S390: [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, bjaideep@ca.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2069193003
Cr-Commit-Position: refs/heads/master@{#37014}

src/s390/builtins-s390.cc

@@ -710,12 +710,13 @@ 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));
-  __ LoadlB(ip, MemOperand(ip));
-  __ CmpP(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));
+  __ LoadB(ip, MemOperand(ip));
+  __ CmpP(ip, Operand(StepIn));
+  __ bge(&prepare_step_in_if_stepping);
 
   // Flood function if we need to continue stepping in the suspended generator.
 

src/s390/macro-assembler-s390.cc

@@ -1309,12 +1309,13 @@ 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(r6, Operand(step_in_enabled));
-  LoadlB(r6, MemOperand(r6));
-  CmpP(r6, Operand::Zero());
-  beq(&skip_flooding);
+  ExternalReference last_step_action =
+      ExternalReference::debug_last_step_action_address(isolate());
+  STATIC_ASSERT(StepFrame > StepIn);
+  mov(r6, Operand(last_step_action));
+  LoadB(r6, MemOperand(r6));
+  CmpP(r6, Operand(StepIn));
+  blt(&skip_flooding);
   {
     FrameScope frame(this,
                      has_frame() ? StackFrame::NONE : StackFrame::INTERNAL);