[promises] Port Promise.race to Torque.

Bug: v8:9838
Change-Id: Iee3bcaa3a7149309c01d16be67d189ccc56bd0e8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1965919
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65562}

BUILD.gn

@@ -988,6 +988,7 @@ torque_files = [
   "src/builtins/promise-abstract-operations.tq",
   "src/builtins/promise-constructor.tq",
   "src/builtins/promise-finally.tq",
+  "src/builtins/promise-race.tq",
   "src/builtins/promise-reaction-job.tq",
   "src/builtins/promise-resolve.tq",
   "src/builtins/promise-then.tq",

src/builtins/base.tq

@@ -352,6 +352,7 @@ extern macro LengthStringConstant(): String;
 extern macro NanConstant(): NaN;
 extern macro IteratorSymbolConstant(): PublicSymbol;
 extern macro MatchSymbolConstant(): Symbol;
+extern macro ReturnStringConstant(): String;
 
 const TheHole: TheHole = TheHoleConstant();
 const Null: Null = NullConstant();
@@ -360,6 +361,8 @@ const True: True = TrueConstant();
 const False: False = FalseConstant();
 const kEmptyString: EmptyString = EmptyStringConstant();
 const kLengthString: String = LengthStringConstant();
+const kReturnString: String = ReturnStringConstant();
+
 const kNaN: NaN = NanConstant();
 const kZero: Zero = %RawDownCast<Zero>(SmiConstant(0));
 

src/builtins/builtins-definitions.h

@@ -717,8 +717,6 @@ namespace internal {
   /* ES #sec-promise.all */                                                    \
   TFJ(PromiseAll, 1, kReceiver, kIterable)                                     \
   TFJ(PromiseAllResolveElementClosure, 1, kReceiver, kValue)                   \
-  /* ES #sec-promise.race */                                                   \
-  TFJ(PromiseRace, 1, kReceiver, kIterable)                                    \
   /* ES #sec-promise.allsettled */                                             \
   TFJ(PromiseAllSettled, 1, kReceiver, kIterable)                              \
   TFJ(PromiseAllSettledResolveElementClosure, 1, kReceiver, kValue)            \

src/builtins/builtins-promise-gen.cc

@@ -943,140 +943,5 @@ TF_BUILTIN(PromiseAllSettledRejectElementClosure, PromiseBuiltinsAssembler) {
       });
 }
 
-// ES#sec-promise.race
-// Promise.race ( iterable )
-TF_BUILTIN(PromiseRace, PromiseBuiltinsAssembler) {
-  IteratorBuiltinsAssembler iter_assembler(state());
-  TVARIABLE(Object, var_exception, TheHoleConstant());
-
-  Node* const receiver = Parameter(Descriptor::kReceiver);
-  const TNode<Context> context = CAST(Parameter(Descriptor::kContext));
-  ThrowIfNotJSReceiver(context, CAST(receiver),
-                       MessageTemplate::kCalledOnNonObject, "Promise.race");
-
-  // Let promiseCapability be ? NewPromiseCapability(C).
-  // Don't fire debugEvent so that forwarding the rejection through all does not
-  // trigger redundant ExceptionEvents
-  const TNode<Oddball> debug_event = FalseConstant();
-  const TNode<PromiseCapability> capability = CAST(CallBuiltin(
-      Builtins::kNewPromiseCapability, context, receiver, debug_event));
-
-  const TNode<Object> resolve =
-      LoadObjectField(capability, PromiseCapability::kResolveOffset);
-  const TNode<Object> reject =
-      LoadObjectField(capability, PromiseCapability::kRejectOffset);
-
-  Label close_iterator(this, Label::kDeferred);
-  Label reject_promise(this, Label::kDeferred);
-
-  // For catch prediction, don't treat the .then calls as handling it;
-  // instead, recurse outwards.
-  SetForwardingHandlerIfTrue(context, IsDebugActive(), reject);
-
-  // Let iterator be GetIterator(iterable).
-  // IfAbruptRejectPromise(iterator, promiseCapability).
-  Node* const iterable = Parameter(Descriptor::kIterable);
-  IteratorRecord iterator = iter_assembler.GetIterator(
-      context, iterable, &reject_promise, &var_exception);
-
-  // Let result be PerformPromiseRace(iteratorRecord, C, promiseCapability).
-  {
-    // We can skip the "resolve" lookup on {constructor} if it's the
-    // Promise constructor and the Promise.resolve protector is intact,
-    // as that guards the lookup path for the "resolve" property on the
-    // Promise constructor.
-    Label loop(this), break_loop(this), if_slow(this, Label::kDeferred);
-    const TNode<NativeContext> native_context = LoadNativeContext(context);
-    TVARIABLE(Object, var_promise_resolve_function, UndefinedConstant());
-    GotoIfNotPromiseResolveLookupChainIntact(native_context, receiver,
-                                             &if_slow);
-    Goto(&loop);
-
-    BIND(&if_slow);
-    {
-      // 3. Let _promiseResolve_ be ? Get(_constructor_, `"resolve"`).
-      TNode<Object> resolve =
-          GetProperty(native_context, receiver, factory()->resolve_string());
-      GotoIfException(resolve, &close_iterator, &var_exception);
-
-      // 4. If IsCallable(_promiseResolve_) is *false*, throw a *TypeError*
-      // exception.
-      ThrowIfNotCallable(context, resolve, "resolve");
-
-      var_promise_resolve_function = resolve;
-      Goto(&loop);
-    }
-
-    BIND(&loop);
-    {
-      const TNode<Map> fast_iterator_result_map = CAST(LoadContextElement(
-          native_context, Context::ITERATOR_RESULT_MAP_INDEX));
-
-      // Let next be IteratorStep(iteratorRecord.[[Iterator]]).
-      // If next is an abrupt completion, set iteratorRecord.[[Done]] to true.
-      // ReturnIfAbrupt(next).
-      const TNode<JSReceiver> next = iter_assembler.IteratorStep(
-          context, iterator, &break_loop, fast_iterator_result_map,
-          &reject_promise, &var_exception);
-
-      // Let nextValue be IteratorValue(next).
-      // If nextValue is an abrupt completion, set iteratorRecord.[[Done]] to
-      //     true.
-      // ReturnIfAbrupt(nextValue).
-      const TNode<Object> next_value =
-          iter_assembler.IteratorValue(context, next, fast_iterator_result_map,
-                                       &reject_promise, &var_exception);
-
-      // Let nextPromise be ? Call(constructor, _promiseResolve_, « nextValue
-      // »).
-      Node* const next_promise = CallResolve(
-          native_context, receiver, var_promise_resolve_function.value(),
-          next_value, &close_iterator, &var_exception);
-
-      // Perform ? Invoke(nextPromise, "then", « resolveElement,
-      //                  resultCapability.[[Reject]] »).
-      const TNode<Object> then =
-          GetProperty(context, next_promise, factory()->then_string());
-      GotoIfException(then, &close_iterator, &var_exception);
-
-      Node* const then_call =
-          CallJS(CodeFactory::Call(isolate(),
-                                   ConvertReceiverMode::kNotNullOrUndefined),
-                 context, then, next_promise, resolve, reject);
-      GotoIfException(then_call, &close_iterator, &var_exception);
-
-      // For catch prediction, mark that rejections here are semantically
-      // handled by the combined Promise.
-      SetPromiseHandledByIfTrue(context, IsDebugActive(), then_call, [=]() {
-        // Load promiseCapability.[[Promise]]
-        return LoadObjectField(capability, PromiseCapability::kPromiseOffset);
-      });
-      Goto(&loop);
-    }
-
-    BIND(&break_loop);
-    Return(LoadObjectField(capability, PromiseCapability::kPromiseOffset));
-  }
-
-  BIND(&close_iterator);
-  {
-    CSA_ASSERT(this, IsNotTheHole(var_exception.value()));
-    iter_assembler.IteratorCloseOnException(context, iterator, &reject_promise,
-                                            &var_exception);
-  }
-
-  BIND(&reject_promise);
-  {
-    const TNode<Object> reject =
-        LoadObjectField(capability, PromiseCapability::kRejectOffset);
-    CallJS(CodeFactory::Call(isolate(), ConvertReceiverMode::kNullOrUndefined),
-           context, reject, UndefinedConstant(), var_exception.value());
-
-    const TNode<Object> promise =
-        LoadObjectField(capability, PromiseCapability::kPromiseOffset);
-    Return(promise);
-  }
-}
-
 }  // namespace internal
 }  // namespace v8

src/builtins/iterator.tq

@@ -72,4 +72,31 @@ namespace iterator {
         otherwise ThrowCalledNonCallable(iteratorMethod);
     return Call(context, iteratorCallable, receiver);
   }
+
+  transitioning
+  macro IteratorCloseOnException(implicit context: Context)(
+      iterator: IteratorRecord, exception: Object): never labels
+  IfException(Object) {
+    // Let return be ? GetMethod(iterator, "return").
+    let method: JSAny;
+    try {
+      method = GetProperty(iterator.object, kReturnString);
+    } catch (e) {
+      goto IfException(e);
+    }
+
+    // If return is undefined, return Completion(completion).
+    if (method == Undefined || method == Null) goto IfException(exception);
+
+    // Let innerResult be Call(return, iterator, « »).
+    // If an exception occurs, the original exception remains bound
+    try {
+      Call(context, UnsafeCast<Callable>(method), iterator.object);
+    } catch (_e) {
+      goto IfException(exception);
+    }
+
+    // (If completion.[[Type]] is throw) return Completion(completion).
+    goto IfException(exception);
+  }
 }

src/builtins/promise-abstract-operations.tq

@@ -523,4 +523,16 @@ namespace promise {
     capability.reject = reject;
     return Undefined;
   }
+
+  transitioning macro CallResolve(implicit context: Context)(
+      constructor: Constructor, resolve: JSAny, value: JSAny): JSAny {
+    // Undefined can never be a valid value for the resolve function,
+    // instead it is used as a special marker for the fast path.
+    if (resolve == Undefined) {
+      return PromiseResolve(constructor, value);
+    } else
+      deferred {
+        return Call(context, UnsafeCast<Callable>(resolve), constructor, value);
+      }
+  }
 }

src/builtins/promise-race.tq

+// Copyright 2019 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include 'src/builtins/builtins-promise-gen.h'
+
+namespace promise {
+
+  extern macro PromiseForwardingHandlerSymbolConstant(): Symbol;
+  const kPromiseForwardingHandlerSymbol: Symbol =
+      PromiseForwardingHandlerSymbolConstant();
+  extern macro PromiseHandledBySymbolConstant(): Symbol;
+  const kPromiseHandledBySymbol: Symbol = PromiseHandledBySymbolConstant();
+  extern macro ResolveStringConstant(): String;
+  const kResolveString: String = ResolveStringConstant();
+  extern macro SetPropertyStrict(Context, Object, Object, Object): Object;
+  extern macro IsPromiseResolveProtectorCellInvalid(): bool;
+
+  macro IsPromiseResolveLookupChainIntact(implicit context: Context)(
+      nativeContext: NativeContext, constructor: JSReceiver): bool {
+    if (IsForceSlowPath()) return false;
+    const promiseFun = UnsafeCast<JSFunction>(
+        nativeContext[NativeContextSlot::PROMISE_FUNCTION_INDEX]);
+    return promiseFun == constructor && !IsPromiseResolveProtectorCellInvalid();
+  }
+
+  // https://tc39.es/ecma262/#sec-promise.race
+  transitioning javascript builtin
+  PromiseRace(js-implicit context: Context, receiver: JSAny)(iterable: JSAny):
+      JSAny {
+    const receiver = Cast<JSReceiver>(receiver)
+        otherwise ThrowTypeError(
+        MessageTemplate::kCalledOnNonObject, 'Promise.race');
+
+    // Let promiseCapability be ? NewPromiseCapability(C).
+    // Don't fire debugEvent so that forwarding the rejection through all does
+    // not trigger redundant ExceptionEvents
+    const capability = NewPromiseCapability(receiver, False);
+    const resolve = capability.resolve;
+    const reject = capability.reject;
+    const promise = capability.promise;
+
+    // For catch prediction, don't treat the .then calls as handling it;
+    // instead, recurse outwards.
+    if (IsDebugActive()) deferred {
+        SetPropertyStrict(
+            context, reject, kPromiseForwardingHandlerSymbol, True);
+      }
+
+    try {
+      // Let iterator be GetIterator(iterable).
+      // IfAbruptRejectPromise(iterator, promiseCapability).
+      let i: iterator::IteratorRecord;
+      try {
+        i = iterator::GetIterator(iterable);
+      } catch (e) deferred {
+        goto Reject(e);
+      }
+
+      // Let result be PerformPromiseRace(iteratorRecord, C, promiseCapability).
+      try {
+        // We can skip the "resolve" lookup on {constructor} if it's the
+        // Promise constructor and the Promise.resolve protector is intact,
+        // as that guards the lookup path for the "resolve" property on the
+        // Promise constructor.
+        const nativeContext = LoadNativeContext(context);
+        let promiseResolveFunction: JSAny = Undefined;
+        if (!IsPromiseResolveLookupChainIntact(nativeContext, receiver))
+          deferred {
+            // 3. Let _promiseResolve_ be ? Get(_constructor_, `"resolve"`).
+            const resolve = GetProperty(receiver, kResolveString);
+
+            // 4. If IsCallable(_promiseResolve_) is *false*, throw a
+            // *TypeError* exception.
+            promiseResolveFunction = Cast<Callable>(resolve)
+                otherwise ThrowTypeError(
+                MessageTemplate::kCalledNonCallable, 'resolve');
+          }
+
+        const fastIteratorResultMap = UnsafeCast<Map>(
+            nativeContext[NativeContextSlot::ITERATOR_RESULT_MAP_INDEX]);
+        while (true) {
+          let nextValue: JSAny;
+          try {
+            // Let next be IteratorStep(iteratorRecord.[[Iterator]]).
+            // If next is an abrupt completion, set iteratorRecord.[[Done]] to
+            // true. ReturnIfAbrupt(next).
+            const next: JSReceiver = iterator::IteratorStep(
+                i, fastIteratorResultMap) otherwise return promise;
+
+            // Let nextValue be IteratorValue(next).
+            // If nextValue is an abrupt completion, set iteratorRecord.[[Done]]
+            // to true.
+            // ReturnIfAbrupt(nextValue).
+            nextValue = iterator::IteratorValue(next, fastIteratorResultMap);
+          } catch (e) {
+            goto Reject(e);
+          }
+          // Let nextPromise be ? Call(constructor, _promiseResolve_, «
+          // nextValue »).
+          const nextPromise = CallResolve(
+              UnsafeCast<Constructor>(receiver), promiseResolveFunction,
+              nextValue);
+
+          // Perform ? Invoke(nextPromise, "then", « resolveElement,
+          //                  resultCapability.[[Reject]] »).
+          const then = GetProperty(nextPromise, kThenString);
+          const thenResult = Call(
+              context, UnsafeCast<Callable>(then), nextPromise,
+              UnsafeCast<JSAny>(resolve), UnsafeCast<JSAny>(reject));
+
+          // For catch prediction, mark that rejections here are semantically
+          // handled by the combined Promise.
+          if (IsDebugActive() && !Is<JSPromise>(promise)) deferred {
+              SetPropertyStrict(
+                  context, thenResult, kPromiseHandledBySymbol,
+                  capability.promise);
+            }
+        }
+      } catch (e) deferred {
+        iterator::IteratorCloseOnException(i, e) otherwise Reject;
+      }
+    }
+    label Reject(exception: Object) deferred {
+      Call(
+          context, UnsafeCast<Callable>(reject), Undefined,
+          UnsafeCast<JSAny>(exception));
+      return promise;
+    }
+    unreachable;
+  }
+}

src/codegen/code-stub-assembler.h

@@ -120,8 +120,12 @@ enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
   V(OnePointerFillerMap, one_pointer_filler_map, OnePointerFillerMap)          \
   V(PreparseDataMap, preparse_data_map, PreparseDataMap)                       \
   V(PromiseCapabilityMap, promise_capability_map, PromiseCapabilityMap)        \
+  V(promise_forwarding_handler_symbol, promise_forwarding_handler_symbol,      \
+    PromiseForwardingHandlerSymbol)                                            \
   V(PromiseFulfillReactionJobTaskMap, promise_fulfill_reaction_job_task_map,   \
     PromiseFulfillReactionJobTaskMap)                                          \
+  V(promise_handled_by_symbol, promise_handled_by_symbol,                      \
+    PromiseHandledBySymbol)                                                    \
   V(PromiseReactionMap, promise_reaction_map, PromiseReactionMap)              \
   V(PromiseRejectReactionJobTaskMap, promise_reject_reaction_job_task_map,     \
     PromiseRejectReactionJobTaskMap)                                           \
@@ -130,6 +134,7 @@ enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
   V(replace_symbol, replace_symbol, ReplaceSymbol)                             \
   V(regexp_to_string, regexp_to_string, RegexpToString)                        \
   V(resolve_string, resolve_string, ResolveString)                             \
+  V(return_string, return_string, ReturnString)                                \
   V(SharedFunctionInfoMap, shared_function_info_map, SharedFunctionInfoMap)    \
   V(SloppyArgumentsElementsMap, sloppy_arguments_elements_map,                 \
     SloppyArgumentsElementsMap)                                                \

src/objects/promise.tq

@@ -5,6 +5,7 @@
 @generateCppClass
 extern class PromiseCapability extends Struct {
   promise: JSReceiver|Undefined;
+  // TODO(joshualitt): Can these be typed more specifically.
   resolve: Object;
   reject: Object;
 }