PPC: [debugger] simplify debug stepping.

Port 3e2d60d8

R=yangguo@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2065423002
Cr-Commit-Position: refs/heads/master@{#37007}

src/ppc/builtins-ppc.cc

@@ -722,12 +722,14 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   // 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(ip, Operand(step_in_enabled));
-  __ lbz(ip, MemOperand(ip));
-  __ cmpi(ip, Operand::Zero());
-  __ bne(&prepare_step_in_if_stepping);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(masm->isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  __ mov(ip, Operand(last_step_action));
+  __ LoadByte(ip, MemOperand(ip), r0);
+  __ extsb(ip, ip);
+  __ cmpi(ip, Operand(StepIn));
+  __ bge(&prepare_step_in_if_stepping);
 
   // Flood function if we need to continue stepping in the suspended generator.
 

src/ppc/macro-assembler-ppc.cc

@@ -1386,12 +1386,14 @@ 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(r7, Operand(step_in_enabled));
-  lbz(r7, MemOperand(r7));
-  cmpi(r7, Operand::Zero());
-  beq(&skip_flooding);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  mov(r7, Operand(last_step_action));
+  LoadByte(r7, MemOperand(r7), r0);
+  extsb(r7, r7);
+  cmpi(r7, Operand(StepIn));
+  blt(&skip_flooding);
   {
     FrameScope frame(this,
                      has_frame() ? StackFrame::NONE : StackFrame::INTERNAL);