MCContext.h revision 287df1bc0309962770b6c176f2d143795dd3cc2f 
1//===- MCContext.h - Machine Code Context -----------------------*- 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#ifndef LLVM_MC_MCCONTEXT_H
11#define LLVM_MC_MCCONTEXT_H
12
13#include "llvm/MC/SectionKind.h"
14#include "llvm/ADT/DenseMap.h"
15#include "llvm/ADT/StringMap.h"
16#include "llvm/Support/Allocator.h"
17
18namespace llvm {
19  class MCAsmInfo;
20  class MCExpr;
21  class MCSection;
22  class MCSymbol;
23  class StringRef;
24  class Twine;
25  class MCSectionMachO;
26
27  /// MCContext - Context object for machine code objects.  This class owns all
28  /// of the sections that it creates.
29  ///
30  class MCContext {
31    MCContext(const MCContext&); // DO NOT IMPLEMENT
32    MCContext &operator=(const MCContext&); // DO NOT IMPLEMENT
33
34    /// The MCAsmInfo for this target.
35    const MCAsmInfo &MAI;
36
37    /// Sections - Bindings of names to allocated sections.
38    StringMap<MCSection*> Sections;
39
40    /// Symbols - Bindings of names to symbols.
41    StringMap<MCSymbol*> Symbols;
42
43    /// NextUniqueID - The next ID to dole out to an unnamed assembler temporary
44    /// symbol.
45    unsigned NextUniqueID;
46
47    /// Allocator - Allocator object used for creating machine code objects.
48    ///
49    /// We use a bump pointer allocator to avoid the need to track all allocated
50    /// objects.
51    BumpPtrAllocator Allocator;
52
53    void *MachOUniquingMap, *ELFUniquingMap;
54  public:
55    explicit MCContext(const MCAsmInfo &MAI);
56    ~MCContext();
57
58    const MCAsmInfo &getAsmInfo() const { return MAI; }
59
60    /// @name Symbol Managment
61    /// @{
62
63    /// CreateTempSymbol - Create and return a new assembler temporary symbol
64    /// with a unique but unspecified name.
65    MCSymbol *CreateTempSymbol();
66
67    /// GetOrCreateSymbol - Lookup the symbol inside with the specified
68    /// @p Name.  If it exists, return it.  If not, create a forward
69    /// reference and return it.
70    ///
71    /// @param Name - The symbol name, which must be unique across all symbols.
72    MCSymbol *GetOrCreateSymbol(StringRef Name);
73    MCSymbol *GetOrCreateSymbol(const Twine &Name);
74
75    /// LookupSymbol - Get the symbol for \p Name, or null.
76    MCSymbol *LookupSymbol(StringRef Name) const;
77
78    /// @}
79
80    /// @name Section Managment
81    /// @{
82
83    /// getMachOSection - Return the MCSection for the specified mach-o section.
84    /// This requires the operands to be valid.
85    const MCSectionMachO *getMachOSection(StringRef Segment,
86                                          StringRef Section,
87                                          unsigned TypeAndAttributes,
88                                          unsigned Reserved2,
89                                          SectionKind K);
90    const MCSectionMachO *getMachOSection(StringRef Segment,
91                                          StringRef Section,
92                                          unsigned TypeAndAttributes,
93                                          SectionKind K) {
94      return getMachOSection(Segment, Section, TypeAndAttributes, 0, K);
95    }
96
97    const MCSection *getELFSection(StringRef Section, unsigned Type,
98                                   unsigned Flags, SectionKind Kind,
99                                   bool IsExplicit = false);
100
101    /// @}
102
103    void *Allocate(unsigned Size, unsigned Align = 8) {
104      return Allocator.Allocate(Size, Align);
105    }
106    void Deallocate(void *Ptr) {
107    }
108  };
109
110} // end namespace llvm
111
112// operator new and delete aren't allowed inside namespaces.
113// The throw specifications are mandated by the standard.
114/// @brief Placement new for using the MCContext's allocator.
115///
116/// This placement form of operator new uses the MCContext's allocator for
117/// obtaining memory. It is a non-throwing new, which means that it returns
118/// null on error. (If that is what the allocator does. The current does, so if
119/// this ever changes, this operator will have to be changed, too.)
120/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
121/// @code
122/// // Default alignment (16)
123/// IntegerLiteral *Ex = new (Context) IntegerLiteral(arguments);
124/// // Specific alignment
125/// IntegerLiteral *Ex2 = new (Context, 8) IntegerLiteral(arguments);
126/// @endcode
127/// Please note that you cannot use delete on the pointer; it must be
128/// deallocated using an explicit destructor call followed by
129/// @c Context.Deallocate(Ptr).
130///
131/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
132/// @param C The MCContext that provides the allocator.
133/// @param Alignment The alignment of the allocated memory (if the underlying
134///                  allocator supports it).
135/// @return The allocated memory. Could be NULL.
136inline void *operator new(size_t Bytes, llvm::MCContext &C,
137                          size_t Alignment = 16) throw () {
138  return C.Allocate(Bytes, Alignment);
139}
140/// @brief Placement delete companion to the new above.
141///
142/// This operator is just a companion to the new above. There is no way of
143/// invoking it directly; see the new operator for more details. This operator
144/// is called implicitly by the compiler if a placement new expression using
145/// the MCContext throws in the object constructor.
146inline void operator delete(void *Ptr, llvm::MCContext &C, size_t)
147              throw () {
148  C.Deallocate(Ptr);
149}
150
151/// This placement form of operator new[] uses the MCContext's allocator for
152/// obtaining memory. It is a non-throwing new[], which means that it returns
153/// null on error.
154/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
155/// @code
156/// // Default alignment (16)
157/// char *data = new (Context) char[10];
158/// // Specific alignment
159/// char *data = new (Context, 8) char[10];
160/// @endcode
161/// Please note that you cannot use delete on the pointer; it must be
162/// deallocated using an explicit destructor call followed by
163/// @c Context.Deallocate(Ptr).
164///
165/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
166/// @param C The MCContext that provides the allocator.
167/// @param Alignment The alignment of the allocated memory (if the underlying
168///                  allocator supports it).
169/// @return The allocated memory. Could be NULL.
170inline void *operator new[](size_t Bytes, llvm::MCContext& C,
171                            size_t Alignment = 16) throw () {
172  return C.Allocate(Bytes, Alignment);
173}
174
175/// @brief Placement delete[] companion to the new[] above.
176///
177/// This operator is just a companion to the new[] above. There is no way of
178/// invoking it directly; see the new[] operator for more details. This operator
179/// is called implicitly by the compiler if a placement new[] expression using
180/// the MCContext throws in the object constructor.
181inline void operator delete[](void *Ptr, llvm::MCContext &C) throw () {
182  C.Deallocate(Ptr);
183}
184
185#endif
186