lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

   1 //===-- X86AsmBackend.cpp - X86 Assembler Backend -------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "MCTargetDesc/X86BaseInfo.h"
  10 #include "MCTargetDesc/X86FixupKinds.h"
  11 #include "llvm/ADT/StringSwitch.h"
  12 #include "llvm/BinaryFormat/ELF.h"
  13 #include "llvm/BinaryFormat/MachO.h"
  14 #include "llvm/MC/MCAsmBackend.h"
  15 #include "llvm/MC/MCDwarf.h"
  16 #include "llvm/MC/MCELFObjectWriter.h"
  17 #include "llvm/MC/MCExpr.h"
  18 #include "llvm/MC/MCFixupKindInfo.h"
  19 #include "llvm/MC/MCInst.h"
  20 #include "llvm/MC/MCMachObjectWriter.h"
  21 #include "llvm/MC/MCObjectWriter.h"
  22 #include "llvm/MC/MCRegisterInfo.h"
  23 #include "llvm/MC/MCSectionMachO.h"
  24 #include "llvm/MC/MCSubtargetInfo.h"
  25 #include "llvm/Support/ErrorHandling.h"
  26 #include "llvm/Support/raw_ostream.h"
  27 using namespace llvm;
  28
  29 static unsigned getFixupKindSize(unsigned Kind) {
  30   switch (Kind) {
  31   default:
  32     llvm_unreachable("invalid fixup kind!");
  33   case FK_NONE:
  34     return 0;
  35   case FK_PCRel_1:
  36   case FK_SecRel_1:
  37   case FK_Data_1:
  38     return 1;
  39   case FK_PCRel_2:
  40   case FK_SecRel_2:
  41   case FK_Data_2:
  42     return 2;
  43   case FK_PCRel_4:
  44   case X86::reloc_riprel_4byte:
  45   case X86::reloc_riprel_4byte_relax:
  46   case X86::reloc_riprel_4byte_relax_rex:
  47   case X86::reloc_riprel_4byte_movq_load:
  48   case X86::reloc_signed_4byte:
  49   case X86::reloc_signed_4byte_relax:
  50   case X86::reloc_global_offset_table:
  51   case X86::reloc_branch_4byte_pcrel:
  52   case FK_SecRel_4:
  53   case FK_Data_4:
  54     return 4;
  55   case FK_PCRel_8:
  56   case FK_SecRel_8:
  57   case FK_Data_8:
  58   case X86::reloc_global_offset_table8:
  59     return 8;
  60   }
  61 }
  62
  63 namespace {
  64
  65 class X86ELFObjectWriter : public MCELFObjectTargetWriter {
  66 public:
  67   X86ELFObjectWriter(bool is64Bit, uint8_t OSABI, uint16_t EMachine,
  68                      bool HasRelocationAddend, bool foobar)
  69     : MCELFObjectTargetWriter(is64Bit, OSABI, EMachine, HasRelocationAddend) {}
  70 };
  71
  72 class X86AsmBackend : public MCAsmBackend {
  73   const MCSubtargetInfo &STI;
  74 public:
  75   X86AsmBackend(const Target &T, const MCSubtargetInfo &STI)
  76       : MCAsmBackend(support::little), STI(STI) {}
  77
  78   unsigned getNumFixupKinds() const override {
  79     return X86::NumTargetFixupKinds;
  80   }
  81
  82   Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
  83
  84   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
  85     const static MCFixupKindInfo Infos[X86::NumTargetFixupKinds] = {
  86         {"reloc_riprel_4byte", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
  87         {"reloc_riprel_4byte_movq_load", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
  88         {"reloc_riprel_4byte_relax", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
  89         {"reloc_riprel_4byte_relax_rex", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
  90         {"reloc_signed_4byte", 0, 32, 0},
  91         {"reloc_signed_4byte_relax", 0, 32, 0},
  92         {"reloc_global_offset_table", 0, 32, 0},
  93         {"reloc_global_offset_table8", 0, 64, 0},
  94         {"reloc_branch_4byte_pcrel", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
  95     };
  96
  97     if (Kind < FirstTargetFixupKind)
  98       return MCAsmBackend::getFixupKindInfo(Kind);
  99
 100     assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
 101            "Invalid kind!");
 102     assert(Infos[Kind - FirstTargetFixupKind].Name && "Empty fixup name!");
 103     return Infos[Kind - FirstTargetFixupKind];
 104   }
 105
 106   bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
 107                              const MCValue &Target) override;
 108
 109   void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
 110                   const MCValue &Target, MutableArrayRef<char> Data,
 111                   uint64_t Value, bool IsResolved,
 112                   const MCSubtargetInfo *STI) const override {
 113     unsigned Size = getFixupKindSize(Fixup.getKind());
 114
 115     assert(Fixup.getOffset() + Size <= Data.size() && "Invalid fixup offset!");
 116
 117     // Check that uppper bits are either all zeros or all ones.
 118     // Specifically ignore overflow/underflow as long as the leakage is
 119     // limited to the lower bits. This is to remain compatible with
 120     // other assemblers.
 121     assert((Size == 0 || isIntN(Size * 8 + 1, Value)) &&
 122            "Value does not fit in the Fixup field");
 123
 124     for (unsigned i = 0; i != Size; ++i)
 125       Data[Fixup.getOffset() + i] = uint8_t(Value >> (i * 8));
 126   }
 127
 128   bool mayNeedRelaxation(const MCInst &Inst,
 129                          const MCSubtargetInfo &STI) const override;
 130
 131   bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
 132                             const MCRelaxableFragment *DF,
 133                             const MCAsmLayout &Layout) const override;
 134
 135   void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
 136                         MCInst &Res) const override;
 137
 138   bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
 139 };
 140 } // end anonymous namespace
 141
 142 static unsigned getRelaxedOpcodeBranch(const MCInst &Inst, bool is16BitMode) {
 143   unsigned Op = Inst.getOpcode();
 144   switch (Op) {
 145   default:
 146     return Op;
 147   case X86::JCC_1:
 148     return (is16BitMode) ? X86::JCC_2 : X86::JCC_4;
 149   case X86::JMP_1:
 150     return (is16BitMode) ? X86::JMP_2 : X86::JMP_4;
 151   }
 152 }
 153
 154 static unsigned getRelaxedOpcodeArith(const MCInst &Inst) {
 155   unsigned Op = Inst.getOpcode();
 156   switch (Op) {
 157   default:
 158     return Op;
 159
 160     // IMUL
 161   case X86::IMUL16rri8: return X86::IMUL16rri;
 162   case X86::IMUL16rmi8: return X86::IMUL16rmi;
 163   case X86::IMUL32rri8: return X86::IMUL32rri;
 164   case X86::IMUL32rmi8: return X86::IMUL32rmi;
 165   case X86::IMUL64rri8: return X86::IMUL64rri32;
 166   case X86::IMUL64rmi8: return X86::IMUL64rmi32;
 167
 168     // AND
 169   case X86::AND16ri8: return X86::AND16ri;
 170   case X86::AND16mi8: return X86::AND16mi;
 171   case X86::AND32ri8: return X86::AND32ri;
 172   case X86::AND32mi8: return X86::AND32mi;
 173   case X86::AND64ri8: return X86::AND64ri32;
 174   case X86::AND64mi8: return X86::AND64mi32;
 175
 176     // OR
 177   case X86::OR16ri8: return X86::OR16ri;
 178   case X86::OR16mi8: return X86::OR16mi;
 179   case X86::OR32ri8: return X86::OR32ri;
 180   case X86::OR32mi8: return X86::OR32mi;
 181   case X86::OR64ri8: return X86::OR64ri32;
 182   case X86::OR64mi8: return X86::OR64mi32;
 183
 184     // XOR
 185   case X86::XOR16ri8: return X86::XOR16ri;
 186   case X86::XOR16mi8: return X86::XOR16mi;
 187   case X86::XOR32ri8: return X86::XOR32ri;
 188   case X86::XOR32mi8: return X86::XOR32mi;
 189   case X86::XOR64ri8: return X86::XOR64ri32;
 190   case X86::XOR64mi8: return X86::XOR64mi32;
 191
 192     // ADD
 193   case X86::ADD16ri8: return X86::ADD16ri;
 194   case X86::ADD16mi8: return X86::ADD16mi;
 195   case X86::ADD32ri8: return X86::ADD32ri;
 196   case X86::ADD32mi8: return X86::ADD32mi;
 197   case X86::ADD64ri8: return X86::ADD64ri32;
 198   case X86::ADD64mi8: return X86::ADD64mi32;
 199
 200    // ADC
 201   case X86::ADC16ri8: return X86::ADC16ri;
 202   case X86::ADC16mi8: return X86::ADC16mi;
 203   case X86::ADC32ri8: return X86::ADC32ri;
 204   case X86::ADC32mi8: return X86::ADC32mi;
 205   case X86::ADC64ri8: return X86::ADC64ri32;
 206   case X86::ADC64mi8: return X86::ADC64mi32;
 207
 208     // SUB
 209   case X86::SUB16ri8: return X86::SUB16ri;
 210   case X86::SUB16mi8: return X86::SUB16mi;
 211   case X86::SUB32ri8: return X86::SUB32ri;
 212   case X86::SUB32mi8: return X86::SUB32mi;
 213   case X86::SUB64ri8: return X86::SUB64ri32;
 214   case X86::SUB64mi8: return X86::SUB64mi32;
 215
 216    // SBB
 217   case X86::SBB16ri8: return X86::SBB16ri;
 218   case X86::SBB16mi8: return X86::SBB16mi;
 219   case X86::SBB32ri8: return X86::SBB32ri;
 220   case X86::SBB32mi8: return X86::SBB32mi;
 221   case X86::SBB64ri8: return X86::SBB64ri32;
 222   case X86::SBB64mi8: return X86::SBB64mi32;
 223
 224     // CMP
 225   case X86::CMP16ri8: return X86::CMP16ri;
 226   case X86::CMP16mi8: return X86::CMP16mi;
 227   case X86::CMP32ri8: return X86::CMP32ri;
 228   case X86::CMP32mi8: return X86::CMP32mi;
 229   case X86::CMP64ri8: return X86::CMP64ri32;
 230   case X86::CMP64mi8: return X86::CMP64mi32;
 231
 232     // PUSH
 233   case X86::PUSH32i8:  return X86::PUSHi32;
 234   case X86::PUSH16i8:  return X86::PUSHi16;
 235   case X86::PUSH64i8:  return X86::PUSH64i32;
 236   }
 237 }
 238
 239 static unsigned getRelaxedOpcode(const MCInst &Inst, bool is16BitMode) {
 240   unsigned R = getRelaxedOpcodeArith(Inst);
 241   if (R != Inst.getOpcode())
 242     return R;
 243   return getRelaxedOpcodeBranch(Inst, is16BitMode);
 244 }
 245
 246 Optional<MCFixupKind> X86AsmBackend::getFixupKind(StringRef Name) const {
 247   if (STI.getTargetTriple().isOSBinFormatELF()) {
 248     if (STI.getTargetTriple().getArch() == Triple::x86_64) {
 249       if (Name == "R_X86_64_NONE")
 250         return FK_NONE;
 251     } else {
 252       if (Name == "R_386_NONE")
 253         return FK_NONE;
 254     }
 255   }
 256   return MCAsmBackend::getFixupKind(Name);
 257 }
 258
 259 bool X86AsmBackend::shouldForceRelocation(const MCAssembler &,
 260                                           const MCFixup &Fixup,
 261                                           const MCValue &) {
 262   return Fixup.getKind() == FK_NONE;
 263 }
 264
 265 bool X86AsmBackend::mayNeedRelaxation(const MCInst &Inst,
 266                                       const MCSubtargetInfo &STI) const {
 267   // Branches can always be relaxed in either mode.
 268   if (getRelaxedOpcodeBranch(Inst, false) != Inst.getOpcode())
 269     return true;
 270
 271   // Check if this instruction is ever relaxable.
 272   if (getRelaxedOpcodeArith(Inst) == Inst.getOpcode())
 273     return false;
 274
 275
 276   // Check if the relaxable operand has an expression. For the current set of
 277   // relaxable instructions, the relaxable operand is always the last operand.
 278   unsigned RelaxableOp = Inst.getNumOperands() - 1;
 279   if (Inst.getOperand(RelaxableOp).isExpr())
 280     return true;
 281
 282   return false;
 283 }
 284
 285 bool X86AsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
 286                                          uint64_t Value,
 287                                          const MCRelaxableFragment *DF,
 288                                          const MCAsmLayout &Layout) const {
 289   // Relax if the value is too big for a (signed) i8.
 290   return !isInt<8>(Value);
 291 }
 292
 293 // FIXME: Can tblgen help at all here to verify there aren't other instructions
 294 // we can relax?
 295 void X86AsmBackend::relaxInstruction(const MCInst &Inst,
 296                                      const MCSubtargetInfo &STI,
 297                                      MCInst &Res) const {
 298   // The only relaxations X86 does is from a 1byte pcrel to a 4byte pcrel.
 299   bool is16BitMode = STI.getFeatureBits()[X86::Mode16Bit];
 300   unsigned RelaxedOp = getRelaxedOpcode(Inst, is16BitMode);
 301
 302   if (RelaxedOp == Inst.getOpcode()) {
 303     SmallString<256> Tmp;
 304     raw_svector_ostream OS(Tmp);
 305     Inst.dump_pretty(OS);
 306     OS << "\n";
 307     report_fatal_error("unexpected instruction to relax: " + OS.str());
 308   }
 309
 310   Res = Inst;
 311   Res.setOpcode(RelaxedOp);
 312 }
 313
 314 /// Write a sequence of optimal nops to the output, covering \p Count
 315 /// bytes.
 316 /// \return - true on success, false on failure
 317 bool X86AsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
 318   static const char Nops[10][11] = {
 319     // nop
 320     "\x90",
 321     // xchg %ax,%ax
 322     "\x66\x90",
 323     // nopl (%[re]ax)
 324     "\x0f\x1f\x00",
 325     // nopl 0(%[re]ax)
 326     "\x0f\x1f\x40\x00",
 327     // nopl 0(%[re]ax,%[re]ax,1)
 328     "\x0f\x1f\x44\x00\x00",
 329     // nopw 0(%[re]ax,%[re]ax,1)
 330     "\x66\x0f\x1f\x44\x00\x00",
 331     // nopl 0L(%[re]ax)
 332     "\x0f\x1f\x80\x00\x00\x00\x00",
 333     // nopl 0L(%[re]ax,%[re]ax,1)
 334     "\x0f\x1f\x84\x00\x00\x00\x00\x00",
 335     // nopw 0L(%[re]ax,%[re]ax,1)
 336     "\x66\x0f\x1f\x84\x00\x00\x00\x00\x00",
 337     // nopw %cs:0L(%[re]ax,%[re]ax,1)
 338     "\x66\x2e\x0f\x1f\x84\x00\x00\x00\x00\x00",
 339   };
 340
 341   // This CPU doesn't support long nops. If needed add more.
 342   // FIXME: We could generated something better than plain 0x90.
 343   if (!STI.getFeatureBits()[X86::FeatureNOPL]) {
 344     for (uint64_t i = 0; i < Count; ++i)
 345       OS << '\x90';
 346     return true;
 347   }
 348
 349   // 15-bytes is the longest single NOP instruction, but 10-bytes is
 350   // commonly the longest that can be efficiently decoded.
 351   uint64_t MaxNopLength = 10;
 352   if (STI.getFeatureBits()[X86::ProcIntelSLM])
 353     MaxNopLength = 7;
 354   else if (STI.getFeatureBits()[X86::FeatureFast15ByteNOP])
 355     MaxNopLength = 15;
 356   else if (STI.getFeatureBits()[X86::FeatureFast11ByteNOP])
 357     MaxNopLength = 11;
 358
 359   // Emit as many MaxNopLength NOPs as needed, then emit a NOP of the remaining
 360   // length.
 361   do {
 362     const uint8_t ThisNopLength = (uint8_t) std::min(Count, MaxNopLength);
 363     const uint8_t Prefixes = ThisNopLength <= 10 ? 0 : ThisNopLength - 10;
 364     for (uint8_t i = 0; i < Prefixes; i++)
 365       OS << '\x66';
 366     const uint8_t Rest = ThisNopLength - Prefixes;
 367     if (Rest != 0)
 368       OS.write(Nops[Rest - 1], Rest);
 369     Count -= ThisNopLength;
 370   } while (Count != 0);
 371
 372   return true;
 373 }
 374
 375 /* *** */
 376
 377 namespace {
 378
 379 class ELFX86AsmBackend : public X86AsmBackend {
 380 public:
 381   uint8_t OSABI;
 382   ELFX86AsmBackend(const Target &T, uint8_t OSABI, const MCSubtargetInfo &STI)
 383       : X86AsmBackend(T, STI), OSABI(OSABI) {}
 384 };
 385
 386 class ELFX86_32AsmBackend : public ELFX86AsmBackend {
 387 public:
 388   ELFX86_32AsmBackend(const Target &T, uint8_t OSABI,
 389                       const MCSubtargetInfo &STI)
 390     : ELFX86AsmBackend(T, OSABI, STI) {}
 391
 392   std::unique_ptr<MCObjectTargetWriter>
 393   createObjectTargetWriter() const override {
 394     return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI, ELF::EM_386);
 395   }
 396 };
 397
 398 class ELFX86_X32AsmBackend : public ELFX86AsmBackend {
 399 public:
 400   ELFX86_X32AsmBackend(const Target &T, uint8_t OSABI,
 401                        const MCSubtargetInfo &STI)
 402       : ELFX86AsmBackend(T, OSABI, STI) {}
 403
 404   std::unique_ptr<MCObjectTargetWriter>
 405   createObjectTargetWriter() const override {
 406     return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI,
 407                                     ELF::EM_X86_64);
 408   }
 409 };
 410
 411 class ELFX86_IAMCUAsmBackend : public ELFX86AsmBackend {
 412 public:
 413   ELFX86_IAMCUAsmBackend(const Target &T, uint8_t OSABI,
 414                          const MCSubtargetInfo &STI)
 415       : ELFX86AsmBackend(T, OSABI, STI) {}
 416
 417   std::unique_ptr<MCObjectTargetWriter>
 418   createObjectTargetWriter() const override {
 419     return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI,
 420                                     ELF::EM_IAMCU);
 421   }
 422 };
 423
 424 class ELFX86_64AsmBackend : public ELFX86AsmBackend {
 425 public:
 426   ELFX86_64AsmBackend(const Target &T, uint8_t OSABI,
 427                       const MCSubtargetInfo &STI)
 428     : ELFX86AsmBackend(T, OSABI, STI) {}
 429
 430   std::unique_ptr<MCObjectTargetWriter>
 431   createObjectTargetWriter() const override {
 432     return createX86ELFObjectWriter(/*IsELF64*/ true, OSABI, ELF::EM_X86_64);
 433   }
 434 };
 435
 436 class WindowsX86AsmBackend : public X86AsmBackend {
 437   bool Is64Bit;
 438
 439 public:
 440   WindowsX86AsmBackend(const Target &T, bool is64Bit,
 441                        const MCSubtargetInfo &STI)
 442     : X86AsmBackend(T, STI)
 443     , Is64Bit(is64Bit) {
 444   }
 445
 446   Optional<MCFixupKind> getFixupKind(StringRef Name) const override {
 447     return StringSwitch<Optional<MCFixupKind>>(Name)
 448         .Case("dir32", FK_Data_4)
 449         .Case("secrel32", FK_SecRel_4)
 450         .Case("secidx", FK_SecRel_2)
 451         .Default(MCAsmBackend::getFixupKind(Name));
 452   }
 453
 454   std::unique_ptr<MCObjectTargetWriter>
 455   createObjectTargetWriter() const override {
 456     return createX86WinCOFFObjectWriter(Is64Bit);
 457   }
 458 };
 459
 460 namespace CU {
 461
 462   /// Compact unwind encoding values.
 463   enum CompactUnwindEncodings {
 464     /// [RE]BP based frame where [RE]BP is pused on the stack immediately after
 465     /// the return address, then [RE]SP is moved to [RE]BP.
 466     UNWIND_MODE_BP_FRAME                   = 0x01000000,
 467
 468     /// A frameless function with a small constant stack size.
 469     UNWIND_MODE_STACK_IMMD                 = 0x02000000,
 470
 471     /// A frameless function with a large constant stack size.
 472     UNWIND_MODE_STACK_IND                  = 0x03000000,
 473
 474     /// No compact unwind encoding is available.
 475     UNWIND_MODE_DWARF                      = 0x04000000,
 476
 477     /// Mask for encoding the frame registers.
 478     UNWIND_BP_FRAME_REGISTERS              = 0x00007FFF,
 479
 480     /// Mask for encoding the frameless registers.
 481     UNWIND_FRAMELESS_STACK_REG_PERMUTATION = 0x000003FF
 482   };
 483
 484 } // end CU namespace
 485
 486 class DarwinX86AsmBackend : public X86AsmBackend {
 487   const MCRegisterInfo &MRI;
 488
 489   /// Number of registers that can be saved in a compact unwind encoding.
 490   enum { CU_NUM_SAVED_REGS = 6 };
 491
 492   mutable unsigned SavedRegs[CU_NUM_SAVED_REGS];
 493   bool Is64Bit;
 494
 495   unsigned OffsetSize;                   ///< Offset of a "push" instruction.
 496   unsigned MoveInstrSize;                ///< Size of a "move" instruction.
 497   unsigned StackDivide;                  ///< Amount to adjust stack size by.
 498 protected:
 499   /// Size of a "push" instruction for the given register.
 500   unsigned PushInstrSize(unsigned Reg) const {
 501     switch (Reg) {
 502       case X86::EBX:
 503       case X86::ECX:
 504       case X86::EDX:
 505       case X86::EDI:
 506       case X86::ESI:
 507       case X86::EBP:
 508       case X86::RBX:
 509       case X86::RBP:
 510         return 1;
 511       case X86::R12:
 512       case X86::R13:
 513       case X86::R14:
 514       case X86::R15:
 515         return 2;
 516     }
 517     return 1;
 518   }
 519
 520   /// Implementation of algorithm to generate the compact unwind encoding
 521   /// for the CFI instructions.
 522   uint32_t
 523   generateCompactUnwindEncodingImpl(ArrayRef<MCCFIInstruction> Instrs) const {
 524     if (Instrs.empty()) return 0;
 525
 526     // Reset the saved registers.
 527     unsigned SavedRegIdx = 0;
 528     memset(SavedRegs, 0, sizeof(SavedRegs));
 529
 530     bool HasFP = false;
 531
 532     // Encode that we are using EBP/RBP as the frame pointer.
 533     uint32_t CompactUnwindEncoding = 0;
 534
 535     unsigned SubtractInstrIdx = Is64Bit ? 3 : 2;
 536     unsigned InstrOffset = 0;
 537     unsigned StackAdjust = 0;
 538     unsigned StackSize = 0;
 539     unsigned NumDefCFAOffsets = 0;
 540
 541     for (unsigned i = 0, e = Instrs.size(); i != e; ++i) {
 542       const MCCFIInstruction &Inst = Instrs[i];
 543
 544       switch (Inst.getOperation()) {
 545       default:
 546         // Any other CFI directives indicate a frame that we aren't prepared
 547         // to represent via compact unwind, so just bail out.
 548         return 0;
 549       case MCCFIInstruction::OpDefCfaRegister: {
 550         // Defines a frame pointer. E.g.
 551         //
 552         //     movq %rsp, %rbp
 553         //  L0:
 554         //     .cfi_def_cfa_register %rbp
 555         //
 556         HasFP = true;
 557
 558         // If the frame pointer is other than esp/rsp, we do not have a way to
 559         // generate a compact unwinding representation, so bail out.
 560         if (MRI.getLLVMRegNum(Inst.getRegister(), true) !=
 561             (Is64Bit ? X86::RBP : X86::EBP))
 562           return 0;
 563
 564         // Reset the counts.
 565         memset(SavedRegs, 0, sizeof(SavedRegs));
 566         StackAdjust = 0;
 567         SavedRegIdx = 0;
 568         InstrOffset += MoveInstrSize;
 569         break;
 570       }
 571       case MCCFIInstruction::OpDefCfaOffset: {
 572         // Defines a new offset for the CFA. E.g.
 573         //
 574         //  With frame:
 575         //
 576         //     pushq %rbp
 577         //  L0:
 578         //     .cfi_def_cfa_offset 16
 579         //
 580         //  Without frame:
 581         //
 582         //     subq $72, %rsp
 583         //  L0:
 584         //     .cfi_def_cfa_offset 80
 585         //
 586         StackSize = std::abs(Inst.getOffset()) / StackDivide;
 587         ++NumDefCFAOffsets;
 588         break;
 589       }
 590       case MCCFIInstruction::OpOffset: {
 591         // Defines a "push" of a callee-saved register. E.g.
 592         //
 593         //     pushq %r15
 594         //     pushq %r14
 595         //     pushq %rbx
 596         //  L0:
 597         //     subq $120, %rsp
 598         //  L1:
 599         //     .cfi_offset %rbx, -40
 600         //     .cfi_offset %r14, -32
 601         //     .cfi_offset %r15, -24
 602         //
 603         if (SavedRegIdx == CU_NUM_SAVED_REGS)
 604           // If there are too many saved registers, we cannot use a compact
 605           // unwind encoding.
 606           return CU::UNWIND_MODE_DWARF;
 607
 608         unsigned Reg = MRI.getLLVMRegNum(Inst.getRegister(), true);
 609         SavedRegs[SavedRegIdx++] = Reg;
 610         StackAdjust += OffsetSize;
 611         InstrOffset += PushInstrSize(Reg);
 612         break;
 613       }
 614       }
 615     }
 616
 617     StackAdjust /= StackDivide;
 618
 619     if (HasFP) {
 620       if ((StackAdjust & 0xFF) != StackAdjust)
 621         // Offset was too big for a compact unwind encoding.
 622         return CU::UNWIND_MODE_DWARF;
 623
 624       // Get the encoding of the saved registers when we have a frame pointer.
 625       uint32_t RegEnc = encodeCompactUnwindRegistersWithFrame();
 626       if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
 627
 628       CompactUnwindEncoding |= CU::UNWIND_MODE_BP_FRAME;
 629       CompactUnwindEncoding |= (StackAdjust & 0xFF) << 16;
 630       CompactUnwindEncoding |= RegEnc & CU::UNWIND_BP_FRAME_REGISTERS;
 631     } else {
 632       SubtractInstrIdx += InstrOffset;
 633       ++StackAdjust;
 634
 635       if ((StackSize & 0xFF) == StackSize) {
 636         // Frameless stack with a small stack size.
 637         CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IMMD;
 638
 639         // Encode the stack size.
 640         CompactUnwindEncoding |= (StackSize & 0xFF) << 16;
 641       } else {
 642         if ((StackAdjust & 0x7) != StackAdjust)
 643           // The extra stack adjustments are too big for us to handle.
 644           return CU::UNWIND_MODE_DWARF;
 645
 646         // Frameless stack with an offset too large for us to encode compactly.
 647         CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IND;
 648
 649         // Encode the offset to the nnnnnn value in the 'subl $nnnnnn, ESP'
 650         // instruction.
 651         CompactUnwindEncoding |= (SubtractInstrIdx & 0xFF) << 16;
 652
 653         // Encode any extra stack adjustments (done via push instructions).
 654         CompactUnwindEncoding |= (StackAdjust & 0x7) << 13;
 655       }
 656
 657       // Encode the number of registers saved. (Reverse the list first.)
 658       std::reverse(&SavedRegs[0], &SavedRegs[SavedRegIdx]);
 659       CompactUnwindEncoding |= (SavedRegIdx & 0x7) << 10;
 660
 661       // Get the encoding of the saved registers when we don't have a frame
 662       // pointer.
 663       uint32_t RegEnc = encodeCompactUnwindRegistersWithoutFrame(SavedRegIdx);
 664       if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
 665
 666       // Encode the register encoding.
 667       CompactUnwindEncoding |=
 668         RegEnc & CU::UNWIND_FRAMELESS_STACK_REG_PERMUTATION;
 669     }
 670
 671     return CompactUnwindEncoding;
 672   }
 673
 674 private:
 675   /// Get the compact unwind number for a given register. The number
 676   /// corresponds to the enum lists in compact_unwind_encoding.h.
 677   int getCompactUnwindRegNum(unsigned Reg) const {
 678     static const MCPhysReg CU32BitRegs[7] = {
 679       X86::EBX, X86::ECX, X86::EDX, X86::EDI, X86::ESI, X86::EBP, 0
 680     };
 681     static const MCPhysReg CU64BitRegs[] = {
 682       X86::RBX, X86::R12, X86::R13, X86::R14, X86::R15, X86::RBP, 0
 683     };
 684     const MCPhysReg *CURegs = Is64Bit ? CU64BitRegs : CU32BitRegs;
 685     for (int Idx = 1; *CURegs; ++CURegs, ++Idx)
 686       if (*CURegs == Reg)
 687         return Idx;
 688
 689     return -1;
 690   }
 691
 692   /// Return the registers encoded for a compact encoding with a frame
 693   /// pointer.
 694   uint32_t encodeCompactUnwindRegistersWithFrame() const {
 695     // Encode the registers in the order they were saved --- 3-bits per
 696     // register. The list of saved registers is assumed to be in reverse
 697     // order. The registers are numbered from 1 to CU_NUM_SAVED_REGS.
 698     uint32_t RegEnc = 0;
 699     for (int i = 0, Idx = 0; i != CU_NUM_SAVED_REGS; ++i) {
 700       unsigned Reg = SavedRegs[i];
 701       if (Reg == 0) break;
 702
 703       int CURegNum = getCompactUnwindRegNum(Reg);
 704       if (CURegNum == -1) return ~0U;
 705
 706       // Encode the 3-bit register number in order, skipping over 3-bits for
 707       // each register.
 708       RegEnc |= (CURegNum & 0x7) << (Idx++ * 3);
 709     }
 710
 711     assert((RegEnc & 0x3FFFF) == RegEnc &&
 712            "Invalid compact register encoding!");
 713     return RegEnc;
 714   }
 715
 716   /// Create the permutation encoding used with frameless stacks. It is
 717   /// passed the number of registers to be saved and an array of the registers
 718   /// saved.
 719   uint32_t encodeCompactUnwindRegistersWithoutFrame(unsigned RegCount) const {
 720     // The saved registers are numbered from 1 to 6. In order to encode the
 721     // order in which they were saved, we re-number them according to their
 722     // place in the register order. The re-numbering is relative to the last
 723     // re-numbered register. E.g., if we have registers {6, 2, 4, 5} saved in
 724     // that order:
 725     //
 726     //    Orig  Re-Num
 727     //    ----  ------
 728     //     6       6
 729     //     2       2
 730     //     4       3
 731     //     5       3
 732     //
 733     for (unsigned i = 0; i < RegCount; ++i) {
 734       int CUReg = getCompactUnwindRegNum(SavedRegs[i]);
 735       if (CUReg == -1) return ~0U;
 736       SavedRegs[i] = CUReg;
 737     }
 738
 739     // Reverse the list.
 740     std::reverse(&SavedRegs[0], &SavedRegs[CU_NUM_SAVED_REGS]);
 741
 742     uint32_t RenumRegs[CU_NUM_SAVED_REGS];
 743     for (unsigned i = CU_NUM_SAVED_REGS - RegCount; i < CU_NUM_SAVED_REGS; ++i){
 744       unsigned Countless = 0;
 745       for (unsigned j = CU_NUM_SAVED_REGS - RegCount; j < i; ++j)
 746         if (SavedRegs[j] < SavedRegs[i])
 747           ++Countless;
 748
 749       RenumRegs[i] = SavedRegs[i] - Countless - 1;
 750     }
 751
 752     // Take the renumbered values and encode them into a 10-bit number.
 753     uint32_t permutationEncoding = 0;
 754     switch (RegCount) {
 755     case 6:
 756       permutationEncoding |= 120 * RenumRegs[0] + 24 * RenumRegs[1]
 757                              + 6 * RenumRegs[2] +  2 * RenumRegs[3]
 758                              +     RenumRegs[4];
 759       break;
 760     case 5:
 761       permutationEncoding |= 120 * RenumRegs[1] + 24 * RenumRegs[2]
 762                              + 6 * RenumRegs[3] +  2 * RenumRegs[4]
 763                              +     RenumRegs[5];
 764       break;
 765     case 4:
 766       permutationEncoding |=  60 * RenumRegs[2] + 12 * RenumRegs[3]
 767                              + 3 * RenumRegs[4] +      RenumRegs[5];
 768       break;
 769     case 3:
 770       permutationEncoding |=  20 * RenumRegs[3] +  4 * RenumRegs[4]
 771                              +     RenumRegs[5];
 772       break;
 773     case 2:
 774       permutationEncoding |=   5 * RenumRegs[4] +      RenumRegs[5];
 775       break;
 776     case 1:
 777       permutationEncoding |=       RenumRegs[5];
 778       break;
 779     }
 780
 781     assert((permutationEncoding & 0x3FF) == permutationEncoding &&
 782            "Invalid compact register encoding!");
 783     return permutationEncoding;
 784   }
 785
 786 public:
 787   DarwinX86AsmBackend(const Target &T, const MCRegisterInfo &MRI,
 788                       const MCSubtargetInfo &STI, bool Is64Bit)
 789     : X86AsmBackend(T, STI), MRI(MRI), Is64Bit(Is64Bit) {
 790     memset(SavedRegs, 0, sizeof(SavedRegs));
 791     OffsetSize = Is64Bit ? 8 : 4;
 792     MoveInstrSize = Is64Bit ? 3 : 2;
 793     StackDivide = Is64Bit ? 8 : 4;
 794   }
 795 };
 796
 797 class DarwinX86_32AsmBackend : public DarwinX86AsmBackend {
 798 public:
 799   DarwinX86_32AsmBackend(const Target &T, const MCRegisterInfo &MRI,
 800                          const MCSubtargetInfo &STI)
 801       : DarwinX86AsmBackend(T, MRI, STI, false) {}
 802
 803   std::unique_ptr<MCObjectTargetWriter>
 804   createObjectTargetWriter() const override {
 805     return createX86MachObjectWriter(/*Is64Bit=*/false,
 806                                      MachO::CPU_TYPE_I386,
 807                                      MachO::CPU_SUBTYPE_I386_ALL);
 808   }
 809
 810   /// Generate the compact unwind encoding for the CFI instructions.
 811   uint32_t generateCompactUnwindEncoding(
 812                              ArrayRef<MCCFIInstruction> Instrs) const override {
 813     return generateCompactUnwindEncodingImpl(Instrs);
 814   }
 815 };
 816
 817 class DarwinX86_64AsmBackend : public DarwinX86AsmBackend {
 818   const MachO::CPUSubTypeX86 Subtype;
 819 public:
 820   DarwinX86_64AsmBackend(const Target &T, const MCRegisterInfo &MRI,
 821                          const MCSubtargetInfo &STI, MachO::CPUSubTypeX86 st)
 822       : DarwinX86AsmBackend(T, MRI, STI, true), Subtype(st) {}
 823
 824   std::unique_ptr<MCObjectTargetWriter>
 825   createObjectTargetWriter() const override {
 826     return createX86MachObjectWriter(/*Is64Bit=*/true, MachO::CPU_TYPE_X86_64,
 827                                      Subtype);
 828   }
 829
 830   /// Generate the compact unwind encoding for the CFI instructions.
 831   uint32_t generateCompactUnwindEncoding(
 832                              ArrayRef<MCCFIInstruction> Instrs) const override {
 833     return generateCompactUnwindEncodingImpl(Instrs);
 834   }
 835 };
 836
 837 } // end anonymous namespace
 838
 839 MCAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
 840                                            const MCSubtargetInfo &STI,
 841                                            const MCRegisterInfo &MRI,
 842                                            const MCTargetOptions &Options) {
 843   const Triple &TheTriple = STI.getTargetTriple();
 844   if (TheTriple.isOSBinFormatMachO())
 845     return new DarwinX86_32AsmBackend(T, MRI, STI);
 846
 847   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
 848     return new WindowsX86AsmBackend(T, false, STI);
 849
 850   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 851
 852   if (TheTriple.isOSIAMCU())
 853     return new ELFX86_IAMCUAsmBackend(T, OSABI, STI);
 854
 855   return new ELFX86_32AsmBackend(T, OSABI, STI);
 856 }
 857
 858 MCAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
 859                                            const MCSubtargetInfo &STI,
 860                                            const MCRegisterInfo &MRI,
 861                                            const MCTargetOptions &Options) {
 862   const Triple &TheTriple = STI.getTargetTriple();
 863   if (TheTriple.isOSBinFormatMachO()) {
 864     MachO::CPUSubTypeX86 CS =
 865         StringSwitch<MachO::CPUSubTypeX86>(TheTriple.getArchName())
 866             .Case("x86_64h", MachO::CPU_SUBTYPE_X86_64_H)
 867             .Default(MachO::CPU_SUBTYPE_X86_64_ALL);
 868     return new DarwinX86_64AsmBackend(T, MRI, STI, CS);
 869   }
 870
 871   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
 872     return new WindowsX86AsmBackend(T, true, STI);
 873
 874   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 875
 876   if (TheTriple.getEnvironment() == Triple::GNUX32)
 877     return new ELFX86_X32AsmBackend(T, OSABI, STI);
 878   return new ELFX86_64AsmBackend(T, OSABI, STI);
 879 }