MCStreamer.h revision a5c783280f83df5c60a8ed9e32c61b05a11048e3 
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    /// SubsectionsViaSymbols - Note in the output that the conventions used in
93    /// in the assembly file allows the bytes of a section to be divided up at
94    /// the boundaries of the symbols by a link editor for processing as atoms.
95    virtual void SubsectionsViaSymbols(void) = 0;
96
97    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
98    ///
99    /// This corresponds to an assembler statement such as:
100    ///  symbol = value
101    ///
102    /// The assignment generates no code, but has the side effect of binding the
103    /// value in the current context. For the assembly streamer, this prints the
104    /// binding into the .s file.
105    ///
106    /// @param Symbol - The symbol being assigned to.
107    /// @param Value - The value for the symbol.
108    /// @param MakeAbsolute - If true, then the symbol should be given the
109    /// absolute value of @param Value, even if @param Value would be
110    /// relocatable expression. This corresponds to the ".set" directive.
111    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
112                                bool MakeAbsolute = false) = 0;
113
114    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
115    //
116    // FIXME: This doesn't make much sense, could we just have attributes be on
117    // the symbol and make the printer smart enough to add the right symbols?
118    // This should work as long as the order of attributes in the file doesn't
119    // matter.
120    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
121                                     SymbolAttr Attribute) = 0;
122
123    /// EmitCommonSymbol - Emit a common or local common symbol of @param Size
124    /// with the @param Pow2Alignment if non-zero.
125    ///
126    /// @param Symbol - The common symbol to emit.
127    /// @param Size - The size of the common symbol.
128    /// @param Pow2Alignment - The alignment of the common symbol if non-zero.
129    /// @param IsLocal - If true, then the symbol is to be a local common
130    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
131                                  unsigned Pow2Alignment, bool IsLocal) = 0;
132
133    /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if
134    /// @param Symbol is non-NULL, for @param Size and with the @param
135    /// Pow2Alignment if non-zero.
136    ///
137    /// @param Section - The zerofill section to create and or to put the symbol
138    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
139    /// @param Size - The size of the zerofill symbol.
140    /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero.
141    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0,
142                              unsigned Size = 0,unsigned Pow2Alignment = 0) = 0;
143
144    /// @}
145    /// @name Generating Data
146    /// @{
147
148    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
149    /// output.
150    ///
151    /// This is used to implement assembler directives such as .byte, .ascii,
152    /// etc.
153    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
154
155    /// EmitValue - Emit the expression @param Value into the output as a native
156    /// integer of the given @param Size bytes.
157    ///
158    /// This is used to implement assembler directives such as .word, .quad,
159    /// etc.
160    ///
161    /// @param Value - The value to emit.
162    /// @param Size - The size of the integer (in bytes) to emit. This must
163    /// match a native machine width.
164    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
165
166    /// EmitValueToAlignment - Emit some number of copies of @param Value until
167    /// the byte alignment @param ByteAlignment is reached.
168    ///
169    /// If the number of bytes need to emit for the alignment is not a multiple
170    /// of @param ValueSize, then the contents of the emitted fill bytes is
171    /// undefined.
172    ///
173    /// This used to implement the .align assembler directive.
174    ///
175    /// @param ByteAlignment - The alignment to reach. This must be a power of
176    /// two on some targets.
177    /// @param Value - The value to use when filling bytes.
178    /// @param Size - The size of the integer (in bytes) to emit for @param
179    /// Value. This must match a native machine width.
180    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
181    /// the alignment cannot be reached in this many bytes, no bytes are
182    /// emitted.
183    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
184                                      unsigned ValueSize = 1,
185                                      unsigned MaxBytesToEmit = 0) = 0;
186
187    /// EmitValueToOffset - Emit some number of copies of @param Value until the
188    /// byte offset @param Offset is reached.
189    ///
190    /// This is used to implement assembler directives such as .org.
191    ///
192    /// @param Offset - The offset to reach.This may be an expression, but the
193    /// expression must be associated with the current section.
194    /// @param Value - The value to use when filling bytes.
195    //
196    // FIXME: How are we going to signal failures out of this?
197    virtual void EmitValueToOffset(const MCValue &Offset,
198                                   unsigned char Value = 0) = 0;
199
200    /// @}
201
202    /// EmitInstruction - Emit the given @param Instruction into the current
203    /// section.
204    virtual void EmitInstruction(const MCInst &Inst) = 0;
205
206    /// Finish - Finish emission of machine code and flush any output.
207    virtual void Finish() = 0;
208  };
209
210  /// createAsmStreamer - Create a machine code streamer which will print out
211  /// assembly for the native target, suitable for compiling with a native
212  /// assembler.
213  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
214
215  // FIXME: These two may end up getting rolled into a single
216  // createObjectStreamer interface, which implements the assembler backend, and
217  // is parameterized on an output object file writer.
218
219  /// createMachOStream - Create a machine code streamer which will generative
220  /// Mach-O format object files.
221  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
222
223  /// createELFStreamer - Create a machine code streamer which will generative
224  /// ELF format object files.
225  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
226
227} // end namespace llvm
228
229#endif
230