// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/compiler/runtime_api.h"
#include "vm/globals.h"

// For `AllocateObjectInstr::WillAllocateNewOrRemembered`
// For `GenericCheckBoundInstr::UseUnboxedRepresentation`
#include "vm/compiler/backend/il.h"

#define SHOULD_NOT_INCLUDE_RUNTIME

#include "vm/compiler/stub_code_compiler.h"

#if defined(TARGET_ARCH_ARM)

#include "vm/class_id.h"
#include "vm/code_entry_kind.h"
#include "vm/compiler/api/type_check_mode.h"
#include "vm/compiler/assembler/assembler.h"
#include "vm/compiler/backend/locations.h"
#include "vm/constants.h"
#include "vm/ffi_callback_metadata.h"
#include "vm/instructions.h"
#include "vm/static_type_exactness_state.h"
#include "vm/tags.h"

#define __ assembler->

namespace dart {
namespace compiler {

// Ensures that [R0] is a new object, if not it will be added to the remembered
// set via a leaf runtime call.
//
// WARNING: This might clobber all registers except for [R0], [THR] and [FP].
// The caller should simply call LeaveStubFrame() and return.
void StubCodeCompiler::EnsureIsNewOrRemembered() {
  // If the object is not in an active TLAB, we call a leaf-runtime to add it to
  // the remembered set and/or deferred marking worklist. This test assumes a
  // Page's TLAB use is always ascending.
  Label done;
  __ AndImmediate(TMP, R0, target::kPageMask);
  __ LoadFromOffset(TMP, TMP, target::Page::original_top_offset());
  __ CompareRegisters(R0, TMP);
  __ BranchIf(UNSIGNED_GREATER_EQUAL, &done);

  {
    LeafRuntimeScope rt(assembler,
                        /*frame_size=*/0,
                        /*preserve_registers=*/false);
    // [R0] already contains first argument.
    __ mov(R1, Operand(THR));
    rt.Call(kEnsureRememberedAndMarkingDeferredRuntimeEntry, 2);
  }

  __ Bind(&done);
}

// Input parameters:
//   LR : return address.
//   SP : address of last argument in argument array.
//   SP + 4*R4 - 4 : address of first argument in argument array.
//   SP + 4*R4 : address of return value.
//   R9 : address of the runtime function to call.
//   R4 : number of arguments to the call.
void StubCodeCompiler::GenerateCallToRuntimeStub() {
  const intptr_t thread_offset = target::NativeArguments::thread_offset();
  const intptr_t argc_tag_offset = target::NativeArguments::argc_tag_offset();
  const intptr_t argv_offset = target::NativeArguments::argv_offset();
  const intptr_t retval_offset = target::NativeArguments::retval_offset();

  __ ldr(CODE_REG, Address(THR, target::Thread::call_to_runtime_stub_offset()));
  __ EnterStubFrame();

  // Save exit frame information to enable stack walking as we are about
  // to transition to Dart VM C++ code.
  __ StoreToOffset(FP, THR, target::Thread::top_exit_frame_info_offset());

  // Mark that the thread exited generated code through a runtime call.
  __ LoadImmediate(R8, target::Thread::exit_through_runtime_call());
  __ StoreToOffset(R8, THR, target::Thread::exit_through_ffi_offset());

#if defined(DEBUG)
  {
    Label ok;
    // Check that we are always entering from Dart code.
    __ LoadFromOffset(R8, THR, target::Thread::vm_tag_offset());
    __ CompareImmediate(R8, VMTag::kDartTagId);
    __ b(&ok, EQ);
    __ Stop("Not coming from Dart code.");
    __ Bind(&ok);
  }
#endif

  // Mark that the thread is executing VM code.
  __ StoreToOffset(R9, THR, target::Thread::vm_tag_offset());

  // Reserve space for arguments and align frame before entering C++ world.
  // target::NativeArguments are passed in registers.
  ASSERT(target::NativeArguments::StructSize() == 4 * target::kWordSize);
  __ ReserveAlignedFrameSpace(0);

  // Pass target::NativeArguments structure by value and call runtime.
  // Registers R0, R1, R2, and R3 are used.

  ASSERT(thread_offset == 0 * target::kWordSize);
  // Set thread in NativeArgs.
  __ mov(R0, Operand(THR));

  ASSERT(argc_tag_offset == 1 * target::kWordSize);
  __ mov(R1, Operand(R4));  // Set argc in target::NativeArguments.

  ASSERT(argv_offset == 2 * target::kWordSize);
  __ add(R2, FP, Operand(R4, LSL, 2));  // Compute argv.
  // Set argv in target::NativeArguments.
  __ AddImmediate(R2,
                  target::frame_layout.param_end_from_fp * target::kWordSize);

  ASSERT(retval_offset == 3 * target::kWordSize);
  __ add(R3, R2,
         Operand(target::kWordSize));  // Retval is next to 1st argument.

  // Call runtime or redirection via simulator.
  __ blx(R9);

  // Mark that the thread is executing Dart code.
  __ LoadImmediate(R2, VMTag::kDartTagId);
  __ StoreToOffset(R2, THR, target::Thread::vm_tag_offset());

  // Mark that the thread has not exited generated Dart code.
  __ LoadImmediate(R2, 0);
  __ StoreToOffset(R2, THR, target::Thread::exit_through_ffi_offset());

  // Reset exit frame information in Isolate's mutator thread structure.
  __ StoreToOffset(R2, THR, target::Thread::top_exit_frame_info_offset());

  // Restore the global object pool after returning from runtime (old space is
  // moving, so the GOP could have been relocated).
  if (FLAG_precompiled_mode) {
    __ SetupGlobalPoolAndDispatchTable();
  }

  __ LeaveStubFrame();

  // The following return can jump to a lazy-deopt stub, which assumes R0
  // contains a return value and will save it in a GC-visible way.  We therefore
  // have to ensure R0 does not contain any garbage value left from the C
  // function we called (which has return type "void").
  // (See GenerateDeoptimizationSequence::saved_result_slot_from_fp.)
  __ LoadImmediate(R0, 0);
  __ Ret();
}

void StubCodeCompiler::GenerateSharedStubGeneric(
    bool save_fpu_registers,
    intptr_t self_code_stub_offset_from_thread,
    bool allow_return,
    std::function<void()> perform_runtime_call) {
  // We want the saved registers to appear like part of the caller's frame, so
  // we push them before calling EnterStubFrame.
  RegisterSet all_registers;
  all_registers.AddAllNonReservedRegisters(save_fpu_registers);

  // To make the stack map calculation architecture independent we do the same
  // as on intel.
  READS_RETURN_ADDRESS_FROM_LR(__ Push(LR));
  __ PushRegisters(all_registers);
  __ ldr(CODE_REG, Address(THR, self_code_stub_offset_from_thread));
  __ EnterStubFrame();
  perform_runtime_call();
  if (!allow_return) {
    __ Breakpoint();
    return;
  }
  __ LeaveStubFrame();
  __ PopRegisters(all_registers);
  __ Drop(1);  // We use the LR restored via LeaveStubFrame.
  READS_RETURN_ADDRESS_FROM_LR(__ bx(LR));
}

void StubCodeCompiler::GenerateSharedStub(
    bool save_fpu_registers,
    const RuntimeEntry* target,
    intptr_t self_code_stub_offset_from_thread,
    bool allow_return,
    bool store_runtime_result_in_result_register) {
  ASSERT(!store_runtime_result_in_result_register || allow_return);
  auto perform_runtime_call = [&]() {
    if (store_runtime_result_in_result_register) {
      // Reserve space for the result on the stack. This needs to be a GC
      // safe value.
      __ PushImmediate(Smi::RawValue(0));
    }
    __ CallRuntime(*target, /*argument_count=*/0);
    if (store_runtime_result_in_result_register) {
      __ PopRegister(R0);
      __ str(R0,
             Address(FP, target::kWordSize *
                             StubCodeCompiler::WordOffsetFromFpToCpuRegister(
                                 SharedSlowPathStubABI::kResultReg)));
    }
  };
  GenerateSharedStubGeneric(save_fpu_registers,
                            self_code_stub_offset_from_thread, allow_return,
                            perform_runtime_call);
}

void StubCodeCompiler::GenerateEnterSafepointStub() {
  RegisterSet all_registers;
  all_registers.AddAllGeneralRegisters();
  __ PushRegisters(all_registers);

  SPILLS_LR_TO_FRAME(__ EnterFrame((1 << FP) | (1 << LR), 0));
  __ ReserveAlignedFrameSpace(0);
  __ ldr(R0, Address(THR, kEnterSafepointRuntimeEntry.OffsetFromThread()));
  __ blx(R0);
  RESTORES_LR_FROM_FRAME(__ LeaveFrame((1 << FP) | (1 << LR), 0));

  __ PopRegisters(all_registers);
  __ Ret();
}

void StubCodeCompiler::GenerateExitSafepointStub() {
  RegisterSet all_registers;
  all_registers.AddAllGeneralRegisters();
  __ PushRegisters(all_registers);

  SPILLS_LR_TO_FRAME(__ EnterFrame((1 << FP) | (1 << LR), 0));
  __ ReserveAlignedFrameSpace(0);

  __ VerifyNotInGenerated(R0);

  __ ldr(R0, Address(THR, kExitSafepointRuntimeEntry.OffsetFromThread()));
  __ blx(R0);
  RESTORES_LR_FROM_FRAME(__ LeaveFrame((1 << FP) | (1 << LR), 0));

  __ PopRegisters(all_registers);
  __ Ret();
}

// Call a native function within a safepoint.
//
// On entry:
//   Stack: set up for call, incl. alignment
//   R8: target to call
//
// On exit:
//   Stack: preserved
//   NOTFP, R4: clobbered, although normally callee-saved
void StubCodeCompiler::GenerateCallNativeThroughSafepointStub() {
  COMPILE_ASSERT(IsAbiPreservedRegister(R4));

  // TransitionGeneratedToNative might clobber LR if it takes the slow path.
  SPILLS_RETURN_ADDRESS_FROM_LR_TO_REGISTER(__ mov(R4, Operand(LR)));

  __ LoadImmediate(R9, target::Thread::exit_through_ffi());
  __ TransitionGeneratedToNative(R8, FPREG, R9 /*volatile*/, NOTFP,
                                 /*enter_safepoint=*/true);

  __ blx(R8);

  __ TransitionNativeToGenerated(R9 /*volatile*/, NOTFP,
                                 /*exit_safepoint=*/true);

  __ bx(R4);
}

void StubCodeCompiler::GenerateLoadBSSEntry(BSS::Relocation relocation,
                                            Register dst,
                                            Register tmp) {
  compiler::Label skip_reloc;
  __ b(&skip_reloc);
  InsertBSSRelocation(relocation);
  __ Bind(&skip_reloc);

  // For historical reasons, the PC on ARM points 8 bytes (two instructions)
  // past the current instruction.
  __ sub(tmp, PC,
         compiler::Operand(Instr::kPCReadOffset + compiler::target::kWordSize));

  // tmp holds the address of the relocation.
  __ ldr(dst, compiler::Address(tmp));

  // dst holds the relocation itself: tmp - bss_start.
  // tmp = tmp + (bss_start - tmp) = bss_start
  __ add(tmp, tmp, compiler::Operand(dst));

  // tmp holds the start of the BSS section.
  // Load the "get-thread" routine: *bss_start.
  __ ldr(dst, compiler::Address(tmp));
}

void StubCodeCompiler::GenerateLoadFfiCallbackMetadataRuntimeFunction(
    uword function_index,
    Register dst) {
  // Keep in sync with FfiCallbackMetadata::EnsureFirstTrampolinePageLocked.
  // Note: If the stub was aligned, this could be a single PC relative load.

  // Load a pointer to the beginning of the stub into dst.
  const intptr_t code_size = __ CodeSize();
  __ SubImmediate(dst, PC, Instr::kPCReadOffset + code_size);

  // Round dst down to the page size.
  __ AndImmediate(dst, dst, FfiCallbackMetadata::kPageMask);

  // Load the function from the function table.
  __ LoadFromOffset(dst, dst,
                    FfiCallbackMetadata::RuntimeFunctionOffset(function_index));
}

void StubCodeCompiler::GenerateFfiCallbackTrampolineStub() {
#if defined(DART_INCLUDE_SIMULATOR) && !defined(DART_PRECOMPILER)
  // TODO(37299): FFI is not supported in SIMARM.
  __ Breakpoint();
#else
  Label body;

  // TMP is volatile and not used for passing any arguments.
  COMPILE_ASSERT(!IsCalleeSavedRegister(TMP) && !IsArgumentRegister(TMP));
  for (intptr_t i = 0; i < FfiCallbackMetadata::NumCallbackTrampolinesPerPage();
       ++i) {
    // The FfiCallbackMetadata table is keyed by the trampoline entry point. So
    // look up the current PC, then jump to the shared section. The PC is offset
    // by Instr::kPCReadOffset, which is subtracted below.
    __ mov(TMP, Operand(PC));
    __ b(&body);
  }

  ASSERT(__ CodeSize() ==
         FfiCallbackMetadata::kNativeCallbackTrampolineSize *
             FfiCallbackMetadata::NumCallbackTrampolinesPerPage());

  __ Bind(&body);

  const intptr_t shared_stub_start = __ CodeSize();

  // Save THR (callee-saved), R4 & R5 (temporaries, callee-saved), and LR.
  COMPILE_ASSERT(FfiCallbackMetadata::kNativeCallbackTrampolineStackDelta == 4);
  SPILLS_LR_TO_FRAME(
      __ PushList((1 << LR) | (1 << THR) | (1 << R4) | (1 << R5)));

  // The PC is in TMP, but is offset by kPCReadOffset. To get the actual
  // trampoline entry point we need to subtract that.
  __ sub(R4, TMP, Operand(Instr::kPCReadOffset));

  COMPILE_ASSERT(IsCalleeSavedRegister(R4));
  COMPILE_ASSERT(!IsArgumentRegister(THR));

  RegisterSet argument_registers;
  argument_registers.AddAllArgumentRegisters();
  __ PushRegisters(argument_registers);

  // Load the thread, verify the callback ID and exit the safepoint.
  //
  // We exit the safepoint inside DLRT_GetFfiCallbackMetadata in order to save
  // code size on this shared stub.
  {
    __ mov(R0, Operand(R4));

    // We also need to look up the entry point for the trampoline. This is
    // returned using a pointer passed to the second arg of the C function
    // below. We aim that pointer at a reserved stack slot.
    __ sub(SP, SP, Operand(compiler::target::kWordSize));
    __ mov(R1, Operand(SP));

    // We also need to know if this is a sync or async callback. This is also
    // returned by pointer.
    __ sub(SP, SP, Operand(compiler::target::kWordSize));
    __ mov(R2, Operand(SP));

    __ EnterFrame(1 << FP, 0);
    __ ReserveAlignedFrameSpace(0);

    GenerateLoadFfiCallbackMetadataRuntimeFunction(
        FfiCallbackMetadata::kGetFfiCallbackMetadata, R4);

    __ blx(R4);
    __ mov(THR, Operand(R0));

    __ LeaveFrame(1 << FP);

    // The trampoline type is at the top of the stack. Pop it into R4.
    __ Pop(R4);

    // Entry point is now at the top of the stack. Pop it into R5.
    __ Pop(R5);
  }

  __ PopRegisters(argument_registers);

  Label async_callback;
  Label sync_isolate_group_shared_callback;
  Label done;

  // If GetFfiCallbackMetadata returned a null thread, it means that the async
  // callback was invoked after it was deleted. In this case, do nothing.
  __ cmp(THR, Operand(0));
  __ b(&done, EQ);

  // Check the trampoline type to see how the callback should be invoked.
  __ cmp(
      R4,
      Operand(static_cast<uword>(FfiCallbackMetadata::TrampolineType::kAsync)));
  __ b(&async_callback, EQ);

  __ cmp(R4,
         Operand(static_cast<uword>(
             FfiCallbackMetadata::TrampolineType::kSyncIsolateGroupShared)));
  __ b(&sync_isolate_group_shared_callback, EQ);

  // Sync callback. The entry point contains the target function, so just call
  // it. DLRT_GetThreadForNativeCallbackTrampoline exited the safepoint, so
  // re-enter it afterwards.

  // On entry to the function, there will be four extra slots on the stack:
  // saved THR, R4, R5 and the return address. The target will know to skip
  // them.
  __ blx(R5);

  // Clobbers R4, R5 and TMP, all saved or volatile.
  __ EnterFullSafepoint(R4, R5);

  __ b(&done);

  __ Bind(&sync_isolate_group_shared_callback);

  __ blx(R5);

  // Exit isolate group shared isolate.
  {
    __ EnterFrame(1 << FP, 0);
    __ ReserveAlignedFrameSpace(0);

    const RegisterSet return_registers(
        (1 << CallingConventions::kReturnReg) |
            (1 << CallingConventions::kSecondReturnReg),
        1 << CallingConventions::kReturnFpuReg);
    __ PushRegisters(return_registers);

    GenerateLoadFfiCallbackMetadataRuntimeFunction(
        FfiCallbackMetadata::kExitIsolateGroupSharedIsolate, R4);

    __ blx(R4);

    __ PopRegisters(return_registers);
    __ LeaveFrame(1 << FP);
  }

  __ b(&done);

  __ Bind(&async_callback);

  // Async callback. The entrypoint marshals the arguments into a message and
  // sends it over the send port. DLRT_GetThreadForNativeCallbackTrampoline
  // entered a temporary isolate, so exit it afterwards.

  // On entry to the function, there will be four extra slots on the stack:
  // saved THR, R4, R5 and the return address. The target will know to skip
  // them.
  __ blx(R5);

  // Exit the temporary isolate.
  {
    GenerateLoadFfiCallbackMetadataRuntimeFunction(
        FfiCallbackMetadata::kExitTemporaryIsolate, R0);

    CLOBBERS_LR(__ PopList((1 << LR) | (1 << THR) | (1 << R4) | (1 << R5)));

    // Tail-call DLRT_ExitTemporaryIsolate. It is not safe to return to this
    // stub, since it might be deleted once DLRT_ExitTemporaryIsolate proceeds
    // enough for VM shutdown.
    __ bx(R0);
    __ Breakpoint();
  }

  __ Bind(&done);

  // Returns.
  __ PopList((1 << PC) | (1 << THR) | (1 << R4) | (1 << R5));

  ASSERT_LESS_OR_EQUAL(__ CodeSize() - shared_stub_start,
                       FfiCallbackMetadata::kNativeCallbackSharedStubSize);
  ASSERT_LESS_OR_EQUAL(__ CodeSize(), FfiCallbackMetadata::kPageSize);

#if defined(DEBUG)
  while (__ CodeSize() < FfiCallbackMetadata::kPageSize) {
    __ Breakpoint();
  }
#endif
#endif
}

void StubCodeCompiler::GenerateDispatchTableNullErrorStub() {
  __ EnterStubFrame();
  __ SmiTag(DispatchTableNullErrorABI::kClassIdReg);
  __ PushRegister(DispatchTableNullErrorABI::kClassIdReg);
  __ CallRuntime(kDispatchTableNullErrorRuntimeEntry, /*argument_count=*/1);
  // The NullError runtime entry does not return.
  __ Breakpoint();
}

void StubCodeCompiler::GenerateRangeError(bool with_fpu_regs) {
  auto perform_runtime_call = [&]() {
    ASSERT(!GenericCheckBoundInstr::UseUnboxedRepresentation());
    __ PushRegistersInOrder(
        {RangeErrorABI::kLengthReg, RangeErrorABI::kIndexReg});
    __ CallRuntime(kRangeErrorRuntimeEntry, /*argument_count=*/2);
    __ Breakpoint();
  };

  GenerateSharedStubGeneric(
      /*save_fpu_registers=*/with_fpu_regs,
      with_fpu_regs
          ? target::Thread::range_error_shared_with_fpu_regs_stub_offset()
          : target::Thread::range_error_shared_without_fpu_regs_stub_offset(),
      /*allow_return=*/false, perform_runtime_call);
}

void StubCodeCompiler::GenerateWriteError(bool with_fpu_regs) {
  auto perform_runtime_call = [&]() {
    __ CallRuntime(kWriteErrorRuntimeEntry, /*argument_count=*/2);
    __ Breakpoint();
  };

  GenerateSharedStubGeneric(
      /*save_fpu_registers=*/with_fpu_regs,
      with_fpu_regs
          ? target::Thread::write_error_shared_with_fpu_regs_stub_offset()
          : target::Thread::write_error_shared_without_fpu_regs_stub_offset(),
      /*allow_return=*/false, perform_runtime_call);
}

// Input parameters:
//   LR : return address.
//   SP : address of return value.
//   R9 : address of the native function to call.
//   R2 : address of first argument in argument array.
//   R1 : argc_tag including number of arguments and function kind.
static void GenerateCallNativeWithWrapperStub(Assembler* assembler,
                                              Address wrapper) {
  const intptr_t thread_offset = target::NativeArguments::thread_offset();
  const intptr_t argc_tag_offset = target::NativeArguments::argc_tag_offset();
  const intptr_t argv_offset = target::NativeArguments::argv_offset();
  const intptr_t retval_offset = target::NativeArguments::retval_offset();

  __ EnterStubFrame();

  // Save exit frame information to enable stack walking as we are about
  // to transition to native code.
  __ StoreToOffset(FP, THR, target::Thread::top_exit_frame_info_offset());

  // Mark that the thread exited generated code through a runtime call.
  __ LoadImmediate(R8, target::Thread::exit_through_runtime_call());
  __ StoreToOffset(R8, THR, target::Thread::exit_through_ffi_offset());

#if defined(DEBUG)
  {
    Label ok;
    // Check that we are always entering from Dart code.
    __ LoadFromOffset(R8, THR, target::Thread::vm_tag_offset());
    __ CompareImmediate(R8, VMTag::kDartTagId);
    __ b(&ok, EQ);
    __ Stop("Not coming from Dart code.");
    __ Bind(&ok);
  }
#endif

  // Mark that the thread is executing native code.
  __ StoreToOffset(R9, THR, target::Thread::vm_tag_offset());

  // Reserve space for the native arguments structure passed on the stack (the
  // outgoing pointer parameter to the native arguments structure is passed in
  // R0) and align frame before entering the C++ world.
  __ ReserveAlignedFrameSpace(target::NativeArguments::StructSize());

  // Initialize target::NativeArguments structure and call native function.
  // Registers R0, R1, R2, and R3 are used.

  ASSERT(thread_offset == 0 * target::kWordSize);
  // Set thread in NativeArgs.
  __ mov(R0, Operand(THR));

  ASSERT(argc_tag_offset == 1 * target::kWordSize);
  // Set argc in target::NativeArguments: R1 already contains argc.

  ASSERT(argv_offset == 2 * target::kWordSize);
  // Set argv in target::NativeArguments: R2 already contains argv.

  // Set retval in NativeArgs.
  ASSERT(retval_offset == 3 * target::kWordSize);
  __ add(R3, FP,
         Operand((target::frame_layout.param_end_from_fp + 1) *
                 target::kWordSize));

  // Passing the structure by value as in runtime calls would require changing
  // Dart API for native functions.
  // For now, space is reserved on the stack and we pass a pointer to it.
  __ stm(IA, SP, (1 << R0) | (1 << R1) | (1 << R2) | (1 << R3));
  __ mov(R0, Operand(SP));  // Pass the pointer to the target::NativeArguments.

  __ mov(R1, Operand(R9));  // Pass the function entrypoint to call.

  // Call native function invocation wrapper or redirection via simulator.
  __ Call(wrapper);

  // Mark that the thread is executing Dart code.
  __ LoadImmediate(R2, VMTag::kDartTagId);
  __ StoreToOffset(R2, THR, target::Thread::vm_tag_offset());

  // Mark that the thread has not exited generated Dart code.
  __ LoadImmediate(R2, 0);
  __ StoreToOffset(R2, THR, target::Thread::exit_through_ffi_offset());

  // Reset exit frame information in Isolate's mutator thread structure.
  __ StoreToOffset(R2, THR, target::Thread::top_exit_frame_info_offset());

  // Restore the global object pool after returning from runtime (old space is
  // moving, so the GOP could have been relocated).
  if (FLAG_precompiled_mode) {
    __ SetupGlobalPoolAndDispatchTable();
  }

  __ LeaveStubFrame();
  __ Ret();
}

void StubCodeCompiler::GenerateCallNoScopeNativeStub() {
  GenerateCallNativeWithWrapperStub(
      assembler,
      Address(THR,
              target::Thread::no_scope_native_wrapper_entry_point_offset()));
}

void StubCodeCompiler::GenerateCallAutoScopeNativeStub() {
  GenerateCallNativeWithWrapperStub(
      assembler,
      Address(THR,
              target::Thread::auto_scope_native_wrapper_entry_point_offset()));
}

// Input parameters:
//   LR : return address.
//   SP : address of return value.
//   R9 : address of the native function to call.
//   R2 : address of first argument in argument array.
//   R1 : argc_tag including number of arguments and function kind.
void StubCodeCompiler::GenerateCallBootstrapNativeStub() {
  GenerateCallNativeWithWrapperStub(
      assembler,
      Address(THR,
              target::Thread::bootstrap_native_wrapper_entry_point_offset()));
}

// Input parameters:
//   ARGS_DESC_REG: arguments descriptor array.
void StubCodeCompiler::GenerateCallStaticFunctionStub() {
  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  // Setup space on stack for return value and preserve arguments descriptor.
  __ LoadImmediate(R0, 0);
  __ PushList((1 << R0) | (1 << ARGS_DESC_REG));
  __ CallRuntime(kPatchStaticCallRuntimeEntry, 0);
  // Get Code object result and restore arguments descriptor array.
  __ PopList((1 << R0) | (1 << ARGS_DESC_REG));
  // Remove the stub frame.
  __ LeaveStubFrame();
  // Jump to the dart function.
  __ mov(CODE_REG, Operand(R0));
  __ Branch(FieldAddress(R0, target::Code::entry_point_offset()));
}

// Called from a static call only when an invalid code has been entered
// (invalid because its function was optimized or deoptimized).
// ARGS_DESC_REG: arguments descriptor array.
void StubCodeCompiler::GenerateFixCallersTargetStub() {
  Label monomorphic;
  __ BranchOnMonomorphicCheckedEntryJIT(&monomorphic);

  // Load code pointer to this stub from the thread:
  // The one that is passed in, is not correct - it points to the code object
  // that needs to be replaced.
  __ ldr(CODE_REG,
         Address(THR, target::Thread::fix_callers_target_code_offset()));
  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  // Setup space on stack for return value and preserve arguments descriptor.
  __ LoadImmediate(R0, 0);
  __ PushList((1 << R0) | (1 << ARGS_DESC_REG));
  __ CallRuntime(kFixCallersTargetRuntimeEntry, 0);
  // Get Code object result and restore arguments descriptor array.
  __ PopList((1 << R0) | (1 << ARGS_DESC_REG));
  // Remove the stub frame.
  __ LeaveStubFrame();
  // Jump to the dart function.
  __ mov(CODE_REG, Operand(R0));
  __ Branch(FieldAddress(R0, target::Code::entry_point_offset()));

  __ Bind(&monomorphic);
  // Load code pointer to this stub from the thread:
  // The one that is passed in, is not correct - it points to the code object
  // that needs to be replaced.
  __ ldr(CODE_REG,
         Address(THR, target::Thread::fix_callers_target_code_offset()));
  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  __ LoadImmediate(R1, 0);
  __ Push(R1);  // Result slot.
  __ Push(R0);  // Preserve receiver.
  __ Push(R9);  // Old cache value (also 2nd return value).
  __ CallRuntime(kFixCallersTargetMonomorphicRuntimeEntry, 2);
  __ Pop(R9);        // Get target cache object.
  __ Pop(R0);        // Restore receiver.
  __ Pop(CODE_REG);  // Get target Code object.
  // Remove the stub frame.
  __ LeaveStubFrame();
  // Jump to the dart function.
  __ Branch(FieldAddress(
      CODE_REG, target::Code::entry_point_offset(CodeEntryKind::kMonomorphic)));
}

// Called from object allocate instruction when the allocation stub has been
// disabled.
void StubCodeCompiler::GenerateFixAllocationStubTargetStub() {
  // Load code pointer to this stub from the thread:
  // The one that is passed in, is not correct - it points to the code object
  // that needs to be replaced.
  __ ldr(CODE_REG,
         Address(THR, target::Thread::fix_allocation_stub_code_offset()));
  __ EnterStubFrame();
  // Setup space on stack for return value.
  __ LoadImmediate(R0, 0);
  __ Push(R0);
  __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
  // Get Code object result.
  __ Pop(R0);
  // Remove the stub frame.
  __ LeaveStubFrame();
  // Jump to the dart function.
  __ mov(CODE_REG, Operand(R0));
  __ Branch(FieldAddress(R0, target::Code::entry_point_offset()));
}

// Called from object allocate instruction when the allocation stub for a
// generic class has been disabled.
void StubCodeCompiler::GenerateFixParameterizedAllocationStubTargetStub() {
  // Load code pointer to this stub from the thread:
  // The one that is passed in, is not correct - it points to the code object
  // that needs to be replaced.
  __ ldr(CODE_REG,
         Address(THR, target::Thread::fix_allocation_stub_code_offset()));
  __ EnterStubFrame();
  // Preserve type arguments register.
  __ Push(AllocateObjectABI::kTypeArgumentsReg);
  // Setup space on stack for return value.
  __ LoadImmediate(R0, 0);
  __ Push(R0);
  __ CallRuntime(kFixAllocationStubTargetRuntimeEntry, 0);
  // Get Code object result.
  __ Pop(R0);
  // Restore type arguments register.
  __ Push(AllocateObjectABI::kTypeArgumentsReg);
  // Remove the stub frame.
  __ LeaveStubFrame();
  // Jump to the dart function.
  __ mov(CODE_REG, Operand(R0));
  __ Branch(FieldAddress(R0, target::Code::entry_point_offset()));
}

// Input parameters:
//   R2: smi-tagged argument count, may be zero.
//   FP[target::frame_layout.param_end_from_fp + 1]: last argument.
static void PushArrayOfArguments(Assembler* assembler) {
  // Allocate array to store arguments of caller.
  __ LoadObject(R1, NullObject());
  // R1: null element type for raw Array.
  // R2: smi-tagged argument count, may be zero.
  __ BranchLink(StubCodeAllocateArray());
  // R0: newly allocated array.
  // R2: smi-tagged argument count, may be zero (was preserved by the stub).
  __ Push(R0);  // Array is in R0 and on top of stack.
  __ AddImmediate(R1, FP,
                  target::frame_layout.param_end_from_fp * target::kWordSize);
  __ AddImmediate(R3, R0, target::Array::data_offset() - kHeapObjectTag);
  // Copy arguments from stack to array (starting at the end).
  // R1: address just beyond last argument on stack.
  // R3: address of first argument in array.
  Label enter;
  __ b(&enter);
  Label loop;
  __ Bind(&loop);
  __ ldr(R8, Address(R1, target::kWordSize, Address::PreIndex));
  // Generational barrier is needed, array is not necessarily in new space.
  __ StoreIntoObject(R0, Address(R3, R2, LSL, 1), R8);
  __ Bind(&enter);
  __ subs(R2, R2, Operand(target::ToRawSmi(1)));  // R2 is Smi.
  __ b(&loop, PL);
}

// Used by eager and lazy deoptimization. Preserve result in R0 if necessary.
// This stub translates optimized frame into unoptimized frame. The optimized
// frame can contain values in registers and on stack, the unoptimized
// frame contains all values on stack.
// Deoptimization occurs in following steps:
// - Push all registers that can contain values.
// - Call C routine to copy the stack and saved registers into temporary buffer.
// - Adjust caller's frame to correct unoptimized frame size.
// - Fill the unoptimized frame.
// - Materialize objects that require allocation (e.g. Double instances).
// GC can occur only after frame is fully rewritten.
// Stack after EnterFrame(...) below:
//   +------------------+
//   | Saved PP         | <- TOS
//   +------------------+
//   | Saved FP         | <- FP of stub
//   +------------------+
//   | Saved LR         |  (deoptimization point)
//   +------------------+
//   | pc marker        |
//   +------------------+
//   | Saved CODE_REG   |
//   +------------------+
//   | ...              | <- SP of optimized frame
//
// Parts of the code cannot GC, part of the code can GC.
static void GenerateDeoptimizationSequence(Assembler* assembler,
                                           DeoptStubKind kind) {
  // DeoptimizeCopyFrame expects a Dart frame, i.e. EnterDartFrame(0), but there
  // is no need to set the correct PC marker or load PP, since they get patched.
  __ EnterDartFrame(0);
  __ LoadPoolPointer();

  // The code in this frame may not cause GC. kDeoptimizeCopyFrameRuntimeEntry
  // and kDeoptimizeFillFrameRuntimeEntry are leaf runtime calls.
  const intptr_t saved_result_slot_from_fp =
      target::frame_layout.first_local_from_fp + 1 -
      (kNumberOfCpuRegisters - R0);
  const intptr_t saved_exception_slot_from_fp =
      target::frame_layout.first_local_from_fp + 1 -
      (kNumberOfCpuRegisters - R0);
  const intptr_t saved_stacktrace_slot_from_fp =
      target::frame_layout.first_local_from_fp + 1 -
      (kNumberOfCpuRegisters - R1);
  // Result in R0 is preserved as part of pushing all registers below.

  // Push registers in their enumeration order: lowest register number at
  // lowest address.
  for (intptr_t i = kNumberOfCpuRegisters - 1; i >= 0; --i) {
    if (i == CODE_REG) {
      // Save the original value of CODE_REG pushed before invoking this stub
      // instead of the value used to call this stub.
      __ ldr(IP, Address(FP, 2 * target::kWordSize));
      __ Push(IP);
    } else if (i == SP) {
      // Push(SP) has unpredictable behavior.
      __ mov(IP, Operand(SP));
      __ Push(IP);
    } else {
      __ Push(static_cast<Register>(i));
    }
  }

  ASSERT(kFpuRegisterSize == 4 * target::kWordSize);
  if (kNumberOfDRegisters > 16) {
    __ vstmd(DB_W, SP, D16, kNumberOfDRegisters - 16);
    __ vstmd(DB_W, SP, D0, 16);
  } else {
    __ vstmd(DB_W, SP, D0, kNumberOfDRegisters);
  }

  {
    __ mov(R0, Operand(SP));  // Pass address of saved registers block.
    LeafRuntimeScope rt(assembler,
                        /*frame_size=*/0,
                        /*preserve_registers=*/false);
    bool is_lazy =
        (kind == kLazyDeoptFromReturn) || (kind == kLazyDeoptFromThrow);
    __ mov(R1, Operand(is_lazy ? 1 : 0));
    rt.Call(kDeoptimizeCopyFrameRuntimeEntry, 2);
    // Result (R0) is stack-size (FP - SP) in bytes.
  }

  if (kind == kLazyDeoptFromReturn) {
    // Restore result into R1 temporarily.
    __ ldr(R1, Address(FP, saved_result_slot_from_fp * target::kWordSize));
  } else if (kind == kLazyDeoptFromThrow) {
    // Restore result into R1 temporarily.
    __ ldr(R1, Address(FP, saved_exception_slot_from_fp * target::kWordSize));
    __ ldr(R2, Address(FP, saved_stacktrace_slot_from_fp * target::kWordSize));
  }

  __ RestoreCodePointer();
  __ LeaveDartFrame();
  __ sub(SP, FP, Operand(R0));

  // DeoptimizeFillFrame expects a Dart frame, i.e. EnterDartFrame(0), but there
  // is no need to set the correct PC marker or load PP, since they get patched.
  __ EnterStubFrame();
  if (kind == kLazyDeoptFromReturn) {
    __ Push(R1);  // Preserve result as first local.
  } else if (kind == kLazyDeoptFromThrow) {
    __ Push(R1);  // Preserve exception as first local.
    __ Push(R2);  // Preserve stacktrace as second local.
  }
  {
    __ mov(R0, Operand(FP));  // Get last FP address.
    LeafRuntimeScope rt(assembler,
                        /*frame_size=*/0,
                        /*preserve_registers=*/false);
    rt.Call(kDeoptimizeFillFrameRuntimeEntry, 1);
  }
  if (kind == kLazyDeoptFromReturn) {
    // Restore result into R1.
    __ ldr(R1, Address(FP, target::frame_layout.first_local_from_fp *
                               target::kWordSize));
  } else if (kind == kLazyDeoptFromThrow) {
    // Restore result into R1.
    __ ldr(R1, Address(FP, target::frame_layout.first_local_from_fp *
                               target::kWordSize));
    __ ldr(R2, Address(FP, (target::frame_layout.first_local_from_fp - 1) *
                               target::kWordSize));
  }
  // Code above cannot cause GC.
  __ RestoreCodePointer();
  __ LeaveStubFrame();

  // Frame is fully rewritten at this point and it is safe to perform a GC.
  // Materialize any objects that were deferred by FillFrame because they
  // require allocation.
  // Enter stub frame with loading PP. The caller's PP is not materialized yet.
  __ EnterStubFrame();
  if (kind == kLazyDeoptFromReturn) {
    __ Push(R1);  // Preserve result, it will be GC-d here.
  } else if (kind == kLazyDeoptFromThrow) {
    // Preserve CODE_REG for one more runtime call.
    __ Push(CODE_REG);
    __ Push(R1);  // Preserve exception, it will be GC-d here.
    __ Push(R2);  // Preserve stacktrace, it will be GC-d here.
  }
  __ PushObject(NullObject());  // Space for the result.
  __ CallRuntime(kDeoptimizeMaterializeRuntimeEntry, 0);
  // Result tells stub how many bytes to remove from the expression stack
  // of the bottom-most frame. They were used as materialization arguments.
  __ Pop(R2);
  if (kind == kLazyDeoptFromReturn) {
    __ Pop(R0);  // Restore result.
  } else if (kind == kLazyDeoptFromThrow) {
    __ Pop(R1);  // Restore stacktrace.
    __ Pop(R0);  // Restore exception.
    __ Pop(CODE_REG);
  }
  __ LeaveStubFrame();
  // Remove materialization arguments.
  __ add(SP, SP, Operand(R2, ASR, kSmiTagSize));
  // The caller is responsible for emitting the return instruction.

  if (kind == kLazyDeoptFromThrow) {
    // Unoptimized frame is now ready to accept the exception. Rethrow it to
    // find the right handler. Ask rethrow machinery to bypass debugger it
    // was already notified about this exception.
    __ EnterStubFrame();
    __ PushImmediate(
        target::ToRawSmi(0));  // Space for the return value (unused).
    __ Push(R0);               // Exception
    __ Push(R1);               // Stacktrace
    __ PushImmediate(target::ToRawSmi(1));  // Bypass debugger
    __ CallRuntime(kReThrowRuntimeEntry, 3);
    __ LeaveStubFrame();
  }
}

// R0: result, must be preserved
void StubCodeCompiler::GenerateDeoptimizeLazyFromReturnStub() {
  // Push zap value instead of CODE_REG for lazy deopt.
  __ LoadImmediate(IP, kZapCodeReg);
  __ Push(IP);
  // Return address for "call" to deopt stub.
  WRITES_RETURN_ADDRESS_TO_LR(__ LoadImmediate(LR, kZapReturnAddress));
  __ ldr(CODE_REG,
         Address(THR, target::Thread::lazy_deopt_from_return_stub_offset()));
  GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
  __ Ret();
}

// R0: exception, must be preserved
// R1: stacktrace, must be preserved
void StubCodeCompiler::GenerateDeoptimizeLazyFromThrowStub() {
  // Push zap value instead of CODE_REG for lazy deopt.
  __ LoadImmediate(IP, kZapCodeReg);
  __ Push(IP);
  // Return address for "call" to deopt stub.
  WRITES_RETURN_ADDRESS_TO_LR(__ LoadImmediate(LR, kZapReturnAddress));
  __ ldr(CODE_REG,
         Address(THR, target::Thread::lazy_deopt_from_throw_stub_offset()));
  GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
  __ Ret();
}

void StubCodeCompiler::GenerateDeoptimizeStub() {
  __ Push(CODE_REG);
  __ ldr(CODE_REG, Address(THR, target::Thread::deoptimize_stub_offset()));
  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
  __ Ret();
}

// IC_DATA_REG: ICData/MegamorphicCache
static void GenerateNoSuchMethodDispatcherBody(Assembler* assembler) {
  __ EnterStubFrame();

  __ ldr(ARGS_DESC_REG,
         FieldAddress(IC_DATA_REG,
                      target::CallSiteData::arguments_descriptor_offset()));

  // Load the receiver.
  __ ldr(R2, FieldAddress(ARGS_DESC_REG,
                          target::ArgumentsDescriptor::size_offset()));
  __ add(IP, FP, Operand(R2, LSL, 1));  // R2 is Smi.
  __ ldr(R8, Address(IP, target::frame_layout.param_end_from_fp *
                             target::kWordSize));
  __ LoadImmediate(IP, 0);
  __ Push(IP);             // Result slot.
  __ Push(R8);             // Receiver.
  __ Push(IC_DATA_REG);    // ICData/MegamorphicCache.
  __ Push(ARGS_DESC_REG);  // Arguments descriptor.

  // Adjust arguments count.
  __ ldr(R3, FieldAddress(ARGS_DESC_REG,
                          target::ArgumentsDescriptor::type_args_len_offset()));
  __ cmp(R3, Operand(0));
  __ AddImmediate(R2, R2, target::ToRawSmi(1),
                  NE);  // Include the type arguments.

  // R2: Smi-tagged arguments array length.
  PushArrayOfArguments(assembler);
  const intptr_t kNumArgs = 4;
  __ CallRuntime(kNoSuchMethodFromCallStubRuntimeEntry, kNumArgs);
  __ Drop(4);
  __ Pop(R0);  // Return value.
  __ LeaveStubFrame();
  __ Ret();
}

static void GenerateDispatcherCode(Assembler* assembler,
                                   Label* call_target_function) {
  __ Comment("NoSuchMethodDispatch");
  // When lazily generated invocation dispatchers are disabled, the
  // miss-handler may return null.
  __ CompareObject(R0, NullObject());
  __ b(call_target_function, NE);

  GenerateNoSuchMethodDispatcherBody(assembler);
}

// Input:
//   ARGS_DESC_REG - arguments descriptor
//   IC_DATA_REG - icdata/megamorphic_cache
void StubCodeCompiler::GenerateNoSuchMethodDispatcherStub() {
  GenerateNoSuchMethodDispatcherBody(assembler);
}

// Called for inline allocation of arrays.
// Input registers (preserved):
//   LR: return address.
//   AllocateArrayABI::kLengthReg: array length as Smi.
//   AllocateArrayABI::kTypeArgumentsReg: type arguments of array.
// Output registers:
//   AllocateArrayABI::kResultReg: newly allocated array.
// Clobbered:
//   R3, R4, R8, R9
void StubCodeCompiler::GenerateAllocateArrayStub() {
  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label slow_case;
    // Compute the size to be allocated, it is based on the array length
    // and is computed as:
    // RoundedAllocationSize(
    //     (array_length * kwordSize) + target::Array::header_size()).
    __ mov(R3, Operand(AllocateArrayABI::kLengthReg));  // Array length.
    // Check that length is a Smi.
    __ tst(R3, Operand(kSmiTagMask));
    __ b(&slow_case, NE);

    // Check length >= 0 && length <= kMaxNewSpaceElements
    const intptr_t max_len =
        target::ToRawSmi(target::Array::kMaxNewSpaceElements);
    __ CompareImmediate(R3, max_len);
    __ b(&slow_case, HI);

    const intptr_t cid = kArrayCid;
    NOT_IN_PRODUCT(__ MaybeTraceAllocation(cid, &slow_case, R4));

    const intptr_t fixed_size_plus_alignment_padding =
        target::Array::header_size() +
        target::ObjectAlignment::kObjectAlignment - 1;
    __ LoadImmediate(R9, fixed_size_plus_alignment_padding);
    __ add(R9, R9, Operand(R3, LSL, 1));  // R3 is a Smi.
    ASSERT(kSmiTagShift == 1);
    __ bic(R9, R9, Operand(target::ObjectAlignment::kObjectAlignment - 1));

    // R9: Allocation size.
    // Potential new object start.
    __ ldr(AllocateArrayABI::kResultReg,
           Address(THR, target::Thread::top_offset()));
    __ adds(R3, AllocateArrayABI::kResultReg,
            Operand(R9));  // Potential next object start.
    __ b(&slow_case, CS);  // Branch if unsigned overflow.

    // Check if the allocation fits into the remaining space.
    // AllocateArrayABI::kResultReg: potential new object start.
    // R3: potential next object start.
    // R9: allocation size.
    __ ldr(TMP, Address(THR, target::Thread::end_offset()));
    __ cmp(R3, Operand(TMP));
    __ b(&slow_case, CS);
    __ CheckAllocationCanary(AllocateArrayABI::kResultReg);

    // Successfully allocated the object(s), now update top to point to
    // next object start and initialize the object.
    __ str(R3, Address(THR, target::Thread::top_offset()));
    __ add(AllocateArrayABI::kResultReg, AllocateArrayABI::kResultReg,
           Operand(kHeapObjectTag));

    // Initialize the tags.
    // AllocateArrayABI::kResultReg: new object start as a tagged pointer.
    // R3: new object end address.
    // R9: allocation size.
    {
      const intptr_t shift = target::UntaggedObject::kTagBitsSizeTagPos -
                             target::ObjectAlignment::kObjectAlignmentLog2;

      __ CompareImmediate(R9, target::UntaggedObject::kSizeTagMaxSizeTag);
      __ mov(R8, Operand(R9, LSL, shift), LS);
      __ mov(R8, Operand(0), HI);

      // Get the class index and insert it into the tags.
      // R8: size and bit tags.
      const uword tags =
          target::MakeTagWordForNewSpaceObject(cid, /*instance_size=*/0);
      __ LoadImmediate(TMP, tags);
      __ orr(R8, R8, Operand(TMP));
      __ InitializeHeader(R8, AllocateArrayABI::kResultReg);
    }

    // AllocateArrayABI::kResultReg: new object start as a tagged pointer.
    // R3: new object end address.
    // Store the type argument field.
    __ StoreIntoObjectNoBarrier(
        AllocateArrayABI::kResultReg,
        FieldAddress(AllocateArrayABI::kResultReg,
                     target::Array::type_arguments_offset()),
        AllocateArrayABI::kTypeArgumentsReg);

    // Set the length field.
    __ StoreIntoObjectNoBarrier(AllocateArrayABI::kResultReg,
                                FieldAddress(AllocateArrayABI::kResultReg,
                                             target::Array::length_offset()),
                                AllocateArrayABI::kLengthReg);

    // Initialize all array elements to raw_null.
    // AllocateArrayABI::kResultReg: new object start as a tagged pointer.
    // R8, R9: null
    // R4: iterator which initially points to the start of the variable
    // data area to be initialized.
    // R3: new object end address.
    // R9: allocation size.

    __ LoadObject(R8, NullObject());
    __ mov(R9, Operand(R8));
    __ AddImmediate(R4, AllocateArrayABI::kResultReg,
                    target::Array::header_size() - kHeapObjectTag);
    __ InitializeFieldsNoBarrier(AllocateArrayABI::kResultReg, R4, R3, R8, R9);
    __ Ret();
    // Unable to allocate the array using the fast inline code, just call
    // into the runtime.
    __ Bind(&slow_case);
  }

  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  __ LoadImmediate(TMP, 0);
  // Setup space on stack for return value.
  // Push array length as Smi and element type.
  __ PushList((1 << AllocateArrayABI::kTypeArgumentsReg) |
              (1 << AllocateArrayABI::kLengthReg) | (1 << IP));
  __ CallRuntime(kAllocateArrayRuntimeEntry, 2);

  // Write-barrier elimination might be enabled for this array (depending on the
  // array length). To be sure we will check if the allocated object is in old
  // space and if so call a leaf runtime to add it to the remembered set.
  __ ldr(AllocateArrayABI::kResultReg, Address(SP, 2 * target::kWordSize));
  EnsureIsNewOrRemembered();

  // Pop arguments; result is popped in IP.
  __ PopList((1 << AllocateArrayABI::kTypeArgumentsReg) |
             (1 << AllocateArrayABI::kLengthReg) | (1 << IP));
  __ mov(AllocateArrayABI::kResultReg, Operand(IP));
  __ LeaveStubFrame();
  __ Ret();
}

// Called for allocation of Mint.
void StubCodeCompiler::GenerateAllocateMintSharedWithFPURegsStub() {
  // For test purpose call allocation stub without inline allocation attempt.
  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label slow_case;
    __ TryAllocate(compiler::MintClass(), &slow_case, Assembler::kNearJump,
                   AllocateMintABI::kResultReg, AllocateMintABI::kTempReg);
    __ Ret();

    __ Bind(&slow_case);
  }
  COMPILE_ASSERT(AllocateMintABI::kResultReg ==
                 SharedSlowPathStubABI::kResultReg);
  GenerateSharedStub(/*save_fpu_registers=*/true, &kAllocateMintRuntimeEntry,
                     target::Thread::allocate_mint_with_fpu_regs_stub_offset(),
                     /*allow_return=*/true,
                     /*store_runtime_result_in_result_register=*/true);
}

// Called for allocation of Mint.
void StubCodeCompiler::GenerateAllocateMintSharedWithoutFPURegsStub() {
  // For test purpose call allocation stub without inline allocation attempt.
  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label slow_case;
    __ TryAllocate(compiler::MintClass(), &slow_case, Assembler::kNearJump,
                   AllocateMintABI::kResultReg, AllocateMintABI::kTempReg);
    __ Ret();

    __ Bind(&slow_case);
  }
  COMPILE_ASSERT(AllocateMintABI::kResultReg ==
                 SharedSlowPathStubABI::kResultReg);
  GenerateSharedStub(
      /*save_fpu_registers=*/false, &kAllocateMintRuntimeEntry,
      target::Thread::allocate_mint_without_fpu_regs_stub_offset(),
      /*allow_return=*/true,
      /*store_runtime_result_in_result_register=*/true);
}

// Called when invoking Dart code from C++ (VM code).
// Input parameters:
//   LR : points to return address.
//   R0 : target code or entry point (in AOT mode).
//   R1 : arguments descriptor array.
//   R2 : arguments array.
//   R3 : current thread.
void StubCodeCompiler::GenerateInvokeDartCodeStub() {
  SPILLS_LR_TO_FRAME(__ EnterFrame((1 << FP) | (1 << LR), 0));

  // Push code object to PC marker slot.
  __ ldr(IP, Address(R3, target::Thread::invoke_dart_code_stub_offset()));
  __ Push(IP);

  __ PushNativeCalleeSavedRegisters();

  // Set up THR, which caches the current thread in Dart code.
  if (THR != R3) {
    __ mov(THR, Operand(R3));
  }

#if defined(USING_SHADOW_CALL_STACK)
#error Unimplemented
#endif

  // Save the current VMTag on the stack.
  __ LoadFromOffset(R9, THR, target::Thread::vm_tag_offset());
  __ Push(R9);

  // Save top resource and top exit frame info. Use R4-6 as temporary registers.
  // StackFrameIterator reads the top exit frame info saved in this frame.
  __ LoadFromOffset(R4, THR, target::Thread::top_resource_offset());
  __ Push(R4);
  __ LoadImmediate(R8, 0);
  __ StoreToOffset(R8, THR, target::Thread::top_resource_offset());

  __ LoadFromOffset(R8, THR, target::Thread::exit_through_ffi_offset());
  __ Push(R8);
  __ LoadImmediate(R8, 0);
  __ StoreToOffset(R8, THR, target::Thread::exit_through_ffi_offset());

  __ LoadFromOffset(R9, THR, target::Thread::top_exit_frame_info_offset());
  __ StoreToOffset(R8, THR, target::Thread::top_exit_frame_info_offset());

  // target::frame_layout.exit_link_slot_from_entry_fp must be kept in sync
  // with the code below.
#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
  ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -27);
#else
  ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -28);
#endif
  __ Push(R9);

  __ EmitEntryFrameVerification(R9);

  // Mark that the thread is executing Dart code. Do this after initializing the
  // exit link for the profiler.
  __ LoadImmediate(R9, VMTag::kDartTagId);
  __ StoreToOffset(R9, THR, target::Thread::vm_tag_offset());

  // Load arguments descriptor array into R4, which is passed to Dart code.
  __ mov(R4, Operand(R1));

  // Load number of arguments into R9 and adjust count for type arguments.
  __ ldr(R3,
         FieldAddress(R4, target::ArgumentsDescriptor::type_args_len_offset()));
  __ ldr(R9, FieldAddress(R4, target::ArgumentsDescriptor::count_offset()));
  __ cmp(R3, Operand(0));
  __ AddImmediate(R9, R9, target::ToRawSmi(1),
                  NE);  // Include the type arguments.
  __ SmiUntag(R9);

  // Compute address of 'arguments array' data area into R2.
  __ AddImmediate(R2, R2, target::Array::data_offset() - kHeapObjectTag);

  // Set up arguments for the Dart call.
  Label push_arguments;
  Label done_push_arguments;
  __ CompareImmediate(R9, 0);  // check if there are arguments.
  __ b(&done_push_arguments, EQ);
  __ LoadImmediate(R1, 0);
  __ Bind(&push_arguments);
  __ ldr(R3, Address(R2));
  __ Push(R3);
  __ AddImmediate(R2, target::kWordSize);
  __ AddImmediate(R1, 1);
  __ cmp(R1, Operand(R9));
  __ b(&push_arguments, LT);
  __ Bind(&done_push_arguments);

  // Call the Dart code entrypoint.
  if (FLAG_precompiled_mode) {
    __ SetupGlobalPoolAndDispatchTable();
    __ LoadImmediate(CODE_REG, 0);  // GC safe value into CODE_REG.
  } else {
    __ LoadImmediate(PP, 0);  // GC safe value into PP.
    __ mov(CODE_REG, Operand(R0));
    __ ldr(R0, FieldAddress(CODE_REG, target::Code::entry_point_offset()));
  }
  __ blx(R0);  // R4 is the arguments descriptor array.

  // Get rid of arguments pushed on the stack.
  __ AddImmediate(
      SP, FP,
      target::frame_layout.exit_link_slot_from_entry_fp * target::kWordSize);

  // Restore the saved top exit frame info and top resource back into the
  // Isolate structure. Uses R9 as a temporary register for this.
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::top_exit_frame_info_offset());
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::exit_through_ffi_offset());
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::top_resource_offset());

  // Restore the current VMTag from the stack.
  __ Pop(R4);
  __ StoreToOffset(R4, THR, target::Thread::vm_tag_offset());

#if defined(USING_SHADOW_CALL_STACK)
#error Unimplemented
#endif

  __ PopNativeCalleeSavedRegisters();

  __ set_constant_pool_allowed(false);

  // Restore the frame pointer and return.
  RESTORES_LR_FROM_FRAME(__ LeaveFrame((1 << FP) | (1 << LR)));
  __ Ret();
}

// Called when invoking compiled Dart code from interpreted Dart code.
// Input parameters:
//   LR : points to return address.
//   R0 : target code or entry point (in AOT mode).
//   R1 : arguments descriptor array.
//   R2 : address of first argument.
//   R3 : current thread.
void StubCodeCompiler::GenerateInvokeDartCodeFromBytecodeStub() {
#if defined(DART_DYNAMIC_MODULES)
  SPILLS_LR_TO_FRAME(__ EnterFrame((1 << FP) | (1 << LR), 0));

  // Push code object to PC marker slot.
  __ ldr(IP,
         Address(R3,
                 target::Thread::invoke_dart_code_from_bytecode_stub_offset()));
  __ Push(IP);

  __ PushNativeCalleeSavedRegisters();

  // Set up THR, which caches the current thread in Dart code.
  if (THR != R3) {
    __ mov(THR, Operand(R3));
  }

#if defined(USING_SHADOW_CALL_STACK)
#error Unimplemented
#endif

  // Save the current VMTag on the stack.
  __ LoadFromOffset(R9, THR, target::Thread::vm_tag_offset());
  __ Push(R9);

  // Save top resource and top exit frame info. Use R4-6 as temporary registers.
  // StackFrameIterator reads the top exit frame info saved in this frame.
  __ LoadFromOffset(R4, THR, target::Thread::top_resource_offset());
  __ Push(R4);
  __ LoadImmediate(R8, 0);
  __ StoreToOffset(R8, THR, target::Thread::top_resource_offset());

  __ LoadFromOffset(R8, THR, target::Thread::exit_through_ffi_offset());
  __ Push(R8);
  __ LoadImmediate(R8, 0);
  __ StoreToOffset(R8, THR, target::Thread::exit_through_ffi_offset());

  __ LoadFromOffset(R9, THR, target::Thread::top_exit_frame_info_offset());
  __ StoreToOffset(R8, THR, target::Thread::top_exit_frame_info_offset());

  // target::frame_layout.exit_link_slot_from_entry_fp must be kept in sync
  // with the code below.
#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
  ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -27);
#else
  ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -28);
#endif
  __ Push(R9);

  __ EmitEntryFrameVerification(R9);

  // Mark that the thread is executing Dart code. Do this after initializing the
  // exit link for the profiler.
  __ LoadImmediate(R9, VMTag::kDartTagId);
  __ StoreToOffset(R9, THR, target::Thread::vm_tag_offset());

  // Load arguments descriptor array into R4, which is passed to Dart code.
  __ mov(R4, Operand(R1));

  // Load number of arguments into R9 and adjust count for type arguments.
  __ ldr(R3,
         FieldAddress(R4, target::ArgumentsDescriptor::type_args_len_offset()));
  __ ldr(R9, FieldAddress(R4, target::ArgumentsDescriptor::count_offset()));
  __ cmp(R3, Operand(0));
  __ AddImmediate(R9, R9, target::ToRawSmi(1),
                  NE);  // Include the type arguments.
  __ SmiUntag(R9);

  // R2 points to first argument.
  // Set up arguments for the Dart call.
  Label push_arguments;
  Label done_push_arguments;
  __ CompareImmediate(R9, 0);  // check if there are arguments.
  __ b(&done_push_arguments, EQ);
  __ LoadImmediate(R1, 0);
  __ Bind(&push_arguments);
  __ ldr(R3, Address(R2));
  __ Push(R3);
  __ AddImmediate(R2, target::kWordSize);
  __ AddImmediate(R1, 1);
  __ cmp(R1, Operand(R9));
  __ b(&push_arguments, LT);
  __ Bind(&done_push_arguments);

  // Call the Dart code entrypoint.
  if (FLAG_precompiled_mode) {
    __ SetupGlobalPoolAndDispatchTable();
    __ LoadImmediate(CODE_REG, 0);  // GC safe value into CODE_REG.
  } else {
    __ LoadImmediate(PP, 0);  // GC safe value into PP.
    __ mov(CODE_REG, Operand(R0));
    __ ldr(R0, FieldAddress(CODE_REG, target::Code::entry_point_offset()));
  }
  __ blx(R0);  // R4 is the arguments descriptor array.

  // Get rid of arguments pushed on the stack.
  __ AddImmediate(
      SP, FP,
      target::frame_layout.exit_link_slot_from_entry_fp * target::kWordSize);

  // Restore the saved top exit frame info and top resource back into the
  // Isolate structure. Uses R9 as a temporary register for this.
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::top_exit_frame_info_offset());
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::exit_through_ffi_offset());
  __ Pop(R9);
  __ StoreToOffset(R9, THR, target::Thread::top_resource_offset());

  // Restore the current VMTag from the stack.
  __ Pop(R4);
  __ StoreToOffset(R4, THR, target::Thread::vm_tag_offset());

#if defined(USING_SHADOW_CALL_STACK)
#error Unimplemented
#endif

  __ PopNativeCalleeSavedRegisters();

  __ set_constant_pool_allowed(false);

  // Restore the frame pointer and return.
  RESTORES_LR_FROM_FRAME(__ LeaveFrame((1 << FP) | (1 << LR)));
  __ Ret();

#else
  __ Stop("Not using Dart dynamic modules");
#endif  // defined(DART_DYNAMIC_MODULES)
}

// Helper to generate space allocation of context stub.
// This does not initialise the fields of the context.
// Input:
//   R1: number of context variables.
// Output:
//   R0: new allocated Context object.
// Clobbered:
//   R2, R3, R8, R9
static void GenerateAllocateContext(Assembler* assembler, Label* slow_case) {
  // First compute the rounded instance size.
  // R1: number of context variables.
  const intptr_t fixed_size_plus_alignment_padding =
      target::Context::header_size() +
      target::ObjectAlignment::kObjectAlignment - 1;
  __ LoadImmediate(R2, fixed_size_plus_alignment_padding);
  __ add(R2, R2, Operand(R1, LSL, 2));
  ASSERT(kSmiTagShift == 1);
  __ bic(R2, R2, Operand(target::ObjectAlignment::kObjectAlignment - 1));

  NOT_IN_PRODUCT(__ MaybeTraceAllocation(kContextCid, slow_case, R8));
  // Now allocate the object.
  // R1: number of context variables.
  // R2: object size.
  __ ldr(R0, Address(THR, target::Thread::top_offset()));
  __ add(R3, R2, Operand(R0));
  // Check if the allocation fits into the remaining space.
  // R0: potential new object.
  // R1: number of context variables.
  // R2: object size.
  // R3: potential next object start.
  __ ldr(IP, Address(THR, target::Thread::end_offset()));
  __ cmp(R3, Operand(IP));
  __ b(slow_case, CS);  // Branch if unsigned higher or equal.
  __ CheckAllocationCanary(R0);

  // Successfully allocated the object, now update top to point to
  // next object start and initialize the object.
  // R0: new object start (untagged).
  // R1: number of context variables.
  // R2: object size.
  // R3: next object start.
  __ str(R3, Address(THR, target::Thread::top_offset()));
  __ add(R0, R0, Operand(kHeapObjectTag));

  // Calculate the size tag.
  // R0: new object (tagged).
  // R1: number of context variables.
  // R2: object size.
  // R3: next object start.
  const intptr_t shift = target::UntaggedObject::kTagBitsSizeTagPos -
                         target::ObjectAlignment::kObjectAlignmentLog2;
  __ CompareImmediate(R2, target::UntaggedObject::kSizeTagMaxSizeTag);
  // If no size tag overflow, shift R2 left, else set R2 to zero.
  __ mov(R9, Operand(R2, LSL, shift), LS);
  __ mov(R9, Operand(0), HI);

  // Get the class index and insert it into the tags.
  // R9: size and bit tags.
  const uword tags =
      target::MakeTagWordForNewSpaceObject(kContextCid, /*instance_size=*/0);

  __ LoadImmediate(IP, tags);
  __ orr(R9, R9, Operand(IP));
  __ InitializeHeader(R9, R0);

  // Setup up number of context variables field.
  // R0: new object.
  // R1: number of context variables as integer value (not object).
  // R2: object size.
  // R3: next object start.
  __ str(R1, FieldAddress(R0, target::Context::num_variables_offset()));
}

// Called for inline allocation of contexts.
// Input:
//   R1: number of context variables.
// Output:
//   R0: new allocated Context object.
// Clobbered:
//   Potentially any since is can go to runtime.
void StubCodeCompiler::GenerateAllocateContextStub() {
  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label slow_case;

    GenerateAllocateContext(assembler, &slow_case);

    // Setup the parent field.
    // R0: new object.
    // R2: object size.
    // R3: next object start.
    __ LoadObject(R8, NullObject());
    __ MoveRegister(R9, R8);  // Needed for InitializeFieldsNoBarrier.
    __ StoreIntoObjectNoBarrier(
        R0, FieldAddress(R0, target::Context::parent_offset()), R8);

    // Initialize the context variables.
    // R0: new object.
    // R2: object size.
    // R3: next object start.
    // R8, R9: raw null.
    __ AddImmediate(R1, R0,
                    target::Context::variable_offset(0) - kHeapObjectTag);
    __ InitializeFieldsNoBarrier(R0, R1, R3, R8, R9);

    // Done allocating and initializing the context.
    // R0: new object.
    __ Ret();

    __ Bind(&slow_case);
  }

  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  // Setup space on stack for return value.
  __ LoadImmediate(R2, 0);
  __ SmiTag(R1);
  __ PushList((1 << R1) | (1 << R2));
  __ CallRuntime(kAllocateContextRuntimeEntry, 1);  // Allocate context.
  __ Drop(1);  // Pop number of context variables argument.
  __ Pop(R0);  // Pop the new context object.

  // Write-barrier elimination might be enabled for this context (depending on
  // the size). To be sure we will check if the allocated object is in old
  // space and if so call a leaf runtime to add it to the remembered set.
  EnsureIsNewOrRemembered();

  // R0: new object
  // Restore the frame pointer.
  __ LeaveStubFrame();

  __ Ret();
}

// Called for clone of contexts.
// Input:
//   R4: context variable to clone.
// Output:
//   R0: new allocated Context object.
// Clobbered:
//   Potentially any since it can go to runtime.
void StubCodeCompiler::GenerateCloneContextStub() {
  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label slow_case;

    // Load num. variable in the existing context.
    __ ldr(R1, FieldAddress(R4, target::Context::num_variables_offset()));

    GenerateAllocateContext(assembler, &slow_case);

    // Load parent in the existing context.
    __ ldr(R2, FieldAddress(R4, target::Context::parent_offset()));
    // Setup the parent field.
    // R0: new object.
    __ StoreIntoObjectNoBarrier(
        R0, FieldAddress(R0, target::Context::parent_offset()), R2);

    // Clone the context variables.
    // R0: new object.
    // R1: number of context variables.
    {
      Label loop, done;
      __ AddImmediate(R2, R0,
                      target::Context::variable_offset(0) - kHeapObjectTag);
      __ AddImmediate(R3, R4,
                      target::Context::variable_offset(0) - kHeapObjectTag);

      __ Bind(&loop);
      __ subs(R1, R1, Operand(1));
      __ b(&done, MI);

      __ ldr(R9, Address(R3, R1, LSL, target::kWordSizeLog2));
      __ str(R9, Address(R2, R1, LSL, target::kWordSizeLog2));

      __ b(&loop, NE);  // Loop if R1 not zero.

      __ Bind(&done);
    }

    // Done allocating and initializing the context.
    // R0: new object.
    __ Ret();

    __ Bind(&slow_case);
  }

  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  // Setup space on stack for return value.
  __ LoadImmediate(R0, 0);
  __ PushRegisterPair(R4, R0);
  __ CallRuntime(kCloneContextRuntimeEntry, 1);  // Clone context.
  // R4: Pop number of context variables argument.
  // R0: Pop the new context object.
  __ PopRegisterPair(R4, R0);

  // Write-barrier elimination might be enabled for this context (depending on
  // the size). To be sure we will check if the allocated object is in old
  // space and if so call a leaf runtime to add it to the remembered set.
  EnsureIsNewOrRemembered();

  // R0: new object
  // Restore the frame pointer.
  __ LeaveStubFrame();
  __ Ret();
}

void StubCodeCompiler::GenerateWriteBarrierWrappersStub() {
  for (intptr_t i = 0; i < kNumberOfCpuRegisters; ++i) {
    if ((kDartAvailableCpuRegs & (1 << i)) == 0) continue;

    Register reg = static_cast<Register>(i);
    intptr_t start = __ CodeSize();
    SPILLS_LR_TO_FRAME(__ PushList((1 << LR) | (1 << kWriteBarrierObjectReg)));
    __ mov(kWriteBarrierObjectReg, Operand(reg));
    __ Call(Address(THR, target::Thread::write_barrier_entry_point_offset()));
    RESTORES_LR_FROM_FRAME(
        __ PopList((1 << LR) | (1 << kWriteBarrierObjectReg)));
    READS_RETURN_ADDRESS_FROM_LR(__ bx(LR));
    intptr_t end = __ CodeSize();

    RELEASE_ASSERT(end - start == kStoreBufferWrapperSize);
  }
}

// Helper stub to implement Assembler::StoreIntoObject.
// Input parameters:
//   R1: Object (old)
//   R0: Value (old or new)
//   R9: Slot
// If R0 is new, add R1 to the store buffer. Otherwise R0 is old, mark R0
// and add it to the mark list.
COMPILE_ASSERT(kWriteBarrierObjectReg == R1);
COMPILE_ASSERT(kWriteBarrierValueReg == R0);
COMPILE_ASSERT(kWriteBarrierSlotReg == R9);
static void GenerateWriteBarrierStubHelper(Assembler* assembler, bool cards) {
  Label skip_marking;
  __ Push(R2);
  __ ldr(TMP, FieldAddress(R0, target::Object::tags_offset()));
  __ ldr(R2, Address(THR, target::Thread::write_barrier_mask_offset()));
  __ and_(TMP, TMP, Operand(R2));
  __ Pop(R2);
  __ tst(TMP, Operand(target::UntaggedObject::kIncrementalBarrierMask));
  __ b(&skip_marking, ZERO);

  {
    // Atomically clear kNotMarkedBit.
    Label retry, is_new, done;
    __ PushList((1 << R2) | (1 << R3) | (1 << R4));  // Spill.
    __ AddImmediate(R3, R0, target::Object::tags_offset() - kHeapObjectTag);
    // R3: Untagged address of header word (ldrex/strex do not support offsets).
    __ Bind(&retry);
    __ ldrex(R2, R3);
    __ tst(R2, Operand(1 << target::UntaggedObject::kNotMarkedBit));
    __ b(&done, ZERO);  // Marked by another thread.
    __ bic(R2, R2, Operand(1 << target::UntaggedObject::kNotMarkedBit));
    __ strex(R4, R2, R3);
    __ cmp(R4, Operand(1));
    __ b(&retry, EQ);

    __ tst(R0, Operand(1 << target::ObjectAlignment::kNewObjectBitPosition));
    __ b(&is_new, NOT_ZERO);

    auto mark_stack_push = [&](intptr_t offset, const RuntimeEntry& entry) {
      __ ldr(R4, Address(THR, offset));
      __ ldr(R2, Address(R4, target::MarkingStackBlock::top_offset()));
      __ add(R3, R4, Operand(R2, LSL, target::kWordSizeLog2));
      __ str(R0, Address(R3, target::MarkingStackBlock::pointers_offset()));
      __ add(R2, R2, Operand(1));
      __ str(R2, Address(R4, target::MarkingStackBlock::top_offset()));
      __ CompareImmediate(R2, target::MarkingStackBlock::kSize);
      __ b(&done, NE);

      {
        LeafRuntimeScope rt(assembler, /*frame_size=*/0,
                            /*preserve_registers=*/true);
        __ mov(R0, Operand(THR));
        rt.Call(entry, 1);
      }
    };

    mark_stack_push(target::Thread::old_marking_stack_block_offset(),
                    kOldMarkingStackBlockProcessRuntimeEntry);
    __ b(&done);

    __ Bind(&is_new);
    mark_stack_push(target::Thread::new_marking_stack_block_offset(),
                    kNewMarkingStackBlockProcessRuntimeEntry);

    __ Bind(&done);
    __ clrex();
    __ PopList((1 << R2) | (1 << R3) | (1 << R4));  // Unspill.
  }

  Label add_to_remembered_set, remember_card;
  __ Bind(&skip_marking);
  __ Push(R2);
  __ ldr(TMP, FieldAddress(R1, target::Object::tags_offset()));
  __ ldr(R2, FieldAddress(R0, target::Object::tags_offset()));
  __ and_(TMP, R2,
          Operand(TMP, LSR, target::UntaggedObject::kBarrierOverlapShift));
  __ Pop(R2);
  __ tst(TMP, Operand(target::UntaggedObject::kGenerationalBarrierMask));
  __ b(&add_to_remembered_set, NOT_ZERO);
  __ Ret();

  __ Bind(&add_to_remembered_set);
  if (cards) {
    __ ldr(TMP, FieldAddress(R1, target::Object::tags_offset()));
    __ tst(TMP, Operand(1 << target::UntaggedObject::kCardRememberedBit));
    __ b(&remember_card, NOT_ZERO);
  } else {
#if defined(DEBUG)
    Label ok;
    __ ldr(TMP, FieldAddress(R1, target::Object::tags_offset()));
    __ tst(TMP, Operand(1 << target::UntaggedObject::kCardRememberedBit));
    __ b(&ok, ZERO);
    __ Stop("Wrong barrier");
    __ Bind(&ok);
#endif
  }

  {
    // Atomically clear kOldAndNotRememberedBit.
    Label retry, done;
    __ PushList((1 << R2) | (1 << R3) | (1 << R4));
    __ AddImmediate(R3, R1, target::Object::tags_offset() - kHeapObjectTag);
    // R3: Untagged address of header word (ldrex/strex do not support offsets).
    __ Bind(&retry);
    __ ldrex(R2, R3);
    __ tst(R2, Operand(1 << target::UntaggedObject::kOldAndNotRememberedBit));
    __ b(&done, ZERO);  // Remembered by another thread.
    __ bic(R2, R2,
           Operand(1 << target::UntaggedObject::kOldAndNotRememberedBit));
    __ strex(R4, R2, R3);
    __ cmp(R4, Operand(1));
    __ b(&retry, EQ);

    // Load the StoreBuffer block out of the thread. Then load top_ out of the
    // StoreBufferBlock and add the address to the pointers_.
    __ ldr(R4, Address(THR, target::Thread::store_buffer_block_offset()));
    __ ldr(R2, Address(R4, target::StoreBufferBlock::top_offset()));
    __ add(R3, R4, Operand(R2, LSL, target::kWordSizeLog2));
    __ str(R1, Address(R3, target::StoreBufferBlock::pointers_offset()));

    // Increment top_ and check for overflow.
    // R2: top_.
    // R4: StoreBufferBlock.
    __ add(R2, R2, Operand(1));
    __ str(R2, Address(R4, target::StoreBufferBlock::top_offset()));
    __ CompareImmediate(R2, target::StoreBufferBlock::kSize);
    __ b(&done, NE);

    {
      LeafRuntimeScope rt(assembler, /*frame_size=*/0,
                          /*preserve_registers=*/true);
      __ mov(R0, Operand(THR));
      rt.Call(kStoreBufferBlockProcessRuntimeEntry, 1);
    }

    __ Bind(&done);
    __ PopList((1 << R2) | (1 << R3) | (1 << R4));
    __ Ret();
  }
  if (cards) {
    Label retry;

    // Get card table.
    __ Bind(&remember_card);
    __ AndImmediate(TMP, R1, target::kPageMask);  // Page.
    __ ldr(TMP,
           Address(TMP, target::Page::card_table_offset()));  // Card table.

    // Atomically dirty the card.
    __ PushList((1 << R0) | (1 << R1) | (1 << R2));
    __ AndImmediate(TMP, R1, target::kPageMask);  // Page.
    __ sub(R9, R9, Operand(TMP));                 // Offset in page.
    __ Lsr(R9, R9, Operand(target::Page::kBytesPerCardLog2));  // Card index.
    __ AndImmediate(R1, R9, target::kBitsPerWord - 1);  // Lsl is not mod 32.
    __ LoadImmediate(R0, 1);                            // Bit offset.
    __ Lsl(R0, R0, R1);                                 // Bit mask.
    __ ldr(TMP,
           Address(TMP, target::Page::card_table_offset()));    // Card table.
    __ Lsr(R9, R9, Operand(target::kBitsPerWordLog2));          // Word index.
    __ add(TMP, TMP, Operand(R9, LSL, target::kWordSizeLog2));  // Word address.

    __ Bind(&retry);
    __ ldrex(R1, TMP);
    __ orr(R1, R1, Operand(R0));
    __ strex(R2, R1, TMP);
    __ cmp(R2, Operand(1));
    __ b(&retry, EQ);
    __ PopList((1 << R0) | (1 << R1) | (1 << R2));
    __ Ret();
  }
}

void StubCodeCompiler::GenerateWriteBarrierStub() {
  GenerateWriteBarrierStubHelper(assembler, false);
}

void StubCodeCompiler::GenerateArrayWriteBarrierStub() {
  GenerateWriteBarrierStubHelper(assembler, true);
}

static void GenerateAllocateObjectHelper(Assembler* assembler,
                                         bool is_cls_parameterized) {
  const Register kTagsReg = AllocateObjectABI::kTagsReg;

  {
    Label slow_case;

#if !defined(PRODUCT)
    {
      const Register kTraceAllocationTempReg = R8;
      const Register kCidRegister = R9;
      __ ExtractClassIdFromTags(kCidRegister, AllocateObjectABI::kTagsReg);
      __ MaybeTraceAllocation(kCidRegister, &slow_case,
                              kTraceAllocationTempReg);
    }
#endif

    const Register kNewTopReg = R8;

    // Bump allocation.
    {
      const Register kEndReg = R1;
      const Register kInstanceSizeReg = R9;

      __ ExtractInstanceSizeFromTags(kInstanceSizeReg, kTagsReg);

      // Load two words from Thread::top: top and end.
      // AllocateObjectABI::kResultReg: potential next object start.
      __ ldrd(AllocateObjectABI::kResultReg, kEndReg, THR,
              target::Thread::top_offset());

      __ add(kNewTopReg, AllocateObjectABI::kResultReg,
             Operand(kInstanceSizeReg));

      __ CompareRegisters(kEndReg, kNewTopReg);
      __ b(&slow_case, UNSIGNED_LESS_EQUAL);

      // Successfully allocated the object, now update top to point to
      // next object start and store the class in the class field of object.
      __ str(kNewTopReg, Address(THR, target::Thread::top_offset()));
    }  //  kEndReg = R1, kInstanceSizeReg = R9

    // Tags.
    __ InitializeHeaderUntagged(kTagsReg, AllocateObjectABI::kResultReg);

    // Initialize the remaining words of the object.
    {
      const Register kFieldReg = R1;
      const Register kNullReg = R9;

      __ LoadObject(kNullReg, NullObject());

      __ AddImmediate(kFieldReg, AllocateObjectABI::kResultReg,
                      target::Instance::first_field_offset());
      Label done, init_loop;
      __ Bind(&init_loop);
      __ CompareRegisters(kFieldReg, kNewTopReg);
      __ b(&done, UNSIGNED_GREATER_EQUAL);
      __ str(kNullReg,
             Address(kFieldReg, target::kWordSize, Address::PostIndex));
      __ b(&init_loop);

      __ Bind(&done);
    }  // kFieldReg = R1, kNullReg = R9

    __ AddImmediate(AllocateObjectABI::kResultReg,
                    AllocateObjectABI::kResultReg, kHeapObjectTag);

    // Store parameterized type.
    if (is_cls_parameterized) {
      Label not_parameterized_case;

      const Register kClsIdReg = R2;
      const Register kTypeOffsetReg = R9;

      __ ExtractClassIdFromTags(kClsIdReg, kTagsReg);

      // Load class' type_arguments_field offset in words.
      __ LoadClassById(kTypeOffsetReg, kClsIdReg);
      __ ldr(
          kTypeOffsetReg,
          FieldAddress(kTypeOffsetReg,
                       target::Class::
                           host_type_arguments_field_offset_in_words_offset()));

      // Set the type arguments in the new object.
      __ add(kTypeOffsetReg, AllocateObjectABI::kResultReg,
             Operand(kTypeOffsetReg, LSL, target::kWordSizeLog2));
      __ StoreIntoObjectNoBarrier(AllocateObjectABI::kResultReg,
                                  FieldAddress(kTypeOffsetReg, 0),
                                  AllocateObjectABI::kTypeArgumentsReg);

      __ Bind(&not_parameterized_case);
    }  // kClsIdReg = R1, kTypeOffsetReg = R9

    __ Ret();

    __ Bind(&slow_case);
  }  // kNewTopReg = R8

  // Fall back on slow case:
  {
    const Register kStubReg = R8;

    if (!is_cls_parameterized) {
      __ LoadObject(AllocateObjectABI::kTypeArgumentsReg, NullObject());
    }

    // Tail call to generic allocation stub.
    __ ldr(kStubReg,
           Address(THR,
                   target::Thread::allocate_object_slow_entry_point_offset()));
    __ bx(kStubReg);
  }  // kStubReg = R8
}

// Called for inline allocation of objects (any class).
void StubCodeCompiler::GenerateAllocateObjectStub() {
  GenerateAllocateObjectHelper(assembler, /*is_cls_parameterized=*/false);
}

void StubCodeCompiler::GenerateAllocateObjectParameterizedStub() {
  GenerateAllocateObjectHelper(assembler, /*is_cls_parameterized=*/true);
}

void StubCodeCompiler::GenerateAllocateObjectSlowStub() {
  const Register kClsReg = R1;

  if (!FLAG_precompiled_mode) {
    __ ldr(CODE_REG,
           Address(THR, target::Thread::call_to_runtime_stub_offset()));
  }

  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();

  __ ExtractClassIdFromTags(AllocateObjectABI::kResultReg,
                            AllocateObjectABI::kTagsReg);
  __ LoadClassById(kClsReg, AllocateObjectABI::kResultReg);

  __ LoadObject(AllocateObjectABI::kResultReg, NullObject());

  // Pushes result slot, then parameter class and type arguments.
  // Type arguments should be Object::null() if class is non-parameterized.
  __ PushRegistersInOrder({AllocateObjectABI::kResultReg, kClsReg,
                           AllocateObjectABI::kTypeArgumentsReg});

  __ CallRuntime(kAllocateObjectRuntimeEntry, 2);

  // Load result off the stack into result register.
  __ ldr(AllocateObjectABI::kResultReg, Address(SP, 2 * target::kWordSize));

  // Write-barrier elimination is enabled for [cls] and we therefore need to
  // ensure that the object is in new-space or has remembered bit set.
  EnsureIsNewOrRemembered();

  __ LeaveDartFrameAndReturn();
}

// Called for inline allocation of objects.
void StubCodeCompiler::GenerateAllocationStubForClass(
    UnresolvedPcRelativeCalls* unresolved_calls,
    const Class& cls,
    const Code& allocate_object,
    const Code& allocat_object_parametrized) {
  classid_t cls_id = target::Class::GetId(cls);
  ASSERT(cls_id != kIllegalCid);

  // The generated code is different if the class is parameterized.
  const bool is_cls_parameterized = target::Class::NumTypeArguments(cls) > 0;
  ASSERT(!is_cls_parameterized || target::Class::TypeArgumentsFieldOffset(
                                      cls) != target::Class::kNoTypeArguments);

  const intptr_t instance_size = target::Class::GetInstanceSize(cls);
  ASSERT(instance_size > 0);

  const uword tags =
      target::MakeTagWordForNewSpaceObject(cls_id, instance_size);

  const Register kTagsReg = AllocateObjectABI::kTagsReg;

  __ LoadImmediate(kTagsReg, tags);

  if (!FLAG_use_slow_path && FLAG_inline_alloc &&
      !target::Class::TraceAllocation(cls) &&
      target::SizeFitsInSizeTag(instance_size)) {
    RELEASE_ASSERT(AllocateObjectInstr::WillAllocateNewOrRemembered(cls));
    RELEASE_ASSERT(target::Heap::IsAllocatableInNewSpace(instance_size));

    if (is_cls_parameterized) {
      if (!IsSameObject(NullObject(),
                        CastHandle<Object>(allocat_object_parametrized))) {
        __ GenerateUnRelocatedPcRelativeTailCall();
        unresolved_calls->Add(new UnresolvedPcRelativeCall(
            __ CodeSize(), allocat_object_parametrized, /*is_tail_call=*/true));
      } else {
        __ ldr(PC,
               Address(THR,
                       target::Thread::
                           allocate_object_parameterized_entry_point_offset()));
      }
    } else {
      if (!IsSameObject(NullObject(), CastHandle<Object>(allocate_object))) {
        __ GenerateUnRelocatedPcRelativeTailCall();
        unresolved_calls->Add(new UnresolvedPcRelativeCall(
            __ CodeSize(), allocate_object, /*is_tail_call=*/true));
      } else {
        __ ldr(
            PC,
            Address(THR, target::Thread::allocate_object_entry_point_offset()));
      }
    }
  } else {
    if (!is_cls_parameterized) {
      __ LoadObject(AllocateObjectABI::kTypeArgumentsReg, NullObject());
    }
    __ ldr(PC,
           Address(THR,
                   target::Thread::allocate_object_slow_entry_point_offset()));
  }
}

// Called for invoking "dynamic noSuchMethod(Invocation invocation)" function
// from the entry code of a dart function after an error in passed argument
// name or number is detected.
// Input parameters:
//  LR : return address.
//  SP : address of last argument.
//  R4: arguments descriptor array.
void StubCodeCompiler::GenerateCallClosureNoSuchMethodStub() {
  __ EnterStubFrame();

  // Load the receiver.
  __ ldr(R2, FieldAddress(R4, target::ArgumentsDescriptor::count_offset()));
  __ add(IP, FP, Operand(R2, LSL, 1));  // R2 is Smi.
  __ ldr(R8, Address(IP, target::frame_layout.param_end_from_fp *
                             target::kWordSize));

  // Load the function.
  __ ldr(R6, FieldAddress(R8, target::Closure::function_offset()));

  // Push space for the return value.
  // Push the receiver.
  // Push arguments descriptor array.
  __ LoadImmediate(IP, 0);
  __ PushList((1 << R4) | (1 << R6) | (1 << R8) | (1 << IP));

  // Adjust arguments count.
  __ ldr(R3,
         FieldAddress(R4, target::ArgumentsDescriptor::type_args_len_offset()));
  __ cmp(R3, Operand(0));
  __ AddImmediate(R2, R2, target::ToRawSmi(1),
                  NE);  // Include the type arguments.

  // R2: Smi-tagged arguments array length.
  PushArrayOfArguments(assembler);

  const intptr_t kNumArgs = 4;
  __ CallRuntime(kNoSuchMethodFromPrologueRuntimeEntry, kNumArgs);
  // noSuchMethod on closures always throws an error, so it will never return.
  __ bkpt(0);
}

//  R8: function object.
//  R9: inline cache data object.
// Cannot use function object from ICData as it may be the inlined
// function and not the top-scope function.
void StubCodeCompiler::GenerateOptimizedUsageCounterIncrement() {
  Register func_reg = R8;
  if (FLAG_precompiled_mode) {
    __ Breakpoint();
    return;
  }
  __ ldr(TMP, FieldAddress(func_reg, target::Function::usage_counter_offset()));
  __ add(TMP, TMP, Operand(1));
  __ str(TMP, FieldAddress(func_reg, target::Function::usage_counter_offset()));
}

// Loads function into 'temp_reg'.
void StubCodeCompiler::GenerateUsageCounterIncrement(Register temp_reg) {
  if (FLAG_precompiled_mode) {
    __ Breakpoint();
    return;
  }
  if (FLAG_optimization_counter_threshold >= 0) {
    Register func_reg = temp_reg;
    ASSERT(temp_reg == R8);
    __ Comment("Increment function counter");
    __ ldr(func_reg, FieldAddress(IC_DATA_REG, target::ICData::owner_offset()));
    __ ldr(TMP,
           FieldAddress(func_reg, target::Function::usage_counter_offset()));
    __ add(TMP, TMP, Operand(1));
    __ str(TMP,
           FieldAddress(func_reg, target::Function::usage_counter_offset()));
  }
}

// Note: R9 must be preserved.
// Attempt a quick Smi operation for known operations ('kind'). The ICData
// must have been primed with a Smi/Smi check that will be used for counting
// the invocations.
static void EmitFastSmiOp(Assembler* assembler,
                          Token::Kind kind,
                          intptr_t num_args,
                          Label* not_smi_or_overflow) {
  __ Comment("Fast Smi op");
  __ ldr(R0, Address(SP, 1 * target::kWordSize));  // Left.
  __ ldr(R1, Address(SP, 0 * target::kWordSize));  // Right.
  __ orr(TMP, R0, Operand(R1));
  __ tst(TMP, Operand(kSmiTagMask));
  __ b(not_smi_or_overflow, NE);
  switch (kind) {
    case Token::kADD: {
      __ adds(R0, R1, Operand(R0));   // Adds.
      __ b(not_smi_or_overflow, VS);  // Branch if overflow.
      break;
    }
    case Token::kLT: {
      __ cmp(R0, Operand(R1));
      __ LoadObject(R0, CastHandle<Object>(TrueObject()), LT);
      __ LoadObject(R0, CastHandle<Object>(FalseObject()), GE);
      break;
    }
    case Token::kEQ: {
      __ cmp(R0, Operand(R1));
      __ LoadObject(R0, CastHandle<Object>(TrueObject()), EQ);
      __ LoadObject(R0, CastHandle<Object>(FalseObject()), NE);
      break;
    }
    default:
      UNIMPLEMENTED();
  }
  // R9: IC data object (preserved).
  __ ldr(R8, FieldAddress(R9, target::ICData::entries_offset()));
  // R8: ic_data_array with check entries: classes and target functions.
  __ AddImmediate(R8, target::Array::data_offset() - kHeapObjectTag);
// R8: points directly to the first ic data array element.
#if defined(DEBUG)
  // Check that first entry is for Smi/Smi.
  Label error, ok;
  const intptr_t imm_smi_cid = target::ToRawSmi(kSmiCid);
  __ ldr(R1, Address(R8, 0));
  __ CompareImmediate(R1, imm_smi_cid);
  __ b(&error, NE);
  __ ldr(R1, Address(R8, target::kWordSize));
  __ CompareImmediate(R1, imm_smi_cid);
  __ b(&ok, EQ);
  __ Bind(&error);
  __ Stop("Incorrect IC data");
  __ Bind(&ok);
#endif
  if (FLAG_optimization_counter_threshold >= 0) {
    // Update counter, ignore overflow.
    const intptr_t count_offset =
        target::ICData::CountIndexFor(num_args) * target::kWordSize;
    __ LoadFromOffset(R1, R8, count_offset);
    __ adds(R1, R1, Operand(target::ToRawSmi(1)));
    __ StoreIntoSmiField(Address(R8, count_offset), R1);
  }
  __ Ret();
}

// Saves the offset of the target entry-point (from the Function) into R3.
//
// Must be the first code generated, since any code before will be skipped in
// the unchecked entry-point.
static void GenerateRecordEntryPoint(Assembler* assembler) {
  Label done;
  __ mov(R3, Operand(target::Function::entry_point_offset() - kHeapObjectTag));
  __ b(&done);
  __ BindUncheckedEntryPoint();
  __ mov(
      R3,
      Operand(target::Function::entry_point_offset(CodeEntryKind::kUnchecked) -
              kHeapObjectTag));
  __ Bind(&done);
}

// Generate inline cache check for 'num_args'.
//  R0: receiver (if instance call)
//  R9: ICData
//  LR: return address
// Control flow:
// - If receiver is null -> jump to IC miss.
// - If receiver is Smi -> load Smi class.
// - If receiver is not-Smi -> load receiver's class.
// - Check if 'num_args' (including receiver) match any IC data group.
// - Match found -> jump to target.
// - Match not found -> jump to IC miss.
void StubCodeCompiler::GenerateNArgsCheckInlineCacheStub(
    intptr_t num_args,
    const RuntimeEntry& handle_ic_miss,
    Token::Kind kind,
    Optimized optimized,
    CallType type,
    Exactness exactness) {
  if (FLAG_precompiled_mode) {
    __ Breakpoint();
    return;
  }

  const bool save_entry_point = kind == Token::kILLEGAL;
  if (save_entry_point) {
    GenerateRecordEntryPoint(assembler);
  }

  if (optimized == kOptimized) {
    GenerateOptimizedUsageCounterIncrement();
  } else {
    GenerateUsageCounterIncrement(/* scratch */ R8);
  }

  __ CheckCodePointer();
  ASSERT(num_args == 1 || num_args == 2);
#if defined(DEBUG)
  {
    Label ok;
    // Check that the IC data array has NumArgsTested() == num_args.
    // 'NumArgsTested' is stored in the least significant bits of 'state_bits'.
    __ ldr(R8, FieldAddress(R9, target::ICData::state_bits_offset()));
    ASSERT(target::ICData::NumArgsTestedShift() == 0);  // No shift needed.
    __ and_(R8, R8, Operand(target::ICData::NumArgsTestedMask()));
    __ CompareImmediate(R8, num_args);
    __ b(&ok, EQ);
    __ Stop("Incorrect stub for IC data");
    __ Bind(&ok);
  }
#endif  // DEBUG

#if !defined(PRODUCT)
  Label stepping, done_stepping;
  if (optimized == kUnoptimized) {
    __ Comment("Check single stepping");
    __ ldrb(R8, Address(THR, target::Thread::single_step_offset()));
    __ CompareImmediate(R8, 0);
    __ b(&stepping, NE);
    __ Bind(&done_stepping);
  }
#endif

  Label not_smi_or_overflow;
  if (kind != Token::kILLEGAL) {
    EmitFastSmiOp(assembler, kind, num_args, &not_smi_or_overflow);
  }
  __ Bind(&not_smi_or_overflow);

  __ Comment("Extract ICData initial values and receiver cid");
  // R9: IC data object (preserved).
  __ ldr(R8, FieldAddress(R9, target::ICData::entries_offset()));
  // R8: ic_data_array with check entries: classes and target functions.
  const int kIcDataOffset = target::Array::data_offset() - kHeapObjectTag;
  // R8: points at the IC data array.

  if (type == kInstanceCall) {
    __ LoadTaggedClassIdMayBeSmi(NOTFP, R0);
    __ ldr(
        ARGS_DESC_REG,
        FieldAddress(R9, target::CallSiteData::arguments_descriptor_offset()));
    if (num_args == 2) {
      __ ldr(R1, FieldAddress(ARGS_DESC_REG,
                              target::ArgumentsDescriptor::count_offset()));
      __ sub(R1, R1, Operand(target::ToRawSmi(2)));
      __ ldr(R1, Address(SP, R1, LSL, 1));  // R1 (argument_count - 2) is Smi.
      __ LoadTaggedClassIdMayBeSmi(R1, R1);
    }
  } else {
    // Load arguments descriptor into R4.
    __ ldr(
        ARGS_DESC_REG,
        FieldAddress(R9, target::CallSiteData::arguments_descriptor_offset()));

    // Get the receiver's class ID (first read number of arguments from
    // arguments descriptor array and then access the receiver from the stack).
    __ ldr(R1, FieldAddress(ARGS_DESC_REG,
                            target::ArgumentsDescriptor::count_offset()));
    __ sub(R1, R1, Operand(target::ToRawSmi(1)));
    // R1: argument_count - 1 (smi).

    __ ldr(R0, Address(SP, R1, LSL, 1));  // R1 (argument_count - 1) is Smi.
    __ LoadTaggedClassIdMayBeSmi(NOTFP, R0);

    if (num_args == 2) {
      __ sub(R1, R1, Operand(target::ToRawSmi(1)));
      __ ldr(R1, Address(SP, R1, LSL, 1));  // R1 (argument_count - 2) is Smi.
      __ LoadTaggedClassIdMayBeSmi(R1, R1);
    }
  }
  // NOTFP: first argument class ID as Smi.
  // R1: second argument class ID as Smi.
  // R4: args descriptor

  // Loop that checks if there is an IC data match.
  Label loop, found, miss;
  __ Comment("ICData loop");

  // We unroll the generic one that is generated once more than the others.
  const bool optimize = kind == Token::kILLEGAL;

  __ Bind(&loop);
  for (int unroll = optimize ? 4 : 2; unroll >= 0; unroll--) {
    Label update;

    __ ldr(R2, Address(R8, kIcDataOffset));
    __ cmp(NOTFP, Operand(R2));  // Class id match?
    if (num_args == 2) {
      __ b(&update, NE);  // Continue.
      __ ldr(R2, Address(R8, kIcDataOffset + target::kWordSize));
      __ cmp(R1, Operand(R2));  // Class id match?
    }
    __ b(&found, EQ);  // Break.

    __ Bind(&update);

    const intptr_t entry_size = target::ICData::TestEntryLengthFor(
                                    num_args, exactness == kCheckExactness) *
                                target::kWordSize;
    __ AddImmediate(R8, entry_size);  // Next entry.

    __ CompareImmediate(R2, target::ToRawSmi(kIllegalCid));  // Done?
    if (unroll == 0) {
      __ b(&loop, NE);
    } else {
      __ b(&miss, EQ);
    }
  }

  __ Bind(&miss);
  __ Comment("IC miss");
  // Compute address of arguments.
  __ ldr(R1, FieldAddress(ARGS_DESC_REG,
                          target::ArgumentsDescriptor::count_offset()));
  __ sub(R1, R1, Operand(target::ToRawSmi(1)));
  // R1: argument_count - 1 (smi).
  __ add(R1, SP, Operand(R1, LSL, 1));  // R1 is Smi.
  // R1: address of receiver.
  // Create a stub frame as we are pushing some objects on the stack before
  // calling into the runtime.
  __ EnterStubFrame();
  __ LoadImmediate(R0, 0);
  // Preserve IC data object and arguments descriptor array and
  // setup space on stack for result (target code object).
  RegList regs = (1 << R0) | (1 << ARGS_DESC_REG) | (1 << R9);
  if (save_entry_point) {
    __ SmiTag(R3);
    regs |= 1 << R3;
  }
  __ PushList(regs);
  // Push call arguments.
  for (intptr_t i = 0; i < num_args; i++) {
    __ LoadFromOffset(TMP, R1, -i * target::kWordSize);
    __ Push(TMP);
  }
  // Pass IC data object.
  __ Push(R9);
  __ CallRuntime(handle_ic_miss, num_args + 1);
  // Remove the call arguments pushed earlier, including the IC data object.
  __ Drop(num_args + 1);
  // Pop returned function object into R0.
  // Restore arguments descriptor array and IC data array.
  COMPILE_ASSERT(FUNCTION_REG == R0);
  __ PopList(regs);
  if (save_entry_point) {
    __ SmiUntag(R3);
  }
  __ RestoreCodePointer();
  __ LeaveStubFrame();
  Label call_target_function;
  if (FLAG_precompiled_mode) {
    GenerateDispatcherCode(assembler, &call_target_function);
  } else {
    __ b(&call_target_function);
  }

  __ Bind(&found);
  // R8: pointer to an IC data check group.
  const intptr_t target_offset =
      target::ICData::TargetIndexFor(num_args) * target::kWordSize;
  const intptr_t count_offset =
      target::ICData::CountIndexFor(num_args) * target::kWordSize;
  const intptr_t exactness_offset =
      target::ICData::ExactnessIndexFor(num_args) * target::kWordSize;

  Label call_target_function_through_unchecked_entry;
  if (exactness == kCheckExactness) {
    Label exactness_ok;
    ASSERT(num_args == 1);
    __ ldr(R1, Address(R8, kIcDataOffset + exactness_offset));
    __ CompareImmediate(
        R1, target::ToRawSmi(
                StaticTypeExactnessState::HasExactSuperType().Encode()));
    __ BranchIf(LESS, &exactness_ok);
    __ BranchIf(EQUAL, &call_target_function_through_unchecked_entry);

    // Check trivial exactness.
    // Note: UntaggedICData::receivers_static_type_ is guaranteed to be not null
    // because we only emit calls to this stub when it is not null.
    __ ldr(R2,
           FieldAddress(R9, target::ICData::receivers_static_type_offset()));
    __ ldr(R2, FieldAddress(R2, target::Type::arguments_offset()));
    // R1 contains an offset to type arguments in words as a smi,
    // hence TIMES_2. R0 is guaranteed to be non-smi because it is expected
    // to have type argument.
    __ LoadIndexedPayload(TMP, R0, 0, R1, TIMES_2);
    __ CompareObjectRegisters(R2, TMP);
    __ BranchIf(EQUAL, &call_target_function_through_unchecked_entry);

    // Update exactness state (not-exact anymore).
    __ LoadImmediate(
        R1, target::ToRawSmi(StaticTypeExactnessState::NotExact().Encode()));
    __ str(R1, Address(R8, kIcDataOffset + exactness_offset));
    __ Bind(&exactness_ok);
  }
  __ LoadFromOffset(FUNCTION_REG, R8, kIcDataOffset + target_offset);

  if (FLAG_optimization_counter_threshold >= 0) {
    __ Comment("Update caller's counter");
    __ LoadFromOffset(R1, R8, kIcDataOffset + count_offset);
    __ add(R1, R1, Operand(target::ToRawSmi(1)));  // Ignore overflow.
    __ StoreIntoSmiField(Address(R8, kIcDataOffset + count_offset), R1);
  }

  __ Comment("Call target");
  __ Bind(&call_target_function);
  // R0: target function.
  __ ldr(CODE_REG, FieldAddress(FUNCTION_REG, target::Function::code_offset()));

  if (save_entry_point) {
    __ Branch(Address(FUNCTION_REG, R3));
  } else {
    __ Branch(
        FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));
  }

  if (exactness == kCheckExactness) {
    __ Bind(&call_target_function_through_unchecked_entry);
    if (FLAG_optimization_counter_threshold >= 0) {
      __ Comment("Update ICData counter");
      __ LoadFromOffset(R1, R8, kIcDataOffset + count_offset);
      __ add(R1, R1, Operand(target::ToRawSmi(1)));  // Ignore overflow.
      __ StoreIntoSmiField(Address(R8, kIcDataOffset + count_offset), R1);
    }
    __ Comment("Call target (via unchecked entry point)");
    __ LoadFromOffset(FUNCTION_REG, R8, kIcDataOffset + target_offset);
    __ ldr(CODE_REG,
           FieldAddress(FUNCTION_REG, target::Function::code_offset()));
    __ Branch(FieldAddress(FUNCTION_REG, target::Function::entry_point_offset(
                                             CodeEntryKind::kUnchecked)));
  }

#if !defined(PRODUCT)
  if (optimized == kUnoptimized) {
    __ Bind(&stepping);
    __ EnterStubFrame();
    if (type == kInstanceCall) {
      __ Push(R0);  // Preserve receiver.
    }
    RegList regs = 1 << R9;
    if (save_entry_point) {
      regs |= 1 << R3;
      __ SmiTag(R3);  // Entry-point is not Smi.
    }
    __ PushList(regs);  // Preserve IC data and entry-point.
    __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
    __ PopList(regs);  // Restore IC data and entry-point
    if (save_entry_point) {
      __ SmiUntag(R3);
    }
    if (type == kInstanceCall) {
      __ Pop(R0);
    }
    __ RestoreCodePointer();
    __ LeaveStubFrame();
    __ b(&done_stepping);
  }
#endif
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateOneArgCheckInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      1, kInlineCacheMissHandlerOneArgRuntimeEntry, Token::kILLEGAL,
      kUnoptimized, kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateOneArgCheckInlineCacheWithExactnessCheckStub() {
  GenerateNArgsCheckInlineCacheStub(
      1, kInlineCacheMissHandlerOneArgRuntimeEntry, Token::kILLEGAL,
      kUnoptimized, kInstanceCall, kCheckExactness);
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateTwoArgsCheckInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      2, kInlineCacheMissHandlerTwoArgsRuntimeEntry, Token::kILLEGAL,
      kUnoptimized, kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateSmiAddInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      2, kInlineCacheMissHandlerTwoArgsRuntimeEntry, Token::kADD, kUnoptimized,
      kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateSmiLessInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      2, kInlineCacheMissHandlerTwoArgsRuntimeEntry, Token::kLT, kUnoptimized,
      kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateSmiEqualInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      2, kInlineCacheMissHandlerTwoArgsRuntimeEntry, Token::kEQ, kUnoptimized,
      kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  R8: Function
//  LR: return address
void StubCodeCompiler::GenerateOneArgOptimizedCheckInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      1, kInlineCacheMissHandlerOneArgRuntimeEntry, Token::kILLEGAL, kOptimized,
      kInstanceCall, kIgnoreExactness);
}

//  R0: receiver
//  R9: ICData
//  R8: Function
//  LR: return address
void StubCodeCompiler::
    GenerateOneArgOptimizedCheckInlineCacheWithExactnessCheckStub() {
  GenerateNArgsCheckInlineCacheStub(
      1, kInlineCacheMissHandlerOneArgRuntimeEntry, Token::kILLEGAL, kOptimized,
      kInstanceCall, kCheckExactness);
}

//  R0: receiver
//  R9: ICData
//  R8: Function
//  LR: return address
void StubCodeCompiler::GenerateTwoArgsOptimizedCheckInlineCacheStub() {
  GenerateNArgsCheckInlineCacheStub(
      2, kInlineCacheMissHandlerTwoArgsRuntimeEntry, Token::kILLEGAL,
      kOptimized, kInstanceCall, kIgnoreExactness);
}

//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateZeroArgsUnoptimizedStaticCallStub() {
  GenerateRecordEntryPoint(assembler);
  GenerateUsageCounterIncrement(/* scratch */ R8);
#if defined(DEBUG)
  {
    Label ok;
    // Check that the IC data array has NumArgsTested() == 0.
    // 'NumArgsTested' is stored in the least significant bits of 'state_bits'.
    __ ldr(R8, FieldAddress(R9, target::ICData::state_bits_offset()));
    ASSERT(target::ICData::NumArgsTestedShift() == 0);  // No shift needed.
    __ and_(R8, R8, Operand(target::ICData::NumArgsTestedMask()));
    __ CompareImmediate(R8, 0);
    __ b(&ok, EQ);
    __ Stop("Incorrect IC data for unoptimized static call");
    __ Bind(&ok);
  }
#endif  // DEBUG

#if !defined(PRODUCT)
  // Check single stepping.
  Label stepping, done_stepping;
  __ ldrb(R8, Address(THR, target::Thread::single_step_offset()));
  __ CompareImmediate(R8, 0);
  __ b(&stepping, NE);
  __ Bind(&done_stepping);
#endif

  // R9: IC data object (preserved).
  __ ldr(R8, FieldAddress(R9, target::ICData::entries_offset()));
  // R8: ic_data_array with entries: target functions and count.
  __ AddImmediate(R8, target::Array::data_offset() - kHeapObjectTag);
  // R8: points directly to the first ic data array element.
  const intptr_t target_offset =
      target::ICData::TargetIndexFor(0) * target::kWordSize;
  const intptr_t count_offset =
      target::ICData::CountIndexFor(0) * target::kWordSize;

  if (FLAG_optimization_counter_threshold >= 0) {
    // Increment count for this call, ignore overflow.
    __ LoadFromOffset(R1, R8, count_offset);
    __ adds(R1, R1, Operand(target::ToRawSmi(1)));
    __ StoreIntoSmiField(Address(R8, count_offset), R1);
  }

  // Load arguments descriptor into R4.
  __ ldr(ARGS_DESC_REG,
         FieldAddress(R9, target::CallSiteData::arguments_descriptor_offset()));

  // Get function and call it, if possible.
  __ LoadFromOffset(FUNCTION_REG, R8, target_offset);
  __ ldr(CODE_REG, FieldAddress(FUNCTION_REG, target::Function::code_offset()));

  __ Branch(Address(FUNCTION_REG, R3));

#if !defined(PRODUCT)
  __ Bind(&stepping);
  __ EnterStubFrame();
  __ SmiTag(R3);                       // Entry-point is not Smi.
  __ PushList((1 << R9) | (1 << R3));  // Preserve IC data and entry-point.
  __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
  __ PopList((1 << R9) | (1 << R3));
  __ SmiUntag(R3);
  __ RestoreCodePointer();
  __ LeaveStubFrame();
  __ b(&done_stepping);
#endif
}

//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateOneArgUnoptimizedStaticCallStub() {
  GenerateUsageCounterIncrement(/* scratch */ R8);
  GenerateNArgsCheckInlineCacheStub(1, kStaticCallMissHandlerOneArgRuntimeEntry,
                                    Token::kILLEGAL, kUnoptimized, kStaticCall,
                                    kIgnoreExactness);
}

//  R9: ICData
//  LR: return address
void StubCodeCompiler::GenerateTwoArgsUnoptimizedStaticCallStub() {
  GenerateUsageCounterIncrement(/* scratch */ R8);
  GenerateNArgsCheckInlineCacheStub(
      2, kStaticCallMissHandlerTwoArgsRuntimeEntry, Token::kILLEGAL,
      kUnoptimized, kStaticCall, kIgnoreExactness);
}

// Stub for compiling a function and jumping to the compiled code.
// ARGS_DESC_REG: Arguments descriptor.
// FUNCTION_REG: Function.
void StubCodeCompiler::GenerateLazyCompileStub() {
  __ EnterStubFrame();
  // Preserve arg desc, pass function.
  COMPILE_ASSERT(FUNCTION_REG < ARGS_DESC_REG);
  __ PushList((1 << FUNCTION_REG) | (1 << ARGS_DESC_REG));
  __ CallRuntime(kCompileFunctionRuntimeEntry, 1);
  __ PopList((1 << FUNCTION_REG) | (1 << ARGS_DESC_REG));
  __ LeaveStubFrame();

  __ ldr(CODE_REG, FieldAddress(FUNCTION_REG, target::Function::code_offset()));
  __ Branch(FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));
}

// Stub for interpreting a function call.
// R4: Arguments descriptor.
// R0: Function.
void StubCodeCompiler::GenerateInterpretCallStub() {
#if defined(DART_DYNAMIC_MODULES)

  __ EnterStubFrame();

#if defined(DEBUG)
  {
    Label ok;
    // Check that we are always entering from Dart code.
    __ LoadFromOffset(R8, THR, target::Thread::vm_tag_offset());
    __ CompareImmediate(R8, VMTag::kDartTagId);
    __ b(&ok, EQ);
    __ Stop("Not coming from Dart code.");
    __ Bind(&ok);
  }
#endif

  // Adjust arguments count for type arguments vector.
  __ LoadFieldFromOffset(R2, R4, target::ArgumentsDescriptor::count_offset());
  __ SmiUntag(R2);
  __ LoadFieldFromOffset(R1, R4,
                         target::ArgumentsDescriptor::type_args_len_offset());
  __ cmp(R1, Operand(0));
  __ AddImmediate(R2, R2, 1, NE);  // Include the type arguments.

  // Compute argv.
  __ mov(R3, Operand(R2, LSL, 2));
  __ add(R3, FP, Operand(R3));
  __ AddImmediate(R3,
                  target::frame_layout.param_end_from_fp * target::kWordSize);

  // Indicate decreasing memory addresses of arguments with negative argc.
  __ rsb(R2, R2, Operand(0));

  // Align frame before entering C++ world. Fifth argument passed on the stack.
  __ ReserveAlignedFrameSpace(1 * target::kWordSize);

  // Pass arguments in registers.
  // R0: Function.
  __ mov(R1, Operand(R4));  // Arguments descriptor.
  // R2: Negative argc.
  // R3: Argv.
  __ str(THR, Address(SP, 0));  // Fifth argument: Thread.

  // Save exit frame information to enable stack walking as we are about
  // to transition to Dart VM C++ code.
  __ StoreToOffset(FP, THR, target::Thread::top_exit_frame_info_offset());

  // Mark that the thread exited generated code through a runtime call.
  __ LoadImmediate(R5, target::Thread::exit_through_runtime_call());
  __ StoreToOffset(R5, THR, target::Thread::exit_through_ffi_offset());

  // Mark that the thread is executing VM code.
  __ LoadFromOffset(R5, THR,
                    target::Thread::interpret_call_entry_point_offset());
  __ StoreToOffset(R5, THR, target::Thread::vm_tag_offset());

  __ blx(R5);

  // Mark that the thread is executing Dart code.
  __ LoadImmediate(R2, VMTag::kDartTagId);
  __ StoreToOffset(R2, THR, target::Thread::vm_tag_offset());

  // Mark that the thread has not exited generated Dart code.
  __ LoadImmediate(R2, 0);
  __ StoreToOffset(R2, THR, target::Thread::exit_through_ffi_offset());

  // Reset exit frame information in Isolate's mutator thread structure.
  __ StoreToOffset(R2, THR, target::Thread::top_exit_frame_info_offset());

  __ LeaveStubFrame();
  __ Ret();

#else
  __ Stop("Not using Dart dynamic modules");
#endif  // defined(DART_DYNAMIC_MODULES)
}

// R9: Contains an ICData.
void StubCodeCompiler::GenerateICCallBreakpointStub() {
#if defined(PRODUCT)
  __ Stop("No debugging in PRODUCT mode");
#else
  __ EnterStubFrame();
  __ Push(R0);          // Preserve receiver.
  __ Push(R9);          // Preserve IC data.
  __ PushImmediate(0);  // Space for result.
  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
  __ Pop(CODE_REG);  // Original stub.
  __ Pop(R9);        // Restore IC data.
  __ Pop(R0);        // Restore receiver.
  __ LeaveStubFrame();
  __ Branch(FieldAddress(CODE_REG, target::Code::entry_point_offset()));
#endif  // defined(PRODUCT)
}

void StubCodeCompiler::GenerateUnoptStaticCallBreakpointStub() {
#if defined(PRODUCT)
  __ Stop("No debugging in PRODUCT mode");
#else
  __ EnterStubFrame();
  __ Push(R9);          // Preserve IC data.
  __ PushImmediate(0);  // Space for result.
  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
  __ Pop(CODE_REG);  // Original stub.
  __ Pop(R9);        // Restore IC data.
  __ LeaveStubFrame();
  __ Branch(FieldAddress(CODE_REG, target::Code::entry_point_offset()));
#endif  // defined(PRODUCT)
}

void StubCodeCompiler::GenerateRuntimeCallBreakpointStub() {
#if defined(PRODUCT)
  __ Stop("No debugging in PRODUCT mode");
#else
  __ EnterStubFrame();
  __ LoadImmediate(R0, 0);
  // Make room for result.
  __ PushList((1 << R0));
  __ CallRuntime(kBreakpointRuntimeHandlerRuntimeEntry, 0);
  __ PopList((1 << CODE_REG));
  __ LeaveStubFrame();
  __ Branch(FieldAddress(CODE_REG, target::Code::entry_point_offset()));
#endif  // defined(PRODUCT)
}

// Called only from unoptimized code. All relevant registers have been saved.
void StubCodeCompiler::GenerateDebugStepCheckStub() {
#if defined(PRODUCT)
  __ Stop("No debugging in PRODUCT mode");
#else
  // Check single stepping.
  Label stepping, done_stepping;
  __ ldrb(R1, Address(THR, target::Thread::single_step_offset()));
  __ CompareImmediate(R1, 0);
  __ b(&stepping, NE);
  __ Bind(&done_stepping);
  __ Ret();

  __ Bind(&stepping);
  __ EnterStubFrame();
  __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
  __ LeaveStubFrame();
  __ b(&done_stepping);
#endif  // defined(PRODUCT)
}

// Used to check class and type arguments. Arguments passed in registers:
//
// Inputs (all preserved, mostly from TypeTestABI struct):
//   - kSubtypeTestCacheReg: SubtypeTestCacheLayout
//   - kInstanceReg: instance to test against.
//   - kDstTypeReg: destination type (for n>=7).
//   - kInstantiatorTypeArgumentsReg: instantiator type arguments (for n>=3).
//   - kFunctionTypeArgumentsReg: function type arguments (for n>=4).
//   - LR: return address.
//
// Outputs (from TypeTestABI struct):
//   - kSubtypeTestCacheResultReg: the cached result, or null if not found.
void StubCodeCompiler::GenerateSubtypeNTestCacheStub(Assembler* assembler,
                                                     int n) {
  ASSERT(n >= 1);
  ASSERT(n <= SubtypeTestCache::kMaxInputs);
  // If we need the parent function type arguments for a closure, we also need
  // the delayed type arguments, so this case will never happen.
  ASSERT(n != 5);
  RegisterSet saved_registers;

  // Safe as the original value of TypeTestABI::kSubtypeTestCacheReg is only
  // used to initialize this register.
  const Register kCacheArrayReg = TypeTestABI::kSubtypeTestCacheReg;
  saved_registers.AddRegister(kCacheArrayReg);

  // CODE_REG is used only in JIT mode, and the dispatch table only exists in
  // AOT mode, so we can use the corresponding register for the mode we're not
  // in without having to preserve it.
  const Register kNullReg =
      FLAG_precompiled_mode ? CODE_REG : DISPATCH_TABLE_REG;
  __ LoadObject(kNullReg, NullObject());

  // Free up additional registers needed for checks in the loop. Initially
  // define them as kNoRegister so any unexpected uses are caught.
  Register kInstanceInstantiatorTypeArgumentsReg = kNoRegister;
  if (n >= 2) {
    kInstanceInstantiatorTypeArgumentsReg = PP;
    saved_registers.AddRegister(kInstanceInstantiatorTypeArgumentsReg);
  }
  Register kInstanceParentFunctionTypeArgumentsReg = kNoRegister;
  if (n >= 5) {
    // For this, we look at the pair of Registers we considered for kNullReg
    // and use the one that must be preserved instead.
    kInstanceParentFunctionTypeArgumentsReg =
        FLAG_precompiled_mode ? DISPATCH_TABLE_REG : CODE_REG;
    saved_registers.AddRegister(kInstanceParentFunctionTypeArgumentsReg);
  }
  Register kInstanceDelayedFunctionTypeArgumentsReg = kNoRegister;
  if (n >= 6) {
    // We retrieve all the needed fields from the instance during loop
    // initialization and store them in registers, so we don't need the value
    // of kInstanceReg during the loop and just need to save and restore it.
    // Thus, use kInstanceReg for the last field that can possibly be retrieved
    // from the instance.
    kInstanceDelayedFunctionTypeArgumentsReg = TypeTestABI::kInstanceReg;
    saved_registers.AddRegister(kInstanceDelayedFunctionTypeArgumentsReg);
  }

  // We'll replace these with actual registers if possible, but fall back to
  // the stack if register pressure is too great. The last two values are
  // used in every loop iteration, and so are more important to put in
  // registers if possible, whereas the first is used only when we go off
  // the end of the backing array (usually at most once per check).
  Register kCacheContentsSizeReg = kNoRegister;
  if (n < 5) {
    // Use the register we would have used for the parent function type args.
    kCacheContentsSizeReg =
        FLAG_precompiled_mode ? DISPATCH_TABLE_REG : CODE_REG;
    saved_registers.AddRegister(kCacheContentsSizeReg);
  }
  Register kProbeDistanceReg = kNoRegister;
  if (n < 6) {
    // Use the register we would have used for the delayed type args.
    kProbeDistanceReg = TypeTestABI::kInstanceReg;
    saved_registers.AddRegister(kProbeDistanceReg);
  }
  Register kCacheEntryEndReg = kNoRegister;
  if (n < 7) {
    // Use the destination type, as that is the last input that might be unused.
    kCacheEntryEndReg = TypeTestABI::kDstTypeReg;
    saved_registers.AddRegister(TypeTestABI::kDstTypeReg);
  }

  __ PushRegisters(saved_registers);

  Label not_found;
  GenerateSubtypeTestCacheSearch(
      assembler, n, kNullReg, kCacheArrayReg,
      STCInternalRegs::kInstanceCidOrSignatureReg,
      kInstanceInstantiatorTypeArgumentsReg,
      kInstanceParentFunctionTypeArgumentsReg,
      kInstanceDelayedFunctionTypeArgumentsReg, kCacheEntryEndReg,
      kCacheContentsSizeReg, kProbeDistanceReg,
      [&](Assembler* assembler, int n) {
        __ LoadCompressed(
            TypeTestABI::kSubtypeTestCacheResultReg,
            Address(kCacheArrayReg, target::kCompressedWordSize *
                                        target::SubtypeTestCache::kTestResult));
        __ PopRegisters(saved_registers);
        __ Ret();
      },
      [&](Assembler* assembler, int n) {
        __ MoveRegister(TypeTestABI::kSubtypeTestCacheResultReg, kNullReg);
        __ PopRegisters(saved_registers);
        __ Ret();
      });
}

// Return the current stack pointer address, used to do stack alignment checks.
void StubCodeCompiler::GenerateGetCStackPointerStub() {
  __ mov(R0, Operand(SP));
  __ Ret();
}

// Jump to a frame on the call stack.
// LR: return address.
// R0: program_counter.
// R1: stack_pointer.
// R2: frame_pointer.
// R3: thread.
// Does not return.
//
// Notice: We need to keep this in sync with `Simulator::JumpToFrame()`.
void StubCodeCompiler::GenerateJumpToFrameStub() {
  COMPILE_ASSERT(kExceptionObjectReg == R0);
  COMPILE_ASSERT(kStackTraceObjectReg == R1);
  COMPILE_ASSERT(IsAbiPreservedRegister(R4));
  COMPILE_ASSERT(IsAbiPreservedRegister(THR));
  __ mov(R4, Operand(R0));   // Program counter.
  __ mov(THR, Operand(R3));  // Thread.
  __ mov(FP, Operand(R2));   // Frame_pointer.
  __ mov(SP, Operand(R1));   // Set Stack pointer.
#if defined(USING_SHADOW_CALL_STACK)
#error Unimplemented
#endif

  // Set the tag.
  __ LoadImmediate(R2, VMTag::kDartTagId);
  __ StoreToOffset(R2, THR, target::Thread::vm_tag_offset());
  // Clear top exit frame.
  __ LoadImmediate(R2, 0);
  __ StoreToOffset(R2, THR, target::Thread::top_exit_frame_info_offset());
  // Restore the pool pointer.
  __ RestoreCodePointer();
  if (FLAG_precompiled_mode) {
    __ SetupGlobalPoolAndDispatchTable();
    __ set_constant_pool_allowed(true);
  } else {
    __ LoadPoolPointer();
  }
  __ bx(R4);  // Jump to continuation point.
}

// Run an exception handler.  Execution comes from JumpToFrame
// stub or from the simulator.
//
// The arguments are stored in the Thread object.
// Does not return.
static void GenerateRunExceptionHandler(Assembler* assembler,
                                        bool unbox_exception) {
  WRITES_RETURN_ADDRESS_TO_LR(
      __ LoadFromOffset(LR, THR, target::Thread::resume_pc_offset()));

  word offset_from_thread = 0;
  bool ok = target::CanLoadFromThread(NullObject(), &offset_from_thread);
  ASSERT(ok);
  __ LoadFromOffset(R2, THR, offset_from_thread);

  // Exception object.
  __ LoadFromOffset(R0, THR, target::Thread::active_exception_offset());
  __ StoreToOffset(R2, THR, target::Thread::active_exception_offset());
  if (unbox_exception) {
    compiler::Label not_smi, done;
    __ BranchIfNotSmi(R0, &not_smi);
    __ SmiUntag(R0);
    __ Jump(&done);
    __ Bind(&not_smi);
    __ ldr(R0, FieldAddress(R0, Mint::value_offset()));
    __ Bind(&done);
  }

  // StackTrace object.
  __ LoadFromOffset(R1, THR, target::Thread::active_stacktrace_offset());
  __ StoreToOffset(R2, THR, target::Thread::active_stacktrace_offset());

  READS_RETURN_ADDRESS_FROM_LR(
      __ bx(LR));  // Jump to the exception handler code.
}

void StubCodeCompiler::GenerateRunExceptionHandlerStub() {
  GenerateRunExceptionHandler(assembler, false);
}

void StubCodeCompiler::GenerateRunExceptionHandlerUnboxStub() {
  GenerateRunExceptionHandler(assembler, true);
}

// Deoptimize a frame on the call stack before rewinding.
// The arguments are stored in the Thread object.
// No result.
void StubCodeCompiler::GenerateDeoptForRewindStub() {
  // Push zap value instead of CODE_REG.
  __ LoadImmediate(IP, kZapCodeReg);
  __ Push(IP);

  // Load the deopt pc into LR.
  WRITES_RETURN_ADDRESS_TO_LR(
      __ LoadFromOffset(LR, THR, target::Thread::resume_pc_offset()));
  GenerateDeoptimizationSequence(assembler, kEagerDeopt);

  // After we have deoptimized, jump to the correct frame.
  __ EnterStubFrame();
  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
  __ LeaveStubFrame();
  __ bkpt(0);
}

// Calls to the runtime to optimize the given function.
// R8: function to be reoptimized.
// ARGS_DESC_REG: argument descriptor (preserved).
void StubCodeCompiler::GenerateOptimizeFunctionStub() {
  __ ldr(CODE_REG, Address(THR, target::Thread::optimize_stub_offset()));
  __ EnterStubFrame();
  __ Push(ARGS_DESC_REG);
  __ LoadImmediate(IP, 0);
  __ Push(IP);  // Setup space on stack for return value.
  __ Push(R8);
  __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry, 1);
  __ Pop(R0);             // Discard argument.
  __ Pop(FUNCTION_REG);   // Get Function object
  __ Pop(ARGS_DESC_REG);  // Restore argument descriptor.
  __ LeaveStubFrame();
  __ ldr(CODE_REG, FieldAddress(FUNCTION_REG, target::Function::code_offset()));
  __ Branch(FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));
  __ bkpt(0);
}

// Does identical check (object references are equal or not equal) with special
// checks for boxed numbers.
// LR: return address.
// Return Zero condition flag set if equal.
// Note: A Mint cannot contain a value that would fit in Smi.
static void GenerateIdenticalWithNumberCheckStub(Assembler* assembler,
                                                 const Register left,
                                                 const Register right,
                                                 const Register temp) {
  Label reference_compare, done, check_mint;
  // If any of the arguments is Smi do reference compare.
  __ tst(left, Operand(kSmiTagMask));
  __ b(&reference_compare, EQ);
  __ tst(right, Operand(kSmiTagMask));
  __ b(&reference_compare, EQ);

  // Value compare for two doubles.
  __ CompareClassId(left, kDoubleCid, temp);
  __ b(&check_mint, NE);
  __ CompareClassId(right, kDoubleCid, temp);
  __ b(&done, NE);

  // Double values bitwise compare.
  __ ldr(temp, FieldAddress(left, target::Double::value_offset() +
                                      0 * target::kWordSize));
  __ ldr(IP, FieldAddress(right, target::Double::value_offset() +
                                     0 * target::kWordSize));
  __ cmp(temp, Operand(IP));
  __ b(&done, NE);
  __ ldr(temp, FieldAddress(left, target::Double::value_offset() +
                                      1 * target::kWordSize));
  __ ldr(IP, FieldAddress(right, target::Double::value_offset() +
                                     1 * target::kWordSize));
  __ cmp(temp, Operand(IP));
  __ b(&done);

  __ Bind(&check_mint);
  __ CompareClassId(left, kMintCid, temp);
  __ b(&reference_compare, NE);
  __ CompareClassId(right, kMintCid, temp);
  __ b(&done, NE);
  __ ldr(temp, FieldAddress(
                   left, target::Mint::value_offset() + 0 * target::kWordSize));
  __ ldr(IP, FieldAddress(
                 right, target::Mint::value_offset() + 0 * target::kWordSize));
  __ cmp(temp, Operand(IP));
  __ b(&done, NE);
  __ ldr(temp, FieldAddress(
                   left, target::Mint::value_offset() + 1 * target::kWordSize));
  __ ldr(IP, FieldAddress(
                 right, target::Mint::value_offset() + 1 * target::kWordSize));
  __ cmp(temp, Operand(IP));
  __ b(&done);

  __ Bind(&reference_compare);
  __ cmp(left, Operand(right));
  __ Bind(&done);
}

// Called only from unoptimized code. All relevant registers have been saved.
// LR: return address.
// SP + 4: left operand.
// SP + 0: right operand.
// Return Zero condition flag set if equal.
void StubCodeCompiler::GenerateUnoptimizedIdenticalWithNumberCheckStub() {
#if !defined(PRODUCT)
  // Check single stepping.
  Label stepping, done_stepping;
  __ ldrb(R1, Address(THR, target::Thread::single_step_offset()));
  __ CompareImmediate(R1, 0);
  __ b(&stepping, NE);
  __ Bind(&done_stepping);
#endif

  const Register temp = R2;
  const Register left = R1;
  const Register right = R0;
  __ ldr(left, Address(SP, 1 * target::kWordSize));
  __ ldr(right, Address(SP, 0 * target::kWordSize));
  GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
  __ Ret();

#if !defined(PRODUCT)
  __ Bind(&stepping);
  __ EnterStubFrame();
  __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
  __ RestoreCodePointer();
  __ LeaveStubFrame();
  __ b(&done_stepping);
#endif
}

// Called from optimized code only.
// LR: return address.
// SP + 4: left operand.
// SP + 0: right operand.
// Return Zero condition flag set if equal.
void StubCodeCompiler::GenerateOptimizedIdenticalWithNumberCheckStub() {
  const Register temp = R2;
  const Register left = R1;
  const Register right = R0;
  __ ldr(left, Address(SP, 1 * target::kWordSize));
  __ ldr(right, Address(SP, 0 * target::kWordSize));
  GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
  __ Ret();
}

// Called from megamorphic calls.
//  R0: receiver
//  IC_DATA_REG: MegamorphicCache (preserved)
// Passed to target:
//  FUNCTION_REG: target function
//  ARGS_DESC_REG: arguments descriptor
//  CODE_REG: target Code
void StubCodeCompiler::GenerateMegamorphicCallStub() {
  __ LoadTaggedClassIdMayBeSmi(R8, R0);
  // R8: receiver cid as Smi.
  __ ldr(R1,
         FieldAddress(IC_DATA_REG, target::MegamorphicCache::mask_offset()));
  __ ldr(R2,
         FieldAddress(IC_DATA_REG, target::MegamorphicCache::buckets_offset()));
  // R1: mask as a smi - load first to support insertion w/o stopping Dart code.
  // R2: cache buckets array.

  // Compute the table index.
  ASSERT(target::MegamorphicCache::kSpreadFactor == 7);
  // Use reverse subtract to multiply with 7 == 8 - 1.
  __ rsb(R3, R8, Operand(R8, LSL, 3));
  // R3: probe.
  Label loop;
  __ Bind(&loop);
  __ and_(R3, R3, Operand(R1));

  const intptr_t base = target::Array::data_offset();
  // R3 is smi tagged, but table entries are two words, so LSL 2.
  Label probe_failed;
  __ add(IP, R2, Operand(R3, LSL, 2));
  __ ldr(R6, FieldAddress(IP, base));
  __ cmp(R6, Operand(R8));
  __ b(&probe_failed, NE);

  Label load_target;
  __ Bind(&load_target);
  // Call the target found in the cache.  For a class id match, this is a
  // proper target for the given name and arguments descriptor.  If the
  // illegal class id was found, the target is a cache miss handler that can
  // be invoked as a normal Dart function.
  __ ldr(FUNCTION_REG, FieldAddress(IP, base + target::kWordSize));
  if (!FLAG_precompiled_mode) {
    __ ldr(CODE_REG,
           FieldAddress(FUNCTION_REG, target::Function::code_offset()));
  }
  __ ldr(ARGS_DESC_REG,
         FieldAddress(IC_DATA_REG,
                      target::CallSiteData::arguments_descriptor_offset()));
  __ Branch(FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));

  // Probe failed, check if it is a miss.
  __ Bind(&probe_failed);
  ASSERT(kIllegalCid == 0);
  __ tst(R6, Operand(R6));
  Label miss;
  __ b(&miss, EQ);  // branch if miss.

  // Try next entry in the table.
  __ AddImmediate(R3, target::ToRawSmi(1));
  __ b(&loop);

  __ Bind(&miss);
  GenerateSwitchableCallMissStub();
}

void StubCodeCompiler::GenerateICCallThroughCodeStub() {
  Label loop, found, miss;
  __ ldr(R8, FieldAddress(IC_DATA_REG, target::ICData::entries_offset()));
  __ ldr(R4, FieldAddress(IC_DATA_REG,
                          target::CallSiteData::arguments_descriptor_offset()));
  __ AddImmediate(R8, target::Array::data_offset() - kHeapObjectTag);
  // R8: first IC entry
  __ LoadTaggedClassIdMayBeSmi(R1, R0);
  // R1: receiver cid as Smi

  __ Bind(&loop);
  __ ldr(R2, Address(R8, 0));
  __ cmp(R1, Operand(R2));
  __ b(&found, EQ);
  __ CompareImmediate(R2, target::ToRawSmi(kIllegalCid));
  __ b(&miss, EQ);

  const intptr_t entry_length =
      target::ICData::TestEntryLengthFor(1, /*exactness_check=*/false) *
      target::kWordSize;
  __ AddImmediate(R8, entry_length);  // Next entry.
  __ b(&loop);

  __ Bind(&found);
  if (FLAG_precompiled_mode) {
    const intptr_t entry_offset =
        target::ICData::EntryPointIndexFor(1) * target::kWordSize;
    __ LoadCompressed(FUNCTION_REG, Address(R8, entry_offset));
    __ Branch(
        FieldAddress(FUNCTION_REG, target::Function::entry_point_offset()));
  } else {
    const intptr_t code_offset =
        target::ICData::CodeIndexFor(1) * target::kWordSize;
    __ LoadCompressed(CODE_REG, Address(R8, code_offset));
    __ Branch(FieldAddress(CODE_REG, target::Code::entry_point_offset()));
  }

  __ Bind(&miss);
  __ Branch(Address(THR, target::Thread::switchable_call_miss_entry_offset()));
}

// Implement the monomorphic entry check for call-sites where the receiver
// might be a Smi.
//
//   R0: receiver
//   R9: MonomorphicSmiableCall object
//
//   R2, R3: clobbered
void StubCodeCompiler::GenerateMonomorphicSmiableCheckStub() {
  __ LoadClassIdMayBeSmi(IP, R0);

  // entrypoint_ should come right after expected_cid_
  ASSERT(target::MonomorphicSmiableCall::entrypoint_offset() ==
         target::MonomorphicSmiableCall::expected_cid_offset() +
             target::kWordSize);

  // Note: this stub is only used in AOT mode, hence the direct (bare) call.
  // Simultaneously load the expected cid into R2 and the entrypoint into R3.
  __ ldrd(
      R2, R3, R9,
      target::MonomorphicSmiableCall::expected_cid_offset() - kHeapObjectTag);
  __ cmp(R2, Operand(IP));
  __ Branch(Address(THR, target::Thread::switchable_call_miss_entry_offset()),
            NE);
  __ bx(R3);
}

static void CallSwitchableCallMissRuntimeEntry(Assembler* assembler,
                                               Register receiver_reg) {
  __ LoadImmediate(IP, 0);
  __ Push(IP);            // Result slot
  __ Push(IP);            // Arg0: stub out
  __ Push(receiver_reg);  // Arg1: Receiver
  __ CallRuntime(kSwitchableCallMissRuntimeEntry, 2);
  __ Pop(R0);        // Get the receiver
  __ Pop(CODE_REG);  // result = stub
  __ Pop(R9);        // result = IC
}

// Called from switchable IC calls.
//  R0: receiver
void StubCodeCompiler::GenerateSwitchableCallMissStub() {
  __ ldr(CODE_REG,
         Address(THR, target::Thread::switchable_call_miss_stub_offset()));
  __ EnterStubFrame();
  CallSwitchableCallMissRuntimeEntry(assembler, /*receiver_reg=*/R0);
  __ LeaveStubFrame();

  __ Branch(FieldAddress(
      CODE_REG, target::Code::entry_point_offset(CodeEntryKind::kNormal)));
}

// Called from switchable IC calls.
//  R0: receiver
//  R9: SingleTargetCache
// Passed to target:
//  CODE_REG: target Code object
void StubCodeCompiler::GenerateSingleTargetCallStub() {
  Label miss;
  __ LoadClassIdMayBeSmi(R1, R0);
  __ ldrh(R2,
          FieldAddress(R9, target::SingleTargetCache::lower_limit_offset()));
  __ ldrh(R3,
          FieldAddress(R9, target::SingleTargetCache::upper_limit_offset()));

  __ cmp(R1, Operand(R2));
  __ b(&miss, LT);
  __ cmp(R1, Operand(R3));
  __ b(&miss, GT);

  __ ldr(CODE_REG,
         FieldAddress(R9, target::SingleTargetCache::target_offset()));
  __ Branch(FieldAddress(R9, target::SingleTargetCache::entry_point_offset()));

  __ Bind(&miss);
  __ EnterStubFrame();
  CallSwitchableCallMissRuntimeEntry(assembler, /*receiver_reg=*/R0);
  __ LeaveStubFrame();

  __ Branch(FieldAddress(
      CODE_REG, target::Code::entry_point_offset(CodeEntryKind::kMonomorphic)));
}

static int GetScaleFactor(intptr_t size) {
  switch (size) {
    case 1:
      return 0;
    case 2:
      return 1;
    case 4:
      return 2;
    case 8:
      return 3;
    case 16:
      return 4;
  }
  UNREACHABLE();
  return -1;
}

void StubCodeCompiler::GenerateAllocateTypedDataArrayStub(intptr_t cid) {
  const intptr_t element_size = TypedDataElementSizeInBytes(cid);
  const intptr_t max_len = TypedDataMaxNewSpaceElements(cid);
  const intptr_t scale_shift = GetScaleFactor(element_size);

  COMPILE_ASSERT(AllocateTypedDataArrayABI::kLengthReg == R4);
  COMPILE_ASSERT(AllocateTypedDataArrayABI::kResultReg == R0);

  if (!FLAG_use_slow_path && FLAG_inline_alloc) {
    Label call_runtime;
    NOT_IN_PRODUCT(__ MaybeTraceAllocation(cid, &call_runtime, R2));
    __ mov(R2, Operand(AllocateTypedDataArrayABI::kLengthReg));
    /* Check that length is a positive Smi. */
    /* R2: requested array length argument. */
    __ tst(R2, Operand(kSmiTagMask));
    __ b(&call_runtime, NE);
    __ SmiUntag(R2);
    /* Check for length >= 0 && length <= max_len. */
    /* R2: untagged array length. */
    __ CompareImmediate(R2, max_len);
    __ b(&call_runtime, HI);
    __ mov(R2, Operand(R2, LSL, scale_shift));
    const intptr_t fixed_size_plus_alignment_padding =
        target::TypedData::HeaderSize() +
        target::ObjectAlignment::kObjectAlignment - 1;
    __ AddImmediate(R2, fixed_size_plus_alignment_padding);
    __ bic(R2, R2, Operand(target::ObjectAlignment::kObjectAlignment - 1));
    __ ldr(R0, Address(THR, target::Thread::top_offset()));

    /* R2: allocation size. */
    __ adds(R1, R0, Operand(R2));
    __ b(&call_runtime, CS); /* Fail on unsigned overflow. */

    /* Check if the allocation fits into the remaining space. */
    /* R0: potential new object start. */
    /* R1: potential next object start. */
    /* R2: allocation size. */
    __ ldr(IP, Address(THR, target::Thread::end_offset()));
    __ cmp(R1, Operand(IP));
    __ b(&call_runtime, CS);
    __ CheckAllocationCanary(R0);

    __ str(R1, Address(THR, target::Thread::top_offset()));
    __ AddImmediate(R0, kHeapObjectTag);
    /* Initialize the tags. */
    /* R0: new object start as a tagged pointer. */
    /* R1: new object end address. */
    /* R2: allocation size. */
    {
      __ CompareImmediate(R2, target::UntaggedObject::kSizeTagMaxSizeTag);
      __ mov(R3,
             Operand(R2, LSL,
                     target::UntaggedObject::kTagBitsSizeTagPos -
                         target::ObjectAlignment::kObjectAlignmentLog2),
             LS);
      __ mov(R3, Operand(0), HI);

      /* Get the class index and insert it into the tags. */
      uword tags =
          target::MakeTagWordForNewSpaceObject(cid, /*instance_size=*/0);
      __ LoadImmediate(TMP, tags);
      __ orr(R3, R3, Operand(TMP));
      __ InitializeHeader(R3, R0);
    }
    /* Set the length field. */
    /* R0: new object start as a tagged pointer. */
    /* R1: new object end address. */
    /* R2: allocation size. */
    __ mov(R3,
           Operand(AllocateTypedDataArrayABI::kLengthReg)); /* Array length. */
    __ StoreIntoObjectNoBarrier(
        R0, FieldAddress(R0, target::TypedDataBase::length_offset()), R3);
    /* Initialize all array elements to 0. */
    /* R0: new object start as a tagged pointer. */
    /* R1: new object end address. */
    /* R2: allocation size. */
    /* R3: iterator which initially points to the start of the variable */
    /* R8, R9: zero. */
    /* data area to be initialized. */
    __ LoadImmediate(R8, 0);
    __ mov(R9, Operand(R8));
    __ AddImmediate(R3, R0, target::TypedData::HeaderSize() - 1);
    __ StoreInternalPointer(
        R0, FieldAddress(R0, target::PointerBase::data_offset()), R3);
    Label init_loop;
    __ Bind(&init_loop);
    __ AddImmediate(R3, 2 * target::kWordSize);
    __ cmp(R3, Operand(R1));
    __ strd(R8, R9, R3, -2 * target::kWordSize, LS);
    __ b(&init_loop, CC);
    __ str(R8, Address(R3, -2 * target::kWordSize), HI);
    __ WriteAllocationCanary(R1);  // Fix overshoot.

    __ Ret();

    __ Bind(&call_runtime);
  }

  __ EnterStubFrame();
  __ PushObject(Object::null_object());            // Make room for the result.
  __ PushImmediate(target::ToRawSmi(cid));         // Cid
  __ Push(AllocateTypedDataArrayABI::kLengthReg);  // Array length
  __ CallRuntime(kAllocateTypedDataRuntimeEntry, 2);
  __ Drop(2);  // Drop arguments.
  __ Pop(AllocateTypedDataArrayABI::kResultReg);
  __ LeaveStubFrame();
  __ Ret();
}

}  // namespace compiler

}  // namespace dart

#endif  // defined(TARGET_ARCH_ARM)