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      1 //===-- LTOModule.cpp - LLVM Link Time Optimizer --------------------------===//
      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 // This file implements the Link Time Optimization library. This library is
     11 // intended to be used by linker to optimize code at link time.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "LTOModule.h"
     16 
     17 #include "llvm/Constants.h"
     18 #include "llvm/LLVMContext.h"
     19 #include "llvm/Module.h"
     20 #include "llvm/ADT/OwningPtr.h"
     21 #include "llvm/ADT/Triple.h"
     22 #include "llvm/Bitcode/ReaderWriter.h"
     23 #include "llvm/Support/SystemUtils.h"
     24 #include "llvm/Support/MemoryBuffer.h"
     25 #include "llvm/Support/MathExtras.h"
     26 #include "llvm/Support/Host.h"
     27 #include "llvm/Support/Path.h"
     28 #include "llvm/Support/Process.h"
     29 #include "llvm/Support/SourceMgr.h"
     30 #include "llvm/Support/TargetRegistry.h"
     31 #include "llvm/Support/TargetSelect.h"
     32 #include "llvm/Support/system_error.h"
     33 #include "llvm/Target/Mangler.h"
     34 #include "llvm/MC/MCAsmInfo.h"
     35 #include "llvm/MC/MCContext.h"
     36 #include "llvm/MC/MCExpr.h"
     37 #include "llvm/MC/MCInst.h"
     38 #include "llvm/MC/MCParser/MCAsmParser.h"
     39 #include "llvm/MC/MCStreamer.h"
     40 #include "llvm/MC/MCSubtargetInfo.h"
     41 #include "llvm/MC/MCSymbol.h"
     42 #include "llvm/MC/SubtargetFeature.h"
     43 #include "llvm/MC/MCTargetAsmParser.h"
     44 #include "llvm/Target/TargetMachine.h"
     45 #include "llvm/Target/TargetRegisterInfo.h"
     46 
     47 using namespace llvm;
     48 
     49 bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
     50   return llvm::sys::IdentifyFileType((char*)mem, length)
     51     == llvm::sys::Bitcode_FileType;
     52 }
     53 
     54 bool LTOModule::isBitcodeFile(const char *path) {
     55   return llvm::sys::Path(path).isBitcodeFile();
     56 }
     57 
     58 bool LTOModule::isBitcodeFileForTarget(const void *mem, size_t length,
     59                                        const char *triplePrefix) {
     60   MemoryBuffer *buffer = makeBuffer(mem, length);
     61   if (!buffer)
     62     return false;
     63   return isTargetMatch(buffer, triplePrefix);
     64 }
     65 
     66 
     67 bool LTOModule::isBitcodeFileForTarget(const char *path,
     68                                        const char *triplePrefix) {
     69   OwningPtr<MemoryBuffer> buffer;
     70   if (MemoryBuffer::getFile(path, buffer))
     71     return false;
     72   return isTargetMatch(buffer.take(), triplePrefix);
     73 }
     74 
     75 // Takes ownership of buffer.
     76 bool LTOModule::isTargetMatch(MemoryBuffer *buffer, const char *triplePrefix) {
     77   std::string Triple = getBitcodeTargetTriple(buffer, getGlobalContext());
     78   delete buffer;
     79   return (strncmp(Triple.c_str(), triplePrefix,
     80  		  strlen(triplePrefix)) == 0);
     81 }
     82 
     83 
     84 LTOModule::LTOModule(Module *m, TargetMachine *t)
     85   : _module(m), _target(t)
     86 {
     87 }
     88 
     89 LTOModule *LTOModule::makeLTOModule(const char *path,
     90                                     std::string &errMsg) {
     91   OwningPtr<MemoryBuffer> buffer;
     92   if (error_code ec = MemoryBuffer::getFile(path, buffer)) {
     93     errMsg = ec.message();
     94     return NULL;
     95   }
     96   return makeLTOModule(buffer.take(), errMsg);
     97 }
     98 
     99 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    100                                     size_t size,
    101                                     std::string &errMsg) {
    102   return makeLTOModule(fd, path, size, size, 0, errMsg);
    103 }
    104 
    105 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    106                                     size_t file_size,
    107                                     size_t map_size,
    108                                     off_t offset,
    109                                     std::string &errMsg) {
    110   OwningPtr<MemoryBuffer> buffer;
    111   if (error_code ec = MemoryBuffer::getOpenFile(fd, path, buffer, file_size,
    112                                                 map_size, offset, false)) {
    113     errMsg = ec.message();
    114     return NULL;
    115   }
    116   return makeLTOModule(buffer.take(), errMsg);
    117 }
    118 
    119 /// makeBuffer - Create a MemoryBuffer from a memory range.
    120 MemoryBuffer *LTOModule::makeBuffer(const void *mem, size_t length) {
    121   const char *startPtr = (char*)mem;
    122   return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), "", false);
    123 }
    124 
    125 
    126 LTOModule *LTOModule::makeLTOModule(const void *mem, size_t length,
    127                                     std::string &errMsg) {
    128   OwningPtr<MemoryBuffer> buffer(makeBuffer(mem, length));
    129   if (!buffer)
    130     return NULL;
    131   return makeLTOModule(buffer.take(), errMsg);
    132 }
    133 
    134 LTOModule *LTOModule::makeLTOModule(MemoryBuffer *buffer,
    135                                     std::string &errMsg) {
    136   static bool Initialized = false;
    137   if (!Initialized) {
    138     InitializeAllTargets();
    139     InitializeAllTargetMCs();
    140     InitializeAllAsmParsers();
    141     Initialized = true;
    142   }
    143 
    144   // parse bitcode buffer
    145   OwningPtr<Module> m(getLazyBitcodeModule(buffer, getGlobalContext(),
    146                                            &errMsg));
    147   if (!m) {
    148     delete buffer;
    149     return NULL;
    150   }
    151 
    152   std::string Triple = m->getTargetTriple();
    153   if (Triple.empty())
    154     Triple = sys::getHostTriple();
    155 
    156   // find machine architecture for this module
    157   const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
    158   if (!march)
    159     return NULL;
    160 
    161   // construct LTOModule, hand over ownership of module and target
    162   SubtargetFeatures Features;
    163   Features.getDefaultSubtargetFeatures(llvm::Triple(Triple));
    164   std::string FeatureStr = Features.getString();
    165   std::string CPU;
    166   TargetMachine *target = march->createTargetMachine(Triple, CPU, FeatureStr);
    167   LTOModule *Ret = new LTOModule(m.take(), target);
    168   bool Err = Ret->ParseSymbols(errMsg);
    169   if (Err) {
    170     delete Ret;
    171     return NULL;
    172   }
    173   return Ret;
    174 }
    175 
    176 
    177 const char *LTOModule::getTargetTriple() {
    178   return _module->getTargetTriple().c_str();
    179 }
    180 
    181 void LTOModule::setTargetTriple(const char *triple) {
    182   _module->setTargetTriple(triple);
    183 }
    184 
    185 void LTOModule::addDefinedFunctionSymbol(Function *f, Mangler &mangler) {
    186   // add to list of defined symbols
    187   addDefinedSymbol(f, mangler, true);
    188 }
    189 
    190 // Get string that data pointer points to.
    191 bool LTOModule::objcClassNameFromExpression(Constant *c, std::string &name) {
    192   if (ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
    193     Constant *op = ce->getOperand(0);
    194     if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
    195       Constant *cn = gvn->getInitializer();
    196       if (ConstantArray *ca = dyn_cast<ConstantArray>(cn)) {
    197         if (ca->isCString()) {
    198           name = ".objc_class_name_" + ca->getAsCString();
    199           return true;
    200         }
    201       }
    202     }
    203   }
    204   return false;
    205 }
    206 
    207 // Parse i386/ppc ObjC class data structure.
    208 void LTOModule::addObjCClass(GlobalVariable *clgv) {
    209   if (ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer())) {
    210     // second slot in __OBJC,__class is pointer to superclass name
    211     std::string superclassName;
    212     if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
    213       NameAndAttributes info;
    214       StringMap<NameAndAttributes>::value_type &entry =
    215         _undefines.GetOrCreateValue(superclassName);
    216       if (!entry.getValue().name) {
    217         const char *symbolName = entry.getKey().data();
    218         info.name = symbolName;
    219         info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    220         entry.setValue(info);
    221       }
    222     }
    223     // third slot in __OBJC,__class is pointer to class name
    224     std::string className;
    225     if (objcClassNameFromExpression(c->getOperand(2), className)) {
    226       StringSet::value_type &entry =
    227         _defines.GetOrCreateValue(className);
    228       entry.setValue(1);
    229       NameAndAttributes info;
    230       info.name = entry.getKey().data();
    231       info.attributes = (lto_symbol_attributes)
    232         (LTO_SYMBOL_PERMISSIONS_DATA |
    233          LTO_SYMBOL_DEFINITION_REGULAR |
    234          LTO_SYMBOL_SCOPE_DEFAULT);
    235       _symbols.push_back(info);
    236     }
    237   }
    238 }
    239 
    240 
    241 // Parse i386/ppc ObjC category data structure.
    242 void LTOModule::addObjCCategory(GlobalVariable *clgv) {
    243   if (ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer())) {
    244     // second slot in __OBJC,__category is pointer to target class name
    245     std::string targetclassName;
    246     if (objcClassNameFromExpression(c->getOperand(1), targetclassName)) {
    247       NameAndAttributes info;
    248 
    249       StringMap<NameAndAttributes>::value_type &entry =
    250         _undefines.GetOrCreateValue(targetclassName);
    251 
    252       if (entry.getValue().name)
    253         return;
    254 
    255       const char *symbolName = entry.getKey().data();
    256       info.name = symbolName;
    257       info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    258       entry.setValue(info);
    259     }
    260   }
    261 }
    262 
    263 
    264 // Parse i386/ppc ObjC class list data structure.
    265 void LTOModule::addObjCClassRef(GlobalVariable *clgv) {
    266   std::string targetclassName;
    267   if (objcClassNameFromExpression(clgv->getInitializer(), targetclassName)) {
    268     NameAndAttributes info;
    269 
    270     StringMap<NameAndAttributes>::value_type &entry =
    271       _undefines.GetOrCreateValue(targetclassName);
    272     if (entry.getValue().name)
    273       return;
    274 
    275     const char *symbolName = entry.getKey().data();
    276     info.name = symbolName;
    277     info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    278     entry.setValue(info);
    279   }
    280 }
    281 
    282 
    283 void LTOModule::addDefinedDataSymbol(GlobalValue *v, Mangler &mangler) {
    284   // Add to list of defined symbols.
    285   addDefinedSymbol(v, mangler, false);
    286 
    287   // Special case i386/ppc ObjC data structures in magic sections:
    288   // The issue is that the old ObjC object format did some strange
    289   // contortions to avoid real linker symbols.  For instance, the
    290   // ObjC class data structure is allocated statically in the executable
    291   // that defines that class.  That data structures contains a pointer to
    292   // its superclass.  But instead of just initializing that part of the
    293   // struct to the address of its superclass, and letting the static and
    294   // dynamic linkers do the rest, the runtime works by having that field
    295   // instead point to a C-string that is the name of the superclass.
    296   // At runtime the objc initialization updates that pointer and sets
    297   // it to point to the actual super class.  As far as the linker
    298   // knows it is just a pointer to a string.  But then someone wanted the
    299   // linker to issue errors at build time if the superclass was not found.
    300   // So they figured out a way in mach-o object format to use an absolute
    301   // symbols (.objc_class_name_Foo = 0) and a floating reference
    302   // (.reference .objc_class_name_Bar) to cause the linker into erroring when
    303   // a class was missing.
    304   // The following synthesizes the implicit .objc_* symbols for the linker
    305   // from the ObjC data structures generated by the front end.
    306   if (v->hasSection() /* && isTargetDarwin */) {
    307     // special case if this data blob is an ObjC class definition
    308     if (v->getSection().compare(0, 15, "__OBJC,__class,") == 0) {
    309       if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    310         addObjCClass(gv);
    311       }
    312     }
    313 
    314     // special case if this data blob is an ObjC category definition
    315     else if (v->getSection().compare(0, 18, "__OBJC,__category,") == 0) {
    316       if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    317         addObjCCategory(gv);
    318       }
    319     }
    320 
    321     // special case if this data blob is the list of referenced classes
    322     else if (v->getSection().compare(0, 18, "__OBJC,__cls_refs,") == 0) {
    323       if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    324         addObjCClassRef(gv);
    325       }
    326     }
    327   }
    328 }
    329 
    330 
    331 void LTOModule::addDefinedSymbol(GlobalValue *def, Mangler &mangler,
    332                                  bool isFunction) {
    333   // ignore all llvm.* symbols
    334   if (def->getName().startswith("llvm."))
    335     return;
    336 
    337   // string is owned by _defines
    338   SmallString<64> Buffer;
    339   mangler.getNameWithPrefix(Buffer, def, false);
    340 
    341   // set alignment part log2() can have rounding errors
    342   uint32_t align = def->getAlignment();
    343   uint32_t attr = align ? CountTrailingZeros_32(def->getAlignment()) : 0;
    344 
    345   // set permissions part
    346   if (isFunction)
    347     attr |= LTO_SYMBOL_PERMISSIONS_CODE;
    348   else {
    349     GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
    350     if (gv && gv->isConstant())
    351       attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
    352     else
    353       attr |= LTO_SYMBOL_PERMISSIONS_DATA;
    354   }
    355 
    356   // set definition part
    357   if (def->hasWeakLinkage() || def->hasLinkOnceLinkage() ||
    358       def->hasLinkerPrivateWeakLinkage() ||
    359       def->hasLinkerPrivateWeakDefAutoLinkage())
    360     attr |= LTO_SYMBOL_DEFINITION_WEAK;
    361   else if (def->hasCommonLinkage())
    362     attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
    363   else
    364     attr |= LTO_SYMBOL_DEFINITION_REGULAR;
    365 
    366   // set scope part
    367   if (def->hasHiddenVisibility())
    368     attr |= LTO_SYMBOL_SCOPE_HIDDEN;
    369   else if (def->hasProtectedVisibility())
    370     attr |= LTO_SYMBOL_SCOPE_PROTECTED;
    371   else if (def->hasExternalLinkage() || def->hasWeakLinkage() ||
    372            def->hasLinkOnceLinkage() || def->hasCommonLinkage() ||
    373            def->hasLinkerPrivateWeakLinkage())
    374     attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    375   else if (def->hasLinkerPrivateWeakDefAutoLinkage())
    376     attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
    377   else
    378     attr |= LTO_SYMBOL_SCOPE_INTERNAL;
    379 
    380   // add to table of symbols
    381   NameAndAttributes info;
    382   StringSet::value_type &entry = _defines.GetOrCreateValue(Buffer);
    383   entry.setValue(1);
    384 
    385   StringRef Name = entry.getKey();
    386   info.name = Name.data();
    387   assert(info.name[Name.size()] == '\0');
    388   info.attributes = (lto_symbol_attributes)attr;
    389   _symbols.push_back(info);
    390 }
    391 
    392 void LTOModule::addAsmGlobalSymbol(const char *name,
    393                                    lto_symbol_attributes scope) {
    394   StringSet::value_type &entry = _defines.GetOrCreateValue(name);
    395 
    396   // only add new define if not already defined
    397   if (entry.getValue())
    398     return;
    399 
    400   entry.setValue(1);
    401   const char *symbolName = entry.getKey().data();
    402   uint32_t attr = LTO_SYMBOL_DEFINITION_REGULAR;
    403   attr |= scope;
    404   NameAndAttributes info;
    405   info.name = symbolName;
    406   info.attributes = (lto_symbol_attributes)attr;
    407   _symbols.push_back(info);
    408 }
    409 
    410 void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
    411   StringMap<NameAndAttributes>::value_type &entry =
    412     _undefines.GetOrCreateValue(name);
    413 
    414   _asm_undefines.push_back(entry.getKey().data());
    415 
    416   // we already have the symbol
    417   if (entry.getValue().name)
    418     return;
    419 
    420   uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;;
    421   attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    422   NameAndAttributes info;
    423   info.name = entry.getKey().data();
    424   info.attributes = (lto_symbol_attributes)attr;
    425 
    426   entry.setValue(info);
    427 }
    428 
    429 void LTOModule::addPotentialUndefinedSymbol(GlobalValue *decl,
    430                                             Mangler &mangler) {
    431   // ignore all llvm.* symbols
    432   if (decl->getName().startswith("llvm."))
    433     return;
    434 
    435   // ignore all aliases
    436   if (isa<GlobalAlias>(decl))
    437     return;
    438 
    439   SmallString<64> name;
    440   mangler.getNameWithPrefix(name, decl, false);
    441 
    442   StringMap<NameAndAttributes>::value_type &entry =
    443     _undefines.GetOrCreateValue(name);
    444 
    445   // we already have the symbol
    446   if (entry.getValue().name)
    447     return;
    448 
    449   NameAndAttributes info;
    450 
    451   info.name = entry.getKey().data();
    452   if (decl->hasExternalWeakLinkage())
    453     info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
    454   else
    455     info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    456 
    457   entry.setValue(info);
    458 }
    459 
    460 
    461 namespace {
    462   class RecordStreamer : public MCStreamer {
    463   public:
    464     enum State { NeverSeen, Global, Defined, DefinedGlobal, Used};
    465 
    466   private:
    467     StringMap<State> Symbols;
    468 
    469     void markDefined(const MCSymbol &Symbol) {
    470       State &S = Symbols[Symbol.getName()];
    471       switch (S) {
    472       case DefinedGlobal:
    473       case Global:
    474         S = DefinedGlobal;
    475         break;
    476       case NeverSeen:
    477       case Defined:
    478       case Used:
    479         S = Defined;
    480         break;
    481       }
    482     }
    483     void markGlobal(const MCSymbol &Symbol) {
    484       State &S = Symbols[Symbol.getName()];
    485       switch (S) {
    486       case DefinedGlobal:
    487       case Defined:
    488         S = DefinedGlobal;
    489         break;
    490 
    491       case NeverSeen:
    492       case Global:
    493       case Used:
    494         S = Global;
    495         break;
    496       }
    497     }
    498     void markUsed(const MCSymbol &Symbol) {
    499       State &S = Symbols[Symbol.getName()];
    500       switch (S) {
    501       case DefinedGlobal:
    502       case Defined:
    503       case Global:
    504         break;
    505 
    506       case NeverSeen:
    507       case Used:
    508         S = Used;
    509         break;
    510       }
    511     }
    512 
    513     // FIXME: mostly copied for the obj streamer.
    514     void AddValueSymbols(const MCExpr *Value) {
    515       switch (Value->getKind()) {
    516       case MCExpr::Target:
    517         // FIXME: What should we do in here?
    518         break;
    519 
    520       case MCExpr::Constant:
    521         break;
    522 
    523       case MCExpr::Binary: {
    524         const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
    525         AddValueSymbols(BE->getLHS());
    526         AddValueSymbols(BE->getRHS());
    527         break;
    528       }
    529 
    530       case MCExpr::SymbolRef:
    531         markUsed(cast<MCSymbolRefExpr>(Value)->getSymbol());
    532         break;
    533 
    534       case MCExpr::Unary:
    535         AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
    536         break;
    537       }
    538     }
    539 
    540   public:
    541     typedef StringMap<State>::const_iterator const_iterator;
    542 
    543     const_iterator begin() {
    544       return Symbols.begin();
    545     }
    546 
    547     const_iterator end() {
    548       return Symbols.end();
    549     }
    550 
    551     RecordStreamer(MCContext &Context) : MCStreamer(Context) {}
    552 
    553     virtual void ChangeSection(const MCSection *Section) {}
    554     virtual void InitSections() {}
    555     virtual void EmitLabel(MCSymbol *Symbol) {
    556       Symbol->setSection(*getCurrentSection());
    557       markDefined(*Symbol);
    558     }
    559     virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
    560     virtual void EmitThumbFunc(MCSymbol *Func) {}
    561     virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
    562       // FIXME: should we handle aliases?
    563       markDefined(*Symbol);
    564     }
    565     virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) {
    566       if (Attribute == MCSA_Global)
    567         markGlobal(*Symbol);
    568     }
    569     virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
    570     virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {}
    571     virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
    572     virtual void EmitCOFFSymbolStorageClass(int StorageClass) {}
    573     virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    574                               unsigned Size , unsigned ByteAlignment) {
    575       markDefined(*Symbol);
    576     }
    577     virtual void EmitCOFFSymbolType(int Type) {}
    578     virtual void EndCOFFSymbolDef() {}
    579     virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    580                                   unsigned ByteAlignment) {
    581       markDefined(*Symbol);
    582     }
    583     virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
    584     virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    585                                        unsigned ByteAlignment) {}
    586     virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    587                                 uint64_t Size, unsigned ByteAlignment) {}
    588     virtual void EmitBytes(StringRef Data, unsigned AddrSpace) {}
    589     virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
    590                                unsigned AddrSpace) {}
    591     virtual void EmitULEB128Value(const MCExpr *Value) {}
    592     virtual void EmitSLEB128Value(const MCExpr *Value) {}
    593     virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
    594                                       unsigned ValueSize,
    595                                       unsigned MaxBytesToEmit) {}
    596     virtual void EmitCodeAlignment(unsigned ByteAlignment,
    597                                    unsigned MaxBytesToEmit) {}
    598     virtual void EmitValueToOffset(const MCExpr *Offset,
    599                                    unsigned char Value ) {}
    600     virtual void EmitFileDirective(StringRef Filename) {}
    601     virtual void EmitDwarfAdvanceLineAddr(int64_t LineDelta,
    602                                           const MCSymbol *LastLabel,
    603                                           const MCSymbol *Label,
    604                                           unsigned PointerSize) {}
    605 
    606     virtual void EmitInstruction(const MCInst &Inst) {
    607       // Scan for values.
    608       for (unsigned i = Inst.getNumOperands(); i--; )
    609         if (Inst.getOperand(i).isExpr())
    610           AddValueSymbols(Inst.getOperand(i).getExpr());
    611     }
    612     virtual void Finish() {}
    613   };
    614 }
    615 
    616 bool LTOModule::addAsmGlobalSymbols(MCContext &Context, std::string &errMsg) {
    617   const std::string &inlineAsm = _module->getModuleInlineAsm();
    618   if (inlineAsm.empty())
    619     return false;
    620 
    621   OwningPtr<RecordStreamer> Streamer(new RecordStreamer(Context));
    622   MemoryBuffer *Buffer = MemoryBuffer::getMemBuffer(inlineAsm);
    623   SourceMgr SrcMgr;
    624   SrcMgr.AddNewSourceBuffer(Buffer, SMLoc());
    625   OwningPtr<MCAsmParser> Parser(createMCAsmParser(SrcMgr,
    626                                                   Context, *Streamer,
    627                                                   *_target->getMCAsmInfo()));
    628   OwningPtr<MCSubtargetInfo> STI(_target->getTarget().
    629                       createMCSubtargetInfo(_target->getTargetTriple(),
    630                                             _target->getTargetCPU(),
    631                                             _target->getTargetFeatureString()));
    632   OwningPtr<MCTargetAsmParser>
    633     TAP(_target->getTarget().createMCAsmParser(*STI, *Parser.get()));
    634   if (!TAP) {
    635     errMsg = "target " + std::string(_target->getTarget().getName()) +
    636         " does not define AsmParser.";
    637     return true;
    638   }
    639 
    640   Parser->setTargetParser(*TAP);
    641   int Res = Parser->Run(false);
    642   if (Res)
    643     return true;
    644 
    645   for (RecordStreamer::const_iterator i = Streamer->begin(),
    646          e = Streamer->end(); i != e; ++i) {
    647     StringRef Key = i->first();
    648     RecordStreamer::State Value = i->second;
    649     if (Value == RecordStreamer::DefinedGlobal)
    650       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_DEFAULT);
    651     else if (Value == RecordStreamer::Defined)
    652       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_INTERNAL);
    653     else if (Value == RecordStreamer::Global ||
    654              Value == RecordStreamer::Used)
    655       addAsmGlobalSymbolUndef(Key.data());
    656   }
    657   return false;
    658 }
    659 
    660 static bool isDeclaration(const GlobalValue &V) {
    661   if (V.hasAvailableExternallyLinkage())
    662     return true;
    663   if (V.isMaterializable())
    664     return false;
    665   return V.isDeclaration();
    666 }
    667 
    668 static bool isAliasToDeclaration(const GlobalAlias &V) {
    669   return isDeclaration(*V.getAliasedGlobal());
    670 }
    671 
    672 bool LTOModule::ParseSymbols(std::string &errMsg) {
    673   // Use mangler to add GlobalPrefix to names to match linker names.
    674   MCContext Context(*_target->getMCAsmInfo(), *_target->getRegisterInfo(),NULL);
    675   Mangler mangler(Context, *_target->getTargetData());
    676 
    677   // add functions
    678   for (Module::iterator f = _module->begin(); f != _module->end(); ++f) {
    679     if (isDeclaration(*f))
    680       addPotentialUndefinedSymbol(f, mangler);
    681     else
    682       addDefinedFunctionSymbol(f, mangler);
    683   }
    684 
    685   // add data
    686   for (Module::global_iterator v = _module->global_begin(),
    687          e = _module->global_end(); v !=  e; ++v) {
    688     if (isDeclaration(*v))
    689       addPotentialUndefinedSymbol(v, mangler);
    690     else
    691       addDefinedDataSymbol(v, mangler);
    692   }
    693 
    694   // add asm globals
    695   if (addAsmGlobalSymbols(Context, errMsg))
    696     return true;
    697 
    698   // add aliases
    699   for (Module::alias_iterator i = _module->alias_begin(),
    700          e = _module->alias_end(); i != e; ++i) {
    701     if (isAliasToDeclaration(*i))
    702       addPotentialUndefinedSymbol(i, mangler);
    703     else
    704       addDefinedDataSymbol(i, mangler);
    705   }
    706 
    707   // make symbols for all undefines
    708   for (StringMap<NameAndAttributes>::iterator it=_undefines.begin();
    709        it != _undefines.end(); ++it) {
    710     // if this symbol also has a definition, then don't make an undefine
    711     // because it is a tentative definition
    712     if (_defines.count(it->getKey()) == 0) {
    713       NameAndAttributes info = it->getValue();
    714       _symbols.push_back(info);
    715     }
    716   }
    717   return false;
    718 }
    719 
    720 
    721 uint32_t LTOModule::getSymbolCount() {
    722   return _symbols.size();
    723 }
    724 
    725 
    726 lto_symbol_attributes LTOModule::getSymbolAttributes(uint32_t index) {
    727   if (index < _symbols.size())
    728     return _symbols[index].attributes;
    729   else
    730     return lto_symbol_attributes(0);
    731 }
    732 
    733 const char *LTOModule::getSymbolName(uint32_t index) {
    734   if (index < _symbols.size())
    735     return _symbols[index].name;
    736   else
    737     return NULL;
    738 }
    739