1 //===-- llvm/Target/TargetLoweringObjectFile.h - Object Info ----*- 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 // This file implements classes used to handle lowerings specific to common
11 // object file formats.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_TARGET_TARGETLOWERINGOBJECTFILE_H
16 #define LLVM_TARGET_TARGETLOWERINGOBJECTFILE_H
17 
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/MC/MCObjectFileInfo.h"
21 #include "llvm/MC/SectionKind.h"
22 
23 namespace llvm {
24   class MachineModuleInfo;
25   class Mangler;
26   class MCContext;
27   class MCExpr;
28   class MCSection;
29   class MCSymbol;
30   class MCSymbolRefExpr;
31   class MCStreamer;
32   class MCValue;
33   class ConstantExpr;
34   class GlobalValue;
35   class TargetMachine;
36 
37 class TargetLoweringObjectFile : public MCObjectFileInfo {
38   MCContext *Ctx;
39 
40   TargetLoweringObjectFile(
41     const TargetLoweringObjectFile&) = delete;
42   void operator=(const TargetLoweringObjectFile&) = delete;
43 
44 protected:
45   bool SupportIndirectSymViaGOTPCRel;
46   bool SupportGOTPCRelWithOffset;
47 
48 public:
getContext()49   MCContext &getContext() const { return *Ctx; }
50 
TargetLoweringObjectFile()51   TargetLoweringObjectFile()
52       : MCObjectFileInfo(), Ctx(nullptr), SupportIndirectSymViaGOTPCRel(false),
53         SupportGOTPCRelWithOffset(true) {}
54 
55   virtual ~TargetLoweringObjectFile();
56 
57   /// This method must be called before any actual lowering is done.  This
58   /// specifies the current context for codegen, and gives the lowering
59   /// implementations a chance to set up their default sections.
60   virtual void Initialize(MCContext &ctx, const TargetMachine &TM);
61 
62   virtual void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &TM,
63                                     const MCSymbol *Sym) const;
64 
65   /// Emit the module flags that the platform cares about.
emitModuleFlags(MCStreamer & Streamer,ArrayRef<Module::ModuleFlagEntry> Flags,Mangler & Mang,const TargetMachine & TM)66   virtual void emitModuleFlags(MCStreamer &Streamer,
67                                ArrayRef<Module::ModuleFlagEntry> Flags,
68                                Mangler &Mang, const TargetMachine &TM) const {}
69 
70   /// Given a constant with the SectionKind, return a section that it should be
71   /// placed in.
72   virtual MCSection *getSectionForConstant(const DataLayout &DL,
73                                            SectionKind Kind,
74                                            const Constant *C,
75                                            unsigned &Align) const;
76 
77   /// Classify the specified global variable into a set of target independent
78   /// categories embodied in SectionKind.
79   static SectionKind getKindForGlobal(const GlobalValue *GV,
80                                       const TargetMachine &TM);
81 
82   /// This method computes the appropriate section to emit the specified global
83   /// variable or function definition. This should not be passed external (or
84   /// available externally) globals.
85   MCSection *SectionForGlobal(const GlobalValue *GV, SectionKind Kind,
86                               Mangler &Mang, const TargetMachine &TM) const;
87 
88   /// This method computes the appropriate section to emit the specified global
89   /// variable or function definition. This should not be passed external (or
90   /// available externally) globals.
SectionForGlobal(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM)91   MCSection *SectionForGlobal(const GlobalValue *GV, Mangler &Mang,
92                               const TargetMachine &TM) const {
93     return SectionForGlobal(GV, getKindForGlobal(GV, TM), Mang, TM);
94   }
95 
96   virtual void getNameWithPrefix(SmallVectorImpl<char> &OutName,
97                                  const GlobalValue *GV, Mangler &Mang,
98                                  const TargetMachine &TM) const;
99 
100   virtual MCSection *getSectionForJumpTable(const Function &F, Mangler &Mang,
101                                             const TargetMachine &TM) const;
102 
103   virtual bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
104                                                    const Function &F) const;
105 
106   /// Targets should implement this method to assign a section to globals with
107   /// an explicit section specfied. The implementation of this method can
108   /// assume that GV->hasSection() is true.
109   virtual MCSection *
110   getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
111                            Mangler &Mang, const TargetMachine &TM) const = 0;
112 
113   /// Allow the target to completely override section assignment of a global.
getSpecialCasedSectionGlobals(const GlobalValue * GV,SectionKind Kind,Mangler & Mang)114   virtual const MCSection *getSpecialCasedSectionGlobals(const GlobalValue *GV,
115                                                          SectionKind Kind,
116                                                          Mangler &Mang) const {
117     return nullptr;
118   }
119 
120   /// Return an MCExpr to use for a reference to the specified global variable
121   /// from exception handling information.
122   virtual const MCExpr *
123   getTTypeGlobalReference(const GlobalValue *GV, unsigned Encoding,
124                           Mangler &Mang, const TargetMachine &TM,
125                           MachineModuleInfo *MMI, MCStreamer &Streamer) const;
126 
127   /// Return the MCSymbol for a private symbol with global value name as its
128   /// base, with the specified suffix.
129   MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
130                                          StringRef Suffix, Mangler &Mang,
131                                          const TargetMachine &TM) const;
132 
133   // The symbol that gets passed to .cfi_personality.
134   virtual MCSymbol *getCFIPersonalitySymbol(const GlobalValue *GV,
135                                             Mangler &Mang,
136                                             const TargetMachine &TM,
137                                             MachineModuleInfo *MMI) const;
138 
139   const MCExpr *
140   getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
141                     MCStreamer &Streamer) const;
142 
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym)143   virtual MCSection *getStaticCtorSection(unsigned Priority,
144                                           const MCSymbol *KeySym) const {
145     return StaticCtorSection;
146   }
147 
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym)148   virtual MCSection *getStaticDtorSection(unsigned Priority,
149                                           const MCSymbol *KeySym) const {
150     return StaticDtorSection;
151   }
152 
153   /// \brief Create a symbol reference to describe the given TLS variable when
154   /// emitting the address in debug info.
155   virtual const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const;
156 
157   virtual const MCExpr *
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,Mangler & Mang,const TargetMachine & TM)158   lowerRelativeReference(const GlobalValue *LHS, const GlobalValue *RHS,
159                          Mangler &Mang, const TargetMachine &TM) const {
160     return nullptr;
161   }
162 
163   /// \brief Target supports replacing a data "PC"-relative access to a symbol
164   /// through another symbol, by accessing the later via a GOT entry instead?
supportIndirectSymViaGOTPCRel()165   bool supportIndirectSymViaGOTPCRel() const {
166     return SupportIndirectSymViaGOTPCRel;
167   }
168 
169   /// \brief Target GOT "PC"-relative relocation supports encoding an additional
170   /// binary expression with an offset?
supportGOTPCRelWithOffset()171   bool supportGOTPCRelWithOffset() const {
172     return SupportGOTPCRelWithOffset;
173   }
174 
175   /// \brief Get the target specific PC relative GOT entry relocation
getIndirectSymViaGOTPCRel(const MCSymbol * Sym,const MCValue & MV,int64_t Offset,MachineModuleInfo * MMI,MCStreamer & Streamer)176   virtual const MCExpr *getIndirectSymViaGOTPCRel(const MCSymbol *Sym,
177                                                   const MCValue &MV,
178                                                   int64_t Offset,
179                                                   MachineModuleInfo *MMI,
180                                                   MCStreamer &Streamer) const {
181     return nullptr;
182   }
183 
emitLinkerFlagsForGlobal(raw_ostream & OS,const GlobalValue * GV,const Mangler & Mang)184   virtual void emitLinkerFlagsForGlobal(raw_ostream &OS, const GlobalValue *GV,
185                                         const Mangler &Mang) const {}
186 
187 protected:
188   virtual MCSection *SelectSectionForGlobal(const GlobalValue *GV,
189                                             SectionKind Kind, Mangler &Mang,
190                                             const TargetMachine &TM) const = 0;
191 };
192 
193 } // end namespace llvm
194 
195 #endif
196