include/llvm/MC/MCSectionCOFF.h

   1 //===- MCSectionCOFF.h - COFF Machine Code Sections -------------*- 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 // This file declares the MCSectionCOFF class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_MC_MCSECTIONCOFF_H
  14 #define LLVM_MC_MCSECTIONCOFF_H
  15
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/MC/MCSection.h"
  18 #include "llvm/MC/SectionKind.h"
  19 #include <cassert>
  20
  21 namespace llvm {
  22
  23 class MCSymbol;
  24
  25 /// This represents a section on Windows
  26 class MCSectionCOFF final : public MCSection {
  27   // The memory for this string is stored in the same MCContext as *this.
  28   StringRef SectionName;
  29
  30   // FIXME: The following fields should not be mutable, but are for now so the
  31   // asm parser can honor the .linkonce directive.
  32
  33   /// This is the Characteristics field of a section, drawn from the enums
  34   /// below.
  35   mutable unsigned Characteristics;
  36
  37   /// The unique IDs used with the .pdata and .xdata sections created internally
  38   /// by the assembler. This ID is used to ensure that for every .text section,
  39   /// there is exactly one .pdata and one .xdata section, which is required by
  40   /// the Microsoft incremental linker. This data is mutable because this ID is
  41   /// not notionally part of the section.
  42   mutable unsigned WinCFISectionID = ~0U;
  43
  44   /// The COMDAT symbol of this section. Only valid if this is a COMDAT section.
  45   /// Two COMDAT sections are merged if they have the same COMDAT symbol.
  46   MCSymbol *COMDATSymbol;
  47
  48   /// This is the Selection field for the section symbol, if it is a COMDAT
  49   /// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0
  50   mutable int Selection;
  51
  52 private:
  53   friend class MCContext;
  54   MCSectionCOFF(StringRef Section, unsigned Characteristics,
  55                 MCSymbol *COMDATSymbol, int Selection, SectionKind K,
  56                 MCSymbol *Begin)
  57       : MCSection(SV_COFF, K, Begin), SectionName(Section),
  58         Characteristics(Characteristics), COMDATSymbol(COMDATSymbol),
  59         Selection(Selection) {
  60     assert((Characteristics & 0x00F00000) == 0 &&
  61            "alignment must not be set upon section creation");
  62   }
  63
  64 public:
  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, const Triple &T,
  77                             raw_ostream &OS,
  78                             const MCExpr *Subsection) const override;
  79   bool UseCodeAlign() const override;
  80   bool isVirtualSection() const override;
  81
  82   unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
  83     if (WinCFISectionID == ~0U)
  84       WinCFISectionID = (*NextID)++;
  85     return WinCFISectionID;
  86   }
  87
  88   static bool isImplicitlyDiscardable(StringRef Name) {
  89     return Name.startswith(".debug");
  90   }
  91
  92   static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; }
  93 };
  94
  95 } // end namespace llvm
  96
  97 #endif // LLVM_MC_MCSECTIONCOFF_H