[ESnext] Implement Promise.prototype.finally

src/builtins/builtins-promise.h

 // Copyright 2016 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.
 
 #ifndef V8_BUILTINS_BUILTINS_PROMISE_H_
 #define V8_BUILTINS_BUILTINS_PROMISE_H_
 
 #include "src/code-stub-assembler.h"
 #include "src/contexts.h"
 
@@ skipping 18 matching lines @@
     kDebugEventSlot,
     kPromiseContextLength,
   };
 
   enum FunctionContextSlot {
     kCapabilitySlot = Context::MIN_CONTEXT_SLOTS,
 
     kCapabilitiesContextLength,
   };
 
+  // This is used by the PromiseThenFinally and PromiseCatchFinally
+  // builtins to store the onFinally in the onFinallySlot.
+  //
+  // This is also used by the PromiseValueThunkFinally to store the
+  // value in the onFinallySlot and PromiseThrowerFinally to store the
+  // reason in the onFinallySlot.
+  enum PromiseFinallyContextSlot {
+    kOnFinallySlot = Context::MIN_CONTEXT_SLOTS,
+
+    kOnFinallyContextLength,
+  };
+
   explicit PromiseBuiltinsAssembler(CodeAssemblerState* state)
       : CodeStubAssembler(state) {}
   // These allocate and initialize a promise with pending state and
   // undefined fields.
   //
   // This uses undefined as the parent promise for the promise init
   // hook.
   Node* AllocateAndInitJSPromise(Node* context);
   // This uses the given parent as the parent promise for the promise
   // init hook.
@@ skipping 59 matching lines @@
                       v8::Promise::PromiseState status);
 
   void BranchIfAccessCheckFailed(Node* context, Node* native_context,
                                  Node* promise_constructor, Node* executor,
                                  Label* if_noaccess);
 
   void InternalPromiseReject(Node* context, Node* promise, Node* value,
                              bool debug_event);
   void InternalPromiseReject(Node* context, Node* promise, Node* value,
                              Node* debug_event);
+  std::pair<Node*, Node*> CreatePromiseFinallyFunctions(Node* on_finally,
+                                                        Node* native_context);
+  Node* CreatePromiseFinallyContext(Node* on_finally, Node* native_context);
+
+  Node* CreateValueThunkFunction(Node* value, Node* native_context);
+  Node* CreateValueThunkFunctionContext(Node* value, Node* native_context);
+
+  Node* CreateThrowerFunctionContext(Node* reason, Node* native_context);
+  Node* CreateThrowerFunction(Node* reason, Node* native_context);
 
  private:
   Node* AllocateJSPromise(Node* context);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_BUILTINS_BUILTINS_PROMISE_H_