MCStreamer.h revision 4a0abd80f18f9c2a10bf5b14cd6731d51972a426 
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 AsmPrinter;
21  class MCAsmInfo;
22  class MCCodeEmitter;
23  class MCContext;
24  class MCInst;
25  class MCSection;
26  class MCSymbol;
27  class MCValue;
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  /// "emit 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  public:
77    virtual ~MCStreamer();
78
79    MCContext &getContext() const { return Context; }
80
81    /// @name Symbol & Section Management
82    /// @{
83
84    /// SwitchSection - Set the current section where code is being emitted to
85    /// @param Section.  This is required to update CurSection.
86    ///
87    /// This corresponds to assembler directives like .section, .text, etc.
88    virtual void SwitchSection(const MCSection *Section) = 0;
89
90
91    /// getCurrentSection - Return the current seciton that the streamer is
92    /// emitting code to.
93    const MCSection *getCurrentSection() const { return CurSection; }
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    //
104    // FIXME: What to do about the current section? Should we get rid of the
105    // symbol section in the constructor and initialize it here?
106    virtual void EmitLabel(MCSymbol *Symbol) = 0;
107
108    /// EmitAssemblerFlag - Note in the output the specified @param Flag
109    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
110
111    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
112    ///
113    /// This corresponds to an assembler statement such as:
114    ///  symbol = value
115    ///
116    /// The assignment generates no code, but has the side effect of binding the
117    /// value in the current context. For the assembly streamer, this prints the
118    /// binding into the .s file.
119    ///
120    /// @param Symbol - The symbol being assigned to.
121    /// @param Value - The value for the symbol.
122    /// @param MakeAbsolute - If true, then the symbol should be given the
123    /// absolute value of @param Value, even if @param Value would be
124    /// relocatable expression. This corresponds to the ".set" directive.
125    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
126                                bool MakeAbsolute = false) = 0;
127
128    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
129    //
130    // FIXME: This doesn't make much sense, could we just have attributes be on
131    // the symbol and make the printer smart enough to add the right symbols?
132    // This should work as long as the order of attributes in the file doesn't
133    // matter.
134    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
135                                     SymbolAttr Attribute) = 0;
136
137    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
138    ///
139    /// @param Symbol - The symbol to have its n_desc field set.
140    /// @param DescValue - The value to set into the n_desc field.
141    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
142
143    /// EmitLocalSymbol - Emit a local symbol of @param Value to @param Symbol.
144    ///
145    /// @param Symbol - The local symbol being created.
146    /// @param Value - The value for the symbol.
147    virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) = 0;
148
149    /// EmitCommonSymbol - Emit a common or local common symbol of @param Size
150    /// with the @param Pow2Alignment if non-zero.
151    ///
152    /// @param Symbol - The common symbol to emit.
153    /// @param Size - The size of the common symbol.
154    /// @param Pow2Alignment - The alignment of the common symbol if non-zero.
155    /// @param IsLocal - If true, then the symbol is to be a local common
156    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
157                                  unsigned Pow2Alignment, bool IsLocal) = 0;
158
159    /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if
160    /// @param Symbol is non-NULL, for @param Size and with the @param
161    /// Pow2Alignment if non-zero.
162    ///
163    /// @param Section - The zerofill section to create and or to put the symbol
164    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
165    /// @param Size - The size of the zerofill symbol.
166    /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero.
167    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0,
168                              unsigned Size = 0,unsigned Pow2Alignment = 0) = 0;
169
170    /// @}
171    /// @name Generating Data
172    /// @{
173
174    /// EmitBytes - Emit the bytes in @param Data into the output.
175    ///
176    /// This is used to implement assembler directives such as .byte, .ascii,
177    /// etc.
178    virtual void EmitBytes(const StringRef &Data) = 0;
179
180    /// EmitValue - Emit the expression @param Value into the output as a native
181    /// integer of the given @param Size bytes.
182    ///
183    /// This is used to implement assembler directives such as .word, .quad,
184    /// etc.
185    ///
186    /// @param Value - The value to emit.
187    /// @param Size - The size of the integer (in bytes) to emit. This must
188    /// match a native machine width.
189    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
190
191    /// EmitValueToAlignment - Emit some number of copies of @param Value until
192    /// the byte alignment @param ByteAlignment is reached.
193    ///
194    /// If the number of bytes need to emit for the alignment is not a multiple
195    /// of @param ValueSize, then the contents of the emitted fill bytes is
196    /// undefined.
197    ///
198    /// This used to implement the .align assembler directive.
199    ///
200    /// @param ByteAlignment - The alignment to reach. This must be a power of
201    /// two on some targets.
202    /// @param Value - The value to use when filling bytes.
203    /// @param Size - The size of the integer (in bytes) to emit for @param
204    /// Value. This must match a native machine width.
205    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
206    /// the alignment cannot be reached in this many bytes, no bytes are
207    /// emitted.
208    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
209                                      unsigned ValueSize = 1,
210                                      unsigned MaxBytesToEmit = 0) = 0;
211
212    /// EmitValueToOffset - Emit some number of copies of @param Value until the
213    /// byte offset @param Offset is reached.
214    ///
215    /// This is used to implement assembler directives such as .org.
216    ///
217    /// @param Offset - The offset to reach.This may be an expression, but the
218    /// expression must be associated with the current section.
219    /// @param Value - The value to use when filling bytes.
220    //
221    // FIXME: How are we going to signal failures out of this?
222    virtual void EmitValueToOffset(const MCValue &Offset,
223                                   unsigned char Value = 0) = 0;
224
225    /// @}
226
227    /// EmitInstruction - Emit the given @param Instruction into the current
228    /// section.
229    virtual void EmitInstruction(const MCInst &Inst) = 0;
230
231    /// Finish - Finish emission of machine code and flush any output.
232    virtual void Finish() = 0;
233  };
234
235  /// createNullStreamer - Create a dummy machine code streamer, which does
236  /// nothing. This is useful for timing the assembler front end.
237  MCStreamer *createNullStreamer(MCContext &Ctx);
238
239  /// createAsmStreamer - Create a machine code streamer which will print out
240  /// assembly for the native target, suitable for compiling with a native
241  /// assembler.
242  ///
243  /// \arg AP - If given, an AsmPrinter to use for printing instructions.
244  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS,
245                                const MCAsmInfo &MAI, AsmPrinter *AP = 0,
246                                MCCodeEmitter *CE = 0);
247
248  // FIXME: These two may end up getting rolled into a single
249  // createObjectStreamer interface, which implements the assembler backend, and
250  // is parameterized on an output object file writer.
251
252  /// createMachOStream - Create a machine code streamer which will generative
253  /// Mach-O format object files.
254  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
255
256  /// createELFStreamer - Create a machine code streamer which will generative
257  /// ELF format object files.
258  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
259
260} // end namespace llvm
261
262#endif
263