1 files changed, 661 insertions, 0 deletions
diff --git a/js/src/frontend/StencilXdr.cpp b/js/src/frontend/StencilXdr.cpp
new file mode 100644
index 0000000000..2a42ba0da0
--- /dev/null
+++ b/js/src/frontend/StencilXdr.cpp
@@ -0,0 +1,661 @@
+/* -*- 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/StencilXdr.h"  // StencilXDR
+
+#include "mozilla/OperatorNewExtensions.h"  // mozilla::KnownNotNull
+#include "mozilla/Variant.h"                // mozilla::AsVariant
+
+#include <stddef.h>     // size_t
+#include <stdint.h>     // uint8_t, uint16_t, uint32_t
+#include <type_traits>  // std::has_unique_object_representations
+#include <utility>      // std::forward
+
+#include "frontend/CompilationInfo.h"  // BaseCompilationStencil
+#include "frontend/ScriptIndex.h"      // ScriptIndex
+#include "vm/JSScript.h"               // js::CheckCompileOptionsMatch
+#include "vm/StencilEnums.h"           // js::ImmutableScriptFlagsEnum
+
+using namespace js;
+using namespace js::frontend;
+
+template <typename NameType>
+struct CanEncodeNameType {
+  static constexpr bool value = false;
+};
+
+template <>
+struct CanEncodeNameType<TaggedParserAtomIndex> {
+  static constexpr bool value = true;
+};
+
+template <XDRMode mode, typename ScopeT>
+/* static */ XDRResult StencilXDR::ScopeSpecificData(
+    XDRState<mode>* xdr, BaseParserScopeData*& baseScopeData) {
+  using SlotInfo = typename ScopeT::SlotInfo;
+  using ScopeDataT = typename ScopeT::ParserData;
+
+  static_assert(CanEncodeNameType<typename ScopeDataT::NameType>::value);
+  static_assert(CanCopyDataToDisk<ScopeDataT>::value,
+                "ScopeData cannot be bulk-copied to disk");
+
+  static_assert(offsetof(ScopeDataT, slotInfo) == 0,
+                "slotInfo should be the first field");
+  static_assert(offsetof(ScopeDataT, trailingNames) == sizeof(SlotInfo),
+                "trailingNames should be the second field");
+
+  MOZ_TRY(xdr->align32());
+
+  const SlotInfo* slotInfo;
+  if (mode == XDR_ENCODE) {
+    ScopeDataT* scopeData = static_cast<ScopeDataT*>(baseScopeData);
+    slotInfo = &scopeData->slotInfo;
+  } else {
+    MOZ_TRY(xdr->peekData(&slotInfo));
+  }
+
+  uint32_t totalLength =
+      sizeof(SlotInfo) +
+      sizeof(AbstractBindingName<TaggedParserAtomIndex>) * slotInfo->length;
+  MOZ_TRY(xdr->borrowedData(&baseScopeData, totalLength));
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T, size_t N, class AP>
+static XDRResult XDRVectorUninitialized(XDRState<mode>* xdr,
+                                        Vector<T, N, AP>& vec,
+                                        uint32_t& length) {
+  if (mode == XDR_ENCODE) {
+    MOZ_ASSERT(vec.length() <= UINT32_MAX);
+    length = vec.length();
+  }
+
+  MOZ_TRY(xdr->codeUint32(&length));
+
+  if (mode == XDR_DECODE) {
+    MOZ_ASSERT(vec.empty());
+    if (!vec.resizeUninitialized(length)) {
+      js::ReportOutOfMemory(xdr->cx());
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T, size_t N, class AP>
+static XDRResult XDRVectorInitialized(XDRState<mode>* xdr,
+                                      Vector<T, N, AP>& vec, uint32_t length) {
+  MOZ_ASSERT_IF(mode == XDR_ENCODE, length == vec.length());
+
+  if (mode == XDR_DECODE) {
+    MOZ_ASSERT(vec.empty());
+    if (!vec.resize(length)) {
+      js::ReportOutOfMemory(xdr->cx());
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T, size_t N, class AP>
+static XDRResult XDRVectorInitialized(XDRState<mode>* xdr,
+                                      Vector<T, N, AP>& vec) {
+  uint32_t length;
+  if (mode == XDR_ENCODE) {
+    MOZ_ASSERT(vec.length() <= UINT32_MAX);
+    length = vec.length();
+  }
+
+  MOZ_TRY(xdr->codeUint32(&length));
+
+  return XDRVectorInitialized(xdr, vec, length);
+}
+
+template <XDRMode mode, typename T, size_t N, class AP>
+static XDRResult XDRVectorContent(XDRState<mode>* xdr, Vector<T, N, AP>& vec) {
+  static_assert(CanCopyDataToDisk<T>::value,
+                "Vector content cannot be bulk-copied to disk.");
+
+  uint32_t length;
+  MOZ_TRY(XDRVectorUninitialized(xdr, vec, length));
+  MOZ_TRY(xdr->codeBytes(vec.begin(), sizeof(T) * length));
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T>
+static XDRResult XDRSpanInitialized(XDRState<mode>* xdr, mozilla::Span<T>& span,
+                                    uint32_t size) {
+  MOZ_ASSERT_IF(mode == XDR_ENCODE, size == span.size());
+
+  if (mode == XDR_DECODE) {
+    MOZ_ASSERT(span.empty());
+    if (size > 0) {
+      auto* p = xdr->stencilAlloc().template newArrayUninitialized<T>(size);
+      if (!p) {
+        js::ReportOutOfMemory(xdr->cx());
+        return xdr->fail(JS::TranscodeResult_Throw);
+      }
+      span = mozilla::Span(p, size);
+
+      for (size_t i = 0; i < size; i++) {
+        new (mozilla::KnownNotNull, &span[i]) T();
+      }
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T>
+static XDRResult XDRSpanContent(XDRState<mode>* xdr, mozilla::Span<T>& span,
+                                uint32_t size) {
+  static_assert(CanCopyDataToDisk<T>::value,
+                "Span cannot be bulk-copied to disk.");
+  MOZ_ASSERT_IF(mode == XDR_ENCODE, size == span.size());
+
+  if (size) {
+    MOZ_TRY(xdr->align32());
+
+    T* data;
+    if (mode == XDR_ENCODE) {
+      data = span.data();
+    }
+    MOZ_TRY(xdr->borrowedData(&data, sizeof(T) * size));
+    if (mode == XDR_DECODE) {
+      span = mozilla::Span(data, size);
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode, typename T>
+static XDRResult XDRSpanContent(XDRState<mode>* xdr, mozilla::Span<T>& span) {
+  uint32_t size;
+  if (mode == XDR_ENCODE) {
+    MOZ_ASSERT(span.size() <= UINT32_MAX);
+    size = span.size();
+  }
+
+  MOZ_TRY(xdr->codeUint32(&size));
+
+  return XDRSpanContent(xdr, span, size);
+}
+
+template <XDRMode mode>
+static XDRResult XDRStencilModuleMetadata(XDRState<mode>* xdr,
+                                          StencilModuleMetadata& stencil) {
+  MOZ_TRY(XDRVectorContent(xdr, stencil.requestedModules));
+  MOZ_TRY(XDRVectorContent(xdr, stencil.importEntries));
+  MOZ_TRY(XDRVectorContent(xdr, stencil.localExportEntries));
+  MOZ_TRY(XDRVectorContent(xdr, stencil.indirectExportEntries));
+  MOZ_TRY(XDRVectorContent(xdr, stencil.starExportEntries));
+  MOZ_TRY(XDRVectorContent(xdr, stencil.functionDecls));
+
+  uint8_t isAsync = 0;
+  if (mode == XDR_ENCODE) {
+    if (stencil.isAsync) {
+      isAsync = stencil.isAsync ? 1 : 0;
+    }
+  }
+
+  MOZ_TRY(xdr->codeUint8(&isAsync));
+
+  if (mode == XDR_DECODE) {
+    stencil.isAsync = isAsync == 1;
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode>
+/* static */ XDRResult StencilXDR::ScopeData(
+    XDRState<mode>* xdr, ScopeStencil& stencil,
+    BaseParserScopeData*& baseScopeData) {
+  // In both decoding and encoding, stencil.kind_ is now known, and
+  // can be assumed.  This allows the encoding to write out the bytes
+  // for the specialized scope-data type without needing to encode
+  // a distinguishing prefix.
+  switch (stencil.kind_) {
+    // FunctionScope
+    case ScopeKind::Function: {
+      // Extra parentheses is for template parameters inside macro.
+      MOZ_TRY((StencilXDR::ScopeSpecificData<mode, FunctionScope>(
+          xdr, baseScopeData)));
+      break;
+    }
+
+    // VarScope
+    case ScopeKind::FunctionBodyVar: {
+      MOZ_TRY(
+          (StencilXDR::ScopeSpecificData<mode, VarScope>(xdr, baseScopeData)));
+      break;
+    }
+
+    // LexicalScope
+    case ScopeKind::Lexical:
+    case ScopeKind::SimpleCatch:
+    case ScopeKind::Catch:
+    case ScopeKind::NamedLambda:
+    case ScopeKind::StrictNamedLambda:
+    case ScopeKind::FunctionLexical:
+    case ScopeKind::ClassBody: {
+      MOZ_TRY((StencilXDR::ScopeSpecificData<mode, LexicalScope>(
+          xdr, baseScopeData)));
+      break;
+    }
+
+    // WithScope
+    case ScopeKind::With: {
+      // With scopes carry no scope data.
+      break;
+    }
+
+    // EvalScope
+    case ScopeKind::Eval:
+    case ScopeKind::StrictEval: {
+      MOZ_TRY(
+          (StencilXDR::ScopeSpecificData<mode, EvalScope>(xdr, baseScopeData)));
+      break;
+    }
+
+    // GlobalScope
+    case ScopeKind::Global:
+    case ScopeKind::NonSyntactic: {
+      MOZ_TRY((StencilXDR::ScopeSpecificData<mode, GlobalScope>(
+          xdr, baseScopeData)));
+      break;
+    }
+
+    // ModuleScope
+    case ScopeKind::Module: {
+      MOZ_TRY((StencilXDR::ScopeSpecificData<mode, ModuleScope>(
+          xdr, baseScopeData)));
+      break;
+    }
+
+    // WasmInstanceScope & WasmFunctionScope should not appear in stencils.
+    case ScopeKind::WasmInstance:
+    case ScopeKind::WasmFunction:
+    default:
+      MOZ_ASSERT_UNREACHABLE("XDR unrecognized ScopeKind.");
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode>
+/* static */ XDRResult StencilXDR::ObjLiteral(XDRState<mode>* xdr,
+                                              ObjLiteralStencil& stencil) {
+  uint8_t flags = 0;
+
+  if (mode == XDR_ENCODE) {
+    flags = stencil.flags_.serialize();
+  }
+  MOZ_TRY(xdr->codeUint8(&flags));
+  if (mode == XDR_DECODE) {
+    stencil.flags_.deserialize(flags);
+  }
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.code_));
+
+  return Ok();
+}
+
+template <XDRMode mode>
+/* static */ XDRResult StencilXDR::BigInt(XDRState<mode>* xdr,
+                                          BigIntStencil& stencil) {
+  uint64_t length;
+
+  if (mode == XDR_ENCODE) {
+    length = stencil.length_;
+  }
+
+  MOZ_TRY(xdr->codeUint64(&length));
+
+  XDRTranscodeString<char16_t> chars;
+
+  if (mode == XDR_DECODE) {
+    stencil.buf_ = xdr->cx()->template make_pod_array<char16_t>(length);
+    if (!stencil.buf_) {
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+    stencil.length_ = length;
+  }
+
+  return xdr->codeChars(stencil.buf_.get(), stencil.length_);
+}
+
+template <XDRMode mode>
+/* static */
+XDRResult StencilXDR::SharedData(XDRState<mode>* xdr,
+                                 RefPtr<SharedImmutableScriptData>& sisd) {
+  if (mode == XDR_ENCODE) {
+    MOZ_TRY(XDRImmutableScriptData<mode>(xdr, sisd->isd_));
+  } else {
+    JSContext* cx = xdr->cx();
+    UniquePtr<SharedImmutableScriptData> data(
+        SharedImmutableScriptData::create(cx));
+    if (!data) {
+      return xdr->fail(JS::TranscodeResult_Throw);
+    }
+    MOZ_TRY(XDRImmutableScriptData<mode>(xdr, data->isd_));
+    sisd = data.release();
+  }
+
+  return Ok();
+}
+
+template
+    /* static */
+    XDRResult
+    StencilXDR::SharedData(XDRState<XDR_ENCODE>* xdr,
+                           RefPtr<SharedImmutableScriptData>& sisd);
+
+template
+    /* static */
+    XDRResult
+    StencilXDR::SharedData(XDRState<XDR_DECODE>* xdr,
+                           RefPtr<SharedImmutableScriptData>& sisd);
+
+namespace js {
+
+template <XDRMode mode>
+XDRResult XDRSharedDataContainer(XDRState<mode>* xdr,
+                                 SharedDataContainer& sharedData) {
+  enum class Kind : uint8_t {
+    Single,
+    Vector,
+    Map,
+  };
+
+  uint8_t kind;
+  if (mode == XDR_ENCODE) {
+    if (sharedData.isSingle()) {
+      kind = uint8_t(Kind::Single);
+    } else if (sharedData.isVector()) {
+      kind = uint8_t(Kind::Vector);
+    } else {
+      MOZ_ASSERT(sharedData.isMap());
+      kind = uint8_t(Kind::Map);
+    }
+  }
+  MOZ_TRY(xdr->codeUint8(&kind));
+
+  switch (Kind(kind)) {
+    case Kind::Single: {
+      RefPtr<SharedImmutableScriptData> ref;
+      if (mode == XDR_ENCODE) {
+        ref = sharedData.asSingle();
+      }
+      MOZ_TRY(StencilXDR::SharedData<mode>(xdr, ref));
+      if (mode == XDR_DECODE) {
+        sharedData.setSingle(ref.forget());
+      }
+      break;
+    }
+
+    case Kind::Vector: {
+      if (mode == XDR_DECODE) {
+        if (!sharedData.initVector(xdr->cx())) {
+          return xdr->fail(JS::TranscodeResult_Throw);
+        }
+      }
+      auto& vec = *sharedData.asVector();
+      MOZ_TRY(XDRVectorInitialized(xdr, vec));
+      for (auto& entry : vec) {
+        // NOTE: There can be nullptr, even if we don't perform syntax parsing,
+        //       because of constant folding.
+        uint8_t exists;
+        if (mode == XDR_ENCODE) {
+          exists = !!entry;
+        }
+
+        MOZ_TRY(xdr->codeUint8(&exists));
+
+        if (exists) {
+          MOZ_TRY(StencilXDR::SharedData<mode>(xdr, entry));
+        }
+      }
+      break;
+    }
+
+    case Kind::Map: {
+      if (mode == XDR_DECODE) {
+        if (!sharedData.initMap(xdr->cx())) {
+          return xdr->fail(JS::TranscodeResult_Throw);
+        }
+      }
+      auto& map = *sharedData.asMap();
+      uint32_t count;
+      if (mode == XDR_ENCODE) {
+        count = map.count();
+      }
+      MOZ_TRY(xdr->codeUint32(&count));
+      if (mode == XDR_DECODE) {
+        if (!map.reserve(count)) {
+          js::ReportOutOfMemory(xdr->cx());
+          return xdr->fail(JS::TranscodeResult_Throw);
+        }
+      }
+
+      if (mode == XDR_ENCODE) {
+        for (auto iter = map.iter(); !iter.done(); iter.next()) {
+          uint32_t index = iter.get().key().index;
+          auto& data = iter.get().value();
+          MOZ_TRY(xdr->codeUint32(&index));
+          MOZ_TRY(StencilXDR::SharedData<mode>(xdr, data));
+        }
+      } else {
+        for (uint32_t i = 0; i < count; i++) {
+          ScriptIndex index;
+          MOZ_TRY(xdr->codeUint32(&index.index));
+
+          RefPtr<SharedImmutableScriptData> data;
+          MOZ_TRY(StencilXDR::SharedData<mode>(xdr, data));
+
+          if (!map.putNew(index, data)) {
+            js::ReportOutOfMemory(xdr->cx());
+            return xdr->fail(JS::TranscodeResult_Throw);
+          }
+        }
+      }
+
+      break;
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode>
+XDRResult XDRBaseCompilationStencilSpanSize(
+    XDRState<mode>* xdr, uint32_t* scriptSize, uint32_t* gcThingSize,
+    uint32_t* scopeSize, uint32_t* regExpSize, uint32_t* bigIntSize,
+    uint32_t* objLiteralSize) {
+  // Compress the series of span sizes, to avoid consuming extra space for
+  // unused/small span sizes.
+  // There will be align32 shortly after this section, so try to make the
+  // padding smaller.
+
+  enum XDRSpanSizeKind {
+    // The scriptSize, gcThingSize, and scopeSize fit in 1 byte, and others have
+    // a value of 0. The entire section takes 4 bytes, and expect no padding.
+    Base8Kind,
+
+    // All of the size values can fit in 1 byte each. The entire section takes 7
+    // bytes, and expect 1 byte padding.
+    All8Kind,
+
+    // Other. This case is less than 1% in practice and indicates the stencil is
+    // already quite large, so don't try to compress. Expect 3 bytes padding for
+    // `sizeKind`.
+    All32Kind,
+  };
+
+  uint8_t sizeKind = All32Kind;
+  if (mode == XDR_ENCODE) {
+    uint32_t mask_base = (*scriptSize) | (*gcThingSize) | (*scopeSize);
+    uint32_t mask_ext = (*regExpSize) | (*bigIntSize) | (*objLiteralSize);
+
+    if (mask_base <= 0xff) {
+      if (mask_ext == 0x00) {
+        sizeKind = Base8Kind;
+      } else if (mask_ext <= 0xFF) {
+        sizeKind = All8Kind;
+      }
+    }
+  }
+  MOZ_TRY(xdr->codeUint8(&sizeKind));
+
+  if (sizeKind == All32Kind) {
+    MOZ_TRY(xdr->codeUint32(scriptSize));
+    MOZ_TRY(xdr->codeUint32(gcThingSize));
+    MOZ_TRY(xdr->codeUint32(scopeSize));
+    MOZ_TRY(xdr->codeUint32(regExpSize));
+    MOZ_TRY(xdr->codeUint32(bigIntSize));
+    MOZ_TRY(xdr->codeUint32(objLiteralSize));
+  } else {
+    uint8_t scriptSize8 = 0;
+    uint8_t gcThingSize8 = 0;
+    uint8_t scopeSize8 = 0;
+    uint8_t regExpSize8 = 0;
+    uint8_t bigIntSize8 = 0;
+    uint8_t objLiteralSize8 = 0;
+
+    if (mode == XDR_ENCODE) {
+      scriptSize8 = uint8_t(*scriptSize);
+      gcThingSize8 = uint8_t(*gcThingSize);
+      scopeSize8 = uint8_t(*scopeSize);
+      regExpSize8 = uint8_t(*regExpSize);
+      bigIntSize8 = uint8_t(*bigIntSize);
+      objLiteralSize8 = uint8_t(*objLiteralSize);
+    }
+
+    MOZ_TRY(xdr->codeUint8(&scriptSize8));
+    MOZ_TRY(xdr->codeUint8(&gcThingSize8));
+    MOZ_TRY(xdr->codeUint8(&scopeSize8));
+
+    if (sizeKind == All8Kind) {
+      MOZ_TRY(xdr->codeUint8(&regExpSize8));
+      MOZ_TRY(xdr->codeUint8(&bigIntSize8));
+      MOZ_TRY(xdr->codeUint8(&objLiteralSize8));
+    } else {
+      MOZ_ASSERT(regExpSize8 == 0);
+      MOZ_ASSERT(bigIntSize8 == 0);
+      MOZ_ASSERT(objLiteralSize8 == 0);
+    }
+
+    if (mode == XDR_DECODE) {
+      *scriptSize = scriptSize8;
+      *gcThingSize = gcThingSize8;
+      *scopeSize = scopeSize8;
+      *regExpSize = regExpSize8;
+      *bigIntSize = bigIntSize8;
+      *objLiteralSize = objLiteralSize8;
+    }
+  }
+
+  return Ok();
+}
+
+template <XDRMode mode>
+XDRResult XDRBaseCompilationStencil(XDRState<mode>* xdr,
+                                    BaseCompilationStencil& stencil) {
+  MOZ_TRY(xdr->codeUint32(&stencil.functionKey));
+
+  uint32_t scriptSize, gcThingSize, scopeSize;
+  uint32_t regExpSize, bigIntSize, objLiteralSize;
+  if (mode == XDR_ENCODE) {
+    scriptSize = stencil.scriptData.size();
+    gcThingSize = stencil.gcThingData.size();
+    scopeSize = stencil.scopeData.size();
+    MOZ_ASSERT(scopeSize == stencil.scopeNames.size());
+
+    regExpSize = stencil.regExpData.size();
+    bigIntSize = stencil.bigIntData.length();
+    objLiteralSize = stencil.objLiteralData.length();
+  }
+  MOZ_TRY(XDRBaseCompilationStencilSpanSize(xdr, &scriptSize, &gcThingSize,
+                                            &scopeSize, &regExpSize,
+                                            &bigIntSize, &objLiteralSize));
+
+  // All of the vector-indexed data elements referenced by the
+  // main script tree must be materialized first.
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.scopeData, scopeSize));
+  MOZ_TRY(XDRSpanInitialized(xdr, stencil.scopeNames, scopeSize));
+  MOZ_ASSERT(stencil.scopeData.size() == stencil.scopeNames.size());
+  for (uint32_t i = 0; i < scopeSize; i++) {
+    MOZ_TRY(StencilXDR::ScopeData(xdr, stencil.scopeData[i],
+                                  stencil.scopeNames[i]));
+  }
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.regExpData, regExpSize));
+
+  MOZ_TRY(XDRVectorInitialized(xdr, stencil.bigIntData, bigIntSize));
+  for (auto& entry : stencil.bigIntData) {
+    MOZ_TRY(StencilXDR::BigInt(xdr, entry));
+  }
+
+  MOZ_TRY(XDRVectorInitialized(xdr, stencil.objLiteralData, objLiteralSize));
+  for (auto& entry : stencil.objLiteralData) {
+    MOZ_TRY(StencilXDR::ObjLiteral(xdr, entry));
+  }
+
+  MOZ_TRY(XDRSharedDataContainer(xdr, stencil.sharedData));
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.gcThingData, gcThingSize));
+
+  // Now serialize the vector of ScriptStencils.
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.scriptData, scriptSize));
+
+  return Ok();
+}
+
+template XDRResult XDRBaseCompilationStencil(XDRState<XDR_ENCODE>* xdr,
+                                             BaseCompilationStencil& stencil);
+
+template XDRResult XDRBaseCompilationStencil(XDRState<XDR_DECODE>* xdr,
+                                             BaseCompilationStencil& stencil);
+
+template <XDRMode mode>
+XDRResult XDRCompilationStencil(XDRState<mode>* xdr,
+                                CompilationStencil& stencil) {
+  if (!stencil.asmJS.empty()) {
+    return xdr->fail(JS::TranscodeResult_Failure_AsmJSNotSupported);
+  }
+
+  MOZ_TRY(XDRBaseCompilationStencil(xdr, stencil));
+
+  MOZ_TRY(XDRSpanContent(xdr, stencil.scriptExtra));
+
+  // We don't support coding non-initial CompilationStencil.
+  MOZ_ASSERT(stencil.isInitialStencil());
+
+  if (stencil.scriptExtra[CompilationStencil::TopLevelIndex].isModule()) {
+    if (mode == XDR_DECODE) {
+      stencil.moduleMetadata.emplace();
+    }
+
+    MOZ_TRY(XDRStencilModuleMetadata(xdr, *stencil.moduleMetadata));
+  }
+
+  return Ok();
+}
+
+template XDRResult XDRCompilationStencil(XDRState<XDR_ENCODE>* xdr,
+                                         CompilationStencil& stencil);
+
+template XDRResult XDRCompilationStencil(XDRState<XDR_DECODE>* xdr,
+                                         CompilationStencil& stencil);
+
+}  // namespace js