return kind_ == GlobalKind::Variable; }
 bool isConstant() const { return kind_ == GlobalKind::Constant; }
 bool isImport() const { return kind_ == GlobalKind::Import; }

 bool isMutable() const { return !isConstant() && isMutable_; }
 const InitExpr& initExpr() const {
   MOZ_ASSERT(!isImport());
   return initial_;
 }
 uint32_t importIndex() const {
   MOZ_ASSERT(isImport());
   return importIndex_;
 }

 LitVal constantValue() const { return initial_.literal(); }

 // If isIndirect() is true then storage for the value is not in the
 // instance's global area, but in a WasmGlobalObject::Cell hanging off a
 // WasmGlobalObject; the global area contains a pointer to the Cell.
 //
 // We don't want to indirect unless we must, so only mutable, exposed
 // globals are indirected - in all other cases we copy values into and out
 // of their module.
 //
 // Note that isIndirect() isn't equivalent to getting a WasmGlobalObject:
 // an immutable exported global will still get an object, but will not be
 // indirect.
 bool isIndirect() const {
   return isMutable() && isWasm() && (isImport() || isExport());
 }

 ValType type() const { return initial_.type(); }

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 WASM_DECLARE_FRIEND_SERIALIZE(GlobalDesc);
};

using GlobalDescVector = Vector<GlobalDesc, 0, SystemAllocPolicy>;

// A TagDesc represents fresh per-instance tags that are used for the
// exception handling proposal and potentially other future proposals.

// The TagOffsetVector represents the offsets in the layout of the
// data buffer stored in a Wasm exception.
using TagOffsetVector = Vector<uint32_t, 2, SystemAllocPolicy>;

class TagType : public AtomicRefCounted<TagType> {
 SharedTypeDef type_;
 TagOffsetVector argOffsets_;
 uint32_t size_;

public:
 TagType() : size_(0) {}

 [[nodiscard]] bool initialize(const SharedTypeDef& funcType);

 const TypeDef& type() const { return *type_; }
 const ValTypeVector& argTypes() const { return type_->funcType().args(); }
 const TagOffsetVector& argOffsets() const { return argOffsets_; }
 ResultType resultType() const { return ResultType::Vector(argTypes()); }

 uint32_t tagSize() const { return size_; }

 static bool matches(const TagType& a, const TagType& b) {
   // Note that this does NOT use subtyping. This is deliberate per the spec.
   return a.type_ == b.type_;
 }

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 WASM_DECLARE_FRIEND_SERIALIZE(TagType);
};

using MutableTagType = RefPtr<TagType>;
using SharedTagType = RefPtr<const TagType>;

struct TagDesc {
 TagKind kind;
 SharedTagType type;
 bool isExport;

 TagDesc() : isExport(false) {}
 TagDesc(TagKind kind, const SharedTagType& type, bool isExport = false)
     : kind(kind), type(type), isExport(isExport) {}

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using TagDescVector = Vector<TagDesc, 0, SystemAllocPolicy>;
using ElemExprOffsetVector = Vector<size_t, 0, SystemAllocPolicy>;

// This holds info about elem segments that is needed for instantiation.  It
// can be dropped when the associated wasm::Module is dropped.
struct ModuleElemSegment {
 enum class Kind {
   Active,
   Passive,
   Declared,
 };

 // The type of encoding used by this element segment. 0 is an invalid value to
 // make sure we notice if we fail to correctly initialize the element segment
 // - reading from the wrong representation could be a bad time.
 enum class Encoding {
   Indices = 1,
   Expressions,
 };

 struct Expressions {
   size_t count = 0;
   Bytes exprBytes;

   size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
 };

 Kind kind;
 uint32_t tableIndex;
 RefType elemType;
 mozilla::Maybe<InitExpr> offsetIfActive;

 // We store either an array of indices or the full bytecode of the element
 // expressions, depending on the encoding used for the element segment.
 Encoding encoding;
 Uint32Vector elemIndices;
 Expressions elemExpressions;

 bool active() const { return kind == Kind::Active; }

 const InitExpr& offset() const { return *offsetIfActive; }

 size_t numElements() const {
   switch (encoding) {
     case Encoding::Indices:
       return elemIndices.length();
     case Encoding::Expressions:
       return elemExpressions.count;
     default:
       MOZ_CRASH("unknown element segment encoding");
   }
 }

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using ModuleElemSegmentVector = Vector<ModuleElemSegment, 0, SystemAllocPolicy>;

using InstanceElemSegment = GCVector<HeapPtr<AnyRef>, 0, SystemAllocPolicy>;
using InstanceElemSegmentVector =
   GCVector<InstanceElemSegment, 0, SystemAllocPolicy>;

// DataSegmentRange holds the initial results of decoding a data segment from
// the bytecode and is stored in the ModuleMetadata.  It contains the bytecode
// bounds of the data segment, and some auxiliary information, but not the
// segment contents itself.
//
// When compilation completes, each DataSegmentRange is transformed into a
// DataSegment, which are also stored in the ModuleMetadata.  DataSegment
// contains the same information as DataSegmentRange but additionally contains
// the segment contents itself.  This allows non-compilation uses of wasm
// validation to avoid expensive copies.
//
// A DataSegment that is "passive" is shared between a ModuleMetadata and its
// wasm::Instances.  To allow each segment to be released as soon as the last
// Instance mem.drops it and the Module (hence, also the ModuleMetadata) is
// destroyed, each DataSegment is individually atomically ref-counted.

constexpr uint32_t InvalidMemoryIndex = UINT32_MAX;
static_assert(InvalidMemoryIndex > MaxMemories, "Invariant");

struct DataSegmentRange {
 uint32_t memoryIndex;
 mozilla::Maybe<InitExpr> offsetIfActive;
 uint32_t bytecodeOffset;
 uint32_t length;
};

using DataSegmentRangeVector = Vector<DataSegmentRange, 0, SystemAllocPolicy>;

struct DataSegment : AtomicRefCounted<DataSegment> {
 uint32_t memoryIndex;
 mozilla::Maybe<InitExpr> offsetIfActive;
 Bytes bytes;

 DataSegment() = default;

 bool active() const { return !!offsetIfActive; }

 const InitExpr& offset() const { return *offsetIfActive; }

 [[nodiscard]] bool init(const BytecodeSource& bytecode,
                         const DataSegmentRange& src) {
   memoryIndex = src.memoryIndex;
   if (src.offsetIfActive) {
     offsetIfActive.emplace();
     if (!offsetIfActive->clone(*src.offsetIfActive)) {
       return false;
     }
   }
   MOZ_ASSERT(bytes.length() == 0);
   BytecodeSpan span =
       bytecode.getSpan(BytecodeRange(src.bytecodeOffset, src.length));
   return bytes.append(span.data(), span.size());
 }

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using MutableDataSegment = RefPtr<DataSegment>;
using SharedDataSegment = RefPtr<const DataSegment>;
using DataSegmentVector = Vector<SharedDataSegment, 0, SystemAllocPolicy>;

// CustomSectionRange and CustomSection are related in the same way that
// DataSegmentRange and DataSegment are: the CustomSectionRanges are stored in
// the ModuleMetadata, and are transformed into CustomSections at the end of
// compilation and stored in wasm::Module.

struct CustomSectionRange {
 BytecodeRange name;
 BytecodeRange payload;

 WASM_CHECK_CACHEABLE_POD(name, payload);
};

WASM_DECLARE_CACHEABLE_POD(CustomSectionRange);

using CustomSectionRangeVector =
   Vector<CustomSectionRange, 0, SystemAllocPolicy>;

struct CustomSection {
 Bytes name;
 SharedBytes payload;

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

using CustomSectionVector = Vector<CustomSection, 0, SystemAllocPolicy>;

// A Name represents a string of utf8 chars embedded within the name custom
// section. The offset of a name is expressed relative to the beginning of the
// name section's payload so that Names can stored in wasm::Code, which only
// holds the name section's bytes, not the whole bytecode.

struct Name {
 // All fields are treated as cacheable POD:
 uint32_t offsetInNamePayload;
 uint32_t length;

 WASM_CHECK_CACHEABLE_POD(offsetInNamePayload, length);

 Name() : offsetInNamePayload(UINT32_MAX), length(0) {}
};

WASM_DECLARE_CACHEABLE_POD(Name);

using NameVector = Vector<Name, 0, SystemAllocPolicy>;

struct NameSection {
 Name moduleName;
 NameVector funcNames;
 uint32_t customSectionIndex;

 size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
};

// The kind of limits to decode or convert from JS.

enum class LimitsKind {
 Memory,
 Table,
};

extern const char* ToString(LimitsKind kind);

// Represents the resizable limits of memories and tables.

struct Limits {
 // `addressType` may be I64 when memory64 is enabled.
 AddressType addressType;

 // The initial and maximum limit. The unit is pages for memories and elements
 // for tables.
 uint64_t initial;
 mozilla::Maybe<uint64_t> maximum;

 // `shared` is Shareable::False for tables but may be Shareable::True for
 // memories.
 Shareable shared;

 // `pageSize` is used only for memories. Defaults to the standard page size
 // but may be set to other values with the custom page size proposal.
 PageSize pageSize = PageSize::Standard;

 WASM_CHECK_CACHEABLE_POD(addressType, initial, maximum, shared, pageSize);

 Limits() = default;
 Limits(uint64_t initial, const mozilla::Maybe<uint64_t>& maximum,
        Shareable shared, PageSize pageSize)
     : addressType(AddressType::I32),
       initial(initial),
       maximum(maximum),
       shared(shared),
       pageSize(pageSize) {}
};

WASM_DECLARE_CACHEABLE_POD(Limits);

// MemoryDesc describes a memory.

struct MemoryDesc {
 // The limits of this memory
 Limits limits;
 // The index of the import if this memory is imported
 mozilla::Maybe<uint32_t> importIndex;

 WASM_CHECK_CACHEABLE_POD(limits, importIndex);

 bool isShared() const { return limits.shared == Shareable::True; }

 // Whether a backing store for this memory may move when grown.
 bool canMovingGrow() const { return limits.maximum.isNothing(); }

 // Whether the boundsCheckLimit will always fit within 32 bits. See the SMDOC
 // for "WASM Linear Memory structure".
 bool boundsCheckLimitIsAlways32Bits() const {
   return limits.maximum.isSome() &&
          limits.maximum.value() < (0x100000000 / PageSizeInBytes(pageSize()));
 }

 AddressType addressType() const { return limits.addressType; }

 PageSize pageSize() const { return limits.pageSize; }

 // The initial length of this memory in pages.
 Pages initialPages() const {
   return Pages::fromPageCount(limits.initial, pageSize());
 }

 // The maximum length of this memory in pages.
 mozilla::Maybe<Pages> maximumPages() const {
   return limits.maximum.map(
       [&](uint64_t x) { return Pages::fromPageCount(x, pageSize()); });
 }

 uint64_t initialLength() const {
   // See static_assert after MemoryDesc for why this is safe for memory32.
   MOZ_ASSERT_IF(addressType() == AddressType::I64,
                 limits.initial <= UINT64_MAX / PageSizeInBytes(pageSize()));
   return addressType() == AddressType::I64 ? initialPages().byteLength64()
                                            : initialPages().byteLength();
 }

 MemoryDesc() = default;
 explicit MemoryDesc(Limits limits)
     : limits(limits), importIndex(mozilla::Nothing()) {}
};

WASM_DECLARE_CACHEABLE_POD(MemoryDesc);

using MemoryDescVector = Vector<MemoryDesc, 1, SystemAllocPolicy>;

// We never need to worry about overflow with a Memory32 field when
// using a uint64_t.
static_assert(MaxMemory32StandardPagesValidation <=
             UINT64_MAX / StandardPageSizeBytes);
#ifdef ENABLE_WASM_CUSTOM_PAGE_SIZES
static_assert(MaxMemory32TinyPagesValidation <= UINT64_MAX);
#endif

struct TableDesc {
 Limits limits;
 RefType elemType;
 bool isImported;
 bool isExported;
 bool isAsmJS;
 mozilla::Maybe<InitExpr> initExpr;

 TableDesc() = default;
 TableDesc(Limits limits, RefType elemType,
           mozilla::Maybe<InitExpr>&& initExpr, bool isAsmJS,
           bool isImported = false, bool isExported = false)
     : limits(limits),
       elemType(elemType),
       isImported(isImported),
       isExported(isExported),
       isAsmJS(isAsmJS),
       initExpr(std::move(initExpr)) {}

 AddressType addressType() const { return limits.addressType; }

 uint64_t initialLength() const { return limits.initial; }

 mozilla::Maybe<uint64_t> maximumLength() const { return limits.maximum; }
};

using TableDescVector = Vector<TableDesc, 0, SystemAllocPolicy>;

}  // namespace wasm
}  // namespace js

#endif  // wasm_module_types_h