Contribution of PowerPC port.

src/ppc/simulator-ppc.cc

+// Copyright 2012 the V8 project authors. All rights reserved.
+//
+// Copyright IBM Corp. 2012, 2013. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <cmath>
+
+#include "src/v8.h"
+
+#if V8_TARGET_ARCH_PPC
+
+#include "src/assembler.h"
+#include "src/codegen.h"
+#include "src/disasm.h"
+#include "src/ppc/constants-ppc.h"
+#include "src/ppc/frames-ppc.h"
+#include "src/ppc/simulator-ppc.h"
+
+#if defined(USE_SIMULATOR)
+
+// Only build the simulator if not compiling for real PPC hardware.
+namespace v8 {
+namespace internal {
+
+// This macro provides a platform independent use of sscanf. The reason for
+// SScanF not being implemented in a platform independent way through
+// ::v8::internal::OS in the same way as SNPrintF is that the
+// Windows C Run-Time Library does not provide vsscanf.
+#define SScanF sscanf  // NOLINT
+
+// The PPCDebugger class is used by the simulator while debugging simulated
+// PowerPC code.
+class PPCDebugger {
+ public:
+  explicit PPCDebugger(Simulator* sim) : sim_(sim) { }
+  ~PPCDebugger();
+
+  void Stop(Instruction* instr);
+  void Info(Instruction* instr);
+  void Debug();
+
+ private:
+  static const Instr kBreakpointInstr = (TWI | 0x1f * B21);
+  static const Instr kNopInstr = (ORI);  // ori, 0,0,0
+
+  Simulator* sim_;
+
+  intptr_t GetRegisterValue(int regnum);
+  double GetRegisterPairDoubleValue(int regnum);
+  double GetFPDoubleRegisterValue(int regnum);
+  bool GetValue(const char* desc, intptr_t* value);
+  bool GetFPDoubleValue(const char* desc, double* value);
+
+  // Set or delete a breakpoint. Returns true if successful.
+  bool SetBreakpoint(Instruction* break_pc);
+  bool DeleteBreakpoint(Instruction* break_pc);
+
+  // Undo and redo all breakpoints. This is needed to bracket disassembly and
+  // execution to skip past breakpoints when run from the debugger.
+  void UndoBreakpoints();
+  void RedoBreakpoints();
+};
+
+
+PPCDebugger::~PPCDebugger() {
+}
+
+
+
+#ifdef GENERATED_CODE_COVERAGE
+static FILE* coverage_log = NULL;
+
+
+static void InitializeCoverage() {
+  char* file_name = getenv("V8_GENERATED_CODE_COVERAGE_LOG");
+  if (file_name != NULL) {
+    coverage_log = fopen(file_name, "aw+");
+  }
+}
+
+
+void PPCDebugger::Stop(Instruction* instr) {  // roohack need to fix for PPC
+  // Get the stop code.
+  uint32_t code = instr->SvcValue() & kStopCodeMask;
+  // Retrieve the encoded address, which comes just after this stop.
+  char** msg_address =
+    reinterpret_cast<char**>(sim_->get_pc() + Instruction::kInstrSize);
+  char* msg = *msg_address;
+  ASSERT(msg != NULL);
+
+  // Update this stop description.
+  if (isWatchedStop(code) && !watched_stops_[code].desc) {
+    watched_stops_[code].desc = msg;
+  }
+
+  if (strlen(msg) > 0) {
+    if (coverage_log != NULL) {
+      fprintf(coverage_log, "%s\n", msg);
+      fflush(coverage_log);
+    }
+    // Overwrite the instruction and address with nops.
+    instr->SetInstructionBits(kNopInstr);
+    reinterpret_cast<Instruction*>(msg_address)->SetInstructionBits(kNopInstr);
+  }
+  sim_->set_pc(sim_->get_pc() + Instruction::kInstrSize + kPointerSize);
+}
+
+#else  // ndef GENERATED_CODE_COVERAGE
+
+static void InitializeCoverage() {
+}
+
+
+void PPCDebugger::Stop(Instruction* instr) {
+  // Get the stop code.
+  // use of kStopCodeMask not right on PowerPC
+  uint32_t code = instr->SvcValue() & kStopCodeMask;
+  // Retrieve the encoded address, which comes just after this stop.
+  char* msg = *reinterpret_cast<char**>(sim_->get_pc()
+                                        + Instruction::kInstrSize);
+  // Update this stop description.
+  if (sim_->isWatchedStop(code) && !sim_->watched_stops_[code].desc) {
+    sim_->watched_stops_[code].desc = msg;
+  }
+  // Print the stop message and code if it is not the default code.
+  if (code != kMaxStopCode) {
+    PrintF("Simulator hit stop %u: %s\n", code, msg);
+  } else {
+    PrintF("Simulator hit %s\n", msg);
+  }
+  sim_->set_pc(sim_->get_pc() + Instruction::kInstrSize + kPointerSize);
+  Debug();
+}
+#endif
+
+
+void PPCDebugger::Info(Instruction* instr) {
+  // Retrieve the encoded address immediately following the Info breakpoint.
+  char* msg = *reinterpret_cast<char**>(sim_->get_pc()
+                                        + Instruction::kInstrSize);
+  PrintF("Simulator info %s\n", msg);
+  sim_->set_pc(sim_->get_pc() + Instruction::kInstrSize + kPointerSize);
+}
+
+
+intptr_t PPCDebugger::GetRegisterValue(int regnum) {
+  return sim_->get_register(regnum);
+}
+
+
+double PPCDebugger::GetRegisterPairDoubleValue(int regnum) {
+  return sim_->get_double_from_register_pair(regnum);
+}
+
+
+double PPCDebugger::GetFPDoubleRegisterValue(int regnum) {
+  return sim_->get_double_from_d_register(regnum);
+}
+
+
+bool PPCDebugger::GetValue(const char* desc, intptr_t* value) {
+  int regnum = Registers::Number(desc);
+  if (regnum != kNoRegister) {
+    *value = GetRegisterValue(regnum);
+    return true;
+  } else {
+    if (strncmp(desc, "0x", 2) == 0) {
+      return SScanF(desc + 2, "%" V8PRIxPTR,
+                    reinterpret_cast<uintptr_t*>(value)) == 1;
+    } else {
+      return SScanF(desc, "%" V8PRIuPTR,
+                    reinterpret_cast<uintptr_t*>(value)) == 1;
+    }
+  }
+  return false;
+}
+
+
+bool PPCDebugger::GetFPDoubleValue(const char* desc, double* value) {
+  int regnum = FPRegisters::Number(desc);
+  if (regnum != kNoRegister) {
+    *value = sim_->get_double_from_d_register(regnum);
+    return true;
+  }
+  return false;
+}
+
+
+bool PPCDebugger::SetBreakpoint(Instruction* break_pc) {
+  // Check if a breakpoint can be set. If not return without any side-effects.
+  if (sim_->break_pc_ != NULL) {
+    return false;
+  }
+
+  // Set the breakpoint.
+  sim_->break_pc_ = break_pc;
+  sim_->break_instr_ = break_pc->InstructionBits();
+  // Not setting the breakpoint instruction in the code itself. It will be set
+  // when the debugger shell continues.
+  return true;
+}
+
+
+bool PPCDebugger::DeleteBreakpoint(Instruction* break_pc) {
+  if (sim_->break_pc_ != NULL) {
+    sim_->break_pc_->SetInstructionBits(sim_->break_instr_);
+  }
+
+  sim_->break_pc_ = NULL;
+  sim_->break_instr_ = 0;
+  return true;
+}
+
+
+void PPCDebugger::UndoBreakpoints() {
+  if (sim_->break_pc_ != NULL) {
+    sim_->break_pc_->SetInstructionBits(sim_->break_instr_);
+  }
+}
+
+
+void PPCDebugger::RedoBreakpoints() {
+  if (sim_->break_pc_ != NULL) {
+    sim_->break_pc_->SetInstructionBits(kBreakpointInstr);
+  }
+}
+
+
+void PPCDebugger::Debug() {
+  intptr_t last_pc = -1;
+  bool done = false;
+
+#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];
+  char* argv[3] = { cmd, arg1, arg2 };
+
+  // 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();
+  // Disable tracing while simulating
+  bool trace=::v8::internal::FLAG_trace_sim;
+  ::v8::internal::FLAG_trace_sim = false;
+
+  while (!done && !sim_->has_bad_pc()) {
+    if (last_pc != sim_->get_pc()) {
+      disasm::NameConverter converter;
+      disasm::Disassembler dasm(converter);
+      // use a reasonably large buffer
+      v8::internal::EmbeddedVector<char, 256> buffer;
+      dasm.InstructionDecode(buffer,
+                             reinterpret_cast<byte*>(sim_->get_pc()));
+      PrintF("  0x%08" V8PRIxPTR "  %s\n", sim_->get_pc(), buffer.start());
+      last_pc = sim_->get_pc();
+    }
+    char* line = ReadLine("sim> ");
+    if (line == NULL) {
+      break;
+    } else {
+      char* last_input = sim_->last_debugger_input();
+      if (strcmp(line, "\n") == 0 && last_input != NULL) {
+        line = last_input;
+      } else {
+        // Ownership is transferred to sim_;
+        sim_->set_last_debugger_input(line);
+      }
+      // Use sscanf to parse the individual parts of the command line. At the
+      // moment no command expects more than two parameters.
+      int argc = SScanF(line,
+                        "%" XSTR(COMMAND_SIZE) "s "
+                        "%" XSTR(ARG_SIZE) "s "
+                        "%" XSTR(ARG_SIZE) "s",
+                        cmd, arg1, arg2);
+      if ((strcmp(cmd, "si") == 0) || (strcmp(cmd, "stepi") == 0)) {
+        intptr_t value;
+
+        // If at a breakpoint, proceed past it.
+        if ((reinterpret_cast<Instruction*>(sim_->get_pc()))->InstructionBits()
+             == 0x7d821008) {
+          sim_->set_pc(sim_->get_pc() + Instruction::kInstrSize);
+        } else {
+          sim_->ExecuteInstruction(
+                  reinterpret_cast<Instruction*>(sim_->get_pc()));
+        }
+
+        if (argc == 2 && last_pc != sim_->get_pc() &&
+                            GetValue(arg1, &value)) {
+          for (int i = 1; i < value; i++) {
+            disasm::NameConverter converter;
+            disasm::Disassembler dasm(converter);
+            // use a reasonably large buffer
+            v8::internal::EmbeddedVector<char, 256> buffer;
+            dasm.InstructionDecode(buffer,
+                                   reinterpret_cast<byte*>(sim_->get_pc()));
+            PrintF("  0x%08" V8PRIxPTR "  %s\n", sim_->get_pc(),
+                   buffer.start());
+            sim_->ExecuteInstruction(
+                    reinterpret_cast<Instruction*>(sim_->get_pc()));
+          }
+        }
+      } else if ((strcmp(cmd, "c") == 0) || (strcmp(cmd, "cont") == 0)) {
+        // If at a breakpoint, proceed past it.
+        if ((reinterpret_cast<Instruction*>(sim_->get_pc()))->InstructionBits()
+             == 0x7d821008) {
+          sim_->set_pc(sim_->get_pc() + Instruction::kInstrSize);
+        } else {
+          // Execute the one instruction we broke at with breakpoints disabled.
+          sim_->ExecuteInstruction(
+                  reinterpret_cast<Instruction*>(sim_->get_pc()));
+        }
+        // Leave the debugger shell.
+        done = true;
+      } else if ((strcmp(cmd, "p") == 0) || (strcmp(cmd, "print") == 0)) {
+        if (argc == 2 || (argc == 3 && strcmp(arg2, "fp") == 0)) {
+          intptr_t value;
+          double dvalue;
+          if (strcmp(arg1, "all") == 0) {
+            for (int i = 0; i < kNumRegisters; i++) {
+              value = GetRegisterValue(i);
+              PrintF("    %3s: %08" V8PRIxPTR, Registers::Name(i), value);
+              if ((argc == 3 && strcmp(arg2, "fp") == 0) &&
+                  i < 8 &&
+                  (i % 2) == 0) {
+                dvalue = GetRegisterPairDoubleValue(i);
+                PrintF(" (%f)\n", dvalue);
+              } else if (i != 0 && !((i+1) & 3)) {
+                PrintF("\n");
+              }
+            }
+            PrintF("  pc: %08" V8PRIxPTR "  lr: %08" V8PRIxPTR "  "
+                   "ctr: %08" V8PRIxPTR "  xer: %08x  cr: %08x\n",
+                   sim_->special_reg_pc_, sim_->special_reg_lr_,
+                   sim_->special_reg_ctr_, sim_->special_reg_xer_,
+                   sim_->condition_reg_);
+          } else if (strcmp(arg1, "alld") == 0) {
+            for (int i = 0; i < kNumRegisters; i++) {
+              value = GetRegisterValue(i);
+              PrintF("     %3s: %08" V8PRIxPTR
+                     " %11" V8PRIdPTR, Registers::Name(i), value, value);
+              if ((argc == 3 && strcmp(arg2, "fp") == 0) &&
+                  i < 8 &&
+                  (i % 2) == 0) {
+                dvalue = GetRegisterPairDoubleValue(i);
+                PrintF(" (%f)\n", dvalue);
+              } else if (!((i+1) % 2)) {
+                PrintF("\n");
+              }
+            }
+            PrintF("   pc: %08" V8PRIxPTR "  lr: %08" V8PRIxPTR "  "
+                   "ctr: %08" V8PRIxPTR "  xer: %08x  cr: %08x\n",
+                   sim_->special_reg_pc_, sim_->special_reg_lr_,
+                   sim_->special_reg_ctr_, sim_->special_reg_xer_,
+                   sim_->condition_reg_);
+          } else if (strcmp(arg1, "allf") == 0) {
+            for (int i = 0; i < DoubleRegister::NumRegisters(); i++) {
+              dvalue = GetFPDoubleRegisterValue(i);
+              uint64_t as_words = BitCast<uint64_t>(dvalue);
+              PrintF("%3s: %f 0x%08x %08x\n",
+                     FPRegisters::Name(i),
+                     dvalue,
+                     static_cast<uint32_t>(as_words >> 32),
+                     static_cast<uint32_t>(as_words & 0xffffffff));
+            }
+          } else if (arg1[0] == 'r' &&
+                      (arg1[1] >= '0' && arg1[1] <= '9' &&
+                        (arg1[2] == '\0' ||
+                          (arg1[2] >= '0' && arg1[2] <= '9'
+                            && arg1[3] == '\0')))) {
+              int regnum = strtoul(&arg1[1], 0, 10);
+              if (regnum != kNoRegister) {
+                value = GetRegisterValue(regnum);
+                PrintF("%s: 0x%08" V8PRIxPTR " %" V8PRIdPTR "\n",
+                       arg1, value, value);
+              } else {
+                PrintF("%s unrecognized\n", arg1);
+              }
+          } else {
+            if (GetValue(arg1, &value)) {
+              PrintF("%s: 0x%08" V8PRIxPTR " %" V8PRIdPTR "\n",
+                     arg1, value, value);
+            } else if (GetFPDoubleValue(arg1, &dvalue)) {
+              uint64_t as_words = BitCast<uint64_t>(dvalue);
+              PrintF("%s: %f 0x%08x %08x\n",
+                     arg1,
+                     dvalue,
+                     static_cast<uint32_t>(as_words >> 32),
+                     static_cast<uint32_t>(as_words & 0xffffffff));
+            } else {
+              PrintF("%s unrecognized\n", arg1);
+            }
+          }
+        } else {
+          PrintF("print <register>\n");
+        }
+      } else if ((strcmp(cmd, "po") == 0)
+                 || (strcmp(cmd, "printobject") == 0)) {
+        if (argc == 2) {
+          intptr_t value;
+          OFStream os(stdout);
+          if (GetValue(arg1, &value)) {
+            Object* obj = reinterpret_cast<Object*>(value);
+            os << arg1 << ": \n";
+#ifdef DEBUG
+            obj->Print(os);
+            os << "\n";
+#else
+            os << Brief(obj) << "\n";
+#endif
+          } else {
+            os << arg1 << " unrecognized\n";
+          }
+        } else {
+          PrintF("printobject <value>\n");
+        }
+      } else if (strcmp(cmd, "setpc") == 0) {
+        intptr_t value;
+
+        if (!GetValue(arg1, &value)) {
+          PrintF("%s unrecognized\n", arg1);
+          continue;
+        }
+        sim_->set_pc(value);
+      } else if (strcmp(cmd, "stack") == 0 || strcmp(cmd, "mem") == 0) {
+        intptr_t* cur = NULL;
+        intptr_t* end = NULL;
+        int next_arg = 1;
+
+        if (strcmp(cmd, "stack") == 0) {
+          cur = reinterpret_cast<intptr_t*>(sim_->get_register(Simulator::sp));
+        } else {  // "mem"
+          intptr_t value;
+          if (!GetValue(arg1, &value)) {
+            PrintF("%s unrecognized\n", arg1);
+            continue;
+          }
+          cur = reinterpret_cast<intptr_t*>(value);
+          next_arg++;
+        }
+
+        intptr_t words;  // likely inaccurate variable name for 64bit
+        if (argc == next_arg) {
+          words = 10;
+        } else {
+          if (!GetValue(argv[next_arg], &words)) {
+            words = 10;
+          }
+        }
+        end = cur + words;
+
+        while (cur < end) {
+          PrintF("  0x%08" V8PRIxPTR ":  0x%08" V8PRIxPTR " %10" V8PRIdPTR,
+                 reinterpret_cast<intptr_t>(cur), *cur, *cur);
+          HeapObject* obj = reinterpret_cast<HeapObject*>(*cur);
+          intptr_t value = *cur;
+          Heap* current_heap = v8::internal::Isolate::Current()->heap();
+          if (((value & 1) == 0) || current_heap->Contains(obj)) {
+            PrintF(" (");
+            if ((value & 1) == 0) {
+              PrintF("smi %d", PlatformSmiTagging::SmiToInt(obj));
+            } else {
+              obj->ShortPrint();
+            }
+            PrintF(")");
+          }
+          PrintF("\n");
+          cur++;
+        }
+      } else if (strcmp(cmd, "disasm") == 0 || strcmp(cmd, "di") == 0) {
+        disasm::NameConverter converter;
+        disasm::Disassembler dasm(converter);
+        // use a reasonably large buffer
+        v8::internal::EmbeddedVector<char, 256> buffer;
+
+        byte* prev = NULL;
+        byte* cur = NULL;
+        byte* end = NULL;
+
+        if (argc == 1) {
+          cur = reinterpret_cast<byte*>(sim_->get_pc());
+          end = cur + (10 * Instruction::kInstrSize);
+        } else if (argc == 2) {
+          int regnum = Registers::Number(arg1);
+          if (regnum != kNoRegister || strncmp(arg1, "0x", 2) == 0) {
+            // The argument is an address or a register name.
+            intptr_t value;
+            if (GetValue(arg1, &value)) {
+              cur = reinterpret_cast<byte*>(value);
+              // Disassemble 10 instructions at <arg1>.
+              end = cur + (10 * Instruction::kInstrSize);
+            }
+          } else {
+            // The argument is the number of instructions.
+            intptr_t value;
+            if (GetValue(arg1, &value)) {
+              cur = reinterpret_cast<byte*>(sim_->get_pc());
+              // Disassemble <arg1> instructions.
+              end = cur + (value * Instruction::kInstrSize);
+            }
+          }
+        } else {
+          intptr_t value1;
+          intptr_t value2;
+          if (GetValue(arg1, &value1) && GetValue(arg2, &value2)) {
+            cur = reinterpret_cast<byte*>(value1);
+            end = cur + (value2 * Instruction::kInstrSize);
+          }
+        }
+
+        while (cur < end) {
+          prev = cur;
+          cur += dasm.InstructionDecode(buffer, cur);
+          PrintF("  0x%08" V8PRIxPTR "  %s\n",
+                 reinterpret_cast<intptr_t>(prev), buffer.start());
+        }
+      } else if (strcmp(cmd, "gdb") == 0) {
+        PrintF("relinquishing control to gdb\n");
+        v8::base::OS::DebugBreak();
+        PrintF("regaining control from gdb\n");
+      } else if (strcmp(cmd, "break") == 0) {
+        if (argc == 2) {
+          intptr_t value;
+          if (GetValue(arg1, &value)) {
+            if (!SetBreakpoint(reinterpret_cast<Instruction*>(value))) {
+              PrintF("setting breakpoint failed\n");
+            }
+          } else {
+            PrintF("%s unrecognized\n", arg1);
+          }
+        } else {
+          PrintF("break <address>\n");
+        }
+      } else if (strcmp(cmd, "del") == 0) {
+        if (!DeleteBreakpoint(NULL)) {
+          PrintF("deleting breakpoint failed\n");
+        }
+      } else if (strcmp(cmd, "cr") == 0) {
+        PrintF("Condition reg: %08x\n", sim_->condition_reg_);
+      } else if (strcmp(cmd, "lr") == 0) {
+        PrintF("Link reg: %08" V8PRIxPTR "\n", sim_->special_reg_lr_);
+      } else if (strcmp(cmd, "ctr") == 0) {
+        PrintF("Ctr reg: %08" V8PRIxPTR "\n", sim_->special_reg_ctr_);
+      } else if (strcmp(cmd, "xer") == 0) {
+        PrintF("XER: %08x\n", sim_->special_reg_xer_);
+      } else if (strcmp(cmd, "fpscr") == 0) {
+        PrintF("FPSCR: %08x\n", sim_->fp_condition_reg_);
+      } else if (strcmp(cmd, "stop") == 0) {
+        intptr_t value;
+        intptr_t stop_pc = sim_->get_pc() -
+                             (Instruction::kInstrSize + kPointerSize);
+        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");
+          }
+        } else if (argc == 3) {
+          // Print information about all/the specified breakpoint(s).
+          if (strcmp(arg1, "info") == 0) {
+            if (strcmp(arg2, "all") == 0) {
+              PrintF("Stop information:\n");
+              for (uint32_t i = 0; i < sim_->kNumOfWatchedStops; i++) {
+                sim_->PrintStopInfo(i);
+              }
+            } else if (GetValue(arg2, &value)) {
+              sim_->PrintStopInfo(value);
+            } else {
+              PrintF("Unrecognized argument.\n");
+            }
+          } else if (strcmp(arg1, "enable") == 0) {
+            // Enable all/the specified breakpoint(s).
+            if (strcmp(arg2, "all") == 0) {
+              for (uint32_t i = 0; i < sim_->kNumOfWatchedStops; i++) {
+                sim_->EnableStop(i);
+              }
+            } else if (GetValue(arg2, &value)) {
+              sim_->EnableStop(value);
+            } else {
+              PrintF("Unrecognized argument.\n");
+            }
+          } else if (strcmp(arg1, "disable") == 0) {
+            // Disable all/the specified breakpoint(s).
+            if (strcmp(arg2, "all") == 0) {
+              for (uint32_t i = 0; i < sim_->kNumOfWatchedStops; i++) {
+                sim_->DisableStop(i);
+              }
+            } else if (GetValue(arg2, &value)) {
+              sim_->DisableStop(value);
+            } else {
+              PrintF("Unrecognized argument.\n");
+            }
+          }
+        } else {
+          PrintF("Wrong usage. Use help command for more information.\n");
+        }
+      } else if ((strcmp(cmd, "t") == 0) || strcmp(cmd, "trace") == 0) {
+        ::v8::internal::FLAG_trace_sim = !::v8::internal::FLAG_trace_sim;
+        PrintF("Trace of executed instructions is %s\n",
+               ::v8::internal::FLAG_trace_sim ? "on" : "off");
+      } else if ((strcmp(cmd, "h") == 0) || (strcmp(cmd, "help") == 0)) {
+        PrintF("cont\n");
+        PrintF("  continue execution (alias 'c')\n");
+        PrintF("stepi [num instructions]\n");
+        PrintF("  step one/num instruction(s) (alias 'si')\n");
+        PrintF("print <register>\n");
+        PrintF("  print register content (alias 'p')\n");
+        PrintF("  use register name 'all' to display all integer registers\n");
+        PrintF("  use register name 'alld' to display integer registers "\
+               "with decimal values\n");
+        PrintF("  use register name 'rN' to display register number 'N'\n");
+        PrintF("  add argument 'fp' to print register pair double values\n");
+        PrintF("  use register name 'allf' to display floating-point "\
+               "registers\n");
+        PrintF("printobject <register>\n");
+        PrintF("  print an object from a register (alias 'po')\n");
+        PrintF("cr\n");
+        PrintF("  print condition register\n");
+        PrintF("lr\n");
+        PrintF("  print link register\n");
+        PrintF("ctr\n");
+        PrintF("  print ctr register\n");
+        PrintF("xer\n");
+        PrintF("  print XER\n");
+        PrintF("fpscr\n");
+        PrintF("  print FPSCR\n");
+        PrintF("stack [<num words>]\n");
+        PrintF("  dump stack content, default dump 10 words)\n");
+        PrintF("mem <address> [<num words>]\n");
+        PrintF("  dump memory content, default dump 10 words)\n");
+        PrintF("disasm [<instructions>]\n");
+        PrintF("disasm [<address/register>]\n");
+        PrintF("disasm [[<address/register>] <instructions>]\n");
+        PrintF("  disassemble code, default is 10 instructions\n");
+        PrintF("  from pc (alias 'di')\n");
+        PrintF("gdb\n");
+        PrintF("  enter gdb\n");
+        PrintF("break <address>\n");
+        PrintF("  set a break point on the address\n");
+        PrintF("del\n");
+        PrintF("  delete the breakpoint\n");
+        PrintF("trace (alias 't')\n");
+        PrintF("  toogle the tracing of all executed statements\n");
+        PrintF("stop feature:\n");
+        PrintF("  Description:\n");
+        PrintF("    Stops are debug instructions inserted by\n");
+        PrintF("    the Assembler::stop() function.\n");
+        PrintF("    When hitting a stop, the Simulator will\n");
+        PrintF("    stop and and give control to the PPCDebugger.\n");
+        PrintF("    The first %d stop codes are watched:\n",
+               Simulator::kNumOfWatchedStops);
+        PrintF("    - They can be enabled / disabled: the Simulator\n");
+        PrintF("      will / won't stop when hitting them.\n");
+        PrintF("    - The Simulator keeps track of how many times they \n");
+        PrintF("      are met. (See the info command.) Going over a\n");
+        PrintF("      disabled stop still increases its counter. \n");
+        PrintF("  Commands:\n");
+        PrintF("    stop info all/<code> : print infos about number <code>\n");
+        PrintF("      or all stop(s).\n");
+        PrintF("    stop enable/disable all/<code> : enables / disables\n");
+        PrintF("      all or number <code> stop(s)\n");
+        PrintF("    stop unstop\n");
+        PrintF("      ignore the stop instruction at the current location\n");
+        PrintF("      from now on\n");
+      } else {
+        PrintF("Unknown command: %s\n", cmd);
+      }
+    }
+  }
+
+  // Add all the breakpoints back to stop execution and enter the debugger
+  // shell when hit.
+  RedoBreakpoints();
+  // Restore tracing
+  ::v8::internal::FLAG_trace_sim = trace;
+
+#undef COMMAND_SIZE
+#undef ARG_SIZE
+
+#undef STR
+#undef XSTR
+}
+
+
+static bool ICacheMatch(void* one, void* two) {
+  ASSERT((reinterpret_cast<intptr_t>(one) & CachePage::kPageMask) == 0);
+  ASSERT((reinterpret_cast<intptr_t>(two) & CachePage::kPageMask) == 0);
+  return one == two;
+}
+
+
+static uint32_t ICacheHash(void* key) {
+  return static_cast<uint32_t>(reinterpret_cast<uintptr_t>(key)) >> 2;
+}
+
+
+static bool AllOnOnePage(uintptr_t start, int size) {
+  intptr_t start_page = (start & ~CachePage::kPageMask);
+  intptr_t end_page = ((start + size) & ~CachePage::kPageMask);
+  return start_page == end_page;
+}
+
+
+void Simulator::set_last_debugger_input(char* input) {
+  DeleteArray(last_debugger_input_);
+  last_debugger_input_ = input;
+}
+
+
+void Simulator::FlushICache(v8::internal::HashMap* i_cache,
+                            void* start_addr,
+                            size_t size) {
+  intptr_t start = reinterpret_cast<intptr_t>(start_addr);
+  int intra_line = (start & CachePage::kLineMask);
+  start -= intra_line;
+  size += intra_line;
+  size = ((size - 1) | CachePage::kLineMask) + 1;
+  int offset = (start & CachePage::kPageMask);
+  while (!AllOnOnePage(start, size - 1)) {
+    int bytes_to_flush = CachePage::kPageSize - offset;
+    FlushOnePage(i_cache, start, bytes_to_flush);
+    start += bytes_to_flush;
+    size -= bytes_to_flush;
+    ASSERT_EQ(0, static_cast<int>(start & CachePage::kPageMask));
+    offset = 0;
+  }
+  if (size != 0) {
+    FlushOnePage(i_cache, start, size);
+  }
+}
+
+
+CachePage* Simulator::GetCachePage(v8::internal::HashMap* i_cache, void* page) {
+  v8::internal::HashMap::Entry* entry = i_cache->Lookup(page,
+                                                        ICacheHash(page),
+                                                        true);
+  if (entry->value == NULL) {
+    CachePage* new_page = new CachePage();
+    entry->value = new_page;
+  }
+  return reinterpret_cast<CachePage*>(entry->value);
+}
+
+
+// Flush from start up to and not including start + size.
+void Simulator::FlushOnePage(v8::internal::HashMap* i_cache,
+                             intptr_t start,
+                             int size) {
+  ASSERT(size <= CachePage::kPageSize);
+  ASSERT(AllOnOnePage(start, size - 1));
+  ASSERT((start & CachePage::kLineMask) == 0);
+  ASSERT((size & CachePage::kLineMask) == 0);
+  void* page = reinterpret_cast<void*>(start & (~CachePage::kPageMask));
+  int offset = (start & CachePage::kPageMask);
+  CachePage* cache_page = GetCachePage(i_cache, page);
+  char* valid_bytemap = cache_page->ValidityByte(offset);
+  memset(valid_bytemap, CachePage::LINE_INVALID, size >> CachePage::kLineShift);
+}
+
+
+void Simulator::CheckICache(v8::internal::HashMap* i_cache,
+                            Instruction* instr) {
+  intptr_t address = reinterpret_cast<intptr_t>(instr);
+  void* page = reinterpret_cast<void*>(address & (~CachePage::kPageMask));
+  void* line = reinterpret_cast<void*>(address & (~CachePage::kLineMask));
+  int offset = (address & CachePage::kPageMask);
+  CachePage* cache_page = GetCachePage(i_cache, page);
+  char* cache_valid_byte = cache_page->ValidityByte(offset);
+  bool cache_hit = (*cache_valid_byte == CachePage::LINE_VALID);
+  char* cached_line = cache_page->CachedData(offset & ~CachePage::kLineMask);
+  if (cache_hit) {
+    // Check that the data in memory matches the contents of the I-cache.
+    CHECK_EQ(0, memcmp(reinterpret_cast<void*>(instr),
+                       cache_page->CachedData(offset),
+                       Instruction::kInstrSize));
+  } else {
+    // Cache miss.  Load memory into the cache.
+    memcpy(cached_line, line, CachePage::kLineLength);
+    *cache_valid_byte = CachePage::LINE_VALID;
+  }
+}
+
+
+void Simulator::Initialize(Isolate* isolate) {
+  if (isolate->simulator_initialized()) return;
+  isolate->set_simulator_initialized(true);
+  ::v8::internal::ExternalReference::set_redirector(isolate,
+                                                    &RedirectExternalReference);
+}
+
+
+Simulator::Simulator(Isolate* isolate) : isolate_(isolate) {
+  i_cache_ = isolate_->simulator_i_cache();
+  if (i_cache_ == NULL) {
+    i_cache_ = new v8::internal::HashMap(&ICacheMatch);
+    isolate_->set_simulator_i_cache(i_cache_);
+  }
+  Initialize(isolate);
+  // Set up simulator support first. Some of this information is needed to
+  // setup the architecture state.
+#if V8_TARGET_ARCH_PPC64
+  size_t stack_size = 2 * 1024*1024;  // allocate 2MB for stack
+#else
+  size_t stack_size = 1 * 1024*1024;  // allocate 1MB for stack
+#endif
+  stack_ = reinterpret_cast<char*>(malloc(stack_size));
+  pc_modified_ = false;
+  icount_ = 0;
+  break_pc_ = NULL;
+  break_instr_ = 0;
+
+  // Set up architecture state.
+  // All registers are initialized to zero to start with.
+  for (int i = 0; i < kNumGPRs; i++) {
+    registers_[i] = 0;
+  }
+  condition_reg_ = 0;
+  fp_condition_reg_ = 0;
+  special_reg_pc_ = 0;
+  special_reg_lr_ = 0;
+  special_reg_ctr_ = 0;
+
+  // Initializing FP registers.
+  for (int i = 0; i < kNumFPRs; i++) {
+    fp_registers_[i] = 0.0;
+  }
+
+  // The sp is initialized to point to the bottom (high address) of the
+  // allocated stack area. To be safe in potential stack underflows we leave
+  // some buffer below.
+  registers_[sp] = reinterpret_cast<intptr_t>(stack_) + stack_size - 64;
+  InitializeCoverage();
+
+  last_debugger_input_ = NULL;
+}
+
+
+Simulator::~Simulator() {
+}
+
+
+// When the generated code calls an external reference we need to catch that in
+// the simulator.  The external reference will be a function compiled for the
+// host architecture.  We need to call that function instead of trying to
+// execute it with the simulator.  We do that by redirecting the external
+// reference to a svc (Supervisor Call) instruction that is handled by
+// the simulator.  We write the original destination of the jump just at a known
+// offset from the svc instruction so the simulator knows what to call.
+class Redirection {
+ public:
+  Redirection(void* external_function, ExternalReference::Type type)
+      : external_function_(external_function),
+        swi_instruction_(rtCallRedirInstr | kCallRtRedirected),
+        type_(type),
+        next_(NULL) {
+    Isolate* isolate = Isolate::Current();
+    next_ = isolate->simulator_redirection();
+    Simulator::current(isolate)->
+        FlushICache(isolate->simulator_i_cache(),
+                    reinterpret_cast<void*>(&swi_instruction_),
+                    Instruction::kInstrSize);
+    isolate->set_simulator_redirection(this);
+  }
+
+  void* address_of_swi_instruction() {
+    return reinterpret_cast<void*>(&swi_instruction_);
+  }
+
+  void* external_function() { return external_function_; }
+  ExternalReference::Type type() { return type_; }
+
+  static Redirection* Get(void* external_function,
+                          ExternalReference::Type type) {
+    Isolate* isolate = Isolate::Current();
+    Redirection* current = isolate->simulator_redirection();
+    for (; current != NULL; current = current->next_) {
+      if (current->external_function_ == external_function) {
+        ASSERT_EQ(current->type(), type);
+        return current;
+      }
+    }
+    return new Redirection(external_function, type);
+  }
+
+  static Redirection* FromSwiInstruction(Instruction* swi_instruction) {
+    char* addr_of_swi = reinterpret_cast<char*>(swi_instruction);
+    char* addr_of_redirection =
+        addr_of_swi - OFFSET_OF(Redirection, swi_instruction_);
+    return reinterpret_cast<Redirection*>(addr_of_redirection);
+  }
+
+  static void* ReverseRedirection(intptr_t reg) {
+    Redirection* redirection = FromSwiInstruction(
+        reinterpret_cast<Instruction*>(reinterpret_cast<void*>(reg)));
+    return redirection->external_function();
+  }
+
+ private:
+  void* external_function_;
+  uint32_t swi_instruction_;
+  ExternalReference::Type type_;
+  Redirection* next_;
+};
+
+
+void* Simulator::RedirectExternalReference(void* external_function,
+                                           ExternalReference::Type type) {
+  Redirection* redirection = Redirection::Get(external_function, type);
+  return redirection->address_of_swi_instruction();
+}
+
+
+// Get the active Simulator for the current thread.
+Simulator* Simulator::current(Isolate* isolate) {
+  v8::internal::Isolate::PerIsolateThreadData* isolate_data =
+      isolate->FindOrAllocatePerThreadDataForThisThread();
+  ASSERT(isolate_data != NULL);
+
+  Simulator* sim = isolate_data->simulator();
+  if (sim == NULL) {
+    // TODO(146): delete the simulator object when a thread/isolate goes away.
+    sim = new Simulator(isolate);
+    isolate_data->set_simulator(sim);
+  }
+  return sim;
+}
+
+
+// Sets the register in the architecture state.
+void Simulator::set_register(int reg, intptr_t value) {
+  ASSERT((reg >= 0) && (reg < kNumGPRs));
+  registers_[reg] = value;
+}
+
+
+// Get the register from the architecture state.
+intptr_t Simulator::get_register(int reg) const {
+  ASSERT((reg >= 0) && (reg < kNumGPRs));
+  // Stupid code added to avoid bug in GCC.
+  // See: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43949
+  if (reg >= kNumGPRs) return 0;
+  // End stupid code.
+  return registers_[reg];
+}
+
+
+double Simulator::get_double_from_register_pair(int reg) {
+  ASSERT((reg >= 0) && (reg < kNumGPRs) && ((reg % 2) == 0));
+
+  double dm_val = 0.0;
+#if !V8_TARGET_ARCH_PPC64  // doesn't make sense in 64bit mode
+  // Read the bits from the unsigned integer register_[] array
+  // into the double precision floating point value and return it.
+  char buffer[sizeof(fp_registers_[0])];
+  memcpy(buffer, &registers_[reg], 2 * sizeof(registers_[0]));
+  memcpy(&dm_val, buffer, 2 * sizeof(registers_[0]));
+#endif
+  return(dm_val);
+}
+
+
+// Raw access to the PC register.
+void Simulator::set_pc(intptr_t value) {
+  pc_modified_ = true;
+  special_reg_pc_ = value;
+}
+
+
+bool Simulator::has_bad_pc() const {
+  return ((special_reg_pc_ == bad_lr) || (special_reg_pc_ == end_sim_pc));
+}
+
+
+// Raw access to the PC register without the special adjustment when reading.
+intptr_t Simulator::get_pc() const {
+  return special_reg_pc_;
+}
+
+
+// Runtime FP routines take:
+// - two double arguments
+// - one double argument and zero or one integer arguments.
+// All are consructed here from d1, d2 and r3.
+void Simulator::GetFpArgs(double* x, double* y, intptr_t* z) {
+  *x = get_double_from_d_register(1);
+  *y = get_double_from_d_register(2);
+  *z = get_register(3);
+}
+
+
+// The return value is in d1.
+void Simulator::SetFpResult(const double& result) {
+  fp_registers_[1] = result;
+}
+
+
+void Simulator::TrashCallerSaveRegisters() {
+  // We don't trash the registers with the return value.
+#if 0  // A good idea to trash volatile registers, needs to be done
+  registers_[2] = 0x50Bad4U;
+  registers_[3] = 0x50Bad4U;
+  registers_[12] = 0x50Bad4U;
+#endif
+}
+
+
+uint32_t Simulator::ReadWU(intptr_t addr, Instruction* instr) {
+  uint32_t* ptr = reinterpret_cast<uint32_t*>(addr);
+  return *ptr;
+}
+
+
+int32_t Simulator::ReadW(intptr_t addr, Instruction* instr) {
+  int32_t* ptr = reinterpret_cast<int32_t*>(addr);
+  return *ptr;
+}
+
+
+void Simulator::WriteW(intptr_t addr, uint32_t value, Instruction* instr) {
+  uint32_t* ptr = reinterpret_cast<uint32_t*>(addr);
+  *ptr = value;
+  return;
+}
+
+
+void Simulator::WriteW(intptr_t addr, int32_t value, Instruction* instr) {
+  int32_t* ptr = reinterpret_cast<int32_t*>(addr);
+  *ptr = value;
+  return;
+}
+
+
+uint16_t Simulator::ReadHU(intptr_t addr, Instruction* instr) {
+  uint16_t* ptr = reinterpret_cast<uint16_t*>(addr);
+  return *ptr;
+}
+
+
+int16_t Simulator::ReadH(intptr_t addr, Instruction* instr) {
+  int16_t* ptr = reinterpret_cast<int16_t*>(addr);
+  return *ptr;
+}
+
+
+void Simulator::WriteH(intptr_t addr, uint16_t value, Instruction* instr) {
+  uint16_t* ptr = reinterpret_cast<uint16_t*>(addr);
+  *ptr = value;
+  return;
+}
+
+
+void Simulator::WriteH(intptr_t addr, int16_t value, Instruction* instr) {
+  int16_t* ptr = reinterpret_cast<int16_t*>(addr);
+  *ptr = value;
+  return;
+}
+
+
+uint8_t Simulator::ReadBU(intptr_t addr) {
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(addr);
+  return *ptr;
+}
+
+
+int8_t Simulator::ReadB(intptr_t addr) {
+  int8_t* ptr = reinterpret_cast<int8_t*>(addr);
+  return *ptr;
+}
+
+
+void Simulator::WriteB(intptr_t addr, uint8_t value) {
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(addr);
+  *ptr = value;
+}
+
+
+void Simulator::WriteB(intptr_t addr, int8_t value) {
+  int8_t* ptr = reinterpret_cast<int8_t*>(addr);
+  *ptr = value;
+}
+
+
+intptr_t* Simulator::ReadDW(intptr_t addr) {
+  intptr_t* ptr = reinterpret_cast<intptr_t*>(addr);
+  return ptr;
+}
+
+
+void Simulator::WriteDW(intptr_t addr, int64_t value) {
+  int64_t* ptr = reinterpret_cast<int64_t*>(addr);
+  *ptr = value;
+  return;
+}
+
+
+// Returns the limit of the stack area to enable checking for stack overflows.
+uintptr_t Simulator::StackLimit() const {
+  // Leave a safety margin of 1024 bytes to prevent overrunning the stack when
+  // pushing values.
+  return reinterpret_cast<uintptr_t>(stack_) + 1024;
+}
+
+
+// Unsupported instructions use Format to print an error and stop execution.
+void Simulator::Format(Instruction* instr, const char* format) {
+  PrintF("Simulator found unsupported instruction:\n 0x%08" V8PRIxPTR ": %s\n",
+         reinterpret_cast<intptr_t>(instr), format);
+  UNIMPLEMENTED();
+}
+
+
+// Calculate C flag value for additions.
+bool Simulator::CarryFrom(int32_t left, int32_t right, int32_t carry) {
+  uint32_t uleft = static_cast<uint32_t>(left);
+  uint32_t uright = static_cast<uint32_t>(right);
+  uint32_t urest  = 0xffffffffU - uleft;
+
+  return (uright > urest) ||
+         (carry && (((uright + 1) > urest) || (uright > (urest - 1))));
+}
+
+
+// Calculate C flag value for subtractions.
+bool Simulator::BorrowFrom(int32_t left, int32_t right) {
+  uint32_t uleft = static_cast<uint32_t>(left);
+  uint32_t uright = static_cast<uint32_t>(right);
+
+  return (uright > uleft);
+}
+
+
+// Calculate V flag value for additions and subtractions.
+bool Simulator::OverflowFrom(int32_t alu_out,
+                             int32_t left, int32_t right, bool addition) {
+  bool overflow;
+  if (addition) {
+               // operands have the same sign
+    overflow = ((left >= 0 && right >= 0) || (left < 0 && right < 0))
+               // and operands and result have different sign
+               && ((left < 0 && alu_out >= 0) || (left >= 0 && alu_out < 0));
+  } else {
+               // operands have different signs
+    overflow = ((left < 0 && right >= 0) || (left >= 0 && right < 0))
+               // and first operand and result have different signs
+               && ((left < 0 && alu_out >= 0) || (left >= 0 && alu_out < 0));
+  }
+  return overflow;
+}
+
+
+#if !V8_TARGET_ARCH_PPC64
+// Calls into the V8 runtime are based on this very simple interface.
+// Note: To be able to return two values from some calls the code in runtime.cc
+// uses the ObjectPair which is essentially two 32-bit values stuffed into a
+// 64-bit value. With the code below we assume that all runtime calls return
+// 64 bits of result. If they don't, the r4 result register contains a bogus
+// value, which is fine because it is caller-saved.
+typedef int64_t (*SimulatorRuntimeCall)(intptr_t arg0,
+                                        intptr_t arg1,
+                                        intptr_t arg2,
+                                        intptr_t arg3,
+                                        intptr_t arg4,
+                                        intptr_t arg5);
+#else
+// For 64-bit, we need to be more explicit.
+typedef intptr_t (*SimulatorRuntimeCall)(intptr_t arg0,
+                                        intptr_t arg1,
+                                        intptr_t arg2,
+                                        intptr_t arg3,
+                                        intptr_t arg4,
+                                        intptr_t arg5);
+struct ObjectPair {
+  intptr_t x;
+  intptr_t y;
+};
+
+typedef struct ObjectPair (*SimulatorRuntimeObjectPairCall)(intptr_t arg0,
+                                                            intptr_t arg1,
+                                                            intptr_t arg2,
+                                                            intptr_t arg3,
+                                                            intptr_t arg4,
+                                                            intptr_t arg5);
+#endif
+
+// These prototypes handle the four types of FP calls.
+typedef int (*SimulatorRuntimeCompareCall)(double darg0, double darg1);
+typedef double (*SimulatorRuntimeFPFPCall)(double darg0, double darg1);
+typedef double (*SimulatorRuntimeFPCall)(double darg0);
+typedef double (*SimulatorRuntimeFPIntCall)(double darg0, intptr_t arg0);
+
+// This signature supports direct call in to API function native callback
+// (refer to InvocationCallback in v8.h).
+typedef void (*SimulatorRuntimeDirectApiCall)(intptr_t arg0);
+typedef void (*SimulatorRuntimeProfilingApiCall)(intptr_t arg0, void* arg1);
+
+// This signature supports direct call to accessor getter callback.
+typedef void (*SimulatorRuntimeDirectGetterCall)(intptr_t arg0, intptr_t arg1);
+typedef void (*SimulatorRuntimeProfilingGetterCall)(
+    intptr_t arg0, intptr_t arg1, void* arg2);
+
+// Software interrupt instructions are used by the simulator to call into the
+// C-based V8 runtime.
+void Simulator::SoftwareInterrupt(Instruction* instr) {
+  int svc = instr->SvcValue();
+  switch (svc) {
+    case kCallRtRedirected: {
+      // Check if stack is aligned. Error if not aligned is reported below to
+      // include information on the function called.
+      bool stack_aligned =
+          (get_register(sp)
+           & (::v8::internal::FLAG_sim_stack_alignment - 1)) == 0;
+      Redirection* redirection = Redirection::FromSwiInstruction(instr);
+      const int kArgCount = 6;
+      int arg0_regnum = 3;
+#if V8_TARGET_ARCH_PPC64 && !ABI_RETURNS_OBJECT_PAIRS_IN_REGS
+      intptr_t result_buffer = 0;
+      if (redirection->type() == ExternalReference::BUILTIN_OBJECTPAIR_CALL) {
+        result_buffer = get_register(r3);
+        arg0_regnum++;
+      }
+#endif
+      intptr_t arg[kArgCount];
+      for (int i = 0; i < kArgCount; i++) {
+        arg[i] = get_register(arg0_regnum + i);
+      }
+      bool fp_call =
+         (redirection->type() == ExternalReference::BUILTIN_FP_FP_CALL) ||
+         (redirection->type() == ExternalReference::BUILTIN_COMPARE_CALL) ||
+         (redirection->type() == ExternalReference::BUILTIN_FP_CALL) ||
+         (redirection->type() == ExternalReference::BUILTIN_FP_INT_CALL);
+      // This is dodgy but it works because the C entry stubs are never moved.
+      // See comment in codegen-arm.cc and bug 1242173.
+      intptr_t saved_lr = special_reg_lr_;
+      intptr_t external =
+          reinterpret_cast<intptr_t>(redirection->external_function());
+      if (fp_call) {
+        double dval0, dval1;  // one or two double parameters
+        intptr_t ival;        // zero or one integer parameters
+        int iresult = 0;      // integer return value
+        double dresult = 0;   // double return value
+        GetFpArgs(&dval0, &dval1, &ival);
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          SimulatorRuntimeCall generic_target =
+              reinterpret_cast<SimulatorRuntimeCall>(external);
+          switch (redirection->type()) {
+          case ExternalReference::BUILTIN_FP_FP_CALL:
+          case ExternalReference::BUILTIN_COMPARE_CALL:
+            PrintF("Call to host function at %p with args %f, %f",
+                   FUNCTION_ADDR(generic_target), dval0, dval1);
+            break;
+          case ExternalReference::BUILTIN_FP_CALL:
+            PrintF("Call to host function at %p with arg %f",
+                   FUNCTION_ADDR(generic_target), dval0);
+            break;
+          case ExternalReference::BUILTIN_FP_INT_CALL:
+            PrintF("Call to host function at %p with args %f, %" V8PRIdPTR,
+                   FUNCTION_ADDR(generic_target), dval0, ival);
+            break;
+          default:
+            UNREACHABLE();
+            break;
+          }
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR
+                   "\n", get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+        switch (redirection->type()) {
+          case ExternalReference::BUILTIN_COMPARE_CALL: {
+            SimulatorRuntimeCompareCall target =
+              reinterpret_cast<SimulatorRuntimeCompareCall>(external);
+            iresult = target(dval0, dval1);
+            set_register(r3, iresult);
+            break;
+          }
+          case ExternalReference::BUILTIN_FP_FP_CALL: {
+            SimulatorRuntimeFPFPCall target =
+              reinterpret_cast<SimulatorRuntimeFPFPCall>(external);
+            dresult = target(dval0, dval1);
+            SetFpResult(dresult);
+            break;
+          }
+          case ExternalReference::BUILTIN_FP_CALL: {
+            SimulatorRuntimeFPCall target =
+              reinterpret_cast<SimulatorRuntimeFPCall>(external);
+            dresult = target(dval0);
+            SetFpResult(dresult);
+            break;
+          }
+          case ExternalReference::BUILTIN_FP_INT_CALL: {
+            SimulatorRuntimeFPIntCall target =
+              reinterpret_cast<SimulatorRuntimeFPIntCall>(external);
+            dresult = target(dval0, ival);
+            SetFpResult(dresult);
+            break;
+          }
+          default:
+            UNREACHABLE();
+            break;
+        }
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          switch (redirection->type()) {
+          case ExternalReference::BUILTIN_COMPARE_CALL:
+            PrintF("Returned %08x\n", iresult);
+            break;
+          case ExternalReference::BUILTIN_FP_FP_CALL:
+          case ExternalReference::BUILTIN_FP_CALL:
+          case ExternalReference::BUILTIN_FP_INT_CALL:
+            PrintF("Returned %f\n", dresult);
+            break;
+          default:
+            UNREACHABLE();
+            break;
+          }
+        }
+      } else if (redirection->type() == ExternalReference::DIRECT_API_CALL) {
+        // See callers of MacroAssembler::CallApiFunctionAndReturn for
+        // explanation of register usage.
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          PrintF("Call to host function at %p args %08" V8PRIxPTR,
+                 reinterpret_cast<void*>(external), arg[0]);
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR
+                   "\n", get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+        SimulatorRuntimeDirectApiCall target =
+          reinterpret_cast<SimulatorRuntimeDirectApiCall>(external);
+        target(arg[0]);
+      } else if (
+          redirection->type() == ExternalReference::PROFILING_API_CALL) {
+        // See callers of MacroAssembler::CallApiFunctionAndReturn for
+        // explanation of register usage.
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          PrintF("Call to host function at %p args %08" V8PRIxPTR " %08"
+                 V8PRIxPTR,
+                 reinterpret_cast<void*>(external), arg[0], arg[1]);
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR
+                   "\n", get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+        SimulatorRuntimeProfilingApiCall target =
+          reinterpret_cast<SimulatorRuntimeProfilingApiCall>(external);
+        target(arg[0], Redirection::ReverseRedirection(arg[1]));
+      } else if (
+          redirection->type() == ExternalReference::DIRECT_GETTER_CALL) {
+        // See callers of MacroAssembler::CallApiFunctionAndReturn for
+        // explanation of register usage.
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          PrintF("Call to host function at %p args %08" V8PRIxPTR " %08"
+                 V8PRIxPTR,
+                 reinterpret_cast<void*>(external), arg[0], arg[1]);
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR
+                   "\n", get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+        SimulatorRuntimeDirectGetterCall target =
+          reinterpret_cast<SimulatorRuntimeDirectGetterCall>(external);
+#if !ABI_PASSES_HANDLES_IN_REGS
+        arg[0] = *(reinterpret_cast<intptr_t *>(arg[0]));
+#endif
+        target(arg[0], arg[1]);
+      } else if (
+        redirection->type() == ExternalReference::PROFILING_GETTER_CALL) {
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          PrintF("Call to host function at %p args %08" V8PRIxPTR " %08"
+                 V8PRIxPTR " %08" V8PRIxPTR,
+                 reinterpret_cast<void*>(external), arg[0], arg[1], arg[2]);
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR "\n",
+                   get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+        SimulatorRuntimeProfilingGetterCall target =
+          reinterpret_cast<SimulatorRuntimeProfilingGetterCall>(
+            external);
+#if !ABI_PASSES_HANDLES_IN_REGS
+        arg[0] = *(reinterpret_cast<intptr_t *>(arg[0]));
+#endif
+        target(arg[0], arg[1], Redirection::ReverseRedirection(arg[2]));
+      } else {
+        // builtin call.
+        if (::v8::internal::FLAG_trace_sim || !stack_aligned) {
+          SimulatorRuntimeCall target =
+            reinterpret_cast<SimulatorRuntimeCall>(external);
+          PrintF(
+              "Call to host function at %p,\n"
+              "\t\t\t\targs %08" V8PRIxPTR ", %08" V8PRIxPTR ", %08" V8PRIxPTR
+              ", %08" V8PRIxPTR ", %08" V8PRIxPTR ", %08" V8PRIxPTR,
+              FUNCTION_ADDR(target),
+              arg[0],
+              arg[1],
+              arg[2],
+              arg[3],
+              arg[4],
+              arg[5]);
+          if (!stack_aligned) {
+            PrintF(" with unaligned stack %08" V8PRIxPTR
+                   "\n", get_register(sp));
+          }
+          PrintF("\n");
+        }
+        CHECK(stack_aligned);
+#if !V8_TARGET_ARCH_PPC64
+        ASSERT(redirection->type() == ExternalReference::BUILTIN_CALL);
+        SimulatorRuntimeCall target =
+          reinterpret_cast<SimulatorRuntimeCall>(external);
+        int64_t result = target(arg[0], arg[1], arg[2], arg[3], arg[4], arg[5]);
+        int32_t lo_res = static_cast<int32_t>(result);
+        int32_t hi_res = static_cast<int32_t>(result >> 32);
+#if V8_TARGET_BIG_ENDIAN
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Returned %08x\n", hi_res);
+        }
+        set_register(r3, hi_res);
+        set_register(r4, lo_res);
+#else
+        if (::v8::internal::FLAG_trace_sim) {
+          PrintF("Returned %08x\n", lo_res);
+        }
+        set_register(r3, lo_res);
+        set_register(r4, hi_res);
+#endif
+#else
+        if (redirection->type() == ExternalReference::BUILTIN_CALL) {
+          SimulatorRuntimeCall target =
+            reinterpret_cast<SimulatorRuntimeCall>(external);
+          intptr_t result = target(arg[0], arg[1], arg[2], arg[3], arg[4],
+                                   arg[5]);
+          if (::v8::internal::FLAG_trace_sim) {
+            PrintF("Returned %08" V8PRIxPTR "\n", result);
+          }
+          set_register(r3, result);
+        } else {
+          ASSERT(redirection->type() ==
+                 ExternalReference::BUILTIN_OBJECTPAIR_CALL);
+          SimulatorRuntimeObjectPairCall target =
+            reinterpret_cast<SimulatorRuntimeObjectPairCall>(external);
+          struct ObjectPair result = target(arg[0], arg[1], arg[2], arg[3],
+                                            arg[4], arg[5]);
+          if (::v8::internal::FLAG_trace_sim) {
+            PrintF("Returned %08" V8PRIxPTR ", %08" V8PRIxPTR "\n",
+                   result.x, result.y);
+          }
+#if ABI_RETURNS_OBJECT_PAIRS_IN_REGS
+          set_register(r3, result.x);
+          set_register(r4, result.y);
+#else
+          memcpy(reinterpret_cast<void *>(result_buffer), &result,
+                 sizeof(struct ObjectPair));
+#endif
+        }
+#endif
+      }
+      set_pc(saved_lr);
+      break;
+    }
+    case kBreakpoint: {
+      PPCDebugger dbg(this);
+      dbg.Debug();
+      break;
+    }
+    case kInfo: {
+       PPCDebugger dbg(this);
+       dbg.Info(instr);
+       break;
+     }
+    // stop uses all codes greater than 1 << 23.
+    default: {
+      if (svc >= (1 << 23)) {
+        uint32_t code = svc & kStopCodeMask;
+        if (isWatchedStop(code)) {
+          IncreaseStopCounter(code);
+        }
+        // Stop if it is enabled, otherwise go on jumping over the stop
+        // and the message address.
+        if (isEnabledStop(code)) {
+          PPCDebugger dbg(this);
+          dbg.Stop(instr);
+        } else {
+          set_pc(get_pc() + Instruction::kInstrSize + kPointerSize);
+        }
+      } else {
+        // This is not a valid svc code.
+        UNREACHABLE();
+        break;
+      }
+    }
+  }
+}
+
+
+// Stop helper functions.
+bool Simulator::isStopInstruction(Instruction* instr) {
+  return (instr->Bits(27, 24) == 0xF) && (instr->SvcValue() >= kStopCode);
+}
+
+
+bool Simulator::isWatchedStop(uint32_t code) {
+  ASSERT(code <= kMaxStopCode);
+  return code < kNumOfWatchedStops;
+}
+
+
+bool Simulator::isEnabledStop(uint32_t code) {
+  ASSERT(code <= kMaxStopCode);
+  // Unwatched stops are always enabled.
+  return !isWatchedStop(code) ||
+    !(watched_stops_[code].count & kStopDisabledBit);
+}
+
+
+void Simulator::EnableStop(uint32_t code) {
+  ASSERT(isWatchedStop(code));
+  if (!isEnabledStop(code)) {
+    watched_stops_[code].count &= ~kStopDisabledBit;
+  }
+}
+
+
+void Simulator::DisableStop(uint32_t code) {
+  ASSERT(isWatchedStop(code));
+  if (isEnabledStop(code)) {
+    watched_stops_[code].count |= kStopDisabledBit;
+  }
+}
+
+
+void Simulator::IncreaseStopCounter(uint32_t code) {
+  ASSERT(code <= kMaxStopCode);
+  ASSERT(isWatchedStop(code));
+  if ((watched_stops_[code].count & ~(1 << 31)) == 0x7fffffff) {
+    PrintF("Stop counter for code %i has overflowed.\n"
+           "Enabling this code and reseting the counter to 0.\n", code);
+    watched_stops_[code].count = 0;
+    EnableStop(code);
+  } else {
+    watched_stops_[code].count++;
+  }
+}
+
+
+// Print a stop status.
+void Simulator::PrintStopInfo(uint32_t code) {
+  ASSERT(code <= kMaxStopCode);
+  if (!isWatchedStop(code)) {
+    PrintF("Stop not watched.");
+  } else {
+    const char* state = isEnabledStop(code) ? "Enabled" : "Disabled";
+    int32_t count = watched_stops_[code].count & ~kStopDisabledBit;
+    // Don't print the state of unused breakpoints.
+    if (count != 0) {
+      if (watched_stops_[code].desc) {
+        PrintF("stop %i - 0x%x: \t%s, \tcounter = %i, \t%s\n",
+               code, code, state, count, watched_stops_[code].desc);
+      } else {
+        PrintF("stop %i - 0x%x: \t%s, \tcounter = %i\n",
+               code, code, state, count);
+      }
+    }
+  }
+}
+
+
+void Simulator::SetCR0(intptr_t result, bool setSO) {
+  int bf = 0;
+  if (result <  0) { bf |= 0x80000000; }
+  if (result >  0) { bf |= 0x40000000; }
+  if (result == 0) { bf |= 0x20000000; }
+  if (setSO) { bf |= 0x10000000; }
+  condition_reg_ = (condition_reg_ & ~0xF0000000) | bf;
+}
+
+
+void Simulator::ExecuteBranchConditional(Instruction* instr) {
+  int bo = instr->Bits(25, 21) << 21;
+  int offset = (instr->Bits(15, 2) << 18) >> 16;
+  int condition_bit = instr->Bits(20, 16);
+  int condition_mask = 0x80000000 >> condition_bit;
+  switch (bo) {
+    case DCBNZF:  // Decrement CTR; branch if CTR != 0 and condition false
+    case DCBEZF:  // Decrement CTR; branch if CTR == 0 and condition false
+      UNIMPLEMENTED();
+    case BF: {   // Branch if condition false
+      if (!(condition_reg_ & condition_mask)) {
+        if (instr->Bit(0) == 1) {  // LK flag set
+          special_reg_lr_ = get_pc() + 4;
+        }
+        set_pc(get_pc() + offset);
+      }
+      break;
+    }
+    case DCBNZT:  // Decrement CTR; branch if CTR != 0 and condition true
+    case DCBEZT:  // Decrement CTR; branch if CTR == 0 and condition true
+      UNIMPLEMENTED();
+    case BT: {   // Branch if condition true
+      if (condition_reg_ & condition_mask) {
+        if (instr->Bit(0) == 1) {  // LK flag set
+          special_reg_lr_ = get_pc() + 4;
+        }
+        set_pc(get_pc() + offset);
+      }
+      break;
+    }
+    case DCBNZ:  // Decrement CTR; branch if CTR != 0
+    case DCBEZ:  // Decrement CTR; branch if CTR == 0
+      special_reg_ctr_ -= 1;
+      if ((special_reg_ctr_ == 0) == (bo == DCBEZ)) {
+        if (instr->Bit(0) == 1) {  // LK flag set
+          special_reg_lr_ = get_pc() + 4;
+        }
+        set_pc(get_pc() + offset);
+      }
+      break;
+    case BA: {   // Branch always
+      if (instr->Bit(0) == 1) {  // LK flag set
+        special_reg_lr_ = get_pc() + 4;
+      }
+      set_pc(get_pc() + offset);
+      break;
+    }
+    default:
+      UNIMPLEMENTED();  // Invalid encoding
+  }
+}
+
+
+// Handle execution based on instruction types.
+void Simulator::ExecuteExt1(Instruction* instr) {
+  switch (instr->Bits(10, 1) << 1) {
+    case MCRF:
+      UNIMPLEMENTED();  // Not used by V8.
+    case BCLRX: {
+        // need to check BO flag
+        intptr_t old_pc = get_pc();
+        set_pc(special_reg_lr_);
+        if (instr->Bit(0) == 1) {  // LK flag set
+          special_reg_lr_ = old_pc + 4;
+        }
+      break;
+    }
+    case BCCTRX: {
+        // need to check BO flag
+        intptr_t old_pc = get_pc();
+        set_pc(special_reg_ctr_);
+        if (instr->Bit(0) == 1) {  // LK flag set
+          special_reg_lr_ = old_pc + 4;
+        }
+      break;
+    }
+    case CRNOR:
+    case RFI:
+    case CRANDC:
+      UNIMPLEMENTED();
+    case ISYNC: {
+      // todo - simulate isync
+      break;
+    }
+    case CRXOR: {
+      int bt = instr->Bits(25, 21);
+      int ba = instr->Bits(20, 16);
+      int bb = instr->Bits(15, 11);
+      int ba_val = ((0x80000000 >> ba) & condition_reg_) == 0 ? 0 : 1;
+      int bb_val = ((0x80000000 >> bb) & condition_reg_) == 0 ? 0 : 1;
+      int bt_val = ba_val ^ bb_val;
+      bt_val = bt_val << (31-bt);  // shift bit to correct destination
+      condition_reg_ &= ~(0x80000000 >> bt);
+      condition_reg_ |= bt_val;
+      break;
+    }
+    case CREQV: {
+      int bt = instr->Bits(25, 21);
+      int ba = instr->Bits(20, 16);
+      int bb = instr->Bits(15, 11);
+      int ba_val = ((0x80000000 >> ba) & condition_reg_) == 0 ? 0 : 1;
+      int bb_val = ((0x80000000 >> bb) & condition_reg_) == 0 ? 0 : 1;
+      int bt_val = 1 - (ba_val ^ bb_val);
+      bt_val = bt_val << (31-bt);  // shift bit to correct destination
+      condition_reg_ &= ~(0x80000000 >> bt);
+      condition_reg_ |= bt_val;
+      break;
+    }
+    case CRNAND:
+    case CRAND:
+    case CRORC:
+    case CROR:
+    default: {
+      UNIMPLEMENTED();  // Not used by V8.
+    }
+  }
+}
+
+
+bool Simulator::ExecuteExt2_10bit(Instruction *instr) {
+  bool found = true;
+
+  int opcode = instr->Bits(10, 1) << 1;
+  switch (opcode) {
+    case SRWX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      uint32_t rs_val = get_register(rs);
+      uintptr_t rb_val = get_register(rb);
+      intptr_t  result = rs_val >> (rb_val & 0x3f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case SRDX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      uintptr_t rs_val = get_register(rs);
+      uintptr_t rb_val = get_register(rb);
+      intptr_t  result = rs_val >> (rb_val & 0x7f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#endif
+    case SRAW: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int32_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t result = rs_val >> (rb_val & 0x3f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case SRAD: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t result = rs_val >> (rb_val & 0x7f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#endif
+    case SRAWIX: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      int sh = instr->Bits(15, 11);
+      int32_t rs_val = get_register(rs);
+      intptr_t result = rs_val >> sh;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case EXTSW: {
+      const int shift = kBitsPerPointer - 32;
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t ra_val = (rs_val << shift) >> shift;
+      set_register(ra, ra_val);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(ra_val);
+      }
+      break;
+    }
+#endif
+    case EXTSH: {
+      const int shift = kBitsPerPointer - 16;
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t ra_val = (rs_val << shift) >> shift;
+      set_register(ra, ra_val);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(ra_val);
+      }
+      break;
+    }
+    case EXTSB: {
+      const int shift = kBitsPerPointer - 8;
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t ra_val = (rs_val << shift) >> shift;
+      set_register(ra, ra_val);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(ra_val);
+      }
+      break;
+    }
+    case LFSUX:
+    case LFSX: {
+      int frt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      int32_t val = ReadW(ra_val + rb_val, instr);
+      float *fptr = reinterpret_cast<float*>(&val);
+      set_d_register_from_double(frt, static_cast<double>(*fptr));
+      if (opcode == LFSUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case LFDUX:
+    case LFDX: {
+      int frt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      double *dptr = reinterpret_cast<double*>(ReadDW(ra_val + rb_val));
+      set_d_register_from_double(frt, *dptr);
+      if (opcode == LFDUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case STFSUX: {
+    case STFSX:
+      int frs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      float frs_val = static_cast<float>(get_double_from_d_register(frs));
+      int32_t *p=  reinterpret_cast<int32_t*>(&frs_val);
+      WriteW(ra_val + rb_val, *p, instr);
+      if (opcode == STFSUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case STFDUX: {
+    case STFDX:
+      int frs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      double frs_val = get_double_from_d_register(frs);
+      int64_t *p = reinterpret_cast<int64_t *>(&frs_val);
+      WriteDW(ra_val + rb_val, *p);
+      if (opcode == STFDUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case SYNC: {
+      // todo - simulate sync
+      break;
+    }
+    case ICBI: {
+      // todo - simulate icbi
+      break;
+    }
+    default: {
+      found = false;
+      break;
+    }
+  }
+
+  if (found)
+    return found;
+
+  found = true;
+  opcode = instr->Bits(10, 2) << 2;
+  switch (opcode) {
+    case SRADIX: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      int sh = (instr->Bits(15, 11) | (instr->Bit(1) << 5));
+      intptr_t rs_val = get_register(rs);
+      intptr_t result = rs_val >> sh;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+    default: {
+      found = false;
+      break;
+    }
+  }
+
+  return found;
+}
+
+
+bool Simulator::ExecuteExt2_9bit_part1(Instruction* instr) {
+  bool found = true;
+
+  int opcode = instr->Bits(9, 1) << 1;
+  switch (opcode) {
+    case TW: {
+      // used for call redirection in simulation mode
+      SoftwareInterrupt(instr);
+      break;
+    }
+    case CMP: {
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int cr = instr->Bits(25, 23);
+      uint32_t bf = 0;
+#if V8_TARGET_ARCH_PPC64
+      int L = instr->Bit(21);
+      if (L) {
+#endif
+        intptr_t ra_val = get_register(ra);
+        intptr_t rb_val = get_register(rb);
+        if (ra_val < rb_val) { bf |= 0x80000000; }
+        if (ra_val > rb_val) { bf |= 0x40000000; }
+        if (ra_val == rb_val) { bf |= 0x20000000; }
+#if V8_TARGET_ARCH_PPC64
+      } else {
+        int32_t ra_val = get_register(ra);
+        int32_t rb_val = get_register(rb);
+        if (ra_val < rb_val) { bf |= 0x80000000; }
+        if (ra_val > rb_val) { bf |= 0x40000000; }
+        if (ra_val == rb_val) { bf |= 0x20000000; }
+      }
+#endif
+      uint32_t condition_mask = 0xF0000000U >> (cr*4);
+      uint32_t condition =  bf >> (cr*4);
+      condition_reg_ = (condition_reg_ & ~condition_mask) | condition;
+      break;
+    }
+    case SUBFCX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      // int oe = instr->Bit(10);
+      uintptr_t ra_val = get_register(ra);
+      uintptr_t rb_val = get_register(rb);
+      uintptr_t alu_out = ~ra_val + rb_val + 1;
+      set_register(rt, alu_out);
+      // If the sign of rb and alu_out don't match, carry = 0
+      if ((alu_out ^ rb_val) & 0x80000000) {
+        special_reg_xer_ &= ~0xF0000000;
+      } else {
+        special_reg_xer_ = (special_reg_xer_ & ~0xF0000000) | 0x20000000;
+      }
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case ADDCX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      // int oe = instr->Bit(10);
+      uintptr_t ra_val = get_register(ra);
+      uintptr_t rb_val = get_register(rb);
+      uintptr_t alu_out = ra_val + rb_val;
+      // Check overflow
+      if (~ra_val < rb_val) {
+        special_reg_xer_ = (special_reg_xer_ & ~0xF0000000) | 0x20000000;
+      } else {
+        special_reg_xer_ &= ~0xF0000000;
+      }
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(static_cast<intptr_t>(alu_out));
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case MULHWX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int32_t ra_val = (get_register(ra) & 0xFFFFFFFF);
+      int32_t rb_val = (get_register(rb) & 0xFFFFFFFF);
+      int64_t alu_out = (int64_t)ra_val * (int64_t)rb_val;
+      alu_out >>= 32;
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(static_cast<intptr_t>(alu_out));
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case NEGX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      intptr_t ra_val = get_register(ra);
+      intptr_t alu_out = 1 + ~ra_val;
+#if V8_TARGET_ARCH_PPC64
+      intptr_t one = 1;  // work-around gcc
+      intptr_t kOverflowVal = (one << 63);
+#else
+      intptr_t kOverflowVal = kMinInt;
+#endif
+      set_register(rt, alu_out);
+      if (instr->Bit(10)) {  // OE bit set
+        if (ra_val == kOverflowVal) {
+            special_reg_xer_ |= 0xC0000000;  // set SO,OV
+        } else {
+            special_reg_xer_ &= ~0x40000000;  // clear OV
+        }
+      }
+      if (instr->Bit(0)) {  // RC bit set
+        bool setSO = (special_reg_xer_ & 0x80000000);
+        SetCR0(alu_out, setSO);
+      }
+      break;
+    }
+    case SLWX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      uint32_t rs_val = get_register(rs);
+      uintptr_t rb_val = get_register(rb);
+      uint32_t result = rs_val << (rb_val & 0x3f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case SLDX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      uintptr_t rs_val = get_register(rs);
+      uintptr_t rb_val = get_register(rb);
+      uintptr_t result = rs_val << (rb_val & 0x7f);
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+#endif
+    default: {
+      found = false;
+      break;
+    }
+  }
+
+  return found;
+}
+
+
+
+void Simulator::ExecuteExt2_9bit_part2(Instruction* instr) {
+  int opcode = instr->Bits(9, 1) << 1;
+  switch (opcode) {
+    case CNTLZWX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      uintptr_t rs_val = get_register(rs);
+      uintptr_t count  = 0;
+      int      n      = 0;
+      uintptr_t bit    = 0x80000000;
+      for (; n < 32; n++) {
+          if (bit & rs_val)
+              break;
+          count++;
+          bit >>= 1;
+      }
+      set_register(ra, count);
+      if (instr->Bit(0)) {  // RC Bit set
+        int bf = 0;
+        if (count > 0)  { bf |= 0x40000000; }
+        if (count == 0) { bf |= 0x20000000; }
+        condition_reg_ = (condition_reg_ & ~0xF0000000) | bf;
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case CNTLZDX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      uintptr_t rs_val = get_register(rs);
+      uintptr_t count  = 0;
+      int      n      = 0;
+      uintptr_t bit    = 0x8000000000000000UL;
+      for (; n < 64; n++) {
+          if (bit & rs_val)
+              break;
+          count++;
+          bit >>= 1;
+      }
+      set_register(ra, count);
+      if (instr->Bit(0)) {  // RC Bit set
+        int bf = 0;
+        if (count > 0)  { bf |= 0x40000000; }
+        if (count == 0) { bf |= 0x20000000; }
+        condition_reg_ = (condition_reg_ & ~0xF0000000) | bf;
+      }
+      break;
+    }
+#endif
+    case ANDX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = rs_val & rb_val;
+      set_register(ra, alu_out);
+      if (instr->Bit(0)) {  // RC Bit set
+        SetCR0(alu_out);
+      }
+      break;
+    }
+    case ANDCX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = rs_val & ~rb_val;
+      set_register(ra, alu_out);
+      if (instr->Bit(0)) {  // RC Bit set
+        SetCR0(alu_out);
+      }
+      break;
+    }
+    case CMPL: {
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int cr = instr->Bits(25, 23);
+      uint32_t bf = 0;
+#if V8_TARGET_ARCH_PPC64
+      int L = instr->Bit(21);
+      if (L) {
+#endif
+        uintptr_t ra_val = get_register(ra);
+        uintptr_t rb_val = get_register(rb);
+        if (ra_val < rb_val) { bf |= 0x80000000; }
+        if (ra_val > rb_val) { bf |= 0x40000000; }
+        if (ra_val == rb_val) { bf |= 0x20000000; }
+#if V8_TARGET_ARCH_PPC64
+      } else {
+        uint32_t ra_val = get_register(ra);
+        uint32_t rb_val = get_register(rb);
+        if (ra_val < rb_val) { bf |= 0x80000000; }
+        if (ra_val > rb_val) { bf |= 0x40000000; }
+        if (ra_val == rb_val) { bf |= 0x20000000; }
+      }
+#endif
+      uint32_t condition_mask = 0xF0000000U >> (cr*4);
+      uint32_t condition =  bf >> (cr*4);
+      condition_reg_ = (condition_reg_ & ~condition_mask) | condition;
+      break;
+    }
+    case SUBFX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      // int oe = instr->Bit(10);
+      intptr_t ra_val = get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = rb_val - ra_val;
+      // todo - figure out underflow
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC Bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case ADDZEX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      intptr_t ra_val = get_register(ra);
+      if (special_reg_xer_ & 0x20000000) {
+        ra_val += 1;
+      }
+      set_register(rt, ra_val);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(ra_val);
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case NORX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = ~(rs_val | rb_val);
+      set_register(ra, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      break;
+    }
+    case MULLW: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int32_t ra_val = (get_register(ra) & 0xFFFFFFFF);
+      int32_t rb_val = (get_register(rb) & 0xFFFFFFFF);
+      int32_t alu_out = ra_val * rb_val;
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case MULLD: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int64_t ra_val = get_register(ra);
+      int64_t rb_val = get_register(rb);
+      int64_t alu_out = ra_val * rb_val;
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+#endif
+    case DIVW: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int32_t ra_val = get_register(ra);
+      int32_t rb_val = get_register(rb);
+      bool overflow = (ra_val == kMinInt && rb_val == -1);
+      // result is undefined if divisor is zero or if operation
+      // is 0x80000000 / -1.
+      int32_t alu_out = (rb_val == 0 || overflow) ? -1 : ra_val / rb_val;
+      set_register(rt, alu_out);
+      if (instr->Bit(10)) {  // OE bit set
+        if (overflow) {
+            special_reg_xer_ |= 0xC0000000;  // set SO,OV
+        } else {
+            special_reg_xer_ &= ~0x40000000;  // clear OV
+        }
+      }
+      if (instr->Bit(0)) {  // RC bit set
+        bool setSO = (special_reg_xer_ & 0x80000000);
+        SetCR0(alu_out, setSO);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case DIVD: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      int64_t ra_val = get_register(ra);
+      int64_t rb_val = get_register(rb);
+      int64_t one = 1;  // work-around gcc
+      int64_t kMinLongLong = (one << 63);
+      // result is undefined if divisor is zero or if operation
+      // is 0x80000000_00000000 / -1.
+      int64_t alu_out = (rb_val == 0 ||
+                         (ra_val == kMinLongLong && rb_val == -1)) ?
+        -1 :
+        ra_val / rb_val;
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+#endif
+    case ADDX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      // int oe = instr->Bit(10);
+      intptr_t ra_val = get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = ra_val + rb_val;
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      // todo - handle OE bit
+      break;
+    }
+    case XORX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = rs_val ^ rb_val;
+      set_register(ra, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      break;
+    }
+    case ORX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      intptr_t alu_out = rs_val | rb_val;
+      set_register(ra, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(alu_out);
+      }
+      break;
+    }
+    case MFSPR: {
+      int rt = instr->RTValue();
+      int spr = instr->Bits(20, 11);
+      if (spr != 256) {
+        UNIMPLEMENTED();  // Only LRLR supported
+      }
+      set_register(rt, special_reg_lr_);
+      break;
+    }
+    case MTSPR: {
+      int rt = instr->RTValue();
+      intptr_t rt_val = get_register(rt);
+      int spr = instr->Bits(20, 11);
+      if (spr == 256) {
+        special_reg_lr_ = rt_val;
+      } else if (spr == 288) {
+        special_reg_ctr_ = rt_val;
+      } else if (spr == 32) {
+        special_reg_xer_ = rt_val;
+      } else {
+        UNIMPLEMENTED();  // Only LR supported
+      }
+      break;
+    }
+    case MFCR: {
+      int rt = instr->RTValue();
+      set_register(rt, condition_reg_);
+      break;
+    }
+    case STWUX:
+    case STWX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int32_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      WriteW(ra_val+rb_val, rs_val, instr);
+      if (opcode == STWUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case STBUX:
+    case STBX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int8_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      WriteB(ra_val+rb_val, rs_val);
+      if (opcode == STBUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case STHUX:
+    case STHX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int16_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      WriteH(ra_val+rb_val, rs_val, instr);
+      if (opcode == STHUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case LWZX:
+    case LWZUX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      set_register(rt, ReadWU(ra_val+rb_val, instr));
+      if (opcode == LWZUX) {
+        ASSERT(ra != 0 && ra != rt);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+#if V8_TARGET_ARCH_PPC64
+    case LDX:
+    case LDUX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      intptr_t *result = ReadDW(ra_val+rb_val);
+      set_register(rt, *result);
+      if (opcode == LDUX) {
+        ASSERT(ra != 0 && ra != rt);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case STDX:
+    case STDUX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      WriteDW(ra_val+rb_val, rs_val);
+      if (opcode == STDUX) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+#endif
+    case LBZX:
+    case LBZUX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      set_register(rt, ReadBU(ra_val+rb_val) & 0xFF);
+      if (opcode == LBZUX) {
+        ASSERT(ra != 0 && ra != rt);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case LHZX:
+    case LHZUX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rb_val = get_register(rb);
+      set_register(rt, ReadHU(ra_val+rb_val, instr) & 0xFFFF);
+      if (opcode == LHZUX) {
+        ASSERT(ra != 0 && ra != rt);
+        set_register(ra, ra_val+rb_val);
+      }
+      break;
+    }
+    case DCBF: {
+      // todo - simulate dcbf
+      break;
+    }
+    default: {
+      PrintF("Unimplemented: %08x\n", instr->InstructionBits());
+      UNIMPLEMENTED();  // Not used by V8.
+    }
+  }
+}
+
+
+void Simulator::ExecuteExt2(Instruction* instr) {
+    // Check first the 10-1 bit versions
+    if (ExecuteExt2_10bit(instr))
+        return;
+    // Now look at the lesser encodings
+    if (ExecuteExt2_9bit_part1(instr))
+        return;
+    ExecuteExt2_9bit_part2(instr);
+}
+
+
+void Simulator::ExecuteExt4(Instruction* instr) {
+  switch (instr->Bits(5, 1) << 1) {
+    case FDIV: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = fra_val / frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FSUB: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = fra_val - frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FADD: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = fra_val + frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FSQRT: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = std::sqrt(frb_val);
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FSEL: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      int frc = instr->RCValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frc_val = get_double_from_d_register(frc);
+      double frt_val = ((fra_val >= 0.0) ? frc_val : frb_val);
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FMUL: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frc = instr->RCValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frc_val = get_double_from_d_register(frc);
+      double frt_val = fra_val * frc_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FMSUB: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      int frc = instr->RCValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frc_val = get_double_from_d_register(frc);
+      double frt_val = (fra_val * frc_val) - frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FMADD: {
+      int frt = instr->RTValue();
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      int frc = instr->RCValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      double frc_val = get_double_from_d_register(frc);
+      double frt_val = (fra_val * frc_val) + frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+  }
+  int opcode = instr->Bits(10, 1) << 1;
+  switch (opcode) {
+    case FCMPU: {
+      int fra = instr->RAValue();
+      int frb = instr->RBValue();
+      double fra_val = get_double_from_d_register(fra);
+      double frb_val = get_double_from_d_register(frb);
+      int cr = instr->Bits(25, 23);
+      int bf = 0;
+      if (fra_val < frb_val) { bf |= 0x80000000; }
+      if (fra_val > frb_val) { bf |= 0x40000000; }
+      if (fra_val == frb_val) { bf |= 0x20000000; }
+      if (std::isunordered(fra_val, frb_val)) { bf |= 0x10000000; }
+      int condition_mask = 0xF0000000 >> (cr*4);
+      int condition =  bf >> (cr*4);
+      condition_reg_ = (condition_reg_ & ~condition_mask) | condition;
+      return;
+    }
+    case FRSP: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      // frsp round 8-byte double-precision value to 8-byte
+      // single-precision value, ignore the round here
+      set_d_register_from_double(frt, frb_val);
+      if (instr->Bit(0)) {  // RC bit set
+        //  UNIMPLEMENTED();
+      }
+      return;
+    }
+    case FCFID: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double t_val = get_double_from_d_register(frb);
+      int64_t* frb_val_p = reinterpret_cast<int64_t*>(&t_val);
+      double frt_val = static_cast<double>(*frb_val_p);
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FCTID: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      int64_t frt_val;
+      int64_t one = 1;  // work-around gcc
+      int64_t kMinLongLong = (one << 63);
+      int64_t kMaxLongLong = kMinLongLong - 1;
+
+      if (frb_val > kMaxLongLong) {
+        frt_val = kMaxLongLong;
+      } else if (frb_val < kMinLongLong) {
+        frt_val = kMinLongLong;
+      } else {
+        switch (fp_condition_reg_ & kFPRoundingModeMask) {
+          case kRoundToZero:
+            frt_val = (int64_t)frb_val;
+            break;
+          case kRoundToPlusInf:
+            frt_val = (int64_t)std::ceil(frb_val);
+            break;
+          case kRoundToMinusInf:
+            frt_val = (int64_t)std::floor(frb_val);
+            break;
+          default:
+            frt_val = (int64_t)frb_val;
+            UNIMPLEMENTED();  // Not used by V8.
+            break;
+        }
+      }
+      double *p = reinterpret_cast<double*>(&frt_val);
+      set_d_register_from_double(frt, *p);
+      return;
+    }
+    case FCTIDZ: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      int64_t frt_val;
+      int64_t one = 1;  // work-around gcc
+      int64_t kMinLongLong = (one << 63);
+      int64_t kMaxLongLong = kMinLongLong - 1;
+
+      if (frb_val > kMaxLongLong) {
+        frt_val = kMaxLongLong;
+      } else if (frb_val < kMinLongLong) {
+        frt_val = kMinLongLong;
+      } else {
+        frt_val = (int64_t)frb_val;
+      }
+      double *p = reinterpret_cast<double*>(&frt_val);
+      set_d_register_from_double(frt, *p);
+      return;
+    }
+    case FCTIW:
+    case FCTIWZ: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      int64_t frt_val;
+      if (frb_val > kMaxInt) {
+        frt_val = kMaxInt;
+      } else if (frb_val < kMinInt) {
+        frt_val = kMinInt;
+      } else {
+        if (opcode == FCTIWZ) {
+          frt_val = (int64_t)frb_val;
+        } else {
+          switch (fp_condition_reg_ & kFPRoundingModeMask) {
+          case kRoundToZero:
+            frt_val = (int64_t)frb_val;
+            break;
+          case kRoundToPlusInf:
+            frt_val = (int64_t)std::ceil(frb_val);
+            break;
+          case kRoundToMinusInf:
+            frt_val = (int64_t)std::floor(frb_val);
+            break;
+          case kRoundToNearest:
+            frt_val = (int64_t)lround(frb_val);
+
+            // Round to even if exactly halfway.  (lround rounds up)
+            if (std::fabs(static_cast<double>(frt_val) - frb_val) == 0.5 &&
+                (frt_val % 2)) {
+                frt_val += ((frt_val > 0) ? -1 : 1);
+            }
+
+            break;
+          default:
+            ASSERT(false);
+            frt_val = (int64_t)frb_val;
+            break;
+          }
+        }
+      }
+      double *p = reinterpret_cast<double*>(&frt_val);
+      set_d_register_from_double(frt, *p);
+      return;
+    }
+    case FNEG: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = -frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FMR: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = frb_val;
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case MTFSFI: {
+      int bf = instr->Bits(25, 23);
+      int imm = instr->Bits(15, 12);
+      int fp_condition_mask = 0xF0000000 >> (bf*4);
+      fp_condition_reg_ &= ~fp_condition_mask;
+      fp_condition_reg_ |= (imm << (28 - (bf*4)));
+      if (instr->Bit(0)) {  // RC bit set
+        condition_reg_ &= 0xF0FFFFFF;
+        condition_reg_ |= (imm << 23);
+      }
+      return;
+    }
+    case MTFSF: {
+      int frb = instr->RBValue();
+      double frb_dval = get_double_from_d_register(frb);
+      int64_t *p =  reinterpret_cast<int64_t*>(&frb_dval);
+      int32_t frb_ival = static_cast<int32_t>((*p) & 0xffffffff);
+      int l = instr->Bits(25, 25);
+      if (l == 1) {
+        fp_condition_reg_ = frb_ival;
+      } else {
+        UNIMPLEMENTED();
+      }
+      if (instr->Bit(0)) {  // RC bit set
+        UNIMPLEMENTED();
+        // int w = instr->Bits(16, 16);
+        // int flm = instr->Bits(24, 17);
+      }
+      return;
+    }
+    case MFFS: {
+      int frt = instr->RTValue();
+      int64_t lval = static_cast<int64_t>(fp_condition_reg_);
+      double* p = reinterpret_cast<double*>(&lval);
+      set_d_register_from_double(frt, *p);
+      return;
+    }
+    case FABS: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      double frt_val = std::fabs(frb_val);
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+    case FRIM: {
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double frb_val = get_double_from_d_register(frb);
+      int64_t floor_val = (int64_t)frb_val;
+      if (floor_val > frb_val)
+        floor_val--;
+      double frt_val = static_cast<double>(floor_val);
+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
+  }
+  UNIMPLEMENTED();  // Not used by V8.
+}
+
+#if V8_TARGET_ARCH_PPC64
+void Simulator::ExecuteExt5(Instruction* instr) {
+  switch (instr->Bits(4, 2) << 2) {
+    case RLDICL: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uintptr_t rs_val = get_register(rs);
+      int sh = (instr->Bits(15, 11) | (instr->Bit(1) << 5));
+      int mb = (instr->Bits(10, 6) | (instr->Bit(5) << 5));
+      ASSERT(sh >=0 && sh <= 63);
+      ASSERT(mb >=0 && mb <= 63);
+      // rotate left
+      uintptr_t result = (rs_val << sh) | (rs_val >> (64-sh));
+      uintptr_t mask = 0xffffffffffffffff >> mb;
+      result &= mask;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      return;
+    }
+    case RLDICR: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uintptr_t rs_val = get_register(rs);
+      int sh = (instr->Bits(15, 11) | (instr->Bit(1) << 5));
+      int me = (instr->Bits(10, 6) | (instr->Bit(5) << 5));
+      ASSERT(sh >=0 && sh <= 63);
+      ASSERT(me >=0 && me <= 63);
+      // rotate left
+      uintptr_t result = (rs_val << sh) | (rs_val >> (64-sh));
+      uintptr_t mask = 0xffffffffffffffff << (63-me);
+      result &= mask;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      return;
+    }
+    case RLDIC: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uintptr_t rs_val = get_register(rs);
+      int sh = (instr->Bits(15, 11) | (instr->Bit(1) << 5));
+      int mb = (instr->Bits(10, 6) | (instr->Bit(5) << 5));
+      ASSERT(sh >=0 && sh <= 63);
+      ASSERT(mb >=0 && mb <= 63);
+      // rotate left
+      uintptr_t result = (rs_val << sh) | (rs_val >> (64-sh));
+      uintptr_t mask = (0xffffffffffffffff >> mb) & (0xffffffffffffffff << sh);
+      result &= mask;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      return;
+    }
+    case RLDIMI: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uintptr_t rs_val = get_register(rs);
+      intptr_t ra_val = get_register(ra);
+      int sh = (instr->Bits(15, 11) | (instr->Bit(1) << 5));
+      int mb = (instr->Bits(10, 6) | (instr->Bit(5) << 5));
+      int me = 63 - sh;
+      // rotate left
+      uintptr_t result = (rs_val << sh) | (rs_val >> (64-sh));
+      uintptr_t mask = 0;
+      if (mb < me+1) {
+        uintptr_t bit = 0x8000000000000000 >> mb;
+        for (; mb <= me; mb++) {
+          mask |= bit;
+          bit >>= 1;
+        }
+      } else if (mb == me+1) {
+         mask = 0xffffffffffffffff;
+      } else {  // mb > me+1
+        uintptr_t bit = 0x8000000000000000 >> (me+1);  // needs to be tested
+        mask = 0xffffffffffffffff;
+        for (;me < mb;me++) {
+          mask ^= bit;
+          bit >>= 1;
+        }
+      }
+      result &= mask;
+      ra_val &= ~mask;
+      result |= ra_val;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      return;
+    }
+  }
+  switch (instr->Bits(4, 1) << 1) {
+    case RLDCL: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      int rb = instr->RBValue();
+      uintptr_t rs_val = get_register(rs);
+      uintptr_t rb_val = get_register(rb);
+      int sh = (rb_val & 0x3f);
+      int mb = (instr->Bits(10, 6) | (instr->Bit(5) << 5));
+      ASSERT(sh >=0 && sh <= 63);
+      ASSERT(mb >=0 && mb <= 63);
+      // rotate left
+      uintptr_t result = (rs_val << sh) | (rs_val >> (64-sh));
+      uintptr_t mask = 0xffffffffffffffff >> mb;
+      result &= mask;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      return;
+    }
+  }
+  UNIMPLEMENTED();  // Not used by V8.
+}
+#endif
+
+
+void Simulator::ExecuteGeneric(Instruction* instr) {
+  int opcode = instr->OpcodeValue() << 26;
+  switch (opcode) {
+    case SUBFIC: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      intptr_t ra_val = get_register(ra);
+      int32_t im_val = instr->Bits(15, 0);
+      im_val = SIGN_EXT_IMM16(im_val);
+      intptr_t alu_out = im_val - ra_val;
+      set_register(rt, alu_out);
+      // todo - handle RC bit
+      break;
+    }
+    case CMPLI: {
+      int ra = instr->RAValue();
+      uint32_t im_val = instr->Bits(15, 0);
+      int cr = instr->Bits(25, 23);
+      uint32_t bf = 0;
+#if V8_TARGET_ARCH_PPC64
+      int L = instr->Bit(21);
+      if (L) {
+#endif
+        uintptr_t ra_val = get_register(ra);
+        if (ra_val < im_val) { bf |= 0x80000000; }
+        if (ra_val > im_val) { bf |= 0x40000000; }
+        if (ra_val == im_val) { bf |= 0x20000000; }
+#if V8_TARGET_ARCH_PPC64
+      } else {
+        uint32_t ra_val = get_register(ra);
+        if (ra_val < im_val) { bf |= 0x80000000; }
+        if (ra_val > im_val) { bf |= 0x40000000; }
+        if (ra_val == im_val) { bf |= 0x20000000; }
+      }
+#endif
+      uint32_t condition_mask = 0xF0000000U >> (cr*4);
+      uint32_t condition =  bf >> (cr*4);
+      condition_reg_ = (condition_reg_ & ~condition_mask) | condition;
+      break;
+    }
+    case CMPI: {
+      int ra = instr->RAValue();
+      int32_t im_val = instr->Bits(15, 0);
+      im_val = SIGN_EXT_IMM16(im_val);
+      int cr = instr->Bits(25, 23);
+      uint32_t bf = 0;
+#if V8_TARGET_ARCH_PPC64
+      int L = instr->Bit(21);
+      if (L) {
+#endif
+        intptr_t ra_val = get_register(ra);
+        if (ra_val < im_val) { bf |= 0x80000000; }
+        if (ra_val > im_val) { bf |= 0x40000000; }
+        if (ra_val == im_val) { bf |= 0x20000000; }
+#if V8_TARGET_ARCH_PPC64
+      } else {
+        int32_t ra_val = get_register(ra);
+        if (ra_val < im_val) { bf |= 0x80000000; }
+        if (ra_val > im_val) { bf |= 0x40000000; }
+        if (ra_val == im_val) { bf |= 0x20000000; }
+      }
+#endif
+      uint32_t condition_mask = 0xF0000000U >> (cr*4);
+      uint32_t condition =  bf >> (cr*4);
+      condition_reg_ = (condition_reg_ & ~condition_mask) | condition;
+      break;
+    }
+    case ADDIC: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      uintptr_t ra_val = get_register(ra);
+      uintptr_t im_val = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      uintptr_t alu_out = ra_val + im_val;
+      // Check overflow
+      if (~ra_val < im_val) {
+        special_reg_xer_ = (special_reg_xer_ & ~0xF0000000) | 0x20000000;
+      } else {
+        special_reg_xer_ &= ~0xF0000000;
+      }
+      set_register(rt, alu_out);
+      break;
+    }
+    case ADDI: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int32_t im_val = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      intptr_t alu_out;
+      if (ra == 0) {
+        alu_out = im_val;
+      } else {
+        intptr_t ra_val = get_register(ra);
+        alu_out = ra_val + im_val;
+      }
+      set_register(rt, alu_out);
+      // todo - handle RC bit
+      break;
+    }
+    case ADDIS: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int32_t im_val = (instr->Bits(15, 0) << 16);
+      intptr_t alu_out;
+      if (ra == 0) {  // treat r0 as zero
+        alu_out = im_val;
+      } else {
+        intptr_t ra_val = get_register(ra);
+        alu_out = ra_val + im_val;
+      }
+      set_register(rt, alu_out);
+      break;
+    }
+    case BCX: {
+      ExecuteBranchConditional(instr);
+      break;
+    }
+    case BX: {
+      int offset = (instr->Bits(25, 2) << 8) >> 6;
+      if (instr->Bit(0) == 1) {  // LK flag set
+        special_reg_lr_ = get_pc() + 4;
+      }
+      set_pc(get_pc() + offset);
+      // todo - AA flag
+      break;
+    }
+    case EXT1: {
+      ExecuteExt1(instr);
+      break;
+    }
+    case RLWIMIX: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uint32_t rs_val = get_register(rs);
+      int32_t ra_val = get_register(ra);
+      int sh = instr->Bits(15, 11);
+      int mb = instr->Bits(10, 6);
+      int me = instr->Bits(5, 1);
+      // rotate left
+      uint32_t result = (rs_val << sh) | (rs_val >> (32-sh));
+      int mask = 0;
+      if (mb < me+1) {
+        int bit = 0x80000000 >> mb;
+        for (; mb <= me; mb++) {
+          mask |= bit;
+          bit >>= 1;
+        }
+      } else if (mb == me+1) {
+         mask = 0xffffffff;
+      } else {  // mb > me+1
+        int bit = 0x80000000 >> (me+1);  // needs to be tested
+        mask = 0xffffffff;
+        for (;me < mb;me++) {
+          mask ^= bit;
+          bit >>= 1;
+        }
+      }
+      result &= mask;
+      ra_val &= ~mask;
+      result |= ra_val;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+    case RLWINMX:
+    case RLWNMX: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      uint32_t rs_val = get_register(rs);
+      int sh = 0;
+      if (opcode == RLWINMX) {
+        sh = instr->Bits(15, 11);
+      } else {
+        int rb = instr->RBValue();
+        uint32_t rb_val = get_register(rb);
+        sh = (rb_val & 0x1f);
+      }
+      int mb = instr->Bits(10, 6);
+      int me = instr->Bits(5, 1);
+      // rotate left
+      uint32_t result = (rs_val << sh) | (rs_val >> (32-sh));
+      int mask = 0;
+      if (mb < me+1) {
+        int bit = 0x80000000 >> mb;
+        for (; mb <= me; mb++) {
+          mask |= bit;
+          bit >>= 1;
+        }
+      } else if (mb == me+1) {
+         mask = 0xffffffff;
+      } else {  // mb > me+1
+        int bit = 0x80000000 >> (me+1);  // needs to be tested
+        mask = 0xffffffff;
+        for (;me < mb;me++) {
+          mask ^= bit;
+          bit >>= 1;
+        }
+      }
+      result &= mask;
+      set_register(ra, result);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(result);
+      }
+      break;
+    }
+    case ORI: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val | im_val;
+      set_register(ra, alu_out);
+      break;
+    }
+    case ORIS: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val | (im_val << 16);
+      set_register(ra, alu_out);
+      break;
+    }
+    case XORI: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val ^ im_val;
+      set_register(ra, alu_out);
+      // todo - set condition based SO bit
+      break;
+    }
+    case XORIS: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val ^ (im_val << 16);
+      set_register(ra, alu_out);
+      break;
+    }
+    case ANDIx: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val & im_val;
+      set_register(ra, alu_out);
+      SetCR0(alu_out);
+      break;
+    }
+    case ANDISx: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      intptr_t rs_val = get_register(rs);
+      uint32_t im_val = instr->Bits(15, 0);
+      intptr_t alu_out = rs_val & (im_val << 16);
+      set_register(ra, alu_out);
+      SetCR0(alu_out);
+      break;
+    }
+    case EXT2: {
+      ExecuteExt2(instr);
+      break;
+    }
+
+    case LWZU:
+    case LWZ: {
+      int ra = instr->RAValue();
+      int rt = instr->RTValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      set_register(rt, ReadWU(ra_val+offset, instr));
+      if (opcode == LWZU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case LBZU:
+    case LBZ: {
+      int ra = instr->RAValue();
+      int rt = instr->RTValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      set_register(rt, ReadB(ra_val+offset) & 0xFF);
+      if (opcode == LBZU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case STWU:
+    case STW: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int32_t rs_val = get_register(rs);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      WriteW(ra_val+offset, rs_val, instr);
+      if (opcode == STWU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      // printf("r%d %08x -> %08x\n", rs, rs_val, offset); // 0xdead
+      break;
+    }
+
+    case STBU:
+    case STB: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int8_t rs_val = get_register(rs);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      WriteB(ra_val+offset, rs_val);
+      if (opcode == STBU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case LHZU:
+    case LHZ: {
+      int ra = instr->RAValue();
+      int rt = instr->RTValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      uintptr_t result = ReadHU(ra_val+offset, instr) & 0xffff;
+      set_register(rt, result);
+      if (opcode == LHZU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case LHA:
+    case LHAU: {
+      UNIMPLEMENTED();
+      break;
+    }
+
+    case STHU:
+    case STH: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int16_t rs_val = get_register(rs);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      WriteH(ra_val+offset, rs_val, instr);
+      if (opcode == STHU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case LMW:
+    case STMW: {
+      UNIMPLEMENTED();
+      break;
+    }
+
+    case LFSU:
+    case LFS: {
+     int frt = instr->RTValue();
+      int ra = instr->RAValue();
+      int32_t offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int32_t val = ReadW(ra_val + offset, instr);
+      float *fptr = reinterpret_cast<float*>(&val);
+      set_d_register_from_double(frt, static_cast<double>(*fptr));
+      if (opcode == LFSU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case LFDU:
+    case LFD: {
+      int frt = instr->RTValue();
+      int ra = instr->RAValue();
+      int32_t offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      double *dptr = reinterpret_cast<double*>(ReadDW(ra_val + offset));
+      set_d_register_from_double(frt, *dptr);
+      if (opcode == LFDU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case STFSU: {
+    case STFS:
+      int frs = instr->RSValue();
+      int ra = instr->RAValue();
+      int32_t offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      float frs_val = static_cast<float>(get_double_from_d_register(frs));
+      int32_t *p=  reinterpret_cast<int32_t*>(&frs_val);
+      WriteW(ra_val + offset, *p, instr);
+      if (opcode == STFSU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case STFDU:
+    case STFD: {
+      int frs = instr->RSValue();
+      int ra = instr->RAValue();
+      int32_t offset = SIGN_EXT_IMM16(instr->Bits(15, 0));
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      double frs_val = get_double_from_d_register(frs);
+      int64_t *p = reinterpret_cast<int64_t *>(&frs_val);
+      WriteDW(ra_val + offset, *p);
+      if (opcode == STFDU) {
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+
+    case EXT3:
+      UNIMPLEMENTED();
+    case EXT4: {
+      ExecuteExt4(instr);
+      break;
+    }
+
+#if V8_TARGET_ARCH_PPC64
+    case EXT5: {
+      ExecuteExt5(instr);
+      break;
+    }
+    case LD: {
+      int ra = instr->RAValue();
+      int rt = instr->RTValue();
+      int64_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0) & ~3);
+      switch  (instr->Bits(1, 0)) {
+        case 0:  {  // ld
+          intptr_t *result = ReadDW(ra_val+offset);
+          set_register(rt, *result);
+          break;
+        }
+        case 1: {  // ldu
+          intptr_t *result = ReadDW(ra_val+offset);
+          set_register(rt, *result);
+          ASSERT(ra != 0);
+          set_register(ra, ra_val+offset);
+          break;
+        }
+        case 2: {  // lwa
+          intptr_t result = ReadW(ra_val+offset, instr);
+          set_register(rt, result);
+          break;
+        }
+      }
+      break;
+    }
+
+    case STD: {
+      int ra = instr->RAValue();
+      int rs = instr->RSValue();
+      int64_t ra_val = ra == 0 ? 0 : get_register(ra);
+      int64_t rs_val = get_register(rs);
+      int offset = SIGN_EXT_IMM16(instr->Bits(15, 0) & ~3);
+      WriteDW(ra_val+offset, rs_val);
+      if (instr->Bit(0) == 1) {  // This is the STDU form
+        ASSERT(ra != 0);
+        set_register(ra, ra_val+offset);
+      }
+      break;
+    }
+#endif
+
+    case FAKE_OPCODE: {
+      if (instr->Bits(MARKER_SUBOPCODE_BIT, MARKER_SUBOPCODE_BIT) == 1) {
+        int marker_code = instr->Bits(STUB_MARKER_HIGH_BIT, 0);
+        ASSERT(marker_code < F_NEXT_AVAILABLE_STUB_MARKER);
+        PrintF("Hit stub-marker: %d (EMIT_STUB_MARKER)\n",
+               marker_code);
+      } else {
+        int fake_opcode = instr->Bits(FAKE_OPCODE_HIGH_BIT, 0);
+        if (fake_opcode == fBKPT) {
+          PPCDebugger dbg(this);
+          PrintF("Simulator hit BKPT.\n");
+          dbg.Debug();
+        } else {
+          ASSERT(fake_opcode < fLastFaker);
+          PrintF("Hit ARM opcode: %d(FAKE_OPCODE defined in constant-ppc.h)\n",
+                 fake_opcode);
+          UNIMPLEMENTED();
+        }
+      }
+      break;
+    }
+
+    default: {
+      UNIMPLEMENTED();
+      break;
+    }
+  }
+}
+
+
+void Simulator::Trace(Instruction *instr) {
+  disasm::NameConverter converter;
+  disasm::Disassembler dasm(converter);
+  // use a reasonably large buffer
+  v8::internal::EmbeddedVector<char, 256> buffer;
+  dasm.InstructionDecode(buffer, reinterpret_cast<byte*>(instr));
+  PrintF("%05d  %08" V8PRIxPTR "  %s\n", icount_,
+         reinterpret_cast<intptr_t>(instr), buffer.start());
+}
+
+
+// Executes the current instruction.
+void Simulator::ExecuteInstruction(Instruction* instr) {
+  if (v8::internal::FLAG_check_icache) {
+    CheckICache(isolate_->simulator_i_cache(), instr);
+  }
+  pc_modified_ = false;
+  if (::v8::internal::FLAG_trace_sim) {
+    Trace(instr);
+  }
+  int opcode = instr->OpcodeValue() << 26;
+  if (opcode == TWI) {
+    SoftwareInterrupt(instr);
+  } else {
+    ExecuteGeneric(instr);
+  }
+  if (!pc_modified_) {
+    set_pc(reinterpret_cast<intptr_t>(instr) + Instruction::kInstrSize);
+  }
+}
+
+
+void Simulator::Execute() {
+  // Get the PC to simulate. Cannot use the accessor here as we need the
+  // raw PC value and not the one used as input to arithmetic instructions.
+  intptr_t program_counter = get_pc();
+
+  if (::v8::internal::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 (program_counter != end_sim_pc) {
+      Instruction* instr = reinterpret_cast<Instruction*>(program_counter);
+      icount_++;
+      ExecuteInstruction(instr);
+      program_counter = get_pc();
+    }
+  } else {
+    // FLAG_stop_sim_at is at the non-default value. Stop in the debugger when
+    // we reach the particular instuction count.
+    while (program_counter != end_sim_pc) {
+      Instruction* instr = reinterpret_cast<Instruction*>(program_counter);
+      icount_++;
+      if (icount_ == ::v8::internal::FLAG_stop_sim_at) {
+        PPCDebugger dbg(this);
+        dbg.Debug();
+      } else {
+        ExecuteInstruction(instr);
+      }
+      program_counter = get_pc();
+    }
+  }
+}
+
+
+void Simulator::CallInternal(byte *entry) {
+  // Prepare to execute the code at entry
+#if ABI_USES_FUNCTION_DESCRIPTORS
+  // entry is the function descriptor
+  set_pc(*(reinterpret_cast<intptr_t *>(entry)));
+#else
+  // entry is the instruction address
+  set_pc(reinterpret_cast<intptr_t>(entry));
+#endif
+
+  // Put down marker for end of simulation. The simulator will stop simulation
+  // when the PC reaches this value. By saving the "end simulation" value into
+  // the LR the simulation stops when returning to this call point.
+  special_reg_lr_ = end_sim_pc;
+
+  // Remember the values of non-volatile registers.
+  intptr_t r2_val = get_register(r2);
+  intptr_t r13_val = get_register(r13);
+  intptr_t r14_val = get_register(r14);
+  intptr_t r15_val = get_register(r15);
+  intptr_t r16_val = get_register(r16);
+  intptr_t r17_val = get_register(r17);
+  intptr_t r18_val = get_register(r18);
+  intptr_t r19_val = get_register(r19);
+  intptr_t r20_val = get_register(r20);
+  intptr_t r21_val = get_register(r21);
+  intptr_t r22_val = get_register(r22);
+  intptr_t r23_val = get_register(r23);
+  intptr_t r24_val = get_register(r24);
+  intptr_t r25_val = get_register(r25);
+  intptr_t r26_val = get_register(r26);
+  intptr_t r27_val = get_register(r27);
+  intptr_t r28_val = get_register(r28);
+  intptr_t r29_val = get_register(r29);
+  intptr_t r30_val = get_register(r30);
+  intptr_t r31_val = get_register(fp);
+
+  // Set up the non-volatile registers with a known value. To be able to check
+  // that they are preserved properly across JS execution.
+  intptr_t callee_saved_value = icount_;
+  set_register(r2, callee_saved_value);
+  set_register(r13, callee_saved_value);
+  set_register(r14, callee_saved_value);
+  set_register(r15, callee_saved_value);
+  set_register(r16, callee_saved_value);
+  set_register(r17, callee_saved_value);
+  set_register(r18, callee_saved_value);
+  set_register(r19, callee_saved_value);
+  set_register(r20, callee_saved_value);
+  set_register(r21, callee_saved_value);
+  set_register(r22, callee_saved_value);
+  set_register(r23, callee_saved_value);
+  set_register(r24, callee_saved_value);
+  set_register(r25, callee_saved_value);
+  set_register(r26, callee_saved_value);
+  set_register(r27, callee_saved_value);
+  set_register(r28, callee_saved_value);
+  set_register(r29, callee_saved_value);
+  set_register(r30, callee_saved_value);
+  set_register(fp, callee_saved_value);
+
+  // Start the simulation
+  Execute();
+
+  // Check that the non-volatile registers have been preserved.
+  CHECK_EQ(callee_saved_value, get_register(r2));
+  CHECK_EQ(callee_saved_value, get_register(r13));
+  CHECK_EQ(callee_saved_value, get_register(r14));
+  CHECK_EQ(callee_saved_value, get_register(r15));
+  CHECK_EQ(callee_saved_value, get_register(r16));
+  CHECK_EQ(callee_saved_value, get_register(r17));
+  CHECK_EQ(callee_saved_value, get_register(r18));
+  CHECK_EQ(callee_saved_value, get_register(r19));
+  CHECK_EQ(callee_saved_value, get_register(r20));
+  CHECK_EQ(callee_saved_value, get_register(r21));
+  CHECK_EQ(callee_saved_value, get_register(r22));
+  CHECK_EQ(callee_saved_value, get_register(r23));
+  CHECK_EQ(callee_saved_value, get_register(r24));
+  CHECK_EQ(callee_saved_value, get_register(r25));
+  CHECK_EQ(callee_saved_value, get_register(r26));
+  CHECK_EQ(callee_saved_value, get_register(r27));
+  CHECK_EQ(callee_saved_value, get_register(r28));
+  CHECK_EQ(callee_saved_value, get_register(r29));
+  CHECK_EQ(callee_saved_value, get_register(r30));
+  CHECK_EQ(callee_saved_value, get_register(fp));
+
+  // Restore non-volatile registers with the original value.
+  set_register(r2, r2_val);
+  set_register(r13, r13_val);
+  set_register(r14, r14_val);
+  set_register(r15, r15_val);
+  set_register(r16, r16_val);
+  set_register(r17, r17_val);
+  set_register(r18, r18_val);
+  set_register(r19, r19_val);
+  set_register(r20, r20_val);
+  set_register(r21, r21_val);
+  set_register(r22, r22_val);
+  set_register(r23, r23_val);
+  set_register(r24, r24_val);
+  set_register(r25, r25_val);
+  set_register(r26, r26_val);
+  set_register(r27, r27_val);
+  set_register(r28, r28_val);
+  set_register(r29, r29_val);
+  set_register(r30, r30_val);
+  set_register(fp, r31_val);
+}
+
+
+intptr_t Simulator::Call(byte* entry, int argument_count, ...) {
+  va_list parameters;
+  va_start(parameters, argument_count);
+  // Set up arguments
+
+  // First eight arguments passed in registers r3-r10.
+  int reg_arg_count   = (argument_count > 8) ? 8 : argument_count;
+  int stack_arg_count = argument_count - reg_arg_count;
+  for (int i = 0; i < reg_arg_count; i++) {
+      set_register(i + 3, va_arg(parameters, intptr_t));
+  }
+
+  // Remaining arguments passed on stack.
+  intptr_t original_stack = get_register(sp);
+  // Compute position of stack on entry to generated code.
+  intptr_t entry_stack = (original_stack -
+                          (kNumRequiredStackFrameSlots + stack_arg_count) *
+                          sizeof(intptr_t));
+  if (base::OS::ActivationFrameAlignment() != 0) {
+    entry_stack &= -base::OS::ActivationFrameAlignment();
+  }
+  // Store remaining arguments on stack, from low to high memory.
+  // +2 is a hack for the LR slot + old SP on PPC
+  intptr_t* stack_argument = reinterpret_cast<intptr_t*>(entry_stack) +
+    kStackFrameExtraParamSlot;
+  for (int i = 0; i < stack_arg_count; i++) {
+    stack_argument[i] = va_arg(parameters, intptr_t);
+  }
+  va_end(parameters);
+  set_register(sp, entry_stack);
+
+  CallInternal(entry);
+
+  // Pop stack passed arguments.
+  CHECK_EQ(entry_stack, get_register(sp));
+  set_register(sp, original_stack);
+
+  intptr_t result = get_register(r3);
+  return result;
+}
+
+
+void Simulator::CallFP(byte* entry, double d0, double d1) {
+  set_d_register_from_double(1, d0);
+  set_d_register_from_double(2, d1);
+  CallInternal(entry);
+}
+
+
+int32_t Simulator::CallFPReturnsInt(byte* entry, double d0, double d1) {
+  CallFP(entry, d0, d1);
+  int32_t result = get_register(r3);
+  return result;
+}
+
+
+double Simulator::CallFPReturnsDouble(byte* entry, double d0, double d1) {
+  CallFP(entry, d0, d1);
+  return get_double_from_d_register(1);
+}
+
+
+uintptr_t Simulator::PushAddress(uintptr_t address) {
+  uintptr_t new_sp = get_register(sp) - sizeof(uintptr_t);
+  uintptr_t* stack_slot = reinterpret_cast<uintptr_t*>(new_sp);
+  *stack_slot = address;
+  set_register(sp, new_sp);
+  return new_sp;
+}
+
+
+uintptr_t Simulator::PopAddress() {
+  uintptr_t current_sp = get_register(sp);
+  uintptr_t* stack_slot = reinterpret_cast<uintptr_t*>(current_sp);
+  uintptr_t address = *stack_slot;
+  set_register(sp, current_sp + sizeof(uintptr_t));
+  return address;
+}
+
+} }  // namespace v8::internal
+
+#endif  // USE_SIMULATOR
+#endif  // V8_TARGET_ARCH_PPC