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;
MCSectionCOFF(StringRef Section,unsigned Characteristics,MCSymbol * COMDATSymbol,int Selection,SectionKind K,MCSymbol * Begin)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 
getSectionName()69   StringRef getSectionName() const { return SectionName; }
getCharacteristics()70   unsigned getCharacteristics() const { return Characteristics; }
getCOMDATSymbol()71   MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; }
getSelection()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 
getOrAssignWinCFISectionID(unsigned * NextID)81   unsigned getOrAssignWinCFISectionID(unsigned *NextID) const {
82     if (WinCFISectionID == ~0U)
83       WinCFISectionID = (*NextID)++;
84     return WinCFISectionID;
85   }
86 
classof(const MCSection * S)87   static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; }
88 };
89 
90 } // end namespace llvm
91 
92 #endif
93