[debugger] simplify debug stepping.

src/mips64/macro-assembler-mips64.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.
 
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_MIPS64
 
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
@@ skipping 5124 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());
-  li(t0, Operand(step_in_enabled));
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  li(t0, Operand(last_step_action));
   lb(t0, MemOperand(t0));
-  Branch(&skip_flooding, eq, t0, Operand(zero_reg));
+  Branch(&skip_flooding, lt, t0, Operand(StepIn));
   {
     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 1980 matching lines @@
   if (mag.shift > 0) sra(result, result, mag.shift);
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64