MCStreamer.h revision 8b67f774e9c38b7718b2b300b628388f966df4e0 
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 raw_ostream;
30
31  /// MCStreamer - Streaming machine code generation interface.  This interface
32  /// is intended to provide a programatic interface that is very similar to the
33  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
34  /// handle directives, etc.  The implementation of this interface retains
35  /// state to know what the current section is etc.
36  ///
37  /// There are multiple implementations of this interface: one for writing out
38  /// a .s file, and implementations that write out .o files of various formats.
39  ///
40  class MCStreamer {
41  public:
42    enum SymbolAttr {
43      Global,         /// .globl
44      Hidden,         /// .hidden (ELF)
45      IndirectSymbol, /// .indirect_symbol (Apple)
46      Internal,       /// .internal (ELF)
47      LazyReference,  /// .lazy_reference (Apple)
48      NoDeadStrip,    /// .no_dead_strip (Apple)
49      PrivateExtern,  /// .private_extern (Apple)
50      Protected,      /// .protected (ELF)
51      Reference,      /// .reference (Apple)
52      Weak,           /// .weak
53      WeakDefinition, /// .weak_definition (Apple)
54      WeakReference,  /// .weak_reference (Apple)
55
56      SymbolAttrFirst = Global,
57      SymbolAttrLast = WeakReference
58    };
59
60    enum AssemblerFlag {
61      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
62    };
63
64  private:
65    MCContext &Context;
66
67    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
68    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
69
70  protected:
71    MCStreamer(MCContext &Ctx);
72
73    /// CurSection - This is the current section code is being emitted to, it is
74    /// kept up to date by SwitchSection.
75    const MCSection *CurSection;
76
77  public:
78    virtual ~MCStreamer();
79
80    MCContext &getContext() const { return Context; }
81
82    /// @name Symbol & Section Management
83    /// @{
84
85    /// getCurrentSection - Return the current seciton that the streamer is
86    /// emitting code to.
87    const MCSection *getCurrentSection() const { return CurSection; }
88
89    /// SwitchSection - Set the current section where code is being emitted to
90    /// @param Section.  This is required to update CurSection.
91    ///
92    /// This corresponds to assembler directives like .section, .text, etc.
93    virtual void SwitchSection(const MCSection *Section) = 0;
94
95    /// EmitLabel - Emit a label for @param Symbol into the current section.
96    ///
97    /// This corresponds to an assembler statement such as:
98    ///   foo:
99    ///
100    /// @param Symbol - The symbol to emit. A given symbol should only be
101    /// emitted as a label once, and symbols emitted as a label should never be
102    /// used in an assignment.
103    virtual void EmitLabel(MCSymbol *Symbol) = 0;
104
105    /// EmitAssemblerFlag - Note in the output the specified @param Flag
106    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
107
108    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
109    ///
110    /// This corresponds to an assembler statement such as:
111    ///  symbol = value
112    ///
113    /// The assignment generates no code, but has the side effect of binding the
114    /// value in the current context. For the assembly streamer, this prints the
115    /// binding into the .s file.
116    ///
117    /// @param Symbol - The symbol being assigned to.
118    /// @param Value - The value for the symbol.
119    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) = 0;
120
121    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
122    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
123                                     SymbolAttr Attribute) = 0;
124
125    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
126    ///
127    /// @param Symbol - The symbol to have its n_desc field set.
128    /// @param DescValue - The value to set into the n_desc field.
129    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
130
131    /// EmitCommonSymbol - Emit a common or local common symbol.
132    ///
133    /// @param Symbol - The common symbol to emit.
134    /// @param Size - The size of the common symbol.
135    /// @param ByteAlignment - The alignment of the symbol if
136    /// non-zero. This must be a power of 2 on some targets.
137    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
138                                  unsigned ByteAlignment) = 0;
139
140    /// EmitZerofill - Emit a the zerofill section and an option symbol.
141    ///
142    /// @param Section - The zerofill section to create and or to put the symbol
143    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
144    /// @param Size - The size of the zerofill symbol.
145    /// @param ByteAlignment - The alignment of the zerofill symbol if
146    /// non-zero. This must be a power of 2 on some targets.
147    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
148                              unsigned Size = 0,unsigned ByteAlignment = 0) = 0;
149
150    /// @}
151    /// @name Generating Data
152    /// @{
153
154    /// EmitBytes - Emit the bytes in \arg Data into the output.
155    ///
156    /// This is used to implement assembler directives such as .byte, .ascii,
157    /// etc.
158    virtual void EmitBytes(const StringRef &Data) = 0;
159
160    /// EmitValue - Emit the expression @param Value into the output as a native
161    /// integer of the given @param Size bytes.
162    ///
163    /// This is used to implement assembler directives such as .word, .quad,
164    /// etc.
165    ///
166    /// @param Value - The value to emit.
167    /// @param Size - The size of the integer (in bytes) to emit. This must
168    /// match a native machine width.
169    virtual void EmitValue(const MCExpr *Value, unsigned Size) = 0;
170
171    /// EmitValueToAlignment - Emit some number of copies of @param Value until
172    /// the byte alignment @param ByteAlignment is reached.
173    ///
174    /// If the number of bytes need to emit for the alignment is not a multiple
175    /// of @param ValueSize, then the contents of the emitted fill bytes is
176    /// undefined.
177    ///
178    /// This used to implement the .align assembler directive.
179    ///
180    /// @param ByteAlignment - The alignment to reach. This must be a power of
181    /// two on some targets.
182    /// @param Value - The value to use when filling bytes.
183    /// @param Size - The size of the integer (in bytes) to emit for @param
184    /// Value. This must match a native machine width.
185    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
186    /// the alignment cannot be reached in this many bytes, no bytes are
187    /// emitted.
188    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
189                                      unsigned ValueSize = 1,
190                                      unsigned MaxBytesToEmit = 0) = 0;
191
192    /// EmitValueToOffset - Emit some number of copies of @param Value until the
193    /// byte offset @param Offset is reached.
194    ///
195    /// This is used to implement assembler directives such as .org.
196    ///
197    /// @param Offset - The offset to reach. This may be an expression, but the
198    /// expression must be associated with the current section.
199    /// @param Value - The value to use when filling bytes.
200    virtual void EmitValueToOffset(const MCExpr *Offset,
201                                   unsigned char Value = 0) = 0;
202
203    /// @}
204
205    /// EmitInstruction - Emit the given @param Instruction into the current
206    /// section.
207    virtual void EmitInstruction(const MCInst &Inst) = 0;
208
209    /// Finish - Finish emission of machine code and flush any output.
210    virtual void Finish() = 0;
211  };
212
213  /// createNullStreamer - Create a dummy machine code streamer, which does
214  /// nothing. This is useful for timing the assembler front end.
215  MCStreamer *createNullStreamer(MCContext &Ctx);
216
217  /// createAsmStreamer - Create a machine code streamer which will print out
218  /// assembly for the native target, suitable for compiling with a native
219  /// assembler.
220  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS,
221                                const MCAsmInfo &MAI,
222                                MCInstPrinter *InstPrint = 0,
223                                MCCodeEmitter *CE = 0);
224
225  // FIXME: These two may end up getting rolled into a single
226  // createObjectStreamer interface, which implements the assembler backend, and
227  // is parameterized on an output object file writer.
228
229  /// createMachOStream - Create a machine code streamer which will generative
230  /// Mach-O format object files.
231  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS,
232                                  MCCodeEmitter *CE = 0);
233
234  /// createELFStreamer - Create a machine code streamer which will generative
235  /// ELF format object files.
236  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
237
238} // end namespace llvm
239
240#endif
241