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      1 //===-- ARMAddressingModes.h - ARM Addressing Modes -------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains the ARM addressing mode implementation stuff.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_TARGET_ARM_ARMADDRESSINGMODES_H
     15 #define LLVM_TARGET_ARM_ARMADDRESSINGMODES_H
     16 
     17 #include "llvm/ADT/APFloat.h"
     18 #include "llvm/ADT/APInt.h"
     19 #include "llvm/Support/ErrorHandling.h"
     20 #include "llvm/Support/MathExtras.h"
     21 #include <cassert>
     22 
     23 namespace llvm {
     24 
     25 /// ARM_AM - ARM Addressing Mode Stuff
     26 namespace ARM_AM {
     27   enum ShiftOpc {
     28     no_shift = 0,
     29     asr,
     30     lsl,
     31     lsr,
     32     ror,
     33     rrx
     34   };
     35 
     36   enum AddrOpc {
     37     sub = 0,
     38     add
     39   };
     40 
     41   static inline const char *getAddrOpcStr(AddrOpc Op) {
     42     return Op == sub ? "-" : "";
     43   }
     44 
     45   static inline const char *getShiftOpcStr(ShiftOpc Op) {
     46     switch (Op) {
     47     default: llvm_unreachable("Unknown shift opc!");
     48     case ARM_AM::asr: return "asr";
     49     case ARM_AM::lsl: return "lsl";
     50     case ARM_AM::lsr: return "lsr";
     51     case ARM_AM::ror: return "ror";
     52     case ARM_AM::rrx: return "rrx";
     53     }
     54   }
     55 
     56   static inline unsigned getShiftOpcEncoding(ShiftOpc Op) {
     57     switch (Op) {
     58     default: llvm_unreachable("Unknown shift opc!");
     59     case ARM_AM::asr: return 2;
     60     case ARM_AM::lsl: return 0;
     61     case ARM_AM::lsr: return 1;
     62     case ARM_AM::ror: return 3;
     63     }
     64   }
     65 
     66   enum AMSubMode {
     67     bad_am_submode = 0,
     68     ia,
     69     ib,
     70     da,
     71     db
     72   };
     73 
     74   static inline const char *getAMSubModeStr(AMSubMode Mode) {
     75     switch (Mode) {
     76     default: llvm_unreachable("Unknown addressing sub-mode!");
     77     case ARM_AM::ia: return "ia";
     78     case ARM_AM::ib: return "ib";
     79     case ARM_AM::da: return "da";
     80     case ARM_AM::db: return "db";
     81     }
     82   }
     83 
     84   /// rotr32 - Rotate a 32-bit unsigned value right by a specified # bits.
     85   ///
     86   static inline unsigned rotr32(unsigned Val, unsigned Amt) {
     87     assert(Amt < 32 && "Invalid rotate amount");
     88     return (Val >> Amt) | (Val << ((32-Amt)&31));
     89   }
     90 
     91   /// rotl32 - Rotate a 32-bit unsigned value left by a specified # bits.
     92   ///
     93   static inline unsigned rotl32(unsigned Val, unsigned Amt) {
     94     assert(Amt < 32 && "Invalid rotate amount");
     95     return (Val << Amt) | (Val >> ((32-Amt)&31));
     96   }
     97 
     98   //===--------------------------------------------------------------------===//
     99   // Addressing Mode #1: shift_operand with registers
    100   //===--------------------------------------------------------------------===//
    101   //
    102   // This 'addressing mode' is used for arithmetic instructions.  It can
    103   // represent things like:
    104   //   reg
    105   //   reg [asr|lsl|lsr|ror|rrx] reg
    106   //   reg [asr|lsl|lsr|ror|rrx] imm
    107   //
    108   // This is stored three operands [rega, regb, opc].  The first is the base
    109   // reg, the second is the shift amount (or reg0 if not present or imm).  The
    110   // third operand encodes the shift opcode and the imm if a reg isn't present.
    111   //
    112   static inline unsigned getSORegOpc(ShiftOpc ShOp, unsigned Imm) {
    113     return ShOp | (Imm << 3);
    114   }
    115   static inline unsigned getSORegOffset(unsigned Op) {
    116     return Op >> 3;
    117   }
    118   static inline ShiftOpc getSORegShOp(unsigned Op) {
    119     return (ShiftOpc)(Op & 7);
    120   }
    121 
    122   /// getSOImmValImm - Given an encoded imm field for the reg/imm form, return
    123   /// the 8-bit imm value.
    124   static inline unsigned getSOImmValImm(unsigned Imm) {
    125     return Imm & 0xFF;
    126   }
    127   /// getSOImmValRot - Given an encoded imm field for the reg/imm form, return
    128   /// the rotate amount.
    129   static inline unsigned getSOImmValRot(unsigned Imm) {
    130     return (Imm >> 8) * 2;
    131   }
    132 
    133   /// getSOImmValRotate - Try to handle Imm with an immediate shifter operand,
    134   /// computing the rotate amount to use.  If this immediate value cannot be
    135   /// handled with a single shifter-op, determine a good rotate amount that will
    136   /// take a maximal chunk of bits out of the immediate.
    137   static inline unsigned getSOImmValRotate(unsigned Imm) {
    138     // 8-bit (or less) immediates are trivially shifter_operands with a rotate
    139     // of zero.
    140     if ((Imm & ~255U) == 0) return 0;
    141 
    142     // Use CTZ to compute the rotate amount.
    143     unsigned TZ = countTrailingZeros(Imm);
    144 
    145     // Rotate amount must be even.  Something like 0x200 must be rotated 8 bits,
    146     // not 9.
    147     unsigned RotAmt = TZ & ~1;
    148 
    149     // If we can handle this spread, return it.
    150     if ((rotr32(Imm, RotAmt) & ~255U) == 0)
    151       return (32-RotAmt)&31;  // HW rotates right, not left.
    152 
    153     // For values like 0xF000000F, we should ignore the low 6 bits, then
    154     // retry the hunt.
    155     if (Imm & 63U) {
    156       unsigned TZ2 = countTrailingZeros(Imm & ~63U);
    157       unsigned RotAmt2 = TZ2 & ~1;
    158       if ((rotr32(Imm, RotAmt2) & ~255U) == 0)
    159         return (32-RotAmt2)&31;  // HW rotates right, not left.
    160     }
    161 
    162     // Otherwise, we have no way to cover this span of bits with a single
    163     // shifter_op immediate.  Return a chunk of bits that will be useful to
    164     // handle.
    165     return (32-RotAmt)&31;  // HW rotates right, not left.
    166   }
    167 
    168   /// getSOImmVal - Given a 32-bit immediate, if it is something that can fit
    169   /// into an shifter_operand immediate operand, return the 12-bit encoding for
    170   /// it.  If not, return -1.
    171   static inline int getSOImmVal(unsigned Arg) {
    172     // 8-bit (or less) immediates are trivially shifter_operands with a rotate
    173     // of zero.
    174     if ((Arg & ~255U) == 0) return Arg;
    175 
    176     unsigned RotAmt = getSOImmValRotate(Arg);
    177 
    178     // If this cannot be handled with a single shifter_op, bail out.
    179     if (rotr32(~255U, RotAmt) & Arg)
    180       return -1;
    181 
    182     // Encode this correctly.
    183     return rotl32(Arg, RotAmt) | ((RotAmt>>1) << 8);
    184   }
    185 
    186   /// isSOImmTwoPartVal - Return true if the specified value can be obtained by
    187   /// or'ing together two SOImmVal's.
    188   static inline bool isSOImmTwoPartVal(unsigned V) {
    189     // If this can be handled with a single shifter_op, bail out.
    190     V = rotr32(~255U, getSOImmValRotate(V)) & V;
    191     if (V == 0)
    192       return false;
    193 
    194     // If this can be handled with two shifter_op's, accept.
    195     V = rotr32(~255U, getSOImmValRotate(V)) & V;
    196     return V == 0;
    197   }
    198 
    199   /// getSOImmTwoPartFirst - If V is a value that satisfies isSOImmTwoPartVal,
    200   /// return the first chunk of it.
    201   static inline unsigned getSOImmTwoPartFirst(unsigned V) {
    202     return rotr32(255U, getSOImmValRotate(V)) & V;
    203   }
    204 
    205   /// getSOImmTwoPartSecond - If V is a value that satisfies isSOImmTwoPartVal,
    206   /// return the second chunk of it.
    207   static inline unsigned getSOImmTwoPartSecond(unsigned V) {
    208     // Mask out the first hunk.
    209     V = rotr32(~255U, getSOImmValRotate(V)) & V;
    210 
    211     // Take what's left.
    212     assert(V == (rotr32(255U, getSOImmValRotate(V)) & V));
    213     return V;
    214   }
    215 
    216   /// getThumbImmValShift - Try to handle Imm with a 8-bit immediate followed
    217   /// by a left shift. Returns the shift amount to use.
    218   static inline unsigned getThumbImmValShift(unsigned Imm) {
    219     // 8-bit (or less) immediates are trivially immediate operand with a shift
    220     // of zero.
    221     if ((Imm & ~255U) == 0) return 0;
    222 
    223     // Use CTZ to compute the shift amount.
    224     return countTrailingZeros(Imm);
    225   }
    226 
    227   /// isThumbImmShiftedVal - Return true if the specified value can be obtained
    228   /// by left shifting a 8-bit immediate.
    229   static inline bool isThumbImmShiftedVal(unsigned V) {
    230     // If this can be handled with
    231     V = (~255U << getThumbImmValShift(V)) & V;
    232     return V == 0;
    233   }
    234 
    235   /// getThumbImm16ValShift - Try to handle Imm with a 16-bit immediate followed
    236   /// by a left shift. Returns the shift amount to use.
    237   static inline unsigned getThumbImm16ValShift(unsigned Imm) {
    238     // 16-bit (or less) immediates are trivially immediate operand with a shift
    239     // of zero.
    240     if ((Imm & ~65535U) == 0) return 0;
    241 
    242     // Use CTZ to compute the shift amount.
    243     return countTrailingZeros(Imm);
    244   }
    245 
    246   /// isThumbImm16ShiftedVal - Return true if the specified value can be
    247   /// obtained by left shifting a 16-bit immediate.
    248   static inline bool isThumbImm16ShiftedVal(unsigned V) {
    249     // If this can be handled with
    250     V = (~65535U << getThumbImm16ValShift(V)) & V;
    251     return V == 0;
    252   }
    253 
    254   /// getThumbImmNonShiftedVal - If V is a value that satisfies
    255   /// isThumbImmShiftedVal, return the non-shiftd value.
    256   static inline unsigned getThumbImmNonShiftedVal(unsigned V) {
    257     return V >> getThumbImmValShift(V);
    258   }
    259 
    260 
    261   /// getT2SOImmValSplat - Return the 12-bit encoded representation
    262   /// if the specified value can be obtained by splatting the low 8 bits
    263   /// into every other byte or every byte of a 32-bit value. i.e.,
    264   ///     00000000 00000000 00000000 abcdefgh    control = 0
    265   ///     00000000 abcdefgh 00000000 abcdefgh    control = 1
    266   ///     abcdefgh 00000000 abcdefgh 00000000    control = 2
    267   ///     abcdefgh abcdefgh abcdefgh abcdefgh    control = 3
    268   /// Return -1 if none of the above apply.
    269   /// See ARM Reference Manual A6.3.2.
    270   static inline int getT2SOImmValSplatVal(unsigned V) {
    271     unsigned u, Vs, Imm;
    272     // control = 0
    273     if ((V & 0xffffff00) == 0)
    274       return V;
    275 
    276     // If the value is zeroes in the first byte, just shift those off
    277     Vs = ((V & 0xff) == 0) ? V >> 8 : V;
    278     // Any passing value only has 8 bits of payload, splatted across the word
    279     Imm = Vs & 0xff;
    280     // Likewise, any passing values have the payload splatted into the 3rd byte
    281     u = Imm | (Imm << 16);
    282 
    283     // control = 1 or 2
    284     if (Vs == u)
    285       return (((Vs == V) ? 1 : 2) << 8) | Imm;
    286 
    287     // control = 3
    288     if (Vs == (u | (u << 8)))
    289       return (3 << 8) | Imm;
    290 
    291     return -1;
    292   }
    293 
    294   /// getT2SOImmValRotateVal - Return the 12-bit encoded representation if the
    295   /// specified value is a rotated 8-bit value. Return -1 if no rotation
    296   /// encoding is possible.
    297   /// See ARM Reference Manual A6.3.2.
    298   static inline int getT2SOImmValRotateVal(unsigned V) {
    299     unsigned RotAmt = countLeadingZeros(V);
    300     if (RotAmt >= 24)
    301       return -1;
    302 
    303     // If 'Arg' can be handled with a single shifter_op return the value.
    304     if ((rotr32(0xff000000U, RotAmt) & V) == V)
    305       return (rotr32(V, 24 - RotAmt) & 0x7f) | ((RotAmt + 8) << 7);
    306 
    307     return -1;
    308   }
    309 
    310   /// getT2SOImmVal - Given a 32-bit immediate, if it is something that can fit
    311   /// into a Thumb-2 shifter_operand immediate operand, return the 12-bit
    312   /// encoding for it.  If not, return -1.
    313   /// See ARM Reference Manual A6.3.2.
    314   static inline int getT2SOImmVal(unsigned Arg) {
    315     // If 'Arg' is an 8-bit splat, then get the encoded value.
    316     int Splat = getT2SOImmValSplatVal(Arg);
    317     if (Splat != -1)
    318       return Splat;
    319 
    320     // If 'Arg' can be handled with a single shifter_op return the value.
    321     int Rot = getT2SOImmValRotateVal(Arg);
    322     if (Rot != -1)
    323       return Rot;
    324 
    325     return -1;
    326   }
    327 
    328   static inline unsigned getT2SOImmValRotate(unsigned V) {
    329     if ((V & ~255U) == 0) return 0;
    330     // Use CTZ to compute the rotate amount.
    331     unsigned RotAmt = countTrailingZeros(V);
    332     return (32 - RotAmt) & 31;
    333   }
    334 
    335   static inline bool isT2SOImmTwoPartVal (unsigned Imm) {
    336     unsigned V = Imm;
    337     // Passing values can be any combination of splat values and shifter
    338     // values. If this can be handled with a single shifter or splat, bail
    339     // out. Those should be handled directly, not with a two-part val.
    340     if (getT2SOImmValSplatVal(V) != -1)
    341       return false;
    342     V = rotr32 (~255U, getT2SOImmValRotate(V)) & V;
    343     if (V == 0)
    344       return false;
    345 
    346     // If this can be handled as an immediate, accept.
    347     if (getT2SOImmVal(V) != -1) return true;
    348 
    349     // Likewise, try masking out a splat value first.
    350     V = Imm;
    351     if (getT2SOImmValSplatVal(V & 0xff00ff00U) != -1)
    352       V &= ~0xff00ff00U;
    353     else if (getT2SOImmValSplatVal(V & 0x00ff00ffU) != -1)
    354       V &= ~0x00ff00ffU;
    355     // If what's left can be handled as an immediate, accept.
    356     if (getT2SOImmVal(V) != -1) return true;
    357 
    358     // Otherwise, do not accept.
    359     return false;
    360   }
    361 
    362   static inline unsigned getT2SOImmTwoPartFirst(unsigned Imm) {
    363     assert (isT2SOImmTwoPartVal(Imm) &&
    364             "Immedate cannot be encoded as two part immediate!");
    365     // Try a shifter operand as one part
    366     unsigned V = rotr32 (~255, getT2SOImmValRotate(Imm)) & Imm;
    367     // If the rest is encodable as an immediate, then return it.
    368     if (getT2SOImmVal(V) != -1) return V;
    369 
    370     // Try masking out a splat value first.
    371     if (getT2SOImmValSplatVal(Imm & 0xff00ff00U) != -1)
    372       return Imm & 0xff00ff00U;
    373 
    374     // The other splat is all that's left as an option.
    375     assert (getT2SOImmValSplatVal(Imm & 0x00ff00ffU) != -1);
    376     return Imm & 0x00ff00ffU;
    377   }
    378 
    379   static inline unsigned getT2SOImmTwoPartSecond(unsigned Imm) {
    380     // Mask out the first hunk
    381     Imm ^= getT2SOImmTwoPartFirst(Imm);
    382     // Return what's left
    383     assert (getT2SOImmVal(Imm) != -1 &&
    384             "Unable to encode second part of T2 two part SO immediate");
    385     return Imm;
    386   }
    387 
    388 
    389   //===--------------------------------------------------------------------===//
    390   // Addressing Mode #2
    391   //===--------------------------------------------------------------------===//
    392   //
    393   // This is used for most simple load/store instructions.
    394   //
    395   // addrmode2 := reg +/- reg shop imm
    396   // addrmode2 := reg +/- imm12
    397   //
    398   // The first operand is always a Reg.  The second operand is a reg if in
    399   // reg/reg form, otherwise it's reg#0.  The third field encodes the operation
    400   // in bit 12, the immediate in bits 0-11, and the shift op in 13-15. The
    401   // fourth operand 16-17 encodes the index mode.
    402   //
    403   // If this addressing mode is a frame index (before prolog/epilog insertion
    404   // and code rewriting), this operand will have the form:  FI#, reg0, <offs>
    405   // with no shift amount for the frame offset.
    406   //
    407   static inline unsigned getAM2Opc(AddrOpc Opc, unsigned Imm12, ShiftOpc SO,
    408                                    unsigned IdxMode = 0) {
    409     assert(Imm12 < (1 << 12) && "Imm too large!");
    410     bool isSub = Opc == sub;
    411     return Imm12 | ((int)isSub << 12) | (SO << 13) | (IdxMode << 16) ;
    412   }
    413   static inline unsigned getAM2Offset(unsigned AM2Opc) {
    414     return AM2Opc & ((1 << 12)-1);
    415   }
    416   static inline AddrOpc getAM2Op(unsigned AM2Opc) {
    417     return ((AM2Opc >> 12) & 1) ? sub : add;
    418   }
    419   static inline ShiftOpc getAM2ShiftOpc(unsigned AM2Opc) {
    420     return (ShiftOpc)((AM2Opc >> 13) & 7);
    421   }
    422   static inline unsigned getAM2IdxMode(unsigned AM2Opc) {
    423     return (AM2Opc >> 16);
    424   }
    425 
    426 
    427   //===--------------------------------------------------------------------===//
    428   // Addressing Mode #3
    429   //===--------------------------------------------------------------------===//
    430   //
    431   // This is used for sign-extending loads, and load/store-pair instructions.
    432   //
    433   // addrmode3 := reg +/- reg
    434   // addrmode3 := reg +/- imm8
    435   //
    436   // The first operand is always a Reg.  The second operand is a reg if in
    437   // reg/reg form, otherwise it's reg#0.  The third field encodes the operation
    438   // in bit 8, the immediate in bits 0-7. The fourth operand 9-10 encodes the
    439   // index mode.
    440 
    441   /// getAM3Opc - This function encodes the addrmode3 opc field.
    442   static inline unsigned getAM3Opc(AddrOpc Opc, unsigned char Offset,
    443                                    unsigned IdxMode = 0) {
    444     bool isSub = Opc == sub;
    445     return ((int)isSub << 8) | Offset | (IdxMode << 9);
    446   }
    447   static inline unsigned char getAM3Offset(unsigned AM3Opc) {
    448     return AM3Opc & 0xFF;
    449   }
    450   static inline AddrOpc getAM3Op(unsigned AM3Opc) {
    451     return ((AM3Opc >> 8) & 1) ? sub : add;
    452   }
    453   static inline unsigned getAM3IdxMode(unsigned AM3Opc) {
    454     return (AM3Opc >> 9);
    455   }
    456 
    457   //===--------------------------------------------------------------------===//
    458   // Addressing Mode #4
    459   //===--------------------------------------------------------------------===//
    460   //
    461   // This is used for load / store multiple instructions.
    462   //
    463   // addrmode4 := reg, <mode>
    464   //
    465   // The four modes are:
    466   //    IA - Increment after
    467   //    IB - Increment before
    468   //    DA - Decrement after
    469   //    DB - Decrement before
    470   // For VFP instructions, only the IA and DB modes are valid.
    471 
    472   static inline AMSubMode getAM4SubMode(unsigned Mode) {
    473     return (AMSubMode)(Mode & 0x7);
    474   }
    475 
    476   static inline unsigned getAM4ModeImm(AMSubMode SubMode) {
    477     return (int)SubMode;
    478   }
    479 
    480   //===--------------------------------------------------------------------===//
    481   // Addressing Mode #5
    482   //===--------------------------------------------------------------------===//
    483   //
    484   // This is used for coprocessor instructions, such as FP load/stores.
    485   //
    486   // addrmode5 := reg +/- imm8*4
    487   //
    488   // The first operand is always a Reg.  The second operand encodes the
    489   // operation in bit 8 and the immediate in bits 0-7.
    490 
    491   /// getAM5Opc - This function encodes the addrmode5 opc field.
    492   static inline unsigned getAM5Opc(AddrOpc Opc, unsigned char Offset) {
    493     bool isSub = Opc == sub;
    494     return ((int)isSub << 8) | Offset;
    495   }
    496   static inline unsigned char getAM5Offset(unsigned AM5Opc) {
    497     return AM5Opc & 0xFF;
    498   }
    499   static inline AddrOpc getAM5Op(unsigned AM5Opc) {
    500     return ((AM5Opc >> 8) & 1) ? sub : add;
    501   }
    502 
    503   //===--------------------------------------------------------------------===//
    504   // Addressing Mode #6
    505   //===--------------------------------------------------------------------===//
    506   //
    507   // This is used for NEON load / store instructions.
    508   //
    509   // addrmode6 := reg with optional alignment
    510   //
    511   // This is stored in two operands [regaddr, align].  The first is the
    512   // address register.  The second operand is the value of the alignment
    513   // specifier in bytes or zero if no explicit alignment.
    514   // Valid alignments depend on the specific instruction.
    515 
    516   //===--------------------------------------------------------------------===//
    517   // NEON Modified Immediates
    518   //===--------------------------------------------------------------------===//
    519   //
    520   // Several NEON instructions (e.g., VMOV) take a "modified immediate"
    521   // vector operand, where a small immediate encoded in the instruction
    522   // specifies a full NEON vector value.  These modified immediates are
    523   // represented here as encoded integers.  The low 8 bits hold the immediate
    524   // value; bit 12 holds the "Op" field of the instruction, and bits 11-8 hold
    525   // the "Cmode" field of the instruction.  The interfaces below treat the
    526   // Op and Cmode values as a single 5-bit value.
    527 
    528   static inline unsigned createNEONModImm(unsigned OpCmode, unsigned Val) {
    529     return (OpCmode << 8) | Val;
    530   }
    531   static inline unsigned getNEONModImmOpCmode(unsigned ModImm) {
    532     return (ModImm >> 8) & 0x1f;
    533   }
    534   static inline unsigned getNEONModImmVal(unsigned ModImm) {
    535     return ModImm & 0xff;
    536   }
    537 
    538   /// decodeNEONModImm - Decode a NEON modified immediate value into the
    539   /// element value and the element size in bits.  (If the element size is
    540   /// smaller than the vector, it is splatted into all the elements.)
    541   static inline uint64_t decodeNEONModImm(unsigned ModImm, unsigned &EltBits) {
    542     unsigned OpCmode = getNEONModImmOpCmode(ModImm);
    543     unsigned Imm8 = getNEONModImmVal(ModImm);
    544     uint64_t Val = 0;
    545 
    546     if (OpCmode == 0xe) {
    547       // 8-bit vector elements
    548       Val = Imm8;
    549       EltBits = 8;
    550     } else if ((OpCmode & 0xc) == 0x8) {
    551       // 16-bit vector elements
    552       unsigned ByteNum = (OpCmode & 0x6) >> 1;
    553       Val = Imm8 << (8 * ByteNum);
    554       EltBits = 16;
    555     } else if ((OpCmode & 0x8) == 0) {
    556       // 32-bit vector elements, zero with one byte set
    557       unsigned ByteNum = (OpCmode & 0x6) >> 1;
    558       Val = Imm8 << (8 * ByteNum);
    559       EltBits = 32;
    560     } else if ((OpCmode & 0xe) == 0xc) {
    561       // 32-bit vector elements, one byte with low bits set
    562       unsigned ByteNum = 1 + (OpCmode & 0x1);
    563       Val = (Imm8 << (8 * ByteNum)) | (0xffff >> (8 * (2 - ByteNum)));
    564       EltBits = 32;
    565     } else if (OpCmode == 0x1e) {
    566       // 64-bit vector elements
    567       for (unsigned ByteNum = 0; ByteNum < 8; ++ByteNum) {
    568         if ((ModImm >> ByteNum) & 1)
    569           Val |= (uint64_t)0xff << (8 * ByteNum);
    570       }
    571       EltBits = 64;
    572     } else {
    573       llvm_unreachable("Unsupported NEON immediate");
    574     }
    575     return Val;
    576   }
    577 
    578   AMSubMode getLoadStoreMultipleSubMode(int Opcode);
    579 
    580   //===--------------------------------------------------------------------===//
    581   // Floating-point Immediates
    582   //
    583   static inline float getFPImmFloat(unsigned Imm) {
    584     // We expect an 8-bit binary encoding of a floating-point number here.
    585     union {
    586       uint32_t I;
    587       float F;
    588     } FPUnion;
    589 
    590     uint8_t Sign = (Imm >> 7) & 0x1;
    591     uint8_t Exp = (Imm >> 4) & 0x7;
    592     uint8_t Mantissa = Imm & 0xf;
    593 
    594     //   8-bit FP    iEEEE Float Encoding
    595     //   abcd efgh   aBbbbbbc defgh000 00000000 00000000
    596     //
    597     // where B = NOT(b);
    598 
    599     FPUnion.I = 0;
    600     FPUnion.I |= Sign << 31;
    601     FPUnion.I |= ((Exp & 0x4) != 0 ? 0 : 1) << 30;
    602     FPUnion.I |= ((Exp & 0x4) != 0 ? 0x1f : 0) << 25;
    603     FPUnion.I |= (Exp & 0x3) << 23;
    604     FPUnion.I |= Mantissa << 19;
    605     return FPUnion.F;
    606   }
    607 
    608   /// getFP32Imm - Return an 8-bit floating-point version of the 32-bit
    609   /// floating-point value. If the value cannot be represented as an 8-bit
    610   /// floating-point value, then return -1.
    611   static inline int getFP32Imm(const APInt &Imm) {
    612     uint32_t Sign = Imm.lshr(31).getZExtValue() & 1;
    613     int32_t Exp = (Imm.lshr(23).getSExtValue() & 0xff) - 127;  // -126 to 127
    614     int64_t Mantissa = Imm.getZExtValue() & 0x7fffff;  // 23 bits
    615 
    616     // We can handle 4 bits of mantissa.
    617     // mantissa = (16+UInt(e:f:g:h))/16.
    618     if (Mantissa & 0x7ffff)
    619       return -1;
    620     Mantissa >>= 19;
    621     if ((Mantissa & 0xf) != Mantissa)
    622       return -1;
    623 
    624     // We can handle 3 bits of exponent: exp == UInt(NOT(b):c:d)-3
    625     if (Exp < -3 || Exp > 4)
    626       return -1;
    627     Exp = ((Exp+3) & 0x7) ^ 4;
    628 
    629     return ((int)Sign << 7) | (Exp << 4) | Mantissa;
    630   }
    631 
    632   static inline int getFP32Imm(const APFloat &FPImm) {
    633     return getFP32Imm(FPImm.bitcastToAPInt());
    634   }
    635 
    636   /// getFP64Imm - Return an 8-bit floating-point version of the 64-bit
    637   /// floating-point value. If the value cannot be represented as an 8-bit
    638   /// floating-point value, then return -1.
    639   static inline int getFP64Imm(const APInt &Imm) {
    640     uint64_t Sign = Imm.lshr(63).getZExtValue() & 1;
    641     int64_t Exp = (Imm.lshr(52).getSExtValue() & 0x7ff) - 1023; // -1022 to 1023
    642     uint64_t Mantissa = Imm.getZExtValue() & 0xfffffffffffffULL;
    643 
    644     // We can handle 4 bits of mantissa.
    645     // mantissa = (16+UInt(e:f:g:h))/16.
    646     if (Mantissa & 0xffffffffffffULL)
    647       return -1;
    648     Mantissa >>= 48;
    649     if ((Mantissa & 0xf) != Mantissa)
    650       return -1;
    651 
    652     // We can handle 3 bits of exponent: exp == UInt(NOT(b):c:d)-3
    653     if (Exp < -3 || Exp > 4)
    654       return -1;
    655     Exp = ((Exp+3) & 0x7) ^ 4;
    656 
    657     return ((int)Sign << 7) | (Exp << 4) | Mantissa;
    658   }
    659 
    660   static inline int getFP64Imm(const APFloat &FPImm) {
    661     return getFP64Imm(FPImm.bitcastToAPInt());
    662   }
    663 
    664 } // end namespace ARM_AM
    665 } // end namespace llvm
    666 
    667 #endif
    668 
    669