[wasm][stack-switching] Support rejected promises

If the returned promise rejects, we switch to the suspender's stack and
throw the value.
Re-purpose the WasmOnFulfilled data to also represent the rejecting
case and rename it to WasmResumeData.

R=ahaas@chromium.org
CC=fgm@chromium.org

Bug: v8:12191
Change-Id: I91a301c3c6d9d243efbfabe7263555e11f0d9277
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3706606
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81325}

src/builtins/arm/builtins-arm.cc

@@ -2784,6 +2784,11 @@ void Builtins::Generate_WasmResume(MacroAssembler* masm) {
   __ Trap();
 }
 
+void Builtins::Generate_WasmReject(MacroAssembler* masm) {
+  // TODO(v8:12191): Implement for this platform.
+  __ Trap();
+}
+
 void Builtins::Generate_WasmOnStackReplace(MacroAssembler* masm) {
   // Only needed on x64.
   __ Trap();

src/builtins/arm64/builtins-arm64.cc

@@ -3175,6 +3175,11 @@ void Builtins::Generate_WasmResume(MacroAssembler* masm) {
   __ Trap();
 }
 
+void Builtins::Generate_WasmReject(MacroAssembler* masm) {
+  // TODO(v8:12191): Implement for this platform.
+  __ Trap();
+}
+
 void Builtins::Generate_WasmOnStackReplace(MacroAssembler* masm) {
   // Only needed on x64.
   __ Trap();

src/builtins/builtins-definitions.h

@@ -966,6 +966,7 @@ namespace internal {
   IF_WASM(ASM, WasmReturnPromiseOnSuspend, WasmDummy)                          \
   IF_WASM(ASM, WasmSuspend, WasmSuspend)                                       \
   IF_WASM(ASM, WasmResume, WasmDummy)                                          \
+  IF_WASM(ASM, WasmReject, WasmDummy)                                          \
   IF_WASM(ASM, WasmCompileLazy, WasmDummy)                                     \
   IF_WASM(ASM, WasmDebugBreak, WasmDummy)                                      \
   IF_WASM(ASM, WasmOnStackReplace, WasmDummy)                                  \

src/builtins/ia32/builtins-ia32.cc

@@ -3032,6 +3032,11 @@ void Builtins::Generate_WasmResume(MacroAssembler* masm) {
   __ Trap();
 }
 
+void Builtins::Generate_WasmReject(MacroAssembler* masm) {
+  // TODO(v8:12191): Implement for this platform.
+  __ Trap();
+}
+
 void Builtins::Generate_WasmOnStackReplace(MacroAssembler* masm) {
   // Only needed on x64.
   __ Trap();

src/builtins/x64/builtins-x64.cc

@@ -4116,8 +4116,12 @@ void Builtins::Generate_WasmSuspend(MacroAssembler* masm) {
   __ ret(0);
 }
 
-// Resume the suspender stored in the closure.
-void Builtins::Generate_WasmResume(MacroAssembler* masm) {
+namespace {
+// Resume the suspender stored in the closure. We generate two variants of this
+// builtin: the onFulfilled variant resumes execution at the saved PC and
+// forwards the value, the onRejected variant throws the value.
+
+void Generate_WasmResumeHelper(MacroAssembler* masm, wasm::OnResume on_resume) {
   __ EnterFrame(StackFrame::STACK_SWITCH);
 
   Register param_count = rax;
@@ -4152,8 +4156,7 @@ void Builtins::Generate_WasmResume(MacroAssembler* masm) {
       FieldOperand(sfi, SharedFunctionInfo::kFunctionDataOffset));
   Register suspender = rax;
   __ LoadAnyTaggedField(
-      suspender,
-      FieldOperand(function_data, WasmOnFulfilledData::kSuspenderOffset));
+      suspender, FieldOperand(function_data, WasmResumeData::kSuspenderOffset));
   // Check the suspender state.
   Label suspender_is_suspended;
   Register state = rdx;
@@ -4232,12 +4235,30 @@ void Builtins::Generate_WasmResume(MacroAssembler* masm) {
   // Move resolved value to return register.
   __ movq(kReturnRegister0, Operand(rbp, 3 * kSystemPointerSize));
   __ Move(GCScanSlotPlace, 0);
-  LoadJumpBuffer(masm, target_jmpbuf, true);
+  if (on_resume == wasm::OnResume::kThrow) {
+    // Switch to the continuation's stack without restoring the PC.
+    LoadJumpBuffer(masm, target_jmpbuf, false);
+    // Forward the onRejected value to kThrow.
+    __ pushq(kReturnRegister0);
+    __ CallRuntime(Runtime::kThrow);
+  } else {
+    // Resume the continuation normally.
+    LoadJumpBuffer(masm, target_jmpbuf, true);
+  }
   __ Trap();
   __ bind(&suspend);
   __ LeaveFrame(StackFrame::STACK_SWITCH);
   __ ret(3);
 }
+}  // namespace
+
+void Builtins::Generate_WasmResume(MacroAssembler* masm) {
+  Generate_WasmResumeHelper(masm, wasm::OnResume::kContinue);
+}
+
+void Builtins::Generate_WasmReject(MacroAssembler* masm) {
+  Generate_WasmResumeHelper(masm, wasm::OnResume::kThrow);
+}
 
 void Builtins::Generate_WasmOnStackReplace(MacroAssembler* masm) {
   MemOperand OSRTargetSlot(rbp, -wasm::kOSRTargetOffset);

src/codegen/code-stub-assembler.cc

@@ -14740,7 +14740,7 @@ TNode<CodeT> CodeStubAssembler::GetSharedFunctionInfoCode(
     WASM_EXPORTED_FUNCTION_DATA_TYPE,
     WASM_JS_FUNCTION_DATA_TYPE,
     ASM_WASM_DATA_TYPE,
-    WASM_ON_FULFILLED_DATA_TYPE,
+    WASM_RESUME_DATA_TYPE,
 #endif  // V8_ENABLE_WEBASSEMBLY
   };
   Label check_is_bytecode_array(this);
@@ -14750,7 +14750,7 @@ TNode<CodeT> CodeStubAssembler::GetSharedFunctionInfoCode(
   Label check_is_function_template_info(this);
   Label check_is_interpreter_data(this);
   Label check_is_wasm_function_data(this);
-  Label check_is_wasm_on_fulfilled(this);
+  Label check_is_wasm_resume(this);
   Label* case_labels[] = {
     &check_is_bytecode_array,
     &check_is_baseline_data,
@@ -14764,7 +14764,7 @@ TNode<CodeT> CodeStubAssembler::GetSharedFunctionInfoCode(
     &check_is_wasm_function_data,
     &check_is_wasm_function_data,
     &check_is_asm_wasm_data,
-    &check_is_wasm_on_fulfilled,
+    &check_is_wasm_resume,
 #endif  // V8_ENABLE_WEBASSEMBLY
   };
   static_assert(arraysize(case_values) == arraysize(case_labels));
@@ -14819,8 +14819,8 @@ TNode<CodeT> CodeStubAssembler::GetSharedFunctionInfoCode(
   sfi_code = HeapConstant(BUILTIN_CODE(isolate(), InstantiateAsmJs));
   Goto(&done);
 
-  // IsWasmOnFulfilledData: Resume the suspended wasm continuation.
-  BIND(&check_is_wasm_on_fulfilled);
+  // IsWasmResumeData: Resume the suspended wasm continuation.
+  BIND(&check_is_wasm_resume);
   sfi_code = HeapConstant(BUILTIN_CODE(isolate(), WasmResume));
   Goto(&done);
 #endif  // V8_ENABLE_WEBASSEMBLY

src/diagnostics/objects-debug.cc

@@ -950,7 +950,7 @@ void SharedFunctionInfo::SharedFunctionInfoVerify(ReadOnlyRoots roots) {
 #if V8_ENABLE_WEBASSEMBLY
   bool is_wasm = HasWasmExportedFunctionData() || HasAsmWasmData() ||
                  HasWasmJSFunctionData() || HasWasmCapiFunctionData() ||
-                 HasWasmOnFulfilledData();
+                 HasWasmResumeData();
 #else
   bool is_wasm = false;
 #endif  // V8_ENABLE_WEBASSEMBLY

src/diagnostics/objects-printer.cc

@@ -2053,8 +2053,8 @@ void WasmJSFunctionData::WasmJSFunctionDataPrint(std::ostream& os) {
   os << "\n";
 }
 
-void WasmOnFulfilledData::WasmOnFulfilledDataPrint(std::ostream& os) {
-  PrintHeader(os, "WasmOnFulfilledData");
+void WasmResumeData::WasmResumeDataPrint(std::ostream& os) {
+  PrintHeader(os, "WasmResumeData");
   os << "\n - suspender: " << Brief(suspender());
   os << '\n';
 }

src/heap/factory.cc

@@ -1600,14 +1600,14 @@ Handle<WasmJSFunctionData> Factory::NewWasmJSFunctionData(
   return handle(result, isolate());
 }
 
-Handle<WasmOnFulfilledData> Factory::NewWasmOnFulfilledData(
-    Handle<WasmSuspenderObject> suspender) {
-  Map map = *wasm_onfulfilled_data_map();
-  WasmOnFulfilledData result =
-      WasmOnFulfilledData::cast(AllocateRawWithImmortalMap(
-          map.instance_size(), AllocationType::kOld, map));
+Handle<WasmResumeData> Factory::NewWasmResumeData(
+    Handle<WasmSuspenderObject> suspender, wasm::OnResume on_resume) {
+  Map map = *wasm_resume_data_map();
+  WasmResumeData result = WasmResumeData::cast(AllocateRawWithImmortalMap(
+      map.instance_size(), AllocationType::kOld, map));
   DisallowGarbageCollection no_gc;
   result.set_suspender(*suspender);
+  result.set_on_resume(static_cast<int>(on_resume));
   return handle(result, isolate());
 }
 
@@ -1776,8 +1776,8 @@ Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfoForWasmJSFunction(
   return NewSharedFunctionInfo(name, data, Builtin::kNoBuiltinId);
 }
 
-Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfoForWasmOnFulfilled(
-    Handle<WasmOnFulfilledData> data) {
+Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfoForWasmResume(
+    Handle<WasmResumeData> data) {
   return NewSharedFunctionInfo({}, data, Builtin::kNoBuiltinId);
 }
 

src/heap/factory.h

@@ -78,6 +78,7 @@ class ArrayType;
 class StructType;
 struct WasmElemSegment;
 class WasmValue;
+enum class OnResume : int;
 }  // namespace wasm
 #endif
 
@@ -638,8 +639,8 @@ class V8_EXPORT_PRIVATE Factory : public FactoryBase<Factory> {
       int parameter_count, Handle<PodArray<wasm::ValueType>> serialized_sig,
       Handle<CodeT> wrapper_code, Handle<Map> rtt,
       Handle<HeapObject> suspender);
-  Handle<WasmOnFulfilledData> NewWasmOnFulfilledData(
-      Handle<WasmSuspenderObject> suspender);
+  Handle<WasmResumeData> NewWasmResumeData(
+      Handle<WasmSuspenderObject> suspender, wasm::OnResume on_resume);
   Handle<WasmStruct> NewWasmStruct(const wasm::StructType* type,
                                    wasm::WasmValue* args, Handle<Map> map);
   Handle<WasmArray> NewWasmArrayFromElements(
@@ -657,8 +658,8 @@ class V8_EXPORT_PRIVATE Factory : public FactoryBase<Factory> {
       Handle<String> name, Handle<WasmExportedFunctionData> data);
   Handle<SharedFunctionInfo> NewSharedFunctionInfoForWasmJSFunction(
       Handle<String> name, Handle<WasmJSFunctionData> data);
-  Handle<SharedFunctionInfo> NewSharedFunctionInfoForWasmOnFulfilled(
-      Handle<WasmOnFulfilledData> data);
+  Handle<SharedFunctionInfo> NewSharedFunctionInfoForWasmResume(
+      Handle<WasmResumeData> data);
   Handle<SharedFunctionInfo> NewSharedFunctionInfoForWasmCapiFunction(
       Handle<WasmCapiFunctionData> data);
 #endif  // V8_ENABLE_WEBASSEMBLY

src/heap/objects-visiting.h

@@ -67,7 +67,7 @@ namespace internal {
   IF_WASM(V, WasmJSFunctionData)        \
   IF_WASM(V, WasmStruct)                \
   IF_WASM(V, WasmSuspenderObject)       \
-  IF_WASM(V, WasmOnFulfilledData)       \
+  IF_WASM(V, WasmResumeData)            \
   IF_WASM(V, WasmTypeInfo)
 
 #define FORWARD_DECLARE(TypeName) class TypeName;

src/heap/setup-heap-internal.cc

@@ -517,8 +517,8 @@ bool Heap::CreateInitialMaps() {
             WasmInternalFunction::kSize, wasm_internal_function)
     IF_WASM(ALLOCATE_MAP, WASM_JS_FUNCTION_DATA_TYPE, WasmJSFunctionData::kSize,
             wasm_js_function_data)
-    IF_WASM(ALLOCATE_MAP, WASM_ON_FULFILLED_DATA_TYPE,
-            WasmOnFulfilledData::kSize, wasm_onfulfilled_data)
+    IF_WASM(ALLOCATE_MAP, WASM_RESUME_DATA_TYPE, WasmResumeData::kSize,
+            wasm_resume_data)
     IF_WASM(ALLOCATE_MAP, WASM_TYPE_INFO_TYPE, kVariableSizeSentinel,
             wasm_type_info)
 

src/objects/map.cc

@@ -393,8 +393,8 @@ VisitorId Map::GetVisitorId(Map map) {
       return kVisitWasmInternalFunction;
     case WASM_JS_FUNCTION_DATA_TYPE:
       return kVisitWasmJSFunctionData;
-    case WASM_ON_FULFILLED_DATA_TYPE:
-      return kVisitWasmOnFulfilledData;
+    case WASM_RESUME_DATA_TYPE:
+      return kVisitWasmResumeData;
     case WASM_API_FUNCTION_REF_TYPE:
       return kVisitWasmApiFunctionRef;
     case WASM_EXPORTED_FUNCTION_DATA_TYPE:

src/objects/map.h

@@ -83,7 +83,7 @@ enum InstanceType : uint16_t;
   IF_WASM(V, WasmInstanceObject)        \
   IF_WASM(V, WasmInternalFunction)      \
   IF_WASM(V, WasmJSFunctionData)        \
-  IF_WASM(V, WasmOnFulfilledData)       \
+  IF_WASM(V, WasmResumeData)            \
   IF_WASM(V, WasmStruct)                \
   IF_WASM(V, WasmSuspenderObject)       \
   IF_WASM(V, WasmTypeInfo)              \

src/objects/object-list-macros.h

@@ -258,7 +258,7 @@ class ZoneForwardList;
   IF_WASM(V, WasmMemoryObject)                  \
   IF_WASM(V, WasmModuleObject)                  \
   IF_WASM(V, WasmObject)                        \
-  IF_WASM(V, WasmOnFulfilledData)               \
+  IF_WASM(V, WasmResumeData)                    \
   IF_WASM(V, WasmStruct)                        \
   IF_WASM(V, WasmTypeInfo)                      \
   IF_WASM(V, WasmTableObject)                   \

src/objects/objects-body-descriptors-inl.h

@@ -1172,8 +1172,8 @@ auto BodyDescriptorApply(InstanceType type, Args&&... args) {
       return CALL_APPLY(WasmInternalFunction);
     case WASM_JS_FUNCTION_DATA_TYPE:
       return CALL_APPLY(WasmJSFunctionData);
-    case WASM_ON_FULFILLED_DATA_TYPE:
-      return CALL_APPLY(WasmOnFulfilledData);
+    case WASM_RESUME_DATA_TYPE:
+      return CALL_APPLY(WasmResumeData);
     case WASM_STRUCT_TYPE:
       return CALL_APPLY(WasmStruct);
     case WASM_TYPE_INFO_TYPE:

src/objects/shared-function-info-inl.h

@@ -711,8 +711,8 @@ bool SharedFunctionInfo::HasWasmCapiFunctionData() const {
   return function_data(kAcquireLoad).IsWasmCapiFunctionData();
 }
 
-bool SharedFunctionInfo::HasWasmOnFulfilledData() const {
-  return function_data(kAcquireLoad).IsWasmOnFulfilledData();
+bool SharedFunctionInfo::HasWasmResumeData() const {
+  return function_data(kAcquireLoad).IsWasmResumeData();
 }
 
 AsmWasmData SharedFunctionInfo::asm_wasm_data() const {

src/objects/shared-function-info.cc

@@ -108,8 +108,13 @@ CodeT SharedFunctionInfo::GetCode() const {
   if (data.IsWasmCapiFunctionData()) {
     return wasm_capi_function_data().wrapper_code();
   }
-  if (data.IsWasmOnFulfilledData()) {
-    return isolate->builtins()->code(Builtin::kWasmResume);
+  if (data.IsWasmResumeData()) {
+    if (static_cast<wasm::OnResume>(wasm_resume_data().on_resume()) ==
+        wasm::OnResume::kContinue) {
+      return isolate->builtins()->code(Builtin::kWasmResume);
+    } else {
+      return isolate->builtins()->code(Builtin::kWasmReject);
+    }
   }
 #endif  // V8_ENABLE_WEBASSEMBLY
   if (data.IsUncompiledData()) {
@@ -147,6 +152,11 @@ WasmCapiFunctionData SharedFunctionInfo::wasm_capi_function_data() const {
   DCHECK(HasWasmCapiFunctionData());
   return WasmCapiFunctionData::cast(function_data(kAcquireLoad));
 }
+
+WasmResumeData SharedFunctionInfo::wasm_resume_data() const {
+  DCHECK(HasWasmResumeData());
+  return WasmResumeData::cast(function_data(kAcquireLoad));
+}
 #endif  // V8_ENABLE_WEBASSEMBLY
 
 SharedFunctionInfo::ScriptIterator::ScriptIterator(Isolate* isolate,

src/objects/shared-function-info.h

@@ -40,6 +40,7 @@ class Signature;
 class WasmCapiFunctionData;
 class WasmExportedFunctionData;
 class WasmJSFunctionData;
+class WasmResumeData;
 
 namespace wasm {
 struct WasmModule;
@@ -347,7 +348,7 @@ class SharedFunctionInfo
   inline bool HasWasmExportedFunctionData() const;
   inline bool HasWasmJSFunctionData() const;
   inline bool HasWasmCapiFunctionData() const;
-  inline bool HasWasmOnFulfilledData() const;
+  inline bool HasWasmResumeData() const;
   inline AsmWasmData asm_wasm_data() const;
   inline void set_asm_wasm_data(AsmWasmData data);
 
@@ -355,6 +356,7 @@ class SharedFunctionInfo
   wasm_exported_function_data() const;
   WasmJSFunctionData wasm_js_function_data() const;
   WasmCapiFunctionData wasm_capi_function_data() const;
+  WasmResumeData wasm_resume_data() const;
 
   inline const wasm::WasmModule* wasm_module() const;
   inline const wasm::FunctionSig* wasm_function_signature() const;

src/roots/roots.h

@@ -120,7 +120,7 @@ class Symbol;
           WasmExportedFunctionDataMap)                                         \
   IF_WASM(V, Map, wasm_internal_function_map, WasmInternalFunctionMap)         \
   IF_WASM(V, Map, wasm_js_function_data_map, WasmJSFunctionDataMap)            \
-  IF_WASM(V, Map, wasm_onfulfilled_data_map, WasmOnFulfilledDataMap)           \
+  IF_WASM(V, Map, wasm_resume_data_map, WasmResumeDataMap)                     \
   IF_WASM(V, Map, wasm_type_info_map, WasmTypeInfoMap)                         \
   V(Map, weak_fixed_array_map, WeakFixedArrayMap)                              \
   V(Map, weak_array_list_map, WeakArrayListMap)                                \

src/runtime/runtime-wasm.cc

@@ -832,15 +832,16 @@ RUNTIME_FUNCTION(Runtime_WasmSyncStackLimit) {
   return ReadOnlyRoots(isolate).undefined_value();
 }
 
-// Takes a promise and a suspender, and returns promise.then(onFulfilled), where
-// onFulfilled resumes the suspender.
+// Takes a promise and a suspender, and returns
+// promise.then(suspender.resume(), suspender.reject());
 RUNTIME_FUNCTION(Runtime_WasmCreateResumePromise) {
   CHECK(FLAG_experimental_wasm_stack_switching);
   HandleScope scope(isolate);
   Handle<Object> promise = args.at(0);
   Handle<WasmSuspenderObject> suspender = args.at<WasmSuspenderObject>(1);
 
-  i::Handle<i::Object> argv[] = {handle(suspender->resume(), isolate)};
+  i::Handle<i::Object> argv[] = {handle(suspender->resume(), isolate),
+                                 handle(suspender->reject(), isolate)};
   i::Handle<i::Object> result;
   bool has_pending_exception =
       !i::Execution::CallBuiltin(isolate, isolate->promise_then(), promise,

src/wasm/wasm-objects-inl.h

@@ -55,7 +55,7 @@ TQ_OBJECT_CONSTRUCTORS_IMPL(WasmStruct)
 TQ_OBJECT_CONSTRUCTORS_IMPL(WasmArray)
 TQ_OBJECT_CONSTRUCTORS_IMPL(WasmContinuationObject)
 TQ_OBJECT_CONSTRUCTORS_IMPL(WasmSuspenderObject)
-TQ_OBJECT_CONSTRUCTORS_IMPL(WasmOnFulfilledData)
+TQ_OBJECT_CONSTRUCTORS_IMPL(WasmResumeData)
 
 CAST_ACCESSOR(WasmInstanceObject)
 

src/wasm/wasm-objects.cc

@@ -1807,15 +1807,22 @@ Handle<WasmSuspenderObject> WasmSuspenderObject::New(Isolate* isolate) {
   suspender->set_state(kInactive);
   // Instantiate the callable object which resumes this Suspender. This will be
   // used implicitly as the onFulfilled callback of the returned JS promise.
-  Handle<WasmOnFulfilledData> function_data =
-      isolate->factory()->NewWasmOnFulfilledData(suspender);
-  Handle<SharedFunctionInfo> shared =
-      isolate->factory()->NewSharedFunctionInfoForWasmOnFulfilled(
-          function_data);
+  Handle<WasmResumeData> resume_data = isolate->factory()->NewWasmResumeData(
+      suspender, wasm::OnResume::kContinue);
+  Handle<SharedFunctionInfo> resume_sfi =
+      isolate->factory()->NewSharedFunctionInfoForWasmResume(resume_data);
   Handle<Context> context(isolate->native_context());
   Handle<JSObject> resume =
-      Factory::JSFunctionBuilder{isolate, shared, context}.Build();
+      Factory::JSFunctionBuilder{isolate, resume_sfi, context}.Build();
+
+  Handle<WasmResumeData> reject_data =
+      isolate->factory()->NewWasmResumeData(suspender, wasm::OnResume::kThrow);
+  Handle<SharedFunctionInfo> reject_sfi =
+      isolate->factory()->NewSharedFunctionInfoForWasmResume(reject_data);
+  Handle<JSObject> reject =
+      Factory::JSFunctionBuilder{isolate, reject_sfi, context}.Build();
   suspender->set_resume(*resume);
+  suspender->set_reject(*reject);
   return suspender;
 }
 

src/wasm/wasm-objects.h

@@ -787,14 +787,17 @@ class WasmCapiFunctionData
   TQ_OBJECT_CONSTRUCTORS(WasmCapiFunctionData)
 };
 
-class WasmOnFulfilledData
-    : public TorqueGeneratedWasmOnFulfilledData<WasmOnFulfilledData,
-                                                HeapObject> {
+namespace wasm {
+enum class OnResume : int { kContinue, kThrow };
+}
+
+class WasmResumeData
+    : public TorqueGeneratedWasmResumeData<WasmResumeData, HeapObject> {
  public:
   using BodyDescriptor =
-      FlexibleBodyDescriptor<WasmOnFulfilledData::kStartOfStrongFieldsOffset>;
-  DECL_PRINTER(WasmOnFulfilledData)
-  TQ_OBJECT_CONSTRUCTORS(WasmOnFulfilledData)
+      FlexibleBodyDescriptor<WasmResumeData::kStartOfStrongFieldsOffset>;
+  DECL_PRINTER(WasmResumeData)
+  TQ_OBJECT_CONSTRUCTORS(WasmResumeData)
 };
 
 class WasmScript : public AllStatic {

src/wasm/wasm-objects.tq

@@ -80,8 +80,9 @@ extern class WasmCapiFunctionData extends WasmFunctionData {
   serialized_signature: PodArrayOfWasmValueType;
 }
 
-extern class WasmOnFulfilledData extends HeapObject {
+extern class WasmResumeData extends HeapObject {
   suspender: WasmSuspenderObject;
+  on_resume: Smi;  // See wasm::OnResume enum.
 }
 
 extern class WasmIndirectFunctionTable extends Struct {
@@ -104,6 +105,7 @@ extern class WasmSuspenderObject extends JSObject {
   continuation: WasmContinuationObject|Undefined;
   parent: WasmSuspenderObject|Undefined;
   resume: JSObject|Undefined;
+  reject: JSObject|Undefined;
   state: Smi;  // 0: Inactive, 1: Active, 2: Suspended.
 }
 

test/mjsunit/wasm/stack-switching.js

@@ -295,3 +295,31 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   let combined_promise = wrapped_export();
   assertThrowsAsync(combined_promise, WebAssembly.Exception);
 })();
+
+(function TestStackSwitchPromiseReject() {
+  print(arguments.callee.name);
+  let tag = new WebAssembly.Tag({parameters: ['i32']});
+  let builder = new WasmModuleBuilder();
+  import_index = builder.addImport('m', 'import', kSig_i_v);
+  tag_index = builder.addImportedTag('m', 'tag', kSig_v_i);
+  builder.addFunction("test", kSig_i_v)
+      .addBody([
+          kExprTry, kWasmI32,
+          kExprCallFunction, import_index,
+          kExprCatch, tag_index,
+          kExprEnd,
+      ]).exportFunc();
+  let suspender = new WebAssembly.Suspender();
+  function js_import() {
+    return Promise.reject(new WebAssembly.Exception(tag, [42]));
+  };
+  let wasm_js_import = new WebAssembly.Function(
+      {parameters: [], results: ['externref']}, js_import);
+  let suspending_wasm_js_import =
+      suspender.suspendOnReturnedPromise(wasm_js_import);
+
+  let instance = builder.instantiate({m: {import: suspending_wasm_js_import, tag: tag}});
+  let wrapped_export = suspender.returnPromiseOnSuspend(instance.exports.test);
+  let combined_promise = wrapped_export();
+  assertPromiseResult(combined_promise, v => assertEquals(v, 42));
+})();

tools/v8heapconst.py

@@ -167,7 +167,7 @@ INSTANCE_TYPES = {
   260: "SORT_STATE_TYPE",
   261: "SWISS_NAME_DICTIONARY_TYPE",
   262: "WASM_API_FUNCTION_REF_TYPE",
-  263: "WASM_ON_FULFILLED_DATA_TYPE",
+  263: "WASM_RESUME_DATA_TYPE",
   264: "WEAK_ARRAY_LIST_TYPE",
   265: "WEAK_CELL_TYPE",
   266: "WASM_ARRAY_TYPE",
@@ -353,7 +353,7 @@ KNOWN_MAPS = {
     ("read_only_space", 0x02f51): (223, "WasmExportedFunctionDataMap"),
     ("read_only_space", 0x02f79): (205, "WasmInternalFunctionMap"),
     ("read_only_space", 0x02fa1): (224, "WasmJSFunctionDataMap"),
-    ("read_only_space", 0x02fc9): (263, "WasmOnFulfilledDataMap"),
+    ("read_only_space", 0x02fc9): (263, "WasmResumeDataMap"),
     ("read_only_space", 0x02ff1): (206, "WasmTypeInfoMap"),
     ("read_only_space", 0x03019): (235, "WeakFixedArrayMap"),
     ("read_only_space", 0x03041): (179, "EphemeronHashTableMap"),