MCStreamer.h revision 5026ae4514caf5bb88d6c09fbf56a9db2753ed43 
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    /// @}
166    /// @name Generating Data
167    /// @{
168
169    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
170    /// output.
171    ///
172    /// This is used to implement assembler directives such as .byte, .ascii,
173    /// etc.
174    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
175
176    /// EmitValue - Emit the expression @param Value into the output as a native
177    /// integer of the given @param Size bytes.
178    ///
179    /// This is used to implement assembler directives such as .word, .quad,
180    /// etc.
181    ///
182    /// @param Value - The value to emit.
183    /// @param Size - The size of the integer (in bytes) to emit. This must
184    /// match a native machine width.
185    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
186
187    /// EmitValueToAlignment - Emit some number of copies of @param Value until
188    /// the byte alignment @param ByteAlignment is reached.
189    ///
190    /// If the number of bytes need to emit for the alignment is not a multiple
191    /// of @param ValueSize, then the contents of the emitted fill bytes is
192    /// undefined.
193    ///
194    /// This used to implement the .align assembler directive.
195    ///
196    /// @param ByteAlignment - The alignment to reach. This must be a power of
197    /// two on some targets.
198    /// @param Value - The value to use when filling bytes.
199    /// @param Size - The size of the integer (in bytes) to emit for @param
200    /// Value. This must match a native machine width.
201    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
202    /// the alignment cannot be reached in this many bytes, no bytes are
203    /// emitted.
204    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
205                                      unsigned ValueSize = 1,
206                                      unsigned MaxBytesToEmit = 0) = 0;
207
208    /// EmitValueToOffset - Emit some number of copies of @param Value until the
209    /// byte offset @param Offset is reached.
210    ///
211    /// This is used to implement assembler directives such as .org.
212    ///
213    /// @param Offset - The offset to reach.This may be an expression, but the
214    /// expression must be associated with the current section.
215    /// @param Value - The value to use when filling bytes.
216    //
217    // FIXME: How are we going to signal failures out of this?
218    virtual void EmitValueToOffset(const MCValue &Offset,
219                                   unsigned char Value = 0) = 0;
220
221    /// @}
222
223    /// EmitInstruction - Emit the given @param Instruction into the current
224    /// section.
225    virtual void EmitInstruction(const MCInst &Inst) = 0;
226
227    /// Finish - Finish emission of machine code and flush any output.
228    virtual void Finish() = 0;
229  };
230
231  /// createAsmStreamer - Create a machine code streamer which will print out
232  /// assembly for the native target, suitable for compiling with a native
233  /// assembler.
234  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
235
236  // FIXME: These two may end up getting rolled into a single
237  // createObjectStreamer interface, which implements the assembler backend, and
238  // is parameterized on an output object file writer.
239
240  /// createMachOStream - Create a machine code streamer which will generative
241  /// Mach-O format object files.
242  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
243
244  /// createELFStreamer - Create a machine code streamer which will generative
245  /// ELF format object files.
246  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
247
248} // end namespace llvm
249
250#endif
251