MCStreamer.h revision 3924868a957d5a6d468b61741cbb7db77324d1f6 
1//===- MCStreamer.h - High-level Streaming Machine Code Output --*- 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 declares the MCStreamer class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_MC_MCSTREAMER_H
15#define LLVM_MC_MCSTREAMER_H
16
17#include "llvm/System/DataTypes.h"
18
19namespace llvm {
20  class MCAsmInfo;
21  class MCCodeEmitter;
22  class MCContext;
23  class MCExpr;
24  class MCInst;
25  class MCInstPrinter;
26  class MCSection;
27  class MCSymbol;
28  class StringRef;
29  class Twine;
30  class raw_ostream;
31  class formatted_raw_ostream;
32
33  /// MCStreamer - Streaming machine code generation interface.  This interface
34  /// is intended to provide a programatic interface that is very similar to the
35  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
36  /// handle directives, etc.  The implementation of this interface retains
37  /// state to know what the current section is etc.
38  ///
39  /// There are multiple implementations of this interface: one for writing out
40  /// a .s file, and implementations that write out .o files of various formats.
41  ///
42  class MCStreamer {
43  public:
44    enum SymbolAttr {
45      Global,         /// .globl
46      Hidden,         /// .hidden (ELF)
47      IndirectSymbol, /// .indirect_symbol (Apple)
48      Internal,       /// .internal (ELF)
49      LazyReference,  /// .lazy_reference (Apple)
50      Local,          /// .local (ELF)
51      NoDeadStrip,    /// .no_dead_strip (Apple)
52      PrivateExtern,  /// .private_extern (Apple)
53      Protected,      /// .protected (ELF)
54      Reference,      /// .reference (Apple)
55      Weak,           /// .weak
56      WeakDefinition, /// .weak_definition (Apple)
57      WeakReference,  /// .weak_reference (Apple)
58
59      SymbolAttrFirst = Global,
60      SymbolAttrLast = WeakReference
61    };
62
63    enum AssemblerFlag {
64      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
65    };
66
67  private:
68    MCContext &Context;
69
70    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
71    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
72
73  protected:
74    MCStreamer(MCContext &Ctx);
75
76    /// CurSection - This is the current section code is being emitted to, it is
77    /// kept up to date by SwitchSection.
78    const MCSection *CurSection;
79
80  public:
81    virtual ~MCStreamer();
82
83    MCContext &getContext() const { return Context; }
84
85    /// @name Assembly File Formatting.
86    /// @{
87
88    /// AddComment - Add a comment that can be emitted to the generated .s
89    /// file if applicable as a QoI issue to make the output of the compiler
90    /// more readable.  This only affects the MCAsmStreamer, and only when
91    /// verbose assembly output is enabled.
92    ///
93    /// If the comment includes embedded \n's, they will each get the comment
94    /// prefix as appropriate.  The added comment should not end with a \n.
95    virtual void AddComment(const Twine &T) {}
96
97    /// GetCommentOS - Return a raw_ostream that comments can be written to.
98    /// Unlike AddComment, you are required to terminate comments with \n if you
99    /// use this method.
100    virtual raw_ostream &GetCommentOS();
101
102    /// AddBlankLine - Emit a blank line to a .s file to pretty it up.
103    virtual void AddBlankLine() {}
104
105    /// @}
106
107    /// @name Symbol & Section Management
108    /// @{
109
110    /// getCurrentSection - Return the current seciton that the streamer is
111    /// emitting code to.
112    const MCSection *getCurrentSection() const { return CurSection; }
113
114    /// SwitchSection - Set the current section where code is being emitted to
115    /// @param Section.  This is required to update CurSection.
116    ///
117    /// This corresponds to assembler directives like .section, .text, etc.
118    virtual void SwitchSection(const MCSection *Section) = 0;
119
120    /// EmitLabel - Emit a label for @param Symbol into the current section.
121    ///
122    /// This corresponds to an assembler statement such as:
123    ///   foo:
124    ///
125    /// @param Symbol - The symbol to emit. A given symbol should only be
126    /// emitted as a label once, and symbols emitted as a label should never be
127    /// used in an assignment.
128    virtual void EmitLabel(MCSymbol *Symbol) = 0;
129
130    /// EmitAssemblerFlag - Note in the output the specified @param Flag
131    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
132
133    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
134    ///
135    /// This corresponds to an assembler statement such as:
136    ///  symbol = value
137    ///
138    /// The assignment generates no code, but has the side effect of binding the
139    /// value in the current context. For the assembly streamer, this prints the
140    /// binding into the .s file.
141    ///
142    /// @param Symbol - The symbol being assigned to.
143    /// @param Value - The value for the symbol.
144    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) = 0;
145
146    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
147    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
148                                     SymbolAttr Attribute) = 0;
149
150    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
151    ///
152    /// @param Symbol - The symbol to have its n_desc field set.
153    /// @param DescValue - The value to set into the n_desc field.
154    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
155
156    /// EmitCommonSymbol - Emit a common or local common symbol.
157    ///
158    /// @param Symbol - The common symbol to emit.
159    /// @param Size - The size of the common symbol.
160    /// @param ByteAlignment - The alignment of the symbol if
161    /// non-zero. This must be a power of 2 on some targets.
162    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
163                                  unsigned ByteAlignment) = 0;
164
165    /// EmitZerofill - Emit a the zerofill section and an option symbol.
166    ///
167    /// @param Section - The zerofill section to create and or to put the symbol
168    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
169    /// @param Size - The size of the zerofill symbol.
170    /// @param ByteAlignment - The alignment of the zerofill symbol if
171    /// non-zero. This must be a power of 2 on some targets.
172    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
173                              unsigned Size = 0,unsigned ByteAlignment = 0) = 0;
174
175    /// @}
176    /// @name Generating Data
177    /// @{
178
179    /// EmitBytes - Emit the bytes in \arg Data into the output.
180    ///
181    /// This is used to implement assembler directives such as .byte, .ascii,
182    /// etc.
183    virtual void EmitBytes(StringRef Data, unsigned AddrSpace) = 0;
184
185    /// EmitValue - Emit the expression @param Value into the output as a native
186    /// integer of the given @param Size bytes.
187    ///
188    /// This is used to implement assembler directives such as .word, .quad,
189    /// etc.
190    ///
191    /// @param Value - The value to emit.
192    /// @param Size - The size of the integer (in bytes) to emit. This must
193    /// match a native machine width.
194    virtual void EmitValue(const MCExpr *Value, unsigned Size,
195                           unsigned AddrSpace) = 0;
196
197    /// EmitIntValue - Special case of EmitValue that avoids the client having
198    /// to pass in a MCExpr for constant integers.
199    virtual void EmitIntValue(uint64_t Value, unsigned Size,unsigned AddrSpace);
200
201    /// EmitFill - Emit NumBytes bytes worth of the value specified by
202    /// FillValue.  This implements directives such as '.space'.
203    virtual void EmitFill(uint64_t NumBytes, uint8_t FillValue,
204                          unsigned AddrSpace);
205
206    /// EmitZeros - Emit NumBytes worth of zeros.  This is a convenience
207    /// function that just wraps EmitFill.
208    void EmitZeros(uint64_t NumBytes, unsigned AddrSpace) {
209      EmitFill(NumBytes, 0, AddrSpace);
210    }
211
212
213    /// EmitValueToAlignment - Emit some number of copies of @param Value until
214    /// the byte alignment @param ByteAlignment is reached.
215    ///
216    /// If the number of bytes need to emit for the alignment is not a multiple
217    /// of @param ValueSize, then the contents of the emitted fill bytes is
218    /// undefined.
219    ///
220    /// This used to implement the .align assembler directive.
221    ///
222    /// @param ByteAlignment - The alignment to reach. This must be a power of
223    /// two on some targets.
224    /// @param Value - The value to use when filling bytes.
225    /// @param Size - The size of the integer (in bytes) to emit for @param
226    /// Value. This must match a native machine width.
227    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
228    /// the alignment cannot be reached in this many bytes, no bytes are
229    /// emitted.
230    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
231                                      unsigned ValueSize = 1,
232                                      unsigned MaxBytesToEmit = 0) = 0;
233
234    /// EmitValueToOffset - Emit some number of copies of @param Value until the
235    /// byte offset @param Offset is reached.
236    ///
237    /// This is used to implement assembler directives such as .org.
238    ///
239    /// @param Offset - The offset to reach. This may be an expression, but the
240    /// expression must be associated with the current section.
241    /// @param Value - The value to use when filling bytes.
242    virtual void EmitValueToOffset(const MCExpr *Offset,
243                                   unsigned char Value = 0) = 0;
244
245    /// @}
246
247    /// EmitInstruction - Emit the given @param Instruction into the current
248    /// section.
249    virtual void EmitInstruction(const MCInst &Inst) = 0;
250
251    /// Finish - Finish emission of machine code and flush any output.
252    virtual void Finish() = 0;
253  };
254
255  /// createNullStreamer - Create a dummy machine code streamer, which does
256  /// nothing. This is useful for timing the assembler front end.
257  MCStreamer *createNullStreamer(MCContext &Ctx);
258
259  /// createAsmStreamer - Create a machine code streamer which will print out
260  /// assembly for the native target, suitable for compiling with a native
261  /// assembler.
262  MCStreamer *createAsmStreamer(MCContext &Ctx, formatted_raw_ostream &OS,
263                                const MCAsmInfo &MAI, bool isLittleEndian,
264                                bool isVerboseAsm,
265                                MCInstPrinter *InstPrint = 0,
266                                MCCodeEmitter *CE = 0);
267
268  // FIXME: These two may end up getting rolled into a single
269  // createObjectStreamer interface, which implements the assembler backend, and
270  // is parameterized on an output object file writer.
271
272  /// createMachOStream - Create a machine code streamer which will generative
273  /// Mach-O format object files.
274  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS,
275                                  MCCodeEmitter *CE = 0);
276
277  /// createELFStreamer - Create a machine code streamer which will generative
278  /// ELF format object files.
279  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
280
281} // end namespace llvm
282
283#endif
284