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8007c5924c
This change introduces support for zero flag ELF section groups to LLVM. LLVM already supports COMDAT sections, which in ELF are a special type of ELF section groups. These are generally useful to enable linker GC where you want a group of sections to always travel together, that is to be either retained or discarded as a whole, but without the COMDAT semantics. Other ELF assemblers already support zero flag ELF section groups and this change helps us reach feature parity. Differential Revision: https://reviews.llvm.org/D95851
104 lines
3.6 KiB
C++
104 lines
3.6 KiB
C++
//===- MCSectionELF.h - ELF Machine Code Sections ---------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the MCSectionELF class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_MC_MCSECTIONELF_H
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#define LLVM_MC_MCSECTIONELF_H
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#include "llvm/ADT/PointerIntPair.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/MC/MCSection.h"
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#include "llvm/MC/MCSymbolELF.h"
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#include "llvm/MC/SectionKind.h"
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namespace llvm {
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class MCSymbol;
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/// This represents a section on linux, lots of unix variants and some bare
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/// metal systems.
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class MCSectionELF final : public MCSection {
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/// This is the sh_type field of a section, drawn from the enums below.
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unsigned Type;
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/// This is the sh_flags field of a section, drawn from the enums below.
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unsigned Flags;
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unsigned UniqueID;
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/// The size of each entry in this section. This size only makes sense for
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/// sections that contain fixed-sized entries. If a section does not contain
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/// fixed-sized entries 'EntrySize' will be 0.
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unsigned EntrySize;
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/// The section group signature symbol (if not null) and a bool indicating
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/// whether this is a GRP_COMDAT group.
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const PointerIntPair<const MCSymbolELF *, 1, bool> Group;
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/// Used by SHF_LINK_ORDER. If non-null, the sh_link field will be set to the
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/// section header index of the section where LinkedToSym is defined.
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const MCSymbol *LinkedToSym;
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private:
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friend class MCContext;
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// The storage of Name is owned by MCContext's ELFUniquingMap.
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MCSectionELF(StringRef Name, unsigned type, unsigned flags, SectionKind K,
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unsigned entrySize, const MCSymbolELF *group, bool IsComdat,
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unsigned UniqueID, MCSymbol *Begin,
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const MCSymbolELF *LinkedToSym)
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: MCSection(SV_ELF, Name, K, Begin), Type(type), Flags(flags),
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UniqueID(UniqueID), EntrySize(entrySize), Group(group, IsComdat),
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LinkedToSym(LinkedToSym) {
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if (Group.getPointer())
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Group.getPointer()->setIsSignature();
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}
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// TODO Delete after we stop supporting generation of GNU-style .zdebug_*
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// sections.
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void setSectionName(StringRef Name) { this->Name = Name; }
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public:
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/// Decides whether a '.section' directive should be printed before the
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/// section name
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bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
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unsigned getType() const { return Type; }
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unsigned getFlags() const { return Flags; }
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unsigned getEntrySize() const { return EntrySize; }
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void setFlags(unsigned F) { Flags = F; }
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const MCSymbolELF *getGroup() const { return Group.getPointer(); }
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bool isComdat() const { return Group.getInt(); }
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void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
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raw_ostream &OS,
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const MCExpr *Subsection) const override;
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bool UseCodeAlign() const override;
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bool isVirtualSection() const override;
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StringRef getVirtualSectionKind() const override;
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bool isUnique() const { return UniqueID != NonUniqueID; }
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unsigned getUniqueID() const { return UniqueID; }
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const MCSection *getLinkedToSection() const {
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return &LinkedToSym->getSection();
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}
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const MCSymbol *getLinkedToSymbol() const { return LinkedToSym; }
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static bool classof(const MCSection *S) {
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return S->getVariant() == SV_ELF;
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}
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};
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} // end namespace llvm
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#endif // LLVM_MC_MCSECTIONELF_H
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