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_DTPMOD,         // symbol@dtpmod
 239     VK_PPC_TPREL_LO,       // symbol@tprel@l
 240     VK_PPC_TPREL_HI,       // symbol@tprel@h
 241     VK_PPC_TPREL_HA,       // symbol@tprel@ha
 242     VK_PPC_TPREL_HIGH,     // symbol@tprel@high
 243     VK_PPC_TPREL_HIGHA,    // symbol@tprel@higha
 244     VK_PPC_TPREL_HIGHER,   // symbol@tprel@higher
 245     VK_PPC_TPREL_HIGHERA,  // symbol@tprel@highera
 246     VK_PPC_TPREL_HIGHEST,  // symbol@tprel@highest
 247     VK_PPC_TPREL_HIGHESTA, // symbol@tprel@highesta
 248     VK_PPC_DTPREL_LO,      // symbol@dtprel@l
 249     VK_PPC_DTPREL_HI,      // symbol@dtprel@h
 250     VK_PPC_DTPREL_HA,      // symbol@dtprel@ha
 251     VK_PPC_DTPREL_HIGH,    // symbol@dtprel@high
 252     VK_PPC_DTPREL_HIGHA,   // symbol@dtprel@higha
 253     VK_PPC_DTPREL_HIGHER,  // symbol@dtprel@higher
 254     VK_PPC_DTPREL_HIGHERA, // symbol@dtprel@highera
 255     VK_PPC_DTPREL_HIGHEST, // symbol@dtprel@highest
 256     VK_PPC_DTPREL_HIGHESTA,// symbol@dtprel@highesta
 257     VK_PPC_GOT_TPREL,      // symbol@got@tprel
 258     VK_PPC_GOT_TPREL_LO,   // symbol@got@tprel@l
 259     VK_PPC_GOT_TPREL_HI,   // symbol@got@tprel@h
 260     VK_PPC_GOT_TPREL_HA,   // symbol@got@tprel@ha
 261     VK_PPC_GOT_DTPREL,     // symbol@got@dtprel
 262     VK_PPC_GOT_DTPREL_LO,  // symbol@got@dtprel@l
 263     VK_PPC_GOT_DTPREL_HI,  // symbol@got@dtprel@h
 264     VK_PPC_GOT_DTPREL_HA,  // symbol@got@dtprel@ha
 265     VK_PPC_TLS,            // symbol@tls
 266     VK_PPC_GOT_TLSGD,      // symbol@got@tlsgd
 267     VK_PPC_GOT_TLSGD_LO,   // symbol@got@tlsgd@l
 268     VK_PPC_GOT_TLSGD_HI,   // symbol@got@tlsgd@h
 269     VK_PPC_GOT_TLSGD_HA,   // symbol@got@tlsgd@ha
 270     VK_PPC_TLSGD,          // symbol@tlsgd
 271     VK_PPC_GOT_TLSLD,      // symbol@got@tlsld
 272     VK_PPC_GOT_TLSLD_LO,   // symbol@got@tlsld@l
 273     VK_PPC_GOT_TLSLD_HI,   // symbol@got@tlsld@h
 274     VK_PPC_GOT_TLSLD_HA,   // symbol@got@tlsld@ha
 275     VK_PPC_TLSLD,          // symbol@tlsld
 276     VK_PPC_LOCAL,          // symbol@local
 277
 278     VK_COFF_IMGREL32, // symbol@imgrel (image-relative)
 279
 280     VK_Hexagon_PCREL,
 281     VK_Hexagon_LO16,
 282     VK_Hexagon_HI16,
 283     VK_Hexagon_GPREL,
 284     VK_Hexagon_GD_GOT,
 285     VK_Hexagon_LD_GOT,
 286     VK_Hexagon_GD_PLT,
 287     VK_Hexagon_LD_PLT,
 288     VK_Hexagon_IE,
 289     VK_Hexagon_IE_GOT,
 290
 291     VK_WASM_TYPEINDEX, // Reference to a symbol's type (signature)
 292     VK_WASM_MBREL,     // Memory address relative to memory base
 293     VK_WASM_TBREL,     // Table index relative to table bare
 294
 295     VK_AMDGPU_GOTPCREL32_LO, // symbol@gotpcrel32@lo
 296     VK_AMDGPU_GOTPCREL32_HI, // symbol@gotpcrel32@hi
 297     VK_AMDGPU_REL32_LO,      // symbol@rel32@lo
 298     VK_AMDGPU_REL32_HI,      // symbol@rel32@hi
 299     VK_AMDGPU_REL64,         // symbol@rel64
 300     VK_AMDGPU_ABS32_LO,      // symbol@abs32@lo
 301     VK_AMDGPU_ABS32_HI,      // symbol@abs32@hi
 302
 303     VK_TPREL,
 304     VK_DTPREL
 305   };
 306
 307 private:
 308   /// The symbol reference modifier.
 309   const VariantKind Kind;
 310
 311   /// Specifies how the variant kind should be printed.
 312   const unsigned UseParensForSymbolVariant : 1;
 313
 314   // FIXME: Remove this bit.
 315   const unsigned HasSubsectionsViaSymbols : 1;
 316
 317   /// The symbol being referenced.
 318   const MCSymbol *Symbol;
 319
 320   explicit MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
 321                            const MCAsmInfo *MAI, SMLoc Loc = SMLoc());
 322
 323 public:
 324   /// \name Construction
 325   /// @{
 326
 327   static const MCSymbolRefExpr *create(const MCSymbol *Symbol, MCContext &Ctx) {
 328     return MCSymbolRefExpr::create(Symbol, VK_None, Ctx);
 329   }
 330
 331   static const MCSymbolRefExpr *create(const MCSymbol *Symbol, VariantKind Kind,
 332                                        MCContext &Ctx, SMLoc Loc = SMLoc());
 333   static const MCSymbolRefExpr *create(StringRef Name, VariantKind Kind,
 334                                        MCContext &Ctx);
 335
 336   /// @}
 337   /// \name Accessors
 338   /// @{
 339
 340   const MCSymbol &getSymbol() const { return *Symbol; }
 341
 342   VariantKind getKind() const { return Kind; }
 343
 344   void printVariantKind(raw_ostream &OS) const;
 345
 346   bool hasSubsectionsViaSymbols() const { return HasSubsectionsViaSymbols; }
 347
 348   /// @}
 349   /// \name Static Utility Functions
 350   /// @{
 351
 352   static StringRef getVariantKindName(VariantKind Kind);
 353
 354   static VariantKind getVariantKindForName(StringRef Name);
 355
 356   /// @}
 357
 358   static bool classof(const MCExpr *E) {
 359     return E->getKind() == MCExpr::SymbolRef;
 360   }
 361 };
 362
 363 /// Unary assembler expressions.
 364 class MCUnaryExpr : public MCExpr {
 365 public:
 366   enum Opcode {
 367     LNot,  ///< Logical negation.
 368     Minus, ///< Unary minus.
 369     Not,   ///< Bitwise negation.
 370     Plus   ///< Unary plus.
 371   };
 372
 373 private:
 374   Opcode Op;
 375   const MCExpr *Expr;
 376
 377   MCUnaryExpr(Opcode Op, const MCExpr *Expr, SMLoc Loc)
 378       : MCExpr(MCExpr::Unary, Loc), Op(Op), Expr(Expr) {}
 379
 380 public:
 381   /// \name Construction
 382   /// @{
 383
 384   static const MCUnaryExpr *create(Opcode Op, const MCExpr *Expr,
 385                                    MCContext &Ctx, SMLoc Loc = SMLoc());
 386
 387   static const MCUnaryExpr *createLNot(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 388     return create(LNot, Expr, Ctx, Loc);
 389   }
 390
 391   static const MCUnaryExpr *createMinus(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 392     return create(Minus, Expr, Ctx, Loc);
 393   }
 394
 395   static const MCUnaryExpr *createNot(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 396     return create(Not, Expr, Ctx, Loc);
 397   }
 398
 399   static const MCUnaryExpr *createPlus(const MCExpr *Expr, MCContext &Ctx, SMLoc Loc = SMLoc()) {
 400     return create(Plus, Expr, Ctx, Loc);
 401   }
 402
 403   /// @}
 404   /// \name Accessors
 405   /// @{
 406
 407   /// Get the kind of this unary expression.
 408   Opcode getOpcode() const { return Op; }
 409
 410   /// Get the child of this unary expression.
 411   const MCExpr *getSubExpr() const { return Expr; }
 412
 413   /// @}
 414
 415   static bool classof(const MCExpr *E) {
 416     return E->getKind() == MCExpr::Unary;
 417   }
 418 };
 419
 420 /// Binary assembler expressions.
 421 class MCBinaryExpr : public MCExpr {
 422 public:
 423   enum Opcode {
 424     Add,  ///< Addition.
 425     And,  ///< Bitwise and.
 426     Div,  ///< Signed division.
 427     EQ,   ///< Equality comparison.
 428     GT,   ///< Signed greater than comparison (result is either 0 or some
 429           ///< target-specific non-zero value)
 430     GTE,  ///< Signed greater than or equal comparison (result is either 0 or
 431           ///< some target-specific non-zero value).
 432     LAnd, ///< Logical and.
 433     LOr,  ///< Logical or.
 434     LT,   ///< Signed less than comparison (result is either 0 or
 435           ///< some target-specific non-zero value).
 436     LTE,  ///< Signed less than or equal comparison (result is either 0 or
 437           ///< some target-specific non-zero value).
 438     Mod,  ///< Signed remainder.
 439     Mul,  ///< Multiplication.
 440     NE,   ///< Inequality comparison.
 441     Or,   ///< Bitwise or.
 442     Shl,  ///< Shift left.
 443     AShr, ///< Arithmetic shift right.
 444     LShr, ///< Logical shift right.
 445     Sub,  ///< Subtraction.
 446     Xor   ///< Bitwise exclusive or.
 447   };
 448
 449 private:
 450   Opcode Op;
 451   const MCExpr *LHS, *RHS;
 452
 453   MCBinaryExpr(Opcode Op, const MCExpr *LHS, const MCExpr *RHS,
 454                SMLoc Loc = SMLoc())
 455       : MCExpr(MCExpr::Binary, Loc), Op(Op), LHS(LHS), RHS(RHS) {}
 456
 457 public:
 458   /// \name Construction
 459   /// @{
 460
 461   static const MCBinaryExpr *create(Opcode Op, const MCExpr *LHS,
 462                                     const MCExpr *RHS, MCContext &Ctx,
 463                                     SMLoc Loc = SMLoc());
 464
 465   static const MCBinaryExpr *createAdd(const MCExpr *LHS, const MCExpr *RHS,
 466                                        MCContext &Ctx) {
 467     return create(Add, LHS, RHS, Ctx);
 468   }
 469
 470   static const MCBinaryExpr *createAnd(const MCExpr *LHS, const MCExpr *RHS,
 471                                        MCContext &Ctx) {
 472     return create(And, LHS, RHS, Ctx);
 473   }
 474
 475   static const MCBinaryExpr *createDiv(const MCExpr *LHS, const MCExpr *RHS,
 476                                        MCContext &Ctx) {
 477     return create(Div, LHS, RHS, Ctx);
 478   }
 479
 480   static const MCBinaryExpr *createEQ(const MCExpr *LHS, const MCExpr *RHS,
 481                                       MCContext &Ctx) {
 482     return create(EQ, LHS, RHS, Ctx);
 483   }
 484
 485   static const MCBinaryExpr *createGT(const MCExpr *LHS, const MCExpr *RHS,
 486                                       MCContext &Ctx) {
 487     return create(GT, LHS, RHS, Ctx);
 488   }
 489
 490   static const MCBinaryExpr *createGTE(const MCExpr *LHS, const MCExpr *RHS,
 491                                        MCContext &Ctx) {
 492     return create(GTE, LHS, RHS, Ctx);
 493   }
 494
 495   static const MCBinaryExpr *createLAnd(const MCExpr *LHS, const MCExpr *RHS,
 496                                         MCContext &Ctx) {
 497     return create(LAnd, LHS, RHS, Ctx);
 498   }
 499
 500   static const MCBinaryExpr *createLOr(const MCExpr *LHS, const MCExpr *RHS,
 501                                        MCContext &Ctx) {
 502     return create(LOr, LHS, RHS, Ctx);
 503   }
 504
 505   static const MCBinaryExpr *createLT(const MCExpr *LHS, const MCExpr *RHS,
 506                                       MCContext &Ctx) {
 507     return create(LT, LHS, RHS, Ctx);
 508   }
 509
 510   static const MCBinaryExpr *createLTE(const MCExpr *LHS, const MCExpr *RHS,
 511                                        MCContext &Ctx) {
 512     return create(LTE, LHS, RHS, Ctx);
 513   }
 514
 515   static const MCBinaryExpr *createMod(const MCExpr *LHS, const MCExpr *RHS,
 516                                        MCContext &Ctx) {
 517     return create(Mod, LHS, RHS, Ctx);
 518   }
 519
 520   static const MCBinaryExpr *createMul(const MCExpr *LHS, const MCExpr *RHS,
 521                                        MCContext &Ctx) {
 522     return create(Mul, LHS, RHS, Ctx);
 523   }
 524
 525   static const MCBinaryExpr *createNE(const MCExpr *LHS, const MCExpr *RHS,
 526                                       MCContext &Ctx) {
 527     return create(NE, LHS, RHS, Ctx);
 528   }
 529
 530   static const MCBinaryExpr *createOr(const MCExpr *LHS, const MCExpr *RHS,
 531                                       MCContext &Ctx) {
 532     return create(Or, LHS, RHS, Ctx);
 533   }
 534
 535   static const MCBinaryExpr *createShl(const MCExpr *LHS, const MCExpr *RHS,
 536                                        MCContext &Ctx) {
 537     return create(Shl, LHS, RHS, Ctx);
 538   }
 539
 540   static const MCBinaryExpr *createAShr(const MCExpr *LHS, const MCExpr *RHS,
 541                                        MCContext &Ctx) {
 542     return create(AShr, LHS, RHS, Ctx);
 543   }
 544
 545   static const MCBinaryExpr *createLShr(const MCExpr *LHS, const MCExpr *RHS,
 546                                        MCContext &Ctx) {
 547     return create(LShr, LHS, RHS, Ctx);
 548   }
 549
 550   static const MCBinaryExpr *createSub(const MCExpr *LHS, const MCExpr *RHS,
 551                                        MCContext &Ctx) {
 552     return create(Sub, LHS, RHS, Ctx);
 553   }
 554
 555   static const MCBinaryExpr *createXor(const MCExpr *LHS, const MCExpr *RHS,
 556                                        MCContext &Ctx) {
 557     return create(Xor, LHS, RHS, Ctx);
 558   }
 559
 560   /// @}
 561   /// \name Accessors
 562   /// @{
 563
 564   /// Get the kind of this binary expression.
 565   Opcode getOpcode() const { return Op; }
 566
 567   /// Get the left-hand side expression of the binary operator.
 568   const MCExpr *getLHS() const { return LHS; }
 569
 570   /// Get the right-hand side expression of the binary operator.
 571   const MCExpr *getRHS() const { return RHS; }
 572
 573   /// @}
 574
 575   static bool classof(const MCExpr *E) {
 576     return E->getKind() == MCExpr::Binary;
 577   }
 578 };
 579
 580 /// This is an extension point for target-specific MCExpr subclasses to
 581 /// implement.
 582 ///
 583 /// NOTE: All subclasses are required to have trivial destructors because
 584 /// MCExprs are bump pointer allocated and not destructed.
 585 class MCTargetExpr : public MCExpr {
 586   virtual void anchor();
 587
 588 protected:
 589   MCTargetExpr() : MCExpr(Target, SMLoc()) {}
 590   virtual ~MCTargetExpr() = default;
 591
 592 public:
 593   virtual void printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const = 0;
 594   virtual bool evaluateAsRelocatableImpl(MCValue &Res,
 595                                          const MCAsmLayout *Layout,
 596                                          const MCFixup *Fixup) const = 0;
 597   // allow Target Expressions to be checked for equality
 598   virtual bool isEqualTo(const MCExpr *x) const { return false; }
 599   // This should be set when assigned expressions are not valid ".set"
 600   // expressions, e.g. registers, and must be inlined.
 601   virtual bool inlineAssignedExpr() const { return false; }
 602   virtual void visitUsedExpr(MCStreamer& Streamer) const = 0;
 603   virtual MCFragment *findAssociatedFragment() const = 0;
 604
 605   virtual void fixELFSymbolsInTLSFixups(MCAssembler &) const = 0;
 606
 607   static bool classof(const MCExpr *E) {
 608     return E->getKind() == MCExpr::Target;
 609   }
 610 };
 611
 612 } // end namespace llvm
 613
 614 #endif // LLVM_MC_MCEXPR_H