llvm-project/llvm/lib/MC/MCContext.cpp

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//===- lib/MC/MCContext.cpp - Machine Code Context ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCContext.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCLabel.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/SourceMgr.h"
#include <map>
using namespace llvm;
MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
const MCObjectFileInfo *mofi, const SourceMgr *mgr,
bool DoAutoReset)
: SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi), Allocator(),
Symbols(Allocator), UsedNames(Allocator), NextUniqueID(0),
CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0), DwarfLocSeen(false),
GenDwarfForAssembly(false), GenDwarfFileNumber(0), DwarfVersion(4),
AllowTemporaryLabels(true), DwarfCompileUnitID(0),
AutoReset(DoAutoReset) {
std::error_code EC = llvm::sys::fs::current_path(CompilationDir);
if (EC)
CompilationDir.clear();
SecureLogFile = getenv("AS_SECURE_LOG_FILE");
SecureLog = nullptr;
SecureLogUsed = false;
if (SrcMgr && SrcMgr->getNumBuffers())
MainFileName =
SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
}
MCContext::~MCContext() {
if (AutoReset)
reset();
// NOTE: The symbols are all allocated out of a bump pointer allocator,
// we don't need to free them here.
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// If the stream for the .secure_log_unique directive was created free it.
delete (raw_ostream*)SecureLog;
}
//===----------------------------------------------------------------------===//
// Module Lifetime Management
//===----------------------------------------------------------------------===//
void MCContext::reset() {
UsedNames.clear();
Symbols.clear();
Allocator.Reset();
Instances.clear();
CompilationDir.clear();
MainFileName.clear();
MCDwarfLineTablesCUMap.clear();
SectionStartEndSyms.clear();
MCGenDwarfLabelEntries.clear();
DwarfDebugFlags = StringRef();
DwarfCompileUnitID = 0;
CurrentDwarfLoc = MCDwarfLoc(0,0,0,DWARF2_FLAG_IS_STMT,0,0);
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MachOUniquingMap.clear();
ELFUniquingMap.clear();
COFFUniquingMap.clear();
NextUniqueID = 0;
AllowTemporaryLabels = true;
DwarfLocSeen = false;
GenDwarfForAssembly = false;
GenDwarfFileNumber = 0;
}
//===----------------------------------------------------------------------===//
// Symbol Manipulation
//===----------------------------------------------------------------------===//
MCSymbol *MCContext::GetOrCreateSymbol(StringRef Name) {
assert(!Name.empty() && "Normal symbols cannot be unnamed!");
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MCSymbol *&Sym = Symbols[Name];
if (!Sym)
Sym = CreateSymbol(Name);
return Sym;
}
MCSymbol *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
MCSymbol *&Sym = SectionSymbols[&Section];
if (Sym)
return Sym;
StringRef Name = Section.getSectionName();
MCSymbol *&OldSym = Symbols[Name];
if (OldSym && OldSym->isUndefined()) {
Sym = OldSym;
return OldSym;
}
auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
Sym = new (*this) MCSymbol(NameIter->getKey(), /*isTemporary*/ false);
if (!OldSym)
OldSym = Sym;
return Sym;
}
MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName) {
return GetOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) +
"frameallocation_" + FuncName);
}
MCSymbol *MCContext::CreateSymbol(StringRef Name) {
// Determine whether this is an assembler temporary or normal label, if used.
bool isTemporary = false;
if (AllowTemporaryLabels)
isTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
auto NameEntry = UsedNames.insert(std::make_pair(Name, true));
if (!NameEntry.second) {
assert(isTemporary && "Cannot rename non-temporary symbols");
SmallString<128> NewName = Name;
do {
NewName.resize(Name.size());
raw_svector_ostream(NewName) << NextUniqueID++;
NameEntry = UsedNames.insert(std::make_pair(NewName, true));
} while (!NameEntry.second);
}
// Ok, the entry doesn't already exist. Have the MCSymbol object itself refer
// to the copy of the string that is embedded in the UsedNames entry.
MCSymbol *Result =
new (*this) MCSymbol(NameEntry.first->getKey(), isTemporary);
return Result;
}
MCSymbol *MCContext::GetOrCreateSymbol(const Twine &Name) {
SmallString<128> NameSV;
return GetOrCreateSymbol(Name.toStringRef(NameSV));
}
MCSymbol *MCContext::CreateLinkerPrivateTempSymbol() {
SmallString<128> NameSV;
raw_svector_ostream(NameSV)
<< MAI->getLinkerPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
return CreateSymbol(NameSV);
}
MCSymbol *MCContext::CreateTempSymbol() {
SmallString<128> NameSV;
raw_svector_ostream(NameSV)
<< MAI->getPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
return CreateSymbol(NameSV);
}
unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
MCLabel *&Label = Instances[LocalLabelVal];
if (!Label)
Label = new (*this) MCLabel(0);
return Label->incInstance();
}
unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
MCLabel *&Label = Instances[LocalLabelVal];
if (!Label)
Label = new (*this) MCLabel(0);
return Label->getInstance();
}
MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
unsigned Instance) {
MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
if (!Sym)
Sym = CreateTempSymbol();
return Sym;
}
MCSymbol *MCContext::CreateDirectionalLocalSymbol(unsigned LocalLabelVal) {
unsigned Instance = NextInstance(LocalLabelVal);
return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
}
MCSymbol *MCContext::GetDirectionalLocalSymbol(unsigned LocalLabelVal,
bool Before) {
unsigned Instance = GetInstance(LocalLabelVal);
if (!Before)
++Instance;
return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
}
MCSymbol *MCContext::LookupSymbol(StringRef Name) const {
return Symbols.lookup(Name);
}
MCSymbol *MCContext::LookupSymbol(const Twine &Name) const {
SmallString<128> NameSV;
Name.toVector(NameSV);
return LookupSymbol(NameSV.str());
}
//===----------------------------------------------------------------------===//
// Section Management
//===----------------------------------------------------------------------===//
const MCSectionMachO *MCContext::
getMachOSection(StringRef Segment, StringRef Section,
unsigned TypeAndAttributes,
unsigned Reserved2, SectionKind Kind) {
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// We unique sections by their segment/section pair. The returned section
// may not have the same flags as the requested section, if so this should be
// diagnosed by the client as an error.
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// Form the name to look up.
SmallString<64> Name;
Name += Segment;
Name.push_back(',');
Name += Section;
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// Do the lookup, if we have a hit, return it.
const MCSectionMachO *&Entry = MachOUniquingMap[Name.str()];
if (Entry) return Entry;
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// Otherwise, return a new section.
return Entry = new (*this) MCSectionMachO(Segment, Section, TypeAndAttributes,
Reserved2, Kind);
}
const MCSectionELF *MCContext::
getELFSection(StringRef Section, unsigned Type, unsigned Flags,
SectionKind Kind) {
return getELFSection(Section, Type, Flags, Kind, 0, "");
}
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. llvm-svn: 205990
2014-04-11 05:53:53 +08:00
void MCContext::renameELFSection(const MCSectionELF *Section, StringRef Name) {
StringRef GroupName;
if (const MCSymbol *Group = Section->getGroup())
GroupName = Group->getName();
ELFUniquingMap.erase(SectionGroupPair(Section->getSectionName(), GroupName));
auto I =
ELFUniquingMap.insert(std::make_pair(SectionGroupPair(Name, GroupName),
Section)).first;
StringRef CachedName = I->first.first;
const_cast<MCSectionELF*>(Section)->setSectionName(CachedName);
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. llvm-svn: 205990
2014-04-11 05:53:53 +08:00
}
const MCSectionELF *MCContext::
getELFSection(StringRef Section, unsigned Type, unsigned Flags,
SectionKind Kind, unsigned EntrySize, StringRef Group) {
// Do the lookup, if we have a hit, return it.
auto IterBool = ELFUniquingMap.insert(
std::make_pair(SectionGroupPair(Section, Group), nullptr));
auto &Entry = *IterBool.first;
if (!IterBool.second) return Entry.second;
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// Possibly refine the entry size first.
if (!EntrySize) {
EntrySize = MCSectionELF::DetermineEntrySize(Kind);
}
MCSymbol *GroupSym = nullptr;
if (!Group.empty())
GroupSym = GetOrCreateSymbol(Group);
StringRef CachedName = Entry.first.first;
MCSectionELF *Result = new (*this)
MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym);
Entry.second = Result;
return Result;
}
const MCSectionELF *MCContext::CreateELFGroupSection() {
MCSectionELF *Result =
new (*this) MCSectionELF(".group", ELF::SHT_GROUP, 0,
SectionKind::getReadOnly(), 4, nullptr);
return Result;
}
const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
unsigned Characteristics,
SectionKind Kind,
StringRef COMDATSymName,
int Selection) {
// Do the lookup, if we have a hit, return it.
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SectionGroupTriple T(Section, COMDATSymName, Selection);
auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
auto Iter = IterBool.first;
if (!IterBool.second)
return Iter->second;
MCSymbol *COMDATSymbol = nullptr;
if (!COMDATSymName.empty())
COMDATSymbol = GetOrCreateSymbol(COMDATSymName);
StringRef CachedName = std::get<0>(Iter->first);
MCSectionCOFF *Result = new (*this)
MCSectionCOFF(CachedName, Characteristics, COMDATSymbol, Selection, Kind);
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Iter->second = Result;
return Result;
}
const MCSectionCOFF *
MCContext::getCOFFSection(StringRef Section, unsigned Characteristics,
SectionKind Kind) {
return getCOFFSection(Section, Characteristics, Kind, "", 0);
}
const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
SectionGroupTriple T(Section, "", 0);
auto Iter = COFFUniquingMap.find(T);
if (Iter == COFFUniquingMap.end())
return nullptr;
return Iter->second;
}
const MCSectionCOFF *
MCContext::getAssociativeCOFFSection(const MCSectionCOFF *Sec,
const MCSymbol *KeySym) {
// Return the normal section if we don't have to be associative.
if (!KeySym)
return Sec;
// Make an associative section with the same name and kind as the normal
// section.
unsigned Characteristics =
Sec->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
KeySym->getName(),
COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
}
//===----------------------------------------------------------------------===//
// Dwarf Management
//===----------------------------------------------------------------------===//
/// GetDwarfFile - takes a file name an number to place in the dwarf file and
/// directory tables. If the file number has already been allocated it is an
/// error and zero is returned and the client reports the error, else the
/// allocated file number is returned. The file numbers may be in any order.
unsigned MCContext::GetDwarfFile(StringRef Directory, StringRef FileName,
unsigned FileNumber, unsigned CUID) {
MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
return Table.getFile(Directory, FileName, FileNumber);
}
/// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
/// currently is assigned and false otherwise.
bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
const SmallVectorImpl<MCDwarfFile>& MCDwarfFiles = getMCDwarfFiles(CUID);
if(FileNumber == 0 || FileNumber >= MCDwarfFiles.size())
return false;
return !MCDwarfFiles[FileNumber].Name.empty();
}
/// finalizeDwarfSections - Emit end symbols for each non-empty code section.
/// Also remove empty sections from SectionStartEndSyms, to avoid generating
/// useless debug info for them.
void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
MCContext &context = MCOS.getContext();
auto sec = SectionStartEndSyms.begin();
while (sec != SectionStartEndSyms.end()) {
assert(sec->second.first && "Start symbol must be set by now");
MCOS.SwitchSection(sec->first);
if (MCOS.mayHaveInstructions()) {
MCSymbol *SectionEndSym = context.CreateTempSymbol();
MCOS.EmitLabel(SectionEndSym);
sec->second.second = SectionEndSym;
++sec;
} else {
MapVector<const MCSection *, std::pair<MCSymbol *, MCSymbol *> >::iterator
to_erase = sec;
sec = SectionStartEndSyms.erase(to_erase);
}
}
}
void MCContext::FatalError(SMLoc Loc, const Twine &Msg) const {
// If we have a source manager and a location, use it. Otherwise just
// use the generic report_fatal_error().
if (!SrcMgr || Loc == SMLoc())
report_fatal_error(Msg, false);
// Use the source manager to print the message.
SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
// If we reached here, we are failing ungracefully. Run the interrupt handlers
// to make sure any special cleanups get done, in particular that we remove
// files registered with RemoveFileOnSignal.
sys::RunInterruptHandlers();
exit(1);
}