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 // FIXME: The following fields should not be mutable, but are for now so the 28 // asm parser can honor the .linkonce directive. 29 30 /// This is the Characteristics field of a section, drawn from the enums 31 /// below. 32 mutable unsigned Characteristics; 33 34 /// The unique IDs used with the .pdata and .xdata sections created internally 35 /// by the assembler. This ID is used to ensure that for every .text section, 36 /// there is exactly one .pdata and one .xdata section, which is required by 37 /// the Microsoft incremental linker. This data is mutable because this ID is 38 /// not notionally part of the section. 39 mutable unsigned WinCFISectionID = ~0U; 40 41 /// The COMDAT symbol of this section. Only valid if this is a COMDAT section. 42 /// Two COMDAT sections are merged if they have the same COMDAT symbol. 43 MCSymbol *COMDATSymbol; 44 45 /// This is the Selection field for the section symbol, if it is a COMDAT 46 /// section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0 47 mutable int Selection; 48 49 private: 50 friend class MCContext; 51 // The storage of Name is owned by MCContext's COFFUniquingMap. MCSectionCOFF(StringRef Name,unsigned Characteristics,MCSymbol * COMDATSymbol,int Selection,SectionKind K,MCSymbol * Begin)52 MCSectionCOFF(StringRef Name, unsigned Characteristics, 53 MCSymbol *COMDATSymbol, int Selection, SectionKind K, 54 MCSymbol *Begin) 55 : MCSection(SV_COFF, Name, K, Begin), Characteristics(Characteristics), 56 COMDATSymbol(COMDATSymbol), Selection(Selection) { 57 assert((Characteristics & 0x00F00000) == 0 && 58 "alignment must not be set upon section creation"); 59 } 60 61 public: 62 /// Decides whether a '.section' directive should be printed before the 63 /// section name 64 bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const; 65 getCharacteristics()66 unsigned getCharacteristics() const { return Characteristics; } getCOMDATSymbol()67 MCSymbol *getCOMDATSymbol() const { return COMDATSymbol; } getSelection()68 int getSelection() const { return Selection; } 69 70 void setSelection(int Selection) const; 71 72 void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T, 73 raw_ostream &OS, 74 const MCExpr *Subsection) const override; 75 bool UseCodeAlign() const override; 76 bool isVirtualSection() const override; 77 StringRef getVirtualSectionKind() const override; 78 getOrAssignWinCFISectionID(unsigned * NextID)79 unsigned getOrAssignWinCFISectionID(unsigned *NextID) const { 80 if (WinCFISectionID == ~0U) 81 WinCFISectionID = (*NextID)++; 82 return WinCFISectionID; 83 } 84 isImplicitlyDiscardable(StringRef Name)85 static bool isImplicitlyDiscardable(StringRef Name) { 86 return Name.startswith(".debug"); 87 } 88 classof(const MCSection * S)89 static bool classof(const MCSection *S) { return S->getVariant() == SV_COFF; } 90 }; 91 92 } // end namespace llvm 93 94 #endif // LLVM_MC_MCSECTIONCOFF_H 95