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