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
21namespace llvm {
22
23class MCSymbol;
24
25/// This represents a section on Windows
26class 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
52private:
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
64public:
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
98