Use a breakpoint instruction for a stop message on arm instead of

runtime/vm/simulator_arm.cc

Index: runtime/vm/simulator_arm.cc
===================================================================
--- runtime/vm/simulator_arm.cc	(revision 45360)
+++ runtime/vm/simulator_arm.cc	(working copy)
@@ -1506,7 +1506,7 @@
 void Simulator::SupervisorCall(Instr* instr) {
   int svc = instr->SvcField();
   switch (svc) {
-    case kRedirectionSvcCode: {
+    case Instr::kSimulatorRedirectCode: {
       SimulatorSetjmpBuffer buffer(this);
 
       if (!setjmp(buffer.buffer_)) {
@@ -1627,19 +1627,11 @@
 
       break;
     }
-    case kBreakpointSvcCode: {
+    case Instr::kSimulatorBreakCode: {
       SimulatorDebugger dbg(this);
       dbg.Stop(instr, "breakpoint");
       break;
     }
-    case kStopMessageSvcCode: {
-      SimulatorDebugger dbg(this);
-      const char* message = *reinterpret_cast<const char**>(
-          reinterpret_cast<intptr_t>(instr) - Instr::kInstrSize);
-      set_pc(get_pc() + Instr::kInstrSize);
-      dbg.Stop(instr, message);
-      break;
-    }
     default: {
       UNREACHABLE();
       break;
@@ -1696,10 +1688,18 @@
           if ((instr->Bits(21, 2) == 0x1) && (instr->ConditionField() == AL)) {
             // Format(instr, "bkpt #'imm12_4");
             SimulatorDebugger dbg(this);
-            set_pc(get_pc() + Instr::kInstrSize);
-            char buffer[32];
-            snprintf(buffer, sizeof(buffer), "bkpt #0x%x", instr->BkptField());
-            dbg.Stop(instr, buffer);
+            int32_t imm = instr->BkptField();
+            if (imm == Instr::kStopMessageCode) {
+              const char* message = *reinterpret_cast<const char**>(
+                  reinterpret_cast<intptr_t>(instr) - Instr::kInstrSize);
+              set_pc(get_pc() + Instr::kInstrSize);
+              dbg.Stop(instr, message);
+            } else {
+              char buffer[32];
+              snprintf(buffer, sizeof(buffer), "bkpt #0x%x", imm);
+              set_pc(get_pc() + Instr::kInstrSize);
+              dbg.Stop(instr, buffer);
+            }
           } else {
              // Format(instr, "smc'cond");
             UnimplementedInstruction(instr);