MCContext.h revision c18409aed80ba1c6c5998befd3c3c8edc865c423 
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/ADT/DenseMap.h"
14#include "llvm/ADT/StringMap.h"
15#include "llvm/Support/Allocator.h"
16
17namespace llvm {
18  class MCAsmInfo;
19  class MCExpr;
20  class MCSection;
21  class MCSymbol;
22  class StringRef;
23  class Twine;
24
25  /// MCContext - Context object for machine code objects.  This class owns all
26  /// of the sections that it creates.
27  ///
28  class MCContext {
29    MCContext(const MCContext&); // DO NOT IMPLEMENT
30    MCContext &operator=(const MCContext&); // DO NOT IMPLEMENT
31
32    /// The MCAsmInfo for this target.
33    const MCAsmInfo &MAI;
34
35    /// Sections - Bindings of names to allocated sections.
36    StringMap<MCSection*> Sections;
37
38    /// Symbols - Bindings of names to symbols.
39    StringMap<MCSymbol*> Symbols;
40
41    /// NextUniqueID - The next ID to dole out to an unnamed assembler temporary
42    /// symbol.
43    unsigned NextUniqueID;
44
45    /// Allocator - Allocator object used for creating machine code objects.
46    ///
47    /// We use a bump pointer allocator to avoid the need to track all allocated
48    /// objects.
49    BumpPtrAllocator Allocator;
50  public:
51    MCContext(const MCAsmInfo &MAI);
52    ~MCContext();
53
54    const MCAsmInfo &getAsmInfo() const { return MAI; }
55
56    /// @name Symbol Managment
57    /// @{
58
59    /// GetOrCreateSymbol - Lookup the symbol inside with the specified
60    /// @p Name.  If it exists, return it.  If not, create a forward
61    /// reference and return it.
62    ///
63    /// @param Name - The symbol name, which must be unique across all symbols.
64    MCSymbol *GetOrCreateSymbol(StringRef Name);
65    MCSymbol *GetOrCreateSymbol(const Twine &Name);
66
67    /// GetOrCreateTemporarySymbol - Create a new assembler temporary symbol
68    /// with the specified @p Name if it doesn't exist or return the existing
69    /// one if it does.
70    ///
71    /// @param Name - The symbol name, for debugging purposes only, temporary
72    /// symbols do not surive assembly. If non-empty the name must be unique
73    /// across all symbols.
74    MCSymbol *GetOrCreateTemporarySymbol(StringRef Name = "");
75    MCSymbol *GetOrCreateTemporarySymbol(const Twine &Name);
76
77    /// LookupSymbol - Get the symbol for \p Name, or null.
78    MCSymbol *LookupSymbol(StringRef Name) const;
79
80    /// @}
81
82    void *Allocate(unsigned Size, unsigned Align = 8) {
83      return Allocator.Allocate(Size, Align);
84    }
85    void Deallocate(void *Ptr) {
86    }
87  };
88
89} // end namespace llvm
90
91// operator new and delete aren't allowed inside namespaces.
92// The throw specifications are mandated by the standard.
93/// @brief Placement new for using the MCContext's allocator.
94///
95/// This placement form of operator new uses the MCContext's allocator for
96/// obtaining memory. It is a non-throwing new, which means that it returns
97/// null on error. (If that is what the allocator does. The current does, so if
98/// this ever changes, this operator will have to be changed, too.)
99/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
100/// @code
101/// // Default alignment (16)
102/// IntegerLiteral *Ex = new (Context) IntegerLiteral(arguments);
103/// // Specific alignment
104/// IntegerLiteral *Ex2 = new (Context, 8) IntegerLiteral(arguments);
105/// @endcode
106/// Please note that you cannot use delete on the pointer; it must be
107/// deallocated using an explicit destructor call followed by
108/// @c Context.Deallocate(Ptr).
109///
110/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
111/// @param C The MCContext that provides the allocator.
112/// @param Alignment The alignment of the allocated memory (if the underlying
113///                  allocator supports it).
114/// @return The allocated memory. Could be NULL.
115inline void *operator new(size_t Bytes, llvm::MCContext &C,
116                          size_t Alignment = 16) throw () {
117  return C.Allocate(Bytes, Alignment);
118}
119/// @brief Placement delete companion to the new above.
120///
121/// This operator is just a companion to the new above. There is no way of
122/// invoking it directly; see the new operator for more details. This operator
123/// is called implicitly by the compiler if a placement new expression using
124/// the MCContext throws in the object constructor.
125inline void operator delete(void *Ptr, llvm::MCContext &C, size_t)
126              throw () {
127  C.Deallocate(Ptr);
128}
129
130/// This placement form of operator new[] uses the MCContext's allocator for
131/// obtaining memory. It is a non-throwing new[], which means that it returns
132/// null on error.
133/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
134/// @code
135/// // Default alignment (16)
136/// char *data = new (Context) char[10];
137/// // Specific alignment
138/// char *data = new (Context, 8) char[10];
139/// @endcode
140/// Please note that you cannot use delete on the pointer; it must be
141/// deallocated using an explicit destructor call followed by
142/// @c Context.Deallocate(Ptr).
143///
144/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
145/// @param C The MCContext that provides the allocator.
146/// @param Alignment The alignment of the allocated memory (if the underlying
147///                  allocator supports it).
148/// @return The allocated memory. Could be NULL.
149inline void *operator new[](size_t Bytes, llvm::MCContext& C,
150                            size_t Alignment = 16) throw () {
151  return C.Allocate(Bytes, Alignment);
152}
153
154/// @brief Placement delete[] companion to the new[] above.
155///
156/// This operator is just a companion to the new[] above. There is no way of
157/// invoking it directly; see the new[] operator for more details. This operator
158/// is called implicitly by the compiler if a placement new[] expression using
159/// the MCContext throws in the object constructor.
160inline void operator delete[](void *Ptr, llvm::MCContext &C) throw () {
161  C.Deallocate(Ptr);
162}
163
164#endif
165