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

src/arm/builtins-arm.cc

Index: src/arm/builtins-arm.cc
diff --git a/src/arm/builtins-arm.cc b/src/arm/builtins-arm.cc
index 4d855004944e78f1ae58311f22d5f31725478812..665993bafc05ed6ba13bdcf26825f07dafacf674 100644
--- a/src/arm/builtins-arm.cc
+++ b/src/arm/builtins-arm.cc
@@ -720,21 +720,23 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   __ ldr(r4, FieldMemOperand(r1, 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());
   __ mov(ip, Operand(step_in_enabled));
   __ ldrb(ip, MemOperand(ip));
   __ cmp(ip, Operand(0));
-  __ b(eq, &skip_flooding);
-  {
-    FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
-    __ Push(r1, r2, r4);
-    __ CallRuntime(Runtime::kDebugPrepareStepInIfStepping);
-    __ Pop(r1, r2);
-    __ ldr(r4, FieldMemOperand(r1, JSGeneratorObject::kFunctionOffset));
-  }
-  __ bind(&skip_flooding);
+  __ b(ne, &prepare_step_in_if_stepping);
+
+  // Flood function if we need to continue stepping in the suspended generator.
+  ExternalReference debug_suspended_generator =
+      ExternalReference::debug_suspended_generator_address(masm->isolate());
+  __ mov(ip, Operand(debug_suspended_generator));
+  __ ldr(ip, MemOperand(ip));
+  __ cmp(ip, Operand(r1));
+  __ b(eq, &prepare_step_in_suspended_generator);
+  __ bind(&stepping_prepared);
 
   // Push receiver.
   __ ldr(ip, FieldMemOperand(r1, JSGeneratorObject::kReceiverOffset));
@@ -830,6 +832,26 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
     __ Move(r0, r1);  // Continuation expects generator object in r0.
     __ Jump(r3);
   }
+
+  __ bind(&prepare_step_in_if_stepping);
+  {
+    FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+    __ Push(r1, r2, r4);
+    __ CallRuntime(Runtime::kDebugPrepareStepInIfStepping);
+    __ Pop(r1, r2);
+    __ ldr(r4, FieldMemOperand(r1, JSGeneratorObject::kFunctionOffset));
+  }
+  __ b(&stepping_prepared);
+
+  __ bind(&prepare_step_in_suspended_generator);
+  {
+    FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+    __ Push(r1, r2);
+    __ CallRuntime(Runtime::kDebugPrepareStepInSuspendedGenerator);
+    __ Pop(r1, r2);
+    __ ldr(r4, FieldMemOperand(r1, JSGeneratorObject::kFunctionOffset));
+  }
+  __ b(&stepping_prepared);
 }
 
 void Builtins::Generate_ConstructedNonConstructable(MacroAssembler* masm) {