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      1 //===- lib/MC/MCContext.cpp - Machine Code Context ------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "llvm/MC/MCContext.h"
     11 #include "llvm/ADT/SmallString.h"
     12 #include "llvm/ADT/Twine.h"
     13 #include "llvm/MC/MCAsmInfo.h"
     14 #include "llvm/MC/MCDwarf.h"
     15 #include "llvm/MC/MCLabel.h"
     16 #include "llvm/MC/MCObjectFileInfo.h"
     17 #include "llvm/MC/MCRegisterInfo.h"
     18 #include "llvm/MC/MCSectionCOFF.h"
     19 #include "llvm/MC/MCSectionELF.h"
     20 #include "llvm/MC/MCSectionMachO.h"
     21 #include "llvm/MC/MCSymbol.h"
     22 #include "llvm/Support/ELF.h"
     23 #include "llvm/Support/ErrorHandling.h"
     24 #include "llvm/Support/FileSystem.h"
     25 #include "llvm/Support/MemoryBuffer.h"
     26 #include "llvm/Support/Signals.h"
     27 #include "llvm/Support/SourceMgr.h"
     28 #include <map>
     29 
     30 using namespace llvm;
     31 
     32 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
     33                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
     34                      bool DoAutoReset)
     35     : SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi), Allocator(),
     36       Symbols(Allocator), UsedNames(Allocator), NextUniqueID(0),
     37       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0), DwarfLocSeen(false),
     38       GenDwarfForAssembly(false), GenDwarfFileNumber(0), DwarfVersion(4),
     39       AllowTemporaryLabels(true), DwarfCompileUnitID(0),
     40       AutoReset(DoAutoReset) {
     41 
     42   std::error_code EC = llvm::sys::fs::current_path(CompilationDir);
     43   if (EC)
     44     CompilationDir.clear();
     45 
     46   SecureLogFile = getenv("AS_SECURE_LOG_FILE");
     47   SecureLog = nullptr;
     48   SecureLogUsed = false;
     49 
     50   if (SrcMgr && SrcMgr->getNumBuffers())
     51     MainFileName =
     52         SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
     53 }
     54 
     55 MCContext::~MCContext() {
     56 
     57   if (AutoReset)
     58     reset();
     59 
     60   // NOTE: The symbols are all allocated out of a bump pointer allocator,
     61   // we don't need to free them here.
     62 
     63   // If the stream for the .secure_log_unique directive was created free it.
     64   delete (raw_ostream*)SecureLog;
     65 }
     66 
     67 //===----------------------------------------------------------------------===//
     68 // Module Lifetime Management
     69 //===----------------------------------------------------------------------===//
     70 
     71 void MCContext::reset() {
     72   UsedNames.clear();
     73   Symbols.clear();
     74   Allocator.Reset();
     75   Instances.clear();
     76   MCDwarfLineTablesCUMap.clear();
     77   MCGenDwarfLabelEntries.clear();
     78   DwarfDebugFlags = StringRef();
     79   DwarfCompileUnitID = 0;
     80   CurrentDwarfLoc = MCDwarfLoc(0,0,0,DWARF2_FLAG_IS_STMT,0,0);
     81 
     82   MachOUniquingMap.clear();
     83   ELFUniquingMap.clear();
     84   COFFUniquingMap.clear();
     85 
     86   NextUniqueID = 0;
     87   AllowTemporaryLabels = true;
     88   DwarfLocSeen = false;
     89   GenDwarfForAssembly = false;
     90   GenDwarfFileNumber = 0;
     91 }
     92 
     93 //===----------------------------------------------------------------------===//
     94 // Symbol Manipulation
     95 //===----------------------------------------------------------------------===//
     96 
     97 MCSymbol *MCContext::GetOrCreateSymbol(StringRef Name) {
     98   assert(!Name.empty() && "Normal symbols cannot be unnamed!");
     99 
    100   // Do the lookup and get the entire StringMapEntry.  We want access to the
    101   // key if we are creating the entry.
    102   StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
    103   MCSymbol *Sym = Entry.getValue();
    104 
    105   if (Sym)
    106     return Sym;
    107 
    108   Sym = CreateSymbol(Name);
    109   Entry.setValue(Sym);
    110   return Sym;
    111 }
    112 
    113 MCSymbol *MCContext::CreateSymbol(StringRef Name) {
    114   // Determine whether this is an assembler temporary or normal label, if used.
    115   bool isTemporary = false;
    116   if (AllowTemporaryLabels)
    117     isTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
    118 
    119   StringMapEntry<bool> *NameEntry = &UsedNames.GetOrCreateValue(Name);
    120   if (NameEntry->getValue()) {
    121     assert(isTemporary && "Cannot rename non-temporary symbols");
    122     SmallString<128> NewName = Name;
    123     do {
    124       NewName.resize(Name.size());
    125       raw_svector_ostream(NewName) << NextUniqueID++;
    126       NameEntry = &UsedNames.GetOrCreateValue(NewName);
    127     } while (NameEntry->getValue());
    128   }
    129   NameEntry->setValue(true);
    130 
    131   // Ok, the entry doesn't already exist.  Have the MCSymbol object itself refer
    132   // to the copy of the string that is embedded in the UsedNames entry.
    133   MCSymbol *Result = new (*this) MCSymbol(NameEntry->getKey(), isTemporary);
    134 
    135   return Result;
    136 }
    137 
    138 MCSymbol *MCContext::GetOrCreateSymbol(const Twine &Name) {
    139   SmallString<128> NameSV;
    140   return GetOrCreateSymbol(Name.toStringRef(NameSV));
    141 }
    142 
    143 MCSymbol *MCContext::CreateLinkerPrivateTempSymbol() {
    144   SmallString<128> NameSV;
    145   raw_svector_ostream(NameSV)
    146     << MAI->getLinkerPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
    147   return CreateSymbol(NameSV);
    148 }
    149 
    150 MCSymbol *MCContext::CreateTempSymbol() {
    151   SmallString<128> NameSV;
    152   raw_svector_ostream(NameSV)
    153     << MAI->getPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
    154   return CreateSymbol(NameSV);
    155 }
    156 
    157 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
    158   MCLabel *&Label = Instances[LocalLabelVal];
    159   if (!Label)
    160     Label = new (*this) MCLabel(0);
    161   return Label->incInstance();
    162 }
    163 
    164 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
    165   MCLabel *&Label = Instances[LocalLabelVal];
    166   if (!Label)
    167     Label = new (*this) MCLabel(0);
    168   return Label->getInstance();
    169 }
    170 
    171 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
    172                                                        unsigned Instance) {
    173   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
    174   if (!Sym)
    175     Sym = CreateTempSymbol();
    176   return Sym;
    177 }
    178 
    179 MCSymbol *MCContext::CreateDirectionalLocalSymbol(unsigned LocalLabelVal) {
    180   unsigned Instance = NextInstance(LocalLabelVal);
    181   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
    182 }
    183 
    184 MCSymbol *MCContext::GetDirectionalLocalSymbol(unsigned LocalLabelVal,
    185                                                bool Before) {
    186   unsigned Instance = GetInstance(LocalLabelVal);
    187   if (!Before)
    188     ++Instance;
    189   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
    190 }
    191 
    192 MCSymbol *MCContext::LookupSymbol(StringRef Name) const {
    193   return Symbols.lookup(Name);
    194 }
    195 
    196 MCSymbol *MCContext::LookupSymbol(const Twine &Name) const {
    197   SmallString<128> NameSV;
    198   Name.toVector(NameSV);
    199   return LookupSymbol(NameSV.str());
    200 }
    201 
    202 //===----------------------------------------------------------------------===//
    203 // Section Management
    204 //===----------------------------------------------------------------------===//
    205 
    206 const MCSectionMachO *MCContext::
    207 getMachOSection(StringRef Segment, StringRef Section,
    208                 unsigned TypeAndAttributes,
    209                 unsigned Reserved2, SectionKind Kind) {
    210 
    211   // We unique sections by their segment/section pair.  The returned section
    212   // may not have the same flags as the requested section, if so this should be
    213   // diagnosed by the client as an error.
    214 
    215   // Form the name to look up.
    216   SmallString<64> Name;
    217   Name += Segment;
    218   Name.push_back(',');
    219   Name += Section;
    220 
    221   // Do the lookup, if we have a hit, return it.
    222   const MCSectionMachO *&Entry = MachOUniquingMap[Name.str()];
    223   if (Entry) return Entry;
    224 
    225   // Otherwise, return a new section.
    226   return Entry = new (*this) MCSectionMachO(Segment, Section, TypeAndAttributes,
    227                                             Reserved2, Kind);
    228 }
    229 
    230 const MCSectionELF *MCContext::
    231 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
    232               SectionKind Kind) {
    233   return getELFSection(Section, Type, Flags, Kind, 0, "");
    234 }
    235 
    236 void MCContext::renameELFSection(const MCSectionELF *Section, StringRef Name) {
    237   StringRef GroupName;
    238   if (const MCSymbol *Group = Section->getGroup())
    239     GroupName = Group->getName();
    240 
    241   ELFUniquingMap.erase(SectionGroupPair(Section->getSectionName(), GroupName));
    242   auto I =
    243       ELFUniquingMap.insert(std::make_pair(SectionGroupPair(Name, GroupName),
    244                                            Section)).first;
    245   StringRef CachedName = I->first.first;
    246   const_cast<MCSectionELF*>(Section)->setSectionName(CachedName);
    247 }
    248 
    249 const MCSectionELF *MCContext::
    250 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
    251               SectionKind Kind, unsigned EntrySize, StringRef Group) {
    252   // Do the lookup, if we have a hit, return it.
    253   auto IterBool = ELFUniquingMap.insert(
    254       std::make_pair(SectionGroupPair(Section, Group), nullptr));
    255   auto &Entry = *IterBool.first;
    256   if (!IterBool.second) return Entry.second;
    257 
    258   // Possibly refine the entry size first.
    259   if (!EntrySize) {
    260     EntrySize = MCSectionELF::DetermineEntrySize(Kind);
    261   }
    262 
    263   MCSymbol *GroupSym = nullptr;
    264   if (!Group.empty())
    265     GroupSym = GetOrCreateSymbol(Group);
    266 
    267   StringRef CachedName = Entry.first.first;
    268   MCSectionELF *Result = new (*this)
    269       MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym);
    270   Entry.second = Result;
    271   return Result;
    272 }
    273 
    274 const MCSectionELF *MCContext::CreateELFGroupSection() {
    275   MCSectionELF *Result =
    276     new (*this) MCSectionELF(".group", ELF::SHT_GROUP, 0,
    277                              SectionKind::getReadOnly(), 4, nullptr);
    278   return Result;
    279 }
    280 
    281 const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
    282                                                unsigned Characteristics,
    283                                                SectionKind Kind,
    284                                                StringRef COMDATSymName,
    285                                                int Selection) {
    286   // Do the lookup, if we have a hit, return it.
    287 
    288   SectionGroupTriple T(Section, COMDATSymName, Selection);
    289   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
    290   auto Iter = IterBool.first;
    291   if (!IterBool.second)
    292     return Iter->second;
    293 
    294   const MCSymbol *COMDATSymbol = nullptr;
    295   if (!COMDATSymName.empty())
    296     COMDATSymbol = GetOrCreateSymbol(COMDATSymName);
    297 
    298   StringRef CachedName = std::get<0>(Iter->first);
    299   MCSectionCOFF *Result = new (*this)
    300       MCSectionCOFF(CachedName, Characteristics, COMDATSymbol, Selection, Kind);
    301 
    302   Iter->second = Result;
    303   return Result;
    304 }
    305 
    306 const MCSectionCOFF *
    307 MCContext::getCOFFSection(StringRef Section, unsigned Characteristics,
    308                           SectionKind Kind) {
    309   return getCOFFSection(Section, Characteristics, Kind, "", 0);
    310 }
    311 
    312 const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
    313   SectionGroupTriple T(Section, "", 0);
    314   auto Iter = COFFUniquingMap.find(T);
    315   if (Iter == COFFUniquingMap.end())
    316     return nullptr;
    317   return Iter->second;
    318 }
    319 
    320 //===----------------------------------------------------------------------===//
    321 // Dwarf Management
    322 //===----------------------------------------------------------------------===//
    323 
    324 /// GetDwarfFile - takes a file name an number to place in the dwarf file and
    325 /// directory tables.  If the file number has already been allocated it is an
    326 /// error and zero is returned and the client reports the error, else the
    327 /// allocated file number is returned.  The file numbers may be in any order.
    328 unsigned MCContext::GetDwarfFile(StringRef Directory, StringRef FileName,
    329                                  unsigned FileNumber, unsigned CUID) {
    330   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
    331   return Table.getFile(Directory, FileName, FileNumber);
    332 }
    333 
    334 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
    335 /// currently is assigned and false otherwise.
    336 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
    337   const SmallVectorImpl<MCDwarfFile>& MCDwarfFiles = getMCDwarfFiles(CUID);
    338   if(FileNumber == 0 || FileNumber >= MCDwarfFiles.size())
    339     return false;
    340 
    341   return !MCDwarfFiles[FileNumber].Name.empty();
    342 }
    343 
    344 /// finalizeDwarfSections - Emit end symbols for each non-empty code section.
    345 /// Also remove empty sections from SectionStartEndSyms, to avoid generating
    346 /// useless debug info for them.
    347 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
    348   MCContext &context = MCOS.getContext();
    349 
    350   auto sec = SectionStartEndSyms.begin();
    351   while (sec != SectionStartEndSyms.end()) {
    352     assert(sec->second.first && "Start symbol must be set by now");
    353     MCOS.SwitchSection(sec->first);
    354     if (MCOS.mayHaveInstructions()) {
    355       MCSymbol *SectionEndSym = context.CreateTempSymbol();
    356       MCOS.EmitLabel(SectionEndSym);
    357       sec->second.second = SectionEndSym;
    358       ++sec;
    359     } else {
    360       MapVector<const MCSection *, std::pair<MCSymbol *, MCSymbol *> >::iterator
    361         to_erase = sec;
    362       sec = SectionStartEndSyms.erase(to_erase);
    363     }
    364   }
    365 }
    366 
    367 void MCContext::FatalError(SMLoc Loc, const Twine &Msg) const {
    368   // If we have a source manager and a location, use it. Otherwise just
    369   // use the generic report_fatal_error().
    370   if (!SrcMgr || Loc == SMLoc())
    371     report_fatal_error(Msg, false);
    372 
    373   // Use the source manager to print the message.
    374   SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
    375 
    376   // If we reached here, we are failing ungracefully. Run the interrupt handlers
    377   // to make sure any special cleanups get done, in particular that we remove
    378   // files registered with RemoveFileOnSignal.
    379   sys::RunInterruptHandlers();
    380   exit(1);
    381 }
    382