[debug] implement intuitive semantics for stepping over await call.

src/mips/builtins-mips.cc

Index: src/mips/builtins-mips.cc
diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index 530e8116166a17954bb5b47078a4d722036f467a..54377088e74cc6d4e427e381db6ff5370bc86d71 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -841,20 +841,21 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   __ lw(t0, FieldMemOperand(a1, JSGeneratorObject::kFunctionOffset));
 
   // Flood function if we are stepping.
-  Label skip_flooding;
+  Label prepare_step_in_if_stepping, prepare_step_in_suspended_generator;
+  Label stepping_prepared;
   ExternalReference step_in_enabled =
       ExternalReference::debug_step_in_enabled_address(masm->isolate());
   __ li(t1, Operand(step_in_enabled));
   __ lb(t1, MemOperand(t1));
-  __ Branch(&skip_flooding, eq, t1, Operand(zero_reg));
-  {
-    FrameScope scope(masm, StackFrame::INTERNAL);
-    __ Push(a1, a2, t0);
-    __ CallRuntime(Runtime::kDebugPrepareStepInIfStepping);
-    __ Pop(a1, a2);
-    __ lw(t0, FieldMemOperand(a1, JSGeneratorObject::kFunctionOffset));
-  }
-  __ bind(&skip_flooding);
+  __ Branch(&prepare_step_in_if_stepping, ne, t1, Operand(zero_reg));
+
+  // Flood function if we need to continue stepping in the suspended generator.
+  ExternalReference debug_suspended_generator =
+      ExternalReference::debug_suspended_generator_address(masm->isolate());
+  __ li(t1, Operand(debug_suspended_generator));
+  __ lw(t1, MemOperand(t1));
+  __ Branch(&prepare_step_in_suspended_generator, eq, t1, Operand(zero_reg));
+  __ bind(&stepping_prepared);
 
   // Push receiver.
   __ lw(t1, FieldMemOperand(a1, JSGeneratorObject::kReceiverOffset));
@@ -950,6 +951,26 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
     __ Move(v0, a1);  // Continuation expects generator object in v0.
     __ Jump(a3);
   }
+
+  __ bind(&prepare_step_in_if_stepping);
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    __ Push(a1, a2, t0);
+    __ CallRuntime(Runtime::kDebugPrepareStepInIfStepping);
+    __ Pop(a1, a2);
+  }
+  __ Branch(USE_DELAY_SLOT, &stepping_prepared);
+  __ lw(t0, FieldMemOperand(a1, JSGeneratorObject::kFunctionOffset));
+
+  __ bind(&prepare_step_in_suspended_generator);
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    __ Push(a1, a2);
+    __ CallRuntime(Runtime::kDebugPrepareStepInSuspendedGenerator);
+    __ Pop(a1, a2);
+  }
+  __ Branch(USE_DELAY_SLOT, &stepping_prepared);
+  __ lw(t0, FieldMemOperand(a1, JSGeneratorObject::kFunctionOffset));
 }
 
 static void LeaveInterpreterFrame(MacroAssembler* masm, Register scratch) {