MCStreamer.h revision a6594fc7156c0afbe6fd5a6aab9b099aaf950c53 
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#include "llvm/MC/MCDirectives.h"
19
20namespace llvm {
21  class MCAsmInfo;
22  class MCCodeEmitter;
23  class MCContext;
24  class MCExpr;
25  class MCInst;
26  class MCInstPrinter;
27  class MCSection;
28  class MCSymbol;
29  class StringRef;
30  class Twine;
31  class raw_ostream;
32  class formatted_raw_ostream;
33
34  /// MCStreamer - Streaming machine code generation interface.  This interface
35  /// is intended to provide a programatic interface that is very similar to the
36  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
37  /// handle directives, etc.  The implementation of this interface retains
38  /// state to know what the current section is etc.
39  ///
40  /// There are multiple implementations of this interface: one for writing out
41  /// a .s file, and implementations that write out .o files of various formats.
42  ///
43  class MCStreamer {
44    MCContext &Context;
45
46    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
47    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
48
49  protected:
50    MCStreamer(MCContext &Ctx);
51
52    /// CurSection - This is the current section code is being emitted to, it is
53    /// kept up to date by SwitchSection.
54    const MCSection *CurSection;
55
56  public:
57    virtual ~MCStreamer();
58
59    MCContext &getContext() const { return Context; }
60
61    /// @name Assembly File Formatting.
62    /// @{
63
64    /// AddComment - Add a comment that can be emitted to the generated .s
65    /// file if applicable as a QoI issue to make the output of the compiler
66    /// more readable.  This only affects the MCAsmStreamer, and only when
67    /// verbose assembly output is enabled.
68    ///
69    /// If the comment includes embedded \n's, they will each get the comment
70    /// prefix as appropriate.  The added comment should not end with a \n.
71    virtual void AddComment(const Twine &T) {}
72
73    /// GetCommentOS - Return a raw_ostream that comments can be written to.
74    /// Unlike AddComment, you are required to terminate comments with \n if you
75    /// use this method.
76    virtual raw_ostream &GetCommentOS();
77
78    /// AddBlankLine - Emit a blank line to a .s file to pretty it up.
79    virtual void AddBlankLine() {}
80
81    /// @}
82
83    /// @name Symbol & Section Management
84    /// @{
85
86    /// getCurrentSection - Return the current seciton that the streamer is
87    /// emitting code to.
88    const MCSection *getCurrentSection() const { return CurSection; }
89
90    /// SwitchSection - Set the current section where code is being emitted to
91    /// @param Section.  This is required to update CurSection.
92    ///
93    /// This corresponds to assembler directives like .section, .text, etc.
94    virtual void SwitchSection(const MCSection *Section) = 0;
95
96    /// EmitLabel - Emit a label for @param Symbol into the current section.
97    ///
98    /// This corresponds to an assembler statement such as:
99    ///   foo:
100    ///
101    /// @param Symbol - The symbol to emit. A given symbol should only be
102    /// emitted as a label once, and symbols emitted as a label should never be
103    /// used in an assignment.
104    virtual void EmitLabel(MCSymbol *Symbol) = 0;
105
106    /// EmitAssemblerFlag - Note in the output the specified @param Flag
107    virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) = 0;
108
109    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
110    ///
111    /// This corresponds to an assembler statement such as:
112    ///  symbol = value
113    ///
114    /// The assignment generates no code, but has the side effect of binding the
115    /// value in the current context. For the assembly streamer, this prints the
116    /// binding into the .s file.
117    ///
118    /// @param Symbol - The symbol being assigned to.
119    /// @param Value - The value for the symbol.
120    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) = 0;
121
122    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
123    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
124                                     MCSymbolAttr Attribute) = 0;
125
126    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
127    ///
128    /// @param Symbol - The symbol to have its n_desc field set.
129    /// @param DescValue - The value to set into the n_desc field.
130    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
131
132
133    /// EmitELFSize - Emit an ELF .size directive.
134    ///
135    /// This corresponds to an assembler statement such as:
136    ///  .size symbol, expression
137    ///
138    virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) = 0;
139
140    /// EmitCommonSymbol - Emit a common symbol.
141    ///
142    /// @param Symbol - The common symbol to emit.
143    /// @param Size - The size of the common symbol.
144    /// @param ByteAlignment - The alignment of the symbol if
145    /// non-zero. This must be a power of 2.
146    virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
147                                  unsigned ByteAlignment) = 0;
148
149    /// EmitLocalCommonSymbol - Emit a local common (.lcomm) symbol.
150    ///
151    /// @param Symbol - The common symbol to emit.
152    /// @param Size - The size of the common symbol.
153    virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) = 0;
154
155    /// EmitZerofill - Emit a the zerofill section and an option symbol.
156    ///
157    /// @param Section - The zerofill section to create and or to put the symbol
158    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
159    /// @param Size - The size of the zerofill symbol.
160    /// @param ByteAlignment - The alignment of the zerofill symbol if
161    /// non-zero. This must be a power of 2 on some targets.
162    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
163                              unsigned Size = 0,unsigned ByteAlignment = 0) = 0;
164
165    /// @}
166    /// @name Generating Data
167    /// @{
168
169    /// EmitBytes - Emit the bytes in \arg Data into the output.
170    ///
171    /// This is used to implement assembler directives such as .byte, .ascii,
172    /// etc.
173    virtual void EmitBytes(StringRef Data, unsigned AddrSpace) = 0;
174
175    /// EmitValue - Emit the expression @param Value into the output as a native
176    /// integer of the given @param Size bytes.
177    ///
178    /// This is used to implement assembler directives such as .word, .quad,
179    /// etc.
180    ///
181    /// @param Value - The value to emit.
182    /// @param Size - The size of the integer (in bytes) to emit. This must
183    /// match a native machine width.
184    virtual void EmitValue(const MCExpr *Value, unsigned Size,
185                           unsigned AddrSpace) = 0;
186
187    /// EmitIntValue - Special case of EmitValue that avoids the client having
188    /// to pass in a MCExpr for constant integers.
189    virtual void EmitIntValue(uint64_t Value, unsigned Size,unsigned AddrSpace);
190
191    /// EmitFill - Emit NumBytes bytes worth of the value specified by
192    /// FillValue.  This implements directives such as '.space'.
193    virtual void EmitFill(uint64_t NumBytes, uint8_t FillValue,
194                          unsigned AddrSpace);
195
196    /// EmitZeros - Emit NumBytes worth of zeros.  This is a convenience
197    /// function that just wraps EmitFill.
198    void EmitZeros(uint64_t NumBytes, unsigned AddrSpace) {
199      EmitFill(NumBytes, 0, AddrSpace);
200    }
201
202
203    /// EmitValueToAlignment - Emit some number of copies of @param Value until
204    /// the byte alignment @param ByteAlignment is reached.
205    ///
206    /// If the number of bytes need to emit for the alignment is not a multiple
207    /// of @param ValueSize, then the contents of the emitted fill bytes is
208    /// undefined.
209    ///
210    /// This used to implement the .align assembler directive.
211    ///
212    /// @param ByteAlignment - The alignment to reach. This must be a power of
213    /// two on some targets.
214    /// @param Value - The value to use when filling bytes.
215    /// @param Size - The size of the integer (in bytes) to emit for @param
216    /// Value. This must match a native machine width.
217    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
218    /// the alignment cannot be reached in this many bytes, no bytes are
219    /// emitted.
220    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
221                                      unsigned ValueSize = 1,
222                                      unsigned MaxBytesToEmit = 0) = 0;
223
224    /// EmitValueToOffset - Emit some number of copies of @param Value until the
225    /// byte offset @param Offset is reached.
226    ///
227    /// This is used to implement assembler directives such as .org.
228    ///
229    /// @param Offset - The offset to reach. This may be an expression, but the
230    /// expression must be associated with the current section.
231    /// @param Value - The value to use when filling bytes.
232    virtual void EmitValueToOffset(const MCExpr *Offset,
233                                   unsigned char Value = 0) = 0;
234
235    /// @}
236
237    /// EmitFileDirective - Switch to a new logical file.  This is used to
238    /// implement the '.file "foo.c"' assembler directive.
239    virtual void EmitFileDirective(StringRef Filename) = 0;
240
241    /// EmitDwarfFileDirective - Associate a filename with a specified logical
242    /// file number.  This implements the DWARF2 '.file 4 "foo.c"' assembler
243    /// directive.
244    virtual void EmitDwarfFileDirective(unsigned FileNo,StringRef Filename) = 0;
245
246    /// EmitInstruction - Emit the given @param Instruction into the current
247    /// section.
248    virtual void EmitInstruction(const MCInst &Inst) = 0;
249
250    /// Finish - Finish emission of machine code and flush any output.
251    virtual void Finish() = 0;
252  };
253
254  /// createNullStreamer - Create a dummy machine code streamer, which does
255  /// nothing. This is useful for timing the assembler front end.
256  MCStreamer *createNullStreamer(MCContext &Ctx);
257
258  /// createAsmStreamer - Create a machine code streamer which will print out
259  /// assembly for the native target, suitable for compiling with a native
260  /// assembler.
261  MCStreamer *createAsmStreamer(MCContext &Ctx, formatted_raw_ostream &OS,
262                                const MCAsmInfo &MAI, bool isLittleEndian,
263                                bool isVerboseAsm,
264                                MCInstPrinter *InstPrint = 0,
265                                MCCodeEmitter *CE = 0);
266
267  // FIXME: These two may end up getting rolled into a single
268  // createObjectStreamer interface, which implements the assembler backend, and
269  // is parameterized on an output object file writer.
270
271  /// createMachOStream - Create a machine code streamer which will generative
272  /// Mach-O format object files.
273  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS,
274                                  MCCodeEmitter *CE = 0);
275
276  /// createELFStreamer - Create a machine code streamer which will generative
277  /// ELF format object files.
278  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
279
280} // end namespace llvm
281
282#endif
283