// Copyright 2009 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#include "bootstrapper.h"
#include "codegen-inl.h"
#include "assembler-x64.h"
#include "macro-assembler-x64.h"
#include "debug.h"

namespace v8 {
namespace internal {

MacroAssembler::MacroAssembler(void* buffer, int size)
  : Assembler(buffer, size),
    unresolved_(0),
    generating_stub_(false),
    allow_stub_calls_(true),
    code_object_(Heap::undefined_value()) {
}


void MacroAssembler::Assert(Condition cc, const char* msg) {
  if (FLAG_debug_code) Check(cc, msg);
}


void MacroAssembler::Check(Condition cc, const char* msg) {
  Label L;
  j(cc, &L);
  Abort(msg);
  // will not return here
  bind(&L);
}


void MacroAssembler::NegativeZeroTest(Register result,
                                      Register op,
                                      Label* then_label) {
  Label ok;
  testq(result, result);
  j(not_zero, &ok);
  testq(op, op);
  j(sign, then_label);
  bind(&ok);
}


void MacroAssembler::ConstructAndTestJSFunction() {
  const int initial_buffer_size = 4 * KB;
  char* buffer = new char[initial_buffer_size];
  MacroAssembler masm(buffer, initial_buffer_size);

  const uint64_t secret = V8_INT64_C(0xdeadbeefcafebabe);
  Handle<String> constant =
      Factory::NewStringFromAscii(Vector<const char>("451", 3), TENURED);
#define __ ACCESS_MASM((&masm))
  // Construct a simple JSfunction here, using Assembler and MacroAssembler
  // commands.
  __ movq(rax, constant, RelocInfo::EMBEDDED_OBJECT);
  __ push(rax);
  __ CallRuntime(Runtime::kStringParseFloat, 1);
  __ movq(kScratchRegister, secret, RelocInfo::NONE);
  __ addq(rax, kScratchRegister);
  __ ret(0);
#undef __
  CodeDesc desc;
  masm.GetCode(&desc);
  Code::Flags flags = Code::ComputeFlags(Code::FUNCTION);
  Object* code = Heap::CreateCode(desc, NULL, flags, Handle<Object>::null());
  if (!code->IsFailure()) {
    Handle<Code> code_handle(Code::cast(code));
    Handle<String> name =
        Factory::NewStringFromAscii(Vector<const char>("foo", 3), NOT_TENURED);
    Handle<JSFunction> function =
        Factory::NewFunction(name,
                             JS_FUNCTION_TYPE,
                             JSObject::kHeaderSize,
                             code_handle,
                             true);
    bool pending_exceptions;
    Handle<Object> result =
        Execution::Call(function,
                        Handle<Object>::cast(function),
                        0,
                        NULL,
                        &pending_exceptions);
    CHECK(result->IsSmi());
    CHECK(secret + (451 << kSmiTagSize) == reinterpret_cast<uint64_t>(*result));
  }
}


void MacroAssembler::Abort(const char* msg) {
  // We want to pass the msg string like a smi to avoid GC
  // problems, however msg is not guaranteed to be aligned
  // properly. Instead, we pass an aligned pointer that is
  // a proper v8 smi, but also pass the alignment difference
  // from the real pointer as a smi.
  intptr_t p1 = reinterpret_cast<intptr_t>(msg);
  intptr_t p0 = (p1 & ~kSmiTagMask) + kSmiTag;
  // Note: p0 might not be a valid Smi *value*, but it has a valid Smi tag.
  ASSERT(reinterpret_cast<Object*>(p0)->IsSmi());
#ifdef DEBUG
  if (msg != NULL) {
    RecordComment("Abort message: ");
    RecordComment(msg);
  }
#endif
  push(rax);
  movq(kScratchRegister, p0, RelocInfo::NONE);
  push(kScratchRegister);
  movq(kScratchRegister,
       reinterpret_cast<intptr_t>(Smi::FromInt(p1 - p0)),
       RelocInfo::NONE);
  push(kScratchRegister);
  CallRuntime(Runtime::kAbort, 2);
  // will not return here
}


void MacroAssembler::CallStub(CodeStub* stub) {
  ASSERT(allow_stub_calls());  // calls are not allowed in some stubs
  movq(kScratchRegister, stub->GetCode(), RelocInfo::CODE_TARGET);
  call(kScratchRegister);
}


void MacroAssembler::StubReturn(int argc) {
  ASSERT(argc >= 1 && generating_stub());
  ret((argc - 1) * kPointerSize);
}


void MacroAssembler::IllegalOperation(int num_arguments) {
  if (num_arguments > 0) {
    addq(rsp, Immediate(num_arguments * kPointerSize));
  }
  movq(rax, Factory::undefined_value(), RelocInfo::EMBEDDED_OBJECT);
}


void MacroAssembler::CallRuntime(Runtime::FunctionId id, int num_arguments) {
  CallRuntime(Runtime::FunctionForId(id), num_arguments);
}


void MacroAssembler::CallRuntime(Runtime::Function* f, int num_arguments) {
  // If the expected number of arguments of the runtime function is
  // constant, we check that the actual number of arguments match the
  // expectation.
  if (f->nargs >= 0 && f->nargs != num_arguments) {
    IllegalOperation(num_arguments);
    return;
  }

  Runtime::FunctionId function_id =
      static_cast<Runtime::FunctionId>(f->stub_id);
  RuntimeStub stub(function_id, num_arguments);
  CallStub(&stub);
}


void MacroAssembler::TailCallRuntime(ExternalReference const& ext,
                                     int num_arguments) {
  // TODO(1236192): Most runtime routines don't need the number of
  // arguments passed in because it is constant. At some point we
  // should remove this need and make the runtime routine entry code
  // smarter.
  movq(rax, Immediate(num_arguments));
  JumpToBuiltin(ext);
}


void MacroAssembler::JumpToBuiltin(const ExternalReference& ext) {
  // Set the entry point and jump to the C entry runtime stub.
  movq(rbx, ext);
  CEntryStub ces;
  movq(kScratchRegister, ces.GetCode(), RelocInfo::CODE_TARGET);
  jmp(kScratchRegister);
}


void MacroAssembler::GetBuiltinEntry(Register target, Builtins::JavaScript id) {
  bool resolved;
  Handle<Code> code = ResolveBuiltin(id, &resolved);

  const char* name = Builtins::GetName(id);
  int argc = Builtins::GetArgumentsCount(id);

  movq(target, code, RelocInfo::EXTERNAL_REFERENCE);  // Is external reference?
  if (!resolved) {
    uint32_t flags =
        Bootstrapper::FixupFlagsArgumentsCount::encode(argc) |
        Bootstrapper::FixupFlagsIsPCRelative::encode(false) |
        Bootstrapper::FixupFlagsUseCodeObject::encode(true);
    Unresolved entry = { pc_offset() - sizeof(intptr_t), flags, name };
    unresolved_.Add(entry);
  }
  addq(target, Immediate(Code::kHeaderSize - kHeapObjectTag));
}


Handle<Code> MacroAssembler::ResolveBuiltin(Builtins::JavaScript id,
                                            bool* resolved) {
  // Move the builtin function into the temporary function slot by
  // reading it from the builtins object. NOTE: We should be able to
  // reduce this to two instructions by putting the function table in
  // the global object instead of the "builtins" object and by using a
  // real register for the function.
  movq(rdx, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
  movq(rdx, FieldOperand(rdx, GlobalObject::kBuiltinsOffset));
  int builtins_offset =
      JSBuiltinsObject::kJSBuiltinsOffset + (id * kPointerSize);
  movq(rdi, FieldOperand(rdx, builtins_offset));


  return Builtins::GetCode(id, resolved);
}


void MacroAssembler::Set(Register dst, int64_t x) {
  if (is_int32(x)) {
    movq(dst, Immediate(x));
  } else if (is_uint32(x)) {
    movl(dst, Immediate(x));
  } else {
    movq(dst, x, RelocInfo::NONE);
  }
}


void MacroAssembler::Set(const Operand& dst, int64_t x) {
  if (is_int32(x)) {
    movq(kScratchRegister, Immediate(x));
  } else if (is_uint32(x)) {
    movl(kScratchRegister, Immediate(x));
  } else {
    movq(kScratchRegister, x, RelocInfo::NONE);
  }
  movq(dst, kScratchRegister);
}


bool MacroAssembler::IsUnsafeSmi(Smi* value) {
  return false;
}

void MacroAssembler::LoadUnsafeSmi(Register dst, Smi* source) {
  UNIMPLEMENTED();
}


void MacroAssembler::Move(Register dst, Handle<Object> source) {
  if (source->IsSmi()) {
    if (IsUnsafeSmi(source)) {
      LoadUnsafeSmi(dst, source);
    } else {
      movq(dst, source, RelocInfo::NONE);
    }
  } else {
    movq(dst, source, RelocInfo::EMBEDDED_OBJECT);
  }
}


void MacroAssembler::Move(const Operand& dst, Handle<Object> source) {
  Move(kScratchRegister, source);
  movq(dst, kScratchRegister);
}


void MacroAssembler::Cmp(Register dst, Handle<Object> source) {
  Move(kScratchRegister, source);
  cmpq(dst, kScratchRegister);
}


void MacroAssembler::Jump(ExternalReference ext) {
  movq(kScratchRegister, ext);
  jmp(kScratchRegister);
}


void MacroAssembler::Jump(Address destination, RelocInfo::Mode rmode) {
  movq(kScratchRegister, destination, rmode);
  jmp(kScratchRegister);
}


void MacroAssembler::Jump(Handle<Code> code_object, RelocInfo::Mode rmode) {
  WriteRecordedPositions();
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  movq(kScratchRegister, code_object, rmode);
  jmp(kScratchRegister);
}


void MacroAssembler::Call(ExternalReference ext) {
  movq(kScratchRegister, ext);
  call(kScratchRegister);
}


void MacroAssembler::Call(Address destination, RelocInfo::Mode rmode) {
  movq(kScratchRegister, destination, rmode);
  call(kScratchRegister);
}


void MacroAssembler::Call(Handle<Code> code_object, RelocInfo::Mode rmode) {
  WriteRecordedPositions();
  ASSERT(RelocInfo::IsCodeTarget(rmode));
  movq(kScratchRegister, code_object, rmode);
#ifdef DEBUG
  Label target;
  bind(&target);
#endif
  call(kScratchRegister);
#ifdef DEBUG
  ASSERT_EQ(kTargetAddrToReturnAddrDist,
            SizeOfCodeGeneratedSince(&target) + kPointerSize);
#endif
}


void MacroAssembler::PushTryHandler(CodeLocation try_location,
                                    HandlerType type) {
  // Adjust this code if not the case.
  ASSERT(StackHandlerConstants::kSize == 4 * kPointerSize);

  // The pc (return address) is already on TOS.  This code pushes state,
  // frame pointer and current handler.  Check that they are expected
  // next on the stack, in that order.
  ASSERT_EQ(StackHandlerConstants::kStateOffset,
            StackHandlerConstants::kPCOffset - kPointerSize);
  ASSERT_EQ(StackHandlerConstants::kFPOffset,
            StackHandlerConstants::kStateOffset - kPointerSize);
  ASSERT_EQ(StackHandlerConstants::kNextOffset,
            StackHandlerConstants::kFPOffset - kPointerSize);

  if (try_location == IN_JAVASCRIPT) {
    if (type == TRY_CATCH_HANDLER) {
      push(Immediate(StackHandler::TRY_CATCH));
    } else {
      push(Immediate(StackHandler::TRY_FINALLY));
    }
    push(rbp);
  } else {
    ASSERT(try_location == IN_JS_ENTRY);
    // The frame pointer does not point to a JS frame so we save NULL
    // for rbp. We expect the code throwing an exception to check rbp
    // before dereferencing it to restore the context.
    push(Immediate(StackHandler::ENTRY));
    push(Immediate(0));  // NULL frame pointer.
  }
  // Save the current handler.
  movq(kScratchRegister, ExternalReference(Top::k_handler_address));
  push(Operand(kScratchRegister, 0));
  // Link this handler.
  movq(Operand(kScratchRegister, 0), rsp);
}


void MacroAssembler::Ret() {
  ret(0);
}


void MacroAssembler::CmpObjectType(Register heap_object,
                                   InstanceType type,
                                   Register map) {
  movq(map, FieldOperand(heap_object, HeapObject::kMapOffset));
  CmpInstanceType(map, type);
}


void MacroAssembler::CmpInstanceType(Register map, InstanceType type) {
  cmpb(FieldOperand(map, Map::kInstanceTypeOffset),
       Immediate(static_cast<int8_t>(type)));
}



void MacroAssembler::SetCounter(StatsCounter* counter, int value) {
  if (FLAG_native_code_counters && counter->Enabled()) {
    movq(kScratchRegister, ExternalReference(counter));
    movl(Operand(kScratchRegister, 0), Immediate(value));
  }
}


void MacroAssembler::IncrementCounter(StatsCounter* counter, int value) {
  ASSERT(value > 0);
  if (FLAG_native_code_counters && counter->Enabled()) {
    movq(kScratchRegister, ExternalReference(counter));
    Operand operand(kScratchRegister, 0);
    if (value == 1) {
      incl(operand);
    } else {
      addl(operand, Immediate(value));
    }
  }
}


void MacroAssembler::DecrementCounter(StatsCounter* counter, int value) {
  ASSERT(value > 0);
  if (FLAG_native_code_counters && counter->Enabled()) {
    movq(kScratchRegister, ExternalReference(counter));
    Operand operand(kScratchRegister, 0);
    if (value == 1) {
      decl(operand);
    } else {
      subl(operand, Immediate(value));
    }
  }
}


#ifdef ENABLE_DEBUGGER_SUPPORT

void MacroAssembler::PushRegistersFromMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Push the content of the memory location to the stack.
  for (int i = 0; i < kNumJSCallerSaved; i++) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      movq(kScratchRegister, reg_addr);
      push(Operand(kScratchRegister, 0));
    }
  }
}

void MacroAssembler::SaveRegistersToMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of registers to memory location.
  for (int i = 0; i < kNumJSCallerSaved; i++) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      Register reg = { r };
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      movq(kScratchRegister, reg_addr);
      movq(Operand(kScratchRegister, 0), reg);
    }
  }
}


void MacroAssembler::RestoreRegistersFromMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of memory location to registers.
  for (int i = kNumJSCallerSaved - 1; i >= 0; i--) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      Register reg = { r };
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      movq(kScratchRegister, reg_addr);
      movq(reg, Operand(kScratchRegister, 0));
    }
  }
}


void MacroAssembler::PopRegistersToMemory(RegList regs) {
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Pop the content from the stack to the memory location.
  for (int i = kNumJSCallerSaved - 1; i >= 0; i--) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      movq(kScratchRegister, reg_addr);
      pop(Operand(kScratchRegister, 0));
    }
  }
}


void MacroAssembler::CopyRegistersFromStackToMemory(Register base,
                                                    Register scratch,
                                                    RegList regs) {
  ASSERT(!scratch.is(kScratchRegister));
  ASSERT(!base.is(kScratchRegister));
  ASSERT(!base.is(scratch));
  ASSERT((regs & ~kJSCallerSaved) == 0);
  // Copy the content of the stack to the memory location and adjust base.
  for (int i = kNumJSCallerSaved - 1; i >= 0; i--) {
    int r = JSCallerSavedCode(i);
    if ((regs & (1 << r)) != 0) {
      movq(scratch, Operand(base, 0));
      ExternalReference reg_addr =
          ExternalReference(Debug_Address::Register(i));
      movq(kScratchRegister, reg_addr);
      movq(Operand(kScratchRegister, 0), scratch);
      lea(base, Operand(base, kPointerSize));
    }
  }
}

#endif  // ENABLE_DEBUGGER_SUPPORT


void MacroAssembler::InvokePrologue(const ParameterCount& expected,
                                    const ParameterCount& actual,
                                    Handle<Code> code_constant,
                                    Register code_register,
                                    Label* done,
                                    InvokeFlag flag) {
  bool definitely_matches = false;
  Label invoke;
  if (expected.is_immediate()) {
    ASSERT(actual.is_immediate());
    if (expected.immediate() == actual.immediate()) {
      definitely_matches = true;
    } else {
      movq(rax, Immediate(actual.immediate()));
      if (expected.immediate() ==
          SharedFunctionInfo::kDontAdaptArgumentsSentinel) {
        // Don't worry about adapting arguments for built-ins that
        // don't want that done. Skip adaption code by making it look
        // like we have a match between expected and actual number of
        // arguments.
        definitely_matches = true;
      } else {
        movq(rbx, Immediate(expected.immediate()));
      }
    }
  } else {
    if (actual.is_immediate()) {
      // Expected is in register, actual is immediate. This is the
      // case when we invoke function values without going through the
      // IC mechanism.
      cmpq(expected.reg(), Immediate(actual.immediate()));
      j(equal, &invoke);
      ASSERT(expected.reg().is(rbx));
      movq(rax, Immediate(actual.immediate()));
    } else if (!expected.reg().is(actual.reg())) {
      // Both expected and actual are in (different) registers. This
      // is the case when we invoke functions using call and apply.
      cmpq(expected.reg(), actual.reg());
      j(equal, &invoke);
      ASSERT(actual.reg().is(rax));
      ASSERT(expected.reg().is(rbx));
    }
  }

  if (!definitely_matches) {
    Handle<Code> adaptor =
        Handle<Code>(Builtins::builtin(Builtins::ArgumentsAdaptorTrampoline));
    if (!code_constant.is_null()) {
      movq(rdx, code_constant, RelocInfo::EMBEDDED_OBJECT);
      addq(rdx, Immediate(Code::kHeaderSize - kHeapObjectTag));
    } else if (!code_register.is(rdx)) {
      movq(rdx, code_register);
    }

    movq(kScratchRegister, adaptor, RelocInfo::CODE_TARGET);
    if (flag == CALL_FUNCTION) {
      call(kScratchRegister);
      jmp(done);
    } else {
      jmp(kScratchRegister);
    }
    bind(&invoke);
  }
}




void MacroAssembler::InvokeCode(Register code,
                                const ParameterCount& expected,
                                const ParameterCount& actual,
                                InvokeFlag flag) {
  Label done;
  InvokePrologue(expected, actual, Handle<Code>::null(), code, &done, flag);
  if (flag == CALL_FUNCTION) {
    call(code);
  } else {
    ASSERT(flag == JUMP_FUNCTION);
    jmp(code);
  }
  bind(&done);
}


void MacroAssembler::InvokeCode(Handle<Code> code,
                                const ParameterCount& expected,
                                const ParameterCount& actual,
                                RelocInfo::Mode rmode,
                                InvokeFlag flag) {
  Label done;
  Register dummy = rax;
  InvokePrologue(expected, actual, code, dummy, &done, flag);
  movq(kScratchRegister, code, rmode);
  if (flag == CALL_FUNCTION) {
    call(kScratchRegister);
  } else {
    ASSERT(flag == JUMP_FUNCTION);
    jmp(kScratchRegister);
  }
  bind(&done);
}


void MacroAssembler::InvokeFunction(Register function,
                                    const ParameterCount& actual,
                                    InvokeFlag flag) {
  ASSERT(function.is(rdi));
  movq(rdx, FieldOperand(function, JSFunction::kSharedFunctionInfoOffset));
  movq(rsi, FieldOperand(function, JSFunction::kContextOffset));
  movl(rbx, FieldOperand(rdx, SharedFunctionInfo::kFormalParameterCountOffset));
  movq(rdx, FieldOperand(rdx, SharedFunctionInfo::kCodeOffset));
  // Advances rdx to the end of the Code object header, to the start of
  // the executable code.
  lea(rdx, FieldOperand(rdx, Code::kHeaderSize));

  ParameterCount expected(rbx);
  InvokeCode(rdx, expected, actual, flag);
}


void MacroAssembler::EnterFrame(StackFrame::Type type) {
  push(rbp);
  movq(rbp, rsp);
  push(rsi);  // Context.
  push(Immediate(Smi::FromInt(type)));
  movq(kScratchRegister, CodeObject(), RelocInfo::EMBEDDED_OBJECT);
  push(kScratchRegister);
  if (FLAG_debug_code) {
    movq(kScratchRegister,
         Factory::undefined_value(),
         RelocInfo::EMBEDDED_OBJECT);
    cmpq(Operand(rsp, 0), kScratchRegister);
    Check(not_equal, "code object not properly patched");
  }
}


void MacroAssembler::LeaveFrame(StackFrame::Type type) {
  if (FLAG_debug_code) {
    movq(kScratchRegister, Immediate(Smi::FromInt(type)));
    cmpq(Operand(rbp, StandardFrameConstants::kMarkerOffset), kScratchRegister);
    Check(equal, "stack frame types must match");
  }
  movq(rsp, rbp);
  pop(rbp);
}



void MacroAssembler::EnterExitFrame(StackFrame::Type type) {
  ASSERT(type == StackFrame::EXIT || type == StackFrame::EXIT_DEBUG);

  // Setup the frame structure on the stack.
  ASSERT(ExitFrameConstants::kCallerSPDisplacement == +2 * kPointerSize);
  ASSERT(ExitFrameConstants::kCallerPCOffset == +1 * kPointerSize);
  ASSERT(ExitFrameConstants::kCallerFPOffset ==  0 * kPointerSize);
  push(rbp);
  movq(rbp, rsp);

  // Reserve room for entry stack pointer and push the debug marker.
  ASSERT(ExitFrameConstants::kSPOffset  == -1 * kPointerSize);
  push(Immediate(0));  // saved entry sp, patched before call
  push(Immediate(type == StackFrame::EXIT_DEBUG ? 1 : 0));

  // Save the frame pointer and the context in top.
  ExternalReference c_entry_fp_address(Top::k_c_entry_fp_address);
  ExternalReference context_address(Top::k_context_address);
  movq(rdi, rax);  // Backup rax before we use it.

  movq(rax, rbp);
  store_rax(c_entry_fp_address);
  movq(rax, rsi);
  store_rax(context_address);

  // Setup argv in callee-saved register r15. It is reused in LeaveExitFrame,
  // so it must be retained across the C-call.
  int offset = StandardFrameConstants::kCallerSPOffset - kPointerSize;
  lea(r15, Operand(rbp, rdi, kTimesPointerSize, offset));

#ifdef ENABLE_DEBUGGER_SUPPORT
  // Save the state of all registers to the stack from the memory
  // location. This is needed to allow nested break points.
  if (type == StackFrame::EXIT_DEBUG) {
    // TODO(1243899): This should be symmetric to
    // CopyRegistersFromStackToMemory() but it isn't! esp is assumed
    // correct here, but computed for the other call. Very error
    // prone! FIX THIS.  Actually there are deeper problems with
    // register saving than this asymmetry (see the bug report
    // associated with this issue).
    PushRegistersFromMemory(kJSCallerSaved);
  }
#endif

  // Reserve space for two arguments: argc and argv
  subq(rsp, Immediate(2 * kPointerSize));

  // Get the required frame alignment for the OS.
  static const int kFrameAlignment = OS::ActivationFrameAlignment();
  if (kFrameAlignment > 0) {
    ASSERT(IsPowerOf2(kFrameAlignment));
    movq(kScratchRegister, Immediate(-kFrameAlignment));
    and_(rsp, kScratchRegister);
  }

  // Patch the saved entry sp.
  movq(Operand(rbp, ExitFrameConstants::kSPOffset), rsp);
}


void MacroAssembler::LeaveExitFrame(StackFrame::Type type) {
  // Registers:
  // r15 : argv
#ifdef ENABLE_DEBUGGER_SUPPORT
  // Restore the memory copy of the registers by digging them out from
  // the stack. This is needed to allow nested break points.
  if (type == StackFrame::EXIT_DEBUG) {
    // It's okay to clobber register ebx below because we don't need
    // the function pointer after this.
    const int kCallerSavedSize = kNumJSCallerSaved * kPointerSize;
    int kOffset = ExitFrameConstants::kDebugMarkOffset - kCallerSavedSize;
    lea(rbx, Operand(rbp, kOffset));
    CopyRegistersFromStackToMemory(rbx, rcx, kJSCallerSaved);
  }
#endif

  // Get the return address from the stack and restore the frame pointer.
  movq(rcx, Operand(rbp, 1 * kPointerSize));
  movq(rbp, Operand(rbp, 0 * kPointerSize));

  // Pop the arguments and the receiver from the caller stack.
  lea(rsp, Operand(r15, 1 * kPointerSize));

  // Restore current context from top and clear it in debug mode.
  ExternalReference context_address(Top::k_context_address);
  movq(kScratchRegister, context_address);
  movq(rsi, Operand(kScratchRegister, 0));
#ifdef DEBUG
  movq(Operand(kScratchRegister, 0), Immediate(0));
#endif

  // Push the return address to get ready to return.
  push(rcx);

  // Clear the top frame.
  ExternalReference c_entry_fp_address(Top::k_c_entry_fp_address);
  movq(kScratchRegister, c_entry_fp_address);
  movq(Operand(kScratchRegister, 0), Immediate(0));
}


} }  // namespace v8::internal