1 //===- MCObjectStreamer.h - MCStreamer Object File Interface ----*- 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_MCOBJECTSTREAMER_H
11 #define LLVM_MC_MCOBJECTSTREAMER_H
12 
13 #include "llvm/ADT/SmallVector.h"
14 #include "llvm/MC/MCAssembler.h"
15 #include "llvm/MC/MCSection.h"
16 #include "llvm/MC/MCStreamer.h"
17 
18 namespace llvm {
19 class MCAssembler;
20 class MCCodeEmitter;
21 class MCSubtargetInfo;
22 class MCExpr;
23 class MCFragment;
24 class MCDataFragment;
25 class MCAsmBackend;
26 class raw_ostream;
27 class raw_pwrite_stream;
28 
29 /// \brief Streaming object file generation interface.
30 ///
31 /// This class provides an implementation of the MCStreamer interface which is
32 /// suitable for use with the assembler backend. Specific object file formats
33 /// are expected to subclass this interface to implement directives specific
34 /// to that file format or custom semantics expected by the object writer
35 /// implementation.
36 class MCObjectStreamer : public MCStreamer {
37   MCAssembler *Assembler;
38   MCSection::iterator CurInsertionPoint;
39   bool EmitEHFrame;
40   bool EmitDebugFrame;
41   SmallVector<MCSymbol *, 2> PendingLabels;
42 
43   virtual void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo&) = 0;
44   void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) override;
45   void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) override;
46 
47 protected:
48   MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB, raw_pwrite_stream &OS,
49                    MCCodeEmitter *Emitter);
50   ~MCObjectStreamer() override;
51 
52 public:
53   /// state management
54   void reset() override;
55 
56   /// Object streamers require the integrated assembler.
isIntegratedAssemblerRequired()57   bool isIntegratedAssemblerRequired() const override { return true; }
58 
59   void EmitFrames(MCAsmBackend *MAB);
60   void EmitCFISections(bool EH, bool Debug) override;
61 
62 protected:
63   MCFragment *getCurrentFragment() const;
64 
insert(MCFragment * F)65   void insert(MCFragment *F) {
66     flushPendingLabels(F);
67     MCSection *CurSection = getCurrentSectionOnly();
68     CurSection->getFragmentList().insert(CurInsertionPoint, F);
69     F->setParent(CurSection);
70   }
71 
72   /// Get a data fragment to write into, creating a new one if the current
73   /// fragment is not a data fragment.
74   MCDataFragment *getOrCreateDataFragment();
75 
76   bool changeSectionImpl(MCSection *Section, const MCExpr *Subsection);
77 
78   /// If any labels have been emitted but not assigned fragments, ensure that
79   /// they get assigned, either to F if possible or to a new data fragment.
80   /// Optionally, it is also possible to provide an offset \p FOffset, which
81   /// will be used as a symbol offset within the fragment.
82   void flushPendingLabels(MCFragment *F, uint64_t FOffset = 0);
83 
84 public:
85   void visitUsedSymbol(const MCSymbol &Sym) override;
86 
getAssembler()87   MCAssembler &getAssembler() { return *Assembler; }
88 
89   /// \name MCStreamer Interface
90   /// @{
91 
92   void EmitLabel(MCSymbol *Symbol) override;
93   void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
94   void EmitValueImpl(const MCExpr *Value, unsigned Size,
95                      SMLoc Loc = SMLoc()) override;
96   void EmitULEB128Value(const MCExpr *Value) override;
97   void EmitSLEB128Value(const MCExpr *Value) override;
98   void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) override;
99   void ChangeSection(MCSection *Section, const MCExpr *Subsection) override;
100   void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo& STI) override;
101 
102   /// \brief Emit an instruction to a special fragment, because this instruction
103   /// can change its size during relaxation.
104   virtual void EmitInstToFragment(const MCInst &Inst, const MCSubtargetInfo &);
105 
106   void EmitBundleAlignMode(unsigned AlignPow2) override;
107   void EmitBundleLock(bool AlignToEnd) override;
108   void EmitBundleUnlock() override;
109   void EmitBytes(StringRef Data) override;
110   void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
111                             unsigned ValueSize = 1,
112                             unsigned MaxBytesToEmit = 0) override;
113   void EmitCodeAlignment(unsigned ByteAlignment,
114                          unsigned MaxBytesToEmit = 0) override;
115   void emitValueToOffset(const MCExpr *Offset, unsigned char Value) override;
116   void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
117                              unsigned Column, unsigned Flags,
118                              unsigned Isa, unsigned Discriminator,
119                              StringRef FileName) override;
120   void EmitDwarfAdvanceLineAddr(int64_t LineDelta, const MCSymbol *LastLabel,
121                                 const MCSymbol *Label,
122                                 unsigned PointerSize);
123   void EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
124                                  const MCSymbol *Label);
125   void EmitGPRel32Value(const MCExpr *Value) override;
126   void EmitGPRel64Value(const MCExpr *Value) override;
127   bool EmitRelocDirective(const MCExpr &Offset, StringRef Name,
128                           const MCExpr *Expr, SMLoc Loc) override;
129   void EmitFill(uint64_t NumBytes, uint8_t FillValue) override;
130   void FinishImpl() override;
131 
132   /// Emit the absolute difference between two symbols if possible.
133   ///
134   /// Emit the absolute difference between \c Hi and \c Lo, as long as we can
135   /// compute it.  Currently, that requires that both symbols are in the same
136   /// data fragment.  Otherwise, do nothing and return \c false.
137   ///
138   /// \pre Offset of \c Hi is greater than the offset \c Lo.
139   void emitAbsoluteSymbolDiff(const MCSymbol *Hi, const MCSymbol *Lo,
140                               unsigned Size) override;
141 
142   bool mayHaveInstructions(MCSection &Sec) const override;
143 };
144 
145 } // end namespace llvm
146 
147 #endif
148