mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-01-08 18:31:23 +00:00
fe25521451
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
103 lines
3.4 KiB
C++
103 lines
3.4 KiB
C++
//===- 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/StringRef.h"
|
|
#include "llvm/MC/MCSection.h"
|
|
#include "llvm/MC/MCSymbol.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;
|
|
|
|
/// 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 MCSymbol *Group;
|
|
|
|
private:
|
|
friend class MCContext;
|
|
MCSectionELF(StringRef Section, unsigned type, unsigned flags,
|
|
SectionKind K, unsigned entrySize, const MCSymbol *group)
|
|
: MCSection(SV_ELF, K), SectionName(Section), Type(type), Flags(flags),
|
|
EntrySize(entrySize), Group(group) {}
|
|
~MCSectionELF();
|
|
|
|
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; }
|
|
std::string getLabelBeginName() const override {
|
|
if (Group)
|
|
return (SectionName.str() + '_' + Group->getName() + "_begin").str();
|
|
return SectionName.str() + "_begin";
|
|
}
|
|
std::string getLabelEndName() const override {
|
|
if (Group)
|
|
return (SectionName.str() + '_' + Group->getName() + "_end").str();
|
|
return SectionName.str() + "_end";
|
|
}
|
|
unsigned getType() const { return Type; }
|
|
unsigned getFlags() const { return Flags; }
|
|
unsigned getEntrySize() const { return EntrySize; }
|
|
const MCSymbol *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;
|
|
|
|
/// isBaseAddressKnownZero - We know that non-allocatable sections (like
|
|
/// debug info) have a base of zero.
|
|
bool isBaseAddressKnownZero() const override {
|
|
return (getFlags() & ELF::SHF_ALLOC) == 0;
|
|
}
|
|
|
|
static bool classof(const MCSection *S) {
|
|
return S->getVariant() == SV_ELF;
|
|
}
|
|
|
|
// Return the entry size for sections with fixed-width data.
|
|
static unsigned DetermineEntrySize(SectionKind Kind);
|
|
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
#endif
|