1//===- MCAsmLayout.h - Assembly Layout Object -------------------*- 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_MCASMLAYOUT_H
11#define LLVM_MC_MCASMLAYOUT_H
12
13#include "llvm/ADT/DenseMap.h"
14#include "llvm/ADT/SmallVector.h"
15
16namespace llvm {
17class MCAssembler;
18class MCFragment;
19class MCSectionData;
20class MCSymbol;
21class MCSymbolData;
22
23/// Encapsulates the layout of an assembly file at a particular point in time.
24///
25/// Assembly may require computing multiple layouts for a particular assembly
26/// file as part of the relaxation process. This class encapsulates the layout
27/// at a single point in time in such a way that it is always possible to
28/// efficiently compute the exact address of any symbol in the assembly file,
29/// even during the relaxation process.
30class MCAsmLayout {
31public:
32  typedef llvm::SmallVectorImpl<MCSectionData*>::const_iterator const_iterator;
33  typedef llvm::SmallVectorImpl<MCSectionData*>::iterator iterator;
34
35private:
36  MCAssembler &Assembler;
37
38  /// List of sections in layout order.
39  llvm::SmallVector<MCSectionData*, 16> SectionOrder;
40
41  /// The last fragment which was laid out, or 0 if nothing has been laid
42  /// out. Fragments are always laid out in order, so all fragments with a
43  /// lower ordinal will be valid.
44  mutable DenseMap<const MCSectionData*, MCFragment*> LastValidFragment;
45
46  /// \brief Make sure that the layout for the given fragment is valid, lazily
47  /// computing it if necessary.
48  void ensureValid(const MCFragment *F) const;
49
50  /// \brief Is the layout for this fragment valid?
51  bool isFragmentValid(const MCFragment *F) const;
52
53  /// \brief Compute the amount of padding required before this fragment to
54  /// obey bundling restrictions.
55  uint64_t computeBundlePadding(const MCFragment *F,
56                                uint64_t FOffset, uint64_t FSize);
57
58public:
59  MCAsmLayout(MCAssembler &_Assembler);
60
61  /// Get the assembler object this is a layout for.
62  MCAssembler &getAssembler() const { return Assembler; }
63
64  /// \brief Invalidate the fragments starting with F because it has been
65  /// resized. The fragment's size should have already been updated, but
66  /// its bundle padding will be recomputed.
67  void invalidateFragmentsFrom(MCFragment *F);
68
69  /// \brief Perform layout for a single fragment, assuming that the previous
70  /// fragment has already been laid out correctly, and the parent section has
71  /// been initialized.
72  void layoutFragment(MCFragment *Fragment);
73
74  /// @name Section Access (in layout order)
75  /// @{
76
77  llvm::SmallVectorImpl<MCSectionData*> &getSectionOrder() {
78    return SectionOrder;
79  }
80  const llvm::SmallVectorImpl<MCSectionData*> &getSectionOrder() const {
81    return SectionOrder;
82  }
83
84  /// @}
85  /// @name Fragment Layout Data
86  /// @{
87
88  /// \brief Get the offset of the given fragment inside its containing section.
89  uint64_t getFragmentOffset(const MCFragment *F) const;
90
91  /// @}
92  /// @name Utility Functions
93  /// @{
94
95  /// \brief Get the address space size of the given section, as it effects
96  /// layout. This may differ from the size reported by \see getSectionSize() by
97  /// not including section tail padding.
98  uint64_t getSectionAddressSize(const MCSectionData *SD) const;
99
100  /// \brief Get the data size of the given section, as emitted to the object
101  /// file. This may include additional padding, or be 0 for virtual sections.
102  uint64_t getSectionFileSize(const MCSectionData *SD) const;
103
104  /// \brief Get the offset of the given symbol, as computed in the current
105  /// layout.
106  /// \result True on success.
107  bool getSymbolOffset(const MCSymbolData *SD, uint64_t &Val) const;
108
109  /// \brief Variant that reports a fatal error if the offset is not computable.
110  uint64_t getSymbolOffset(const MCSymbolData *SD) const;
111
112  /// \brief If this symbol is equivalent to A + Constant, return A.
113  const MCSymbol *getBaseSymbol(const MCSymbol &Symbol) const;
114
115  /// @}
116};
117
118} // end namespace llvm
119
120#endif
121