MCStreamer.h revision 9be3fee2bdc3126fb87e4e1b31935905f4bcc4d0 
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/Support/DataTypes.h"
18
19namespace llvm {
20  class MCContext;
21  class MCValue;
22  class MCInst;
23  class MCSection;
24  class MCSymbol;
25  class raw_ostream;
26
27  /// MCStreamer - Streaming machine code generation interface.  This interface
28  /// is intended to provide a programatic interface that is very similar to the
29  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
30  /// "emit directives", etc.  The implementation of this interface retains
31  /// state to know what the current section is etc.
32  ///
33  /// There are multiple implementations of this interface: one for writing out
34  /// a .s file, and implementations that write out .o files of various formats.
35  ///
36  class MCStreamer {
37  public:
38    enum SymbolAttr {
39      Global,         /// .globl
40      Hidden,         /// .hidden (ELF)
41      IndirectSymbol, /// .indirect_symbol (Apple)
42      Internal,       /// .internal (ELF)
43      LazyReference,  /// .lazy_reference (Apple)
44      NoDeadStrip,    /// .no_dead_strip (Apple)
45      PrivateExtern,  /// .private_extern (Apple)
46      Protected,      /// .protected (ELF)
47      Reference,      /// .reference (Apple)
48      Weak,           /// .weak
49      WeakDefinition, /// .weak_definition (Apple)
50      WeakReference,  /// .weak_reference (Apple)
51
52      SymbolAttrFirst = Global,
53      SymbolAttrLast = WeakReference
54    };
55
56  private:
57    MCContext &Context;
58
59    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
60    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
61
62  protected:
63    MCStreamer(MCContext &Ctx);
64
65  public:
66    virtual ~MCStreamer();
67
68    MCContext &getContext() const { return Context; }
69
70    /// @name Symbol & Section Management
71    /// @{
72
73    /// SwitchSection - Set the current section where code is being emitted to
74    /// @param Section.
75    ///
76    /// This corresponds to assembler directives like .section, .text, etc.
77    virtual void SwitchSection(MCSection *Section) = 0;
78
79    /// EmitLabel - Emit a label for @param Symbol into the current section.
80    ///
81    /// This corresponds to an assembler statement such as:
82    ///   foo:
83    ///
84    /// @param Symbol - The symbol to emit. A given symbol should only be
85    /// emitted as a label once, and symbols emitted as a label should never be
86    /// used in an assignment.
87    //
88    // FIXME: What to do about the current section? Should we get rid of the
89    // symbol section in the constructor and initialize it here?
90    virtual void EmitLabel(MCSymbol *Symbol) = 0;
91
92    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
93    ///
94    /// This corresponds to an assembler statement such as:
95    ///  symbol = value
96    ///
97    /// The assignment generates no code, but has the side effect of binding the
98    /// value in the current context. For the assembly streamer, this prints the
99    /// binding into the .s file.
100    ///
101    /// @param Symbol - The symbol being assigned to.
102    /// @param Value - The value for the symbol.
103    /// @param MakeAbsolute - If true, then the symbol should be given the
104    /// absolute value of @param Value, even if @param Value would be
105    /// relocatable expression. This corresponds to the ".set" directive.
106    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
107                                bool MakeAbsolute = false) = 0;
108
109    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
110    //
111    // FIXME: This doesn't make much sense, could we just have attributes be on
112    // the symbol and make the printer smart enough to add the right symbols?
113    // This should work as long as the order of attributes in the file doesn't
114    // matter.
115    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
116                                     SymbolAttr Attribute) = 0;
117
118    /// EmitCommonSymbol - Emit a common or local common symbol of @param Size
119    /// with the @param Pow2Alignment if non-zero.
120    ///
121    /// @param Symbol - The common symbol to emit.
122    /// @param Size - The size of the common symbol.
123    /// @param Pow2Alignment - The alignment of the common symbol if non-zero.
124    /// @param IsLocal - If true, then the symbol is to be a local common
125    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
126                                  unsigned Pow2Alignment, bool IsLocal) = 0;
127
128    /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if
129    /// @param Symbol is non-NULL, for @param Size and with the @param
130    /// Pow2Alignment if non-zero.
131    ///
132    /// @param Section - The zerofill section to create and or to put the symbol
133    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
134    /// @param Size - The size of the zerofill symbol.
135    /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero.
136    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0,
137                              unsigned Size = 0,unsigned Pow2Alignment = 0) = 0;
138
139    /// @}
140    /// @name Generating Data
141    /// @{
142
143    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
144    /// output.
145    ///
146    /// This is used to implement assembler directives such as .byte, .ascii,
147    /// etc.
148    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
149
150    /// EmitValue - Emit the expression @param Value into the output as a native
151    /// integer of the given @param Size bytes.
152    ///
153    /// This is used to implement assembler directives such as .word, .quad,
154    /// etc.
155    ///
156    /// @param Value - The value to emit.
157    /// @param Size - The size of the integer (in bytes) to emit. This must
158    /// match a native machine width.
159    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
160
161    /// EmitValueToAlignment - Emit some number of copies of @param Value until
162    /// the byte alignment @param ByteAlignment is reached.
163    ///
164    /// If the number of bytes need to emit for the alignment is not a multiple
165    /// of @param ValueSize, then the contents of the emitted fill bytes is
166    /// undefined.
167    ///
168    /// This used to implement the .align assembler directive.
169    ///
170    /// @param ByteAlignment - The alignment to reach. This must be a power of
171    /// two on some targets.
172    /// @param Value - The value to use when filling bytes.
173    /// @param Size - The size of the integer (in bytes) to emit for @param
174    /// Value. This must match a native machine width.
175    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
176    /// the alignment cannot be reached in this many bytes, no bytes are
177    /// emitted.
178    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
179                                      unsigned ValueSize = 1,
180                                      unsigned MaxBytesToEmit = 0) = 0;
181
182    /// EmitValueToOffset - Emit some number of copies of @param Value until the
183    /// byte offset @param Offset is reached.
184    ///
185    /// This is used to implement assembler directives such as .org.
186    ///
187    /// @param Offset - The offset to reach.This may be an expression, but the
188    /// expression must be associated with the current section.
189    /// @param Value - The value to use when filling bytes.
190    //
191    // FIXME: How are we going to signal failures out of this?
192    virtual void EmitValueToOffset(const MCValue &Offset,
193                                   unsigned char Value = 0) = 0;
194
195    /// @}
196
197    /// EmitInstruction - Emit the given @param Instruction into the current
198    /// section.
199    virtual void EmitInstruction(const MCInst &Inst) = 0;
200
201    /// Finish - Finish emission of machine code and flush any output.
202    virtual void Finish() = 0;
203  };
204
205  /// createAsmStreamer - Create a machine code streamer which will print out
206  /// assembly for the native target, suitable for compiling with a native
207  /// assembler.
208  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
209
210  // FIXME: These two may end up getting rolled into a single
211  // createObjectStreamer interface, which implements the assembler backend, and
212  // is parameterized on an output object file writer.
213
214  /// createMachOStream - Create a machine code streamer which will generative
215  /// Mach-O format object files.
216  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
217
218  /// createELFStreamer - Create a machine code streamer which will generative
219  /// ELF format object files.
220  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
221
222} // end namespace llvm
223
224#endif
225