1 //===- MCExpr.h - Assembly Level Expressions --------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef LLVM_MC_MCEXPR_H
11 #define LLVM_MC_MCEXPR_H
12 
13 #include "llvm/ADT/DenseMap.h"
14 #include "llvm/Support/Casting.h"
15 #include "llvm/Support/DataTypes.h"
16 
17 namespace llvm {
18 class MCAsmInfo;
19 class MCAsmLayout;
20 class MCAssembler;
21 class MCContext;
22 class MCFixup;
23 class MCSection;
24 class MCSectionData;
25 class MCStreamer;
26 class MCSymbol;
27 class MCValue;
28 class raw_ostream;
29 class StringRef;
30 typedef DenseMap<const MCSectionData*, uint64_t> SectionAddrMap;
31 
32 /// MCExpr - Base class for the full range of assembler expressions which are
33 /// needed for parsing.
34 class MCExpr {
35 public:
36   enum ExprKind {
37     Binary,    ///< Binary expressions.
38     Constant,  ///< Constant expressions.
39     SymbolRef, ///< References to labels and assigned expressions.
40     Unary,     ///< Unary expressions.
41     Target     ///< Target specific expression.
42   };
43 
44 private:
45   ExprKind Kind;
46 
47   MCExpr(const MCExpr&) = delete;
48   void operator=(const MCExpr&) = delete;
49 
50   bool EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
51                           const MCAsmLayout *Layout,
52                           const SectionAddrMap *Addrs) const;
53 
54   bool evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
55                           const MCAsmLayout *Layout,
56                           const SectionAddrMap *Addrs, bool InSet) const;
57 
58 protected:
MCExpr(ExprKind Kind)59   explicit MCExpr(ExprKind Kind) : Kind(Kind) {}
60 
61   bool EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
62                                  const MCAsmLayout *Layout,
63                                  const MCFixup *Fixup,
64                                  const SectionAddrMap *Addrs, bool InSet) const;
65 
66 public:
67   /// @name Accessors
68   /// @{
69 
getKind()70   ExprKind getKind() const { return Kind; }
71 
72   /// @}
73   /// @name Utility Methods
74   /// @{
75 
76   void print(raw_ostream &OS) const;
77   void dump() const;
78 
79   /// @}
80   /// @name Expression Evaluation
81   /// @{
82 
83   /// EvaluateAsAbsolute - 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   /// @result - 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 MCAsmLayout &Layout) const;
95 
96   bool evaluateKnownAbsolute(int64_t &Res, const MCAsmLayout &Layout) const;
97 
98   /// EvaluateAsRelocatable - Try to evaluate the expression to a relocatable
99   /// value, i.e. an expression of the fixed form (a - b + constant).
100   ///
101   /// @param Res - The relocatable value, if evaluation succeeds.
102   /// @param Layout - The assembler layout object to use for evaluating values.
103   /// @param Fixup - The Fixup object if available.
104   /// @result - True on success.
105   bool EvaluateAsRelocatable(MCValue &Res, const MCAsmLayout *Layout,
106                              const MCFixup *Fixup) const;
107 
108   /// \brief Try to evaluate the expression to the form (a - b + constant) where
109   /// neither a nor b are variables.
110   ///
111   /// This is a more aggressive variant of EvaluateAsRelocatable. The intended
112   /// use is for when relocations are not available, like the .size directive.
113   bool evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const;
114 
115   /// FindAssociatedSection - Find the "associated section" for this expression,
116   /// which is currently defined as the absolute section for constants, or
117   /// otherwise the section associated with the first defined symbol in the
118   /// expression.
119   const MCSection *FindAssociatedSection() const;
120 
121   /// @}
122 };
123 
124 inline raw_ostream &operator<<(raw_ostream &OS, const MCExpr &E) {
125   E.print(OS);
126   return OS;
127 }
128 
129 //// MCConstantExpr - Represent a constant integer expression.
130 class MCConstantExpr : public MCExpr {
131   int64_t Value;
132 
MCConstantExpr(int64_t Value)133   explicit MCConstantExpr(int64_t Value)
134       : MCExpr(MCExpr::Constant), Value(Value) {}
135 
136 public:
137   /// @name Construction
138   /// @{
139 
140   static const MCConstantExpr *Create(int64_t Value, MCContext &Ctx);
141 
142   /// @}
143   /// @name Accessors
144   /// @{
145 
getValue()146   int64_t getValue() const { return Value; }
147 
148   /// @}
149 
classof(const MCExpr * E)150   static bool classof(const MCExpr *E) {
151     return E->getKind() == MCExpr::Constant;
152   }
153 };
154 
155 /// MCSymbolRefExpr - Represent a reference to a symbol from inside an
156 /// expression.
157 ///
158 /// A symbol reference in an expression may be a use of a label, a use of an
159 /// assembler variable (defined constant), or constitute an implicit definition
160 /// of the symbol as external.
161 class MCSymbolRefExpr : public MCExpr {
162 public:
163   enum VariantKind {
164     VK_None,
165     VK_Invalid,
166 
167     VK_GOT,
168     VK_GOTOFF,
169     VK_GOTPCREL,
170     VK_GOTTPOFF,
171     VK_INDNTPOFF,
172     VK_NTPOFF,
173     VK_GOTNTPOFF,
174     VK_PLT,
175     VK_TLSGD,
176     VK_TLSLD,
177     VK_TLSLDM,
178     VK_TPOFF,
179     VK_DTPOFF,
180     VK_TLVP,      // Mach-O thread local variable relocations
181     VK_TLVPPAGE,
182     VK_TLVPPAGEOFF,
183     VK_PAGE,
184     VK_PAGEOFF,
185     VK_GOTPAGE,
186     VK_GOTPAGEOFF,
187     VK_SECREL,
188     VK_SIZE,      // symbol@SIZE
189     VK_WEAKREF,   // The link between the symbols in .weakref foo, bar
190 
191     VK_ARM_NONE,
192     VK_ARM_TARGET1,
193     VK_ARM_TARGET2,
194     VK_ARM_PREL31,
195     VK_ARM_SBREL,          // symbol(sbrel)
196     VK_ARM_TLSLDO,         // symbol(tlsldo)
197     VK_ARM_TLSCALL,        // symbol(tlscall)
198     VK_ARM_TLSDESC,        // symbol(tlsdesc)
199     VK_ARM_TLSDESCSEQ,
200 
201     VK_PPC_LO,             // symbol@l
202     VK_PPC_HI,             // symbol@h
203     VK_PPC_HA,             // symbol@ha
204     VK_PPC_HIGHER,         // symbol@higher
205     VK_PPC_HIGHERA,        // symbol@highera
206     VK_PPC_HIGHEST,        // symbol@highest
207     VK_PPC_HIGHESTA,       // symbol@highesta
208     VK_PPC_GOT_LO,         // symbol@got@l
209     VK_PPC_GOT_HI,         // symbol@got@h
210     VK_PPC_GOT_HA,         // symbol@got@ha
211     VK_PPC_TOCBASE,        // symbol@tocbase
212     VK_PPC_TOC,            // symbol@toc
213     VK_PPC_TOC_LO,         // symbol@toc@l
214     VK_PPC_TOC_HI,         // symbol@toc@h
215     VK_PPC_TOC_HA,         // symbol@toc@ha
216     VK_PPC_DTPMOD,         // symbol@dtpmod
217     VK_PPC_TPREL,          // symbol@tprel
218     VK_PPC_TPREL_LO,       // symbol@tprel@l
219     VK_PPC_TPREL_HI,       // symbol@tprel@h
220     VK_PPC_TPREL_HA,       // symbol@tprel@ha
221     VK_PPC_TPREL_HIGHER,   // symbol@tprel@higher
222     VK_PPC_TPREL_HIGHERA,  // symbol@tprel@highera
223     VK_PPC_TPREL_HIGHEST,  // symbol@tprel@highest
224     VK_PPC_TPREL_HIGHESTA, // symbol@tprel@highesta
225     VK_PPC_DTPREL,         // symbol@dtprel
226     VK_PPC_DTPREL_LO,      // symbol@dtprel@l
227     VK_PPC_DTPREL_HI,      // symbol@dtprel@h
228     VK_PPC_DTPREL_HA,      // symbol@dtprel@ha
229     VK_PPC_DTPREL_HIGHER,  // symbol@dtprel@higher
230     VK_PPC_DTPREL_HIGHERA, // symbol@dtprel@highera
231     VK_PPC_DTPREL_HIGHEST, // symbol@dtprel@highest
232     VK_PPC_DTPREL_HIGHESTA,// symbol@dtprel@highesta
233     VK_PPC_GOT_TPREL,      // symbol@got@tprel
234     VK_PPC_GOT_TPREL_LO,   // symbol@got@tprel@l
235     VK_PPC_GOT_TPREL_HI,   // symbol@got@tprel@h
236     VK_PPC_GOT_TPREL_HA,   // symbol@got@tprel@ha
237     VK_PPC_GOT_DTPREL,     // symbol@got@dtprel
238     VK_PPC_GOT_DTPREL_LO,  // symbol@got@dtprel@l
239     VK_PPC_GOT_DTPREL_HI,  // symbol@got@dtprel@h
240     VK_PPC_GOT_DTPREL_HA,  // symbol@got@dtprel@ha
241     VK_PPC_TLS,            // symbol@tls
242     VK_PPC_GOT_TLSGD,      // symbol@got@tlsgd
243     VK_PPC_GOT_TLSGD_LO,   // symbol@got@tlsgd@l
244     VK_PPC_GOT_TLSGD_HI,   // symbol@got@tlsgd@h
245     VK_PPC_GOT_TLSGD_HA,   // symbol@got@tlsgd@ha
246     VK_PPC_TLSGD,          // symbol@tlsgd
247     VK_PPC_GOT_TLSLD,      // symbol@got@tlsld
248     VK_PPC_GOT_TLSLD_LO,   // symbol@got@tlsld@l
249     VK_PPC_GOT_TLSLD_HI,   // symbol@got@tlsld@h
250     VK_PPC_GOT_TLSLD_HA,   // symbol@got@tlsld@ha
251     VK_PPC_TLSLD,          // symbol@tlsld
252     VK_PPC_LOCAL,          // symbol@local
253 
254     VK_Mips_GPREL,
255     VK_Mips_GOT_CALL,
256     VK_Mips_GOT16,
257     VK_Mips_GOT,
258     VK_Mips_ABS_HI,
259     VK_Mips_ABS_LO,
260     VK_Mips_TLSGD,
261     VK_Mips_TLSLDM,
262     VK_Mips_DTPREL_HI,
263     VK_Mips_DTPREL_LO,
264     VK_Mips_GOTTPREL,
265     VK_Mips_TPREL_HI,
266     VK_Mips_TPREL_LO,
267     VK_Mips_GPOFF_HI,
268     VK_Mips_GPOFF_LO,
269     VK_Mips_GOT_DISP,
270     VK_Mips_GOT_PAGE,
271     VK_Mips_GOT_OFST,
272     VK_Mips_HIGHER,
273     VK_Mips_HIGHEST,
274     VK_Mips_GOT_HI16,
275     VK_Mips_GOT_LO16,
276     VK_Mips_CALL_HI16,
277     VK_Mips_CALL_LO16,
278     VK_Mips_PCREL_HI16,
279     VK_Mips_PCREL_LO16,
280 
281     VK_COFF_IMGREL32 // symbol@imgrel (image-relative)
282   };
283 
284 private:
285   /// The symbol reference modifier.
286   const unsigned Kind : 16;
287 
288   /// Specifies how the variant kind should be printed.
289   const unsigned UseParensForSymbolVariant : 1;
290 
291   // FIXME: Remove this bit.
292   const unsigned HasSubsectionsViaSymbols : 1;
293 
294   /// The symbol being referenced.
295   const MCSymbol *Symbol;
296 
297   explicit MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
298                            const MCAsmInfo *MAI);
299 
300 public:
301   /// @name Construction
302   /// @{
303 
Create(const MCSymbol * Symbol,MCContext & Ctx)304   static const MCSymbolRefExpr *Create(const MCSymbol *Symbol, MCContext &Ctx) {
305     return MCSymbolRefExpr::Create(Symbol, VK_None, Ctx);
306   }
307 
308   static const MCSymbolRefExpr *Create(const MCSymbol *Symbol, VariantKind Kind,
309                                        MCContext &Ctx);
310   static const MCSymbolRefExpr *Create(StringRef Name, VariantKind Kind,
311                                        MCContext &Ctx);
312 
313   /// @}
314   /// @name Accessors
315   /// @{
316 
getSymbol()317   const MCSymbol &getSymbol() const { return *Symbol; }
318 
getKind()319   VariantKind getKind() const { return static_cast<VariantKind>(Kind); }
320 
321   void printVariantKind(raw_ostream &OS) const;
322 
hasSubsectionsViaSymbols()323   bool hasSubsectionsViaSymbols() const { return HasSubsectionsViaSymbols; }
324 
325   /// @}
326   /// @name Static Utility Functions
327   /// @{
328 
329   static StringRef getVariantKindName(VariantKind Kind);
330 
331   static VariantKind getVariantKindForName(StringRef Name);
332 
333   /// @}
334 
classof(const MCExpr * E)335   static bool classof(const MCExpr *E) {
336     return E->getKind() == MCExpr::SymbolRef;
337   }
338 };
339 
340 /// MCUnaryExpr - Unary assembler expressions.
341 class MCUnaryExpr : public MCExpr {
342 public:
343   enum Opcode {
344     LNot,  ///< Logical negation.
345     Minus, ///< Unary minus.
346     Not,   ///< Bitwise negation.
347     Plus   ///< Unary plus.
348   };
349 
350 private:
351   Opcode Op;
352   const MCExpr *Expr;
353 
MCUnaryExpr(Opcode Op,const MCExpr * Expr)354   MCUnaryExpr(Opcode Op, const MCExpr *Expr)
355       : MCExpr(MCExpr::Unary), Op(Op), Expr(Expr) {}
356 
357 public:
358   /// @name Construction
359   /// @{
360 
361   static const MCUnaryExpr *Create(Opcode Op, const MCExpr *Expr,
362                                    MCContext &Ctx);
CreateLNot(const MCExpr * Expr,MCContext & Ctx)363   static const MCUnaryExpr *CreateLNot(const MCExpr *Expr, MCContext &Ctx) {
364     return Create(LNot, Expr, Ctx);
365   }
CreateMinus(const MCExpr * Expr,MCContext & Ctx)366   static const MCUnaryExpr *CreateMinus(const MCExpr *Expr, MCContext &Ctx) {
367     return Create(Minus, Expr, Ctx);
368   }
CreateNot(const MCExpr * Expr,MCContext & Ctx)369   static const MCUnaryExpr *CreateNot(const MCExpr *Expr, MCContext &Ctx) {
370     return Create(Not, Expr, Ctx);
371   }
CreatePlus(const MCExpr * Expr,MCContext & Ctx)372   static const MCUnaryExpr *CreatePlus(const MCExpr *Expr, MCContext &Ctx) {
373     return Create(Plus, Expr, Ctx);
374   }
375 
376   /// @}
377   /// @name Accessors
378   /// @{
379 
380   /// getOpcode - Get the kind of this unary expression.
getOpcode()381   Opcode getOpcode() const { return Op; }
382 
383   /// getSubExpr - Get the child of this unary expression.
getSubExpr()384   const MCExpr *getSubExpr() const { return Expr; }
385 
386   /// @}
387 
classof(const MCExpr * E)388   static bool classof(const MCExpr *E) {
389     return E->getKind() == MCExpr::Unary;
390   }
391 };
392 
393 /// MCBinaryExpr - Binary assembler expressions.
394 class MCBinaryExpr : public MCExpr {
395 public:
396   enum Opcode {
397     Add,  ///< Addition.
398     And,  ///< Bitwise and.
399     Div,  ///< Signed division.
400     EQ,   ///< Equality comparison.
401     GT,   ///< Signed greater than comparison (result is either 0 or some
402           ///< target-specific non-zero value)
403     GTE,  ///< Signed greater than or equal comparison (result is either 0 or
404           ///< some target-specific non-zero value).
405     LAnd, ///< Logical and.
406     LOr,  ///< Logical or.
407     LT,   ///< Signed less than comparison (result is either 0 or
408           ///< some target-specific non-zero value).
409     LTE,  ///< Signed less than or equal comparison (result is either 0 or
410           ///< some target-specific non-zero value).
411     Mod,  ///< Signed remainder.
412     Mul,  ///< Multiplication.
413     NE,   ///< Inequality comparison.
414     Or,   ///< Bitwise or.
415     Shl,  ///< Shift left.
416     Shr,  ///< Shift right (arithmetic or logical, depending on target)
417     Sub,  ///< Subtraction.
418     Xor   ///< Bitwise exclusive or.
419   };
420 
421 private:
422   Opcode Op;
423   const MCExpr *LHS, *RHS;
424 
MCBinaryExpr(Opcode Op,const MCExpr * LHS,const MCExpr * RHS)425   MCBinaryExpr(Opcode Op, const MCExpr *LHS, const MCExpr *RHS)
426       : MCExpr(MCExpr::Binary), Op(Op), LHS(LHS), RHS(RHS) {}
427 
428 public:
429   /// @name Construction
430   /// @{
431 
432   static const MCBinaryExpr *Create(Opcode Op, const MCExpr *LHS,
433                                     const MCExpr *RHS, MCContext &Ctx);
CreateAdd(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)434   static const MCBinaryExpr *CreateAdd(const MCExpr *LHS, const MCExpr *RHS,
435                                        MCContext &Ctx) {
436     return Create(Add, LHS, RHS, Ctx);
437   }
CreateAnd(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)438   static const MCBinaryExpr *CreateAnd(const MCExpr *LHS, const MCExpr *RHS,
439                                        MCContext &Ctx) {
440     return Create(And, LHS, RHS, Ctx);
441   }
CreateDiv(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)442   static const MCBinaryExpr *CreateDiv(const MCExpr *LHS, const MCExpr *RHS,
443                                        MCContext &Ctx) {
444     return Create(Div, LHS, RHS, Ctx);
445   }
CreateEQ(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)446   static const MCBinaryExpr *CreateEQ(const MCExpr *LHS, const MCExpr *RHS,
447                                       MCContext &Ctx) {
448     return Create(EQ, LHS, RHS, Ctx);
449   }
CreateGT(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)450   static const MCBinaryExpr *CreateGT(const MCExpr *LHS, const MCExpr *RHS,
451                                       MCContext &Ctx) {
452     return Create(GT, LHS, RHS, Ctx);
453   }
CreateGTE(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)454   static const MCBinaryExpr *CreateGTE(const MCExpr *LHS, const MCExpr *RHS,
455                                        MCContext &Ctx) {
456     return Create(GTE, LHS, RHS, Ctx);
457   }
CreateLAnd(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)458   static const MCBinaryExpr *CreateLAnd(const MCExpr *LHS, const MCExpr *RHS,
459                                         MCContext &Ctx) {
460     return Create(LAnd, LHS, RHS, Ctx);
461   }
CreateLOr(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)462   static const MCBinaryExpr *CreateLOr(const MCExpr *LHS, const MCExpr *RHS,
463                                        MCContext &Ctx) {
464     return Create(LOr, LHS, RHS, Ctx);
465   }
CreateLT(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)466   static const MCBinaryExpr *CreateLT(const MCExpr *LHS, const MCExpr *RHS,
467                                       MCContext &Ctx) {
468     return Create(LT, LHS, RHS, Ctx);
469   }
CreateLTE(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)470   static const MCBinaryExpr *CreateLTE(const MCExpr *LHS, const MCExpr *RHS,
471                                        MCContext &Ctx) {
472     return Create(LTE, LHS, RHS, Ctx);
473   }
CreateMod(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)474   static const MCBinaryExpr *CreateMod(const MCExpr *LHS, const MCExpr *RHS,
475                                        MCContext &Ctx) {
476     return Create(Mod, LHS, RHS, Ctx);
477   }
CreateMul(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)478   static const MCBinaryExpr *CreateMul(const MCExpr *LHS, const MCExpr *RHS,
479                                        MCContext &Ctx) {
480     return Create(Mul, LHS, RHS, Ctx);
481   }
CreateNE(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)482   static const MCBinaryExpr *CreateNE(const MCExpr *LHS, const MCExpr *RHS,
483                                       MCContext &Ctx) {
484     return Create(NE, LHS, RHS, Ctx);
485   }
CreateOr(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)486   static const MCBinaryExpr *CreateOr(const MCExpr *LHS, const MCExpr *RHS,
487                                       MCContext &Ctx) {
488     return Create(Or, LHS, RHS, Ctx);
489   }
CreateShl(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)490   static const MCBinaryExpr *CreateShl(const MCExpr *LHS, const MCExpr *RHS,
491                                        MCContext &Ctx) {
492     return Create(Shl, LHS, RHS, Ctx);
493   }
CreateShr(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)494   static const MCBinaryExpr *CreateShr(const MCExpr *LHS, const MCExpr *RHS,
495                                        MCContext &Ctx) {
496     return Create(Shr, LHS, RHS, Ctx);
497   }
CreateSub(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)498   static const MCBinaryExpr *CreateSub(const MCExpr *LHS, const MCExpr *RHS,
499                                        MCContext &Ctx) {
500     return Create(Sub, LHS, RHS, Ctx);
501   }
CreateXor(const MCExpr * LHS,const MCExpr * RHS,MCContext & Ctx)502   static const MCBinaryExpr *CreateXor(const MCExpr *LHS, const MCExpr *RHS,
503                                        MCContext &Ctx) {
504     return Create(Xor, LHS, RHS, Ctx);
505   }
506 
507   /// @}
508   /// @name Accessors
509   /// @{
510 
511   /// getOpcode - Get the kind of this binary expression.
getOpcode()512   Opcode getOpcode() const { return Op; }
513 
514   /// getLHS - Get the left-hand side expression of the binary operator.
getLHS()515   const MCExpr *getLHS() const { return LHS; }
516 
517   /// getRHS - Get the right-hand side expression of the binary operator.
getRHS()518   const MCExpr *getRHS() const { return RHS; }
519 
520   /// @}
521 
classof(const MCExpr * E)522   static bool classof(const MCExpr *E) {
523     return E->getKind() == MCExpr::Binary;
524   }
525 };
526 
527 /// MCTargetExpr - This is an extension point for target-specific MCExpr
528 /// subclasses to implement.
529 ///
530 /// NOTE: All subclasses are required to have trivial destructors because
531 /// MCExprs are bump pointer allocated and not destructed.
532 class MCTargetExpr : public MCExpr {
533   virtual void anchor();
534 protected:
MCTargetExpr()535   MCTargetExpr() : MCExpr(Target) {}
~MCTargetExpr()536   virtual ~MCTargetExpr() {}
537 public:
538 
539   virtual void PrintImpl(raw_ostream &OS) const = 0;
540   virtual bool EvaluateAsRelocatableImpl(MCValue &Res,
541                                          const MCAsmLayout *Layout,
542                                          const MCFixup *Fixup) const = 0;
543   virtual void visitUsedExpr(MCStreamer& Streamer) const = 0;
544   virtual const MCSection *FindAssociatedSection() const = 0;
545 
546   virtual void fixELFSymbolsInTLSFixups(MCAssembler &) const = 0;
547 
classof(const MCExpr * E)548   static bool classof(const MCExpr *E) {
549     return E->getKind() == MCExpr::Target;
550   }
551 };
552 
553 } // end namespace llvm
554 
555 #endif
556