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      1 //===- MCAsmLayout.h - Assembly Layout Object -------------------*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_MC_MCASMLAYOUT_H
     10 #define LLVM_MC_MCASMLAYOUT_H
     11 
     12 #include "llvm/ADT/DenseMap.h"
     13 #include "llvm/ADT/SmallVector.h"
     14 
     15 namespace llvm {
     16 class MCAssembler;
     17 class MCFragment;
     18 class MCSection;
     19 class MCSymbol;
     20 
     21 /// Encapsulates the layout of an assembly file at a particular point in time.
     22 ///
     23 /// Assembly may require computing 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 address of any symbol in the assembly file,
     27 /// even during the relaxation process.
     28 class MCAsmLayout {
     29   MCAssembler &Assembler;
     30 
     31   /// List of sections in layout order.
     32   llvm::SmallVector<MCSection *, 16> SectionOrder;
     33 
     34   /// The last fragment which was laid out, or 0 if nothing has been laid
     35   /// out. Fragments are always laid out in order, so all fragments with a
     36   /// lower ordinal will be valid.
     37   mutable DenseMap<const MCSection *, MCFragment *> LastValidFragment;
     38 
     39   /// Make sure that the layout for the given fragment is valid, lazily
     40   /// computing it if necessary.
     41   void ensureValid(const MCFragment *F) const;
     42 
     43   /// Is the layout for this fragment valid?
     44   bool isFragmentValid(const MCFragment *F) const;
     45 
     46 public:
     47   MCAsmLayout(MCAssembler &Assembler);
     48 
     49   /// Get the assembler object this is a layout for.
     50   MCAssembler &getAssembler() const { return Assembler; }
     51 
     52   /// \returns whether the offset of fragment \p F can be obtained via
     53   /// getFragmentOffset.
     54   bool canGetFragmentOffset(const MCFragment *F) const;
     55 
     56   /// Invalidate the fragments starting with F because it has been
     57   /// resized. The fragment's size should have already been updated, but
     58   /// its bundle padding will be recomputed.
     59   void invalidateFragmentsFrom(MCFragment *F);
     60 
     61   /// Perform layout for a single fragment, assuming that the previous
     62   /// fragment has already been laid out correctly, and the parent section has
     63   /// been initialized.
     64   void layoutFragment(MCFragment *Fragment);
     65 
     66   /// \name Section Access (in layout order)
     67   /// @{
     68 
     69   llvm::SmallVectorImpl<MCSection *> &getSectionOrder() { return SectionOrder; }
     70   const llvm::SmallVectorImpl<MCSection *> &getSectionOrder() const {
     71     return SectionOrder;
     72   }
     73 
     74   /// @}
     75   /// \name Fragment Layout Data
     76   /// @{
     77 
     78   /// Get the offset of the given fragment inside its containing section.
     79   uint64_t getFragmentOffset(const MCFragment *F) const;
     80 
     81   /// @}
     82   /// \name Utility Functions
     83   /// @{
     84 
     85   /// Get the address space size of the given section, as it effects
     86   /// layout. This may differ from the size reported by \see getSectionSize() by
     87   /// not including section tail padding.
     88   uint64_t getSectionAddressSize(const MCSection *Sec) const;
     89 
     90   /// Get the data size of the given section, as emitted to the object
     91   /// file. This may include additional padding, or be 0 for virtual sections.
     92   uint64_t getSectionFileSize(const MCSection *Sec) const;
     93 
     94   /// Get the offset of the given symbol, as computed in the current
     95   /// layout.
     96   /// \return True on success.
     97   bool getSymbolOffset(const MCSymbol &S, uint64_t &Val) const;
     98 
     99   /// Variant that reports a fatal error if the offset is not computable.
    100   uint64_t getSymbolOffset(const MCSymbol &S) const;
    101 
    102   /// If this symbol is equivalent to A + Constant, return A.
    103   const MCSymbol *getBaseSymbol(const MCSymbol &Symbol) const;
    104 
    105   /// @}
    106 };
    107 
    108 } // end namespace llvm
    109 
    110 #endif
    111