MCStreamer.h revision f96db468fcf62d671cda99b68b6cfd3f2dc0b839 
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    enum AssemblerFlag {
57      SubsectionsViaSymbols  /// .subsections_via_symbols (Apple)
58    };
59
60  private:
61    MCContext &Context;
62
63    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
64    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
65
66  protected:
67    MCStreamer(MCContext &Ctx);
68
69  public:
70    virtual ~MCStreamer();
71
72    MCContext &getContext() const { return Context; }
73
74    /// @name Symbol & Section Management
75    /// @{
76
77    /// SwitchSection - Set the current section where code is being emitted to
78    /// @param Section.
79    ///
80    /// This corresponds to assembler directives like .section, .text, etc.
81    virtual void SwitchSection(MCSection *Section) = 0;
82
83    /// EmitLabel - Emit a label for @param Symbol into the current section.
84    ///
85    /// This corresponds to an assembler statement such as:
86    ///   foo:
87    ///
88    /// @param Symbol - The symbol to emit. A given symbol should only be
89    /// emitted as a label once, and symbols emitted as a label should never be
90    /// used in an assignment.
91    //
92    // FIXME: What to do about the current section? Should we get rid of the
93    // symbol section in the constructor and initialize it here?
94    virtual void EmitLabel(MCSymbol *Symbol) = 0;
95
96    /// EmitAssemblerFlag - Note in the output the specified @param Flag
97    virtual void EmitAssemblerFlag(AssemblerFlag Flag) = 0;
98
99    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
100    ///
101    /// This corresponds to an assembler statement such as:
102    ///  symbol = value
103    ///
104    /// The assignment generates no code, but has the side effect of binding the
105    /// value in the current context. For the assembly streamer, this prints the
106    /// binding into the .s file.
107    ///
108    /// @param Symbol - The symbol being assigned to.
109    /// @param Value - The value for the symbol.
110    /// @param MakeAbsolute - If true, then the symbol should be given the
111    /// absolute value of @param Value, even if @param Value would be
112    /// relocatable expression. This corresponds to the ".set" directive.
113    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
114                                bool MakeAbsolute = false) = 0;
115
116    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
117    //
118    // FIXME: This doesn't make much sense, could we just have attributes be on
119    // the symbol and make the printer smart enough to add the right symbols?
120    // This should work as long as the order of attributes in the file doesn't
121    // matter.
122    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
123                                     SymbolAttr Attribute) = 0;
124
125    /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol.
126    ///
127    /// @param Symbol - The symbol to have its n_desc field set.
128    /// @param DescValue - The value to set into the n_desc field.
129    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0;
130
131    /// EmitLocalSymbol - Emit a local symbol of @param Value to @param Symbol.
132    ///
133    /// @param Symbol - The local symbol being created.
134    /// @param Value - The value for the symbol.
135    virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) = 0;
136
137    /// EmitCommonSymbol - Emit a common or local common symbol of @param Size
138    /// with the @param Pow2Alignment if non-zero.
139    ///
140    /// @param Symbol - The common symbol to emit.
141    /// @param Size - The size of the common symbol.
142    /// @param Pow2Alignment - The alignment of the common symbol if non-zero.
143    /// @param IsLocal - If true, then the symbol is to be a local common
144    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
145                                  unsigned Pow2Alignment, bool IsLocal) = 0;
146
147    /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if
148    /// @param Symbol is non-NULL, for @param Size and with the @param
149    /// Pow2Alignment if non-zero.
150    ///
151    /// @param Section - The zerofill section to create and or to put the symbol
152    /// @param Symbol - The zerofill symbol to emit, if non-NULL.
153    /// @param Size - The size of the zerofill symbol.
154    /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero.
155    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0,
156                              unsigned Size = 0,unsigned Pow2Alignment = 0) = 0;
157
158    /// AbortAssembly - Stop and don't produce output, printing @param
159    /// AbortReason if non-NULL to indicate the reason the assembly is
160    /// terminated.
161    ///
162    /// @param AbortReason - The reason assembly is terminated, if non-NULL.
163    virtual void AbortAssembly(const char *AbortReason) = 0;
164
165    /// DumpSymbolsandMacros - Dump to the specified file in @param FileName all
166    /// symbols and macros at this point in the assembly.
167    ///
168    /// @param FileName - The file to dump the symbols and macros into.
169    virtual void DumpSymbolsandMacros(const char *FileName) = 0;
170
171    /// LoadSymbolsandMacros - Load from the specified file in @param FileName
172    /// symbols and macros into the assembler at this point in the assembly.
173    ///
174    /// @param FileName - The file to load the symbols and macros from.
175    virtual void LoadSymbolsandMacros(const char *FileName) = 0;
176
177    /// @}
178    /// @name Generating Data
179    /// @{
180
181    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
182    /// output.
183    ///
184    /// This is used to implement assembler directives such as .byte, .ascii,
185    /// etc.
186    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
187
188    /// EmitValue - Emit the expression @param Value into the output as a native
189    /// integer of the given @param Size bytes.
190    ///
191    /// This is used to implement assembler directives such as .word, .quad,
192    /// etc.
193    ///
194    /// @param Value - The value to emit.
195    /// @param Size - The size of the integer (in bytes) to emit. This must
196    /// match a native machine width.
197    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
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    //
229    // FIXME: How are we going to signal failures out of this?
230    virtual void EmitValueToOffset(const MCValue &Offset,
231                                   unsigned char Value = 0) = 0;
232
233    /// @}
234
235    /// EmitInstruction - Emit the given @param Instruction into the current
236    /// section.
237    virtual void EmitInstruction(const MCInst &Inst) = 0;
238
239    /// Finish - Finish emission of machine code and flush any output.
240    virtual void Finish() = 0;
241  };
242
243  /// createAsmStreamer - Create a machine code streamer which will print out
244  /// assembly for the native target, suitable for compiling with a native
245  /// assembler.
246  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
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