xref: /external/llvm/lib/Target/ARM/MCTargetDesc/ARMAddressingModes.h

//===-- ARMAddressingModes.h - ARM Addressing Modes -------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM addressing mode implementation stuff.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_ARM_ARMADDRESSINGMODES_H
#define LLVM_TARGET_ARM_ARMADDRESSINGMODES_H

#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include <cassert>

namespace llvm {

/// ARM_AM - ARM Addressing Mode Stuff
namespace ARM_AM {
  enum ShiftOpc {
    no_shift = 0,
    asr,
    lsl,
    lsr,
    ror,
    rrx
  };

  enum AddrOpc {
    sub = 0,
    add
  };

  static inline const char *getAddrOpcStr(AddrOpc Op) {
    return Op == sub ? "-" : "";
  }

  static inline const char *getShiftOpcStr(ShiftOpc Op) {
    switch (Op) {
    default: llvm_unreachable("Unknown shift opc!");
    case ARM_AM::asr: return "asr";
    case ARM_AM::lsl: return "lsl";
    case ARM_AM::lsr: return "lsr";
    case ARM_AM::ror: return "ror";
    case ARM_AM::rrx: return "rrx";
    }
  }

  static inline unsigned getShiftOpcEncoding(ShiftOpc Op) {
    switch (Op) {
    default: llvm_unreachable("Unknown shift opc!");
    case ARM_AM::asr: return 2;
    case ARM_AM::lsl: return 0;
    case ARM_AM::lsr: return 1;
    case ARM_AM::ror: return 3;
    }
  }

  enum AMSubMode {
    bad_am_submode = 0,
    ia,
    ib,
    da,
    db
  };

  static inline const char *getAMSubModeStr(AMSubMode Mode) {
    switch (Mode) {
    default: llvm_unreachable("Unknown addressing sub-mode!");
    case ARM_AM::ia: return "ia";
    case ARM_AM::ib: return "ib";
    case ARM_AM::da: return "da";
    case ARM_AM::db: return "db";
    }
  }

  /// rotr32 - Rotate a 32-bit unsigned value right by a specified # bits.
  ///
  static inline unsigned rotr32(unsigned Val, unsigned Amt) {
    assert(Amt < 32 && "Invalid rotate amount");
    return (Val >> Amt) | (Val << ((32-Amt)&31));
  }

  /// rotl32 - Rotate a 32-bit unsigned value left by a specified # bits.
  ///
  static inline unsigned rotl32(unsigned Val, unsigned Amt) {
    assert(Amt < 32 && "Invalid rotate amount");
    return (Val << Amt) | (Val >> ((32-Amt)&31));
  }

  //===--------------------------------------------------------------------===//
  // Addressing Mode #1: shift_operand with registers
  //===--------------------------------------------------------------------===//
  //
  // This 'addressing mode' is used for arithmetic instructions.  It can
  // represent things like:
  //   reg
  //   reg [asr|lsl|lsr|ror|rrx] reg
  //   reg [asr|lsl|lsr|ror|rrx] imm
  //
  // This is stored three operands [rega, regb, opc].  The first is the base
  // reg, the second is the shift amount (or reg0 if not present or imm).  The
  // third operand encodes the shift opcode and the imm if a reg isn't present.
  //
  static inline unsigned getSORegOpc(ShiftOpc ShOp, unsigned Imm) {
    return ShOp | (Imm << 3);
  }
  static inline unsigned getSORegOffset(unsigned Op) {
    return Op >> 3;
  }
  static inline ShiftOpc getSORegShOp(unsigned Op) {
    return (ShiftOpc)(Op & 7);
  }

  /// getSOImmValImm - Given an encoded imm field for the reg/imm form, return
  /// the 8-bit imm value.
  static inline unsigned getSOImmValImm(unsigned Imm) {
    return Imm & 0xFF;
  }
  /// getSOImmValRot - Given an encoded imm field for the reg/imm form, return
  /// the rotate amount.
  static inline unsigned getSOImmValRot(unsigned Imm) {
    return (Imm >> 8) * 2;
  }

  /// getSOImmValRotate - Try to handle Imm with an immediate shifter operand,
  /// computing the rotate amount to use.  If this immediate value cannot be
  /// handled with a single shifter-op, determine a good rotate amount that will
  /// take a maximal chunk of bits out of the immediate.
  static inline unsigned getSOImmValRotate(unsigned Imm) {
    // 8-bit (or less) immediates are trivially shifter_operands with a rotate
    // of zero.
    if ((Imm & ~255U) == 0) return 0;

    // Use CTZ to compute the rotate amount.
    unsigned TZ = CountTrailingZeros_32(Imm);

    // Rotate amount must be even.  Something like 0x200 must be rotated 8 bits,
    // not 9.
    unsigned RotAmt = TZ & ~1;

    // If we can handle this spread, return it.
    if ((rotr32(Imm, RotAmt) & ~255U) == 0)
      return (32-RotAmt)&31;  // HW rotates right, not left.

    // For values like 0xF000000F, we should ignore the low 6 bits, then
    // retry the hunt.
    if (Imm & 63U) {
      unsigned TZ2 = CountTrailingZeros_32(Imm & ~63U);
      unsigned RotAmt2 = TZ2 & ~1;
      if ((rotr32(Imm, RotAmt2) & ~255U) == 0)
        return (32-RotAmt2)&31;  // HW rotates right, not left.
    }

    // Otherwise, we have no way to cover this span of bits with a single
    // shifter_op immediate.  Return a chunk of bits that will be useful to
    // handle.
    return (32-RotAmt)&31;  // HW rotates right, not left.
  }

  /// getSOImmVal - Given a 32-bit immediate, if it is something that can fit
  /// into an shifter_operand immediate operand, return the 12-bit encoding for
  /// it.  If not, return -1.
  static inline int getSOImmVal(unsigned Arg) {
    // 8-bit (or less) immediates are trivially shifter_operands with a rotate
    // of zero.
    if ((Arg & ~255U) == 0) return Arg;

    unsigned RotAmt = getSOImmValRotate(Arg);

    // If this cannot be handled with a single shifter_op, bail out.
    if (rotr32(~255U, RotAmt) & Arg)
      return -1;

    // Encode this correctly.
    return rotl32(Arg, RotAmt) | ((RotAmt>>1) << 8);
  }

  /// isSOImmTwoPartVal - Return true if the specified value can be obtained by
  /// or'ing together two SOImmVal's.
  static inline bool isSOImmTwoPartVal(unsigned V) {
    // If this can be handled with a single shifter_op, bail out.
    V = rotr32(~255U, getSOImmValRotate(V)) & V;
    if (V == 0)
      return false;

    // If this can be handled with two shifter_op's, accept.
    V = rotr32(~255U, getSOImmValRotate(V)) & V;
    return V == 0;
  }

  /// getSOImmTwoPartFirst - If V is a value that satisfies isSOImmTwoPartVal,
  /// return the first chunk of it.
  static inline unsigned getSOImmTwoPartFirst(unsigned V) {
    return rotr32(255U, getSOImmValRotate(V)) & V;
  }

  /// getSOImmTwoPartSecond - If V is a value that satisfies isSOImmTwoPartVal,
  /// return the second chunk of it.
  static inline unsigned getSOImmTwoPartSecond(unsigned V) {
    // Mask out the first hunk.
    V = rotr32(~255U, getSOImmValRotate(V)) & V;

    // Take what's left.
    assert(V == (rotr32(255U, getSOImmValRotate(V)) & V));
    return V;
  }

  /// getThumbImmValShift - Try to handle Imm with a 8-bit immediate followed
  /// by a left shift. Returns the shift amount to use.
  static inline unsigned getThumbImmValShift(unsigned Imm) {
    // 8-bit (or less) immediates are trivially immediate operand with a shift
    // of zero.
    if ((Imm & ~255U) == 0) return 0;

    // Use CTZ to compute the shift amount.
    return CountTrailingZeros_32(Imm);
  }

  /// isThumbImmShiftedVal - Return true if the specified value can be obtained
  /// by left shifting a 8-bit immediate.
  static inline bool isThumbImmShiftedVal(unsigned V) {
    // If this can be handled with
    V = (~255U << getThumbImmValShift(V)) & V;
    return V == 0;
  }

  /// getThumbImm16ValShift - Try to handle Imm with a 16-bit immediate followed
  /// by a left shift. Returns the shift amount to use.
  static inline unsigned getThumbImm16ValShift(unsigned Imm) {
    // 16-bit (or less) immediates are trivially immediate operand with a shift
    // of zero.
    if ((Imm & ~65535U) == 0) return 0;

    // Use CTZ to compute the shift amount.
    return CountTrailingZeros_32(Imm);
  }

  /// isThumbImm16ShiftedVal - Return true if the specified value can be
  /// obtained by left shifting a 16-bit immediate.
  static inline bool isThumbImm16ShiftedVal(unsigned V) {
    // If this can be handled with
    V = (~65535U << getThumbImm16ValShift(V)) & V;
    return V == 0;
  }

  /// getThumbImmNonShiftedVal - If V is a value that satisfies
  /// isThumbImmShiftedVal, return the non-shiftd value.
  static inline unsigned getThumbImmNonShiftedVal(unsigned V) {
    return V >> getThumbImmValShift(V);
  }


  /// getT2SOImmValSplat - Return the 12-bit encoded representation
  /// if the specified value can be obtained by splatting the low 8 bits
  /// into every other byte or every byte of a 32-bit value. i.e.,
  ///     00000000 00000000 00000000 abcdefgh    control = 0
  ///     00000000 abcdefgh 00000000 abcdefgh    control = 1
  ///     abcdefgh 00000000 abcdefgh 00000000    control = 2
  ///     abcdefgh abcdefgh abcdefgh abcdefgh    control = 3
  /// Return -1 if none of the above apply.
  /// See ARM Reference Manual A6.3.2.
  static inline int getT2SOImmValSplatVal(unsigned V) {
    unsigned u, Vs, Imm;
    // control = 0
    if ((V & 0xffffff00) == 0)
      return V;

    // If the value is zeroes in the first byte, just shift those off
    Vs = ((V & 0xff) == 0) ? V >> 8 : V;
    // Any passing value only has 8 bits of payload, splatted across the word
    Imm = Vs & 0xff;
    // Likewise, any passing values have the payload splatted into the 3rd byte
    u = Imm | (Imm << 16);

    // control = 1 or 2
    if (Vs == u)
      return (((Vs == V) ? 1 : 2) << 8) | Imm;

    // control = 3
    if (Vs == (u | (u << 8)))
      return (3 << 8) | Imm;

    return -1;
  }

  /// getT2SOImmValRotateVal - Return the 12-bit encoded representation if the
  /// specified value is a rotated 8-bit value. Return -1 if no rotation
  /// encoding is possible.
  /// See ARM Reference Manual A6.3.2.
  static inline int getT2SOImmValRotateVal(unsigned V) {
    unsigned RotAmt = CountLeadingZeros_32(V);
    if (RotAmt >= 24)
      return -1;

    // If 'Arg' can be handled with a single shifter_op return the value.
    if ((rotr32(0xff000000U, RotAmt) & V) == V)
      return (rotr32(V, 24 - RotAmt) & 0x7f) | ((RotAmt + 8) << 7);

    return -1;
  }

  /// getT2SOImmVal - Given a 32-bit immediate, if it is something that can fit
  /// into a Thumb-2 shifter_operand immediate operand, return the 12-bit
  /// encoding for it.  If not, return -1.
  /// See ARM Reference Manual A6.3.2.
  static inline int getT2SOImmVal(unsigned Arg) {
    // If 'Arg' is an 8-bit splat, then get the encoded value.
    int Splat = getT2SOImmValSplatVal(Arg);
    if (Splat != -1)
      return Splat;

    // If 'Arg' can be handled with a single shifter_op return the value.
    int Rot = getT2SOImmValRotateVal(Arg);
    if (Rot != -1)
      return Rot;

    return -1;
  }

  static inline unsigned getT2SOImmValRotate(unsigned V) {
    if ((V & ~255U) == 0) return 0;
    // Use CTZ to compute the rotate amount.
    unsigned RotAmt = CountTrailingZeros_32(V);
    return (32 - RotAmt) & 31;
  }

  static inline bool isT2SOImmTwoPartVal (unsigned Imm) {
    unsigned V = Imm;
    // Passing values can be any combination of splat values and shifter
    // values. If this can be handled with a single shifter or splat, bail
    // out. Those should be handled directly, not with a two-part val.
    if (getT2SOImmValSplatVal(V) != -1)
      return false;
    V = rotr32 (~255U, getT2SOImmValRotate(V)) & V;
    if (V == 0)
      return false;

    // If this can be handled as an immediate, accept.
    if (getT2SOImmVal(V) != -1) return true;

    // Likewise, try masking out a splat value first.
    V = Imm;
    if (getT2SOImmValSplatVal(V & 0xff00ff00U) != -1)
      V &= ~0xff00ff00U;
    else if (getT2SOImmValSplatVal(V & 0x00ff00ffU) != -1)
      V &= ~0x00ff00ffU;
    // If what's left can be handled as an immediate, accept.
    if (getT2SOImmVal(V) != -1) return true;

    // Otherwise, do not accept.
    return false;
  }

  static inline unsigned getT2SOImmTwoPartFirst(unsigned Imm) {
    assert (isT2SOImmTwoPartVal(Imm) &&
            "Immedate cannot be encoded as two part immediate!");
    // Try a shifter operand as one part
    unsigned V = rotr32 (~255, getT2SOImmValRotate(Imm)) & Imm;
    // If the rest is encodable as an immediate, then return it.
    if (getT2SOImmVal(V) != -1) return V;

    // Try masking out a splat value first.
    if (getT2SOImmValSplatVal(Imm & 0xff00ff00U) != -1)
      return Imm & 0xff00ff00U;

    // The other splat is all that's left as an option.
    assert (getT2SOImmValSplatVal(Imm & 0x00ff00ffU) != -1);
    return Imm & 0x00ff00ffU;
  }

  static inline unsigned getT2SOImmTwoPartSecond(unsigned Imm) {
    // Mask out the first hunk
    Imm ^= getT2SOImmTwoPartFirst(Imm);
    // Return what's left
    assert (getT2SOImmVal(Imm) != -1 &&
            "Unable to encode second part of T2 two part SO immediate");
    return Imm;
  }


  //===--------------------------------------------------------------------===//
  // Addressing Mode #2
  //===--------------------------------------------------------------------===//
  //
  // This is used for most simple load/store instructions.
  //
  // addrmode2 := reg +/- reg shop imm
  // addrmode2 := reg +/- imm12
  //
  // The first operand is always a Reg.  The second operand is a reg if in
  // reg/reg form, otherwise it's reg#0.  The third field encodes the operation
  // in bit 12, the immediate in bits 0-11, and the shift op in 13-15. The
  // fourth operand 16-17 encodes the index mode.
  //
  // If this addressing mode is a frame index (before prolog/epilog insertion
  // and code rewriting), this operand will have the form:  FI#, reg0, <offs>
  // with no shift amount for the frame offset.
  //
  static inline unsigned getAM2Opc(AddrOpc Opc, unsigned Imm12, ShiftOpc SO,
                                   unsigned IdxMode = 0) {
    assert(Imm12 < (1 << 12) && "Imm too large!");
    bool isSub = Opc == sub;
    return Imm12 | ((int)isSub << 12) | (SO << 13) | (IdxMode << 16) ;
  }
  static inline unsigned getAM2Offset(unsigned AM2Opc) {
    return AM2Opc & ((1 << 12)-1);
  }
  static inline AddrOpc getAM2Op(unsigned AM2Opc) {
    return ((AM2Opc >> 12) & 1) ? sub : add;
  }
  static inline ShiftOpc getAM2ShiftOpc(unsigned AM2Opc) {
    return (ShiftOpc)((AM2Opc >> 13) & 7);
  }
  static inline unsigned getAM2IdxMode(unsigned AM2Opc) {
    return (AM2Opc >> 16);
  }


  //===--------------------------------------------------------------------===//
  // Addressing Mode #3
  //===--------------------------------------------------------------------===//
  //
  // This is used for sign-extending loads, and load/store-pair instructions.
  //
  // addrmode3 := reg +/- reg
  // addrmode3 := reg +/- imm8
  //
  // The first operand is always a Reg.  The second operand is a reg if in
  // reg/reg form, otherwise it's reg#0.  The third field encodes the operation
  // in bit 8, the immediate in bits 0-7. The fourth operand 9-10 encodes the
  // index mode.

  /// getAM3Opc - This function encodes the addrmode3 opc field.
  static inline unsigned getAM3Opc(AddrOpc Opc, unsigned char Offset,
                                   unsigned IdxMode = 0) {
    bool isSub = Opc == sub;
    return ((int)isSub << 8) | Offset | (IdxMode << 9);
  }
  static inline unsigned char getAM3Offset(unsigned AM3Opc) {
    return AM3Opc & 0xFF;
  }
  static inline AddrOpc getAM3Op(unsigned AM3Opc) {
    return ((AM3Opc >> 8) & 1) ? sub : add;
  }
  static inline unsigned getAM3IdxMode(unsigned AM3Opc) {
    return (AM3Opc >> 9);
  }

  //===--------------------------------------------------------------------===//
  // Addressing Mode #4
  //===--------------------------------------------------------------------===//
  //
  // This is used for load / store multiple instructions.
  //
  // addrmode4 := reg, <mode>
  //
  // The four modes are:
  //    IA - Increment after
  //    IB - Increment before
  //    DA - Decrement after
  //    DB - Decrement before
  // For VFP instructions, only the IA and DB modes are valid.

  static inline AMSubMode getAM4SubMode(unsigned Mode) {
    return (AMSubMode)(Mode & 0x7);
  }

  static inline unsigned getAM4ModeImm(AMSubMode SubMode) {
    return (int)SubMode;
  }

  //===--------------------------------------------------------------------===//
  // Addressing Mode #5
  //===--------------------------------------------------------------------===//
  //
  // This is used for coprocessor instructions, such as FP load/stores.
  //
  // addrmode5 := reg +/- imm8*4
  //
  // The first operand is always a Reg.  The second operand encodes the
  // operation in bit 8 and the immediate in bits 0-7.

  /// getAM5Opc - This function encodes the addrmode5 opc field.
  static inline unsigned getAM5Opc(AddrOpc Opc, unsigned char Offset) {
    bool isSub = Opc == sub;
    return ((int)isSub << 8) | Offset;
  }
  static inline unsigned char getAM5Offset(unsigned AM5Opc) {
    return AM5Opc & 0xFF;
  }
  static inline AddrOpc getAM5Op(unsigned AM5Opc) {
    return ((AM5Opc >> 8) & 1) ? sub : add;
  }

  //===--------------------------------------------------------------------===//
  // Addressing Mode #6
  //===--------------------------------------------------------------------===//
  //
  // This is used for NEON load / store instructions.
  //
  // addrmode6 := reg with optional alignment
  //
  // This is stored in two operands [regaddr, align].  The first is the
  // address register.  The second operand is the value of the alignment
  // specifier in bytes or zero if no explicit alignment.
  // Valid alignments depend on the specific instruction.

  //===--------------------------------------------------------------------===//
  // NEON Modified Immediates
  //===--------------------------------------------------------------------===//
  //
  // Several NEON instructions (e.g., VMOV) take a "modified immediate"
  // vector operand, where a small immediate encoded in the instruction
  // specifies a full NEON vector value.  These modified immediates are
  // represented here as encoded integers.  The low 8 bits hold the immediate
  // value; bit 12 holds the "Op" field of the instruction, and bits 11-8 hold
  // the "Cmode" field of the instruction.  The interfaces below treat the
  // Op and Cmode values as a single 5-bit value.

  static inline unsigned createNEONModImm(unsigned OpCmode, unsigned Val) {
    return (OpCmode << 8) | Val;
  }
  static inline unsigned getNEONModImmOpCmode(unsigned ModImm) {
    return (ModImm >> 8) & 0x1f;
  }
  static inline unsigned getNEONModImmVal(unsigned ModImm) {
    return ModImm & 0xff;
  }

  /// decodeNEONModImm - Decode a NEON modified immediate value into the
  /// element value and the element size in bits.  (If the element size is
  /// smaller than the vector, it is splatted into all the elements.)
  static inline uint64_t decodeNEONModImm(unsigned ModImm, unsigned &EltBits) {
    unsigned OpCmode = getNEONModImmOpCmode(ModImm);
    unsigned Imm8 = getNEONModImmVal(ModImm);
    uint64_t Val = 0;

    if (OpCmode == 0xe) {
      // 8-bit vector elements
      Val = Imm8;
      EltBits = 8;
    } else if ((OpCmode & 0xc) == 0x8) {
      // 16-bit vector elements
      unsigned ByteNum = (OpCmode & 0x6) >> 1;
      Val = Imm8 << (8 * ByteNum);
      EltBits = 16;
    } else if ((OpCmode & 0x8) == 0) {
      // 32-bit vector elements, zero with one byte set
      unsigned ByteNum = (OpCmode & 0x6) >> 1;
      Val = Imm8 << (8 * ByteNum);
      EltBits = 32;
    } else if ((OpCmode & 0xe) == 0xc) {
      // 32-bit vector elements, one byte with low bits set
      unsigned ByteNum = 1 + (OpCmode & 0x1);
      Val = (Imm8 << (8 * ByteNum)) | (0xffff >> (8 * (2 - ByteNum)));
      EltBits = 32;
    } else if (OpCmode == 0x1e) {
      // 64-bit vector elements
      for (unsigned ByteNum = 0; ByteNum < 8; ++ByteNum) {
        if ((ModImm >> ByteNum) & 1)
          Val |= (uint64_t)0xff << (8 * ByteNum);
      }
      EltBits = 64;
    } else {
      llvm_unreachable("Unsupported NEON immediate");
    }
    return Val;
  }

  AMSubMode getLoadStoreMultipleSubMode(int Opcode);

  //===--------------------------------------------------------------------===//
  // Floating-point Immediates
  //
  static inline float getFPImmFloat(unsigned Imm) {
    // We expect an 8-bit binary encoding of a floating-point number here.
    union {
      uint32_t I;
      float F;
    } FPUnion;

    uint8_t Sign = (Imm >> 7) & 0x1;
    uint8_t Exp = (Imm >> 4) & 0x7;
    uint8_t Mantissa = Imm & 0xf;

    //   8-bit FP    iEEEE Float Encoding
    //   abcd efgh   aBbbbbbc defgh000 00000000 00000000
    //
    // where B = NOT(b);

    FPUnion.I = 0;
    FPUnion.I |= Sign << 31;
    FPUnion.I |= ((Exp & 0x4) != 0 ? 0 : 1) << 30;
    FPUnion.I |= ((Exp & 0x4) != 0 ? 0x1f : 0) << 25;
    FPUnion.I |= (Exp & 0x3) << 23;
    FPUnion.I |= Mantissa << 19;
    return FPUnion.F;
  }

  /// getFP32Imm - Return an 8-bit floating-point version of the 32-bit
  /// floating-point value. If the value cannot be represented as an 8-bit
  /// floating-point value, then return -1.
  static inline int getFP32Imm(const APInt &Imm) {
    uint32_t Sign = Imm.lshr(31).getZExtValue() & 1;
    int32_t Exp = (Imm.lshr(23).getSExtValue() & 0xff) - 127;  // -126 to 127
    int64_t Mantissa = Imm.getZExtValue() & 0x7fffff;  // 23 bits

    // We can handle 4 bits of mantissa.
    // mantissa = (16+UInt(e:f:g:h))/16.
    if (Mantissa & 0x7ffff)
      return -1;
    Mantissa >>= 19;
    if ((Mantissa & 0xf) != Mantissa)
      return -1;

    // We can handle 3 bits of exponent: exp == UInt(NOT(b):c:d)-3
    if (Exp < -3 || Exp > 4)
      return -1;
    Exp = ((Exp+3) & 0x7) ^ 4;

    return ((int)Sign << 7) | (Exp << 4) | Mantissa;
  }

  static inline int getFP32Imm(const APFloat &FPImm) {
    return getFP32Imm(FPImm.bitcastToAPInt());
  }

  /// getFP64Imm - Return an 8-bit floating-point version of the 64-bit
  /// floating-point value. If the value cannot be represented as an 8-bit
  /// floating-point value, then return -1.
  static inline int getFP64Imm(const APInt &Imm) {
    uint64_t Sign = Imm.lshr(63).getZExtValue() & 1;
    int64_t Exp = (Imm.lshr(52).getSExtValue() & 0x7ff) - 1023; // -1022 to 1023
    uint64_t Mantissa = Imm.getZExtValue() & 0xfffffffffffffULL;

    // We can handle 4 bits of mantissa.
    // mantissa = (16+UInt(e:f:g:h))/16.
    if (Mantissa & 0xffffffffffffULL)
      return -1;
    Mantissa >>= 48;
    if ((Mantissa & 0xf) != Mantissa)
      return -1;

    // We can handle 3 bits of exponent: exp == UInt(NOT(b):c:d)-3
    if (Exp < -3 || Exp > 4)
      return -1;
    Exp = ((Exp+3) & 0x7) ^ 4;

    return ((int)Sign << 7) | (Exp << 4) | Mantissa;
  }

  static inline int getFP64Imm(const APFloat &FPImm) {
    return getFP64Imm(FPImm.bitcastToAPInt());
  }

} // end namespace ARM_AM
} // end namespace llvm

#endif