[debugger] simplify debug stepping.

src/arm64/macro-assembler-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/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 2474 matching lines @@
     }
   }
   Bind(&regular_invoke);
 }
 
 
 void MacroAssembler::FloodFunctionIfStepping(Register fun, Register new_target,
                                              const ParameterCount& expected,
                                              const ParameterCount& actual) {
   Label skip_flooding;
-  ExternalReference step_in_enabled =
-      ExternalReference::debug_step_in_enabled_address(isolate());
-  Mov(x4, Operand(step_in_enabled));
-  ldrb(x4, MemOperand(x4));
-  CompareAndBranch(x4, Operand(0), eq, &skip_flooding);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  Mov(x4, Operand(last_step_action));
+  Ldrsb(x4, MemOperand(x4));
+  CompareAndBranch(x4, Operand(StepIn), lt, &skip_flooding);
   {
     FrameScope frame(this,
                      has_frame() ? StackFrame::NONE : StackFrame::INTERNAL);
     if (expected.is_reg()) {
       SmiTag(expected.reg());
       Push(expected.reg());
     }
     if (actual.is_reg()) {
       SmiTag(actual.reg());
       Push(actual.reg());
@@ skipping 2634 matching lines @@
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64