MCStreamer.h revision e18e0c58dcd740c64e962fefde44249d685d0568 
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  private:
57    MCContext &Context;
58
59    MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT
60    MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT
61
62  protected:
63    MCStreamer(MCContext &Ctx);
64
65  public:
66    virtual ~MCStreamer();
67
68    MCContext &getContext() const { return Context; }
69
70    /// @name Symbol & Section Management
71    /// @{
72
73    /// SwitchSection - Set the current section where code is being emitted to
74    /// @param Section.
75    ///
76    /// This corresponds to assembler directives like .section, .text, etc.
77    virtual void SwitchSection(MCSection *Section) = 0;
78
79    /// EmitLabel - Emit a label for @param Symbol into the current section.
80    ///
81    /// This corresponds to an assembler statement such as:
82    ///   foo:
83    ///
84    /// @param Symbol - The symbol to emit. A given symbol should only be
85    /// emitted as a label once, and symbols emitted as a label should never be
86    /// used in an assignment.
87    //
88    // FIXME: What to do about the current section? Should we get rid of the
89    // symbol section in the constructor and initialize it here?
90    virtual void EmitLabel(MCSymbol *Symbol) = 0;
91
92    /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
93    ///
94    /// This corresponds to an assembler statement such as:
95    ///  symbol = value
96    ///
97    /// The assignment generates no code, but has the side effect of binding the
98    /// value in the current context. For the assembly streamer, this prints the
99    /// binding into the .s file.
100    ///
101    /// @param Symbol - The symbol being assigned to.
102    /// @param Value - The value for the symbol.
103    /// @param MakeAbsolute - If true, then the symbol should be given the
104    /// absolute value of @param Value, even if @param Value would be
105    /// relocatable expression. This corresponds to the ".set" directive.
106    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
107                                bool MakeAbsolute = false) = 0;
108
109    /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol.
110    //
111    // FIXME: This doesn't make much sense, could we just have attributes be on
112    // the symbol and make the printer smart enough to add the right symbols?
113    // This should work as long as the order of attributes in the file doesn't
114    // matter.
115    virtual void EmitSymbolAttribute(MCSymbol *Symbol,
116                                     SymbolAttr Attribute) = 0;
117
118    /// @}
119    /// @name Generating Data
120    /// @{
121
122    /// EmitBytes - Emit @param Length bytes starting at @param Data into the
123    /// output.
124    ///
125    /// This is used to implement assembler directives such as .byte, .ascii,
126    /// etc.
127    virtual void EmitBytes(const char *Data, unsigned Length) = 0;
128
129    /// EmitValue - Emit the expression @param Value into the output as a native
130    /// integer of the given @param Size bytes.
131    ///
132    /// This is used to implement assembler directives such as .word, .quad,
133    /// etc.
134    ///
135    /// @param Value - The value to emit.
136    /// @param Size - The size of the integer (in bytes) to emit. This must
137    /// match a native machine width.
138    virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
139
140    /// EmitValueToAlignment - Emit some number of copies of @param Value until
141    /// the byte alignment @param ByteAlignment is reached.
142    ///
143    /// If the number of bytes need to emit for the alignment is not a multiple
144    /// of @param ValueSize, then the contents of the emitted fill bytes is
145    /// undefined.
146    ///
147    /// This used to implement the .align assembler directive.
148    ///
149    /// @param ByteAlignment - The alignment to reach. This must be a power of
150    /// two on some targets.
151    /// @param Value - The value to use when filling bytes.
152    /// @param Size - The size of the integer (in bytes) to emit for @param
153    /// Value. This must match a native machine width.
154    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
155    /// the alignment cannot be reached in this many bytes, no bytes are
156    /// emitted.
157    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
158                                      unsigned ValueSize = 1,
159                                      unsigned MaxBytesToEmit = 0) = 0;
160
161    /// EmitValueToOffset - Emit some number of copies of @param Value until the
162    /// byte offset @param Offset is reached.
163    ///
164    /// This is used to implement assembler directives such as .org.
165    ///
166    /// @param Offset - The offset to reach.This may be an expression, but the
167    /// expression must be associated with the current section.
168    /// @param Value - The value to use when filling bytes.
169    //
170    // FIXME: How are we going to signal failures out of this?
171    virtual void EmitValueToOffset(const MCValue &Offset,
172                                   unsigned char Value = 0) = 0;
173
174    /// @}
175
176    /// EmitInstruction - Emit the given @param Instruction into the current
177    /// section.
178    virtual void EmitInstruction(const MCInst &Inst) = 0;
179
180    /// Finish - Finish emission of machine code and flush any output.
181    virtual void Finish() = 0;
182  };
183
184  /// createAsmStreamer - Create a machine code streamer which will print out
185  /// assembly for the native target, suitable for compiling with a native
186  /// assembler.
187  MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS);
188
189  // FIXME: These two may end up getting rolled into a single
190  // createObjectStreamer interface, which implements the assembler backend, and
191  // is parameterized on an output object file writer.
192
193  /// createMachOStream - Create a machine code streamer which will generative
194  /// Mach-O format object files.
195  MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS);
196
197  /// createELFStreamer - Create a machine code streamer which will generative
198  /// ELF format object files.
199  MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS);
200
201} // end namespace llvm
202
203#endif
204