[debugger] simplify debug stepping.

src/x64/builtins-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 464 matching lines @@
   // Store resume mode into generator object.
   __ movp(FieldOperand(rbx, JSGeneratorObject::kResumeModeOffset), rdx);
 
   // Load suspended function and context.
   __ movp(rsi, FieldOperand(rbx, JSGeneratorObject::kContextOffset));
   __ movp(rdi, FieldOperand(rbx, JSGeneratorObject::kFunctionOffset));
 
   // Flood function if we are stepping.
   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());
-  Operand step_in_enabled_operand = masm->ExternalOperand(step_in_enabled);
-  __ cmpb(step_in_enabled_operand, Immediate(0));
-  __ j(not_equal, &prepare_step_in_if_stepping);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(masm->isolate());
+  Operand last_step_action_operand = masm->ExternalOperand(last_step_action);
+  STATIC_ASSERT(StepFrame > StepIn);
+  __ cmpb(last_step_action_operand, Immediate(StepIn));
+  __ j(greater_equal, &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());
   Operand debug_suspended_generator_operand =
       masm->ExternalOperand(debug_suspended_generator);
   __ cmpp(rbx, debug_suspended_generator_operand);
   __ j(equal, &prepare_step_in_suspended_generator);
   __ bind(&stepping_prepared);
 
@@ skipping 2524 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64