Home | History | Annotate | Download | only in mips
      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef  V8_MIPS_CONSTANTS_H_
      6 #define  V8_MIPS_CONSTANTS_H_
      7 #include "src/globals.h"
      8 // UNIMPLEMENTED_ macro for MIPS.
      9 #ifdef DEBUG
     10 #define UNIMPLEMENTED_MIPS()                                                  \
     11   v8::internal::PrintF("%s, \tline %d: \tfunction %s not implemented. \n",    \
     12                        __FILE__, __LINE__, __func__)
     13 #else
     14 #define UNIMPLEMENTED_MIPS()
     15 #endif
     16 
     17 #define UNSUPPORTED_MIPS() v8::internal::PrintF("Unsupported instruction.\n")
     18 
     19 enum ArchVariants {
     20   kMips32r1 = v8::internal::MIPSr1,
     21   kMips32r2 = v8::internal::MIPSr2,
     22   kMips32r6 = v8::internal::MIPSr6,
     23   kLoongson
     24 };
     25 
     26 #ifdef _MIPS_ARCH_MIPS32R2
     27   static const ArchVariants kArchVariant = kMips32r2;
     28 #elif _MIPS_ARCH_MIPS32R6
     29   static const ArchVariants kArchVariant = kMips32r6;
     30 #elif _MIPS_ARCH_LOONGSON
     31 // The loongson flag refers to the LOONGSON architectures based on MIPS-III,
     32 // which predates (and is a subset of) the mips32r2 and r1 architectures.
     33   static const ArchVariants kArchVariant = kLoongson;
     34 #elif _MIPS_ARCH_MIPS32RX
     35 // This flags referred to compatibility mode that creates universal code that
     36 // can run on any MIPS32 architecture revision. The dynamically generated code
     37 // by v8 is specialized for the MIPS host detected in runtime probing.
     38   static const ArchVariants kArchVariant = kMips32r1;
     39 #else
     40   static const ArchVariants kArchVariant = kMips32r1;
     41 #endif
     42 
     43 enum Endianness {
     44   kLittle,
     45   kBig
     46 };
     47 
     48 #if defined(V8_TARGET_LITTLE_ENDIAN)
     49   static const Endianness kArchEndian = kLittle;
     50 #elif defined(V8_TARGET_BIG_ENDIAN)
     51   static const Endianness kArchEndian = kBig;
     52 #else
     53 #error Unknown endianness
     54 #endif
     55 
     56 enum FpuMode {
     57   kFP32,
     58   kFP64,
     59   kFPXX
     60 };
     61 
     62 #if defined(FPU_MODE_FP32)
     63   static const FpuMode kFpuMode = kFP32;
     64 #elif defined(FPU_MODE_FP64)
     65   static const FpuMode kFpuMode = kFP64;
     66 #elif defined(FPU_MODE_FPXX)
     67 #if defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS32R6)
     68 static const FpuMode kFpuMode = kFPXX;
     69 #else
     70 #error "FPXX is supported only on Mips32R2 and Mips32R6"
     71 #endif
     72 #else
     73 static const FpuMode kFpuMode = kFP32;
     74 #endif
     75 
     76 #if(defined(__mips_hard_float) && __mips_hard_float != 0)
     77 // Use floating-point coprocessor instructions. This flag is raised when
     78 // -mhard-float is passed to the compiler.
     79 const bool IsMipsSoftFloatABI = false;
     80 #elif(defined(__mips_soft_float) && __mips_soft_float != 0)
     81 // This flag is raised when -msoft-float is passed to the compiler.
     82 // Although FPU is a base requirement for v8, soft-float ABI is used
     83 // on soft-float systems with FPU kernel emulation.
     84 const bool IsMipsSoftFloatABI = true;
     85 #else
     86 const bool IsMipsSoftFloatABI = true;
     87 #endif
     88 
     89 #if defined(V8_TARGET_LITTLE_ENDIAN)
     90 const uint32_t kHoleNanUpper32Offset = 4;
     91 const uint32_t kHoleNanLower32Offset = 0;
     92 #elif defined(V8_TARGET_BIG_ENDIAN)
     93 const uint32_t kHoleNanUpper32Offset = 0;
     94 const uint32_t kHoleNanLower32Offset = 4;
     95 #else
     96 #error Unknown endianness
     97 #endif
     98 
     99 #define IsFp64Mode() (kFpuMode == kFP64)
    100 #define IsFp32Mode() (kFpuMode == kFP32)
    101 #define IsFpxxMode() (kFpuMode == kFPXX)
    102 
    103 #ifndef _MIPS_ARCH_MIPS32RX
    104 #define IsMipsArchVariant(check) \
    105   (kArchVariant == check)
    106 #else
    107 #define IsMipsArchVariant(check) \
    108   (CpuFeatures::IsSupported(static_cast<CpuFeature>(check)))
    109 #endif
    110 
    111 #if defined(V8_TARGET_LITTLE_ENDIAN)
    112 const uint32_t kMipsLwrOffset = 0;
    113 const uint32_t kMipsLwlOffset = 3;
    114 const uint32_t kMipsSwrOffset = 0;
    115 const uint32_t kMipsSwlOffset = 3;
    116 #elif defined(V8_TARGET_BIG_ENDIAN)
    117 const uint32_t kMipsLwrOffset = 3;
    118 const uint32_t kMipsLwlOffset = 0;
    119 const uint32_t kMipsSwrOffset = 3;
    120 const uint32_t kMipsSwlOffset = 0;
    121 #else
    122 #error Unknown endianness
    123 #endif
    124 
    125 #define __STDC_FORMAT_MACROS
    126 #include <inttypes.h>
    127 
    128 // Defines constants and accessor classes to assemble, disassemble and
    129 // simulate MIPS32 instructions.
    130 //
    131 // See: MIPS32 Architecture For Programmers
    132 //      Volume II: The MIPS32 Instruction Set
    133 // Try www.cs.cornell.edu/courses/cs3410/2008fa/MIPS_Vol2.pdf.
    134 
    135 namespace v8 {
    136 namespace internal {
    137 
    138 // -----------------------------------------------------------------------------
    139 // Registers and FPURegisters.
    140 
    141 // Number of general purpose registers.
    142 const int kNumRegisters = 32;
    143 const int kInvalidRegister = -1;
    144 
    145 // Number of registers with HI, LO, and pc.
    146 const int kNumSimuRegisters = 35;
    147 
    148 // In the simulator, the PC register is simulated as the 34th register.
    149 const int kPCRegister = 34;
    150 
    151 // Number coprocessor registers.
    152 const int kNumFPURegisters = 32;
    153 const int kInvalidFPURegister = -1;
    154 
    155 // FPU (coprocessor 1) control registers. Currently only FCSR is implemented.
    156 const int kFCSRRegister = 31;
    157 const int kInvalidFPUControlRegister = -1;
    158 const uint32_t kFPUInvalidResult = static_cast<uint32_t>(1 << 31) - 1;
    159 const int32_t kFPUInvalidResultNegative = static_cast<int32_t>(1 << 31);
    160 const uint64_t kFPU64InvalidResult =
    161     static_cast<uint64_t>(static_cast<uint64_t>(1) << 63) - 1;
    162 const int64_t kFPU64InvalidResultNegative =
    163     static_cast<int64_t>(static_cast<uint64_t>(1) << 63);
    164 
    165 // FCSR constants.
    166 const uint32_t kFCSRInexactFlagBit = 2;
    167 const uint32_t kFCSRUnderflowFlagBit = 3;
    168 const uint32_t kFCSROverflowFlagBit = 4;
    169 const uint32_t kFCSRDivideByZeroFlagBit = 5;
    170 const uint32_t kFCSRInvalidOpFlagBit = 6;
    171 const uint32_t kFCSRNaN2008FlagBit = 18;
    172 
    173 const uint32_t kFCSRInexactFlagMask = 1 << kFCSRInexactFlagBit;
    174 const uint32_t kFCSRUnderflowFlagMask = 1 << kFCSRUnderflowFlagBit;
    175 const uint32_t kFCSROverflowFlagMask = 1 << kFCSROverflowFlagBit;
    176 const uint32_t kFCSRDivideByZeroFlagMask = 1 << kFCSRDivideByZeroFlagBit;
    177 const uint32_t kFCSRInvalidOpFlagMask = 1 << kFCSRInvalidOpFlagBit;
    178 const uint32_t kFCSRNaN2008FlagMask = 1 << kFCSRNaN2008FlagBit;
    179 
    180 const uint32_t kFCSRFlagMask =
    181     kFCSRInexactFlagMask |
    182     kFCSRUnderflowFlagMask |
    183     kFCSROverflowFlagMask |
    184     kFCSRDivideByZeroFlagMask |
    185     kFCSRInvalidOpFlagMask;
    186 
    187 const uint32_t kFCSRExceptionFlagMask = kFCSRFlagMask ^ kFCSRInexactFlagMask;
    188 
    189 // 'pref' instruction hints
    190 const int32_t kPrefHintLoad = 0;
    191 const int32_t kPrefHintStore = 1;
    192 const int32_t kPrefHintLoadStreamed = 4;
    193 const int32_t kPrefHintStoreStreamed = 5;
    194 const int32_t kPrefHintLoadRetained = 6;
    195 const int32_t kPrefHintStoreRetained = 7;
    196 const int32_t kPrefHintWritebackInvalidate = 25;
    197 const int32_t kPrefHintPrepareForStore = 30;
    198 
    199 // Helper functions for converting between register numbers and names.
    200 class Registers {
    201  public:
    202   // Return the name of the register.
    203   static const char* Name(int reg);
    204 
    205   // Lookup the register number for the name provided.
    206   static int Number(const char* name);
    207 
    208   struct RegisterAlias {
    209     int reg;
    210     const char* name;
    211   };
    212 
    213   static const int32_t kMaxValue = 0x7fffffff;
    214   static const int32_t kMinValue = 0x80000000;
    215 
    216  private:
    217   static const char* names_[kNumSimuRegisters];
    218   static const RegisterAlias aliases_[];
    219 };
    220 
    221 // Helper functions for converting between register numbers and names.
    222 class FPURegisters {
    223  public:
    224   // Return the name of the register.
    225   static const char* Name(int reg);
    226 
    227   // Lookup the register number for the name provided.
    228   static int Number(const char* name);
    229 
    230   struct RegisterAlias {
    231     int creg;
    232     const char* name;
    233   };
    234 
    235  private:
    236   static const char* names_[kNumFPURegisters];
    237   static const RegisterAlias aliases_[];
    238 };
    239 
    240 
    241 // -----------------------------------------------------------------------------
    242 // Instructions encoding constants.
    243 
    244 // On MIPS all instructions are 32 bits.
    245 typedef int32_t Instr;
    246 
    247 // Special Software Interrupt codes when used in the presence of the MIPS
    248 // simulator.
    249 enum SoftwareInterruptCodes {
    250   // Transition to C code.
    251   call_rt_redirected = 0xfffff
    252 };
    253 
    254 // On MIPS Simulator breakpoints can have different codes:
    255 // - Breaks between 0 and kMaxWatchpointCode are treated as simple watchpoints,
    256 //   the simulator will run through them and print the registers.
    257 // - Breaks between kMaxWatchpointCode and kMaxStopCode are treated as stop()
    258 //   instructions (see Assembler::stop()).
    259 // - Breaks larger than kMaxStopCode are simple breaks, dropping you into the
    260 //   debugger.
    261 const uint32_t kMaxWatchpointCode = 31;
    262 const uint32_t kMaxStopCode = 127;
    263 STATIC_ASSERT(kMaxWatchpointCode < kMaxStopCode);
    264 
    265 
    266 // ----- Fields offset and length.
    267 const int kOpcodeShift   = 26;
    268 const int kOpcodeBits    = 6;
    269 const int kRsShift       = 21;
    270 const int kRsBits        = 5;
    271 const int kRtShift       = 16;
    272 const int kRtBits        = 5;
    273 const int kRdShift       = 11;
    274 const int kRdBits        = 5;
    275 const int kSaShift       = 6;
    276 const int kSaBits        = 5;
    277 const int kLsaSaBits = 2;
    278 const int kFunctionShift = 0;
    279 const int kFunctionBits  = 6;
    280 const int kLuiShift      = 16;
    281 const int kBp2Shift = 6;
    282 const int kBp2Bits = 2;
    283 
    284 const int kImm16Shift = 0;
    285 const int kImm16Bits  = 16;
    286 const int kImm18Shift = 0;
    287 const int kImm18Bits = 18;
    288 const int kImm19Shift = 0;
    289 const int kImm19Bits = 19;
    290 const int kImm21Shift = 0;
    291 const int kImm21Bits  = 21;
    292 const int kImm26Shift = 0;
    293 const int kImm26Bits  = 26;
    294 const int kImm28Shift = 0;
    295 const int kImm28Bits  = 28;
    296 const int kImm32Shift = 0;
    297 const int kImm32Bits  = 32;
    298 
    299 // In branches and jumps immediate fields point to words, not bytes,
    300 // and are therefore shifted by 2.
    301 const int kImmFieldShift = 2;
    302 
    303 const int kFrBits        = 5;
    304 const int kFrShift       = 21;
    305 const int kFsShift       = 11;
    306 const int kFsBits        = 5;
    307 const int kFtShift       = 16;
    308 const int kFtBits        = 5;
    309 const int kFdShift       = 6;
    310 const int kFdBits        = 5;
    311 const int kFCccShift     = 8;
    312 const int kFCccBits      = 3;
    313 const int kFBccShift     = 18;
    314 const int kFBccBits      = 3;
    315 const int kFBtrueShift   = 16;
    316 const int kFBtrueBits    = 1;
    317 
    318 // ----- Miscellaneous useful masks.
    319 // Instruction bit masks.
    320 const int kOpcodeMask = ((1 << kOpcodeBits) - 1) << kOpcodeShift;
    321 const int kImm16Mask = ((1 << kImm16Bits) - 1) << kImm16Shift;
    322 const int kImm18Mask = ((1 << kImm18Bits) - 1) << kImm18Shift;
    323 const int kImm19Mask = ((1 << kImm19Bits) - 1) << kImm19Shift;
    324 const int kImm21Mask = ((1 << kImm21Bits) - 1) << kImm21Shift;
    325 const int kImm26Mask = ((1 << kImm26Bits) - 1) << kImm26Shift;
    326 const int kImm28Mask = ((1 << kImm28Bits) - 1) << kImm28Shift;
    327 const int kRsFieldMask = ((1 << kRsBits) - 1) << kRsShift;
    328 const int kRtFieldMask = ((1 << kRtBits) - 1) << kRtShift;
    329 const int kRdFieldMask = ((1 << kRdBits) - 1) << kRdShift;
    330 const int kSaFieldMask = ((1 << kSaBits) - 1) << kSaShift;
    331 const int kFunctionFieldMask = ((1 << kFunctionBits) - 1) << kFunctionShift;
    332 // Misc masks.
    333 const int kHiMask = 0xffff << 16;
    334 const int kLoMask = 0xffff;
    335 const int kSignMask = 0x80000000;
    336 const int kJumpAddrMask = (1 << (kImm26Bits + kImmFieldShift)) - 1;
    337 
    338 // ----- MIPS Opcodes and Function Fields.
    339 // We use this presentation to stay close to the table representation in
    340 // MIPS32 Architecture For Programmers, Volume II: The MIPS32 Instruction Set.
    341 enum Opcode : uint32_t {
    342   SPECIAL = 0U << kOpcodeShift,
    343   REGIMM = 1U << kOpcodeShift,
    344 
    345   J = ((0U << 3) + 2) << kOpcodeShift,
    346   JAL = ((0U << 3) + 3) << kOpcodeShift,
    347   BEQ = ((0U << 3) + 4) << kOpcodeShift,
    348   BNE = ((0U << 3) + 5) << kOpcodeShift,
    349   BLEZ = ((0U << 3) + 6) << kOpcodeShift,
    350   BGTZ = ((0U << 3) + 7) << kOpcodeShift,
    351 
    352   ADDI = ((1U << 3) + 0) << kOpcodeShift,
    353   ADDIU = ((1U << 3) + 1) << kOpcodeShift,
    354   SLTI = ((1U << 3) + 2) << kOpcodeShift,
    355   SLTIU = ((1U << 3) + 3) << kOpcodeShift,
    356   ANDI = ((1U << 3) + 4) << kOpcodeShift,
    357   ORI = ((1U << 3) + 5) << kOpcodeShift,
    358   XORI = ((1U << 3) + 6) << kOpcodeShift,
    359   LUI = ((1U << 3) + 7) << kOpcodeShift,  // LUI/AUI family.
    360 
    361   BEQC = ((2U << 3) + 0) << kOpcodeShift,
    362   COP1 = ((2U << 3) + 1) << kOpcodeShift,  // Coprocessor 1 class.
    363   BEQL = ((2U << 3) + 4) << kOpcodeShift,
    364   BNEL = ((2U << 3) + 5) << kOpcodeShift,
    365   BLEZL = ((2U << 3) + 6) << kOpcodeShift,
    366   BGTZL = ((2U << 3) + 7) << kOpcodeShift,
    367 
    368   DADDI = ((3U << 3) + 0) << kOpcodeShift,  // This is also BNEC.
    369   SPECIAL2 = ((3U << 3) + 4) << kOpcodeShift,
    370   SPECIAL3 = ((3U << 3) + 7) << kOpcodeShift,
    371 
    372   LB = ((4U << 3) + 0) << kOpcodeShift,
    373   LH = ((4U << 3) + 1) << kOpcodeShift,
    374   LWL = ((4U << 3) + 2) << kOpcodeShift,
    375   LW = ((4U << 3) + 3) << kOpcodeShift,
    376   LBU = ((4U << 3) + 4) << kOpcodeShift,
    377   LHU = ((4U << 3) + 5) << kOpcodeShift,
    378   LWR = ((4U << 3) + 6) << kOpcodeShift,
    379   SB = ((5U << 3) + 0) << kOpcodeShift,
    380   SH = ((5U << 3) + 1) << kOpcodeShift,
    381   SWL = ((5U << 3) + 2) << kOpcodeShift,
    382   SW = ((5U << 3) + 3) << kOpcodeShift,
    383   SWR = ((5U << 3) + 6) << kOpcodeShift,
    384 
    385   LWC1 = ((6U << 3) + 1) << kOpcodeShift,
    386   BC = ((6U << 3) + 2) << kOpcodeShift,
    387   LDC1 = ((6U << 3) + 5) << kOpcodeShift,
    388   POP66 = ((6U << 3) + 6) << kOpcodeShift,  // beqzc, jic
    389 
    390   PREF = ((6U << 3) + 3) << kOpcodeShift,
    391 
    392   SWC1 = ((7U << 3) + 1) << kOpcodeShift,
    393   BALC = ((7U << 3) + 2) << kOpcodeShift,
    394   PCREL = ((7U << 3) + 3) << kOpcodeShift,
    395   SDC1 = ((7U << 3) + 5) << kOpcodeShift,
    396   POP76 = ((7U << 3) + 6) << kOpcodeShift,  // bnezc, jialc
    397 
    398   COP1X = ((1U << 4) + 3) << kOpcodeShift,
    399 
    400   // New r6 instruction.
    401   POP06 = BLEZ,   // bgeuc/bleuc, blezalc, bgezalc
    402   POP07 = BGTZ,   // bltuc/bgtuc, bgtzalc, bltzalc
    403   POP10 = ADDI,   // beqzalc, bovc, beqc
    404   POP26 = BLEZL,  // bgezc, blezc, bgec/blec
    405   POP27 = BGTZL,  // bgtzc, bltzc, bltc/bgtc
    406   POP30 = DADDI,  // bnezalc, bnvc, bnec
    407 };
    408 
    409 enum SecondaryField : uint32_t {
    410   // SPECIAL Encoding of Function Field.
    411   SLL = ((0U << 3) + 0),
    412   MOVCI = ((0U << 3) + 1),
    413   SRL = ((0U << 3) + 2),
    414   SRA = ((0U << 3) + 3),
    415   SLLV = ((0U << 3) + 4),
    416   LSA = ((0U << 3) + 5),
    417   SRLV = ((0U << 3) + 6),
    418   SRAV = ((0U << 3) + 7),
    419 
    420   JR = ((1U << 3) + 0),
    421   JALR = ((1U << 3) + 1),
    422   MOVZ = ((1U << 3) + 2),
    423   MOVN = ((1U << 3) + 3),
    424   BREAK = ((1U << 3) + 5),
    425   SYNC = ((1U << 3) + 7),
    426 
    427   MFHI = ((2U << 3) + 0),
    428   CLZ_R6 = ((2U << 3) + 0),
    429   CLO_R6 = ((2U << 3) + 1),
    430   MFLO = ((2U << 3) + 2),
    431 
    432   MULT = ((3U << 3) + 0),
    433   MULTU = ((3U << 3) + 1),
    434   DIV = ((3U << 3) + 2),
    435   DIVU = ((3U << 3) + 3),
    436 
    437   ADD = ((4U << 3) + 0),
    438   ADDU = ((4U << 3) + 1),
    439   SUB = ((4U << 3) + 2),
    440   SUBU = ((4U << 3) + 3),
    441   AND = ((4U << 3) + 4),
    442   OR = ((4U << 3) + 5),
    443   XOR = ((4U << 3) + 6),
    444   NOR = ((4U << 3) + 7),
    445 
    446   SLT = ((5U << 3) + 2),
    447   SLTU = ((5U << 3) + 3),
    448 
    449   TGE = ((6U << 3) + 0),
    450   TGEU = ((6U << 3) + 1),
    451   TLT = ((6U << 3) + 2),
    452   TLTU = ((6U << 3) + 3),
    453   TEQ = ((6U << 3) + 4),
    454   SELEQZ_S = ((6U << 3) + 5),
    455   TNE = ((6U << 3) + 6),
    456   SELNEZ_S = ((6U << 3) + 7),
    457 
    458   // Multiply integers in r6.
    459   MUL_MUH = ((3U << 3) + 0),    // MUL, MUH.
    460   MUL_MUH_U = ((3U << 3) + 1),  // MUL_U, MUH_U.
    461   RINT = ((3U << 3) + 2),
    462 
    463   MUL_OP = ((0U << 3) + 2),
    464   MUH_OP = ((0U << 3) + 3),
    465   DIV_OP = ((0U << 3) + 2),
    466   MOD_OP = ((0U << 3) + 3),
    467 
    468   DIV_MOD = ((3U << 3) + 2),
    469   DIV_MOD_U = ((3U << 3) + 3),
    470 
    471   // SPECIAL2 Encoding of Function Field.
    472   MUL = ((0U << 3) + 2),
    473   CLZ = ((4U << 3) + 0),
    474   CLO = ((4U << 3) + 1),
    475 
    476   // SPECIAL3 Encoding of Function Field.
    477   EXT = ((0U << 3) + 0),
    478   INS = ((0U << 3) + 4),
    479   BSHFL = ((4U << 3) + 0),
    480 
    481   // SPECIAL3 Encoding of sa Field.
    482   BITSWAP = ((0U << 3) + 0),
    483   ALIGN = ((0U << 3) + 2),
    484   WSBH = ((0U << 3) + 2),
    485   SEB = ((2U << 3) + 0),
    486   SEH = ((3U << 3) + 0),
    487 
    488   // REGIMM  encoding of rt Field.
    489   BLTZ = ((0U << 3) + 0) << 16,
    490   BGEZ = ((0U << 3) + 1) << 16,
    491   BLTZAL = ((2U << 3) + 0) << 16,
    492   BGEZAL = ((2U << 3) + 1) << 16,
    493   BGEZALL = ((2U << 3) + 3) << 16,
    494 
    495   // COP1 Encoding of rs Field.
    496   MFC1 = ((0U << 3) + 0) << 21,
    497   CFC1 = ((0U << 3) + 2) << 21,
    498   MFHC1 = ((0U << 3) + 3) << 21,
    499   MTC1 = ((0U << 3) + 4) << 21,
    500   CTC1 = ((0U << 3) + 6) << 21,
    501   MTHC1 = ((0U << 3) + 7) << 21,
    502   BC1 = ((1U << 3) + 0) << 21,
    503   S = ((2U << 3) + 0) << 21,
    504   D = ((2U << 3) + 1) << 21,
    505   W = ((2U << 3) + 4) << 21,
    506   L = ((2U << 3) + 5) << 21,
    507   PS = ((2U << 3) + 6) << 21,
    508   // COP1 Encoding of Function Field When rs=S.
    509 
    510   ADD_S = ((0U << 3) + 0),
    511   SUB_S = ((0U << 3) + 1),
    512   MUL_S = ((0U << 3) + 2),
    513   DIV_S = ((0U << 3) + 3),
    514   ABS_S = ((0U << 3) + 5),
    515   SQRT_S = ((0U << 3) + 4),
    516   MOV_S = ((0U << 3) + 6),
    517   NEG_S = ((0U << 3) + 7),
    518   ROUND_L_S = ((1U << 3) + 0),
    519   TRUNC_L_S = ((1U << 3) + 1),
    520   CEIL_L_S = ((1U << 3) + 2),
    521   FLOOR_L_S = ((1U << 3) + 3),
    522   ROUND_W_S = ((1U << 3) + 4),
    523   TRUNC_W_S = ((1U << 3) + 5),
    524   CEIL_W_S = ((1U << 3) + 6),
    525   FLOOR_W_S = ((1U << 3) + 7),
    526   RECIP_S = ((2U << 3) + 5),
    527   RSQRT_S = ((2U << 3) + 6),
    528   CLASS_S = ((3U << 3) + 3),
    529   CVT_D_S = ((4U << 3) + 1),
    530   CVT_W_S = ((4U << 3) + 4),
    531   CVT_L_S = ((4U << 3) + 5),
    532   CVT_PS_S = ((4U << 3) + 6),
    533 
    534   // COP1 Encoding of Function Field When rs=D.
    535   ADD_D = ((0U << 3) + 0),
    536   SUB_D = ((0U << 3) + 1),
    537   MUL_D = ((0U << 3) + 2),
    538   DIV_D = ((0U << 3) + 3),
    539   SQRT_D = ((0U << 3) + 4),
    540   ABS_D = ((0U << 3) + 5),
    541   MOV_D = ((0U << 3) + 6),
    542   NEG_D = ((0U << 3) + 7),
    543   ROUND_L_D = ((1U << 3) + 0),
    544   TRUNC_L_D = ((1U << 3) + 1),
    545   CEIL_L_D = ((1U << 3) + 2),
    546   FLOOR_L_D = ((1U << 3) + 3),
    547   ROUND_W_D = ((1U << 3) + 4),
    548   TRUNC_W_D = ((1U << 3) + 5),
    549   CEIL_W_D = ((1U << 3) + 6),
    550   FLOOR_W_D = ((1U << 3) + 7),
    551   RECIP_D = ((2U << 3) + 5),
    552   RSQRT_D = ((2U << 3) + 6),
    553   CLASS_D = ((3U << 3) + 3),
    554   MIN = ((3U << 3) + 4),
    555   MINA = ((3U << 3) + 5),
    556   MAX = ((3U << 3) + 6),
    557   MAXA = ((3U << 3) + 7),
    558   CVT_S_D = ((4U << 3) + 0),
    559   CVT_W_D = ((4U << 3) + 4),
    560   CVT_L_D = ((4U << 3) + 5),
    561   C_F_D = ((6U << 3) + 0),
    562   C_UN_D = ((6U << 3) + 1),
    563   C_EQ_D = ((6U << 3) + 2),
    564   C_UEQ_D = ((6U << 3) + 3),
    565   C_OLT_D = ((6U << 3) + 4),
    566   C_ULT_D = ((6U << 3) + 5),
    567   C_OLE_D = ((6U << 3) + 6),
    568   C_ULE_D = ((6U << 3) + 7),
    569 
    570   // COP1 Encoding of Function Field When rs=W or L.
    571   CVT_S_W = ((4U << 3) + 0),
    572   CVT_D_W = ((4U << 3) + 1),
    573   CVT_S_L = ((4U << 3) + 0),
    574   CVT_D_L = ((4U << 3) + 1),
    575   BC1EQZ = ((2U << 2) + 1) << 21,
    576   BC1NEZ = ((3U << 2) + 1) << 21,
    577   // COP1 CMP positive predicates Bit 5..4 = 00.
    578   CMP_AF = ((0U << 3) + 0),
    579   CMP_UN = ((0U << 3) + 1),
    580   CMP_EQ = ((0U << 3) + 2),
    581   CMP_UEQ = ((0U << 3) + 3),
    582   CMP_LT = ((0U << 3) + 4),
    583   CMP_ULT = ((0U << 3) + 5),
    584   CMP_LE = ((0U << 3) + 6),
    585   CMP_ULE = ((0U << 3) + 7),
    586   CMP_SAF = ((1U << 3) + 0),
    587   CMP_SUN = ((1U << 3) + 1),
    588   CMP_SEQ = ((1U << 3) + 2),
    589   CMP_SUEQ = ((1U << 3) + 3),
    590   CMP_SSLT = ((1U << 3) + 4),
    591   CMP_SSULT = ((1U << 3) + 5),
    592   CMP_SLE = ((1U << 3) + 6),
    593   CMP_SULE = ((1U << 3) + 7),
    594   // COP1 CMP negative predicates Bit 5..4 = 01.
    595   CMP_AT = ((2U << 3) + 0),  // Reserved, not implemented.
    596   CMP_OR = ((2U << 3) + 1),
    597   CMP_UNE = ((2U << 3) + 2),
    598   CMP_NE = ((2U << 3) + 3),
    599   CMP_UGE = ((2U << 3) + 4),  // Reserved, not implemented.
    600   CMP_OGE = ((2U << 3) + 5),  // Reserved, not implemented.
    601   CMP_UGT = ((2U << 3) + 6),  // Reserved, not implemented.
    602   CMP_OGT = ((2U << 3) + 7),  // Reserved, not implemented.
    603   CMP_SAT = ((3U << 3) + 0),  // Reserved, not implemented.
    604   CMP_SOR = ((3U << 3) + 1),
    605   CMP_SUNE = ((3U << 3) + 2),
    606   CMP_SNE = ((3U << 3) + 3),
    607   CMP_SUGE = ((3U << 3) + 4),  // Reserved, not implemented.
    608   CMP_SOGE = ((3U << 3) + 5),  // Reserved, not implemented.
    609   CMP_SUGT = ((3U << 3) + 6),  // Reserved, not implemented.
    610   CMP_SOGT = ((3U << 3) + 7),  // Reserved, not implemented.
    611 
    612   SEL = ((2U << 3) + 0),
    613   MOVZ_C = ((2U << 3) + 2),
    614   MOVN_C = ((2U << 3) + 3),
    615   SELEQZ_C = ((2U << 3) + 4),  // COP1 on FPR registers.
    616   MOVF = ((2U << 3) + 1),      // Function field for MOVT.fmt and MOVF.fmt
    617   SELNEZ_C = ((2U << 3) + 7),  // COP1 on FPR registers.
    618   // COP1 Encoding of Function Field When rs=PS.
    619   // COP1X Encoding of Function Field.
    620   MADD_D = ((4U << 3) + 1),
    621 
    622   // PCREL Encoding of rt Field.
    623   ADDIUPC = ((0U << 2) + 0),
    624   LWPC = ((0U << 2) + 1),
    625   AUIPC = ((3U << 3) + 6),
    626   ALUIPC = ((3U << 3) + 7),
    627 
    628   // POP66 Encoding of rs Field.
    629   JIC = ((0U << 5) + 0),
    630 
    631   // POP76 Encoding of rs Field.
    632   JIALC = ((0U << 5) + 0),
    633 
    634   NULLSF = 0U
    635 };
    636 
    637 // ----- Emulated conditions.
    638 // On MIPS we use this enum to abstract from conditional branch instructions.
    639 // The 'U' prefix is used to specify unsigned comparisons.
    640 // Opposite conditions must be paired as odd/even numbers
    641 // because 'NegateCondition' function flips LSB to negate condition.
    642 enum Condition {
    643   // Any value < 0 is considered no_condition.
    644   kNoCondition = -1,
    645   overflow = 0,
    646   no_overflow = 1,
    647   Uless = 2,
    648   Ugreater_equal = 3,
    649   Uless_equal = 4,
    650   Ugreater = 5,
    651   equal = 6,
    652   not_equal = 7,  // Unordered or Not Equal.
    653   negative = 8,
    654   positive = 9,
    655   parity_even = 10,
    656   parity_odd = 11,
    657   less = 12,
    658   greater_equal = 13,
    659   less_equal = 14,
    660   greater = 15,
    661   ueq = 16,  // Unordered or Equal.
    662   ogl = 17,  // Ordered and Not Equal.
    663   cc_always = 18,
    664 
    665   // Aliases.
    666   carry = Uless,
    667   not_carry = Ugreater_equal,
    668   zero = equal,
    669   eq = equal,
    670   not_zero = not_equal,
    671   ne = not_equal,
    672   nz = not_equal,
    673   sign = negative,
    674   not_sign = positive,
    675   mi = negative,
    676   pl = positive,
    677   hi = Ugreater,
    678   ls = Uless_equal,
    679   ge = greater_equal,
    680   lt = less,
    681   gt = greater,
    682   le = less_equal,
    683   hs = Ugreater_equal,
    684   lo = Uless,
    685   al = cc_always,
    686   ult = Uless,
    687   uge = Ugreater_equal,
    688   ule = Uless_equal,
    689   ugt = Ugreater,
    690   cc_default = kNoCondition
    691 };
    692 
    693 
    694 // Returns the equivalent of !cc.
    695 // Negation of the default kNoCondition (-1) results in a non-default
    696 // no_condition value (-2). As long as tests for no_condition check
    697 // for condition < 0, this will work as expected.
    698 inline Condition NegateCondition(Condition cc) {
    699   DCHECK(cc != cc_always);
    700   return static_cast<Condition>(cc ^ 1);
    701 }
    702 
    703 
    704 inline Condition NegateFpuCondition(Condition cc) {
    705   DCHECK(cc != cc_always);
    706   switch (cc) {
    707     case ult:
    708       return ge;
    709     case ugt:
    710       return le;
    711     case uge:
    712       return lt;
    713     case ule:
    714       return gt;
    715     case lt:
    716       return uge;
    717     case gt:
    718       return ule;
    719     case ge:
    720       return ult;
    721     case le:
    722       return ugt;
    723     case eq:
    724       return ne;
    725     case ne:
    726       return eq;
    727     case ueq:
    728       return ogl;
    729     case ogl:
    730       return ueq;
    731     default:
    732       return cc;
    733   }
    734 }
    735 
    736 
    737 // Commute a condition such that {a cond b == b cond' a}.
    738 inline Condition CommuteCondition(Condition cc) {
    739   switch (cc) {
    740     case Uless:
    741       return Ugreater;
    742     case Ugreater:
    743       return Uless;
    744     case Ugreater_equal:
    745       return Uless_equal;
    746     case Uless_equal:
    747       return Ugreater_equal;
    748     case less:
    749       return greater;
    750     case greater:
    751       return less;
    752     case greater_equal:
    753       return less_equal;
    754     case less_equal:
    755       return greater_equal;
    756     default:
    757       return cc;
    758   }
    759 }
    760 
    761 
    762 // ----- Coprocessor conditions.
    763 enum FPUCondition {
    764   kNoFPUCondition = -1,
    765 
    766   F = 0x00,    // False.
    767   UN = 0x01,   // Unordered.
    768   EQ = 0x02,   // Equal.
    769   UEQ = 0x03,  // Unordered or Equal.
    770   OLT = 0x04,  // Ordered or Less Than, on Mips release < 6.
    771   LT = 0x04,   // Ordered or Less Than, on Mips release >= 6.
    772   ULT = 0x05,  // Unordered or Less Than.
    773   OLE = 0x06,  // Ordered or Less Than or Equal, on Mips release < 6.
    774   LE = 0x06,   // Ordered or Less Than or Equal, on Mips release >= 6.
    775   ULE = 0x07,  // Unordered or Less Than or Equal.
    776 
    777   // Following constants are available on Mips release >= 6 only.
    778   ORD = 0x11,  // Ordered, on Mips release >= 6.
    779   UNE = 0x12,  // Not equal, on Mips release >= 6.
    780   NE = 0x13,   // Ordered Greater Than or Less Than. on Mips >= 6 only.
    781 };
    782 
    783 
    784 // FPU rounding modes.
    785 enum FPURoundingMode {
    786   RN = 0 << 0,  // Round to Nearest.
    787   RZ = 1 << 0,  // Round towards zero.
    788   RP = 2 << 0,  // Round towards Plus Infinity.
    789   RM = 3 << 0,  // Round towards Minus Infinity.
    790 
    791   // Aliases.
    792   kRoundToNearest = RN,
    793   kRoundToZero = RZ,
    794   kRoundToPlusInf = RP,
    795   kRoundToMinusInf = RM,
    796 
    797   mode_round = RN,
    798   mode_ceil = RP,
    799   mode_floor = RM,
    800   mode_trunc = RZ
    801 };
    802 
    803 const uint32_t kFPURoundingModeMask = 3 << 0;
    804 
    805 enum CheckForInexactConversion {
    806   kCheckForInexactConversion,
    807   kDontCheckForInexactConversion
    808 };
    809 
    810 enum class MaxMinKind : int { kMin = 0, kMax = 1 };
    811 
    812 // -----------------------------------------------------------------------------
    813 // Hints.
    814 
    815 // Branch hints are not used on the MIPS.  They are defined so that they can
    816 // appear in shared function signatures, but will be ignored in MIPS
    817 // implementations.
    818 enum Hint {
    819   no_hint = 0
    820 };
    821 
    822 
    823 inline Hint NegateHint(Hint hint) {
    824   return no_hint;
    825 }
    826 
    827 
    828 // -----------------------------------------------------------------------------
    829 // Specific instructions, constants, and masks.
    830 // These constants are declared in assembler-mips.cc, as they use named
    831 // registers and other constants.
    832 
    833 // addiu(sp, sp, 4) aka Pop() operation or part of Pop(r)
    834 // operations as post-increment of sp.
    835 extern const Instr kPopInstruction;
    836 // addiu(sp, sp, -4) part of Push(r) operation as pre-decrement of sp.
    837 extern const Instr kPushInstruction;
    838 // sw(r, MemOperand(sp, 0))
    839 extern const Instr kPushRegPattern;
    840 // lw(r, MemOperand(sp, 0))
    841 extern const Instr kPopRegPattern;
    842 extern const Instr kLwRegFpOffsetPattern;
    843 extern const Instr kSwRegFpOffsetPattern;
    844 extern const Instr kLwRegFpNegOffsetPattern;
    845 extern const Instr kSwRegFpNegOffsetPattern;
    846 // A mask for the Rt register for push, pop, lw, sw instructions.
    847 extern const Instr kRtMask;
    848 extern const Instr kLwSwInstrTypeMask;
    849 extern const Instr kLwSwInstrArgumentMask;
    850 extern const Instr kLwSwOffsetMask;
    851 
    852 // Break 0xfffff, reserved for redirected real time call.
    853 const Instr rtCallRedirInstr = SPECIAL | BREAK | call_rt_redirected << 6;
    854 // A nop instruction. (Encoding of sll 0 0 0).
    855 const Instr nopInstr = 0;
    856 
    857 static constexpr uint64_t OpcodeToBitNumber(Opcode opcode) {
    858   return 1ULL << (static_cast<uint32_t>(opcode) >> kOpcodeShift);
    859 }
    860 
    861 
    862 class Instruction {
    863  public:
    864   enum {
    865     kInstrSize = 4,
    866     kInstrSizeLog2 = 2,
    867     // On MIPS PC cannot actually be directly accessed. We behave as if PC was
    868     // always the value of the current instruction being executed.
    869     kPCReadOffset = 0
    870   };
    871 
    872   // Get the raw instruction bits.
    873   inline Instr InstructionBits() const {
    874     return *reinterpret_cast<const Instr*>(this);
    875   }
    876 
    877   // Set the raw instruction bits to value.
    878   inline void SetInstructionBits(Instr value) {
    879     *reinterpret_cast<Instr*>(this) = value;
    880   }
    881 
    882   // Read one particular bit out of the instruction bits.
    883   inline int Bit(int nr) const {
    884     return (InstructionBits() >> nr) & 1;
    885   }
    886 
    887   // Read a bit field out of the instruction bits.
    888   inline int Bits(int hi, int lo) const {
    889     return (InstructionBits() >> lo) & ((2U << (hi - lo)) - 1);
    890   }
    891 
    892   // Instruction type.
    893   enum Type {
    894     kRegisterType,
    895     kImmediateType,
    896     kJumpType,
    897     kUnsupported = -1
    898   };
    899 
    900   enum TypeChecks { NORMAL, EXTRA };
    901 
    902 
    903   static constexpr uint64_t kOpcodeImmediateTypeMask =
    904       OpcodeToBitNumber(REGIMM) | OpcodeToBitNumber(BEQ) |
    905       OpcodeToBitNumber(BNE) | OpcodeToBitNumber(BLEZ) |
    906       OpcodeToBitNumber(BGTZ) | OpcodeToBitNumber(ADDI) |
    907       OpcodeToBitNumber(DADDI) | OpcodeToBitNumber(ADDIU) |
    908       OpcodeToBitNumber(SLTI) | OpcodeToBitNumber(SLTIU) |
    909       OpcodeToBitNumber(ANDI) | OpcodeToBitNumber(ORI) |
    910       OpcodeToBitNumber(XORI) | OpcodeToBitNumber(LUI) |
    911       OpcodeToBitNumber(BEQL) | OpcodeToBitNumber(BNEL) |
    912       OpcodeToBitNumber(BLEZL) | OpcodeToBitNumber(BGTZL) |
    913       OpcodeToBitNumber(POP66) | OpcodeToBitNumber(POP76) |
    914       OpcodeToBitNumber(LB) | OpcodeToBitNumber(LH) | OpcodeToBitNumber(LWL) |
    915       OpcodeToBitNumber(LW) | OpcodeToBitNumber(LBU) | OpcodeToBitNumber(LHU) |
    916       OpcodeToBitNumber(LWR) | OpcodeToBitNumber(SB) | OpcodeToBitNumber(SH) |
    917       OpcodeToBitNumber(SWL) | OpcodeToBitNumber(SW) | OpcodeToBitNumber(SWR) |
    918       OpcodeToBitNumber(LWC1) | OpcodeToBitNumber(LDC1) |
    919       OpcodeToBitNumber(SWC1) | OpcodeToBitNumber(SDC1) |
    920       OpcodeToBitNumber(PCREL) | OpcodeToBitNumber(BC) |
    921       OpcodeToBitNumber(BALC);
    922 
    923 #define FunctionFieldToBitNumber(function) (1ULL << function)
    924 
    925   static const uint64_t kFunctionFieldRegisterTypeMask =
    926       FunctionFieldToBitNumber(JR) | FunctionFieldToBitNumber(JALR) |
    927       FunctionFieldToBitNumber(BREAK) | FunctionFieldToBitNumber(SLL) |
    928       FunctionFieldToBitNumber(SRL) | FunctionFieldToBitNumber(SRA) |
    929       FunctionFieldToBitNumber(SLLV) | FunctionFieldToBitNumber(SRLV) |
    930       FunctionFieldToBitNumber(SRAV) | FunctionFieldToBitNumber(LSA) |
    931       FunctionFieldToBitNumber(MFHI) | FunctionFieldToBitNumber(MFLO) |
    932       FunctionFieldToBitNumber(MULT) | FunctionFieldToBitNumber(MULTU) |
    933       FunctionFieldToBitNumber(DIV) | FunctionFieldToBitNumber(DIVU) |
    934       FunctionFieldToBitNumber(ADD) | FunctionFieldToBitNumber(ADDU) |
    935       FunctionFieldToBitNumber(SUB) | FunctionFieldToBitNumber(SUBU) |
    936       FunctionFieldToBitNumber(AND) | FunctionFieldToBitNumber(OR) |
    937       FunctionFieldToBitNumber(XOR) | FunctionFieldToBitNumber(NOR) |
    938       FunctionFieldToBitNumber(SLT) | FunctionFieldToBitNumber(SLTU) |
    939       FunctionFieldToBitNumber(TGE) | FunctionFieldToBitNumber(TGEU) |
    940       FunctionFieldToBitNumber(TLT) | FunctionFieldToBitNumber(TLTU) |
    941       FunctionFieldToBitNumber(TEQ) | FunctionFieldToBitNumber(TNE) |
    942       FunctionFieldToBitNumber(MOVZ) | FunctionFieldToBitNumber(MOVN) |
    943       FunctionFieldToBitNumber(MOVCI) | FunctionFieldToBitNumber(SELEQZ_S) |
    944       FunctionFieldToBitNumber(SELNEZ_S) | FunctionFieldToBitNumber(SYNC);
    945 
    946   // Get the encoding type of the instruction.
    947   inline Type InstructionType(TypeChecks checks = NORMAL) const;
    948 
    949   // Accessors for the different named fields used in the MIPS encoding.
    950   inline Opcode OpcodeValue() const {
    951     return static_cast<Opcode>(
    952         Bits(kOpcodeShift + kOpcodeBits - 1, kOpcodeShift));
    953   }
    954 
    955   inline int RsValue() const {
    956     DCHECK(InstructionType() == kRegisterType ||
    957            InstructionType() == kImmediateType);
    958     return Bits(kRsShift + kRsBits - 1, kRsShift);
    959   }
    960 
    961   inline int RtValue() const {
    962     DCHECK(InstructionType() == kRegisterType ||
    963            InstructionType() == kImmediateType);
    964     return Bits(kRtShift + kRtBits - 1, kRtShift);
    965   }
    966 
    967   inline int RdValue() const {
    968     DCHECK(InstructionType() == kRegisterType);
    969     return Bits(kRdShift + kRdBits - 1, kRdShift);
    970   }
    971 
    972   inline int SaValue() const {
    973     DCHECK(InstructionType() == kRegisterType);
    974     return Bits(kSaShift + kSaBits - 1, kSaShift);
    975   }
    976 
    977   inline int LsaSaValue() const {
    978     DCHECK(InstructionType() == kRegisterType);
    979     return Bits(kSaShift + kLsaSaBits - 1, kSaShift);
    980   }
    981 
    982   inline int FunctionValue() const {
    983     DCHECK(InstructionType() == kRegisterType ||
    984            InstructionType() == kImmediateType);
    985     return Bits(kFunctionShift + kFunctionBits - 1, kFunctionShift);
    986   }
    987 
    988   inline int FdValue() const {
    989     return Bits(kFdShift + kFdBits - 1, kFdShift);
    990   }
    991 
    992   inline int FsValue() const {
    993     return Bits(kFsShift + kFsBits - 1, kFsShift);
    994   }
    995 
    996   inline int FtValue() const {
    997     return Bits(kFtShift + kFtBits - 1, kFtShift);
    998   }
    999 
   1000   inline int FrValue() const {
   1001     return Bits(kFrShift + kFrBits -1, kFrShift);
   1002   }
   1003 
   1004   inline int Bp2Value() const {
   1005     DCHECK(InstructionType() == kRegisterType);
   1006     return Bits(kBp2Shift + kBp2Bits - 1, kBp2Shift);
   1007   }
   1008 
   1009   // Float Compare condition code instruction bits.
   1010   inline int FCccValue() const {
   1011     return Bits(kFCccShift + kFCccBits - 1, kFCccShift);
   1012   }
   1013 
   1014   // Float Branch condition code instruction bits.
   1015   inline int FBccValue() const {
   1016     return Bits(kFBccShift + kFBccBits - 1, kFBccShift);
   1017   }
   1018 
   1019   // Float Branch true/false instruction bit.
   1020   inline int FBtrueValue() const {
   1021     return Bits(kFBtrueShift + kFBtrueBits - 1, kFBtrueShift);
   1022   }
   1023 
   1024   // Return the fields at their original place in the instruction encoding.
   1025   inline Opcode OpcodeFieldRaw() const {
   1026     return static_cast<Opcode>(InstructionBits() & kOpcodeMask);
   1027   }
   1028 
   1029   inline int RsFieldRaw() const {
   1030     DCHECK(InstructionType() == kRegisterType ||
   1031            InstructionType() == kImmediateType);
   1032     return InstructionBits() & kRsFieldMask;
   1033   }
   1034 
   1035   // Same as above function, but safe to call within InstructionType().
   1036   inline int RsFieldRawNoAssert() const {
   1037     return InstructionBits() & kRsFieldMask;
   1038   }
   1039 
   1040   inline int RtFieldRaw() const {
   1041     DCHECK(InstructionType() == kRegisterType ||
   1042            InstructionType() == kImmediateType);
   1043     return InstructionBits() & kRtFieldMask;
   1044   }
   1045 
   1046   inline int RdFieldRaw() const {
   1047     DCHECK(InstructionType() == kRegisterType);
   1048     return InstructionBits() & kRdFieldMask;
   1049   }
   1050 
   1051   inline int SaFieldRaw() const {
   1052     return InstructionBits() & kSaFieldMask;
   1053   }
   1054 
   1055   inline int FunctionFieldRaw() const {
   1056     return InstructionBits() & kFunctionFieldMask;
   1057   }
   1058 
   1059   // Get the secondary field according to the opcode.
   1060   inline int SecondaryValue() const {
   1061     Opcode op = OpcodeFieldRaw();
   1062     switch (op) {
   1063       case SPECIAL:
   1064       case SPECIAL2:
   1065         return FunctionValue();
   1066       case COP1:
   1067         return RsValue();
   1068       case REGIMM:
   1069         return RtValue();
   1070       default:
   1071         return NULLSF;
   1072     }
   1073   }
   1074 
   1075   inline int32_t ImmValue(int bits) const {
   1076     DCHECK(InstructionType() == kImmediateType);
   1077     return Bits(bits - 1, 0);
   1078   }
   1079 
   1080   inline int32_t Imm16Value() const {
   1081     DCHECK(InstructionType() == kImmediateType);
   1082     return Bits(kImm16Shift + kImm16Bits - 1, kImm16Shift);
   1083   }
   1084 
   1085   inline int32_t Imm18Value() const {
   1086     DCHECK(InstructionType() == kImmediateType);
   1087     return Bits(kImm18Shift + kImm18Bits - 1, kImm18Shift);
   1088   }
   1089 
   1090   inline int32_t Imm19Value() const {
   1091     DCHECK(InstructionType() == kImmediateType);
   1092     return Bits(kImm19Shift + kImm19Bits - 1, kImm19Shift);
   1093   }
   1094 
   1095   inline int32_t Imm21Value() const {
   1096     DCHECK(InstructionType() == kImmediateType);
   1097     return Bits(kImm21Shift + kImm21Bits - 1, kImm21Shift);
   1098   }
   1099 
   1100   inline int32_t Imm26Value() const {
   1101     DCHECK((InstructionType() == kJumpType) ||
   1102            (InstructionType() == kImmediateType));
   1103     return Bits(kImm26Shift + kImm26Bits - 1, kImm26Shift);
   1104   }
   1105 
   1106   static bool IsForbiddenAfterBranchInstr(Instr instr);
   1107 
   1108   // Say if the instruction should not be used in a branch delay slot or
   1109   // immediately after a compact branch.
   1110   inline bool IsForbiddenAfterBranch() const {
   1111     return IsForbiddenAfterBranchInstr(InstructionBits());
   1112   }
   1113 
   1114   inline bool IsForbiddenInBranchDelay() const {
   1115     return IsForbiddenAfterBranch();
   1116   }
   1117 
   1118   // Say if the instruction 'links'. e.g. jal, bal.
   1119   bool IsLinkingInstruction() const;
   1120   // Say if the instruction is a break or a trap.
   1121   bool IsTrap() const;
   1122 
   1123   // Instructions are read of out a code stream. The only way to get a
   1124   // reference to an instruction is to convert a pointer. There is no way
   1125   // to allocate or create instances of class Instruction.
   1126   // Use the At(pc) function to create references to Instruction.
   1127   static Instruction* At(byte* pc) {
   1128     return reinterpret_cast<Instruction*>(pc);
   1129   }
   1130 
   1131  private:
   1132   // We need to prevent the creation of instances of class Instruction.
   1133   DISALLOW_IMPLICIT_CONSTRUCTORS(Instruction);
   1134 };
   1135 
   1136 
   1137 // -----------------------------------------------------------------------------
   1138 // MIPS assembly various constants.
   1139 
   1140 // C/C++ argument slots size.
   1141 const int kCArgSlotCount = 4;
   1142 const int kCArgsSlotsSize = kCArgSlotCount * Instruction::kInstrSize;
   1143 const int kInvalidStackOffset = -1;
   1144 // JS argument slots size.
   1145 const int kJSArgsSlotsSize = 0 * Instruction::kInstrSize;
   1146 // Assembly builtins argument slots size.
   1147 const int kBArgsSlotsSize = 0 * Instruction::kInstrSize;
   1148 
   1149 const int kBranchReturnOffset = 2 * Instruction::kInstrSize;
   1150 
   1151 
   1152 Instruction::Type Instruction::InstructionType(TypeChecks checks) const {
   1153   if (checks == EXTRA) {
   1154     if (OpcodeToBitNumber(OpcodeFieldRaw()) & kOpcodeImmediateTypeMask) {
   1155       return kImmediateType;
   1156     }
   1157   }
   1158   switch (OpcodeFieldRaw()) {
   1159     case SPECIAL:
   1160       if (checks == EXTRA) {
   1161         if (FunctionFieldToBitNumber(FunctionFieldRaw()) &
   1162             kFunctionFieldRegisterTypeMask) {
   1163           return kRegisterType;
   1164         } else {
   1165           return kUnsupported;
   1166         }
   1167       } else {
   1168         return kRegisterType;
   1169       }
   1170       break;
   1171     case SPECIAL2:
   1172       switch (FunctionFieldRaw()) {
   1173         case MUL:
   1174         case CLZ:
   1175           return kRegisterType;
   1176         default:
   1177           return kUnsupported;
   1178       }
   1179       break;
   1180     case SPECIAL3:
   1181       switch (FunctionFieldRaw()) {
   1182         case INS:
   1183         case EXT:
   1184           return kRegisterType;
   1185         case BSHFL: {
   1186           int sa = SaFieldRaw() >> kSaShift;
   1187           switch (sa) {
   1188             case BITSWAP:
   1189             case WSBH:
   1190             case SEB:
   1191             case SEH:
   1192               return kRegisterType;
   1193           }
   1194           sa >>= kBp2Bits;
   1195           switch (sa) {
   1196             case ALIGN:
   1197               return kRegisterType;
   1198             default:
   1199               return kUnsupported;
   1200           }
   1201         }
   1202         default:
   1203           return kUnsupported;
   1204       }
   1205       break;
   1206     case COP1:  // Coprocessor instructions.
   1207       switch (RsFieldRawNoAssert()) {
   1208         case BC1:  // Branch on coprocessor condition.
   1209         case BC1EQZ:
   1210         case BC1NEZ:
   1211           return kImmediateType;
   1212         default:
   1213           return kRegisterType;
   1214       }
   1215       break;
   1216     case COP1X:
   1217       return kRegisterType;
   1218 
   1219     // 26 bits immediate type instructions. e.g.: j imm26.
   1220     case J:
   1221     case JAL:
   1222       return kJumpType;
   1223 
   1224     default:
   1225       if (checks == NORMAL) {
   1226         return kImmediateType;
   1227       } else {
   1228         return kUnsupported;
   1229       }
   1230   }
   1231 }
   1232 
   1233 #undef OpcodeToBitNumber
   1234 #undef FunctionFieldToBitNumber
   1235 }  // namespace internal
   1236 }  // namespace v8
   1237 
   1238 #endif    // #ifndef V8_MIPS_CONSTANTS_H_
   1239