[async-await] don't eagerly resolve Promise before finally blocks have executed

src/interpreter/bytecode-generator.cc

 // Copyright 2015 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/interpreter/bytecode-generator.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-stubs.h"
@@ skipping 2152 matching lines @@
 }
 
 void BytecodeGenerator::BuildVariableLoadForAccumulatorValue(
     Variable* variable, FeedbackVectorSlot slot, HoleCheckMode hole_check_mode,
     TypeofMode typeof_mode) {
   ValueResultScope accumulator_result(this);
   BuildVariableLoad(variable, slot, hole_check_mode, typeof_mode);
 }
 
 void BytecodeGenerator::BuildReturn() {
+  if (IsAsyncFunction(info()->literal()->kind())) {
+    RegisterAllocationScope register_scope(this);
+    RegisterList args = register_allocator()->NewRegisterList(3);
+    Register receiver = args[0];
+    Register promise = args[1];
+    Register return_value = args[2];
+    builder()->StoreAccumulatorInRegister(return_value);
+
+    Variable* var_promise = scope()->promise_var();
+    DCHECK_NOT_NULL(var_promise);
+    BuildVariableLoad(var_promise, FeedbackVectorSlot::Invalid(),
+                      HoleCheckMode::kElided);
+    builder()
+        ->StoreAccumulatorInRegister(promise)
+        .LoadUndefined()
+        .StoreAccumulatorInRegister(receiver)
+        .CallJSRuntime(Context::PROMISE_RESOLVE_INDEX, args)
+        .LoadAccumulatorWithRegister(promise);
+  }
+
   if (FLAG_trace) {
     RegisterAllocationScope register_scope(this);
     Register result = register_allocator()->NewRegister();
     // Runtime returns {result} value, preserving accumulator.
     builder()->StoreAccumulatorInRegister(result).CallRuntime(
         Runtime::kTraceExit, result);
   }
   builder()->Return();
 }
 
@@ skipping 1396 matching lines @@
 }
 
 Runtime::FunctionId BytecodeGenerator::StoreKeyedToSuperRuntimeId() {
   return is_strict(language_mode()) ? Runtime::kStoreKeyedToSuper_Strict
                                     : Runtime::kStoreKeyedToSuper_Sloppy;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8