MCStreamer.h revision f9507ffa5b1c8697009e86bbedaacb51e4c6735d 
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 StringRef;
26  class raw_ostream;
27
28  /// MCStreamer - Streaming machine code generation interface.  This interface
29  /// is intended to provide a programatic interface that is very similar to the
30  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
31  /// "emit directives", etc.  The implementation of this interface retains
32  /// state to know what the current section is etc.
33  ///
34  /// There are multiple implementations of this interface: one for writing out
35  /// a .s file, and implementations that write out .o files of various formats.
36  ///
37  class MCStreamer {
38  public:
39    enum SymbolAttr {
40      Global,         /// .globl
41      Hidden,         /// .hidden (ELF)
42      IndirectSymbol, /// .indirect_symbol (Apple)
43      Internal,       /// .internal (ELF)
44      LazyReference,  /// .lazy_reference (Apple)
45      NoDeadStrip,    /// .no_dead_strip (Apple)
46      PrivateExtern,  /// .private_extern (Apple)
47      Protected,      /// .protected (ELF)
48      Reference,      /// .reference (Apple)
49      Weak,           /// .weak
50      WeakDefinition, /// .weak_definition (Apple)
51      WeakReference,  /// .weak_reference (Apple)
52
53      SymbolAttrFirst = Global,
54      SymbolAttrLast = WeakReference
55    };
56
57    enum AssemblerFlag {
58      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
59    };
60
61  private:
62    MCContext &Context;
63
64    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
65    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
66
67  protected:
68    MCStreamer(MCContext &Ctx);
69
70  public:
71    virtual ~MCStreamer();
72
73    MCContext &getContext() const { return Context; }
74
75    /// @name Symbol & Section Management
76    /// @{
77
78    /// SwitchSection - Set the current section where code is being emitted to
79    /// @param Section.
80    ///
81    /// This corresponds to assembler directives like .section, .text, etc.
82    virtual void SwitchSection(MCSection *Section) = 0;
83
84    /// EmitLabel - Emit a label for @param Symbol into the current section.
85    ///
86    /// This corresponds to an assembler statement such as:
87    ///   foo:
88    ///
89    /// @param Symbol - The symbol to emit. A given symbol should only be
90    /// emitted as a label once, and symbols emitted as a label should never be
91    /// used in an assignment.
92    //
93    // FIXME: What to do about the current section? Should we get rid of the
94    // symbol section in the constructor and initialize it here?
95    virtual void EmitLabel(MCSymbol *Symbol) = 0;
96
97    /// EmitAssemblerFlag - Note in the output the specified @param Flag
98    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
99
100    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
101    ///
102    /// This corresponds to an assembler statement such as:
103    ///  symbol = value
104    ///
105    /// The assignment generates no code, but has the side effect of binding the
106    /// value in the current context. For the assembly streamer, this prints the
107    /// binding into the .s file.
108    ///
109    /// @param Symbol - The symbol being assigned to.
110    /// @param Value - The value for the symbol.
111    /// @param MakeAbsolute - If true, then the symbol should be given the
112    /// absolute value of @param Value, even if @param Value would be
113    /// relocatable expression. This corresponds to the ".set" directive.
114    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
115                                bool MakeAbsolute = false) = 0;
116
117    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
118    //
119    // FIXME: This doesn't make much sense, could we just have attributes be on
120    // the symbol and make the printer smart enough to add the right symbols?
121    // This should work as long as the order of attributes in the file doesn't
122    // matter.
123    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
124                                     SymbolAttr Attribute) = 0;
125
126    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
127    ///
128    /// @param Symbol - The symbol to have its n_desc field set.
129    /// @param DescValue - The value to set into the n_desc field.
130    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
131
132    /// EmitLocalSymbol - Emit a local symbol of @param Value to @param Symbol.
133    ///
134    /// @param Symbol - The local symbol being created.
135    /// @param Value - The value for the symbol.
136    virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) = 0;
137
138    /// EmitCommonSymbol - Emit a common or local common symbol of @param Size
139    /// with the @param Pow2Alignment if non-zero.
140    ///
141    /// @param Symbol - The common symbol to emit.
142    /// @param Size - The size of the common symbol.
143    /// @param Pow2Alignment - The alignment of the common symbol if non-zero.
144    /// @param IsLocal - If true, then the symbol is to be a local common
145    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
146                                  unsigned Pow2Alignment, bool IsLocal) = 0;
147
148    /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if
149    /// @param Symbol is non-NULL, for @param Size and with the @param
150    /// Pow2Alignment if non-zero.
151    ///
152    /// @param Section - The zerofill section to create and or to put the symbol
153    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
154    /// @param Size - The size of the zerofill symbol.
155    /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero.
156    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0,
157                              unsigned Size = 0,unsigned Pow2Alignment = 0) = 0;
158
159    /// @}
160    /// @name Generating Data
161    /// @{
162
163    /// EmitBytes - Emit the bytes in @param Data into the output.
164    ///
165    /// This is used to implement assembler directives such as .byte, .ascii,
166    /// etc.
167    virtual void EmitBytes(const StringRef &Data) = 0;
168
169    /// EmitValue - Emit the expression @param Value into the output as a native
170    /// integer of the given @param Size bytes.
171    ///
172    /// This is used to implement assembler directives such as .word, .quad,
173    /// etc.
174    ///
175    /// @param Value - The value to emit.
176    /// @param Size - The size of the integer (in bytes) to emit. This must
177    /// match a native machine width.
178    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
179
180    /// EmitValueToAlignment - Emit some number of copies of @param Value until
181    /// the byte alignment @param ByteAlignment is reached.
182    ///
183    /// If the number of bytes need to emit for the alignment is not a multiple
184    /// of @param ValueSize, then the contents of the emitted fill bytes is
185    /// undefined.
186    ///
187    /// This used to implement the .align assembler directive.
188    ///
189    /// @param ByteAlignment - The alignment to reach. This must be a power of
190    /// two on some targets.
191    /// @param Value - The value to use when filling bytes.
192    /// @param Size - The size of the integer (in bytes) to emit for @param
193    /// Value. This must match a native machine width.
194    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
195    /// the alignment cannot be reached in this many bytes, no bytes are
196    /// emitted.
197    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
198                                      unsigned ValueSize = 1,
199                                      unsigned MaxBytesToEmit = 0) = 0;
200
201    /// EmitValueToOffset - Emit some number of copies of @param Value until the
202    /// byte offset @param Offset is reached.
203    ///
204    /// This is used to implement assembler directives such as .org.
205    ///
206    /// @param Offset - The offset to reach.This may be an expression, but the
207    /// expression must be associated with the current section.
208    /// @param Value - The value to use when filling bytes.
209    //
210    // FIXME: How are we going to signal failures out of this?
211    virtual void EmitValueToOffset(const MCValue &Offset,
212                                   unsigned char Value = 0) = 0;
213
214    /// @}
215
216    /// EmitInstruction - Emit the given @param Instruction into the current
217    /// section.
218    virtual void EmitInstruction(const MCInst &Inst) = 0;
219
220    /// Finish - Finish emission of machine code and flush any output.
221    virtual void Finish() = 0;
222  };
223
224  /// createAsmStreamer - Create a machine code streamer which will print out
225  /// assembly for the native target, suitable for compiling with a native
226  /// assembler.
227  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
228
229  // FIXME: These two may end up getting rolled into a single
230  // createObjectStreamer interface, which implements the assembler backend, and
231  // is parameterized on an output object file writer.
232
233  /// createMachOStream - Create a machine code streamer which will generative
234  /// Mach-O format object files.
235  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
236
237  /// createELFStreamer - Create a machine code streamer which will generative
238  /// ELF format object files.
239  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
240
241} // end namespace llvm
242
243#endif
244