MCStreamer.h revision 1fc3d7558139eb6081a7ee5a8f88506d44c8dd7f 
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    /// @}
129    /// @name Generating Data
130    /// @{
131
132    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
133    /// output.
134    ///
135    /// This is used to implement assembler directives such as .byte, .ascii,
136    /// etc.
137    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
138
139    /// EmitValue - Emit the expression @param Value into the output as a native
140    /// integer of the given @param Size bytes.
141    ///
142    /// This is used to implement assembler directives such as .word, .quad,
143    /// etc.
144    ///
145    /// @param Value - The value to emit.
146    /// @param Size - The size of the integer (in bytes) to emit. This must
147    /// match a native machine width.
148    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
149
150    /// EmitValueToAlignment - Emit some number of copies of @param Value until
151    /// the byte alignment @param ByteAlignment is reached.
152    ///
153    /// If the number of bytes need to emit for the alignment is not a multiple
154    /// of @param ValueSize, then the contents of the emitted fill bytes is
155    /// undefined.
156    ///
157    /// This used to implement the .align assembler directive.
158    ///
159    /// @param ByteAlignment - The alignment to reach. This must be a power of
160    /// two on some targets.
161    /// @param Value - The value to use when filling bytes.
162    /// @param Size - The size of the integer (in bytes) to emit for @param
163    /// Value. This must match a native machine width.
164    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
165    /// the alignment cannot be reached in this many bytes, no bytes are
166    /// emitted.
167    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
168                                      unsigned ValueSize = 1,
169                                      unsigned MaxBytesToEmit = 0) = 0;
170
171    /// EmitValueToOffset - Emit some number of copies of @param Value until the
172    /// byte offset @param Offset is reached.
173    ///
174    /// This is used to implement assembler directives such as .org.
175    ///
176    /// @param Offset - The offset to reach.This may be an expression, but the
177    /// expression must be associated with the current section.
178    /// @param Value - The value to use when filling bytes.
179    //
180    // FIXME: How are we going to signal failures out of this?
181    virtual void EmitValueToOffset(const MCValue &Offset,
182                                   unsigned char Value = 0) = 0;
183
184    /// @}
185
186    /// EmitInstruction - Emit the given @param Instruction into the current
187    /// section.
188    virtual void EmitInstruction(const MCInst &Inst) = 0;
189
190    /// Finish - Finish emission of machine code and flush any output.
191    virtual void Finish() = 0;
192  };
193
194  /// createAsmStreamer - Create a machine code streamer which will print out
195  /// assembly for the native target, suitable for compiling with a native
196  /// assembler.
197  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
198
199  // FIXME: These two may end up getting rolled into a single
200  // createObjectStreamer interface, which implements the assembler backend, and
201  // is parameterized on an output object file writer.
202
203  /// createMachOStream - Create a machine code streamer which will generative
204  /// Mach-O format object files.
205  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
206
207  /// createELFStreamer - Create a machine code streamer which will generative
208  /// ELF format object files.
209  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
210
211} // end namespace llvm
212
213#endif
214