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      1 //===- MCSectionCOFF.h - COFF Machine Code Sections -------------*- 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 // This file declares the MCSectionCOFF class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_MC_MCSECTIONCOFF_H
     15 #define LLVM_MC_MCSECTIONCOFF_H
     16 
     17 #include "llvm/ADT/StringRef.h"
     18 #include "llvm/MC/MCSection.h"
     19 
     20 namespace llvm {
     21 class MCSymbol;
     22 
     23 /// This represents a section on Windows
     24 class MCSectionCOFF final : public MCSection {
     25   // The memory for this string is stored in the same MCContext as *this.
     26   StringRef SectionName;
     27 
     28   // FIXME: The following fields should not be mutable, but are for now so the
     29   // asm parser can honor the .linkonce directive.
     30 
     31   /// This is the Characteristics field of a section, drawn from the enums
     32   /// below.
     33   mutable unsigned Characteristics;
     34 
     35   /// The unique IDs used with the .pdata and .xdata sections created internally
     36   /// by the assembler. This ID is used to ensure that for every .text section,
     37   /// there is exactly one .pdata and one .xdata section, which is required by
     38   /// the Microsoft incremental linker. This data is mutable because this ID is
     39   /// not notionally part of the section.
     40   mutable unsigned WinCFISectionID = ~0U;
     41 
     42   /// The COMDAT symbol of this section. Only valid if this is a COMDAT section.
     43   /// Two COMDAT sections are merged if they have the same COMDAT symbol.
     44   MCSymbol *COMDATSymbol;
     45 
     46   /// This is the Selection field for the section symbol, if it is a COMDAT
     47   /// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0
     48   mutable int Selection;
     49 
     50 private:
     51   friend class MCContext;
     52   MCSectionCOFF(StringRef Section, unsigned Characteristics,
     53                 MCSymbol *COMDATSymbol, int Selection, SectionKind K,
     54                 MCSymbol *Begin)
     55       : MCSection(SV_COFF, K, Begin), SectionName(Section),
     56         Characteristics(Characteristics), COMDATSymbol(COMDATSymbol),
     57         Selection(Selection) {
     58     assert((Characteristics & 0x00F00000) == 0 &&
     59            "alignment must not be set upon section creation");
     60   }
     61 
     62 public:
     63   ~MCSectionCOFF();
     64 
     65   /// Decides whether a '.section' directive should be printed before the
     66   /// section name
     67   bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
     68 
     69   StringRef getSectionName() const { return SectionName; }
     70   unsigned getCharacteristics() const { return Characteristics; }
     71   MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; }
     72   int getSelection() const { return Selection; }
     73 
     74   void setSelection(int Selection) const;
     75 
     76   void PrintSwitchToSection(const MCAsmInfo &MAI, raw_ostream &OS,
     77                             const MCExpr *Subsection) const override;
     78   bool UseCodeAlign() const override;
     79   bool isVirtualSection() const override;
     80 
     81   unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
     82     if (WinCFISectionID == ~0U)
     83       WinCFISectionID = (*NextID)++;
     84     return WinCFISectionID;
     85   }
     86 
     87   static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; }
     88 };
     89 
     90 } // end namespace llvm
     91 
     92 #endif
     93