MCStreamer.h revision d32c7cfa248f685e6e3064c0958dc2f0c31a4df6 
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/System/DataTypes.h"
18
19namespace llvm {
20  class MCAsmInfo;
21  class MCCodeEmitter;
22  class MCContext;
23  class MCExpr;
24  class MCInst;
25  class MCInstPrinter;
26  class MCSection;
27  class MCSymbol;
28  class StringRef;
29  class Twine;
30  class raw_ostream;
31  class formatted_raw_ostream;
32
33  /// MCStreamer - Streaming machine code generation interface.  This interface
34  /// is intended to provide a programatic interface that is very similar to the
35  /// level that an assembler .s file provides.  It has callbacks to emit bytes,
36  /// handle directives, etc.  The implementation of this interface retains
37  /// state to know what the current section is etc.
38  ///
39  /// There are multiple implementations of this interface: one for writing out
40  /// a .s file, and implementations that write out .o files of various formats.
41  ///
42  class MCStreamer {
43  public:
44    enum SymbolAttr {
45      Global,         /// .globl
46      Hidden,         /// .hidden (ELF)
47      IndirectSymbol, /// .indirect_symbol (Apple)
48      Internal,       /// .internal (ELF)
49      LazyReference,  /// .lazy_reference (Apple)
50      NoDeadStrip,    /// .no_dead_strip (Apple)
51      PrivateExtern,  /// .private_extern (Apple)
52      Protected,      /// .protected (ELF)
53      Reference,      /// .reference (Apple)
54      Weak,           /// .weak
55      WeakDefinition, /// .weak_definition (Apple)
56      WeakReference,  /// .weak_reference (Apple)
57
58      SymbolAttrFirst = Global,
59      SymbolAttrLast = WeakReference
60    };
61
62    enum AssemblerFlag {
63      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
64    };
65
66  private:
67    MCContext &Context;
68
69    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
70    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
71
72  protected:
73    MCStreamer(MCContext &Ctx);
74
75    /// CurSection - This is the current section code is being emitted to, it is
76    /// kept up to date by SwitchSection.
77    const MCSection *CurSection;
78
79  public:
80    virtual ~MCStreamer();
81
82    MCContext &getContext() const { return Context; }
83
84    /// AddComment - Add a comment that can be emitted to the generated .s
85    /// file if applicable as a QoI issue to make the output of the compiler
86    /// more readable.  This only affects the MCAsmStreamer, and only when
87    /// verbose assembly output is enabled.
88    ///
89    /// If the comment includes embedded \n's, they will each get the comment
90    /// prefix as appropriate.  The added comment should not end with a \n.
91    virtual void AddComment(const Twine &T) {}
92
93    /// @name Symbol & Section Management
94    /// @{
95
96    /// getCurrentSection - Return the current seciton that the streamer is
97    /// emitting code to.
98    const MCSection *getCurrentSection() const { return CurSection; }
99
100    /// SwitchSection - Set the current section where code is being emitted to
101    /// @param Section.  This is required to update CurSection.
102    ///
103    /// This corresponds to assembler directives like .section, .text, etc.
104    virtual void SwitchSection(const MCSection *Section) = 0;
105
106    /// EmitLabel - Emit a label for @param Symbol into the current section.
107    ///
108    /// This corresponds to an assembler statement such as:
109    ///   foo:
110    ///
111    /// @param Symbol - The symbol to emit. A given symbol should only be
112    /// emitted as a label once, and symbols emitted as a label should never be
113    /// used in an assignment.
114    virtual void EmitLabel(MCSymbol *Symbol) = 0;
115
116    /// EmitAssemblerFlag - Note in the output the specified @param Flag
117    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
118
119    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
120    ///
121    /// This corresponds to an assembler statement such as:
122    ///  symbol = value
123    ///
124    /// The assignment generates no code, but has the side effect of binding the
125    /// value in the current context. For the assembly streamer, this prints the
126    /// binding into the .s file.
127    ///
128    /// @param Symbol - The symbol being assigned to.
129    /// @param Value - The value for the symbol.
130    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) = 0;
131
132    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
133    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
134                                     SymbolAttr Attribute) = 0;
135
136    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
137    ///
138    /// @param Symbol - The symbol to have its n_desc field set.
139    /// @param DescValue - The value to set into the n_desc field.
140    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
141
142    /// EmitCommonSymbol - Emit a common or local common symbol.
143    ///
144    /// @param Symbol - The common symbol to emit.
145    /// @param Size - The size of the common symbol.
146    /// @param ByteAlignment - The alignment of the symbol if
147    /// non-zero. This must be a power of 2 on some targets.
148    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
149                                  unsigned ByteAlignment) = 0;
150
151    /// EmitZerofill - Emit a the zerofill section and an option symbol.
152    ///
153    /// @param Section - The zerofill section to create and or to put the symbol
154    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
155    /// @param Size - The size of the zerofill symbol.
156    /// @param ByteAlignment - The alignment of the zerofill symbol if
157    /// non-zero. This must be a power of 2 on some targets.
158    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
159                              unsigned Size = 0,unsigned ByteAlignment = 0) = 0;
160
161    /// @}
162    /// @name Generating Data
163    /// @{
164
165    /// EmitBytes - Emit the bytes in \arg Data into the output.
166    ///
167    /// This is used to implement assembler directives such as .byte, .ascii,
168    /// etc.
169    virtual void EmitBytes(StringRef Data, unsigned AddrSpace) = 0;
170
171    /// EmitValue - Emit the expression @param Value into the output as a native
172    /// integer of the given @param Size bytes.
173    ///
174    /// This is used to implement assembler directives such as .word, .quad,
175    /// etc.
176    ///
177    /// @param Value - The value to emit.
178    /// @param Size - The size of the integer (in bytes) to emit. This must
179    /// match a native machine width.
180    virtual void EmitValue(const MCExpr *Value, unsigned Size,
181                           unsigned AddrSpace) = 0;
182
183    /// EmitIntValue - Special case of EmitValue that avoids the client having
184    /// to pass in a MCExpr for constant integers.
185    virtual void EmitIntValue(uint64_t Value, unsigned Size,unsigned AddrSpace);
186
187    /// EmitFill - Emit NumBytes bytes worth of the value specified by
188    /// FillValue.  This implements directives such as '.space'.
189    virtual void EmitFill(uint64_t NumBytes, uint8_t FillValue,
190                          unsigned AddrSpace);
191
192    /// EmitZeros - Emit NumBytes worth of zeros.  This is a convenience
193    /// function that just wraps EmitFill.
194    void EmitZeros(uint64_t NumBytes, unsigned AddrSpace) {
195      EmitFill(NumBytes, 0, AddrSpace);
196    }
197
198
199    /// EmitValueToAlignment - Emit some number of copies of @param Value until
200    /// the byte alignment @param ByteAlignment is reached.
201    ///
202    /// If the number of bytes need to emit for the alignment is not a multiple
203    /// of @param ValueSize, then the contents of the emitted fill bytes is
204    /// undefined.
205    ///
206    /// This used to implement the .align assembler directive.
207    ///
208    /// @param ByteAlignment - The alignment to reach. This must be a power of
209    /// two on some targets.
210    /// @param Value - The value to use when filling bytes.
211    /// @param Size - The size of the integer (in bytes) to emit for @param
212    /// Value. This must match a native machine width.
213    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
214    /// the alignment cannot be reached in this many bytes, no bytes are
215    /// emitted.
216    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
217                                      unsigned ValueSize = 1,
218                                      unsigned MaxBytesToEmit = 0) = 0;
219
220    /// EmitValueToOffset - Emit some number of copies of @param Value until the
221    /// byte offset @param Offset is reached.
222    ///
223    /// This is used to implement assembler directives such as .org.
224    ///
225    /// @param Offset - The offset to reach. This may be an expression, but the
226    /// expression must be associated with the current section.
227    /// @param Value - The value to use when filling bytes.
228    virtual void EmitValueToOffset(const MCExpr *Offset,
229                                   unsigned char Value = 0) = 0;
230
231    /// @}
232
233    /// EmitInstruction - Emit the given @param Instruction into the current
234    /// section.
235    virtual void EmitInstruction(const MCInst &Inst) = 0;
236
237    /// Finish - Finish emission of machine code and flush any output.
238    virtual void Finish() = 0;
239  };
240
241  /// createNullStreamer - Create a dummy machine code streamer, which does
242  /// nothing. This is useful for timing the assembler front end.
243  MCStreamer *createNullStreamer(MCContext &Ctx);
244
245  /// createAsmStreamer - Create a machine code streamer which will print out
246  /// assembly for the native target, suitable for compiling with a native
247  /// assembler.
248  MCStreamer *createAsmStreamer(MCContext &Ctx, formatted_raw_ostream &OS,
249                                const MCAsmInfo &MAI, bool isLittleEndian,
250                                bool isVerboseAsm,
251                                MCInstPrinter *InstPrint = 0,
252                                MCCodeEmitter *CE = 0);
253
254  // FIXME: These two may end up getting rolled into a single
255  // createObjectStreamer interface, which implements the assembler backend, and
256  // is parameterized on an output object file writer.
257
258  /// createMachOStream - Create a machine code streamer which will generative
259  /// Mach-O format object files.
260  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS,
261                                  MCCodeEmitter *CE = 0);
262
263  /// createELFStreamer - Create a machine code streamer which will generative
264  /// ELF format object files.
265  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
266
267} // end namespace llvm
268
269#endif
270