src/ppc/assembler-ppc.h

// Copyright (c) 1994-2006 Sun Microsystems Inc.
// All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// - Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// - Redistribution in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the
// distribution.
//
// - Neither the name of Sun Microsystems or the names of contributors may
// be used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.

// The original source code covered by the above license above has been
// modified significantly by Google Inc.
// Copyright 2014 the V8 project authors. All rights reserved.

// A light-weight PPC Assembler
// Generates user mode instructions for the PPC architecture up

#ifndef V8_PPC_ASSEMBLER_PPC_H_
#define V8_PPC_ASSEMBLER_PPC_H_

#include <stdio.h>
#include <vector>

#include "src/assembler.h"
#include "src/ppc/constants-ppc.h"

#if V8_HOST_ARCH_PPC && \
    (V8_OS_AIX || (V8_TARGET_ARCH_PPC64 && V8_TARGET_BIG_ENDIAN))
#define ABI_USES_FUNCTION_DESCRIPTORS 1
#else
#define ABI_USES_FUNCTION_DESCRIPTORS 0
#endif

#if !V8_HOST_ARCH_PPC || V8_OS_AIX || V8_TARGET_ARCH_PPC64
#define ABI_PASSES_HANDLES_IN_REGS 1
#else
#define ABI_PASSES_HANDLES_IN_REGS 0
#endif

#if !V8_HOST_ARCH_PPC || !V8_TARGET_ARCH_PPC64 || V8_TARGET_LITTLE_ENDIAN
#define ABI_RETURNS_OBJECT_PAIRS_IN_REGS 1
#else
#define ABI_RETURNS_OBJECT_PAIRS_IN_REGS 0
#endif

#if !V8_HOST_ARCH_PPC || (V8_TARGET_ARCH_PPC64 && V8_TARGET_LITTLE_ENDIAN)
#define ABI_CALL_VIA_IP 1
#else
#define ABI_CALL_VIA_IP 0
#endif

#if !V8_HOST_ARCH_PPC || V8_OS_AIX || V8_TARGET_ARCH_PPC64
#define ABI_TOC_REGISTER 2
#else
#define ABI_TOC_REGISTER 13
#endif

#define INSTR_AND_DATA_CACHE_COHERENCY LWSYNC

namespace v8 {
namespace internal {

// clang-format off
#define GENERAL_REGISTERS(V)                              \
  V(r0)  V(sp)  V(r2)  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)  \
  V(r8)  V(r9)  V(r10) V(r11) V(ip) V(r13) V(r14) V(r15)  \
  V(r16) V(r17) V(r18) V(r19) V(r20) V(r21) V(r22) V(r23) \
  V(r24) V(r25) V(r26) V(r27) V(r28) V(r29) V(r30) V(fp)

#if V8_EMBEDDED_CONSTANT_POOL
#define ALLOCATABLE_GENERAL_REGISTERS(V)                  \
  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)                       \
  V(r8)  V(r9)  V(r10) V(r14) V(r15)                      \
  V(r16) V(r17) V(r18) V(r19) V(r20) V(r21) V(r22) V(r23) \
  V(r24) V(r25) V(r26) V(r27) V(r30)
#else
#define ALLOCATABLE_GENERAL_REGISTERS(V)                  \
  V(r3)  V(r4)  V(r5)  V(r6)  V(r7)                       \
  V(r8)  V(r9)  V(r10) V(r14) V(r15)                      \
  V(r16) V(r17) V(r18) V(r19) V(r20) V(r21) V(r22) V(r23) \
  V(r24) V(r25) V(r26) V(r27) V(r28) V(r30)
#endif

#define DOUBLE_REGISTERS(V)                               \
  V(d0)  V(d1)  V(d2)  V(d3)  V(d4)  V(d5)  V(d6)  V(d7)  \
  V(d8)  V(d9)  V(d10) V(d11) V(d12) V(d13) V(d14) V(d15) \
  V(d16) V(d17) V(d18) V(d19) V(d20) V(d21) V(d22) V(d23) \
  V(d24) V(d25) V(d26) V(d27) V(d28) V(d29) V(d30) V(d31)

#define FLOAT_REGISTERS DOUBLE_REGISTERS
#define SIMD128_REGISTERS DOUBLE_REGISTERS

#define ALLOCATABLE_DOUBLE_REGISTERS(V)                   \
  V(d1)  V(d2)  V(d3)  V(d4)  V(d5)  V(d6)  V(d7)         \
  V(d8)  V(d9)  V(d10) V(d11) V(d12) V(d15)               \
  V(d16) V(d17) V(d18) V(d19) V(d20) V(d21) V(d22) V(d23) \
  V(d24) V(d25) V(d26) V(d27) V(d28) V(d29) V(d30) V(d31)
// clang-format on

// CPU Registers.
//
// 1) We would prefer to use an enum, but enum values are assignment-
// compatible with int, which has caused code-generation bugs.
//
// 2) We would prefer to use a class instead of a struct but we don't like
// the register initialization to depend on the particular initialization
// order (which appears to be different on OS X, Linux, and Windows for the
// installed versions of C++ we tried). Using a struct permits C-style
// "initialization". Also, the Register objects cannot be const as this
// forces initialization stubs in MSVC, making us dependent on initialization
// order.
//
// 3) By not using an enum, we are possibly preventing the compiler from
// doing certain constant folds, which may significantly reduce the
// code generated for some assembly instructions (because they boil down
// to a few constants). If this is a problem, we could change the code
// such that we use an enum in optimized mode, and the struct in debug
// mode. This way we get the compile-time error checking in debug mode
// and best performance in optimized code.

struct Register {
  enum Code {
#define REGISTER_CODE(R) kCode_##R,
    GENERAL_REGISTERS(REGISTER_CODE)
#undef REGISTER_CODE
        kAfterLast,
    kCode_no_reg = -1
  };

  static const int kNumRegisters = Code::kAfterLast;

#define REGISTER_COUNT(R) 1 +
  static const int kNumAllocatable =
      ALLOCATABLE_GENERAL_REGISTERS(REGISTER_COUNT)0;
#undef REGISTER_COUNT

#define REGISTER_BIT(R) 1 << kCode_##R |
  static const RegList kAllocatable =
      ALLOCATABLE_GENERAL_REGISTERS(REGISTER_BIT)0;
#undef REGISTER_BIT

  static Register from_code(int code) {
    DCHECK(code >= 0);
    DCHECK(code < kNumRegisters);
    Register r = {code};
    return r;
  }
  bool is_valid() const { return 0 <= reg_code && reg_code < kNumRegisters; }
  bool is(Register reg) const { return reg_code == reg.reg_code; }
  int code() const {
    DCHECK(is_valid());
    return reg_code;
  }
  int bit() const {
    DCHECK(is_valid());
    return 1 << reg_code;
  }
  void set_code(int code) {
    reg_code = code;
    DCHECK(is_valid());
  }

#if V8_TARGET_LITTLE_ENDIAN
  static const int kMantissaOffset = 0;
  static const int kExponentOffset = 4;
#else
  static const int kMantissaOffset = 4;
  static const int kExponentOffset = 0;
#endif

  // Unfortunately we can't make this private in a struct.
  int reg_code;
};

#define DECLARE_REGISTER(R) const Register R = {Register::kCode_##R};
GENERAL_REGISTERS(DECLARE_REGISTER)
#undef DECLARE_REGISTER
const Register no_reg = {Register::kCode_no_reg};

// Aliases
const Register kLithiumScratch = r11;        // lithium scratch.
const Register kConstantPoolRegister = r28;  // Constant pool.
const Register kRootRegister = r29;          // Roots array pointer.
const Register cp = r30;                     // JavaScript context pointer.

static const bool kSimpleFPAliasing = true;

// Double word FP register.
struct DoubleRegister {
  enum Code {
#define REGISTER_CODE(R) kCode_##R,
    DOUBLE_REGISTERS(REGISTER_CODE)
#undef REGISTER_CODE
        kAfterLast,
    kCode_no_reg = -1
  };

  static const int kNumRegisters = Code::kAfterLast;
  static const int kMaxNumRegisters = kNumRegisters;

  bool is_valid() const { return 0 <= reg_code && reg_code < kNumRegisters; }
  bool is(DoubleRegister reg) const { return reg_code == reg.reg_code; }
  int code() const {
    DCHECK(is_valid());
    return reg_code;
  }
  int bit() const {
    DCHECK(is_valid());
    return 1 << reg_code;
  }

  static DoubleRegister from_code(int code) {
    DoubleRegister r = {code};
    return r;
  }

  int reg_code;
};

typedef DoubleRegister FloatRegister;

// TODO(ppc) Define SIMD registers.
typedef DoubleRegister Simd128Register;

#define DECLARE_REGISTER(R) \
  const DoubleRegister R = {DoubleRegister::kCode_##R};
DOUBLE_REGISTERS(DECLARE_REGISTER)
#undef DECLARE_REGISTER
const Register no_dreg = {Register::kCode_no_reg};

// Aliases for double registers.  Defined using #define instead of
// "static const DoubleRegister&" because Clang complains otherwise when a
// compilation unit that includes this header doesn't use the variables.
#define kFirstCalleeSavedDoubleReg d14
#define kLastCalleeSavedDoubleReg d31
#define kDoubleRegZero d14
#define kScratchDoubleReg d13

Register ToRegister(int num);

// Coprocessor register
struct CRegister {
  bool is_valid() const { return 0 <= reg_code && reg_code < 8; }
  bool is(CRegister creg) const { return reg_code == creg.reg_code; }
  int code() const {
    DCHECK(is_valid());
    return reg_code;
  }
  int bit() const {
    DCHECK(is_valid());
    return 1 << reg_code;
  }

  // Unfortunately we can't make this private in a struct.
  int reg_code;
};


const CRegister no_creg = {-1};

const CRegister cr0 = {0};
const CRegister cr1 = {1};
const CRegister cr2 = {2};
const CRegister cr3 = {3};
const CRegister cr4 = {4};
const CRegister cr5 = {5};
const CRegister cr6 = {6};
const CRegister cr7 = {7};

// -----------------------------------------------------------------------------
// Machine instruction Operands

#if V8_TARGET_ARCH_PPC64
const RelocInfo::Mode kRelocInfo_NONEPTR = RelocInfo::NONE64;
#else
const RelocInfo::Mode kRelocInfo_NONEPTR = RelocInfo::NONE32;
#endif

// Class Operand represents a shifter operand in data processing instructions
class Operand BASE_EMBEDDED {
 public:
  // immediate
  INLINE(explicit Operand(intptr_t immediate,
                          RelocInfo::Mode rmode = kRelocInfo_NONEPTR));
  INLINE(static Operand Zero()) { return Operand(static_cast<intptr_t>(0)); }
  INLINE(explicit Operand(const ExternalReference& f));
  explicit Operand(Handle<Object> handle);
  INLINE(explicit Operand(Smi* value));

  // rm
  INLINE(explicit Operand(Register rm));

  // Return true if this is a register operand.
  INLINE(bool is_reg() const);

  bool must_output_reloc_info(const Assembler* assembler) const;

  inline intptr_t immediate() const {
    DCHECK(!rm_.is_valid());
    return imm_;
  }

  Register rm() const { return rm_; }

 private:
  Register rm_;
  intptr_t imm_;  // valid if rm_ == no_reg
  RelocInfo::Mode rmode_;

  friend class Assembler;
  friend class MacroAssembler;
};


// Class MemOperand represents a memory operand in load and store instructions
// On PowerPC we have base register + 16bit signed value
// Alternatively we can have a 16bit signed value immediate
class MemOperand BASE_EMBEDDED {
 public:
  explicit MemOperand(Register rn, int32_t offset = 0);

  explicit MemOperand(Register ra, Register rb);

  int32_t offset() const {
    DCHECK(rb_.is(no_reg));
    return offset_;
  }

  // PowerPC - base register
  Register ra() const {
    DCHECK(!ra_.is(no_reg));
    return ra_;
  }

  Register rb() const {
    DCHECK(offset_ == 0 && !rb_.is(no_reg));
    return rb_;
  }

 private:
  Register ra_;     // base
  int32_t offset_;  // offset
  Register rb_;     // index

  friend class Assembler;
};


class DeferredRelocInfo {
 public:
  DeferredRelocInfo() {}
  DeferredRelocInfo(int position, RelocInfo::Mode rmode, intptr_t data)
      : position_(position), rmode_(rmode), data_(data) {}

  int position() const { return position_; }
  RelocInfo::Mode rmode() const { return rmode_; }
  intptr_t data() const { return data_; }

 private:
  int position_;
  RelocInfo::Mode rmode_;
  intptr_t data_;
};


class Assembler : public AssemblerBase {
 public:
  // Create an assembler. Instructions and relocation information are emitted
  // into a buffer, with the instructions starting from the beginning and the
  // relocation information starting from the end of the buffer. See CodeDesc
  // for a detailed comment on the layout (globals.h).
  //
  // If the provided buffer is NULL, the assembler allocates and grows its own
  // buffer, and buffer_size determines the initial buffer size. The buffer is
  // owned by the assembler and deallocated upon destruction of the assembler.
  //
  // If the provided buffer is not NULL, the assembler uses the provided buffer
  // for code generation and assumes its size to be buffer_size. If the buffer
  // is too small, a fatal error occurs. No deallocation of the buffer is done
  // upon destruction of the assembler.
  Assembler(Isolate* isolate, void* buffer, int buffer_size);
  virtual ~Assembler() {}

  // GetCode emits any pending (non-emitted) code and fills the descriptor
  // desc. GetCode() is idempotent; it returns the same result if no other
  // Assembler functions are invoked in between GetCode() calls.
  void GetCode(CodeDesc* desc);

  // Label operations & relative jumps (PPUM Appendix D)
  //
  // Takes a branch opcode (cc) and a label (L) and generates
  // either a backward branch or a forward branch and links it
  // to the label fixup chain. Usage:
  //
  // Label L;    // unbound label
  // j(cc, &L);  // forward branch to unbound label
  // bind(&L);   // bind label to the current pc
  // j(cc, &L);  // backward branch to bound label
  // bind(&L);   // illegal: a label may be bound only once
  //
  // Note: The same Label can be used for forward and backward branches
  // but it may be bound only once.

  void bind(Label* L);  // binds an unbound label L to the current code position

  // Links a label at the current pc_offset().  If already bound, returns the
  // bound position.  If already linked, returns the position of the prior link.
  // Otherwise, returns the current pc_offset().
  int link(Label* L);

  // Determines if Label is bound and near enough so that a single
  // branch instruction can be used to reach it.
  bool is_near(Label* L, Condition cond);

  // Returns the branch offset to the given label from the current code position
  // Links the label to the current position if it is still unbound
  int branch_offset(Label* L) {
    if (L->is_unused() && !trampoline_emitted_) {
      TrackBranch();
    }
    return link(L) - pc_offset();
  }

  // Puts a labels target address at the given position.
  // The high 8 bits are set to zero.
  void label_at_put(Label* L, int at_offset);

  INLINE(static bool IsConstantPoolLoadStart(
      Address pc, ConstantPoolEntry::Access* access = nullptr));
  INLINE(static bool IsConstantPoolLoadEnd(
      Address pc, ConstantPoolEntry::Access* access = nullptr));
  INLINE(static int GetConstantPoolOffset(Address pc,
                                          ConstantPoolEntry::Access access,
                                          ConstantPoolEntry::Type type));
  INLINE(void PatchConstantPoolAccessInstruction(
      int pc_offset, int offset, ConstantPoolEntry::Access access,
      ConstantPoolEntry::Type type));

  // Return the address in the constant pool of the code target address used by
  // the branch/call instruction at pc, or the object in a mov.
  INLINE(static Address target_constant_pool_address_at(
      Address pc, Address constant_pool, ConstantPoolEntry::Access access,
      ConstantPoolEntry::Type type));

  // Read/Modify the code target address in the branch/call instruction at pc.
  INLINE(static Address target_address_at(Address pc, Address constant_pool));
  INLINE(static void set_target_address_at(
      Isolate* isolate, Address pc, Address constant_pool, Address target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED));
  INLINE(static Address target_address_at(Address pc, Code* code)) {
    Address constant_pool = code ? code->constant_pool() : NULL;
    return target_address_at(pc, constant_pool);
  }
  INLINE(static void set_target_address_at(
      Isolate* isolate, Address pc, Code* code, Address target,
      ICacheFlushMode icache_flush_mode = FLUSH_ICACHE_IF_NEEDED)) {
    Address constant_pool = code ? code->constant_pool() : NULL;
    set_target_address_at(isolate, pc, constant_pool, target,
                          icache_flush_mode);
  }

  // Return the code target address at a call site from the return address
  // of that call in the instruction stream.
  inline static Address target_address_from_return_address(Address pc);

  // Given the address of the beginning of a call, return the address
  // in the instruction stream that the call will return to.
  INLINE(static Address return_address_from_call_start(Address pc));

  // This sets the branch destination.
  // This is for calls and branches within generated code.
  inline static void deserialization_set_special_target_at(
      Isolate* isolate, Address instruction_payload, Code* code,
      Address target);

  // This sets the internal reference at the pc.
  inline static void deserialization_set_target_internal_reference_at(
      Isolate* isolate, Address pc, Address target,
      RelocInfo::Mode mode = RelocInfo::INTERNAL_REFERENCE);

  // Size of an instruction.
  static const int kInstrSize = sizeof(Instr);

  // Here we are patching the address in the LUI/ORI instruction pair.
  // These values are used in the serialization process and must be zero for
  // PPC platform, as Code, Embedded Object or External-reference pointers
  // are split across two consecutive instructions and don't exist separately
  // in the code, so the serializer should not step forwards in memory after
  // a target is resolved and written.
  static const int kSpecialTargetSize = 0;

// Number of instructions to load an address via a mov sequence.
#if V8_TARGET_ARCH_PPC64
  static const int kMovInstructionsConstantPool = 1;
  static const int kMovInstructionsNoConstantPool = 5;
#if defined(V8_PPC_TAGGING_OPT)
  static const int kTaggedLoadInstructions = 1;
#else
  static const int kTaggedLoadInstructions = 2;
#endif
#else
  static const int kMovInstructionsConstantPool = 1;
  static const int kMovInstructionsNoConstantPool = 2;
  static const int kTaggedLoadInstructions = 1;
#endif
  static const int kMovInstructions = FLAG_enable_embedded_constant_pool
                                          ? kMovInstructionsConstantPool
                                          : kMovInstructionsNoConstantPool;

  // Distance between the instruction referring to the address of the call
  // target and the return address.

  // Call sequence is a FIXED_SEQUENCE:
  // mov     r8, @ call address
  // mtlr    r8
  // blrl
  //                      @ return address
  static const int kCallTargetAddressOffset =
      (kMovInstructions + 2) * kInstrSize;

  // Distance between start of patched debug break slot and the emitted address
  // to jump to.
  // Patched debug break slot code is a FIXED_SEQUENCE:
  //   mov r0, <address>
  //   mtlr r0
  //   blrl
  static const int kPatchDebugBreakSlotAddressOffset = 0 * kInstrSize;

  // This is the length of the code sequence from SetDebugBreakAtSlot()
  // FIXED_SEQUENCE
  static const int kDebugBreakSlotInstructions =
      kMovInstructionsNoConstantPool + 2;
  static const int kDebugBreakSlotLength =
      kDebugBreakSlotInstructions * kInstrSize;

  static inline int encode_crbit(const CRegister& cr, enum CRBit crbit) {
    return ((cr.code() * CRWIDTH) + crbit);
  }

  // ---------------------------------------------------------------------------
  // Code generation

  // Insert the smallest number of nop instructions
  // possible to align the pc offset to a multiple
  // of m. m must be a power of 2 (>= 4).
  void Align(int m);
  // Insert the smallest number of zero bytes possible to align the pc offset
  // to a mulitple of m. m must be a power of 2 (>= 2).
  void DataAlign(int m);
  // Aligns code to something that's optimal for a jump target for the platform.
  void CodeTargetAlign();

  // Branch instructions
  void bclr(BOfield bo, int condition_bit, LKBit lk);
  void blr();
  void bc(int branch_offset, BOfield bo, int condition_bit, LKBit lk = LeaveLK);
  void b(int branch_offset, LKBit lk);

  void bcctr(BOfield bo, int condition_bit, LKBit lk);
  void bctr();
  void bctrl();

  // Convenience branch instructions using labels
  void b(Label* L, LKBit lk = LeaveLK) { b(branch_offset(L), lk); }

  inline CRegister cmpi_optimization(CRegister cr) {
    // Check whether the branch is preceeded by an optimizable cmpi against 0.
    // The cmpi can be deleted if it is also preceeded by an instruction that
    // sets the register used by the compare and supports a dot form.
    unsigned int sradi_mask = kOpcodeMask | kExt2OpcodeVariant2Mask;
    unsigned int srawi_mask = kOpcodeMask | kExt2OpcodeMask;
    int pos = pc_offset();
    int cmpi_pos = pc_offset() - kInstrSize;

    if (cmpi_pos > 0 && optimizable_cmpi_pos_ == cmpi_pos &&
        cmpi_cr_.code() == cr.code() && last_bound_pos_ != pos) {
      int xpos = cmpi_pos - kInstrSize;
      int xinstr = instr_at(xpos);
      int cmpi_ra = (instr_at(cmpi_pos) & 0x1f0000) >> 16;
      // ra is at the same bit position for the three cases below.
      int ra = (xinstr & 0x1f0000) >> 16;
      if (cmpi_ra == ra) {
        if ((xinstr & sradi_mask) == (EXT2 | SRADIX)) {
          cr = cr0;
          instr_at_put(xpos, xinstr | SetRC);
          pc_ -= kInstrSize;
        } else if ((xinstr & srawi_mask) == (EXT2 | SRAWIX)) {
          cr = cr0;
          instr_at_put(xpos, xinstr | SetRC);
          pc_ -= kInstrSize;
        } else if ((xinstr & kOpcodeMask) == ANDIx) {
          cr = cr0;
          pc_ -= kInstrSize;
          // nothing to do here since andi. records.
        }
        // didn't match one of the above, must keep cmpwi.
      }
    }
    return cr;
  }

  void bc_short(Condition cond, Label* L, CRegister cr = cr7,
                LKBit lk = LeaveLK) {
    DCHECK(cond != al);
    DCHECK(cr.code() >= 0 && cr.code() <= 7);

    cr = cmpi_optimization(cr);

    int b_offset = branch_offset(L);

    switch (cond) {
      case eq:
        bc(b_offset, BT, encode_crbit(cr, CR_EQ), lk);
        break;
      case ne:
        bc(b_offset, BF, encode_crbit(cr, CR_EQ), lk);
        break;
      case gt:
        bc(b_offset, BT, encode_crbit(cr, CR_GT), lk);
        break;
      case le:
        bc(b_offset, BF, encode_crbit(cr, CR_GT), lk);
        break;
      case lt:
        bc(b_offset, BT, encode_crbit(cr, CR_LT), lk);
        break;
      case ge:
        bc(b_offset, BF, encode_crbit(cr, CR_LT), lk);
        break;
      case unordered:
        bc(b_offset, BT, encode_crbit(cr, CR_FU), lk);
        break;
      case ordered:
        bc(b_offset, BF, encode_crbit(cr, CR_FU), lk);
        break;
      case overflow:
        bc(b_offset, BT, encode_crbit(cr, CR_SO), lk);
        break;
      case nooverflow:
        bc(b_offset, BF, encode_crbit(cr, CR_SO), lk);
        break;
      default:
        UNIMPLEMENTED();
    }
  }

  void bclr(Condition cond, CRegister cr = cr7, LKBit lk = LeaveLK) {
    DCHECK(cond != al);
    DCHECK(cr.code() >= 0 && cr.code() <= 7);

    cr = cmpi_optimization(cr);

    switch (cond) {
      case eq:
        bclr(BT, encode_crbit(cr, CR_EQ), lk);
        break;
      case ne:
        bclr(BF, encode_crbit(cr, CR_EQ), lk);
        break;
      case gt:
        bclr(BT, encode_crbit(cr, CR_GT), lk);
        break;
      case le:
        bclr(BF, encode_crbit(cr, CR_GT), lk);
        break;
      case lt:
        bclr(BT, encode_crbit(cr, CR_LT), lk);
        break;
      case ge:
        bclr(BF, encode_crbit(cr, CR_LT), lk);
        break;
      case unordered:
        bclr(BT, encode_crbit(cr, CR_FU), lk);
        break;
      case ordered:
        bclr(BF, encode_crbit(cr, CR_FU), lk);
        break;
      case overflow:
        bclr(BT, encode_crbit(cr, CR_SO), lk);
        break;
      case nooverflow:
        bclr(BF, encode_crbit(cr, CR_SO), lk);
        break;
      default:
        UNIMPLEMENTED();
    }
  }

  void isel(Register rt, Register ra, Register rb, int cb);
  void isel(Condition cond, Register rt, Register ra, Register rb,
            CRegister cr = cr7) {
    DCHECK(cond != al);
    DCHECK(cr.code() >= 0 && cr.code() <= 7);

    cr = cmpi_optimization(cr);

    switch (cond) {
      case eq:
        isel(rt, ra, rb, encode_crbit(cr, CR_EQ));
        break;
      case ne:
        isel(rt, rb, ra, encode_crbit(cr, CR_EQ));
        break;
      case gt:
        isel(rt, ra, rb, encode_crbit(cr, CR_GT));
        break;
      case le:
        isel(rt, rb, ra, encode_crbit(cr, CR_GT));
        break;
      case lt:
        isel(rt, ra, rb, encode_crbit(cr, CR_LT));
        break;
      case ge:
        isel(rt, rb, ra, encode_crbit(cr, CR_LT));
        break;
      case unordered:
        isel(rt, ra, rb, encode_crbit(cr, CR_FU));
        break;
      case ordered:
        isel(rt, rb, ra, encode_crbit(cr, CR_FU));
        break;
      case overflow:
        isel(rt, ra, rb, encode_crbit(cr, CR_SO));
        break;
      case nooverflow:
        isel(rt, rb, ra, encode_crbit(cr, CR_SO));
        break;
      default:
        UNIMPLEMENTED();
    }
  }

  void b(Condition cond, Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    if (cond == al) {
      b(L, lk);
      return;
    }

    if ((L->is_bound() && is_near(L, cond)) || !is_trampoline_emitted()) {
      bc_short(cond, L, cr, lk);
      return;
    }

    Label skip;
    Condition neg_cond = NegateCondition(cond);
    bc_short(neg_cond, &skip, cr);
    b(L, lk);
    bind(&skip);
  }

  void bne(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(ne, L, cr, lk);
  }
  void beq(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(eq, L, cr, lk);
  }
  void blt(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(lt, L, cr, lk);
  }
  void bge(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(ge, L, cr, lk);
  }
  void ble(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(le, L, cr, lk);
  }
  void bgt(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(gt, L, cr, lk);
  }
  void bunordered(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(unordered, L, cr, lk);
  }
  void bordered(Label* L, CRegister cr = cr7, LKBit lk = LeaveLK) {
    b(ordered, L, cr, lk);
  }
  void boverflow(Label* L, CRegister cr = cr0, LKBit lk = LeaveLK) {
    b(overflow, L, cr, lk);
  }
  void bnooverflow(Label* L, CRegister cr = cr0, LKBit lk = LeaveLK) {
    b(nooverflow, L, cr, lk);
  }

  // Decrement CTR; branch if CTR != 0
  void bdnz(Label* L, LKBit lk = LeaveLK) {
    bc(branch_offset(L), DCBNZ, 0, lk);
  }

  // Data-processing instructions

  void sub(Register dst, Register src1, Register src2, OEBit s = LeaveOE,
           RCBit r = LeaveRC);

  void subc(Register dst, Register src1, Register src2, OEBit s = LeaveOE,
            RCBit r = LeaveRC);
  void sube(Register dst, Register src1, Register src2, OEBit s = LeaveOE,
            RCBit r = LeaveRC);

  void subfic(Register dst, Register src, const Operand& imm);

  void add(Register dst, Register src1, Register src2, OEBit s = LeaveOE,
           RCBit r = LeaveRC);

  void addc(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
            RCBit r = LeaveRC);
  void adde(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
            RCBit r = LeaveRC);
  void addze(Register dst, Register src1, OEBit o = LeaveOE, RCBit r = LeaveRC);

  void mullw(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
             RCBit r = LeaveRC);

  void mulhw(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void mulhwu(Register dst, Register src1, Register src2, RCBit r = LeaveRC);

  void divw(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
            RCBit r = LeaveRC);
  void divwu(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
             RCBit r = LeaveRC);

  void addi(Register dst, Register src, const Operand& imm);
  void addis(Register dst, Register src, const Operand& imm);
  void addic(Register dst, Register src, const Operand& imm);

  void and_(Register dst, Register src1, Register src2, RCBit rc = LeaveRC);
  void andc(Register dst, Register src1, Register src2, RCBit rc = LeaveRC);
  void andi(Register ra, Register rs, const Operand& imm);
  void andis(Register ra, Register rs, const Operand& imm);
  void nor(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void notx(Register dst, Register src, RCBit r = LeaveRC);
  void ori(Register dst, Register src, const Operand& imm);
  void oris(Register dst, Register src, const Operand& imm);
  void orx(Register dst, Register src1, Register src2, RCBit rc = LeaveRC);
  void orc(Register dst, Register src1, Register src2, RCBit rc = LeaveRC);
  void xori(Register dst, Register src, const Operand& imm);
  void xoris(Register ra, Register rs, const Operand& imm);
  void xor_(Register dst, Register src1, Register src2, RCBit rc = LeaveRC);
  void cmpi(Register src1, const Operand& src2, CRegister cr = cr7);
  void cmpli(Register src1, const Operand& src2, CRegister cr = cr7);
  void cmpwi(Register src1, const Operand& src2, CRegister cr = cr7);
  void cmplwi(Register src1, const Operand& src2, CRegister cr = cr7);
  void li(Register dst, const Operand& src);
  void lis(Register dst, const Operand& imm);
  void mr(Register dst, Register src);

  void lbz(Register dst, const MemOperand& src);
  void lbzx(Register dst, const MemOperand& src);
  void lbzux(Register dst, const MemOperand& src);
  void lhz(Register dst, const MemOperand& src);
  void lhzx(Register dst, const MemOperand& src);
  void lhzux(Register dst, const MemOperand& src);
  void lha(Register dst, const MemOperand& src);
  void lhax(Register dst, const MemOperand& src);
  void lwz(Register dst, const MemOperand& src);
  void lwzu(Register dst, const MemOperand& src);
  void lwzx(Register dst, const MemOperand& src);
  void lwzux(Register dst, const MemOperand& src);
  void lwa(Register dst, const MemOperand& src);
  void lwax(Register dst, const MemOperand& src);
  void ldbrx(Register dst, const MemOperand& src);
  void lwbrx(Register dst, const MemOperand& src);
  void lhbrx(Register dst, const MemOperand& src);
  void stb(Register dst, const MemOperand& src);
  void stbx(Register dst, const MemOperand& src);
  void stbux(Register dst, const MemOperand& src);
  void sth(Register dst, const MemOperand& src);
  void sthx(Register dst, const MemOperand& src);
  void sthux(Register dst, const MemOperand& src);
  void stw(Register dst, const MemOperand& src);
  void stwu(Register dst, const MemOperand& src);
  void stwx(Register rs, const MemOperand& src);
  void stwux(Register rs, const MemOperand& src);

  void extsb(Register rs, Register ra, RCBit r = LeaveRC);
  void extsh(Register rs, Register ra, RCBit r = LeaveRC);
  void extsw(Register rs, Register ra, RCBit r = LeaveRC);

  void neg(Register rt, Register ra, OEBit o = LeaveOE, RCBit c = LeaveRC);

#if V8_TARGET_ARCH_PPC64
  void ld(Register rd, const MemOperand& src);
  void ldx(Register rd, const MemOperand& src);
  void ldu(Register rd, const MemOperand& src);
  void ldux(Register rd, const MemOperand& src);
  void std(Register rs, const MemOperand& src);
  void stdx(Register rs, const MemOperand& src);
  void stdu(Register rs, const MemOperand& src);
  void stdux(Register rs, const MemOperand& src);
  void rldic(Register dst, Register src, int sh, int mb, RCBit r = LeaveRC);
  void rldicl(Register dst, Register src, int sh, int mb, RCBit r = LeaveRC);
  void rldcl(Register ra, Register rs, Register rb, int mb, RCBit r = LeaveRC);
  void rldicr(Register dst, Register src, int sh, int me, RCBit r = LeaveRC);
  void rldimi(Register dst, Register src, int sh, int mb, RCBit r = LeaveRC);
  void sldi(Register dst, Register src, const Operand& val, RCBit rc = LeaveRC);
  void srdi(Register dst, Register src, const Operand& val, RCBit rc = LeaveRC);
  void clrrdi(Register dst, Register src, const Operand& val,
              RCBit rc = LeaveRC);
  void clrldi(Register dst, Register src, const Operand& val,
              RCBit rc = LeaveRC);
  void sradi(Register ra, Register rs, int sh, RCBit r = LeaveRC);
  void srd(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void sld(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void srad(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void rotld(Register ra, Register rs, Register rb, RCBit r = LeaveRC);
  void rotldi(Register ra, Register rs, int sh, RCBit r = LeaveRC);
  void rotrdi(Register ra, Register rs, int sh, RCBit r = LeaveRC);
  void cntlzd_(Register dst, Register src, RCBit rc = LeaveRC);
  void popcntd(Register dst, Register src);
  void mulld(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
             RCBit r = LeaveRC);
  void divd(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
            RCBit r = LeaveRC);
  void divdu(Register dst, Register src1, Register src2, OEBit o = LeaveOE,
             RCBit r = LeaveRC);
#endif

  void rlwinm(Register ra, Register rs, int sh, int mb, int me,
              RCBit rc = LeaveRC);
  void rlwimi(Register ra, Register rs, int sh, int mb, int me,
              RCBit rc = LeaveRC);
  void rlwnm(Register ra, Register rs, Register rb, int mb, int me,
             RCBit rc = LeaveRC);
  void slwi(Register dst, Register src, const Operand& val, RCBit rc = LeaveRC);
  void srwi(Register dst, Register src, const Operand& val, RCBit rc = LeaveRC);
  void clrrwi(Register dst, Register src, const Operand& val,
              RCBit rc = LeaveRC);
  void clrlwi(Register dst, Register src, const Operand& val,
              RCBit rc = LeaveRC);
  void srawi(Register ra, Register rs, int sh, RCBit r = LeaveRC);
  void srw(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void slw(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void sraw(Register dst, Register src1, Register src2, RCBit r = LeaveRC);
  void rotlw(Register ra, Register rs, Register rb, RCBit r = LeaveRC);
  void rotlwi(Register ra, Register rs, int sh, RCBit r = LeaveRC);
  void rotrwi(Register ra, Register rs, int sh, RCBit r = LeaveRC);

  void cntlzw_(Register dst, Register src, RCBit rc = LeaveRC);
  void popcntw(Register dst, Register src);

  void subi(Register dst, Register src1, const Operand& src2);

  void cmp(Register src1, Register src2, CRegister cr = cr7);
  void cmpl(Register src1, Register src2, CRegister cr = cr7);
  void cmpw(Register src1, Register src2, CRegister cr = cr7);
  void cmplw(Register src1, Register src2, CRegister cr = cr7);

  void mov(Register dst, const Operand& src);
  void bitwise_mov(Register dst, intptr_t value);
  void bitwise_mov32(Register dst, int32_t value);
  void bitwise_add32(Register dst, Register src, int32_t value);

  // Load the position of the label relative to the generated code object
  // pointer in a register.
  void mov_label_offset(Register dst, Label* label);

  // dst = base + label position + delta
  void add_label_offset(Register dst, Register base, Label* label,
                        int delta = 0);

  // Load the address of the label in a register and associate with an
  // internal reference relocation.
  void mov_label_addr(Register dst, Label* label);

  // Emit the address of the label (i.e. a jump table entry) and associate with
  // an internal reference relocation.
  void emit_label_addr(Label* label);

  // Multiply instructions
  void mul(Register dst, Register src1, Register src2, OEBit s = LeaveOE,
           RCBit r = LeaveRC);

  // Miscellaneous arithmetic instructions

  // Special register access
  void crxor(int bt, int ba, int bb);
  void crclr(int bt) { crxor(bt, bt, bt); }
  void creqv(int bt, int ba, int bb);
  void crset(int bt) { creqv(bt, bt, bt); }
  void mflr(Register dst);
  void mtlr(Register src);
  void mtctr(Register src);
  void mtxer(Register src);
  void mcrfs(CRegister cr, FPSCRBit bit);
  void mfcr(Register dst);
#if V8_TARGET_ARCH_PPC64
  void mffprd(Register dst, DoubleRegister src);
  void mffprwz(Register dst, DoubleRegister src);
  void mtfprd(DoubleRegister dst, Register src);
  void mtfprwz(DoubleRegister dst, Register src);
  void mtfprwa(DoubleRegister dst, Register src);
#endif

  void function_descriptor();

  // Exception-generating instructions and debugging support
  void stop(const char* msg, Condition cond = al,
            int32_t code = kDefaultStopCode, CRegister cr = cr7);

  void bkpt(uint32_t imm16);  // v5 and above

  void dcbf(Register ra, Register rb);
  void sync();
  void lwsync();
  void icbi(Register ra, Register rb);
  void isync();

  // Support for floating point
  void lfd(const DoubleRegister frt, const MemOperand& src);
  void lfdu(const DoubleRegister frt, const MemOperand& src);
  void lfdx(const DoubleRegister frt, const MemOperand& src);
  void lfdux(const DoubleRegister frt, const MemOperand& src);
  void lfs(const DoubleRegister frt, const MemOperand& src);
  void lfsu(const DoubleRegister frt, const MemOperand& src);
  void lfsx(const DoubleRegister frt, const MemOperand& src);
  void lfsux(const DoubleRegister frt, const MemOperand& src);
  void stfd(const DoubleRegister frs, const MemOperand& src);
  void stfdu(const DoubleRegister frs, const MemOperand& src);
  void stfdx(const DoubleRegister frs, const MemOperand& src);
  void stfdux(const DoubleRegister frs, const MemOperand& src);
  void stfs(const DoubleRegister frs, const MemOperand& src);
  void stfsu(const DoubleRegister frs, const MemOperand& src);
  void stfsx(const DoubleRegister frs, const MemOperand& src);
  void stfsux(const DoubleRegister frs, const MemOperand& src);

  void fadd(const DoubleRegister frt, const DoubleRegister fra,
            const DoubleRegister frb, RCBit rc = LeaveRC);
  void fsub(const DoubleRegister frt, const DoubleRegister fra,
            const DoubleRegister frb, RCBit rc = LeaveRC);
  void fdiv(const DoubleRegister frt, const DoubleRegister fra,
            const DoubleRegister frb, RCBit rc = LeaveRC);
  void fmul(const DoubleRegister frt, const DoubleRegister fra,
            const DoubleRegister frc, RCBit rc = LeaveRC);
  void fcmpu(const DoubleRegister fra, const DoubleRegister frb,
             CRegister cr = cr7);
  void fmr(const DoubleRegister frt, const DoubleRegister frb,
           RCBit rc = LeaveRC);
  void fctiwz(const DoubleRegister frt, const DoubleRegister frb);
  void fctiw(const DoubleRegister frt, const DoubleRegister frb);
  void frin(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void friz(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void frip(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void frim(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void frsp(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void fcfid(const DoubleRegister frt, const DoubleRegister frb,
             RCBit rc = LeaveRC);
  void fcfidu(const DoubleRegister frt, const DoubleRegister frb,
              RCBit rc = LeaveRC);
  void fcfidus(const DoubleRegister frt, const DoubleRegister frb,
               RCBit rc = LeaveRC);
  void fcfids(const DoubleRegister frt, const DoubleRegister frb,
              RCBit rc = LeaveRC);
  void fctid(const DoubleRegister frt, const DoubleRegister frb,
             RCBit rc = LeaveRC);
  void fctidz(const DoubleRegister frt, const DoubleRegister frb,
              RCBit rc = LeaveRC);
  void fctidu(const DoubleRegister frt, const DoubleRegister frb,
              RCBit rc = LeaveRC);
  void fctiduz(const DoubleRegister frt, const DoubleRegister frb,
               RCBit rc = LeaveRC);
  void fsel(const DoubleRegister frt, const DoubleRegister fra,
            const DoubleRegister frc, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void fneg(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void mtfsb0(FPSCRBit bit, RCBit rc = LeaveRC);
  void mtfsb1(FPSCRBit bit, RCBit rc = LeaveRC);
  void mtfsfi(int bf, int immediate, RCBit rc = LeaveRC);
  void mffs(const DoubleRegister frt, RCBit rc = LeaveRC);
  void mtfsf(const DoubleRegister frb, bool L = 1, int FLM = 0, bool W = 0,
             RCBit rc = LeaveRC);
  void fsqrt(const DoubleRegister frt, const DoubleRegister frb,
             RCBit rc = LeaveRC);
  void fabs(const DoubleRegister frt, const DoubleRegister frb,
            RCBit rc = LeaveRC);
  void fmadd(const DoubleRegister frt, const DoubleRegister fra,
             const DoubleRegister frc, const DoubleRegister frb,
             RCBit rc = LeaveRC);
  void fmsub(const DoubleRegister frt, const DoubleRegister fra,
             const DoubleRegister frc, const DoubleRegister frb,
             RCBit rc = LeaveRC);

  // Pseudo instructions

  // Different nop operations are used by the code generator to detect certain
  // states of the generated code.
  enum NopMarkerTypes {
    NON_MARKING_NOP = 0,
    GROUP_ENDING_NOP,
    DEBUG_BREAK_NOP,
    // IC markers.
    PROPERTY_ACCESS_INLINED,
    PROPERTY_ACCESS_INLINED_CONTEXT,
    PROPERTY_ACCESS_INLINED_CONTEXT_DONT_DELETE,
    // Helper values.
    LAST_CODE_MARKER,
    FIRST_IC_MARKER = PROPERTY_ACCESS_INLINED
  };

  void nop(int type = 0);  // 0 is the default non-marking type.

  void push(Register src) {
#if V8_TARGET_ARCH_PPC64
    stdu(src, MemOperand(sp, -kPointerSize));
#else
    stwu(src, MemOperand(sp, -kPointerSize));
#endif
  }

  void pop(Register dst) {
#if V8_TARGET_ARCH_PPC64
    ld(dst, MemOperand(sp));
#else
    lwz(dst, MemOperand(sp));
#endif
    addi(sp, sp, Operand(kPointerSize));
  }

  void pop() { addi(sp, sp, Operand(kPointerSize)); }

  // Jump unconditionally to given label.
  void jmp(Label* L) { b(L); }

  // Check the code size generated from label to here.
  int SizeOfCodeGeneratedSince(Label* label) {
    return pc_offset() - label->pos();
  }

  // Check the number of instructions generated from label to here.
  int InstructionsGeneratedSince(Label* label) {
    return SizeOfCodeGeneratedSince(label) / kInstrSize;
  }

  // Class for scoping postponing the trampoline pool generation.
  class BlockTrampolinePoolScope {
   public:
    explicit BlockTrampolinePoolScope(Assembler* assem) : assem_(assem) {
      assem_->StartBlockTrampolinePool();
    }
    ~BlockTrampolinePoolScope() { assem_->EndBlockTrampolinePool(); }

   private:
    Assembler* assem_;

    DISALLOW_IMPLICIT_CONSTRUCTORS(BlockTrampolinePoolScope);
  };

  // Class for scoping disabling constant pool entry merging
  class BlockConstantPoolEntrySharingScope {
   public:
    explicit BlockConstantPoolEntrySharingScope(Assembler* assem)
        : assem_(assem) {
      assem_->StartBlockConstantPoolEntrySharing();
    }
    ~BlockConstantPoolEntrySharingScope() {
      assem_->EndBlockConstantPoolEntrySharing();
    }

   private:
    Assembler* assem_;

    DISALLOW_IMPLICIT_CONSTRUCTORS(BlockConstantPoolEntrySharingScope);
  };

  // Debugging

  // Mark generator continuation.
  void RecordGeneratorContinuation();

  // Mark address of a debug break slot.
  void RecordDebugBreakSlot(RelocInfo::Mode mode);

  // Record the AST id of the CallIC being compiled, so that it can be placed
  // in the relocation information.
  void SetRecordedAstId(TypeFeedbackId ast_id) {
    // Causes compiler to fail
    // DCHECK(recorded_ast_id_.IsNone());
    recorded_ast_id_ = ast_id;
  }

  TypeFeedbackId RecordedAstId() {
    // Causes compiler to fail
    // DCHECK(!recorded_ast_id_.IsNone());
    return recorded_ast_id_;
  }

  void ClearRecordedAstId() { recorded_ast_id_ = TypeFeedbackId::None(); }

  // Record a comment relocation entry that can be used by a disassembler.
  // Use --code-comments to enable.
  void RecordComment(const char* msg);

  // Record a deoptimization reason that can be used by a log or cpu profiler.
  // Use --trace-deopt to enable.
  void RecordDeoptReason(DeoptimizeReason reason, SourcePosition position,
                         int id);

  // Writes a single byte or word of data in the code stream.  Used
  // for inline tables, e.g., jump-tables.
  void db(uint8_t data);
  void dd(uint32_t data);
  void dq(uint64_t data);
  void dp(uintptr_t data);

  // Read/patch instructions
  Instr instr_at(int pos) { return *reinterpret_cast<Instr*>(buffer_ + pos); }
  void instr_at_put(int pos, Instr instr) {
    *reinterpret_cast<Instr*>(buffer_ + pos) = instr;
  }
  static Instr instr_at(byte* pc) { return *reinterpret_cast<Instr*>(pc); }
  static void instr_at_put(byte* pc, Instr instr) {
    *reinterpret_cast<Instr*>(pc) = instr;
  }
  static Condition GetCondition(Instr instr);

  static bool IsLis(Instr instr);
  static bool IsLi(Instr instr);
  static bool IsAddic(Instr instr);
  static bool IsOri(Instr instr);

  static bool IsBranch(Instr instr);
  static Register GetRA(Instr instr);
  static Register GetRB(Instr instr);
#if V8_TARGET_ARCH_PPC64
  static bool Is64BitLoadIntoR12(Instr instr1, Instr instr2, Instr instr3,
                                 Instr instr4, Instr instr5);
#else
  static bool Is32BitLoadIntoR12(Instr instr1, Instr instr2);
#endif

  static bool IsCmpRegister(Instr instr);
  static bool IsCmpImmediate(Instr instr);
  static bool IsRlwinm(Instr instr);
  static bool IsAndi(Instr instr);
#if V8_TARGET_ARCH_PPC64
  static bool IsRldicl(Instr instr);
#endif
  static bool IsCrSet(Instr instr);
  static Register GetCmpImmediateRegister(Instr instr);
  static int GetCmpImmediateRawImmediate(Instr instr);
  static bool IsNop(Instr instr, int type = NON_MARKING_NOP);

  // Postpone the generation of the trampoline pool for the specified number of
  // instructions.
  void BlockTrampolinePoolFor(int instructions);
  void CheckTrampolinePool();

  // For mov.  Return the number of actual instructions required to
  // load the operand into a register.  This can be anywhere from
  // one (constant pool small section) to five instructions (full
  // 64-bit sequence).
  //
  // The value returned is only valid as long as no entries are added to the
  // constant pool between this call and the actual instruction being emitted.
  int instructions_required_for_mov(Register dst, const Operand& src) const;

  // Decide between using the constant pool vs. a mov immediate sequence.
  bool use_constant_pool_for_mov(Register dst, const Operand& src,
                                 bool canOptimize) const;

  // The code currently calls CheckBuffer() too often. This has the side
  // effect of randomly growing the buffer in the middle of multi-instruction
  // sequences.
  //
  // This function allows outside callers to check and grow the buffer
  void EnsureSpaceFor(int space_needed);

  int EmitConstantPool() { return constant_pool_builder_.Emit(this); }

  bool ConstantPoolAccessIsInOverflow() const {
    return constant_pool_builder_.NextAccess(ConstantPoolEntry::INTPTR) ==
           ConstantPoolEntry::OVERFLOWED;
  }

  Label* ConstantPoolPosition() {
    return constant_pool_builder_.EmittedPosition();
  }

  void EmitRelocations();

 protected:
  // Relocation for a type-recording IC has the AST id added to it.  This
  // member variable is a way to pass the information from the call site to
  // the relocation info.
  TypeFeedbackId recorded_ast_id_;

  int buffer_space() const { return reloc_info_writer.pos() - pc_; }

  // Decode instruction(s) at pos and return backchain to previous
  // label reference or kEndOfChain.
  int target_at(int pos);

  // Patch instruction(s) at pos to target target_pos (e.g. branch)
  void target_at_put(int pos, int target_pos, bool* is_branch = nullptr);

  // Record reloc info for current pc_
  void RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data = 0);
  ConstantPoolEntry::Access ConstantPoolAddEntry(RelocInfo::Mode rmode,
                                                 intptr_t value) {
    bool sharing_ok = RelocInfo::IsNone(rmode) ||
                      !(serializer_enabled() || rmode < RelocInfo::CELL ||
                        is_constant_pool_entry_sharing_blocked());
    return constant_pool_builder_.AddEntry(pc_offset(), value, sharing_ok);
  }
  ConstantPoolEntry::Access ConstantPoolAddEntry(double value) {
    return constant_pool_builder_.AddEntry(pc_offset(), value);
  }

  // Block the emission of the trampoline pool before pc_offset.
  void BlockTrampolinePoolBefore(int pc_offset) {
    if (no_trampoline_pool_before_ < pc_offset)
      no_trampoline_pool_before_ = pc_offset;
  }

  void StartBlockTrampolinePool() { trampoline_pool_blocked_nesting_++; }
  void EndBlockTrampolinePool() {
    int count = --trampoline_pool_blocked_nesting_;
    if (count == 0) CheckTrampolinePoolQuick();
  }
  bool is_trampoline_pool_blocked() const {
    return trampoline_pool_blocked_nesting_ > 0;
  }

  void StartBlockConstantPoolEntrySharing() {
    constant_pool_entry_sharing_blocked_nesting_++;
  }
  void EndBlockConstantPoolEntrySharing() {
    constant_pool_entry_sharing_blocked_nesting_--;
  }
  bool is_constant_pool_entry_sharing_blocked() const {
    return constant_pool_entry_sharing_blocked_nesting_ > 0;
  }

  bool has_exception() const { return internal_trampoline_exception_; }

  bool is_trampoline_emitted() const { return trampoline_emitted_; }

 private:
  // Code generation
  // The relocation writer's position is at least kGap bytes below the end of
  // the generated instructions. This is so that multi-instruction sequences do
  // not have to check for overflow. The same is true for writes of large
  // relocation info entries.
  static const int kGap = 32;

  // Repeated checking whether the trampoline pool should be emitted is rather
  // expensive. By default we only check again once a number of instructions
  // has been generated.
  int next_trampoline_check_;  // pc offset of next buffer check.

  // Emission of the trampoline pool may be blocked in some code sequences.
  int trampoline_pool_blocked_nesting_;  // Block emission if this is not zero.
  int no_trampoline_pool_before_;  // Block emission before this pc offset.

  // Do not share constant pool entries.
  int constant_pool_entry_sharing_blocked_nesting_;

  // Relocation info generation
  // Each relocation is encoded as a variable size value
  static const int kMaxRelocSize = RelocInfoWriter::kMaxSize;
  RelocInfoWriter reloc_info_writer;
  std::vector<DeferredRelocInfo> relocations_;

  // The bound position, before this we cannot do instruction elimination.
  int last_bound_pos_;
  // Optimizable cmpi information.
  int optimizable_cmpi_pos_;
  CRegister cmpi_cr_;

  ConstantPoolBuilder constant_pool_builder_;

  // Code emission
  inline void CheckBuffer();
  void GrowBuffer(int needed = 0);
  inline void emit(Instr x);
  inline void TrackBranch();
  inline void UntrackBranch();
  inline void CheckTrampolinePoolQuick();

  // Instruction generation
  void a_form(Instr instr, DoubleRegister frt, DoubleRegister fra,
              DoubleRegister frb, RCBit r);
  void d_form(Instr instr, Register rt, Register ra, const intptr_t val,
              bool signed_disp);
  void x_form(Instr instr, Register ra, Register rs, Register rb, RCBit r);
  void xo_form(Instr instr, Register rt, Register ra, Register rb, OEBit o,
               RCBit r);
  void md_form(Instr instr, Register ra, Register rs, int shift, int maskbit,
               RCBit r);
  void mds_form(Instr instr, Register ra, Register rs, Register rb, int maskbit,
                RCBit r);

  // Labels
  void print(Label* L);
  int max_reach_from(int pos);
  void bind_to(Label* L, int pos);
  void next(Label* L);

  class Trampoline {
   public:
    Trampoline() {
      next_slot_ = 0;
      free_slot_count_ = 0;
    }
    Trampoline(int start, int slot_count) {
      next_slot_ = start;
      free_slot_count_ = slot_count;
    }
    int take_slot() {
      int trampoline_slot = kInvalidSlotPos;
      if (free_slot_count_ <= 0) {
        // We have run out of space on trampolines.
        // Make sure we fail in debug mode, so we become aware of each case
        // when this happens.
        DCHECK(0);
        // Internal exception will be caught.
      } else {
        trampoline_slot = next_slot_;
        free_slot_count_--;
        next_slot_ += kTrampolineSlotsSize;
      }
      return trampoline_slot;
    }

   private:
    int next_slot_;
    int free_slot_count_;
  };

  int32_t get_trampoline_entry();
  int tracked_branch_count_;
  // If trampoline is emitted, generated code is becoming large. As
  // this is already a slow case which can possibly break our code
  // generation for the extreme case, we use this information to
  // trigger different mode of branch instruction generation, where we
  // no longer use a single branch instruction.
  bool trampoline_emitted_;
  static const int kTrampolineSlotsSize = kInstrSize;
  static const int kMaxCondBranchReach = (1 << (16 - 1)) - 1;
  static const int kMaxBlockTrampolineSectionSize = 64 * kInstrSize;
  static const int kInvalidSlotPos = -1;

  Trampoline trampoline_;
  bool internal_trampoline_exception_;

  friend class RegExpMacroAssemblerPPC;
  friend class RelocInfo;
  friend class CodePatcher;
  friend class BlockTrampolinePoolScope;
  friend class EnsureSpace;
};


class EnsureSpace BASE_EMBEDDED {
 public:
  explicit EnsureSpace(Assembler* assembler) { assembler->CheckBuffer(); }
};
}  // namespace internal
}  // namespace v8

#endif  // V8_PPC_ASSEMBLER_PPC_H_