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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/MC/MCAsmInfo.h"
     12 #include "llvm/MC/MCObjectFileInfo.h"
     13 #include "llvm/MC/MCRegisterInfo.h"
     14 #include "llvm/MC/MCSectionMachO.h"
     15 #include "llvm/MC/MCSectionELF.h"
     16 #include "llvm/MC/MCSectionCOFF.h"
     17 #include "llvm/MC/MCSymbol.h"
     18 #include "llvm/MC/MCLabel.h"
     19 #include "llvm/MC/MCDwarf.h"
     20 #include "llvm/Target/TargetAsmInfo.h"
     21 #include "llvm/ADT/SmallString.h"
     22 #include "llvm/ADT/Twine.h"
     23 #include "llvm/Support/ELF.h"
     24 using namespace llvm;
     25 
     26 typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
     27 typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
     28 typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
     29 
     30 
     31 MCContext::MCContext(const MCAsmInfo &mai, const MCRegisterInfo &mri,
     32                      const MCObjectFileInfo *mofi, const TargetAsmInfo *tai) :
     33   MAI(mai), MRI(mri), MOFI(mofi), TAI(tai),
     34   Allocator(), Symbols(Allocator), UsedNames(Allocator),
     35   NextUniqueID(0),
     36   CurrentDwarfLoc(0,0,0,DWARF2_FLAG_IS_STMT,0,0),
     37   AllowTemporaryLabels(true) {
     38   MachOUniquingMap = 0;
     39   ELFUniquingMap = 0;
     40   COFFUniquingMap = 0;
     41 
     42   SecureLogFile = getenv("AS_SECURE_LOG_FILE");
     43   SecureLog = 0;
     44   SecureLogUsed = false;
     45 
     46   DwarfLocSeen = false;
     47 }
     48 
     49 MCContext::~MCContext() {
     50   // NOTE: The symbols are all allocated out of a bump pointer allocator,
     51   // we don't need to free them here.
     52 
     53   // If we have the MachO uniquing map, free it.
     54   delete (MachOUniqueMapTy*)MachOUniquingMap;
     55   delete (ELFUniqueMapTy*)ELFUniquingMap;
     56   delete (COFFUniqueMapTy*)COFFUniquingMap;
     57 
     58   // If the stream for the .secure_log_unique directive was created free it.
     59   delete (raw_ostream*)SecureLog;
     60 
     61   delete TAI;
     62 }
     63 
     64 //===----------------------------------------------------------------------===//
     65 // Symbol Manipulation
     66 //===----------------------------------------------------------------------===//
     67 
     68 MCSymbol *MCContext::GetOrCreateSymbol(StringRef Name) {
     69   assert(!Name.empty() && "Normal symbols cannot be unnamed!");
     70 
     71   // Do the lookup and get the entire StringMapEntry.  We want access to the
     72   // key if we are creating the entry.
     73   StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
     74   MCSymbol *Sym = Entry.getValue();
     75 
     76   if (Sym)
     77     return Sym;
     78 
     79   Sym = CreateSymbol(Name);
     80   Entry.setValue(Sym);
     81   return Sym;
     82 }
     83 
     84 MCSymbol *MCContext::CreateSymbol(StringRef Name) {
     85   // Determine whether this is an assembler temporary or normal label, if used.
     86   bool isTemporary = false;
     87   if (AllowTemporaryLabels)
     88     isTemporary = Name.startswith(MAI.getPrivateGlobalPrefix());
     89 
     90   StringMapEntry<bool> *NameEntry = &UsedNames.GetOrCreateValue(Name);
     91   if (NameEntry->getValue()) {
     92     assert(isTemporary && "Cannot rename non temporary symbols");
     93     SmallString<128> NewName = Name;
     94     do {
     95       NewName.resize(Name.size());
     96       raw_svector_ostream(NewName) << NextUniqueID++;
     97       NameEntry = &UsedNames.GetOrCreateValue(NewName);
     98     } while (NameEntry->getValue());
     99   }
    100   NameEntry->setValue(true);
    101 
    102   // Ok, the entry doesn't already exist.  Have the MCSymbol object itself refer
    103   // to the copy of the string that is embedded in the UsedNames entry.
    104   MCSymbol *Result = new (*this) MCSymbol(NameEntry->getKey(), isTemporary);
    105 
    106   return Result;
    107 }
    108 
    109 MCSymbol *MCContext::GetOrCreateSymbol(const Twine &Name) {
    110   SmallString<128> NameSV;
    111   Name.toVector(NameSV);
    112   return GetOrCreateSymbol(NameSV.str());
    113 }
    114 
    115 MCSymbol *MCContext::CreateTempSymbol() {
    116   SmallString<128> NameSV;
    117   raw_svector_ostream(NameSV)
    118     << MAI.getPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
    119   return CreateSymbol(NameSV);
    120 }
    121 
    122 unsigned MCContext::NextInstance(int64_t LocalLabelVal) {
    123   MCLabel *&Label = Instances[LocalLabelVal];
    124   if (!Label)
    125     Label = new (*this) MCLabel(0);
    126   return Label->incInstance();
    127 }
    128 
    129 unsigned MCContext::GetInstance(int64_t LocalLabelVal) {
    130   MCLabel *&Label = Instances[LocalLabelVal];
    131   if (!Label)
    132     Label = new (*this) MCLabel(0);
    133   return Label->getInstance();
    134 }
    135 
    136 MCSymbol *MCContext::CreateDirectionalLocalSymbol(int64_t LocalLabelVal) {
    137   return GetOrCreateSymbol(Twine(MAI.getPrivateGlobalPrefix()) +
    138                            Twine(LocalLabelVal) +
    139                            "\2" +
    140                            Twine(NextInstance(LocalLabelVal)));
    141 }
    142 MCSymbol *MCContext::GetDirectionalLocalSymbol(int64_t LocalLabelVal,
    143                                                int bORf) {
    144   return GetOrCreateSymbol(Twine(MAI.getPrivateGlobalPrefix()) +
    145                            Twine(LocalLabelVal) +
    146                            "\2" +
    147                            Twine(GetInstance(LocalLabelVal) + bORf));
    148 }
    149 
    150 MCSymbol *MCContext::LookupSymbol(StringRef Name) const {
    151   return Symbols.lookup(Name);
    152 }
    153 
    154 //===----------------------------------------------------------------------===//
    155 // Section Management
    156 //===----------------------------------------------------------------------===//
    157 
    158 const MCSectionMachO *MCContext::
    159 getMachOSection(StringRef Segment, StringRef Section,
    160                 unsigned TypeAndAttributes,
    161                 unsigned Reserved2, SectionKind Kind) {
    162 
    163   // We unique sections by their segment/section pair.  The returned section
    164   // may not have the same flags as the requested section, if so this should be
    165   // diagnosed by the client as an error.
    166 
    167   // Create the map if it doesn't already exist.
    168   if (MachOUniquingMap == 0)
    169     MachOUniquingMap = new MachOUniqueMapTy();
    170   MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)MachOUniquingMap;
    171 
    172   // Form the name to look up.
    173   SmallString<64> Name;
    174   Name += Segment;
    175   Name.push_back(',');
    176   Name += Section;
    177 
    178   // Do the lookup, if we have a hit, return it.
    179   const MCSectionMachO *&Entry = Map[Name.str()];
    180   if (Entry) return Entry;
    181 
    182   // Otherwise, return a new section.
    183   return Entry = new (*this) MCSectionMachO(Segment, Section, TypeAndAttributes,
    184                                             Reserved2, Kind);
    185 }
    186 
    187 const MCSectionELF *MCContext::
    188 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
    189               SectionKind Kind) {
    190   return getELFSection(Section, Type, Flags, Kind, 0, "");
    191 }
    192 
    193 const MCSectionELF *MCContext::
    194 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
    195               SectionKind Kind, unsigned EntrySize, StringRef Group) {
    196   if (ELFUniquingMap == 0)
    197     ELFUniquingMap = new ELFUniqueMapTy();
    198   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)ELFUniquingMap;
    199 
    200   // Do the lookup, if we have a hit, return it.
    201   StringMapEntry<const MCSectionELF*> &Entry = Map.GetOrCreateValue(Section);
    202   if (Entry.getValue()) return Entry.getValue();
    203 
    204   // Possibly refine the entry size first.
    205   if (!EntrySize) {
    206     EntrySize = MCSectionELF::DetermineEntrySize(Kind);
    207   }
    208 
    209   MCSymbol *GroupSym = NULL;
    210   if (!Group.empty())
    211     GroupSym = GetOrCreateSymbol(Group);
    212 
    213   MCSectionELF *Result = new (*this) MCSectionELF(Entry.getKey(), Type, Flags,
    214                                                   Kind, EntrySize, GroupSym);
    215   Entry.setValue(Result);
    216   return Result;
    217 }
    218 
    219 const MCSectionELF *MCContext::CreateELFGroupSection() {
    220   MCSectionELF *Result =
    221     new (*this) MCSectionELF(".group", ELF::SHT_GROUP, 0,
    222                              SectionKind::getReadOnly(), 4, NULL);
    223   return Result;
    224 }
    225 
    226 const MCSection *MCContext::getCOFFSection(StringRef Section,
    227                                            unsigned Characteristics,
    228                                            int Selection,
    229                                            SectionKind Kind) {
    230   if (COFFUniquingMap == 0)
    231     COFFUniquingMap = new COFFUniqueMapTy();
    232   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)COFFUniquingMap;
    233 
    234   // Do the lookup, if we have a hit, return it.
    235   StringMapEntry<const MCSectionCOFF*> &Entry = Map.GetOrCreateValue(Section);
    236   if (Entry.getValue()) return Entry.getValue();
    237 
    238   MCSectionCOFF *Result = new (*this) MCSectionCOFF(Entry.getKey(),
    239                                                     Characteristics,
    240                                                     Selection, Kind);
    241 
    242   Entry.setValue(Result);
    243   return Result;
    244 }
    245 
    246 //===----------------------------------------------------------------------===//
    247 // Dwarf Management
    248 //===----------------------------------------------------------------------===//
    249 
    250 /// GetDwarfFile - takes a file name an number to place in the dwarf file and
    251 /// directory tables.  If the file number has already been allocated it is an
    252 /// error and zero is returned and the client reports the error, else the
    253 /// allocated file number is returned.  The file numbers may be in any order.
    254 unsigned MCContext::GetDwarfFile(StringRef FileName, unsigned FileNumber) {
    255   // TODO: a FileNumber of zero says to use the next available file number.
    256   // Note: in GenericAsmParser::ParseDirectiveFile() FileNumber was checked
    257   // to not be less than one.  This needs to be change to be not less than zero.
    258 
    259   // Make space for this FileNumber in the MCDwarfFiles vector if needed.
    260   if (FileNumber >= MCDwarfFiles.size()) {
    261     MCDwarfFiles.resize(FileNumber + 1);
    262   } else {
    263     MCDwarfFile *&ExistingFile = MCDwarfFiles[FileNumber];
    264     if (ExistingFile)
    265       // It is an error to use see the same number more than once.
    266       return 0;
    267   }
    268 
    269   // Get the new MCDwarfFile slot for this FileNumber.
    270   MCDwarfFile *&File = MCDwarfFiles[FileNumber];
    271 
    272   // Separate the directory part from the basename of the FileName.
    273   std::pair<StringRef, StringRef> Slash = FileName.rsplit('/');
    274 
    275   // Find or make a entry in the MCDwarfDirs vector for this Directory.
    276   StringRef Name;
    277   unsigned DirIndex;
    278   // Capture directory name.
    279   if (Slash.second.empty()) {
    280     Name = Slash.first;
    281     DirIndex = 0; // For FileNames with no directories a DirIndex of 0 is used.
    282   } else {
    283     StringRef Directory = Slash.first;
    284     Name = Slash.second;
    285     for (DirIndex = 0; DirIndex < MCDwarfDirs.size(); DirIndex++) {
    286       if (Directory == MCDwarfDirs[DirIndex])
    287         break;
    288     }
    289     if (DirIndex >= MCDwarfDirs.size()) {
    290       char *Buf = static_cast<char *>(Allocate(Directory.size()));
    291       memcpy(Buf, Directory.data(), Directory.size());
    292       MCDwarfDirs.push_back(StringRef(Buf, Directory.size()));
    293     }
    294     // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
    295     // no directories.  MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
    296     // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames are
    297     // stored at MCDwarfFiles[FileNumber].Name .
    298     DirIndex++;
    299   }
    300 
    301   // Now make the MCDwarfFile entry and place it in the slot in the MCDwarfFiles
    302   // vector.
    303   char *Buf = static_cast<char *>(Allocate(Name.size()));
    304   memcpy(Buf, Name.data(), Name.size());
    305   File = new (*this) MCDwarfFile(StringRef(Buf, Name.size()), DirIndex);
    306 
    307   // return the allocated FileNumber.
    308   return FileNumber;
    309 }
    310 
    311 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
    312 /// currently is assigned and false otherwise.
    313 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber) {
    314   if(FileNumber == 0 || FileNumber >= MCDwarfFiles.size())
    315     return false;
    316 
    317   return MCDwarfFiles[FileNumber] != 0;
    318 }
    319