include/llvm/MC/MCExpr.h

   1 //===- MCExpr.h - Assembly Level Expressions --------------------*- C++ -*-===//
   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 #ifndef LLVM_MC_MCEXPR_H
  10 #define LLVM_MC_MCEXPR_H
  11
  12 #include "llvm/ADT/DenseMap.h"
  13 #include "llvm/Support/SMLoc.h"
  14 #include <cstdint>
  15
  16 namespace llvm {
  17
  18 class MCAsmInfo;
  19 class MCAsmLayout;
  20 class MCAssembler;
  21 class MCContext;
  22 class MCFixup;
  23 class MCFragment;
  24 class MCSection;
  25 class MCStreamer;
  26 class MCSymbol;
  27 class MCValue;
  28 class raw_ostream;
  29 class StringRef;
  30
  31 using SectionAddrMap = DenseMap<const MCSection *, uint64_t>;
  32
  33 /// Base class for the full range of assembler expressions which are
  34 /// needed for parsing.
  35 class MCExpr {
  36 public:
  37   enum ExprKind {
  38     Binary,    ///< Binary expressions.
  39     Constant,  ///< Constant expressions.
  40     SymbolRef, ///< References to labels and assigned expressions.
  41     Unary,     ///< Unary expressions.
  42     Target     ///< Target specific expression.
  43   };
  44
  45 private:
  46   ExprKind Kind;
  47   SMLoc Loc;
  48
  49   bool evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
  50                           const MCAsmLayout *Layout,
  51                           const SectionAddrMap *Addrs, bool InSet) const;
  52
  53 protected:
  54   explicit MCExpr(ExprKind Kind, SMLoc Loc) : Kind(Kind), Loc(Loc) {}
  55
  56   bool evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
  57                                  const MCAsmLayout *Layout,
  58                                  const MCFixup *Fixup,
  59                                  const SectionAddrMap *Addrs, bool InSet) const;
  60
  61 public:
  62   MCExpr(const MCExpr &) = delete;
  63   MCExpr &operator=(const MCExpr &) = delete;
  64
  65   /// \name Accessors
  66   /// @{
  67
  68   ExprKind getKind() const { return Kind; }
  69   SMLoc getLoc() const { return Loc; }
  70
  71   /// @}
  72   /// \name Utility Methods
  73   /// @{
  74
  75   void print(raw_ostream &OS, const MCAsmInfo *MAI,
  76              bool InParens = false) const;
  77   void dump() const;
  78
  79   /// @}
  80   /// \name Expression Evaluation
  81   /// @{
  82
  83   /// Try to evaluate the expression to an absolute value.
  84   ///
  85   /// \param Res - The absolute value, if evaluation succeeds.
  86   /// \param Layout - The assembler layout object to use for evaluating symbol
  87   /// values. If not given, then only non-symbolic expressions will be
  88   /// evaluated.
  89   /// \return - True on success.
  90   bool evaluateAsAbsolute(int64_t &Res, const MCAsmLayout &Layout,
  91                           const SectionAddrMap &Addrs) const;
  92   bool evaluateAsAbsolute(int64_t &Res) const;
  93   bool evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const;
  94   bool evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm) const;
  95   bool evaluateAsAbsolute(int64_t &Res, const MCAsmLayout &Layout) const;
  96
  97   bool evaluateKnownAbsolute(int64_t &Res, const MCAsmLayout &Layout) const;
  98
  99   /// Try to evaluate the expression to a relocatable value, i.e. an
 100   /// expression of the fixed form (a - b + constant).
 101   ///
 102   /// \param Res - The relocatable value, if evaluation succeeds.
 103   /// \param Layout - The assembler layout object to use for evaluating values.
 104   /// \param Fixup - The Fixup object if available.
 105   /// \return - True on success.
 106   bool evaluateAsRelocatable(MCValue &Res, const MCAsmLayout *Layout,
 107                              const MCFixup *Fixup) const;
 108
 109   /// Try to evaluate the expression to the form (a - b + constant) where
 110   /// neither a nor b are variables.
 111   ///
 112   /// This is a more aggressive variant of evaluateAsRelocatable. The intended
 113   /// use is for when relocations are not available, like the .size directive.
 114   bool evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const;
 115
 116   /// Find the "associated section" for this expression, which is
 117   /// currently defined as the absolute section for constants, or
 118   /// otherwise the section associated with the first defined symbol in the
 119   /// expression.
 120   MCFragment *findAssociatedFragment() const;
 121
 122   /// @}
 123 };
 124
 125 inline raw_ostream &operator<<(raw_ostream &OS, const MCExpr &E) {
 126   E.print(OS, nullptr);
 127   return OS;
 128 }
 129
 130 ////  Represent a constant integer expression.
 131 class MCConstantExpr : public MCExpr {
 132   int64_t Value;
 133   bool PrintInHex = false;
 134
 135   explicit MCConstantExpr(int64_t Value)
 136       : MCExpr(MCExpr::Constant, SMLoc()), Value(Value) {}
 137
 138   MCConstantExpr(int64_t Value, bool PrintInHex)
 139       : MCExpr(MCExpr::Constant, SMLoc()), Value(Value),
 140         PrintInHex(PrintInHex) {}
 141
 142 public:
 143   /// \name Construction
 144   /// @{
 145
 146   static const MCConstantExpr *create(int64_t Value, MCContext &Ctx,
 147                                       bool PrintInHex = false);
 148
 149   /// @}
 150   /// \name Accessors
 151   /// @{
 152
 153   int64_t getValue() const { return Value; }
 154
 155   bool useHexFormat() const { return PrintInHex; }
 156
 157   /// @}
 158
 159   static bool classof(const MCExpr *E) {
 160     return E->getKind() == MCExpr::Constant;
 161   }
 162 };
 163
 164 ///  Represent a reference to a symbol from inside an expression.
 165 ///
 166 /// A symbol reference in an expression may be a use of a label, a use of an
 167 /// assembler variable (defined constant), or constitute an implicit definition
 168 /// of the symbol as external.
 169 class MCSymbolRefExpr : public MCExpr {
 170 public:
 171   enum VariantKind : uint16_t {
 172     VK_None,
 173     VK_Invalid,
 174
 175     VK_GOT,
 176     VK_GOTOFF,
 177     VK_GOTREL,
 178     VK_GOTPCREL,
 179     VK_GOTTPOFF,
 180     VK_INDNTPOFF,
 181     VK_NTPOFF,
 182     VK_GOTNTPOFF,
 183     VK_PLT,
 184     VK_TLSGD,
 185     VK_TLSLD,
 186     VK_TLSLDM,
 187     VK_TPOFF,
 188     VK_DTPOFF,
 189     VK_TLSCALL,   // symbol(tlscall)
 190     VK_TLSDESC,   // symbol(tlsdesc)
 191     VK_TLVP,      // Mach-O thread local variable relocations
 192     VK_TLVPPAGE,
 193     VK_TLVPPAGEOFF,
 194     VK_PAGE,
 195     VK_PAGEOFF,
 196     VK_GOTPAGE,
 197     VK_GOTPAGEOFF,
 198     VK_SECREL,
 199     VK_SIZE,      // symbol@SIZE
 200     VK_WEAKREF,   // The link between the symbols in .weakref foo, bar
 201
 202     VK_X86_ABS8,
 203
 204     VK_ARM_NONE,
 205     VK_ARM_GOT_PREL,
 206     VK_ARM_TARGET1,
 207     VK_ARM_TARGET2,
 208     VK_ARM_PREL31,
 209     VK_ARM_SBREL,          // symbol(sbrel)
 210     VK_ARM_TLSLDO,         // symbol(tlsldo)
 211     VK_ARM_TLSDESCSEQ,
 212
 213     VK_AVR_NONE,
 214     VK_AVR_LO8,
 215     VK_AVR_HI8,
 216     VK_AVR_HLO8,
 217     VK_AVR_DIFF8,
 218     VK_AVR_DIFF16,
 219     VK_AVR_DIFF32,
 220
 221     VK_PPC_LO,             // symbol@l
 222     VK_PPC_HI,             // symbol@h
 223     VK_PPC_HA,             // symbol@ha
 224     VK_PPC_HIGH,           // symbol@high
 225     VK_PPC_HIGHA,          // symbol@higha
 226     VK_PPC_HIGHER,         // symbol@higher
 227     VK_PPC_HIGHERA,        // symbol@highera
 228     VK_PPC_HIGHEST,        // symbol@highest
 229     VK_PPC_HIGHESTA,       // symbol@highesta
 230     VK_PPC_GOT_LO,         // symbol@got@l
 231     VK_PPC_GOT_HI,         // symbol@got@h
 232     VK_PPC_GOT_HA,         // symbol@got@ha
 233     VK_PPC_TOCBASE,        // symbol@tocbase
 234     VK_PPC_TOC,            // symbol@toc
 235     VK_PPC_TOC_LO,         // symbol@toc@l
 236     VK_PPC_TOC_HI,         // symbol@toc@h
 237     VK_PPC_TOC_HA,         // symbol@toc@ha
 238     VK_PPC_U,              // symbol@u
 239     VK_PPC_L,              // symbol@l
 240     VK_PPC_DTPMOD,         // symbol@dtpmod
 241     VK_PPC_TPREL_LO,       // symbol@tprel@l
 242     VK_PPC_TPREL_HI,       // symbol@tprel@h
 243     VK_PPC_TPREL_HA,       // symbol@tprel@ha
 244     VK_PPC_TPREL_HIGH,     // symbol@tprel@high
 245     VK_PPC_TPREL_HIGHA,    // symbol@tprel@higha
 246     VK_PPC_TPREL_HIGHER,   // symbol@tprel@higher
 247     VK_PPC_TPREL_HIGHERA,  // symbol@tprel@highera
 248     VK_PPC_TPREL_HIGHEST,  // symbol@tprel@highest
 249     VK_PPC_TPREL_HIGHESTA, // symbol@tprel@highesta
 250     VK_PPC_DTPREL_LO,      // symbol@dtprel@l
 251     VK_PPC_DTPREL_HI,      // symbol@dtprel@h
 252     VK_PPC_DTPREL_HA,      // symbol@dtprel@ha
 253     VK_PPC_DTPREL_HIGH,    // symbol@dtprel@high
 254     VK_PPC_DTPREL_HIGHA,   // symbol@dtprel@higha
 255     VK_PPC_DTPREL_HIGHER,  // symbol@dtprel@higher
 256     VK_PPC_DTPREL_HIGHERA, // symbol@dtprel@highera
 257     VK_PPC_DTPREL_HIGHEST, // symbol@dtprel@highest
 258     VK_PPC_DTPREL_HIGHESTA,// symbol@dtprel@highesta
 259     VK_PPC_GOT_TPREL,      // symbol@got@tprel
 260     VK_PPC_GOT_TPREL_LO,   // symbol@got@tprel@l
 261     VK_PPC_GOT_TPREL_HI,   // symbol@got@tprel@h
 262     VK_PPC_GOT_TPREL_HA,   // symbol@got@tprel@ha
 263     VK_PPC_GOT_DTPREL,     // symbol@got@dtprel
 264     VK_PPC_GOT_DTPREL_LO,  // symbol@got@dtprel@l
 265     VK_PPC_GOT_DTPREL_HI,  // symbol@got@dtprel@h
 266     VK_PPC_GOT_DTPREL_HA,  // symbol@got@dtprel@ha
 267     VK_PPC_TLS,            // symbol@tls
 268     VK_PPC_GOT_TLSGD,      // symbol@got@tlsgd
 269     VK_PPC_GOT_TLSGD_LO,   // symbol@got@tlsgd@l
 270     VK_PPC_GOT_TLSGD_HI,   // symbol@got@tlsgd@h
 271     VK_PPC_GOT_TLSGD_HA,   // symbol@got@tlsgd@ha
 272     VK_PPC_TLSGD,          // symbol@tlsgd
 273     VK_PPC_GOT_TLSLD,      // symbol@got@tlsld
 274     VK_PPC_GOT_TLSLD_LO,   // symbol@got@tlsld@l
 275     VK_PPC_GOT_TLSLD_HI,   // symbol@got@tlsld@h
 276     VK_PPC_GOT_TLSLD_HA,   // symbol@got@tlsld@ha
 277     VK_PPC_TLSLD,          // symbol@tlsld
 278     VK_PPC_LOCAL,          // symbol@local
 279
 280     VK_COFF_IMGREL32, // symbol@imgrel (image-relative)
 281
 282     VK_Hexagon_PCREL,
 283     VK_Hexagon_LO16,
 284     VK_Hexagon_HI16,
 285     VK_Hexagon_GPREL,
 286     VK_Hexagon_GD_GOT,
 287     VK_Hexagon_LD_GOT,
 288     VK_Hexagon_GD_PLT,
 289     VK_Hexagon_LD_PLT,
 290     VK_Hexagon_IE,
 291     VK_Hexagon_IE_GOT,
 292
 293     VK_WASM_TYPEINDEX, // Reference to a symbol's type (signature)
 294     VK_WASM_MBREL,     // Memory address relative to memory base
 295     VK_WASM_TBREL,     // Table index relative to table bare
 296
 297     VK_AMDGPU_GOTPCREL32_LO, // symbol@gotpcrel32@lo
 298     VK_AMDGPU_GOTPCREL32_HI, // symbol@gotpcrel32@hi
 299     VK_AMDGPU_REL32_LO,      // symbol@rel32@lo
 300     VK_AMDGPU_REL32_HI,      // symbol@rel32@hi
 301     VK_AMDGPU_REL64,         // symbol@rel64
 302     VK_AMDGPU_ABS32_LO,      // symbol@abs32@lo
 303     VK_AMDGPU_ABS32_HI,      // symbol@abs32@hi
 304
 305     VK_TPREL,
 306     VK_DTPREL
 307   };
 308
 309 private:
 310   /// The symbol reference modifier.
 311   const VariantKind Kind;
 312
 313   /// Specifies how the variant kind should be printed.
 314   const unsigned UseParensForSymbolVariant : 1;
 315
 316   // FIXME: Remove this bit.
 317   const unsigned HasSubsectionsViaSymbols : 1;
 318
 319   /// The symbol being referenced.
 320   const MCSymbol *Symbol;
 321
 322   explicit MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
 323                            const MCAsmInfo *MAI, SMLoc Loc = SMLoc());
 324
 325 public:
 326   /// \name Construction
 327   /// @{
 328
 329   static const MCSymbolRefExpr *create(const MCSymbol *Symbol, MCContext &Ctx) {
 330     return MCSymbolRefExpr::create(Symbol, VK_None, Ctx);
 331   }
 332
 333   static const MCSymbolRefExpr *create(const MCSymbol *Symbol, VariantKind Kind,
 334                                        MCContext &Ctx, SMLoc Loc = SMLoc());
 335   static const MCSymbolRefExpr *create(StringRef Name, VariantKind Kind,
 336                                        MCContext &Ctx);
 337
 338   /// @}
 339   /// \name Accessors
 340   /// @{
 341
 342   const MCSymbol &getSymbol() const { return *Symbol; }
 343
 344   VariantKind getKind() const { return Kind; }
 345
 346   void printVariantKind(raw_ostream &OS) const;
 347
 348   bool hasSubsectionsViaSymbols() const { return HasSubsectionsViaSymbols; }
 349
 350   /// @}
 351   /// \name Static Utility Functions
 352   /// @{
 353
 354   static StringRef getVariantKindName(VariantKind Kind);
 355
 356   static VariantKind getVariantKindForName(StringRef Name);
 357
 358   /// @}
 359
 360   static bool classof(const MCExpr *E) {
 361     return E->getKind() == MCExpr::SymbolRef;
 362   }
 363 };
 364
 365 /// Unary assembler expressions.
 366 class MCUnaryExpr : public MCExpr {
 367 public:
 368   enum Opcode {
 369     LNot,  ///< Logical negation.
 370     Minus, ///< Unary minus.
 371     Not,   ///< Bitwise negation.
 372     Plus   ///< Unary plus.
 373   };
 374
 375 private:
 376   Opcode Op;
 377   const MCExpr *Expr;
 378
 379   MCUnaryExpr(Opcode Op, const MCExpr *Expr, SMLoc Loc)
 380       : MCExpr(MCExpr::Unary, Loc), Op(Op), Expr(Expr) {}
 381
 382 public:
 383   /// \name Construction
 384   /// @{
 385
 386   static const MCUnaryExpr *create(Opcode Op, const MCExpr *Expr,
 387                                    MCContext &Ctx, SMLoc Loc = SMLoc());
 388
 389   static const MCUnaryExpr *createLNot(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 390     return create(LNot, Expr, Ctx, Loc);
 391   }
 392
 393   static const MCUnaryExpr *createMinus(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 394     return create(Minus, Expr, Ctx, Loc);
 395   }
 396
 397   static const MCUnaryExpr *createNot(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 398     return create(Not, Expr, Ctx, Loc);
 399   }
 400
 401   static const MCUnaryExpr *createPlus(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 402     return create(Plus, Expr, Ctx, Loc);
 403   }
 404
 405   /// @}
 406   /// \name Accessors
 407   /// @{
 408
 409   /// Get the kind of this unary expression.
 410   Opcode getOpcode() const { return Op; }
 411
 412   /// Get the child of this unary expression.
 413   const MCExpr *getSubExpr() const { return Expr; }
 414
 415   /// @}
 416
 417   static bool classof(const MCExpr *E) {
 418     return E->getKind() == MCExpr::Unary;
 419   }
 420 };
 421
 422 /// Binary assembler expressions.
 423 class MCBinaryExpr : public MCExpr {
 424 public:
 425   enum Opcode {
 426     Add,  ///< Addition.
 427     And,  ///< Bitwise and.
 428     Div,  ///< Signed division.
 429     EQ,   ///< Equality comparison.
 430     GT,   ///< Signed greater than comparison (result is either 0 or some
 431           ///< target-specific non-zero value)
 432     GTE,  ///< Signed greater than or equal comparison (result is either 0 or
 433           ///< some target-specific non-zero value).
 434     LAnd, ///< Logical and.
 435     LOr,  ///< Logical or.
 436     LT,   ///< Signed less than comparison (result is either 0 or
 437           ///< some target-specific non-zero value).
 438     LTE,  ///< Signed less than or equal comparison (result is either 0 or
 439           ///< some target-specific non-zero value).
 440     Mod,  ///< Signed remainder.
 441     Mul,  ///< Multiplication.
 442     NE,   ///< Inequality comparison.
 443     Or,   ///< Bitwise or.
 444     Shl,  ///< Shift left.
 445     AShr, ///< Arithmetic shift right.
 446     LShr, ///< Logical shift right.
 447     Sub,  ///< Subtraction.
 448     Xor   ///< Bitwise exclusive or.
 449   };
 450
 451 private:
 452   Opcode Op;
 453   const MCExpr *LHS, *RHS;
 454
 455   MCBinaryExpr(Opcode Op, const MCExpr *LHS, const MCExpr *RHS,
 456                SMLoc Loc = SMLoc())
 457       : MCExpr(MCExpr::Binary, Loc), Op(Op), LHS(LHS), RHS(RHS) {}
 458
 459 public:
 460   /// \name Construction
 461   /// @{
 462
 463   static const MCBinaryExpr *create(Opcode Op, const MCExpr *LHS,
 464                                     const MCExpr *RHS, MCContext &Ctx,
 465                                     SMLoc Loc = SMLoc());
 466
 467   static const MCBinaryExpr *createAdd(const MCExpr *LHS, const MCExpr *RHS,
 468                                        MCContext &Ctx) {
 469     return create(Add, LHS, RHS, Ctx);
 470   }
 471
 472   static const MCBinaryExpr *createAnd(const MCExpr *LHS, const MCExpr *RHS,
 473                                        MCContext &Ctx) {
 474     return create(And, LHS, RHS, Ctx);
 475   }
 476
 477   static const MCBinaryExpr *createDiv(const MCExpr *LHS, const MCExpr *RHS,
 478                                        MCContext &Ctx) {
 479     return create(Div, LHS, RHS, Ctx);
 480   }
 481
 482   static const MCBinaryExpr *createEQ(const MCExpr *LHS, const MCExpr *RHS,
 483                                       MCContext &Ctx) {
 484     return create(EQ, LHS, RHS, Ctx);
 485   }
 486
 487   static const MCBinaryExpr *createGT(const MCExpr *LHS, const MCExpr *RHS,
 488                                       MCContext &Ctx) {
 489     return create(GT, LHS, RHS, Ctx);
 490   }
 491
 492   static const MCBinaryExpr *createGTE(const MCExpr *LHS, const MCExpr *RHS,
 493                                        MCContext &Ctx) {
 494     return create(GTE, LHS, RHS, Ctx);
 495   }
 496
 497   static const MCBinaryExpr *createLAnd(const MCExpr *LHS, const MCExpr *RHS,
 498                                         MCContext &Ctx) {
 499     return create(LAnd, LHS, RHS, Ctx);
 500   }
 501
 502   static const MCBinaryExpr *createLOr(const MCExpr *LHS, const MCExpr *RHS,
 503                                        MCContext &Ctx) {
 504     return create(LOr, LHS, RHS, Ctx);
 505   }
 506
 507   static const MCBinaryExpr *createLT(const MCExpr *LHS, const MCExpr *RHS,
 508                                       MCContext &Ctx) {
 509     return create(LT, LHS, RHS, Ctx);
 510   }
 511
 512   static const MCBinaryExpr *createLTE(const MCExpr *LHS, const MCExpr *RHS,
 513                                        MCContext &Ctx) {
 514     return create(LTE, LHS, RHS, Ctx);
 515   }
 516
 517   static const MCBinaryExpr *createMod(const MCExpr *LHS, const MCExpr *RHS,
 518                                        MCContext &Ctx) {
 519     return create(Mod, LHS, RHS, Ctx);
 520   }
 521
 522   static const MCBinaryExpr *createMul(const MCExpr *LHS, const MCExpr *RHS,
 523                                        MCContext &Ctx) {
 524     return create(Mul, LHS, RHS, Ctx);
 525   }
 526
 527   static const MCBinaryExpr *createNE(const MCExpr *LHS, const MCExpr *RHS,
 528                                       MCContext &Ctx) {
 529     return create(NE, LHS, RHS, Ctx);
 530   }
 531
 532   static const MCBinaryExpr *createOr(const MCExpr *LHS, const MCExpr *RHS,
 533                                       MCContext &Ctx) {
 534     return create(Or, LHS, RHS, Ctx);
 535   }
 536
 537   static const MCBinaryExpr *createShl(const MCExpr *LHS, const MCExpr *RHS,
 538                                        MCContext &Ctx) {
 539     return create(Shl, LHS, RHS, Ctx);
 540   }
 541
 542   static const MCBinaryExpr *createAShr(const MCExpr *LHS, const MCExpr *RHS,
 543                                        MCContext &Ctx) {
 544     return create(AShr, LHS, RHS, Ctx);
 545   }
 546
 547   static const MCBinaryExpr *createLShr(const MCExpr *LHS, const MCExpr *RHS,
 548                                        MCContext &Ctx) {
 549     return create(LShr, LHS, RHS, Ctx);
 550   }
 551
 552   static const MCBinaryExpr *createSub(const MCExpr *LHS, const MCExpr *RHS,
 553                                        MCContext &Ctx) {
 554     return create(Sub, LHS, RHS, Ctx);
 555   }
 556
 557   static const MCBinaryExpr *createXor(const MCExpr *LHS, const MCExpr *RHS,
 558                                        MCContext &Ctx) {
 559     return create(Xor, LHS, RHS, Ctx);
 560   }
 561
 562   /// @}
 563   /// \name Accessors
 564   /// @{
 565
 566   /// Get the kind of this binary expression.
 567   Opcode getOpcode() const { return Op; }
 568
 569   /// Get the left-hand side expression of the binary operator.
 570   const MCExpr *getLHS() const { return LHS; }
 571
 572   /// Get the right-hand side expression of the binary operator.
 573   const MCExpr *getRHS() const { return RHS; }
 574
 575   /// @}
 576
 577   static bool classof(const MCExpr *E) {
 578     return E->getKind() == MCExpr::Binary;
 579   }
 580 };
 581
 582 /// This is an extension point for target-specific MCExpr subclasses to
 583 /// implement.
 584 ///
 585 /// NOTE: All subclasses are required to have trivial destructors because
 586 /// MCExprs are bump pointer allocated and not destructed.
 587 class MCTargetExpr : public MCExpr {
 588   virtual void anchor();
 589
 590 protected:
 591   MCTargetExpr() : MCExpr(Target, SMLoc()) {}
 592   virtual ~MCTargetExpr() = default;
 593
 594 public:
 595   virtual void printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const = 0;
 596   virtual bool evaluateAsRelocatableImpl(MCValue &Res,
 597                                          const MCAsmLayout *Layout,
 598                                          const MCFixup *Fixup) const = 0;
 599   // allow Target Expressions to be checked for equality
 600   virtual bool isEqualTo(const MCExpr *x) const { return false; }
 601   // This should be set when assigned expressions are not valid ".set"
 602   // expressions, e.g. registers, and must be inlined.
 603   virtual bool inlineAssignedExpr() const { return false; }
 604   virtual void visitUsedExpr(MCStreamer& Streamer) const = 0;
 605   virtual MCFragment *findAssociatedFragment() const = 0;
 606
 607   virtual void fixELFSymbolsInTLSFixups(MCAssembler &) const = 0;
 608
 609   static bool classof(const MCExpr *E) {
 610     return E->getKind() == MCExpr::Target;
 611   }
 612 };
 613
 614 } // end namespace llvm
 615
 616 #endif // LLVM_MC_MCEXPR_H