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/SmallVector.h"
14 
15 namespace llvm {
16 class MCAssembler;
17 class MCFragment;
18 class MCSectionData;
19 class MCSymbolData;
20 
21 /// Encapsulates the layout of an assembly file at a particular point in time.
22 ///
23 /// Assembly may requiring compute multiple layouts for a particular assembly
24 /// file as part of the relaxation process. This class encapsulates the layout
25 /// at a single point in time in such a way that it is always possible to
26 /// efficiently compute the exact addresses of any symbol in the assembly file,
27 /// even during the relaxation process.
28 class MCAsmLayout {
29 public:
30   typedef llvm::SmallVectorImpl<MCSectionData*>::const_iterator const_iterator;
31   typedef llvm::SmallVectorImpl<MCSectionData*>::iterator iterator;
32 
33 private:
34   MCAssembler &Assembler;
35 
36   /// List of sections in layout order.
37   llvm::SmallVector<MCSectionData*, 16> SectionOrder;
38 
39   /// The last fragment which was layed out, or 0 if nothing has been layed
40   /// out. Fragments are always layed out in order, so all fragments with a
41   /// lower ordinal will be up to date.
42   mutable MCFragment *LastValidFragment;
43 
44   /// \brief Make sure that the layout for the given fragment is valid, lazily
45   /// computing it if necessary.
46   void EnsureValid(const MCFragment *F) const;
47 
48   bool isSectionUpToDate(const MCSectionData *SD) const;
49   bool isFragmentUpToDate(const MCFragment *F) const;
50 
51 public:
52   MCAsmLayout(MCAssembler &_Assembler);
53 
54   /// Get the assembler object this is a layout for.
getAssembler()55   MCAssembler &getAssembler() const { return Assembler; }
56 
57   /// \brief Update the layout because a fragment has been resized. The
58   /// fragments size should have already been updated, the \arg SlideAmount is
59   /// the delta from the old size.
60   void UpdateForSlide(MCFragment *F, int SlideAmount);
61 
62   /// \brief Update the layout because a fragment has been replaced.
63   void FragmentReplaced(MCFragment *Src, MCFragment *Dst);
64 
65   /// \brief Perform a full layout.
66   void LayoutFile();
67 
68   /// \brief Perform layout for a single fragment, assuming that the previous
69   /// fragment has already been layed out correctly, and the parent section has
70   /// been initialized.
71   void LayoutFragment(MCFragment *Fragment);
72 
73   /// \brief Performs initial layout for a single section, assuming that the
74   /// previous section (including its fragments) has already been layed out
75   /// correctly.
76   void LayoutSection(MCSectionData *SD);
77 
78   /// @name Section Access (in layout order)
79   /// @{
80 
getSectionOrder()81   llvm::SmallVectorImpl<MCSectionData*> &getSectionOrder() {
82     return SectionOrder;
83   }
getSectionOrder()84   const llvm::SmallVectorImpl<MCSectionData*> &getSectionOrder() const {
85     return SectionOrder;
86   }
87 
88   /// @}
89   /// @name Fragment Layout Data
90   /// @{
91 
92   /// \brief Get the effective size of the given fragment, as computed in the
93   /// current layout.
94   uint64_t getFragmentEffectiveSize(const MCFragment *F) const;
95 
96   /// \brief Get the offset of the given fragment inside its containing section.
97   uint64_t getFragmentOffset(const MCFragment *F) const;
98 
99   /// @}
100   /// @name Section Layout Data
101   /// @{
102 
103   /// \brief Get the computed address of the given section.
104   uint64_t getSectionAddress(const MCSectionData *SD) const;
105 
106   /// @}
107   /// @name Utility Functions
108   /// @{
109 
110   /// \brief Get the address of the given fragment, as computed in the current
111   /// layout.
112   uint64_t getFragmentAddress(const MCFragment *F) const;
113 
114   /// \brief Get the address space size of the given section, as it effects
115   /// layout. This may differ from the size reported by \see getSectionSize() by
116   /// not including section tail padding.
117   uint64_t getSectionAddressSize(const MCSectionData *SD) const;
118 
119   /// \brief Get the data size of the given section, as emitted to the object
120   /// file. This may include additional padding, or be 0 for virtual sections.
121   uint64_t getSectionFileSize(const MCSectionData *SD) const;
122 
123   /// \brief Get the logical data size of the given section.
124   uint64_t getSectionSize(const MCSectionData *SD) const;
125 
126   /// \brief Get the address of the given symbol, as computed in the current
127   /// layout.
128   uint64_t getSymbolAddress(const MCSymbolData *SD) const;
129 
130   /// @}
131 };
132 
133 } // end namespace llvm
134 
135 #endif
136