MCStreamer.h revision d79d9dce47d505369662ae5111dba24f9ccdef68 
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      NoDeadStrip,    /// .no_dead_strip (Apple)
51      PrivateExtern,  /// .private_extern (Apple)
52      Protected,      /// .protected (ELF)
53      Reference,      /// .reference (Apple)
54      Weak,           /// .weak
55      WeakDefinition, /// .weak_definition (Apple)
56      WeakReference,  /// .weak_reference (Apple)
57
58      SymbolAttrFirst = Global,
59      SymbolAttrLast = WeakReference
60    };
61
62    enum AssemblerFlag {
63      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
64    };
65
66  private:
67    MCContext &Context;
68
69    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
70    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
71
72  protected:
73    MCStreamer(MCContext &Ctx);
74
75    /// CurSection - This is the current section code is being emitted to, it is
76    /// kept up to date by SwitchSection.
77    const MCSection *CurSection;
78
79  public:
80    virtual ~MCStreamer();
81
82    MCContext &getContext() const { return Context; }
83
84    /// AddComment - Add a comment that can be emitted to the generated .s
85    /// file if applicable as a QoI issue to make the output of the compiler
86    /// more readable.  This only affects the MCAsmStreamer, and only when
87    /// verbose assembly output is enabled.
88    ///
89    /// If the comment includes embedded \n's, they will each get the comment
90    /// prefix as appropriate.  The added comment should not end with a \n.
91    virtual void AddComment(const Twine &T) {}
92
93    /// GetCommentOS - Return a raw_ostream that comments can be written to.
94    /// Unlike AddComment, you are required to terminate comments with \n if you
95    /// use this method.
96    virtual raw_ostream &GetCommentOS();
97
98    /// @name Symbol & Section Management
99    /// @{
100
101    /// getCurrentSection - Return the current seciton that the streamer is
102    /// emitting code to.
103    const MCSection *getCurrentSection() const { return CurSection; }
104
105    /// SwitchSection - Set the current section where code is being emitted to
106    /// @param Section.  This is required to update CurSection.
107    ///
108    /// This corresponds to assembler directives like .section, .text, etc.
109    virtual void SwitchSection(const MCSection *Section) = 0;
110
111    /// EmitLabel - Emit a label for @param Symbol into the current section.
112    ///
113    /// This corresponds to an assembler statement such as:
114    ///   foo:
115    ///
116    /// @param Symbol - The symbol to emit. A given symbol should only be
117    /// emitted as a label once, and symbols emitted as a label should never be
118    /// used in an assignment.
119    virtual void EmitLabel(MCSymbol *Symbol) = 0;
120
121    /// EmitAssemblerFlag - Note in the output the specified @param Flag
122    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
123
124    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
125    ///
126    /// This corresponds to an assembler statement such as:
127    ///  symbol = value
128    ///
129    /// The assignment generates no code, but has the side effect of binding the
130    /// value in the current context. For the assembly streamer, this prints the
131    /// binding into the .s file.
132    ///
133    /// @param Symbol - The symbol being assigned to.
134    /// @param Value - The value for the symbol.
135    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) = 0;
136
137    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
138    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
139                                     SymbolAttr Attribute) = 0;
140
141    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
142    ///
143    /// @param Symbol - The symbol to have its n_desc field set.
144    /// @param DescValue - The value to set into the n_desc field.
145    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
146
147    /// EmitCommonSymbol - Emit a common or local common symbol.
148    ///
149    /// @param Symbol - The common symbol to emit.
150    /// @param Size - The size of the common symbol.
151    /// @param ByteAlignment - The alignment of the symbol if
152    /// non-zero. This must be a power of 2 on some targets.
153    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
154                                  unsigned ByteAlignment) = 0;
155
156    /// EmitZerofill - Emit a the zerofill section and an option symbol.
157    ///
158    /// @param Section - The zerofill section to create and or to put the symbol
159    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
160    /// @param Size - The size of the zerofill symbol.
161    /// @param ByteAlignment - The alignment of the zerofill symbol if
162    /// non-zero. This must be a power of 2 on some targets.
163    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
164                              unsigned Size = 0,unsigned ByteAlignment = 0) = 0;
165
166    /// @}
167    /// @name Generating Data
168    /// @{
169
170    /// EmitBytes - Emit the bytes in \arg Data into the output.
171    ///
172    /// This is used to implement assembler directives such as .byte, .ascii,
173    /// etc.
174    virtual void EmitBytes(StringRef Data, unsigned AddrSpace) = 0;
175
176    /// EmitValue - Emit the expression @param Value into the output as a native
177    /// integer of the given @param Size bytes.
178    ///
179    /// This is used to implement assembler directives such as .word, .quad,
180    /// etc.
181    ///
182    /// @param Value - The value to emit.
183    /// @param Size - The size of the integer (in bytes) to emit. This must
184    /// match a native machine width.
185    virtual void EmitValue(const MCExpr *Value, unsigned Size,
186                           unsigned AddrSpace) = 0;
187
188    /// EmitIntValue - Special case of EmitValue that avoids the client having
189    /// to pass in a MCExpr for constant integers.
190    virtual void EmitIntValue(uint64_t Value, unsigned Size,unsigned AddrSpace);
191
192    /// EmitFill - Emit NumBytes bytes worth of the value specified by
193    /// FillValue.  This implements directives such as '.space'.
194    virtual void EmitFill(uint64_t NumBytes, uint8_t FillValue,
195                          unsigned AddrSpace);
196
197    /// EmitZeros - Emit NumBytes worth of zeros.  This is a convenience
198    /// function that just wraps EmitFill.
199    void EmitZeros(uint64_t NumBytes, unsigned AddrSpace) {
200      EmitFill(NumBytes, 0, AddrSpace);
201    }
202
203
204    /// EmitValueToAlignment - Emit some number of copies of @param Value until
205    /// the byte alignment @param ByteAlignment is reached.
206    ///
207    /// If the number of bytes need to emit for the alignment is not a multiple
208    /// of @param ValueSize, then the contents of the emitted fill bytes is
209    /// undefined.
210    ///
211    /// This used to implement the .align assembler directive.
212    ///
213    /// @param ByteAlignment - The alignment to reach. This must be a power of
214    /// two on some targets.
215    /// @param Value - The value to use when filling bytes.
216    /// @param Size - The size of the integer (in bytes) to emit for @param
217    /// Value. This must match a native machine width.
218    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
219    /// the alignment cannot be reached in this many bytes, no bytes are
220    /// emitted.
221    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
222                                      unsigned ValueSize = 1,
223                                      unsigned MaxBytesToEmit = 0) = 0;
224
225    /// EmitValueToOffset - Emit some number of copies of @param Value until the
226    /// byte offset @param Offset is reached.
227    ///
228    /// This is used to implement assembler directives such as .org.
229    ///
230    /// @param Offset - The offset to reach. This may be an expression, but the
231    /// expression must be associated with the current section.
232    /// @param Value - The value to use when filling bytes.
233    virtual void EmitValueToOffset(const MCExpr *Offset,
234                                   unsigned char Value = 0) = 0;
235
236    /// @}
237
238    /// EmitInstruction - Emit the given @param Instruction into the current
239    /// section.
240    virtual void EmitInstruction(const MCInst &Inst) = 0;
241
242    /// Finish - Finish emission of machine code and flush any output.
243    virtual void Finish() = 0;
244  };
245
246  /// createNullStreamer - Create a dummy machine code streamer, which does
247  /// nothing. This is useful for timing the assembler front end.
248  MCStreamer *createNullStreamer(MCContext &Ctx);
249
250  /// createAsmStreamer - Create a machine code streamer which will print out
251  /// assembly for the native target, suitable for compiling with a native
252  /// assembler.
253  MCStreamer *createAsmStreamer(MCContext &Ctx, formatted_raw_ostream &OS,
254                                const MCAsmInfo &MAI, bool isLittleEndian,
255                                bool isVerboseAsm,
256                                MCInstPrinter *InstPrint = 0,
257                                MCCodeEmitter *CE = 0);
258
259  // FIXME: These two may end up getting rolled into a single
260  // createObjectStreamer interface, which implements the assembler backend, and
261  // is parameterized on an output object file writer.
262
263  /// createMachOStream - Create a machine code streamer which will generative
264  /// Mach-O format object files.
265  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS,
266                                  MCCodeEmitter *CE = 0);
267
268  /// createELFStreamer - Create a machine code streamer which will generative
269  /// ELF format object files.
270  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
271
272} // end namespace llvm
273
274#endif
275