Drops into Simulator Debugger only in a session that is already interactive.

runtime/vm/simulator_mips.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_MIPS)
 
 // Only build the simulator if not compiling for real MIPS hardware.
 #if !defined(HOST_ARCH_MIPS)
 
@@ skipping 201 matching lines @@
 void SimulatorDebugger::RedoBreakpoints() {
   if (sim_->break_pc_ != NULL) {
     sim_->break_pc_->SetInstructionBits(Instr::kBreakPointInstruction);
   }
 }
 
 
 void SimulatorDebugger::Debug() {
   intptr_t last_pc = -1;
   bool done = false;
-  bool decoded = true;
 
 #define COMMAND_SIZE 63
 #define ARG_SIZE 255
 
 #define STR(a) #a
 #define XSTR(a) STR(a)
 
   char cmd[COMMAND_SIZE + 1];
   char arg1[ARG_SIZE + 1];
   char arg2[ARG_SIZE + 1];
 
   // make sure to have a proper terminating character if reaching the limit
   cmd[COMMAND_SIZE] = 0;
   arg1[ARG_SIZE] = 0;
   arg2[ARG_SIZE] = 0;
 
   // Undo all set breakpoints while running in the debugger shell. This will
   // make them invisible to all commands.
   UndoBreakpoints();
 
   while (!done) {
     if (last_pc != sim_->get_pc()) {
       last_pc = sim_->get_pc();
-      decoded = Disassembler::Disassemble(last_pc, last_pc + Instr::kInstrSize);
+      Disassembler::Disassemble(last_pc, last_pc + Instr::kInstrSize);
     }
     char* line = ReadLine("sim> ");
     if (line == NULL) {
-      break;
+      FATAL("ReadLine failed");
     } else {
       // Use sscanf to parse the individual parts of the command line. At the
       // moment no command expects more than two parameters.
       int args = SScanF(line,
                         "%" XSTR(COMMAND_SIZE) "s "
                         "%" XSTR(ARG_SIZE) "s "
                         "%" XSTR(ARG_SIZE) "s",
                         cmd, arg1, arg2);
       if ((strcmp(cmd, "h") == 0) || (strcmp(cmd, "help") == 0)) {
         OS::Print("c/cont -- continue execution\n"
                   "disasm -- disassemble instrs at current pc location\n"
                   "  other variants are:\n"
                   "    disasm <address>\n"
                   "    disasm <address> <number_of_instructions>\n"
                   "  by default 10 instrs are disassembled\n"
                   "del -- delete breakpoints\n"
                   "gdb -- transfer control to gdb\n"
                   "h/help -- print this help string\n"
                   "break <address> -- set break point at specified address\n"
                   "p/print <reg or value or *addr> -- print integer value\n"
                   "pf/printfloat <freg or *addr> -- print float value\n"
                   "po/printobject <*reg or *addr> -- print object\n"
                   "si/stepi -- single step an instruction\n"
                   "unstop -- if current pc is a stop instr make it a nop\n"
                   "q/quit -- Quit the debugger and exit the program\n");
       } else if ((strcmp(cmd, "quit") == 0) || (strcmp(cmd, "q") == 0)) {
         OS::Print("Quitting\n");
         OS::Exit(0);
       } else if ((strcmp(cmd, "si") == 0) || (strcmp(cmd, "stepi") == 0)) {
-        if (decoded) {
-          sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
-        } else {
-          OS::Print("Instruction could not be decoded. Stepping disabled.\n");
-        }
+        sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
       } else if ((strcmp(cmd, "c") == 0) || (strcmp(cmd, "cont") == 0)) {
-        if (decoded) {
-          // Execute the one instruction we broke at with breakpoints disabled.
-          sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
-          // Leave the debugger shell.
-          done = true;
-        } else {
-          OS::Print("Instruction could not be decoded. Cannot continue.\n");
-        }
+        // Execute the one instruction we broke at with breakpoints disabled.
+        sim_->InstructionDecode(reinterpret_cast<Instr*>(sim_->get_pc()));
+        // Leave the debugger shell.
+        done = true;
       } else if ((strcmp(cmd, "p") == 0) || (strcmp(cmd, "print") == 0)) {
         if (args == 2) {
           uint32_t value;
           if (GetValue(arg1, &value)) {
             OS::Print("%s: %u 0x%x\n", arg1, value, value);
           } else {
             OS::Print("%s unrecognized\n", arg1);
           }
         } else {
           OS::Print("print <reg or value or *addr>\n");
@@ skipping 250 matching lines @@
   fregisters_[reg] = value;
 }
 
 
 double Simulator::get_fregister(FRegister reg) const {
   ASSERT((reg >= 0) && (reg < kNumberOfFRegisters));
   return fregisters_[reg];
 }
 
 
+void Simulator::UnimplementedInstruction(Instr* instr) {
+  char buffer[64];
+  snprintf(buffer, sizeof(buffer), "Unimplemented instruction: pc=%p\n", instr);
+  SimulatorDebugger dbg(this);
+  dbg.Stop(instr, buffer);
+  FATAL("Cannot continue execution after unimplemented instruction.");
+}
+
+
 void Simulator::HandleIllegalAccess(uword addr, Instr* instr) {
   uword fault_pc = get_pc();
   // The debugger will not be able to single step past this instruction, but
   // it will be possible to disassemble the code and inspect registers.
   char buffer[128];
   snprintf(buffer, sizeof(buffer),
            "illegal memory access at 0x%"Px", pc=0x%"Px"\n",
            addr, fault_pc);
   SimulatorDebugger dbg(this);
   dbg.Stop(instr, buffer);
@@ skipping 360 matching lines @@
     case XOR: {
       ASSERT(instr->SaField() == 0);
       // Format(instr, "xor 'rd, 'rs, 'rt");
       int32_t rs_val = get_register(instr->RsField());
       int32_t rt_val = get_register(instr->RtField());
       set_register(instr->RdField(), rs_val ^ rt_val);
       break;
     }
     default: {
       OS::PrintErr("DecodeSpecial: 0x%x\n", instr->InstructionBits());
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
 }
 
 
 void Simulator::DecodeSpecial2(Instr* instr) {
   ASSERT(instr->OpcodeField() == SPECIAL2);
   switch (instr->FunctionField()) {
     case CLO: {
@@ skipping 21 matching lines @@
           rs_val <<= 1;
         }
       } else {
         bitcount = 32;
       }
       set_register(instr->RdField(), bitcount);
       break;
     }
     default: {
       OS::PrintErr("DecodeSpecial2: 0x%x\n", instr->InstructionBits());
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
 }
 
 
 void Simulator::InstructionDecode(Instr* instr) {
   switch (instr->OpcodeField()) {
     case SPECIAL: {
       DecodeSpecial(instr);
@@ skipping 129 matching lines @@
       if (Simulator::IsIllegalAddress(addr)) {
         HandleIllegalAccess(addr, instr);
       } else {
         WriteW(addr, rt_val, instr);
       }
       break;
     }
     default: {
       OS::PrintErr("Undecoded instruction: 0x%x at %p\n",
                     instr->InstructionBits(), instr);
-      UNIMPLEMENTED();
+      UnimplementedInstruction(instr);
       break;
     }
   }
   pc_ += Instr::kInstrSize;
 }
 
 
 void Simulator::ExecuteDelaySlot() {
   ASSERT(pc_ != kEndSimulatingPC);
   delay_slot_ = true;
   icount_++;
+  Instr* instr = Instr::At(pc_ + Instr::kInstrSize);
   if (icount_ == FLAG_stop_sim_at) {
-    UNIMPLEMENTED();
+    SimulatorDebugger dbg(this);
+    dbg.Stop(instr, "Instruction count reached");
   }
-  Instr* instr = Instr::At(pc_ + Instr::kInstrSize);
   InstructionDecode(instr);
   delay_slot_ = false;
 }
 
 
 void Simulator::Execute() {
   if (FLAG_stop_sim_at == 0) {
     // Fast version of the dispatch loop without checking whether the simulator
     // should be stopping at a particular executed instruction.
     while (pc_ != kEndSimulatingPC) {
       icount_++;
       Instr* instr = Instr::At(pc_);
-      InstructionDecode(instr);
+      if (IsIllegalAddress(pc_)) {
+        HandleIllegalAccess(pc_, instr);
+      } else {
+        InstructionDecode(instr);
+      }
     }
   } else {
     // FLAG_stop_sim_at is at the non-default value. Stop in the debugger when
     // we reach the particular instruction count.
     while (pc_ != kEndSimulatingPC) {
       icount_++;
+      Instr* instr = Instr::At(pc_);
       if (icount_ == FLAG_stop_sim_at) {
-        UNIMPLEMENTED();
+        SimulatorDebugger dbg(this);
+        dbg.Stop(instr, "Instruction count reached");
       } else {
-        Instr* instr = Instr::At(pc_);
-        InstructionDecode(instr);
+        if (IsIllegalAddress(pc_)) {
+          HandleIllegalAccess(pc_, instr);
+        } else {
+          InstructionDecode(instr);
+        }
       }
     }
   }
 }
 
 
 int64_t Simulator::Call(int32_t entry,
                         int32_t parameter0,
                         int32_t parameter1,
                         int32_t parameter2,
@@ skipping 72 matching lines @@
   // Restore the SP register and return R1:R0.
   set_register(SP, sp_before_call);
   return Utils::LowHighTo64Bits(get_register(V0), get_register(V1));
 }
 
 }  // namespace dart
 
 #endif  // !defined(HOST_ARCH_MIPS)
 
 #endif  // defined TARGET_ARCH_MIPS