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Cpu-vixl.cpp (16255B)


      1 // Copyright 2015, VIXL authors
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are met:
      6 //
      7 //   * Redistributions of source code must retain the above copyright notice,
      8 //     this list of conditions and the following disclaimer.
      9 //   * Redistributions in binary form must reproduce the above copyright notice,
     10 //     this list of conditions and the following disclaimer in the documentation
     11 //     and/or other materials provided with the distribution.
     12 //   * Neither the name of ARM Limited nor the names of its contributors may be
     13 //     used to endorse or promote products derived from this software without
     14 //     specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
     17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
     20 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     22 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     23 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26 
     27 #include "jit/arm64/vixl/Cpu-vixl.h"
     28 
     29 #include "jstypes.h"
     30 
     31 #if defined(__aarch64__) && (defined(__ANDROID__) || defined(__linux__))
     32 #include <sys/auxv.h>
     33 #define VIXL_USE_LINUX_HWCAP 1
     34 #endif
     35 
     36 #include "jit/arm64/vixl/Utils-vixl.h"
     37 
     38 
     39 namespace vixl {
     40 
     41 
     42 const IDRegister::Field AA64PFR0::kFP(16, Field::kSigned);
     43 const IDRegister::Field AA64PFR0::kAdvSIMD(20, Field::kSigned);
     44 const IDRegister::Field AA64PFR0::kRAS(28);
     45 const IDRegister::Field AA64PFR0::kSVE(32);
     46 const IDRegister::Field AA64PFR0::kDIT(48);
     47 const IDRegister::Field AA64PFR0::kCSV2(56);
     48 const IDRegister::Field AA64PFR0::kCSV3(60);
     49 
     50 const IDRegister::Field AA64PFR1::kBT(0);
     51 const IDRegister::Field AA64PFR1::kSSBS(4);
     52 const IDRegister::Field AA64PFR1::kMTE(8);
     53 const IDRegister::Field AA64PFR1::kSME(24);
     54 
     55 const IDRegister::Field AA64ISAR0::kAES(4);
     56 const IDRegister::Field AA64ISAR0::kSHA1(8);
     57 const IDRegister::Field AA64ISAR0::kSHA2(12);
     58 const IDRegister::Field AA64ISAR0::kCRC32(16);
     59 const IDRegister::Field AA64ISAR0::kAtomic(20);
     60 const IDRegister::Field AA64ISAR0::kRDM(28);
     61 const IDRegister::Field AA64ISAR0::kSHA3(32);
     62 const IDRegister::Field AA64ISAR0::kSM3(36);
     63 const IDRegister::Field AA64ISAR0::kSM4(40);
     64 const IDRegister::Field AA64ISAR0::kDP(44);
     65 const IDRegister::Field AA64ISAR0::kFHM(48);
     66 const IDRegister::Field AA64ISAR0::kTS(52);
     67 const IDRegister::Field AA64ISAR0::kRNDR(60);
     68 
     69 const IDRegister::Field AA64ISAR1::kDPB(0);
     70 const IDRegister::Field AA64ISAR1::kAPA(4);
     71 const IDRegister::Field AA64ISAR1::kAPI(8);
     72 const IDRegister::Field AA64ISAR1::kJSCVT(12);
     73 const IDRegister::Field AA64ISAR1::kFCMA(16);
     74 const IDRegister::Field AA64ISAR1::kLRCPC(20);
     75 const IDRegister::Field AA64ISAR1::kGPA(24);
     76 const IDRegister::Field AA64ISAR1::kGPI(28);
     77 const IDRegister::Field AA64ISAR1::kFRINTTS(32);
     78 const IDRegister::Field AA64ISAR1::kSB(36);
     79 const IDRegister::Field AA64ISAR1::kSPECRES(40);
     80 const IDRegister::Field AA64ISAR1::kBF16(44);
     81 const IDRegister::Field AA64ISAR1::kDGH(48);
     82 const IDRegister::Field AA64ISAR1::kI8MM(52);
     83 
     84 const IDRegister::Field AA64ISAR2::kWFXT(0);
     85 const IDRegister::Field AA64ISAR2::kRPRES(4);
     86 const IDRegister::Field AA64ISAR2::kMOPS(16);
     87 const IDRegister::Field AA64ISAR2::kCSSC(52);
     88 
     89 const IDRegister::Field AA64MMFR0::kECV(60);
     90 
     91 const IDRegister::Field AA64MMFR1::kLO(16);
     92 const IDRegister::Field AA64MMFR1::kAFP(44);
     93 
     94 const IDRegister::Field AA64MMFR2::kAT(32);
     95 
     96 const IDRegister::Field AA64ZFR0::kSVEver(0);
     97 const IDRegister::Field AA64ZFR0::kAES(4);
     98 const IDRegister::Field AA64ZFR0::kBitPerm(16);
     99 const IDRegister::Field AA64ZFR0::kBF16(20);
    100 const IDRegister::Field AA64ZFR0::kSHA3(32);
    101 const IDRegister::Field AA64ZFR0::kSM4(40);
    102 const IDRegister::Field AA64ZFR0::kI8MM(44);
    103 const IDRegister::Field AA64ZFR0::kF32MM(52);
    104 const IDRegister::Field AA64ZFR0::kF64MM(56);
    105 
    106 const IDRegister::Field AA64SMFR0::kSMEf32f32(32, 1);
    107 const IDRegister::Field AA64SMFR0::kSMEb16f32(34, 1);
    108 const IDRegister::Field AA64SMFR0::kSMEf16f32(35, 1);
    109 const IDRegister::Field AA64SMFR0::kSMEi8i32(36);
    110 const IDRegister::Field AA64SMFR0::kSMEf64f64(48, 1);
    111 const IDRegister::Field AA64SMFR0::kSMEi16i64(52);
    112 const IDRegister::Field AA64SMFR0::kSMEfa64(63, 1);
    113 
    114 CPUFeatures AA64PFR0::GetCPUFeatures() const {
    115  CPUFeatures f;
    116  if (Get(kFP) >= 0) f.Combine(CPUFeatures::kFP);
    117  if (Get(kFP) >= 1) f.Combine(CPUFeatures::kFPHalf);
    118  if (Get(kAdvSIMD) >= 0) f.Combine(CPUFeatures::kNEON);
    119  if (Get(kAdvSIMD) >= 1) f.Combine(CPUFeatures::kNEONHalf);
    120  if (Get(kRAS) >= 1) f.Combine(CPUFeatures::kRAS);
    121  if (Get(kSVE) >= 1) f.Combine(CPUFeatures::kSVE);
    122  if (Get(kDIT) >= 1) f.Combine(CPUFeatures::kDIT);
    123  if (Get(kCSV2) >= 1) f.Combine(CPUFeatures::kCSV2);
    124  if (Get(kCSV2) >= 2) f.Combine(CPUFeatures::kSCXTNUM);
    125  if (Get(kCSV3) >= 1) f.Combine(CPUFeatures::kCSV3);
    126  return f;
    127 }
    128 
    129 CPUFeatures AA64PFR1::GetCPUFeatures() const {
    130  CPUFeatures f;
    131  if (Get(kBT) >= 1) f.Combine(CPUFeatures::kBTI);
    132  if (Get(kSSBS) >= 1) f.Combine(CPUFeatures::kSSBS);
    133  if (Get(kSSBS) >= 2) f.Combine(CPUFeatures::kSSBSControl);
    134  if (Get(kMTE) >= 1) f.Combine(CPUFeatures::kMTEInstructions);
    135  if (Get(kMTE) >= 2) f.Combine(CPUFeatures::kMTE);
    136  if (Get(kMTE) >= 3) f.Combine(CPUFeatures::kMTE3);
    137  if (Get(kSME) >= 1) f.Combine(CPUFeatures::kSME);
    138  return f;
    139 }
    140 
    141 CPUFeatures AA64ISAR0::GetCPUFeatures() const {
    142  CPUFeatures f;
    143  if (Get(kAES) >= 1) f.Combine(CPUFeatures::kAES);
    144  if (Get(kAES) >= 2) f.Combine(CPUFeatures::kPmull1Q);
    145  if (Get(kSHA1) >= 1) f.Combine(CPUFeatures::kSHA1);
    146  if (Get(kSHA2) >= 1) f.Combine(CPUFeatures::kSHA2);
    147  if (Get(kSHA2) >= 2) f.Combine(CPUFeatures::kSHA512);
    148  if (Get(kCRC32) >= 1) f.Combine(CPUFeatures::kCRC32);
    149  if (Get(kAtomic) >= 1) f.Combine(CPUFeatures::kAtomics);
    150  if (Get(kRDM) >= 1) f.Combine(CPUFeatures::kRDM);
    151  if (Get(kSHA3) >= 1) f.Combine(CPUFeatures::kSHA3);
    152  if (Get(kSM3) >= 1) f.Combine(CPUFeatures::kSM3);
    153  if (Get(kSM4) >= 1) f.Combine(CPUFeatures::kSM4);
    154  if (Get(kDP) >= 1) f.Combine(CPUFeatures::kDotProduct);
    155  if (Get(kFHM) >= 1) f.Combine(CPUFeatures::kFHM);
    156  if (Get(kTS) >= 1) f.Combine(CPUFeatures::kFlagM);
    157  if (Get(kTS) >= 2) f.Combine(CPUFeatures::kAXFlag);
    158  if (Get(kRNDR) >= 1) f.Combine(CPUFeatures::kRNG);
    159  return f;
    160 }
    161 
    162 CPUFeatures AA64ISAR1::GetCPUFeatures() const {
    163  CPUFeatures f;
    164  if (Get(kDPB) >= 1) f.Combine(CPUFeatures::kDCPoP);
    165  if (Get(kDPB) >= 2) f.Combine(CPUFeatures::kDCCVADP);
    166  if (Get(kJSCVT) >= 1) f.Combine(CPUFeatures::kJSCVT);
    167  if (Get(kFCMA) >= 1) f.Combine(CPUFeatures::kFcma);
    168  if (Get(kLRCPC) >= 1) f.Combine(CPUFeatures::kRCpc);
    169  if (Get(kLRCPC) >= 2) f.Combine(CPUFeatures::kRCpcImm);
    170  if (Get(kFRINTTS) >= 1) f.Combine(CPUFeatures::kFrintToFixedSizedInt);
    171  if (Get(kSB) >= 1) f.Combine(CPUFeatures::kSB);
    172  if (Get(kSPECRES) >= 1) f.Combine(CPUFeatures::kSPECRES);
    173  if (Get(kBF16) >= 1) f.Combine(CPUFeatures::kBF16);
    174  if (Get(kBF16) >= 2) f.Combine(CPUFeatures::kEBF16);
    175  if (Get(kDGH) >= 1) f.Combine(CPUFeatures::kDGH);
    176  if (Get(kI8MM) >= 1) f.Combine(CPUFeatures::kI8MM);
    177 
    178  // Only one of these fields should be non-zero, but they have the same
    179  // encodings, so merge the logic.
    180  int apx = std::max(Get(kAPI), Get(kAPA));
    181  if (apx >= 1) {
    182    f.Combine(CPUFeatures::kPAuth);
    183    // APA (rather than API) indicates QARMA.
    184    if (Get(kAPA) >= 1) f.Combine(CPUFeatures::kPAuthQARMA);
    185    if (apx == 0b0010) f.Combine(CPUFeatures::kPAuthEnhancedPAC);
    186    if (apx >= 0b0011) f.Combine(CPUFeatures::kPAuthEnhancedPAC2);
    187    if (apx >= 0b0100) f.Combine(CPUFeatures::kPAuthFPAC);
    188    if (apx >= 0b0101) f.Combine(CPUFeatures::kPAuthFPACCombined);
    189  }
    190 
    191  if (Get(kGPI) >= 1) f.Combine(CPUFeatures::kPAuthGeneric);
    192  if (Get(kGPA) >= 1) {
    193    f.Combine(CPUFeatures::kPAuthGeneric, CPUFeatures::kPAuthGenericQARMA);
    194  }
    195  return f;
    196 }
    197 
    198 CPUFeatures AA64ISAR2::GetCPUFeatures() const {
    199  CPUFeatures f;
    200  if (Get(kWFXT) >= 2) f.Combine(CPUFeatures::kWFXT);
    201  if (Get(kRPRES) >= 1) f.Combine(CPUFeatures::kRPRES);
    202  if (Get(kMOPS) >= 1) f.Combine(CPUFeatures::kMOPS);
    203  if (Get(kCSSC) >= 1) f.Combine(CPUFeatures::kCSSC);
    204  return f;
    205 }
    206 
    207 CPUFeatures AA64MMFR0::GetCPUFeatures() const {
    208  CPUFeatures f;
    209  if (Get(kECV) >= 1) f.Combine(CPUFeatures::kECV);
    210  return f;
    211 }
    212 
    213 CPUFeatures AA64MMFR1::GetCPUFeatures() const {
    214  CPUFeatures f;
    215  if (Get(kLO) >= 1) f.Combine(CPUFeatures::kLORegions);
    216  if (Get(kAFP) >= 1) f.Combine(CPUFeatures::kAFP);
    217  return f;
    218 }
    219 
    220 CPUFeatures AA64MMFR2::GetCPUFeatures() const {
    221  CPUFeatures f;
    222  if (Get(kAT) >= 1) f.Combine(CPUFeatures::kUSCAT);
    223  return f;
    224 }
    225 
    226 CPUFeatures AA64ZFR0::GetCPUFeatures() const {
    227  // This register is only available with SVE, but reads-as-zero in its absence,
    228  // so it's always safe to read it.
    229  CPUFeatures f;
    230  if (Get(kF64MM) >= 1) f.Combine(CPUFeatures::kSVEF64MM);
    231  if (Get(kF32MM) >= 1) f.Combine(CPUFeatures::kSVEF32MM);
    232  if (Get(kI8MM) >= 1) f.Combine(CPUFeatures::kSVEI8MM);
    233  if (Get(kSM4) >= 1) f.Combine(CPUFeatures::kSVESM4);
    234  if (Get(kSHA3) >= 1) f.Combine(CPUFeatures::kSVESHA3);
    235  if (Get(kBF16) >= 1) f.Combine(CPUFeatures::kSVEBF16);
    236  if (Get(kBF16) >= 2) f.Combine(CPUFeatures::kSVE_EBF16);
    237  if (Get(kBitPerm) >= 1) f.Combine(CPUFeatures::kSVEBitPerm);
    238  if (Get(kAES) >= 1) f.Combine(CPUFeatures::kSVEAES);
    239  if (Get(kAES) >= 2) f.Combine(CPUFeatures::kSVEPmull128);
    240  if (Get(kSVEver) >= 1) f.Combine(CPUFeatures::kSVE2);
    241  return f;
    242 }
    243 
    244 CPUFeatures AA64SMFR0::GetCPUFeatures() const {
    245  CPUFeatures f;
    246  if (Get(kSMEf32f32) >= 1) f.Combine(CPUFeatures::kSMEf32f32);
    247  if (Get(kSMEb16f32) >= 1) f.Combine(CPUFeatures::kSMEb16f32);
    248  if (Get(kSMEf16f32) >= 1) f.Combine(CPUFeatures::kSMEf16f32);
    249  if (Get(kSMEi8i32) >= 15) f.Combine(CPUFeatures::kSMEi8i32);
    250  if (Get(kSMEf64f64) >= 1) f.Combine(CPUFeatures::kSMEf64f64);
    251  if (Get(kSMEi16i64) >= 15) f.Combine(CPUFeatures::kSMEi16i64);
    252  if (Get(kSMEfa64) >= 1) f.Combine(CPUFeatures::kSMEfa64);
    253  return f;
    254 }
    255 
    256 int IDRegister::Get(IDRegister::Field field) const {
    257  int msb = field.GetMsb();
    258  int lsb = field.GetLsb();
    259  VIXL_STATIC_ASSERT(static_cast<size_t>(Field::kMaxWidthInBits) <
    260                     (sizeof(int) * kBitsPerByte));
    261  switch (field.GetType()) {
    262    case Field::kSigned:
    263      return static_cast<int>(ExtractSignedBitfield64(msb, lsb, value_));
    264    case Field::kUnsigned:
    265      return static_cast<int>(ExtractUnsignedBitfield64(msb, lsb, value_));
    266  }
    267  VIXL_UNREACHABLE();
    268  return 0;
    269 }
    270 
    271 CPUFeatures CPU::InferCPUFeaturesFromIDRegisters() {
    272  CPUFeatures f;
    273 #define VIXL_COMBINE_ID_REG(NAME, MRS_ARG) \
    274  f.Combine(Read##NAME().GetCPUFeatures());
    275  VIXL_AARCH64_ID_REG_LIST(VIXL_COMBINE_ID_REG)
    276 #undef VIXL_COMBINE_ID_REG
    277  return f;
    278 }
    279 
    280 CPUFeatures CPU::InferCPUFeaturesFromOS(
    281    CPUFeatures::QueryIDRegistersOption option) {
    282  CPUFeatures features;
    283 
    284 #ifdef VIXL_USE_LINUX_HWCAP
    285  // Map each set bit onto a feature. Ideally, we'd use HWCAP_* macros rather
    286  // than explicit bits, but explicit bits allow us to identify features that
    287  // the toolchain doesn't know about.
    288  static const CPUFeatures::Feature kFeatureBitsLow[] =
    289      {// Bits 0-7
    290       CPUFeatures::kFP,
    291       CPUFeatures::kNEON,
    292       CPUFeatures::kNone,  // "EVTSTRM", which VIXL doesn't track.
    293       CPUFeatures::kAES,
    294       CPUFeatures::kPmull1Q,
    295       CPUFeatures::kSHA1,
    296       CPUFeatures::kSHA2,
    297       CPUFeatures::kCRC32,
    298       // Bits 8-15
    299       CPUFeatures::kAtomics,
    300       CPUFeatures::kFPHalf,
    301       CPUFeatures::kNEONHalf,
    302       CPUFeatures::kIDRegisterEmulation,
    303       CPUFeatures::kRDM,
    304       CPUFeatures::kJSCVT,
    305       CPUFeatures::kFcma,
    306       CPUFeatures::kRCpc,
    307       // Bits 16-23
    308       CPUFeatures::kDCPoP,
    309       CPUFeatures::kSHA3,
    310       CPUFeatures::kSM3,
    311       CPUFeatures::kSM4,
    312       CPUFeatures::kDotProduct,
    313       CPUFeatures::kSHA512,
    314       CPUFeatures::kSVE,
    315       CPUFeatures::kFHM,
    316       // Bits 24-31
    317       CPUFeatures::kDIT,
    318       CPUFeatures::kUSCAT,
    319       CPUFeatures::kRCpcImm,
    320       CPUFeatures::kFlagM,
    321       CPUFeatures::kSSBSControl,
    322       CPUFeatures::kSB,
    323       CPUFeatures::kPAuth,
    324       CPUFeatures::kPAuthGeneric};
    325  VIXL_STATIC_ASSERT(ArrayLength(kFeatureBitsLow) < 64);
    326 
    327  static const CPUFeatures::Feature kFeatureBitsHigh[] =
    328      {// Bits 0-7
    329       CPUFeatures::kDCCVADP,
    330       CPUFeatures::kSVE2,
    331       CPUFeatures::kSVEAES,
    332       CPUFeatures::kSVEPmull128,
    333       CPUFeatures::kSVEBitPerm,
    334       CPUFeatures::kSVESHA3,
    335       CPUFeatures::kSVESM4,
    336       CPUFeatures::kAXFlag,
    337       // Bits 8-15
    338       CPUFeatures::kFrintToFixedSizedInt,
    339       CPUFeatures::kSVEI8MM,
    340       CPUFeatures::kSVEF32MM,
    341       CPUFeatures::kSVEF64MM,
    342       CPUFeatures::kSVEBF16,
    343       CPUFeatures::kI8MM,
    344       CPUFeatures::kBF16,
    345       CPUFeatures::kDGH,
    346       // Bits 16-23
    347       CPUFeatures::kRNG,
    348       CPUFeatures::kBTI,
    349       CPUFeatures::kMTE,
    350       CPUFeatures::kECV,
    351       CPUFeatures::kAFP,
    352       CPUFeatures::kRPRES,
    353       CPUFeatures::kMTE3,
    354       CPUFeatures::kSME,
    355       // Bits 24-31
    356       CPUFeatures::kSMEi16i64,
    357       CPUFeatures::kSMEf64f64,
    358       CPUFeatures::kSMEi8i32,
    359       CPUFeatures::kSMEf16f32,
    360       CPUFeatures::kSMEb16f32,
    361       CPUFeatures::kSMEf32f32,
    362       CPUFeatures::kSMEfa64,
    363       CPUFeatures::kWFXT,
    364       // Bits 32-39
    365       CPUFeatures::kEBF16,
    366       CPUFeatures::kSVE_EBF16};
    367  VIXL_STATIC_ASSERT(ArrayLength(kFeatureBitsHigh) < 64);
    368 
    369  auto combine_features = [&features](uint64_t hwcap,
    370                                      const CPUFeatures::Feature* feature_array,
    371                                      size_t features_size) {
    372    for (size_t i = 0; i < features_size; i++) {
    373      if (hwcap & (UINT64_C(1) << i)) features.Combine(feature_array[i]);
    374    }
    375  };
    376 
    377  uint64_t hwcap_low = getauxval(AT_HWCAP);
    378  uint64_t hwcap_high = getauxval(AT_HWCAP2);
    379 
    380  combine_features(hwcap_low, kFeatureBitsLow, ArrayLength(kFeatureBitsLow));
    381  combine_features(hwcap_high, kFeatureBitsHigh, ArrayLength(kFeatureBitsHigh));
    382 
    383  // MTE support from HWCAP2 signifies FEAT_MTE1 and FEAT_MTE2 support
    384  if (features.Has(CPUFeatures::kMTE)) {
    385    features.Combine(CPUFeatures::kMTEInstructions);
    386  }
    387 #elif defined(XP_DARWIN)
    388  // Apple processors have kJSCVT, kDotProduct, and kAtomics features.
    389  features.Combine(CPUFeatures::kJSCVT, CPUFeatures::kDotProduct,
    390                   CPUFeatures::kAtomics);
    391 #endif  // VIXL_USE_LINUX_HWCAP
    392 
    393  if ((option == CPUFeatures::kQueryIDRegistersIfAvailable) &&
    394      (features.Has(CPUFeatures::kIDRegisterEmulation))) {
    395    features.Combine(InferCPUFeaturesFromIDRegisters());
    396  }
    397  return features;
    398 }
    399 
    400 
    401 #ifdef __aarch64__
    402 #define VIXL_READ_ID_REG(NAME, MRS_ARG)        \
    403  NAME CPU::Read##NAME() {                     \
    404    uint64_t value = 0;                        \
    405    __asm__("mrs %0, " MRS_ARG : "=r"(value)); \
    406    return NAME(value);                        \
    407  }
    408 #else  // __aarch64__
    409 #define VIXL_READ_ID_REG(NAME, MRS_ARG) \
    410  NAME CPU::Read##NAME() {              \
    411    VIXL_UNREACHABLE();                 \
    412    return NAME(0);                     \
    413  }
    414 #endif  // __aarch64__
    415 
    416 VIXL_AARCH64_ID_REG_LIST(VIXL_READ_ID_REG)
    417 
    418 #undef VIXL_READ_ID_REG
    419 
    420 
    421 // Initialise to smallest possible cache size.
    422 unsigned CPU::dcache_line_size_ = 1;
    423 unsigned CPU::icache_line_size_ = 1;
    424 
    425 
    426 // Query the SVE vector length. This requires CPUFeatures::kSVE.
    427 int CPU::ReadSVEVectorLengthInBits() {
    428 #ifdef __aarch64__
    429  uint64_t vl;
    430  // To support compilers that don't understand `rdvl`, encode the value
    431  // directly and move it manually.
    432  __asm__(
    433      "   .word 0x04bf5100\n"  // rdvl x0, #8
    434      "   mov %[vl], x0\n"
    435      : [vl] "=r"(vl)
    436      :
    437      : "x0");
    438  VIXL_ASSERT(vl <= INT_MAX);
    439  return static_cast<int>(vl);
    440 #else
    441  VIXL_UNREACHABLE();
    442  return 0;
    443 #endif
    444 }
    445 
    446 
    447 }  // namespace vixl