[simulator] remove unused argument field for stop/breaks.

We used to embed a string address as description right after
a stop instruction, which the simulator would read and print.
We removed that a while ago to make the snapshot predictable.

R=petermarshall@chromium.org
BUG=v8:6071

Review-Url: https://codereview.chromium.org/2744503003
Cr-Commit-Position: refs/heads/master@{#43698}

src/arm/assembler-arm.cc

@@ -2282,19 +2282,12 @@ void Assembler::stop(const char* msg, Condition cond, int32_t code) {
 #ifndef __arm__
   DCHECK(code >= kDefaultStopCode);
   {
-    // The Simulator will handle the stop instruction and get the message
-    // address. It expects to find the address just after the svc instruction.
     BlockConstPoolScope block_const_pool(this);
     if (code >= 0) {
       svc(kStopCode + code, cond);
     } else {
       svc(kStopCode + kMaxStopCode, cond);
     }
-    // Do not embed the message string address! We used to do this, but that
-    // made snapshots created from position-independent executable builds
-    // non-deterministic.
-    // TODO(yangguo): remove this field entirely.
-    nop();
   }
 #else  // def __arm__
   if (cond != al) {

src/arm/disasm-arm.cc

@@ -1364,12 +1364,6 @@ int Decoder::DecodeType7(Instruction* instr) {
   if (instr->Bit(24) == 1) {
     if (instr->SvcValue() >= kStopCode) {
       Format(instr, "stop'cond 'svc");
-      out_buffer_pos_ += SNPrintF(
-          out_buffer_ + out_buffer_pos_, "\n  %p  %08x",
-          reinterpret_cast<void*>(instr + Instruction::kInstrSize),
-          *reinterpret_cast<uint32_t*>(instr + Instruction::kInstrSize));
-      // We have decoded 2 * Instruction::kInstrSize bytes.
-      return 2 * Instruction::kInstrSize;
     } else {
       Format(instr, "svc'cond 'svc");
     }

src/arm/simulator-arm.cc

@@ -432,15 +432,12 @@ void ArmDebugger::Debug() {
         PrintF("INEXACT flag: %d;\n", sim_->inexact_vfp_flag_);
       } else if (strcmp(cmd, "stop") == 0) {
         int32_t value;
-        intptr_t stop_pc = sim_->get_pc() - 2 * Instruction::kInstrSize;
+        intptr_t stop_pc = sim_->get_pc() - Instruction::kInstrSize;
         Instruction* stop_instr = reinterpret_cast<Instruction*>(stop_pc);
-        Instruction* msg_address =
-          reinterpret_cast<Instruction*>(stop_pc + Instruction::kInstrSize);
         if ((argc == 2) && (strcmp(arg1, "unstop") == 0)) {
           // Remove the current stop.
           if (sim_->isStopInstruction(stop_instr)) {
             stop_instr->SetInstructionBits(kNopInstr);
-            msg_address->SetInstructionBits(kNopInstr);
           } else {
             PrintF("Not at debugger stop.\n");
           }
@@ -5671,10 +5668,6 @@ void Simulator::InstructionDecode(Instruction* instr) {
         break;
       }
     }
-  // If the instruction is a non taken conditional stop, we need to skip the
-  // inlined message address.
-  } else if (instr->IsStop()) {
-    set_pc(get_pc() + 2 * Instruction::kInstrSize);
   }
   if (!pc_modified_) {
     set_register(pc, reinterpret_cast<int32_t>(instr)

src/mips/assembler-mips.cc

@@ -2020,14 +2020,7 @@ void Assembler::stop(const char* msg, uint32_t code) {
   break_(0x54321);
 #else  // V8_HOST_ARCH_MIPS
   BlockTrampolinePoolFor(2);
-  // The Simulator will handle the stop instruction and get the message address.
-  // On MIPS stop() is just a special kind of break_().
   break_(code, true);
-  // Do not embed the message string address! We used to do this, but that
-  // made snapshots created from position-independent executable builds
-  // non-deterministic.
-  // TODO(yangguo): remove this field entirely.
-  nop();
 #endif
 }
 

src/mips64/assembler-mips64.cc

@@ -2272,14 +2272,7 @@ void Assembler::stop(const char* msg, uint32_t code) {
   break_(0x54321);
 #else  // V8_HOST_ARCH_MIPS
   BlockTrampolinePoolFor(3);
-  // The Simulator will handle the stop instruction and get the message address.
-  // On MIPS stop() is just a special kind of break_().
   break_(code, true);
-  // Do not embed the message string address! We used to do this, but that
-  // made snapshots created from position-independent executable builds
-  // non-deterministic.
-  // TODO(yangguo): remove this field entirely.
-  nop();
 #endif
 }