riscv/processor.cc

   1 // See LICENSE for license details.
   2
   3 #include "processor.h"
   4 #include "extension.h"
   5 #include "common.h"
   6 #include "config.h"
   7 #include "sim.h"
   8 #include "mmu.h"
   9 #include "htif.h"
  10 #include "disasm.h"
  11 #include <cinttypes>
  12 #include <cmath>
  13 #include <cstdlib>
  14 #include <iostream>
  15 #include <assert.h>
  16 #include <limits.h>
  17 #include <stdexcept>
  18 #include <algorithm>
  19
  20 #undef STATE
  21 #define STATE state
  22
  23 processor_t::processor_t(const char* isa, sim_t* sim, uint32_t id)
  24   : sim(sim), ext(NULL), disassembler(new disassembler_t),
  25     id(id), run(false), debug(false), halted(false), single_step(false)
  26 {
  27   parse_isa_string(isa);
  28
  29   mmu = new mmu_t(sim, this);
  30
  31   reset(true);
  32
  33   register_base_instructions();
  34 }
  35
  36 processor_t::~processor_t()
  37 {
  38 #ifdef RISCV_ENABLE_HISTOGRAM
  39   if (histogram_enabled)
  40   {
  41     fprintf(stderr, "PC Histogram size:%zu\n", pc_histogram.size());
  42     for (auto it : pc_histogram)
  43       fprintf(stderr, "%0" PRIx64 " %" PRIu64 "\n", it.first, it.second);
  44   }
  45 #endif
  46
  47   delete mmu;
  48   delete disassembler;
  49 }
  50
  51 static void bad_isa_string(const char* isa)
  52 {
  53   fprintf(stderr, "error: bad --isa option %s\n", isa);
  54   abort();
  55 }
  56
  57 void processor_t::parse_isa_string(const char* str)
  58 {
  59   std::string lowercase, tmp;
  60   for (const char *r = str; *r; r++)
  61     lowercase += std::tolower(*r);
  62
  63   const char* p = lowercase.c_str();
  64   const char* all_subsets = "imafdc";
  65
  66   max_xlen = 64;
  67   isa = reg_t(2) << 62;
  68
  69   if (strncmp(p, "rv32", 4) == 0)
  70     max_xlen = 32, isa = reg_t(1) << 30, p += 4;
  71   else if (strncmp(p, "rv64", 4) == 0)
  72     p += 4;
  73   else if (strncmp(p, "rv", 2) == 0)
  74     p += 2;
  75
  76   if (!*p) {
  77     p = all_subsets;
  78   } else if (*p == 'g') { // treat "G" as "IMAFD"
  79     tmp = std::string("imafd") + (p+1);
  80     p = &tmp[0];
  81   } else if (*p != 'i') {
  82     bad_isa_string(str);
  83   }
  84
  85   isa_string = "rv" + std::to_string(max_xlen) + p;
  86   isa |= 1L << ('s' - 'a'); // advertise support for supervisor mode
  87
  88   while (*p) {
  89     isa |= 1L << (*p - 'a');
  90
  91     if (auto next = strchr(all_subsets, *p)) {
  92       all_subsets = next + 1;
  93       p++;
  94     } else if (*p == 'x') {
  95       const char* ext = p+1, *end = ext;
  96       while (islower(*end))
  97         end++;
  98       register_extension(find_extension(std::string(ext, end - ext).c_str())());
  99       p = end;
 100     } else {
 101       bad_isa_string(str);
 102     }
 103   }
 104
 105   if (supports_extension('D') && !supports_extension('F'))
 106     bad_isa_string(str);
 107
 108   // advertise support for supervisor and user modes
 109   isa |= 1L << ('s' - 'a');
 110   isa |= 1L << ('u' - 'a');
 111 }
 112
 113 void state_t::reset()
 114 {
 115   memset(this, 0, sizeof(*this));
 116   prv = PRV_M;
 117   pc = DEFAULT_RSTVEC;
 118   mtvec = DEFAULT_MTVEC;
 119   load_reservation = -1;
 120 }
 121
 122 void processor_t::set_debug(bool value)
 123 {
 124   debug = value;
 125   if (ext)
 126     ext->set_debug(value);
 127 }
 128
 129 void processor_t::set_halted(bool value, halt_reason_t reason)
 130 {
 131   halted = value;
 132   halt_reason = reason;
 133 }
 134
 135 void processor_t::set_single_step(bool value)
 136 {
 137   single_step = value;
 138 }
 139
 140 void processor_t::set_histogram(bool value)
 141 {
 142   histogram_enabled = value;
 143 #ifndef RISCV_ENABLE_HISTOGRAM
 144   if (value) {
 145     fprintf(stderr, "PC Histogram support has not been properly enabled;");
 146     fprintf(stderr, " please re-build the riscv-isa-run project using \"configure --enable-histogram\".\n");
 147   }
 148 #endif
 149 }
 150
 151 void processor_t::reset(bool value)
 152 {
 153   if (run == !value)
 154     return;
 155   run = !value;
 156
 157   state.reset();
 158   set_csr(CSR_MSTATUS, state.mstatus);
 159
 160   if (ext)
 161     ext->reset(); // reset the extension
 162 }
 163
 164 void processor_t::raise_interrupt(reg_t which)
 165 {
 166   throw trap_t(((reg_t)1 << (max_xlen-1)) | which);
 167 }
 168
 169 static int ctz(reg_t val)
 170 {
 171   int res = 0;
 172   if (val)
 173     while ((val & 1) == 0)
 174       val >>= 1, res++;
 175   return res;
 176 }
 177
 178 void processor_t::take_interrupt()
 179 {
 180   reg_t pending_interrupts = state.mip & state.mie;
 181
 182   reg_t mie = get_field(state.mstatus, MSTATUS_MIE);
 183   reg_t m_enabled = state.prv < PRV_M || (state.prv == PRV_M && mie);
 184   reg_t enabled_interrupts = pending_interrupts & ~state.mideleg & -m_enabled;
 185
 186   reg_t sie = get_field(state.mstatus, MSTATUS_SIE);
 187   reg_t s_enabled = state.prv < PRV_S || (state.prv == PRV_S && sie);
 188   enabled_interrupts |= pending_interrupts & state.mideleg & -s_enabled;
 189
 190   if (enabled_interrupts)
 191     raise_interrupt(ctz(enabled_interrupts));
 192 }
 193
 194 static bool validate_priv(reg_t priv)
 195 {
 196   return priv == PRV_U || priv == PRV_S || priv == PRV_M;
 197 }
 198
 199 void processor_t::set_privilege(reg_t prv)
 200 {
 201   assert(validate_priv(prv));
 202   mmu->flush_tlb();
 203   state.prv = prv;
 204 }
 205
 206 void processor_t::take_trap(trap_t& t, reg_t epc)
 207 {
 208   if (debug)
 209     fprintf(stderr, "core %3d: exception %s, epc 0x%016" PRIx64 "\n",
 210             id, t.name(), epc);
 211
 212   if (t.cause() == CAUSE_BREAKPOINT &&
 213           sim->gdbserver && sim->gdbserver->connected()) {
 214     set_halted(true, HR_SWBP);
 215     return;
 216   }
 217
 218   // by default, trap to M-mode, unless delegated to S-mode
 219   reg_t bit = t.cause();
 220   reg_t deleg = state.medeleg;
 221   if (bit & ((reg_t)1 << (max_xlen-1)))
 222     deleg = state.mideleg, bit &= ~((reg_t)1 << (max_xlen-1));
 223   if (state.prv <= PRV_S && bit < max_xlen && ((deleg >> bit) & 1)) {
 224     // handle the trap in S-mode
 225     state.pc = state.stvec;
 226     state.scause = t.cause();
 227     state.sepc = epc;
 228     if (t.has_badaddr())
 229       state.sbadaddr = t.get_badaddr();
 230
 231     reg_t s = state.mstatus;
 232     s = set_field(s, MSTATUS_SPIE, get_field(s, MSTATUS_UIE << state.prv));
 233     s = set_field(s, MSTATUS_SPP, state.prv);
 234     s = set_field(s, MSTATUS_SIE, 0);
 235     set_csr(CSR_MSTATUS, s);
 236     set_privilege(PRV_S);
 237   } else {
 238     state.pc = state.mtvec;
 239     state.mcause = t.cause();
 240     state.mepc = epc;
 241     if (t.has_badaddr())
 242       state.mbadaddr = t.get_badaddr();
 243
 244     reg_t s = state.mstatus;
 245     s = set_field(s, MSTATUS_MPIE, get_field(s, MSTATUS_UIE << state.prv));
 246     s = set_field(s, MSTATUS_MPP, state.prv);
 247     s = set_field(s, MSTATUS_MIE, 0);
 248     set_csr(CSR_MSTATUS, s);
 249     set_privilege(PRV_M);
 250   }
 251
 252   yield_load_reservation();
 253 }
 254
 255 void processor_t::disasm(insn_t insn)
 256 {
 257   uint64_t bits = insn.bits() & ((1ULL << (8 * insn_length(insn.bits()))) - 1);
 258   fprintf(stderr, "core %3d: 0x%016" PRIx64 " (0x%08" PRIx64 ") %s\n",
 259           id, state.pc, bits, disassembler->disassemble(insn).c_str());
 260 }
 261
 262 static bool validate_vm(int max_xlen, reg_t vm)
 263 {
 264   if (max_xlen == 64 && (vm == VM_SV39 || vm == VM_SV48))
 265     return true;
 266   if (max_xlen == 32 && vm == VM_SV32)
 267     return true;
 268   return vm == VM_MBARE;
 269 }
 270
 271 void processor_t::set_csr(int which, reg_t val)
 272 {
 273   val = zext_xlen(val);
 274   reg_t delegable_ints = MIP_SSIP | MIP_STIP | MIP_SEIP | (1 << IRQ_COP);
 275   reg_t all_ints = delegable_ints | MIP_MSIP | MIP_MTIP;
 276   switch (which)
 277   {
 278     case CSR_FFLAGS:
 279       dirty_fp_state;
 280       state.fflags = val & (FSR_AEXC >> FSR_AEXC_SHIFT);
 281       break;
 282     case CSR_FRM:
 283       dirty_fp_state;
 284       state.frm = val & (FSR_RD >> FSR_RD_SHIFT);
 285       break;
 286     case CSR_FCSR:
 287       dirty_fp_state;
 288       state.fflags = (val & FSR_AEXC) >> FSR_AEXC_SHIFT;
 289       state.frm = (val & FSR_RD) >> FSR_RD_SHIFT;
 290       break;
 291     case CSR_MSTATUS: {
 292       if ((val ^ state.mstatus) &
 293           (MSTATUS_VM | MSTATUS_MPP | MSTATUS_MPRV | MSTATUS_PUM))
 294         mmu->flush_tlb();
 295
 296       reg_t mask = MSTATUS_SIE | MSTATUS_SPIE | MSTATUS_MIE | MSTATUS_MPIE
 297                  | MSTATUS_SPP | MSTATUS_FS | MSTATUS_MPRV | MSTATUS_PUM
 298                  | (ext ? MSTATUS_XS : 0);
 299
 300       if (validate_vm(max_xlen, get_field(val, MSTATUS_VM)))
 301         mask |= MSTATUS_VM;
 302       if (validate_priv(get_field(val, MSTATUS_MPP)))
 303         mask |= MSTATUS_MPP;
 304
 305       state.mstatus = (state.mstatus & ~mask) | (val & mask);
 306
 307       bool dirty = (state.mstatus & MSTATUS_FS) == MSTATUS_FS;
 308       dirty |= (state.mstatus & MSTATUS_XS) == MSTATUS_XS;
 309       if (max_xlen == 32)
 310         state.mstatus = set_field(state.mstatus, MSTATUS32_SD, dirty);
 311       else
 312         state.mstatus = set_field(state.mstatus, MSTATUS64_SD, dirty);
 313
 314       // spike supports the notion of xlen < max_xlen, but current priv spec
 315       // doesn't provide a mechanism to run RV32 software on an RV64 machine
 316       xlen = max_xlen;
 317       break;
 318     }
 319     case CSR_MIP: {
 320       reg_t mask = MIP_SSIP | MIP_STIP;
 321       state.mip = (state.mip & ~mask) | (val & mask);
 322       break;
 323     }
 324     case CSR_MIE:
 325       state.mie = (state.mie & ~all_ints) | (val & all_ints);
 326       break;
 327     case CSR_MIDELEG:
 328       state.mideleg = (state.mideleg & ~delegable_ints) | (val & delegable_ints);
 329       break;
 330     case CSR_MEDELEG: {
 331       reg_t mask = 0;
 332 #define DECLARE_CAUSE(name, value) mask |= 1ULL << (value);
 333 #include "encoding.h"
 334 #undef DECLARE_CAUSE
 335       state.medeleg = (state.medeleg & ~mask) | (val & mask);
 336       break;
 337     }
 338     case CSR_MUCOUNTEREN:
 339       state.mucounteren = val & 7;
 340       break;
 341     case CSR_MSCOUNTEREN:
 342       state.mscounteren = val & 7;
 343       break;
 344     case CSR_SSTATUS: {
 345       reg_t mask = SSTATUS_SIE | SSTATUS_SPIE | SSTATUS_SPP | SSTATUS_FS
 346                  | SSTATUS_XS | SSTATUS_PUM;
 347       return set_csr(CSR_MSTATUS, (state.mstatus & ~mask) | (val & mask));
 348     }
 349     case CSR_SIP:
 350       return set_csr(CSR_MIP,
 351                      (state.mip & ~state.mideleg) | (val & state.mideleg));
 352     case CSR_SIE:
 353       return set_csr(CSR_MIE,
 354                      (state.mie & ~state.mideleg) | (val & state.mideleg));
 355     case CSR_SEPC: state.sepc = val; break;
 356     case CSR_STVEC: state.stvec = val >> 2 << 2; break;
 357     case CSR_SPTBR: state.sptbr = val; break;
 358     case CSR_SSCRATCH: state.sscratch = val; break;
 359     case CSR_SCAUSE: state.scause = val; break;
 360     case CSR_SBADADDR: state.sbadaddr = val; break;
 361     case CSR_MEPC: state.mepc = val; break;
 362     case CSR_MTVEC: state.mtvec = val >> 2 << 2; break;
 363     case CSR_MSCRATCH: state.mscratch = val; break;
 364     case CSR_MCAUSE: state.mcause = val; break;
 365     case CSR_MBADADDR: state.mbadaddr = val; break;
 366     case DCSR_ADDRESS:
 367       state.dcsr.prv = (val & DCSR_PRV_MASK) >> DCSR_PRV_OFFSET;
 368       state.dcsr.step = (val & DCSR_STEP_MASK) >> DCSR_STEP_OFFSET;
 369       // TODO: ndreset and fullreset
 370       state.dcsr.ebreakm = (val & DCSR_EBREAKM_MASK) >> DCSR_EBREAKM_OFFSET;
 371       state.dcsr.ebreakh = (val & DCSR_EBREAKH_MASK) >> DCSR_EBREAKH_OFFSET;
 372       state.dcsr.ebreaks = (val & DCSR_EBREAKS_MASK) >> DCSR_EBREAKS_OFFSET;
 373       state.dcsr.ebreaku = (val & DCSR_EBREAKU_MASK) >> DCSR_EBREAKU_OFFSET;
 374       state.dcsr.halt = (val & DCSR_HALT_MASK) >> DCSR_HALT_OFFSET;
 375       break;
 376     case DPC_ADDRESS:
 377       state.dpc = val;
 378       break;
 379     case DSCRATCH_ADDRESS:
 380       state.dscratch = val;
 381       break;
 382   }
 383 }
 384
 385 reg_t processor_t::get_csr(int which)
 386 {
 387   switch (which)
 388   {
 389     case CSR_FFLAGS:
 390       require_fp;
 391       if (!supports_extension('F'))
 392         break;
 393       return state.fflags;
 394     case CSR_FRM:
 395       require_fp;
 396       if (!supports_extension('F'))
 397         break;
 398       return state.frm;
 399     case CSR_FCSR:
 400       require_fp;
 401       if (!supports_extension('F'))
 402         break;
 403       return (state.fflags << FSR_AEXC_SHIFT) | (state.frm << FSR_RD_SHIFT);
 404     case CSR_TIME:
 405     case CSR_INSTRET:
 406     case CSR_CYCLE:
 407       if ((state.mucounteren >> (which & (xlen-1))) & 1)
 408         return get_csr(which + (CSR_MCYCLE - CSR_CYCLE));
 409       break;
 410     case CSR_STIME:
 411     case CSR_SINSTRET:
 412     case CSR_SCYCLE:
 413       if ((state.mscounteren >> (which & (xlen-1))) & 1)
 414         return get_csr(which + (CSR_MCYCLE - CSR_SCYCLE));
 415       break;
 416     case CSR_MUCOUNTEREN: return state.mucounteren;
 417     case CSR_MSCOUNTEREN: return state.mscounteren;
 418     case CSR_MUCYCLE_DELTA: return 0;
 419     case CSR_MUTIME_DELTA: return 0;
 420     case CSR_MUINSTRET_DELTA: return 0;
 421     case CSR_MSCYCLE_DELTA: return 0;
 422     case CSR_MSTIME_DELTA: return 0;
 423     case CSR_MSINSTRET_DELTA: return 0;
 424     case CSR_MUCYCLE_DELTAH: if (xlen > 32) break; else return 0;
 425     case CSR_MUTIME_DELTAH: if (xlen > 32) break; else return 0;
 426     case CSR_MUINSTRET_DELTAH: if (xlen > 32) break; else return 0;
 427     case CSR_MSCYCLE_DELTAH: if (xlen > 32) break; else return 0;
 428     case CSR_MSTIME_DELTAH: if (xlen > 32) break; else return 0;
 429     case CSR_MSINSTRET_DELTAH: if (xlen > 32) break; else return 0;
 430     case CSR_MCYCLE: return state.minstret;
 431     case CSR_MINSTRET: return state.minstret;
 432     case CSR_MCYCLEH: if (xlen > 32) break; else return state.minstret >> 32;
 433     case CSR_MINSTRETH: if (xlen > 32) break; else return state.minstret >> 32;
 434     case CSR_SSTATUS: {
 435       reg_t mask = SSTATUS_SIE | SSTATUS_SPIE | SSTATUS_SPP | SSTATUS_FS
 436                  | SSTATUS_XS | SSTATUS_PUM;
 437       reg_t sstatus = state.mstatus & mask;
 438       if ((sstatus & SSTATUS_FS) == SSTATUS_FS ||
 439           (sstatus & SSTATUS_XS) == SSTATUS_XS)
 440         sstatus |= (xlen == 32 ? SSTATUS32_SD : SSTATUS64_SD);
 441       return sstatus;
 442     }
 443     case CSR_SIP: return state.mip & state.mideleg;
 444     case CSR_SIE: return state.mie & state.mideleg;
 445     case CSR_SEPC: return state.sepc;
 446     case CSR_SBADADDR: return state.sbadaddr;
 447     case CSR_STVEC: return state.stvec;
 448     case CSR_SCAUSE:
 449       if (max_xlen > xlen)
 450         return state.scause | ((state.scause >> (max_xlen-1)) << (xlen-1));
 451       return state.scause;
 452     case CSR_SPTBR: return state.sptbr;
 453     case CSR_SASID: return 0;
 454     case CSR_SSCRATCH: return state.sscratch;
 455     case CSR_MSTATUS: return state.mstatus;
 456     case CSR_MIP: return state.mip;
 457     case CSR_MIE: return state.mie;
 458     case CSR_MEPC: return state.mepc;
 459     case CSR_MSCRATCH: return state.mscratch;
 460     case CSR_MCAUSE: return state.mcause;
 461     case CSR_MBADADDR: return state.mbadaddr;
 462     case CSR_MISA: return isa;
 463     case CSR_MARCHID: return 0;
 464     case CSR_MIMPID: return 0;
 465     case CSR_MVENDORID: return 0;
 466     case CSR_MHARTID: return id;
 467     case CSR_MTVEC: return state.mtvec;
 468     case CSR_MEDELEG: return state.medeleg;
 469     case CSR_MIDELEG: return state.mideleg;
 470     case DCSR_ADDRESS:
 471       return
 472           (1 << DCSR_XDEBUGVER_OFFSET) |
 473           (0 << DCSR_HWBPCOUNT_OFFSET) |
 474           (0 << DCSR_NDRESET_OFFSET) |
 475           (0 << DCSR_FULLRESET_OFFSET) |
 476           (state.dcsr.prv << DCSR_PRV_OFFSET) |
 477           (state.dcsr.step << DCSR_STEP_OFFSET) |
 478           (state.dcsr.debugint << DCSR_DEBUGINT_OFFSET) |
 479           (0 << DCSR_STOPCYCLE_OFFSET) |
 480           (0 << DCSR_STOPTIME_OFFSET) |
 481           (state.dcsr.ebreakm << DCSR_EBREAKM_OFFSET) |
 482           (state.dcsr.ebreakh << DCSR_EBREAKH_OFFSET) |
 483           (state.dcsr.ebreaks << DCSR_EBREAKS_OFFSET) |
 484           (state.dcsr.ebreaku << DCSR_EBREAKU_OFFSET) |
 485           (state.dcsr.halt << DCSR_HALT_OFFSET) |
 486           (state.dcsr.cause << DCSR_CAUSE_OFFSET);
 487     case DPC_ADDRESS:
 488       return state.dpc;
 489     case DSCRATCH_ADDRESS:
 490       return state.dscratch;
 491   }
 492   throw trap_illegal_instruction();
 493 }
 494
 495 reg_t illegal_instruction(processor_t* p, insn_t insn, reg_t pc)
 496 {
 497   throw trap_illegal_instruction();
 498 }
 499
 500 insn_func_t processor_t::decode_insn(insn_t insn)
 501 {
 502   // look up opcode in hash table
 503   size_t idx = insn.bits() % OPCODE_CACHE_SIZE;
 504   insn_desc_t desc = opcode_cache[idx];
 505
 506   if (unlikely(insn.bits() != desc.match)) {
 507     // fall back to linear search
 508     insn_desc_t* p = &instructions[0];
 509     while ((insn.bits() & p->mask) != p->match)
 510       p++;
 511     desc = *p;
 512
 513     if (p->mask != 0 && p > &instructions[0]) {
 514       if (p->match != (p-1)->match && p->match != (p+1)->match) {
 515         // move to front of opcode list to reduce miss penalty
 516         while (--p >= &instructions[0])
 517           *(p+1) = *p;
 518         instructions[0] = desc;
 519       }
 520     }
 521
 522     opcode_cache[idx] = desc;
 523     opcode_cache[idx].match = insn.bits();
 524   }
 525
 526   return xlen == 64 ? desc.rv64 : desc.rv32;
 527 }
 528
 529 void processor_t::register_insn(insn_desc_t desc)
 530 {
 531   instructions.push_back(desc);
 532 }
 533
 534 void processor_t::build_opcode_map()
 535 {
 536   struct cmp {
 537     bool operator()(const insn_desc_t& lhs, const insn_desc_t& rhs) {
 538       if (lhs.match == rhs.match)
 539         return lhs.mask > rhs.mask;
 540       return lhs.match > rhs.match;
 541     }
 542   };
 543   std::sort(instructions.begin(), instructions.end(), cmp());
 544
 545   for (size_t i = 0; i < OPCODE_CACHE_SIZE; i++)
 546     opcode_cache[i] = {1, 0, &illegal_instruction, &illegal_instruction};
 547 }
 548
 549 void processor_t::register_extension(extension_t* x)
 550 {
 551   for (auto insn : x->get_instructions())
 552     register_insn(insn);
 553   build_opcode_map();
 554   for (auto disasm_insn : x->get_disasms())
 555     disassembler->add_insn(disasm_insn);
 556   if (ext != NULL)
 557     throw std::logic_error("only one extension may be registered");
 558   ext = x;
 559   x->set_processor(this);
 560 }
 561
 562 void processor_t::register_base_instructions()
 563 {
 564   #define DECLARE_INSN(name, match, mask) \
 565     insn_bits_t name##_match = (match), name##_mask = (mask);
 566   #include "encoding.h"
 567   #undef DECLARE_INSN
 568
 569   #define DEFINE_INSN(name) \
 570     REGISTER_INSN(this, name, name##_match, name##_mask)
 571   #include "insn_list.h"
 572   #undef DEFINE_INSN
 573
 574   register_insn({0, 0, &illegal_instruction, &illegal_instruction});
 575   build_opcode_map();
 576 }
 577
 578 bool processor_t::load(reg_t addr, size_t len, uint8_t* bytes)
 579 {
 580   return false;
 581 }
 582
 583 bool processor_t::store(reg_t addr, size_t len, const uint8_t* bytes)
 584 {
 585   switch (addr)
 586   {
 587     case 0:
 588       state.mip &= ~MIP_MSIP;
 589       if (bytes[0] & 1)
 590         state.mip |= MIP_MSIP;
 591       return true;
 592
 593     default:
 594       return false;
 595   }
 596 }