[debugger] simplify debug stepping.

src/arm64/builtins-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/arm64/frames-arm64.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 708 matching lines @@
   // Store resume mode into generator object.
   __ Str(x2, FieldMemOperand(x1, JSGeneratorObject::kResumeModeOffset));
 
   // Load suspended function and context.
   __ Ldr(cp, FieldMemOperand(x1, JSGeneratorObject::kContextOffset));
   __ Ldr(x4, FieldMemOperand(x1, 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());
-  __ Mov(x10, Operand(step_in_enabled));
-  __ Ldrb(x10, MemOperand(x10));
-  __ CompareAndBranch(x10, Operand(0), ne, &prepare_step_in_if_stepping);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(masm->isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  __ Mov(x10, Operand(last_step_action));
+  __ Ldrsb(x10, MemOperand(x10));
+  __ CompareAndBranch(x10, Operand(StepIn), ge, &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(x10, Operand(debug_suspended_generator));
   __ Ldr(x10, MemOperand(x10));
   __ CompareAndBranch(x10, Operand(x1), eq,
                       &prepare_step_in_suspended_generator);
   __ Bind(&stepping_prepared);
 
@@ skipping 2243 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM