llvm-6502/include/llvm/MC/MCSectionELF.h

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//===- MCSectionELF.h - ELF Machine Code Sections ---------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the MCSectionELF class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCSECTIONELF_H
#define LLVM_MC_MCSECTIONELF_H
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/raw_ostream.h"
namespace llvm {
class MCSymbol;
/// MCSectionELF - This represents a section on linux, lots of unix variants
/// and some bare metal systems.
class MCSectionELF : public MCSection {
/// SectionName - This is the name of the section. The referenced memory is
/// owned by TargetLoweringObjectFileELF's ELFUniqueMap.
StringRef SectionName;
/// Type - This is the sh_type field of a section, drawn from the enums below.
unsigned Type;
/// Flags - This is the sh_flags field of a section, drawn from the enums.
/// below.
unsigned Flags;
unsigned UniqueID;
/// EntrySize - The size of each entry in this section. This size only
/// makes sense for sections that contain fixed-sized entries. If a
/// section does not contain fixed-sized entries 'EntrySize' will be 0.
unsigned EntrySize;
const MCSymbolELF *Group;
/// Depending on the type of the section this is sh_link or sh_info.
const MCSectionELF *Associated;
private:
friend class MCContext;
MCSectionELF(StringRef Section, unsigned type, unsigned flags, SectionKind K,
unsigned entrySize, const MCSymbolELF *group, unsigned UniqueID,
MCSymbol *Begin, const MCSectionELF *Associated)
: MCSection(SV_ELF, K, Begin), SectionName(Section), Type(type),
Flags(flags), UniqueID(UniqueID), EntrySize(entrySize), Group(group),
Associated(Associated) {
if (Group)
Group->setIsSignature();
}
~MCSectionELF() override;
Reimplement debug info compression by compressing the whole section, rather than a fragment. To support compressing the debug_line section that contains multiple fragments (due, I believe, to variation in choices of line table encoding depending on the size of instruction ranges in the actual program code) we needed to support compressing multiple MCFragments in a single pass. This patch implements that behavior by mutating the post-relaxed and relocated section to be the compressed form of its former self, including renaming the section. This is a more flexible (and less invasive, to a degree) implementation that will allow for other features such as "use compression only if it's smaller than the uncompressed data". Compressing debug_frame would be a possible further extension to this work, but I've left it for now. The hurdle there is alignment sections - which might require going as far as to refactor MCAssembler.cpp:writeFragment to handle writing to a byte buffer or an MCObjectWriter (there's already a virtual call there, so it shouldn't add substantial compile-time cost) which could in turn involve refactoring MCAsmBackend::writeNopData to use that same abstraction... which involves touching all the backends. This would remove the limited handling of fragment writing seen in ELFObjectWriter.cpp:getUncompressedData which would be nice - but it's more invasive. I did discover that I (perhaps obviously) don't need to handle relocations when I rewrite the fragments - since the relocations have already been applied and computed (and stored into ELFObjectWriter::Relocations) by this stage (necessarily, because we need to have written any immediate values or assembly-time relocations into the data already before we compress it, which we have). The test case doesn't necessarily cover that in detail - I can add more test coverage if that's preferred. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205990 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-10 21:53:53 +00:00
void setSectionName(StringRef Name) { SectionName = Name; }
public:
/// ShouldOmitSectionDirective - Decides whether a '.section' directive
/// should be printed before the section name
bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
StringRef getSectionName() const { return SectionName; }
unsigned getType() const { return Type; }
unsigned getFlags() const { return Flags; }
unsigned getEntrySize() const { return EntrySize; }
const MCSymbolELF *getGroup() const { return Group; }
void PrintSwitchToSection(const MCAsmInfo &MAI, raw_ostream &OS,
const MCExpr *Subsection) const override;
bool UseCodeAlign() const override;
bool isVirtualSection() const override;
bool isUnique() const { return UniqueID != ~0U; }
unsigned getUniqueID() const { return UniqueID; }
const MCSectionELF *getAssociatedSection() const { return Associated; }
static bool classof(const MCSection *S) {
return S->getVariant() == SV_ELF;
}
};
} // end namespace llvm
#endif