MCContext.h revision 6e5ce287b0e53c264af0ba37169ad964e19b5bb7 
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, *COFFUniquingMap;
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    const MCSection *getCOFFSection(StringRef Section, unsigned Characteristics,
102                                    int Selection, SectionKind Kind);
103
104    const MCSection *getCOFFSection(StringRef Section, unsigned Characteristics,
105                                    SectionKind Kind) {
106      return getCOFFSection (Section, Characteristics, 0, Kind);
107    }
108
109
110    /// @}
111
112    void *Allocate(unsigned Size, unsigned Align = 8) {
113      return Allocator.Allocate(Size, Align);
114    }
115    void Deallocate(void *Ptr) {
116    }
117  };
118
119} // end namespace llvm
120
121// operator new and delete aren't allowed inside namespaces.
122// The throw specifications are mandated by the standard.
123/// @brief Placement new for using the MCContext's allocator.
124///
125/// This placement form of operator new uses the MCContext's allocator for
126/// obtaining memory. It is a non-throwing new, which means that it returns
127/// null on error. (If that is what the allocator does. The current does, so if
128/// this ever changes, this operator will have to be changed, too.)
129/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
130/// @code
131/// // Default alignment (16)
132/// IntegerLiteral *Ex = new (Context) IntegerLiteral(arguments);
133/// // Specific alignment
134/// IntegerLiteral *Ex2 = new (Context, 8) IntegerLiteral(arguments);
135/// @endcode
136/// Please note that you cannot use delete on the pointer; it must be
137/// deallocated using an explicit destructor call followed by
138/// @c Context.Deallocate(Ptr).
139///
140/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
141/// @param C The MCContext that provides the allocator.
142/// @param Alignment The alignment of the allocated memory (if the underlying
143///                  allocator supports it).
144/// @return The allocated memory. Could be NULL.
145inline void *operator new(size_t Bytes, llvm::MCContext &C,
146                          size_t Alignment = 16) throw () {
147  return C.Allocate(Bytes, Alignment);
148}
149/// @brief Placement delete companion to the new above.
150///
151/// This operator is just a companion to the new above. There is no way of
152/// invoking it directly; see the new operator for more details. This operator
153/// is called implicitly by the compiler if a placement new expression using
154/// the MCContext throws in the object constructor.
155inline void operator delete(void *Ptr, llvm::MCContext &C, size_t)
156              throw () {
157  C.Deallocate(Ptr);
158}
159
160/// This placement form of operator new[] uses the MCContext's allocator for
161/// obtaining memory. It is a non-throwing new[], which means that it returns
162/// null on error.
163/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
164/// @code
165/// // Default alignment (16)
166/// char *data = new (Context) char[10];
167/// // Specific alignment
168/// char *data = new (Context, 8) char[10];
169/// @endcode
170/// Please note that you cannot use delete on the pointer; it must be
171/// deallocated using an explicit destructor call followed by
172/// @c Context.Deallocate(Ptr).
173///
174/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
175/// @param C The MCContext that provides the allocator.
176/// @param Alignment The alignment of the allocated memory (if the underlying
177///                  allocator supports it).
178/// @return The allocated memory. Could be NULL.
179inline void *operator new[](size_t Bytes, llvm::MCContext& C,
180                            size_t Alignment = 16) throw () {
181  return C.Allocate(Bytes, Alignment);
182}
183
184/// @brief Placement delete[] companion to the new[] above.
185///
186/// This operator is just a companion to the new[] above. There is no way of
187/// invoking it directly; see the new[] operator for more details. This operator
188/// is called implicitly by the compiler if a placement new[] expression using
189/// the MCContext throws in the object constructor.
190inline void operator delete[](void *Ptr, llvm::MCContext &C) throw () {
191  C.Deallocate(Ptr);
192}
193
194#endif
195