macro-assembler-arm.h

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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef V8_ARM_MACRO_ASSEMBLER_ARM_H_
#define V8_ARM_MACRO_ASSEMBLER_ARM_H_
 
#include "src/assembler.h"
#include "src/bailout-reason.h"
#include "src/frames.h"
#include "src/globals.h"
 
namespace v8 {
namespace internal {
 
// ----------------------------------------------------------------------------
// Static helper functions
 
// Generate a MemOperand for loading a field from an object.
inline MemOperand FieldMemOperand(Register object, int offset) {
  return MemOperand(object, offset - kHeapObjectTag);
}
 
 
// Give alias names to registers
const Register cp = { kRegister_r7_Code };  // JavaScript context pointer.
const Register pp = { kRegister_r8_Code };  // Constant pool pointer.
const Register kRootRegister = { kRegister_r10_Code };  // Roots array pointer.
 
// Flags used for AllocateHeapNumber
enum TaggingMode {
  // Tag the result.
  TAG_RESULT,
  // Don't tag
  DONT_TAG_RESULT
};
 
 
enum RememberedSetAction { EMIT_REMEMBERED_SET, OMIT_REMEMBERED_SET };
enum SmiCheck { INLINE_SMI_CHECK, OMIT_SMI_CHECK };
enum PointersToHereCheck {
  kPointersToHereMaybeInteresting,
  kPointersToHereAreAlwaysInteresting
};
enum LinkRegisterStatus { kLRHasNotBeenSaved, kLRHasBeenSaved };
 
 
Register GetRegisterThatIsNotOneOf(Register reg1,
                                   Register reg2 = no_reg,
                                   Register reg3 = no_reg,
                                   Register reg4 = no_reg,
                                   Register reg5 = no_reg,
                                   Register reg6 = no_reg);
 
 
#ifdef DEBUG
bool AreAliased(Register reg1,
                Register reg2,
                Register reg3 = no_reg,
                Register reg4 = no_reg,
                Register reg5 = no_reg,
                Register reg6 = no_reg,
                Register reg7 = no_reg,
                Register reg8 = no_reg);
#endif
 
 
enum TargetAddressStorageMode {
  CAN_INLINE_TARGET_ADDRESS,
  NEVER_INLINE_TARGET_ADDRESS
};
 
// MacroAssembler implements a collection of frequently used macros.
class MacroAssembler: public Assembler {
 public:
  // The isolate parameter can be NULL if the macro assembler should
  // not use isolate-dependent functionality. In this case, it's the
  // responsibility of the caller to never invoke such function on the
  // macro assembler.
  MacroAssembler(Isolate* isolate, void* buffer, int size);
 
 
  // Returns the size of a call in instructions. Note, the value returned is
  // only valid as long as no entries are added to the constant pool between
  // checking the call size and emitting the actual call.
  static int CallSize(Register target, Condition cond = al);
  int CallSize(Address target, RelocInfo::Mode rmode, Condition cond = al);
  int CallStubSize(CodeStub* stub,
                   TypeFeedbackId ast_id = TypeFeedbackId::None(),
                   Condition cond = al);
  static int CallSizeNotPredictableCodeSize(Isolate* isolate,
                                            Address target,
                                            RelocInfo::Mode rmode,
                                            Condition cond = al);
 
  // Jump, Call, and Ret pseudo instructions implementing inter-working.
  void Jump(Register target, Condition cond = al);
  void Jump(Address target, RelocInfo::Mode rmode, Condition cond = al);
  void Jump(Handle<Code> code, RelocInfo::Mode rmode, Condition cond = al);
  void Call(Register target, Condition cond = al);
  void Call(Address target, RelocInfo::Mode rmode,
            Condition cond = al,
            TargetAddressStorageMode mode = CAN_INLINE_TARGET_ADDRESS);
  int CallSize(Handle<Code> code,
               RelocInfo::Mode rmode = RelocInfo::CODE_TARGET,
               TypeFeedbackId ast_id = TypeFeedbackId::None(),
               Condition cond = al);
  void Call(Handle<Code> code,
            RelocInfo::Mode rmode = RelocInfo::CODE_TARGET,
            TypeFeedbackId ast_id = TypeFeedbackId::None(),
            Condition cond = al,
            TargetAddressStorageMode mode = CAN_INLINE_TARGET_ADDRESS);
  void Ret(Condition cond = al);
 
  // Emit code to discard a non-negative number of pointer-sized elements
  // from the stack, clobbering only the sp register.
  void Drop(int count, Condition cond = al);
 
  void Ret(int drop, Condition cond = al);
 
  // Swap two registers.  If the scratch register is omitted then a slightly
  // less efficient form using xor instead of mov is emitted.
  void Swap(Register reg1,
            Register reg2,
            Register scratch = no_reg,
            Condition cond = al);
 
  void Mls(Register dst, Register src1, Register src2, Register srcA,
           Condition cond = al);
  void And(Register dst, Register src1, const Operand& src2,
           Condition cond = al);
  void Ubfx(Register dst, Register src, int lsb, int width,
            Condition cond = al);
  void Sbfx(Register dst, Register src, int lsb, int width,
            Condition cond = al);
  // The scratch register is not used for ARMv7.
  // scratch can be the same register as src (in which case it is trashed), but
  // not the same as dst.
  void Bfi(Register dst,
           Register src,
           Register scratch,
           int lsb,
           int width,
           Condition cond = al);
  void Bfc(Register dst, Register src, int lsb, int width, Condition cond = al);
  void Usat(Register dst, int satpos, const Operand& src,
            Condition cond = al);
 
  void Call(Label* target);
  void Push(Register src) { push(src); }
  void Pop(Register dst) { pop(dst); }
 
  // Register move. May do nothing if the registers are identical.
  void Move(Register dst, Handle<Object> value);
  void Move(Register dst, Register src, Condition cond = al);
  void Move(Register dst, const Operand& src, SBit sbit = LeaveCC,
            Condition cond = al) {
    if (!src.is_reg() || !src.rm().is(dst) || sbit != LeaveCC) {
      mov(dst, src, sbit, cond);
    }
  }
  void Move(DwVfpRegister dst, DwVfpRegister src);
 
  void Load(Register dst, const MemOperand& src, Representation r);
  void Store(Register src, const MemOperand& dst, Representation r);
 
  // Load an object from the root table.
  void LoadRoot(Register destination,
                Heap::RootListIndex index,
                Condition cond = al);
  // Store an object to the root table.
  void StoreRoot(Register source,
                 Heap::RootListIndex index,
                 Condition cond = al);
 
  // ---------------------------------------------------------------------------
  // GC Support
 
  void IncrementalMarkingRecordWriteHelper(Register object,
                                           Register value,
                                           Register address);
 
  enum RememberedSetFinalAction {
    kReturnAtEnd,
    kFallThroughAtEnd
  };
 
  // Record in the remembered set the fact that we have a pointer to new space
  // at the address pointed to by the addr register.  Only works if addr is not
  // in new space.
  void RememberedSetHelper(Register object,  // Used for debug code.
                           Register addr,
                           Register scratch,
                           SaveFPRegsMode save_fp,
                           RememberedSetFinalAction and_then);
 
  void CheckPageFlag(Register object,
                     Register scratch,
                     int mask,
                     Condition cc,
                     Label* condition_met);
 
  void CheckMapDeprecated(Handle<Map> map,
                          Register scratch,
                          Label* if_deprecated);
 
  // Check if object is in new space.  Jumps if the object is not in new space.
  // The register scratch can be object itself, but scratch will be clobbered.
  void JumpIfNotInNewSpace(Register object,
                           Register scratch,
                           Label* branch) {
    InNewSpace(object, scratch, ne, branch);
  }
 
  // Check if object is in new space.  Jumps if the object is in new space.
  // The register scratch can be object itself, but it will be clobbered.
  void JumpIfInNewSpace(Register object,
                        Register scratch,
                        Label* branch) {
    InNewSpace(object, scratch, eq, branch);
  }
 
  // Check if an object has a given incremental marking color.
  void HasColor(Register object,
                Register scratch0,
                Register scratch1,
                Label* has_color,
                int first_bit,
                int second_bit);
 
  void JumpIfBlack(Register object,
                   Register scratch0,
                   Register scratch1,
                   Label* on_black);
 
  // Checks the color of an object.  If the object is already grey or black
  // then we just fall through, since it is already live.  If it is white and
  // we can determine that it doesn't need to be scanned, then we just mark it
  // black and fall through.  For the rest we jump to the label so the
  // incremental marker can fix its assumptions.
  void EnsureNotWhite(Register object,
                      Register scratch1,
                      Register scratch2,
                      Register scratch3,
                      Label* object_is_white_and_not_data);
 
  // Detects conservatively whether an object is data-only, i.e. it does need to
  // be scanned by the garbage collector.
  void JumpIfDataObject(Register value,
                        Register scratch,
                        Label* not_data_object);
 
  // Notify the garbage collector that we wrote a pointer into an object.
  // |object| is the object being stored into, |value| is the object being
  // stored.  value and scratch registers are clobbered by the operation.
  // The offset is the offset from the start of the object, not the offset from
  // the tagged HeapObject pointer.  For use with FieldOperand(reg, off).
  void RecordWriteField(
      Register object,
      int offset,
      Register value,
      Register scratch,
      LinkRegisterStatus lr_status,
      SaveFPRegsMode save_fp,
      RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
      SmiCheck smi_check = INLINE_SMI_CHECK,
      PointersToHereCheck pointers_to_here_check_for_value =
          kPointersToHereMaybeInteresting);
 
  // As above, but the offset has the tag presubtracted.  For use with
  // MemOperand(reg, off).
  inline void RecordWriteContextSlot(
      Register context,
      int offset,
      Register value,
      Register scratch,
      LinkRegisterStatus lr_status,
      SaveFPRegsMode save_fp,
      RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
      SmiCheck smi_check = INLINE_SMI_CHECK,
      PointersToHereCheck pointers_to_here_check_for_value =
          kPointersToHereMaybeInteresting) {
    RecordWriteField(context,
                     offset + kHeapObjectTag,
                     value,
                     scratch,
                     lr_status,
                     save_fp,
                     remembered_set_action,
                     smi_check,
                     pointers_to_here_check_for_value);
  }
 
  void RecordWriteForMap(
      Register object,
      Register map,
      Register dst,
      LinkRegisterStatus lr_status,
      SaveFPRegsMode save_fp);
 
  // For a given |object| notify the garbage collector that the slot |address|
  // has been written.  |value| is the object being stored. The value and
  // address registers are clobbered by the operation.
  void RecordWrite(
      Register object,
      Register address,
      Register value,
      LinkRegisterStatus lr_status,
      SaveFPRegsMode save_fp,
      RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
      SmiCheck smi_check = INLINE_SMI_CHECK,
      PointersToHereCheck pointers_to_here_check_for_value =
          kPointersToHereMaybeInteresting);
 
  // Push a handle.
  void Push(Handle<Object> handle);
  void Push(Smi* smi) { Push(Handle<Smi>(smi, isolate())); }
 
  // Push two registers.  Pushes leftmost register first (to highest address).
  void Push(Register src1, Register src2, Condition cond = al) {
    DCHECK(!src1.is(src2));
    if (src1.code() > src2.code()) {
      stm(db_w, sp, src1.bit() | src2.bit(), cond);
    } else {
      str(src1, MemOperand(sp, 4, NegPreIndex), cond);
      str(src2, MemOperand(sp, 4, NegPreIndex), cond);
    }
  }
 
  // Push three registers.  Pushes leftmost register first (to highest address).
  void Push(Register src1, Register src2, Register src3, Condition cond = al) {
    DCHECK(!src1.is(src2));
    DCHECK(!src2.is(src3));
    DCHECK(!src1.is(src3));
    if (src1.code() > src2.code()) {
      if (src2.code() > src3.code()) {
        stm(db_w, sp, src1.bit() | src2.bit() | src3.bit(), cond);
      } else {
        stm(db_w, sp, src1.bit() | src2.bit(), cond);
        str(src3, MemOperand(sp, 4, NegPreIndex), cond);
      }
    } else {
      str(src1, MemOperand(sp, 4, NegPreIndex), cond);
      Push(src2, src3, cond);
    }
  }
 
  // Push four registers.  Pushes leftmost register first (to highest address).
  void Push(Register src1,
            Register src2,
            Register src3,
            Register src4,
            Condition cond = al) {
    DCHECK(!src1.is(src2));
    DCHECK(!src2.is(src3));
    DCHECK(!src1.is(src3));
    DCHECK(!src1.is(src4));
    DCHECK(!src2.is(src4));
    DCHECK(!src3.is(src4));
    if (src1.code() > src2.code()) {
      if (src2.code() > src3.code()) {
        if (src3.code() > src4.code()) {
          stm(db_w,
              sp,
              src1.bit() | src2.bit() | src3.bit() | src4.bit(),
              cond);
        } else {
          stm(db_w, sp, src1.bit() | src2.bit() | src3.bit(), cond);
          str(src4, MemOperand(sp, 4, NegPreIndex), cond);
        }
      } else {
        stm(db_w, sp, src1.bit() | src2.bit(), cond);
        Push(src3, src4, cond);
      }
    } else {
      str(src1, MemOperand(sp, 4, NegPreIndex), cond);
      Push(src2, src3, src4, cond);
    }
  }
 
  // Pop two registers. Pops rightmost register first (from lower address).
  void Pop(Register src1, Register src2, Condition cond = al) {
    DCHECK(!src1.is(src2));
    if (src1.code() > src2.code()) {
      ldm(ia_w, sp, src1.bit() | src2.bit(), cond);
    } else {
      ldr(src2, MemOperand(sp, 4, PostIndex), cond);
      ldr(src1, MemOperand(sp, 4, PostIndex), cond);
    }
  }
 
  // Pop three registers.  Pops rightmost register first (from lower address).
  void Pop(Register src1, Register src2, Register src3, Condition cond = al) {
    DCHECK(!src1.is(src2));
    DCHECK(!src2.is(src3));
    DCHECK(!src1.is(src3));
    if (src1.code() > src2.code()) {
      if (src2.code() > src3.code()) {
        ldm(ia_w, sp, src1.bit() | src2.bit() | src3.bit(), cond);
      } else {
        ldr(src3, MemOperand(sp, 4, PostIndex), cond);
        ldm(ia_w, sp, src1.bit() | src2.bit(), cond);
      }
    } else {
      Pop(src2, src3, cond);
      ldr(src1, MemOperand(sp, 4, PostIndex), cond);
    }
  }
 
  // Pop four registers.  Pops rightmost register first (from lower address).
  void Pop(Register src1,
           Register src2,
           Register src3,
           Register src4,
           Condition cond = al) {
    DCHECK(!src1.is(src2));
    DCHECK(!src2.is(src3));
    DCHECK(!src1.is(src3));
    DCHECK(!src1.is(src4));
    DCHECK(!src2.is(src4));
    DCHECK(!src3.is(src4));
    if (src1.code() > src2.code()) {
      if (src2.code() > src3.code()) {
        if (src3.code() > src4.code()) {
          ldm(ia_w,
              sp,
              src1.bit() | src2.bit() | src3.bit() | src4.bit(),
              cond);
        } else {
          ldr(src4, MemOperand(sp, 4, PostIndex), cond);
          ldm(ia_w, sp, src1.bit() | src2.bit() | src3.bit(), cond);
        }
      } else {
        Pop(src3, src4, cond);
        ldm(ia_w, sp, src1.bit() | src2.bit(), cond);
      }
    } else {
      Pop(src2, src3, src4, cond);
      ldr(src1, MemOperand(sp, 4, PostIndex), cond);
    }
  }
 
  // Push a fixed frame, consisting of lr, fp, constant pool (if
  // FLAG_enable_ool_constant_pool), context and JS function / marker id if
  // marker_reg is a valid register.
  void PushFixedFrame(Register marker_reg = no_reg);
  void PopFixedFrame(Register marker_reg = no_reg);
 
  // Push and pop the registers that can hold pointers, as defined by the
  // RegList constant kSafepointSavedRegisters.
  void PushSafepointRegisters();
  void PopSafepointRegisters();
  // Store value in register src in the safepoint stack slot for
  // register dst.
  void StoreToSafepointRegisterSlot(Register src, Register dst);
  // Load the value of the src register from its safepoint stack slot
  // into register dst.
  void LoadFromSafepointRegisterSlot(Register dst, Register src);
 
  // Load two consecutive registers with two consecutive memory locations.
  void Ldrd(Register dst1,
            Register dst2,
            const MemOperand& src,
            Condition cond = al);
 
  // Store two consecutive registers to two consecutive memory locations.
  void Strd(Register src1,
            Register src2,
            const MemOperand& dst,
            Condition cond = al);
 
  // Ensure that FPSCR contains values needed by JavaScript.
  // We need the NaNModeControlBit to be sure that operations like
  // vadd and vsub generate the Canonical NaN (if a NaN must be generated).
  // In VFP3 it will be always the Canonical NaN.
  // In VFP2 it will be either the Canonical NaN or the negative version
  // of the Canonical NaN. It doesn't matter if we have two values. The aim
  // is to be sure to never generate the hole NaN.
  void VFPEnsureFPSCRState(Register scratch);
 
  // If the value is a NaN, canonicalize the value else, do nothing.
  void VFPCanonicalizeNaN(const DwVfpRegister dst,
                          const DwVfpRegister src,
                          const Condition cond = al);
  void VFPCanonicalizeNaN(const DwVfpRegister value,
                          const Condition cond = al) {
    VFPCanonicalizeNaN(value, value, cond);
  }
 
  // Compare double values and move the result to the normal condition flags.
  void VFPCompareAndSetFlags(const DwVfpRegister src1,
                             const DwVfpRegister src2,
                             const Condition cond = al);
  void VFPCompareAndSetFlags(const DwVfpRegister src1,
                             const double src2,
                             const Condition cond = al);
 
  // Compare double values and then load the fpscr flags to a register.
  void VFPCompareAndLoadFlags(const DwVfpRegister src1,
                              const DwVfpRegister src2,
                              const Register fpscr_flags,
                              const Condition cond = al);
  void VFPCompareAndLoadFlags(const DwVfpRegister src1,
                              const double src2,
                              const Register fpscr_flags,
                              const Condition cond = al);
 
  void Vmov(const DwVfpRegister dst,
            const double imm,
            const Register scratch = no_reg);
 
  void VmovHigh(Register dst, DwVfpRegister src);
  void VmovHigh(DwVfpRegister dst, Register src);
  void VmovLow(Register dst, DwVfpRegister src);
  void VmovLow(DwVfpRegister dst, Register src);
 
  // Loads the number from object into dst register.
  // If |object| is neither smi nor heap number, |not_number| is jumped to
  // with |object| still intact.
  void LoadNumber(Register object,
                  LowDwVfpRegister dst,
                  Register heap_number_map,
                  Register scratch,
                  Label* not_number);
 
  // Loads the number from object into double_dst in the double format.
  // Control will jump to not_int32 if the value cannot be exactly represented
  // by a 32-bit integer.
  // Floating point value in the 32-bit integer range that are not exact integer
  // won't be loaded.
  void LoadNumberAsInt32Double(Register object,
                               DwVfpRegister double_dst,
                               Register heap_number_map,
                               Register scratch,
                               LowDwVfpRegister double_scratch,
                               Label* not_int32);
 
  // Loads the number from object into dst as a 32-bit integer.
  // Control will jump to not_int32 if the object cannot be exactly represented
  // by a 32-bit integer.
  // Floating point value in the 32-bit integer range that are not exact integer
  // won't be converted.
  void LoadNumberAsInt32(Register object,
                         Register dst,
                         Register heap_number_map,
                         Register scratch,
                         DwVfpRegister double_scratch0,
                         LowDwVfpRegister double_scratch1,
                         Label* not_int32);
 
  // Generates function and stub prologue code.
  void StubPrologue();
  void Prologue(bool code_pre_aging);
 
  // Enter exit frame.
  // stack_space - extra stack space, used for alignment before call to C.
  void EnterExitFrame(bool save_doubles, int stack_space = 0);
 
  // Leave the current exit frame. Expects the return value in r0.
  // Expect the number of values, pushed prior to the exit frame, to
  // remove in a register (or no_reg, if there is nothing to remove).
  void LeaveExitFrame(bool save_doubles,
                      Register argument_count,
                      bool restore_context);
 
  // Get the actual activation frame alignment for target environment.
  static int ActivationFrameAlignment();
 
  void LoadContext(Register dst, int context_chain_length);
 
  // Conditionally load the cached Array transitioned map of type
  // transitioned_kind from the native context if the map in register
  // map_in_out is the cached Array map in the native context of
  // expected_kind.
  void LoadTransitionedArrayMapConditional(
      ElementsKind expected_kind,
      ElementsKind transitioned_kind,
      Register map_in_out,
      Register scratch,
      Label* no_map_match);
 
  void LoadGlobalFunction(int index, Register function);
 
  // Load the initial map from the global function. The registers
  // function and map can be the same, function is then overwritten.
  void LoadGlobalFunctionInitialMap(Register function,
                                    Register map,
                                    Register scratch);
 
  void InitializeRootRegister() {
    ExternalReference roots_array_start =
        ExternalReference::roots_array_start(isolate());
    mov(kRootRegister, Operand(roots_array_start));
  }
 
  // ---------------------------------------------------------------------------
  // JavaScript invokes
 
  // Invoke the JavaScript function code by either calling or jumping.
  void InvokeCode(Register code,
                  const ParameterCount& expected,
                  const ParameterCount& actual,
                  InvokeFlag flag,
                  const CallWrapper& call_wrapper);
 
  // Invoke the JavaScript function in the given register. Changes the
  // current context to the context in the function before invoking.
  void InvokeFunction(Register function,
                      const ParameterCount& actual,
                      InvokeFlag flag,
                      const CallWrapper& call_wrapper);
 
  void InvokeFunction(Register function,
                      const ParameterCount& expected,
                      const ParameterCount& actual,
                      InvokeFlag flag,
                      const CallWrapper& call_wrapper);
 
  void InvokeFunction(Handle<JSFunction> function,
                      const ParameterCount& expected,
                      const ParameterCount& actual,
                      InvokeFlag flag,
                      const CallWrapper& call_wrapper);
 
  void IsObjectJSObjectType(Register heap_object,
                            Register map,
                            Register scratch,
                            Label* fail);
 
  void IsInstanceJSObjectType(Register map,
                              Register scratch,
                              Label* fail);
 
  void IsObjectJSStringType(Register object,
                            Register scratch,
                            Label* fail);
 
  void IsObjectNameType(Register object,
                        Register scratch,
                        Label* fail);
 
  // ---------------------------------------------------------------------------
  // Debugger Support
 
  void DebugBreak();
 
  // ---------------------------------------------------------------------------
  // Exception handling
 
  // Push a new try handler and link into try handler chain.
  void PushTryHandler(StackHandler::Kind kind, int handler_index);
 
  // Unlink the stack handler on top of the stack from the try handler chain.
  // Must preserve the result register.
  void PopTryHandler();
 
  // Passes thrown value to the handler of top of the try handler chain.
  void Throw(Register value);
 
  // Propagates an uncatchable exception to the top of the current JS stack's
  // handler chain.
  void ThrowUncatchable(Register value);
 
  // ---------------------------------------------------------------------------
  // Inline caching support
 
  // Generate code for checking access rights - used for security checks
  // on access to global objects across environments. The holder register
  // is left untouched, whereas both scratch registers are clobbered.
  void CheckAccessGlobalProxy(Register holder_reg,
                              Register scratch,
                              Label* miss);
 
  void GetNumberHash(Register t0, Register scratch);
 
  void LoadFromNumberDictionary(Label* miss,
                                Register elements,
                                Register key,
                                Register result,
                                Register t0,
                                Register t1,
                                Register t2);
 
 
  inline void MarkCode(NopMarkerTypes type) {
    nop(type);
  }
 
  // Check if the given instruction is a 'type' marker.
  // i.e. check if is is a mov r<type>, r<type> (referenced as nop(type))
  // These instructions are generated to mark special location in the code,
  // like some special IC code.
  static inline bool IsMarkedCode(Instr instr, int type) {
    DCHECK((FIRST_IC_MARKER <= type) && (type < LAST_CODE_MARKER));
    return IsNop(instr, type);
  }
 
 
  static inline int GetCodeMarker(Instr instr) {
    int dst_reg_offset = 12;
    int dst_mask = 0xf << dst_reg_offset;
    int src_mask = 0xf;
    int dst_reg = (instr & dst_mask) >> dst_reg_offset;
    int src_reg = instr & src_mask;
    uint32_t non_register_mask = ~(dst_mask | src_mask);
    uint32_t mov_mask = al | 13 << 21;
 
    // Return <n> if we have a mov rn rn, else return -1.
    int type = ((instr & non_register_mask) == mov_mask) &&
               (dst_reg == src_reg) &&
               (FIRST_IC_MARKER <= dst_reg) && (dst_reg < LAST_CODE_MARKER)
                   ? src_reg
                   : -1;
    DCHECK((type == -1) ||
           ((FIRST_IC_MARKER <= type) && (type < LAST_CODE_MARKER)));
    return type;
  }
 
 
  // ---------------------------------------------------------------------------
  // Allocation support
 
  // Allocate an object in new space or old pointer space. The object_size is
  // specified either in bytes or in words if the allocation flag SIZE_IN_WORDS
  // is passed. If the space is exhausted control continues at the gc_required
  // label. The allocated object is returned in result. If the flag
  // tag_allocated_object is true the result is tagged as as a heap object.
  // All registers are clobbered also when control continues at the gc_required
  // label.
  void Allocate(int object_size,
                Register result,
                Register scratch1,
                Register scratch2,
                Label* gc_required,
                AllocationFlags flags);
 
  void Allocate(Register object_size,
                Register result,
                Register scratch1,
                Register scratch2,
                Label* gc_required,
                AllocationFlags flags);
 
  // Undo allocation in new space. The object passed and objects allocated after
  // it will no longer be allocated. The caller must make sure that no pointers
  // are left to the object(s) no longer allocated as they would be invalid when
  // allocation is undone.
  void UndoAllocationInNewSpace(Register object, Register scratch);
 
 
  void AllocateTwoByteString(Register result,
                             Register length,
                             Register scratch1,
                             Register scratch2,
                             Register scratch3,
                             Label* gc_required);
  void AllocateOneByteString(Register result, Register length,
                             Register scratch1, Register scratch2,
                             Register scratch3, Label* gc_required);
  void AllocateTwoByteConsString(Register result,
                                 Register length,
                                 Register scratch1,
                                 Register scratch2,
                                 Label* gc_required);
  void AllocateOneByteConsString(Register result, Register length,
                                 Register scratch1, Register scratch2,
                                 Label* gc_required);
  void AllocateTwoByteSlicedString(Register result,
                                   Register length,
                                   Register scratch1,
                                   Register scratch2,
                                   Label* gc_required);
  void AllocateOneByteSlicedString(Register result, Register length,
                                   Register scratch1, Register scratch2,
                                   Label* gc_required);
 
  // Allocates a heap number or jumps to the gc_required label if the young
  // space is full and a scavenge is needed. All registers are clobbered also
  // when control continues at the gc_required label.
  void AllocateHeapNumber(Register result,
                          Register scratch1,
                          Register scratch2,
                          Register heap_number_map,
                          Label* gc_required,
                          TaggingMode tagging_mode = TAG_RESULT,
                          MutableMode mode = IMMUTABLE);
  void AllocateHeapNumberWithValue(Register result,
                                   DwVfpRegister value,
                                   Register scratch1,
                                   Register scratch2,
                                   Register heap_number_map,
                                   Label* gc_required);
 
  // Copies a fixed number of fields of heap objects from src to dst.
  void CopyFields(Register dst,
                  Register src,
                  LowDwVfpRegister double_scratch,
                  int field_count);
 
  // Copies a number of bytes from src to dst. All registers are clobbered. On
  // exit src and dst will point to the place just after where the last byte was
  // read or written and length will be zero.
  void CopyBytes(Register src,
                 Register dst,
                 Register length,
                 Register scratch);
 
  // Initialize fields with filler values.  Fields starting at |start_offset|
  // not including end_offset are overwritten with the value in |filler|.  At
  // the end the loop, |start_offset| takes the value of |end_offset|.
  void InitializeFieldsWithFiller(Register start_offset,
                                  Register end_offset,
                                  Register filler);
 
  // ---------------------------------------------------------------------------
  // Support functions.
 
  // Try to get function prototype of a function and puts the value in
  // the result register. Checks that the function really is a
  // function and jumps to the miss label if the fast checks fail. The
  // function register will be untouched; the other registers may be
  // clobbered.
  void TryGetFunctionPrototype(Register function,
                               Register result,
                               Register scratch,
                               Label* miss,
                               bool miss_on_bound_function = false);
 
  // Compare object type for heap object.  heap_object contains a non-Smi
  // whose object type should be compared with the given type.  This both
  // sets the flags and leaves the object type in the type_reg register.
  // It leaves the map in the map register (unless the type_reg and map register
  // are the same register).  It leaves the heap object in the heap_object
  // register unless the heap_object register is the same register as one of the
  // other registers.
  // Type_reg can be no_reg. In that case ip is used.
  void CompareObjectType(Register heap_object,
                         Register map,
                         Register type_reg,
                         InstanceType type);
 
  // Compare object type for heap object. Branch to false_label if type
  // is lower than min_type or greater than max_type.
  // Load map into the register map.
  void CheckObjectTypeRange(Register heap_object,
                            Register map,
                            InstanceType min_type,
                            InstanceType max_type,
                            Label* false_label);
 
  // Compare instance type in a map.  map contains a valid map object whose
  // object type should be compared with the given type.  This both
  // sets the flags and leaves the object type in the type_reg register.
  void CompareInstanceType(Register map,
                           Register type_reg,
                           InstanceType type);
 
 
  // Check if a map for a JSObject indicates that the object has fast elements.
  // Jump to the specified label if it does not.
  void CheckFastElements(Register map,
                         Register scratch,
                         Label* fail);
 
  // Check if a map for a JSObject indicates that the object can have both smi
  // and HeapObject elements.  Jump to the specified label if it does not.
  void CheckFastObjectElements(Register map,
                               Register scratch,
                               Label* fail);
 
  // Check if a map for a JSObject indicates that the object has fast smi only
  // elements.  Jump to the specified label if it does not.
  void CheckFastSmiElements(Register map,
                            Register scratch,
                            Label* fail);
 
  // Check to see if maybe_number can be stored as a double in
  // FastDoubleElements. If it can, store it at the index specified by key in
  // the FastDoubleElements array elements. Otherwise jump to fail.
  void StoreNumberToDoubleElements(Register value_reg,
                                   Register key_reg,
                                   Register elements_reg,
                                   Register scratch1,
                                   LowDwVfpRegister double_scratch,
                                   Label* fail,
                                   int elements_offset = 0);
 
  // Compare an object's map with the specified map and its transitioned
  // elements maps if mode is ALLOW_ELEMENT_TRANSITION_MAPS. Condition flags are
  // set with result of map compare. If multiple map compares are required, the
  // compare sequences branches to early_success.
  void CompareMap(Register obj,
                  Register scratch,
                  Handle<Map> map,
                  Label* early_success);
 
  // As above, but the map of the object is already loaded into the register
  // which is preserved by the code generated.
  void CompareMap(Register obj_map,
                  Handle<Map> map,
                  Label* early_success);
 
  // Check if the map of an object is equal to a specified map and branch to
  // label if not. Skip the smi check if not required (object is known to be a
  // heap object). If mode is ALLOW_ELEMENT_TRANSITION_MAPS, then also match
  // against maps that are ElementsKind transition maps of the specified map.
  void CheckMap(Register obj,
                Register scratch,
                Handle<Map> map,
                Label* fail,
                SmiCheckType smi_check_type);
 
 
  void CheckMap(Register obj,
                Register scratch,
                Heap::RootListIndex index,
                Label* fail,
                SmiCheckType smi_check_type);
 
 
  // Check if the map of an object is equal to a specified map and branch to a
  // specified target if equal. Skip the smi check if not required (object is
  // known to be a heap object)
  void DispatchMap(Register obj,
                   Register scratch,
                   Handle<Map> map,
                   Handle<Code> success,
                   SmiCheckType smi_check_type);
 
 
  // Compare the object in a register to a value from the root list.
  // Uses the ip register as scratch.
  void CompareRoot(Register obj, Heap::RootListIndex index);
 
 
  // Load and check the instance type of an object for being a string.
  // Loads the type into the second argument register.
  // Returns a condition that will be enabled if the object was a string
  // and the passed-in condition passed. If the passed-in condition failed
  // then flags remain unchanged.
  Condition IsObjectStringType(Register obj,
                               Register type,
                               Condition cond = al) {
    ldr(type, FieldMemOperand(obj, HeapObject::kMapOffset), cond);
    ldrb(type, FieldMemOperand(type, Map::kInstanceTypeOffset), cond);
    tst(type, Operand(kIsNotStringMask), cond);
    DCHECK_EQ(0, kStringTag);
    return eq;
  }
 
 
  // Picks out an array index from the hash field.
  // Register use:
  //   hash - holds the index's hash. Clobbered.
  //   index - holds the overwritten index on exit.
  void IndexFromHash(Register hash, Register index);
 
  // Get the number of least significant bits from a register
  void GetLeastBitsFromSmi(Register dst, Register src, int num_least_bits);
  void GetLeastBitsFromInt32(Register dst, Register src, int mun_least_bits);
 
  // Load the value of a smi object into a double register.
  // The register value must be between d0 and d15.
  void SmiToDouble(LowDwVfpRegister value, Register smi);
 
  // Check if a double can be exactly represented as a signed 32-bit integer.
  // Z flag set to one if true.
  void TestDoubleIsInt32(DwVfpRegister double_input,
                         LowDwVfpRegister double_scratch);
 
  // Try to convert a double to a signed 32-bit integer.
  // Z flag set to one and result assigned if the conversion is exact.
  void TryDoubleToInt32Exact(Register result,
                             DwVfpRegister double_input,
                             LowDwVfpRegister double_scratch);
 
  // Floor a double and writes the value to the result register.
  // Go to exact if the conversion is exact (to be able to test -0),
  // fall through calling code if an overflow occurred, else go to done.
  // In return, input_high is loaded with high bits of input.
  void TryInt32Floor(Register result,
                     DwVfpRegister double_input,
                     Register input_high,
                     LowDwVfpRegister double_scratch,
                     Label* done,
                     Label* exact);
 
  // Performs a truncating conversion of a floating point number as used by
  // the JS bitwise operations. See ECMA-262 9.5: ToInt32. Goes to 'done' if it
  // succeeds, otherwise falls through if result is saturated. On return
  // 'result' either holds answer, or is clobbered on fall through.
  //
  // Only public for the test code in test-code-stubs-arm.cc.
  void TryInlineTruncateDoubleToI(Register result,
                                  DwVfpRegister input,
                                  Label* done);
 
  // Performs a truncating conversion of a floating point number as used by
  // the JS bitwise operations. See ECMA-262 9.5: ToInt32.
  // Exits with 'result' holding the answer.
  void TruncateDoubleToI(Register result, DwVfpRegister double_input);
 
  // Performs a truncating conversion of a heap number as used by
  // the JS bitwise operations. See ECMA-262 9.5: ToInt32. 'result' and 'input'
  // must be different registers.  Exits with 'result' holding the answer.
  void TruncateHeapNumberToI(Register result, Register object);
 
  // Converts the smi or heap number in object to an int32 using the rules
  // for ToInt32 as described in ECMAScript 9.5.: the value is truncated
  // and brought into the range -2^31 .. +2^31 - 1. 'result' and 'input' must be
  // different registers.
  void TruncateNumberToI(Register object,
                         Register result,
                         Register heap_number_map,
                         Register scratch1,
                         Label* not_int32);
 
  // Check whether d16-d31 are available on the CPU. The result is given by the
  // Z condition flag: Z==0 if d16-d31 available, Z==1 otherwise.
  void CheckFor32DRegs(Register scratch);
 
  // Does a runtime check for 16/32 FP registers. Either way, pushes 32 double
  // values to location, saving [d0..(d15|d31)].
  void SaveFPRegs(Register location, Register scratch);
 
  // Does a runtime check for 16/32 FP registers. Either way, pops 32 double
  // values to location, restoring [d0..(d15|d31)].
  void RestoreFPRegs(Register location, Register scratch);
 
  // ---------------------------------------------------------------------------
  // Runtime calls
 
  // Call a code stub.
  void CallStub(CodeStub* stub,
                TypeFeedbackId ast_id = TypeFeedbackId::None(),
                Condition cond = al);
 
  // Call a code stub.
  void TailCallStub(CodeStub* stub, Condition cond = al);
 
  // Call a runtime routine.
  void CallRuntime(const Runtime::Function* f,
                   int num_arguments,
                   SaveFPRegsMode save_doubles = kDontSaveFPRegs);
  void CallRuntimeSaveDoubles(Runtime::FunctionId id) {
    const Runtime::Function* function = Runtime::FunctionForId(id);
    CallRuntime(function, function->nargs, kSaveFPRegs);
  }
 
  // Convenience function: Same as above, but takes the fid instead.
  void CallRuntime(Runtime::FunctionId id,
                   int num_arguments,
                   SaveFPRegsMode save_doubles = kDontSaveFPRegs) {
    CallRuntime(Runtime::FunctionForId(id), num_arguments, save_doubles);
  }
 
  // Convenience function: call an external reference.
  void CallExternalReference(const ExternalReference& ext,
                             int num_arguments);
 
  // Tail call of a runtime routine (jump).
  // Like JumpToExternalReference, but also takes care of passing the number
  // of parameters.
  void TailCallExternalReference(const ExternalReference& ext,
                                 int num_arguments,
                                 int result_size);
 
  // Convenience function: tail call a runtime routine (jump).
  void TailCallRuntime(Runtime::FunctionId fid,
                       int num_arguments,
                       int result_size);
 
  int CalculateStackPassedWords(int num_reg_arguments,
                                int num_double_arguments);
 
  // Before calling a C-function from generated code, align arguments on stack.
  // After aligning the frame, non-register arguments must be stored in
  // sp[0], sp[4], etc., not pushed. The argument count assumes all arguments
  // are word sized. If double arguments are used, this function assumes that
  // all double arguments are stored before core registers; otherwise the
  // correct alignment of the double values is not guaranteed.
  // Some compilers/platforms require the stack to be aligned when calling
  // C++ code.
  // Needs a scratch register to do some arithmetic. This register will be
  // trashed.
  void PrepareCallCFunction(int num_reg_arguments,
                            int num_double_registers,
                            Register scratch);
  void PrepareCallCFunction(int num_reg_arguments,
                            Register scratch);
 
  // There are two ways of passing double arguments on ARM, depending on
  // whether soft or hard floating point ABI is used. These functions
  // abstract parameter passing for the three different ways we call
  // C functions from generated code.
  void MovToFloatParameter(DwVfpRegister src);
  void MovToFloatParameters(DwVfpRegister src1, DwVfpRegister src2);
  void MovToFloatResult(DwVfpRegister src);
 
  // Calls a C function and cleans up the space for arguments allocated
  // by PrepareCallCFunction. The called function is not allowed to trigger a
  // garbage collection, since that might move the code and invalidate the
  // return address (unless this is somehow accounted for by the called
  // function).
  void CallCFunction(ExternalReference function, int num_arguments);
  void CallCFunction(Register function, int num_arguments);
  void CallCFunction(ExternalReference function,
                     int num_reg_arguments,
                     int num_double_arguments);
  void CallCFunction(Register function,
                     int num_reg_arguments,
                     int num_double_arguments);
 
  void MovFromFloatParameter(DwVfpRegister dst);
  void MovFromFloatResult(DwVfpRegister dst);
 
  // Calls an API function.  Allocates HandleScope, extracts returned value
  // from handle and propagates exceptions.  Restores context.  stack_space
  // - space to be unwound on exit (includes the call JS arguments space and
  // the additional space allocated for the fast call).
  void CallApiFunctionAndReturn(Register function_address,
                                ExternalReference thunk_ref,
                                int stack_space,
                                MemOperand return_value_operand,
                                MemOperand* context_restore_operand);
 
  // Jump to a runtime routine.
  void JumpToExternalReference(const ExternalReference& builtin);
 
  // Invoke specified builtin JavaScript function. Adds an entry to
  // the unresolved list if the name does not resolve.
  void InvokeBuiltin(Builtins::JavaScript id,
                     InvokeFlag flag,
                     const CallWrapper& call_wrapper = NullCallWrapper());
 
  // Store the code object for the given builtin in the target register and
  // setup the function in r1.
  void GetBuiltinEntry(Register target, Builtins::JavaScript id);
 
  // Store the function for the given builtin in the target register.
  void GetBuiltinFunction(Register target, Builtins::JavaScript id);
 
  Handle<Object> CodeObject() {
    DCHECK(!code_object_.is_null());
    return code_object_;
  }
 
 
  // Emit code for a truncating division by a constant. The dividend register is
  // unchanged and ip gets clobbered. Dividend and result must be different.
  void TruncatingDiv(Register result, Register dividend, int32_t divisor);
 
  // ---------------------------------------------------------------------------
  // StatsCounter support
 
  void SetCounter(StatsCounter* counter, int value,
                  Register scratch1, Register scratch2);
  void IncrementCounter(StatsCounter* counter, int value,
                        Register scratch1, Register scratch2);
  void DecrementCounter(StatsCounter* counter, int value,
                        Register scratch1, Register scratch2);
 
 
  // ---------------------------------------------------------------------------
  // Debugging
 
  // Calls Abort(msg) if the condition cond is not satisfied.
  // Use --debug_code to enable.
  void Assert(Condition cond, BailoutReason reason);
  void AssertFastElements(Register elements);
 
  // Like Assert(), but always enabled.
  void Check(Condition cond, BailoutReason reason);
 
  // Print a message to stdout and abort execution.
  void Abort(BailoutReason msg);
 
  // Verify restrictions about code generated in stubs.
  void set_generating_stub(bool value) { generating_stub_ = value; }
  bool generating_stub() { return generating_stub_; }
  void set_has_frame(bool value) { has_frame_ = value; }
  bool has_frame() { return has_frame_; }
  inline bool AllowThisStubCall(CodeStub* stub);
 
  // EABI variant for double arguments in use.
  bool use_eabi_hardfloat() {
#ifdef __arm__
    return base::OS::ArmUsingHardFloat();
#elif USE_EABI_HARDFLOAT
    return true;
#else
    return false;
#endif
  }
 
  // ---------------------------------------------------------------------------
  // Number utilities
 
  // Check whether the value of reg is a power of two and not zero. If not
  // control continues at the label not_power_of_two. If reg is a power of two
  // the register scratch contains the value of (reg - 1) when control falls
  // through.
  void JumpIfNotPowerOfTwoOrZero(Register reg,
                                 Register scratch,
                                 Label* not_power_of_two_or_zero);
  // Check whether the value of reg is a power of two and not zero.
  // Control falls through if it is, with scratch containing the mask
  // value (reg - 1).
  // Otherwise control jumps to the 'zero_and_neg' label if the value of reg is
  // zero or negative, or jumps to the 'not_power_of_two' label if the value is
  // strictly positive but not a power of two.
  void JumpIfNotPowerOfTwoOrZeroAndNeg(Register reg,
                                       Register scratch,
                                       Label* zero_and_neg,
                                       Label* not_power_of_two);
 
  // ---------------------------------------------------------------------------
  // Smi utilities
 
  void SmiTag(Register reg, SBit s = LeaveCC) {
    add(reg, reg, Operand(reg), s);
  }
  void SmiTag(Register dst, Register src, SBit s = LeaveCC) {
    add(dst, src, Operand(src), s);
  }
 
  // Try to convert int32 to smi. If the value is to large, preserve
  // the original value and jump to not_a_smi. Destroys scratch and
  // sets flags.
  void TrySmiTag(Register reg, Label* not_a_smi) {
    TrySmiTag(reg, reg, not_a_smi);
  }
  void TrySmiTag(Register reg, Register src, Label* not_a_smi) {
    SmiTag(ip, src, SetCC);
    b(vs, not_a_smi);
    mov(reg, ip);
  }
 
 
  void SmiUntag(Register reg, SBit s = LeaveCC) {
    mov(reg, Operand::SmiUntag(reg), s);
  }
  void SmiUntag(Register dst, Register src, SBit s = LeaveCC) {
    mov(dst, Operand::SmiUntag(src), s);
  }
 
  // Untag the source value into destination and jump if source is a smi.
  // Souce and destination can be the same register.
  void UntagAndJumpIfSmi(Register dst, Register src, Label* smi_case);
 
  // Untag the source value into destination and jump if source is not a smi.
  // Souce and destination can be the same register.
  void UntagAndJumpIfNotSmi(Register dst, Register src, Label* non_smi_case);
 
  // Test if the register contains a smi (Z == 0 (eq) if true).
  inline void SmiTst(Register value) {
    tst(value, Operand(kSmiTagMask));
  }
  inline void NonNegativeSmiTst(Register value) {
    tst(value, Operand(kSmiTagMask | kSmiSignMask));
  }
  // Jump if the register contains a smi.
  inline void JumpIfSmi(Register value, Label* smi_label) {
    tst(value, Operand(kSmiTagMask));
    b(eq, smi_label);
  }
  // Jump if either of the registers contain a non-smi.
  inline void JumpIfNotSmi(Register value, Label* not_smi_label) {
    tst(value, Operand(kSmiTagMask));
    b(ne, not_smi_label);
  }
  // Jump if either of the registers contain a non-smi.
  void JumpIfNotBothSmi(Register reg1, Register reg2, Label* on_not_both_smi);
  // Jump if either of the registers contain a smi.
  void JumpIfEitherSmi(Register reg1, Register reg2, Label* on_either_smi);
 
  // Abort execution if argument is a smi, enabled via --debug-code.
  void AssertNotSmi(Register object);
  void AssertSmi(Register object);
 
  // Abort execution if argument is not a string, enabled via --debug-code.
  void AssertString(Register object);
 
  // Abort execution if argument is not a name, enabled via --debug-code.
  void AssertName(Register object);
 
  // Abort execution if argument is not undefined or an AllocationSite, enabled
  // via --debug-code.
  void AssertUndefinedOrAllocationSite(Register object, Register scratch);
 
  // Abort execution if reg is not the root value with the given index,
  // enabled via --debug-code.
  void AssertIsRoot(Register reg, Heap::RootListIndex index);
 
  // ---------------------------------------------------------------------------
  // HeapNumber utilities
 
  void JumpIfNotHeapNumber(Register object,
                           Register heap_number_map,
                           Register scratch,
                           Label* on_not_heap_number);
 
  // ---------------------------------------------------------------------------
  // String utilities
 
  // Generate code to do a lookup in the number string cache. If the number in
  // the register object is found in the cache the generated code falls through
  // with the result in the result register. The object and the result register
  // can be the same. If the number is not found in the cache the code jumps to
  // the label not_found with only the content of register object unchanged.
  void LookupNumberStringCache(Register object,
                               Register result,
                               Register scratch1,
                               Register scratch2,
                               Register scratch3,
                               Label* not_found);
 
  // Checks if both objects are sequential one-byte strings and jumps to label
  // if either is not. Assumes that neither object is a smi.
  void JumpIfNonSmisNotBothSequentialOneByteStrings(Register object1,
                                                    Register object2,
                                                    Register scratch1,
                                                    Register scratch2,
                                                    Label* failure);
 
  // Checks if both objects are sequential one-byte strings and jumps to label
  // if either is not.
  void JumpIfNotBothSequentialOneByteStrings(Register first, Register second,
                                             Register scratch1,
                                             Register scratch2,
                                             Label* not_flat_one_byte_strings);
 
  // Checks if both instance types are sequential one-byte strings and jumps to
  // label if either is not.
  void JumpIfBothInstanceTypesAreNotSequentialOneByte(
      Register first_object_instance_type, Register second_object_instance_type,
      Register scratch1, Register scratch2, Label* failure);
 
  // Check if instance type is sequential one-byte string and jump to label if
  // it is not.
  void JumpIfInstanceTypeIsNotSequentialOneByte(Register type, Register scratch,
                                                Label* failure);
 
  void JumpIfNotUniqueNameInstanceType(Register reg, Label* not_unique_name);
 
  void EmitSeqStringSetCharCheck(Register string,
                                 Register index,
                                 Register value,
                                 uint32_t encoding_mask);
 
  // ---------------------------------------------------------------------------
  // Patching helpers.
 
  // Get the location of a relocated constant (its address in the constant pool)
  // from its load site.
  void GetRelocatedValueLocation(Register ldr_location, Register result,
                                 Register scratch);
 
 
  void ClampUint8(Register output_reg, Register input_reg);
 
  void ClampDoubleToUint8(Register result_reg,
                          DwVfpRegister input_reg,
                          LowDwVfpRegister double_scratch);
 
 
  void LoadInstanceDescriptors(Register map, Register descriptors);
  void EnumLength(Register dst, Register map);
  void NumberOfOwnDescriptors(Register dst, Register map);
 
  template<typename Field>
  void DecodeField(Register dst, Register src) {
    Ubfx(dst, src, Field::kShift, Field::kSize);
  }
 
  template<typename Field>
  void DecodeField(Register reg) {
    DecodeField<Field>(reg, reg);
  }
 
  template<typename Field>
  void DecodeFieldToSmi(Register dst, Register src) {
    static const int shift = Field::kShift;
    static const int mask = Field::kMask >> shift << kSmiTagSize;
    STATIC_ASSERT((mask & (0x80000000u >> (kSmiTagSize - 1))) == 0);
    STATIC_ASSERT(kSmiTag == 0);
    if (shift < kSmiTagSize) {
      mov(dst, Operand(src, LSL, kSmiTagSize - shift));
      and_(dst, dst, Operand(mask));
    } else if (shift > kSmiTagSize) {
      mov(dst, Operand(src, LSR, shift - kSmiTagSize));
      and_(dst, dst, Operand(mask));
    } else {
      and_(dst, src, Operand(mask));
    }
  }
 
  template<typename Field>
  void DecodeFieldToSmi(Register reg) {
    DecodeField<Field>(reg, reg);
  }
 
  // Activation support.
  void EnterFrame(StackFrame::Type type, bool load_constant_pool = false);
  // Returns the pc offset at which the frame ends.
  int LeaveFrame(StackFrame::Type type);
 
  // Expects object in r0 and returns map with validated enum cache
  // in r0.  Assumes that any other register can be used as a scratch.
  void CheckEnumCache(Register null_value, Label* call_runtime);
 
  // AllocationMemento support. Arrays may have an associated
  // AllocationMemento object that can be checked for in order to pretransition
  // to another type.
  // On entry, receiver_reg should point to the array object.
  // scratch_reg gets clobbered.
  // If allocation info is present, condition flags are set to eq.
  void TestJSArrayForAllocationMemento(Register receiver_reg,
                                       Register scratch_reg,
                                       Label* no_memento_found);
 
  void JumpIfJSArrayHasAllocationMemento(Register receiver_reg,
                                         Register scratch_reg,
                                         Label* memento_found) {
    Label no_memento_found;
    TestJSArrayForAllocationMemento(receiver_reg, scratch_reg,
                                    &no_memento_found);
    b(eq, memento_found);
    bind(&no_memento_found);
  }
 
  // Jumps to found label if a prototype map has dictionary elements.
  void JumpIfDictionaryInPrototypeChain(Register object, Register scratch0,
                                        Register scratch1, Label* found);
 
 private:
  void CallCFunctionHelper(Register function,
                           int num_reg_arguments,
                           int num_double_arguments);
 
  void Jump(intptr_t target, RelocInfo::Mode rmode, Condition cond = al);
 
  // Helper functions for generating invokes.
  void InvokePrologue(const ParameterCount& expected,
                      const ParameterCount& actual,
                      Handle<Code> code_constant,
                      Register code_reg,
                      Label* done,
                      bool* definitely_mismatches,
                      InvokeFlag flag,
                      const CallWrapper& call_wrapper);
 
  void InitializeNewString(Register string,
                           Register length,
                           Heap::RootListIndex map_index,
                           Register scratch1,
                           Register scratch2);
 
  // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
  void InNewSpace(Register object,
                  Register scratch,
                  Condition cond,  // eq for new space, ne otherwise.
                  Label* branch);
 
  // Helper for finding the mark bits for an address.  Afterwards, the
  // bitmap register points at the word with the mark bits and the mask
  // the position of the first bit.  Leaves addr_reg unchanged.
  inline void GetMarkBits(Register addr_reg,
                          Register bitmap_reg,
                          Register mask_reg);
 
  // Helper for throwing exceptions.  Compute a handler address and jump to
  // it.  See the implementation for register usage.
  void JumpToHandlerEntry();
 
  // Compute memory operands for safepoint stack slots.
  static int SafepointRegisterStackIndex(int reg_code);
  MemOperand SafepointRegisterSlot(Register reg);
  MemOperand SafepointRegistersAndDoublesSlot(Register reg);
 
  // Loads the constant pool pointer (pp) register.
  void LoadConstantPoolPointerRegister();
 
  bool generating_stub_;
  bool has_frame_;
  // This handle will be patched with the code object on installation.
  Handle<Object> code_object_;
 
  // Needs access to SafepointRegisterStackIndex for compiled frame
  // traversal.
  friend class StandardFrame;
};
 
 
// The code patcher is used to patch (typically) small parts of code e.g. for
// debugging and other types of instrumentation. When using the code patcher
// the exact number of bytes specified must be emitted. It is not legal to emit
// relocation information. If any of these constraints are violated it causes
// an assertion to fail.
class CodePatcher {
 public:
  enum FlushICache {
    FLUSH,
    DONT_FLUSH
  };
 
  CodePatcher(byte* address,
              int instructions,
              FlushICache flush_cache = FLUSH);
  virtual ~CodePatcher();
 
  // Macro assembler to emit code.
  MacroAssembler* masm() { return &masm_; }
 
  // Emit an instruction directly.
  void Emit(Instr instr);
 
  // Emit an address directly.
  void Emit(Address addr);
 
  // Emit the condition part of an instruction leaving the rest of the current
  // instruction unchanged.
  void EmitCondition(Condition cond);
 
 private:
  byte* address_;  // The address of the code being patched.
  int size_;  // Number of bytes of the expected patch size.
  MacroAssembler masm_;  // Macro assembler used to generate the code.
  FlushICache flush_cache_;  // Whether to flush the I cache after patching.
};
 
 
class FrameAndConstantPoolScope {
 public:
  FrameAndConstantPoolScope(MacroAssembler* masm, StackFrame::Type type)
      : masm_(masm),
        type_(type),
        old_has_frame_(masm->has_frame()),
        old_constant_pool_available_(masm->is_constant_pool_available())  {
    // We only want to enable constant pool access for non-manual frame scopes
    // to ensure the constant pool pointer is valid throughout the scope.
    DCHECK(type_ != StackFrame::MANUAL && type_ != StackFrame::NONE);
    masm->set_has_frame(true);
    masm->set_constant_pool_available(true);
    masm->EnterFrame(type, !old_constant_pool_available_);
  }
 
  ~FrameAndConstantPoolScope() {
    masm_->LeaveFrame(type_);
    masm_->set_has_frame(old_has_frame_);
    masm_->set_constant_pool_available(old_constant_pool_available_);
  }
 
  // Normally we generate the leave-frame code when this object goes
  // out of scope.  Sometimes we may need to generate the code somewhere else
  // in addition.  Calling this will achieve that, but the object stays in
  // scope, the MacroAssembler is still marked as being in a frame scope, and
  // the code will be generated again when it goes out of scope.
  void GenerateLeaveFrame() {
    DCHECK(type_ != StackFrame::MANUAL && type_ != StackFrame::NONE);
    masm_->LeaveFrame(type_);
  }
 
 private:
  MacroAssembler* masm_;
  StackFrame::Type type_;
  bool old_has_frame_;
  bool old_constant_pool_available_;
 
  DISALLOW_IMPLICIT_CONSTRUCTORS(FrameAndConstantPoolScope);
};
 
 
// Class for scoping the the unavailability of constant pool access.
class ConstantPoolUnavailableScope {
 public:
  explicit ConstantPoolUnavailableScope(MacroAssembler* masm)
     : masm_(masm),
       old_constant_pool_available_(masm->is_constant_pool_available()) {
    if (FLAG_enable_ool_constant_pool) {
      masm_->set_constant_pool_available(false);
    }
  }
  ~ConstantPoolUnavailableScope() {
    if (FLAG_enable_ool_constant_pool) {
     masm_->set_constant_pool_available(old_constant_pool_available_);
    }
  }
 
 private:
  MacroAssembler* masm_;
  int old_constant_pool_available_;
 
  DISALLOW_IMPLICIT_CONSTRUCTORS(ConstantPoolUnavailableScope);
};
 
 
// -----------------------------------------------------------------------------
// Static helper functions.
 
inline MemOperand ContextOperand(Register context, int index) {
  return MemOperand(context, Context::SlotOffset(index));
}
 
 
inline MemOperand GlobalObjectOperand()  {
  return ContextOperand(cp, Context::GLOBAL_OBJECT_INDEX);
}
 
 
#ifdef GENERATED_CODE_COVERAGE
#define CODE_COVERAGE_STRINGIFY(x) #x
#define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
#define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
#define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
#else
#define ACCESS_MASM(masm) masm->
#endif
 
 
} }  // namespace v8::internal
 
#endif  // V8_ARM_MACRO_ASSEMBLER_ARM_H_