MCContext.h revision 77e76940269b1bed36bc31ee5139b5c90fd13836 
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    explicit MCContext(const MCAsmInfo &MAI);
52    ~MCContext();
53
54    const MCAsmInfo &getAsmInfo() const { return MAI; }
55
56    /// @name Symbol Managment
57    /// @{
58
59    /// CreateTempSymbol - Create and return a new assembler temporary symbol
60    /// with a unique but unspecified name.
61    MCSymbol *CreateTempSymbol();
62
63    /// GetOrCreateSymbol - Lookup the symbol inside with the specified
64    /// @p Name.  If it exists, return it.  If not, create a forward
65    /// reference and return it.
66    ///
67    /// @param Name - The symbol name, which must be unique across all symbols.
68    MCSymbol *GetOrCreateSymbol(StringRef Name, bool isTemporary = false);
69    MCSymbol *GetOrCreateSymbol(const Twine &Name, bool isTemporary = false);
70
71    /// GetOrCreateTemporarySymbol - Create a new assembler temporary symbol
72    /// with the specified @p Name if it doesn't exist or return the existing
73    /// one if it does.
74    ///
75    /// @param Name - The symbol name, for debugging purposes only, temporary
76    /// symbols do not surive assembly.
77    MCSymbol *GetOrCreateTemporarySymbol(StringRef Name) {
78      return GetOrCreateSymbol(Name, true);
79    }
80    MCSymbol *GetOrCreateTemporarySymbol(const Twine &Name);
81
82    /// LookupSymbol - Get the symbol for \p Name, or null.
83    MCSymbol *LookupSymbol(StringRef Name) const;
84
85    /// @}
86
87    void *Allocate(unsigned Size, unsigned Align = 8) {
88      return Allocator.Allocate(Size, Align);
89    }
90    void Deallocate(void *Ptr) {
91    }
92  };
93
94} // end namespace llvm
95
96// operator new and delete aren't allowed inside namespaces.
97// The throw specifications are mandated by the standard.
98/// @brief Placement new for using the MCContext's allocator.
99///
100/// This placement form of operator new uses the MCContext's allocator for
101/// obtaining memory. It is a non-throwing new, which means that it returns
102/// null on error. (If that is what the allocator does. The current does, so if
103/// this ever changes, this operator will have to be changed, too.)
104/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
105/// @code
106/// // Default alignment (16)
107/// IntegerLiteral *Ex = new (Context) IntegerLiteral(arguments);
108/// // Specific alignment
109/// IntegerLiteral *Ex2 = new (Context, 8) IntegerLiteral(arguments);
110/// @endcode
111/// Please note that you cannot use delete on the pointer; it must be
112/// deallocated using an explicit destructor call followed by
113/// @c Context.Deallocate(Ptr).
114///
115/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
116/// @param C The MCContext that provides the allocator.
117/// @param Alignment The alignment of the allocated memory (if the underlying
118///                  allocator supports it).
119/// @return The allocated memory. Could be NULL.
120inline void *operator new(size_t Bytes, llvm::MCContext &C,
121                          size_t Alignment = 16) throw () {
122  return C.Allocate(Bytes, Alignment);
123}
124/// @brief Placement delete companion to the new above.
125///
126/// This operator is just a companion to the new above. There is no way of
127/// invoking it directly; see the new operator for more details. This operator
128/// is called implicitly by the compiler if a placement new expression using
129/// the MCContext throws in the object constructor.
130inline void operator delete(void *Ptr, llvm::MCContext &C, size_t)
131              throw () {
132  C.Deallocate(Ptr);
133}
134
135/// This placement form of operator new[] uses the MCContext's allocator for
136/// obtaining memory. It is a non-throwing new[], which means that it returns
137/// null on error.
138/// Usage looks like this (assuming there's an MCContext 'Context' in scope):
139/// @code
140/// // Default alignment (16)
141/// char *data = new (Context) char[10];
142/// // Specific alignment
143/// char *data = new (Context, 8) char[10];
144/// @endcode
145/// Please note that you cannot use delete on the pointer; it must be
146/// deallocated using an explicit destructor call followed by
147/// @c Context.Deallocate(Ptr).
148///
149/// @param Bytes The number of bytes to allocate. Calculated by the compiler.
150/// @param C The MCContext that provides the allocator.
151/// @param Alignment The alignment of the allocated memory (if the underlying
152///                  allocator supports it).
153/// @return The allocated memory. Could be NULL.
154inline void *operator new[](size_t Bytes, llvm::MCContext& C,
155                            size_t Alignment = 16) throw () {
156  return C.Allocate(Bytes, Alignment);
157}
158
159/// @brief Placement delete[] companion to the new[] above.
160///
161/// This operator is just a companion to the new[] above. There is no way of
162/// invoking it directly; see the new[] operator for more details. This operator
163/// is called implicitly by the compiler if a placement new[] expression using
164/// the MCContext throws in the object constructor.
165inline void operator delete[](void *Ptr, llvm::MCContext &C) throw () {
166  C.Deallocate(Ptr);
167}
168
169#endif
170