WIP [esnext] implement async iteration proposal

src/builtins/x64/builtins-x64.cc

Index: src/builtins/x64/builtins-x64.cc
diff --git a/src/builtins/x64/builtins-x64.cc b/src/builtins/x64/builtins-x64.cc
index 87dfc7d3a6b6305a4d7ec63c05c36e47b5418a7c..d0cd7b43ad47eb6e3f18b09553b24e6c6e2d87fe 100644
--- a/src/builtins/x64/builtins-x64.cc
+++ b/src/builtins/x64/builtins-x64.cc
@@ -440,19 +440,21 @@ void Builtins::Generate_JSConstructEntryTrampoline(MacroAssembler* masm) {
 }
 
 // static
-void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
+void Builtins::Generate_ResumeGenerator(MacroAssembler* masm,
+                                        ResumeGeneratorType type) {
   // ----------- S t a t e -------------
   //  -- rax    : the value to pass to the generator
   //  -- rbx    : the JSGeneratorObject to resume
   //  -- rdx    : the resume mode (tagged)
   //  -- rsp[0] : return address
   // -----------------------------------
-  __ AssertGeneratorObject(rbx);
 
   // Store input value into generator object.
-  __ movp(FieldOperand(rbx, JSGeneratorObject::kInputOrDebugPosOffset), rax);
-  __ RecordWriteField(rbx, JSGeneratorObject::kInputOrDebugPosOffset, rax, rcx,
-                      kDontSaveFPRegs);
+  int offset = type == ResumeGeneratorType::kYield
+                   ? JSGeneratorObject::kInputOrDebugPosOffset
+                   : JSAsyncGeneratorObject::kAwaitInputOffset;
+  __ movp(FieldOperand(rbx, offset), rax);
+  __ RecordWriteField(rbx, offset, rax, rcx, kDontSaveFPRegs);
 
   // Store resume mode into generator object.
   __ movp(FieldOperand(rbx, JSGeneratorObject::kResumeModeOffset), rdx);
@@ -559,6 +561,30 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   __ jmp(&stepping_prepared);
 }
 
+// static
+void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax    : the value to pass to the generator
+  //  -- rbx    : the JSGeneratorObject to resume
+  //  -- rdx    : the resume mode (tagged)
+  //  -- rsp[0] : return address
+  // -----------------------------------
+  __ AssertGeneratorObject(rbx);
+  Generate_ResumeGenerator(masm, ResumeGeneratorType::kYield);
+}
+
+// static
+void Builtins::Generate_ResumeAwaitedGeneratorTrampoline(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax    : the value to pass to the generator
+  //  -- rbx    : the JSGeneratorObject to resume
+  //  -- rdx    : the resume mode (tagged)
+  //  -- rsp[0] : return address
+  // -----------------------------------
+  __ AssertAsyncGeneratorObject(rbx);
+  Generate_ResumeGenerator(masm, ResumeGeneratorType::kAwait);
+}
+
 static void LeaveInterpreterFrame(MacroAssembler* masm, Register scratch1,
                                   Register scratch2) {
   Register args_count = scratch1;