Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 658 insertions, 0 deletions

diff --git a/js/src/wasm/WasmGcObject.cpp b/js/src/wasm/WasmGcObject.cpp
new file mode 100644
index 0000000000..bcab5fe275
--- /dev/null
+++ b/js/src/wasm/WasmGcObject.cpp
@@ -0,0 +1,658 @@
+/* -*- 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 "wasm/WasmGcObject-inl.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Casting.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/DebugOnly.h"
+
+#include <algorithm>
+
+#include "gc/Marking.h"
+#include "js/CharacterEncoding.h"
+#include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
+#include "js/PropertySpec.h"
+#include "js/ScalarType.h"  // js::Scalar::Type
+#include "js/Vector.h"
+#include "util/StringBuffer.h"
+#include "vm/GlobalObject.h"
+#include "vm/JSFunction.h"
+#include "vm/JSObject.h"
+#include "vm/PlainObject.h"  // js::PlainObject
+#include "vm/PropertyResult.h"
+#include "vm/Realm.h"
+#include "vm/SelfHosting.h"
+#include "vm/StringType.h"
+#include "vm/TypedArrayObject.h"
+#include "vm/Uint8Clamped.h"
+
+#include "gc/GCContext-inl.h"  // GCContext::removeCellMemory
+#include "gc/ObjectKind-inl.h"
+#include "vm/JSContext-inl.h"
+
+using mozilla::AssertedCast;
+using mozilla::CheckedUint32;
+using mozilla::IsPowerOfTwo;
+using mozilla::PodCopy;
+using mozilla::PointerRangeSize;
+
+using namespace js;
+using namespace wasm;
+
+// [SMDOC] Management of OOL storage areas for Wasm{Array,Struct}Object.
+//
+// WasmArrayObject always has its payload data stored in a block the C++-heap,
+// which is pointed to from the WasmArrayObject.  The same is true for
+// WasmStructObject in the case where the fields cannot fit in the object
+// itself.  These C++ blocks are in some places referred to as "trailer blocks".
+//
+// The presence of trailer blocks complicates the use of generational GC (that
+// is, Nursery allocation) of Wasm{Array,Struct}Object.  In particular:
+//
+// (1) For objects which do not get tenured at minor collection, there must be
+//     a way to free the associated trailer, but there is no way to visit
+//     non-tenured blocks during minor collection.
+//
+// (2) Even if (1) were solved, calling js_malloc/js_free for every object
+//     creation-death cycle is expensive, possibly around 400 machine
+//     instructions, and we expressly want to avoid that in a generational GC
+//     scenario.
+//
+// The following scheme is therefore employed.
+//
+// (a) gc::Nursery maintains a pool of available C++-heap-allocated blocks --
+//     a js::MallocedBlockCache -- and the intention is that trailers are
+//     allocated from this pool and freed back into it whenever possible.
+//
+// (b) WasmArrayObject::createArrayNonEmpty and
+//     WasmStructObject::createStructOOL always request trailer allocation
+//     from the nursery's cache (a).  If the cache cannot honour the request
+//     directly it will allocate directly from js_malloc; we hope this happens
+//     only infrequently.
+//
+// (c) The allocated block is returned as a js::PointerAndUint7, a pair that
+//     holds the trailer block pointer and an auxiliary tag that the
+//     js::MallocedBlockCache needs to see when the block is freed.
+//
+//     The raw trailer block pointer (a `void*`) is stored in the
+//     Wasm{Array,Struct}Object OOL data field.  These objects are not aware
+//     of and do not interact with js::PointerAndUint7, and nor does any
+//     JIT-generated code.
+//
+// (d) Still in WasmArrayObject::createArrayNonEmpty and
+//     WasmStructObject::createStructOOL, if the object was allocated in the
+//     nursery, then the resulting js::PointerAndUint7 is "registered" with
+//     the nursery by handing it to Nursery::registerTrailer.
+//
+// (e) When a minor collection happens (Nursery::doCollection), we are
+//     notified of objects that are moved by calls to the ::obj_moved methods
+//     in this file.  For those objects that have been tenured, the raw
+//     trailer pointer is "unregistered" with the nursery by handing it to
+//     Nursery::unregisterTrailer.
+//
+// (f) Still during minor collection: The nursery now knows both the set of
+//     trailer blocks added, and those removed because the corresponding
+//     object has been tenured.  The difference between these two sets (that
+//     is, `added - removed`) is the set of trailer blocks corresponding to
+//     blocks that didn't get tenured.  That set is computed and freed (back
+//     to the nursery's js::MallocedBlockCache) by Nursery::freeTrailerBlocks.
+//
+// (g) At the end of minor collection, the added and removed sets are made
+//     empty, and the cycle begins again.
+//
+// (h) Also at the end of minor collection, a call to
+//     `mallocedBlockCache_.preen` hands a few blocks in the cache back to
+//     js_free.  This mechanism exists so as to ensure that unused blocks do
+//     not remain in the cache indefinitely.
+//
+// (i) In order that the tenured heap is collected "often enough" in the case
+//     where the trailer blocks are large (relative to their owning objects),
+//     we have to tell the tenured heap about the sizes of trailers entering
+//     and leaving it.  This is done via calls to AddCellMemory and
+//     GCContext::removeCellMemory.
+//
+// (j) For objects that got tenured, we are eventually notified of their death
+//     by a call to the ::obj_finalize methods below.  At that point we hand
+//     their block pointers to js_free.
+//
+// (k) When the nursery is eventually destroyed, all blocks in its block cache
+//     are handed to js_free.  Hence, at process exit, provided all nurseries
+//     are first collected and then their destructors run, no C++ heap blocks
+//     are leaked.
+//
+// As a result of this scheme, trailer blocks associated with what we hope is
+// the frequent case -- objects that are allocated but never make it out of
+// the nursery -- are cycled through the nursery's block cache.
+//
+// Trailers associated with tenured blocks cannot participate though; they are
+// always returned to js_free.  Making them participate is difficult: it would
+// require changing their owning object's OOL data pointer to be a
+// js::PointerAndUint7 rather than a raw `void*`, so that then the blocks
+// could be released to the cache in the ::obj_finalize methods.  This would
+// however require changes in the generated code for array element and OOL
+// struct element accesses.
+//
+// It would also lead to threading difficulties, because the ::obj_finalize
+// methods run on a background thread, whilst allocation from the cache
+// happens on the main thread, but the MallocedBlockCache is not thread safe.
+// Making it thread safe would entail adding a locking mechanism, but that's
+// potentially slow and so negates the point of having a cache at all.
+//
+// Here's a short summary of the trailer block life cycle:
+//
+// * allocated:
+//
+//   - in WasmArrayObject::createArrayNonEmpty
+//     and WasmStructObject::createStructOOL
+//
+//   - by calling the nursery's MallocBlockCache alloc method
+//
+// * deallocated:
+//
+//   - for non-tenured objects, in the collector itself,
+//     in Nursery::doCollection calling Nursery::freeTrailerBlocks,
+//     releasing to the nursery's block cache
+//
+//   - for tenured objects, in the ::obj_finalize methods, releasing directly
+//     to js_free
+//
+// If this seems confusing ("why is it ok to allocate from the cache but
+// release to js_free?"), remember that the cache holds blocks previously
+// obtained from js_malloc but which are *not* currently in use.  Hence it is
+// fine to give them back to js_free; that just makes the cache a bit emptier
+// but has no effect on correctness.
+
+//=========================================================================
+// WasmGcObject
+
+const ObjectOps WasmGcObject::objectOps_ = {
+    WasmGcObject::obj_lookupProperty,            // lookupProperty
+    WasmGcObject::obj_defineProperty,            // defineProperty
+    WasmGcObject::obj_hasProperty,               // hasProperty
+    WasmGcObject::obj_getProperty,               // getProperty
+    WasmGcObject::obj_setProperty,               // setProperty
+    WasmGcObject::obj_getOwnPropertyDescriptor,  // getOwnPropertyDescriptor
+    WasmGcObject::obj_deleteProperty,            // deleteProperty
+    nullptr,                                     // getElements
+    nullptr,                                     // funToString
+};
+
+/* static */
+bool WasmGcObject::obj_lookupProperty(JSContext* cx, HandleObject obj,
+                                      HandleId id, MutableHandleObject objp,
+                                      PropertyResult* propp) {
+  objp.set(nullptr);
+  propp->setNotFound();
+  return true;
+}
+
+bool WasmGcObject::obj_defineProperty(JSContext* cx, HandleObject obj,
+                                      HandleId id,
+                                      Handle<PropertyDescriptor> desc,
+                                      ObjectOpResult& result) {
+  result.failReadOnly();
+  return true;
+}
+
+bool WasmGcObject::obj_hasProperty(JSContext* cx, HandleObject obj, HandleId id,
+                                   bool* foundp) {
+  *foundp = false;
+  return true;
+}
+
+bool WasmGcObject::obj_getProperty(JSContext* cx, HandleObject obj,
+                                   HandleValue receiver, HandleId id,
+                                   MutableHandleValue vp) {
+  vp.setUndefined();
+  return true;
+}
+
+bool WasmGcObject::obj_setProperty(JSContext* cx, HandleObject obj, HandleId id,
+                                   HandleValue v, HandleValue receiver,
+                                   ObjectOpResult& result) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                            JSMSG_WASM_MODIFIED_GC_OBJECT);
+  return false;
+}
+
+bool WasmGcObject::obj_getOwnPropertyDescriptor(
+    JSContext* cx, HandleObject obj, HandleId id,
+    MutableHandle<mozilla::Maybe<PropertyDescriptor>> desc) {
+  desc.reset();
+  return true;
+}
+
+bool WasmGcObject::obj_deleteProperty(JSContext* cx, HandleObject obj,
+                                      HandleId id, ObjectOpResult& result) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                            JSMSG_WASM_MODIFIED_GC_OBJECT);
+  return false;
+}
+
+bool WasmGcObject::lookUpProperty(JSContext* cx, Handle<WasmGcObject*> obj,
+                                  jsid id, WasmGcObject::PropOffset* offset,
+                                  StorageType* type) {
+  switch (obj->kind()) {
+    case wasm::TypeDefKind::Struct: {
+      const auto& structType = obj->typeDef().structType();
+      uint32_t index;
+      if (!IdIsIndex(id, &index)) {
+        return false;
+      }
+      if (index >= structType.fields_.length()) {
+        JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                                 JSMSG_WASM_OUT_OF_BOUNDS);
+        return false;
+      }
+      const StructField& field = structType.fields_[index];
+      offset->set(field.offset);
+      *type = field.type;
+      return true;
+    }
+    case wasm::TypeDefKind::Array: {
+      const auto& arrayType = obj->typeDef().arrayType();
+
+      uint32_t index;
+      if (!IdIsIndex(id, &index)) {
+        return false;
+      }
+      uint32_t numElements = obj->as<WasmArrayObject>().numElements_;
+      if (index >= numElements) {
+        return false;
+      }
+      uint64_t scaledIndex =
+          uint64_t(index) * uint64_t(arrayType.elementType_.size());
+      if (scaledIndex >= uint64_t(UINT32_MAX)) {
+        // It's unrepresentable as an WasmGcObject::PropOffset.  Give up.
+        return false;
+      }
+      offset->set(uint32_t(scaledIndex));
+      *type = arrayType.elementType_;
+      return true;
+    }
+    default:
+      MOZ_ASSERT_UNREACHABLE();
+      return false;
+  }
+}
+
+bool WasmGcObject::loadValue(JSContext* cx, Handle<WasmGcObject*> obj, jsid id,
+                             MutableHandleValue vp) {
+  WasmGcObject::PropOffset offset;
+  StorageType type;
+  if (!lookUpProperty(cx, obj, id, &offset, &type)) {
+    return false;
+  }
+
+  // Temporary hack, (ref T) is not exposable to JS yet but some tests would
+  // like to access it so we erase (ref T) with eqref when loading. This is
+  // safe as (ref T) <: eqref and we're not in the writing case where we
+  // would need to perform a type check.
+  if (type.isTypeRef()) {
+    type = RefType::fromTypeCode(TypeCode::EqRef, true);
+  }
+
+  if (!type.isExposable()) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                             JSMSG_WASM_BAD_VAL_TYPE);
+    return false;
+  }
+
+  if (obj->is<WasmStructObject>()) {
+    // `offset` is the field offset, without regard to the in/out-line split.
+    // That is handled by the call to `fieldOffsetToAddress`.
+    WasmStructObject& structObj = obj->as<WasmStructObject>();
+    // Ensure no out-of-range access possible
+    MOZ_RELEASE_ASSERT(structObj.kind() == TypeDefKind::Struct);
+    MOZ_RELEASE_ASSERT(offset.get() + type.size() <=
+                       structObj.typeDef().structType().size_);
+    return ToJSValue(cx, structObj.fieldOffsetToAddress(type, offset.get()),
+                     type, vp);
+  }
+
+  MOZ_ASSERT(obj->is<WasmArrayObject>());
+  const WasmArrayObject& arrayObj = obj->as<WasmArrayObject>();
+  return ToJSValue(cx, arrayObj.data_ + offset.get(), type, vp);
+}
+
+bool WasmGcObject::isRuntimeSubtypeOf(
+    const wasm::TypeDef* parentTypeDef) const {
+  return TypeDef::isSubTypeOf(&typeDef(), parentTypeDef);
+}
+
+bool WasmGcObject::obj_newEnumerate(JSContext* cx, HandleObject obj,
+                                    MutableHandleIdVector properties,
+                                    bool enumerableOnly) {
+  return true;
+}
+
+static void WriteValTo(const Val& val, StorageType ty, void* dest) {
+  switch (ty.kind()) {
+    case StorageType::I8:
+      *((uint8_t*)dest) = val.i32();
+      break;
+    case StorageType::I16:
+      *((uint16_t*)dest) = val.i32();
+      break;
+    case StorageType::I32:
+      *((uint32_t*)dest) = val.i32();
+      break;
+    case StorageType::I64:
+      *((uint64_t*)dest) = val.i64();
+      break;
+    case StorageType::F32:
+      *((float*)dest) = val.f32();
+      break;
+    case StorageType::F64:
+      *((double*)dest) = val.f64();
+      break;
+    case StorageType::V128:
+      *((V128*)dest) = val.v128();
+      break;
+    case StorageType::Ref:
+      *((GCPtr<AnyRef>*)dest) = val.ref();
+      break;
+  }
+}
+
+//=========================================================================
+// WasmArrayObject
+
+/* static */
+void WasmArrayObject::obj_trace(JSTracer* trc, JSObject* object) {
+  WasmArrayObject& arrayObj = object->as<WasmArrayObject>();
+  uint8_t* data = arrayObj.data_;
+
+  const auto& typeDef = arrayObj.typeDef();
+  const auto& arrayType = typeDef.arrayType();
+  if (!arrayType.elementType_.isRefRepr()) {
+    return;
+  }
+
+  uint32_t numElements = arrayObj.numElements_;
+  uint32_t elemSize = arrayType.elementType_.size();
+  for (uint32_t i = 0; i < numElements; i++) {
+    AnyRef* elementPtr = reinterpret_cast<AnyRef*>(data + i * elemSize);
+    TraceManuallyBarrieredEdge(trc, elementPtr, "wasm-array-element");
+  }
+}
+
+/* static */
+void WasmArrayObject::obj_finalize(JS::GCContext* gcx, JSObject* object) {
+  // This method, and also ::obj_moved and the WasmStructObject equivalents,
+  // assumes that the object's TypeDef (as reachable via its SuperTypeVector*)
+  // stays alive at least as long as the object.
+  WasmArrayObject& arrayObj = object->as<WasmArrayObject>();
+  if (!arrayObj.isDataInline()) {
+    // Free the trailer block.  Unfortunately we can't give it back to the
+    // malloc'd block cache because we might not be running on the main
+    // thread, and the cache isn't thread-safe.
+    js_free(arrayObj.dataHeader());
+    // And tell the tenured-heap accounting machinery that the trailer has
+    // been freed.
+    const TypeDef& typeDef = arrayObj.typeDef();
+    MOZ_ASSERT(typeDef.isArrayType());
+    size_t trailerSize = calcStorageBytes(
+        typeDef.arrayType().elementType_.size(), arrayObj.numElements_);
+    // Ensured by WasmArrayObject::createArrayNonEmpty.
+    MOZ_RELEASE_ASSERT(trailerSize <= size_t(MaxArrayPayloadBytes));
+    gcx->removeCellMemory(&arrayObj, trailerSize + TrailerBlockOverhead,
+                          MemoryUse::WasmTrailerBlock);
+    // For safety
+    arrayObj.data_ = nullptr;
+  }
+}
+
+/* static */
+size_t WasmArrayObject::obj_moved(JSObject* obj, JSObject* old) {
+  MOZ_ASSERT(!IsInsideNursery(obj));
+
+  // Moving inline arrays requires us to update the data pointer.
+  WasmArrayObject& arrayObj = obj->as<WasmArrayObject>();
+  WasmArrayObject& oldArrayObj = old->as<WasmArrayObject>();
+  if (oldArrayObj.isDataInline()) {
+    // The old array had inline storage, which has been copied.
+    // Fix up the data pointer on the new array to point to it.
+    arrayObj.data_ = WasmArrayObject::addressOfInlineData(&arrayObj);
+  }
+  MOZ_ASSERT(arrayObj.isDataInline() == oldArrayObj.isDataInline());
+
+  if (IsInsideNursery(old)) {
+    // It's been tenured.
+    MOZ_ASSERT(obj->isTenured());
+    if (!arrayObj.isDataInline()) {
+      // Tell the nursery that the trailer is no longer associated with an
+      // object in the nursery, since the object has been moved to the tenured
+      // heap.
+      Nursery& nursery = obj->runtimeFromMainThread()->gc.nursery();
+      nursery.unregisterTrailer(arrayObj.dataHeader());
+      // Tell the tenured-heap accounting machinery that the trailer is now
+      // associated with the tenured heap.
+      const TypeDef& typeDef = arrayObj.typeDef();
+      MOZ_ASSERT(typeDef.isArrayType());
+      size_t trailerSize = calcStorageBytes(
+          typeDef.arrayType().elementType_.size(), arrayObj.numElements_);
+      // Ensured by WasmArrayObject::createArrayOOL.
+      MOZ_RELEASE_ASSERT(trailerSize <= size_t(MaxArrayPayloadBytes));
+      AddCellMemory(&arrayObj, trailerSize + TrailerBlockOverhead,
+                    MemoryUse::WasmTrailerBlock);
+    }
+  }
+
+  return 0;
+}
+
+void WasmArrayObject::storeVal(const Val& val, uint32_t itemIndex) {
+  const ArrayType& arrayType = typeDef().arrayType();
+  size_t elementSize = arrayType.elementType_.size();
+  MOZ_ASSERT(itemIndex < numElements_);
+  uint8_t* data = data_ + elementSize * itemIndex;
+  WriteValTo(val, arrayType.elementType_, data);
+}
+
+void WasmArrayObject::fillVal(const Val& val, uint32_t itemIndex,
+                              uint32_t len) {
+  const ArrayType& arrayType = typeDef().arrayType();
+  size_t elementSize = arrayType.elementType_.size();
+  uint8_t* data = data_ + elementSize * itemIndex;
+  MOZ_ASSERT(itemIndex <= numElements_ && len <= numElements_ - itemIndex);
+  for (uint32_t i = 0; i < len; i++) {
+    WriteValTo(val, arrayType.elementType_, data);
+    data += elementSize;
+  }
+}
+
+static const JSClassOps WasmArrayObjectClassOps = {
+    nullptr, /* addProperty */
+    nullptr, /* delProperty */
+    nullptr, /* enumerate   */
+    WasmGcObject::obj_newEnumerate,
+    nullptr,                       /* resolve     */
+    nullptr,                       /* mayResolve  */
+    WasmArrayObject::obj_finalize, /* finalize    */
+    nullptr,                       /* call        */
+    nullptr,                       /* construct   */
+    WasmArrayObject::obj_trace,
+};
+static const ClassExtension WasmArrayObjectClassExt = {
+    WasmArrayObject::obj_moved /* objectMovedOp */
+};
+const JSClass WasmArrayObject::class_ = {
+    "WasmArrayObject",
+    JSClass::NON_NATIVE | JSCLASS_DELAY_METADATA_BUILDER |
+        JSCLASS_BACKGROUND_FINALIZE | JSCLASS_SKIP_NURSERY_FINALIZE,
+    &WasmArrayObjectClassOps,
+    JS_NULL_CLASS_SPEC,
+    &WasmArrayObjectClassExt,
+    &WasmGcObject::objectOps_};
+
+//=========================================================================
+// WasmStructObject
+
+/* static */
+const JSClass* js::WasmStructObject::classForTypeDef(
+    const wasm::TypeDef* typeDef) {
+  MOZ_ASSERT(typeDef->kind() == wasm::TypeDefKind::Struct);
+  size_t nbytes = typeDef->structType().size_;
+  return nbytes > WasmStructObject_MaxInlineBytes
+             ? &WasmStructObject::classOutline_
+             : &WasmStructObject::classInline_;
+}
+
+/* static */
+js::gc::AllocKind js::WasmStructObject::allocKindForTypeDef(
+    const wasm::TypeDef* typeDef) {
+  MOZ_ASSERT(typeDef->kind() == wasm::TypeDefKind::Struct);
+  size_t nbytes = typeDef->structType().size_;
+
+  // `nbytes` is the total required size for all struct fields, including
+  // padding.  What we need is the size of resulting WasmStructObject,
+  // ignoring any space used for out-of-line data.  First, restrict `nbytes`
+  // to cover just the inline data.
+  if (nbytes > WasmStructObject_MaxInlineBytes) {
+    nbytes = WasmStructObject_MaxInlineBytes;
+  }
+
+  // Now convert it to size of the WasmStructObject as a whole.
+  nbytes = sizeOfIncludingInlineData(nbytes);
+
+  return gc::GetGCObjectKindForBytes(nbytes);
+}
+
+/* static */
+void WasmStructObject::obj_trace(JSTracer* trc, JSObject* object) {
+  WasmStructObject& structObj = object->as<WasmStructObject>();
+
+  const auto& structType = structObj.typeDef().structType();
+  for (uint32_t offset : structType.inlineTraceOffsets_) {
+    AnyRef* fieldPtr =
+        reinterpret_cast<AnyRef*>(structObj.inlineData() + offset);
+    TraceManuallyBarrieredEdge(trc, fieldPtr, "wasm-struct-field");
+  }
+  for (uint32_t offset : structType.outlineTraceOffsets_) {
+    AnyRef* fieldPtr =
+        reinterpret_cast<AnyRef*>(structObj.outlineData_ + offset);
+    TraceManuallyBarrieredEdge(trc, fieldPtr, "wasm-struct-field");
+  }
+}
+
+/* static */
+void WasmStructObject::obj_finalize(JS::GCContext* gcx, JSObject* object) {
+  // See corresponding comments in WasmArrayObject::obj_finalize.
+  WasmStructObject& structObj = object->as<WasmStructObject>();
+  if (structObj.outlineData_) {
+    js_free(structObj.outlineData_);
+    const TypeDef& typeDef = structObj.typeDef();
+    MOZ_ASSERT(typeDef.isStructType());
+    uint32_t totalBytes = typeDef.structType().size_;
+    uint32_t inlineBytes, outlineBytes;
+    WasmStructObject::getDataByteSizes(totalBytes, &inlineBytes, &outlineBytes);
+    MOZ_ASSERT(inlineBytes == WasmStructObject_MaxInlineBytes);
+    MOZ_ASSERT(outlineBytes > 0);
+    gcx->removeCellMemory(&structObj, outlineBytes + TrailerBlockOverhead,
+                          MemoryUse::WasmTrailerBlock);
+    structObj.outlineData_ = nullptr;
+  }
+}
+
+/* static */
+size_t WasmStructObject::obj_moved(JSObject* obj, JSObject* old) {
+  // See also, corresponding comments in WasmArrayObject::obj_moved.
+  MOZ_ASSERT(!IsInsideNursery(obj));
+  if (IsInsideNursery(old)) {
+    // It's been tenured.
+    MOZ_ASSERT(obj->isTenured());
+    WasmStructObject& structObj = obj->as<WasmStructObject>();
+    // WasmStructObject::classForTypeDef ensures we only get called for
+    // structs with OOL data.  Hence:
+    MOZ_ASSERT(structObj.outlineData_);
+    Nursery& nursery = obj->runtimeFromMainThread()->gc.nursery();
+    nursery.unregisterTrailer(structObj.outlineData_);
+    const TypeDef& typeDef = structObj.typeDef();
+    MOZ_ASSERT(typeDef.isStructType());
+    uint32_t totalBytes = typeDef.structType().size_;
+    uint32_t inlineBytes, outlineBytes;
+    WasmStructObject::getDataByteSizes(totalBytes, &inlineBytes, &outlineBytes);
+    MOZ_ASSERT(inlineBytes == WasmStructObject_MaxInlineBytes);
+    MOZ_ASSERT(outlineBytes > 0);
+    AddCellMemory(&structObj, outlineBytes + TrailerBlockOverhead,
+                  MemoryUse::WasmTrailerBlock);
+  }
+  return 0;
+}
+
+void WasmStructObject::storeVal(const Val& val, uint32_t fieldIndex) {
+  const StructType& structType = typeDef().structType();
+  StorageType fieldType = structType.fields_[fieldIndex].type;
+  uint32_t fieldOffset = structType.fields_[fieldIndex].offset;
+
+  MOZ_ASSERT(fieldIndex < structType.fields_.length());
+  bool areaIsOutline;
+  uint32_t areaOffset;
+  fieldOffsetToAreaAndOffset(fieldType, fieldOffset, &areaIsOutline,
+                             &areaOffset);
+
+  uint8_t* data;
+  if (areaIsOutline) {
+    data = outlineData_ + areaOffset;
+  } else {
+    data = inlineData() + areaOffset;
+  }
+
+  WriteValTo(val, fieldType, data);
+}
+
+static const JSClassOps WasmStructObjectOutlineClassOps = {
+    nullptr, /* addProperty */
+    nullptr, /* delProperty */
+    nullptr, /* enumerate   */
+    WasmGcObject::obj_newEnumerate,
+    nullptr,                        /* resolve     */
+    nullptr,                        /* mayResolve  */
+    WasmStructObject::obj_finalize, /* finalize    */
+    nullptr,                        /* call        */
+    nullptr,                        /* construct   */
+    WasmStructObject::obj_trace,
+};
+static const ClassExtension WasmStructObjectOutlineClassExt = {
+    WasmStructObject::obj_moved /* objectMovedOp */
+};
+const JSClass WasmStructObject::classOutline_ = {
+    "WasmStructObject",
+    JSClass::NON_NATIVE | JSCLASS_DELAY_METADATA_BUILDER |
+        JSCLASS_BACKGROUND_FINALIZE | JSCLASS_SKIP_NURSERY_FINALIZE,
+    &WasmStructObjectOutlineClassOps,
+    JS_NULL_CLASS_SPEC,
+    &WasmStructObjectOutlineClassExt,
+    &WasmGcObject::objectOps_};
+
+// Structs that only have inline data get a different class without a
+// finalizer. This class should otherwise be identical to the class for
+// structs with outline data.
+static const JSClassOps WasmStructObjectInlineClassOps = {
+    nullptr, /* addProperty */
+    nullptr, /* delProperty */
+    nullptr, /* enumerate   */
+    WasmGcObject::obj_newEnumerate,
+    nullptr, /* resolve     */
+    nullptr, /* mayResolve  */
+    nullptr, /* finalize    */
+    nullptr, /* call        */
+    nullptr, /* construct   */
+    WasmStructObject::obj_trace,
+};
+static const ClassExtension WasmStructObjectInlineClassExt = {
+    nullptr /* objectMovedOp */
+};
+const JSClass WasmStructObject::classInline_ = {
+    "WasmStructObject",
+    JSClass::NON_NATIVE | JSCLASS_DELAY_METADATA_BUILDER,
+    &WasmStructObjectInlineClassOps,
+    JS_NULL_CLASS_SPEC,
+    &WasmStructObjectInlineClassExt,
+    &WasmGcObject::objectOps_};