Home | History | Annotate | Download | only in lto 
      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 #include "llvm/ADT/OwningPtr.h"
     17 #include "llvm/ADT/Triple.h"
     18 #include "llvm/Bitcode/ReaderWriter.h"
     19 #include "llvm/IR/Constants.h"
     20 #include "llvm/IR/LLVMContext.h"
     21 #include "llvm/IR/Module.h"
     22 #include "llvm/MC/MCExpr.h"
     23 #include "llvm/MC/MCInst.h"
     24 #include "llvm/MC/MCParser/MCAsmParser.h"
     25 #include "llvm/MC/MCStreamer.h"
     26 #include "llvm/MC/MCSubtargetInfo.h"
     27 #include "llvm/MC/MCSymbol.h"
     28 #include "llvm/MC/MCTargetAsmParser.h"
     29 #include "llvm/MC/SubtargetFeature.h"
     30 #include "llvm/Support/CommandLine.h"
     31 #include "llvm/Support/Host.h"
     32 #include "llvm/Support/FileSystem.h"
     33 #include "llvm/Support/MemoryBuffer.h"
     34 #include "llvm/Support/Path.h"
     35 #include "llvm/Support/SourceMgr.h"
     36 #include "llvm/Support/TargetRegistry.h"
     37 #include "llvm/Support/TargetSelect.h"
     38 #include "llvm/Support/system_error.h"
     39 #include "llvm/Target/TargetRegisterInfo.h"
     40 using namespace llvm;
     41 
     42 static cl::opt<bool>
     43 EnableFPMAD("enable-fp-mad",
     44   cl::desc("Enable less precise MAD instructions to be generated"),
     45   cl::init(false));
     46 
     47 static cl::opt<bool>
     48 DisableFPElim("disable-fp-elim",
     49   cl::desc("Disable frame pointer elimination optimization"),
     50   cl::init(false));
     51 
     52 static cl::opt<bool>
     53 EnableUnsafeFPMath("enable-unsafe-fp-math",
     54   cl::desc("Enable optimizations that may decrease FP precision"),
     55   cl::init(false));
     56 
     57 static cl::opt<bool>
     58 EnableNoInfsFPMath("enable-no-infs-fp-math",
     59   cl::desc("Enable FP math optimizations that assume no +-Infs"),
     60   cl::init(false));
     61 
     62 static cl::opt<bool>
     63 EnableNoNaNsFPMath("enable-no-nans-fp-math",
     64   cl::desc("Enable FP math optimizations that assume no NaNs"),
     65   cl::init(false));
     66 
     67 static cl::opt<bool>
     68 EnableHonorSignDependentRoundingFPMath("enable-sign-dependent-rounding-fp-math",
     69   cl::Hidden,
     70   cl::desc("Force codegen to assume rounding mode can change dynamically"),
     71   cl::init(false));
     72 
     73 static cl::opt<bool>
     74 GenerateSoftFloatCalls("soft-float",
     75   cl::desc("Generate software floating point library calls"),
     76   cl::init(false));
     77 
     78 static cl::opt<llvm::FloatABI::ABIType>
     79 FloatABIForCalls("float-abi",
     80   cl::desc("Choose float ABI type"),
     81   cl::init(FloatABI::Default),
     82   cl::values(
     83     clEnumValN(FloatABI::Default, "default",
     84                "Target default float ABI type"),
     85     clEnumValN(FloatABI::Soft, "soft",
     86                "Soft float ABI (implied by -soft-float)"),
     87     clEnumValN(FloatABI::Hard, "hard",
     88                "Hard float ABI (uses FP registers)"),
     89     clEnumValEnd));
     90 
     91 static cl::opt<llvm::FPOpFusion::FPOpFusionMode>
     92 FuseFPOps("fp-contract",
     93   cl::desc("Enable aggresive formation of fused FP ops"),
     94   cl::init(FPOpFusion::Standard),
     95   cl::values(
     96     clEnumValN(FPOpFusion::Fast, "fast",
     97                "Fuse FP ops whenever profitable"),
     98     clEnumValN(FPOpFusion::Standard, "on",
     99                "Only fuse 'blessed' FP ops."),
    100     clEnumValN(FPOpFusion::Strict, "off",
    101                "Only fuse FP ops when the result won't be effected."),
    102     clEnumValEnd));
    103 
    104 static cl::opt<bool>
    105 DontPlaceZerosInBSS("nozero-initialized-in-bss",
    106   cl::desc("Don't place zero-initialized symbols into bss section"),
    107   cl::init(false));
    108 
    109 static cl::opt<bool>
    110 EnableGuaranteedTailCallOpt("tailcallopt",
    111   cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
    112   cl::init(false));
    113 
    114 static cl::opt<bool>
    115 DisableTailCalls("disable-tail-calls",
    116   cl::desc("Never emit tail calls"),
    117   cl::init(false));
    118 
    119 static cl::opt<unsigned>
    120 OverrideStackAlignment("stack-alignment",
    121   cl::desc("Override default stack alignment"),
    122   cl::init(0));
    123 
    124 static cl::opt<std::string>
    125 TrapFuncName("trap-func", cl::Hidden,
    126   cl::desc("Emit a call to trap function rather than a trap instruction"),
    127   cl::init(""));
    128 
    129 static cl::opt<bool>
    130 EnablePIE("enable-pie",
    131   cl::desc("Assume the creation of a position independent executable."),
    132   cl::init(false));
    133 
    134 static cl::opt<bool>
    135 SegmentedStacks("segmented-stacks",
    136   cl::desc("Use segmented stacks if possible."),
    137   cl::init(false));
    138 
    139 static cl::opt<bool>
    140 UseInitArray("use-init-array",
    141   cl::desc("Use .init_array instead of .ctors."),
    142   cl::init(false));
    143 
    144 LTOModule::LTOModule(llvm::Module *m, llvm::TargetMachine *t)
    145   : _module(m), _target(t),
    146     _context(_target->getMCAsmInfo(), _target->getRegisterInfo(), NULL),
    147     _mangler(_context, t) {}
    148 
    149 /// isBitcodeFile - Returns 'true' if the file (or memory contents) is LLVM
    150 /// bitcode.
    151 bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
    152   return sys::fs::identify_magic(StringRef((const char *)mem, length)) ==
    153          sys::fs::file_magic::bitcode;
    154 }
    155 
    156 bool LTOModule::isBitcodeFile(const char *path) {
    157   sys::fs::file_magic type;
    158   if (sys::fs::identify_magic(path, type))
    159     return false;
    160   return type == sys::fs::file_magic::bitcode;
    161 }
    162 
    163 /// isBitcodeFileForTarget - Returns 'true' if the file (or memory contents) is
    164 /// LLVM bitcode for the specified triple.
    165 bool LTOModule::isBitcodeFileForTarget(const void *mem, size_t length,
    166                                        const char *triplePrefix) {
    167   MemoryBuffer *buffer = makeBuffer(mem, length);
    168   if (!buffer)
    169     return false;
    170   return isTargetMatch(buffer, triplePrefix);
    171 }
    172 
    173 bool LTOModule::isBitcodeFileForTarget(const char *path,
    174                                        const char *triplePrefix) {
    175   OwningPtr<MemoryBuffer> buffer;
    176   if (MemoryBuffer::getFile(path, buffer))
    177     return false;
    178   return isTargetMatch(buffer.take(), triplePrefix);
    179 }
    180 
    181 /// isTargetMatch - Returns 'true' if the memory buffer is for the specified
    182 /// target triple.
    183 bool LTOModule::isTargetMatch(MemoryBuffer *buffer, const char *triplePrefix) {
    184   std::string Triple = getBitcodeTargetTriple(buffer, getGlobalContext());
    185   delete buffer;
    186   return strncmp(Triple.c_str(), triplePrefix, strlen(triplePrefix)) == 0;
    187 }
    188 
    189 /// makeLTOModule - Create an LTOModule. N.B. These methods take ownership of
    190 /// the buffer.
    191 LTOModule *LTOModule::makeLTOModule(const char *path, std::string &errMsg) {
    192   OwningPtr<MemoryBuffer> buffer;
    193   if (error_code ec = MemoryBuffer::getFile(path, buffer)) {
    194     errMsg = ec.message();
    195     return NULL;
    196   }
    197   return makeLTOModule(buffer.take(), errMsg);
    198 }
    199 
    200 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    201                                     size_t size, std::string &errMsg) {
    202   return makeLTOModule(fd, path, size, 0, errMsg);
    203 }
    204 
    205 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    206                                     size_t map_size,
    207                                     off_t offset,
    208                                     std::string &errMsg) {
    209   OwningPtr<MemoryBuffer> buffer;
    210   if (error_code ec =
    211           MemoryBuffer::getOpenFileSlice(fd, path, buffer, map_size, offset)) {
    212     errMsg = ec.message();
    213     return NULL;
    214   }
    215   return makeLTOModule(buffer.take(), errMsg);
    216 }
    217 
    218 LTOModule *LTOModule::makeLTOModule(const void *mem, size_t length,
    219                                     std::string &errMsg) {
    220   OwningPtr<MemoryBuffer> buffer(makeBuffer(mem, length));
    221   if (!buffer)
    222     return NULL;
    223   return makeLTOModule(buffer.take(), errMsg);
    224 }
    225 
    226 void LTOModule::getTargetOptions(TargetOptions &Options) {
    227   Options.LessPreciseFPMADOption = EnableFPMAD;
    228   Options.NoFramePointerElim = DisableFPElim;
    229   Options.AllowFPOpFusion = FuseFPOps;
    230   Options.UnsafeFPMath = EnableUnsafeFPMath;
    231   Options.NoInfsFPMath = EnableNoInfsFPMath;
    232   Options.NoNaNsFPMath = EnableNoNaNsFPMath;
    233   Options.HonorSignDependentRoundingFPMathOption =
    234     EnableHonorSignDependentRoundingFPMath;
    235   Options.UseSoftFloat = GenerateSoftFloatCalls;
    236   if (FloatABIForCalls != FloatABI::Default)
    237     Options.FloatABIType = FloatABIForCalls;
    238   Options.NoZerosInBSS = DontPlaceZerosInBSS;
    239   Options.GuaranteedTailCallOpt = EnableGuaranteedTailCallOpt;
    240   Options.DisableTailCalls = DisableTailCalls;
    241   Options.StackAlignmentOverride = OverrideStackAlignment;
    242   Options.TrapFuncName = TrapFuncName;
    243   Options.PositionIndependentExecutable = EnablePIE;
    244   Options.EnableSegmentedStacks = SegmentedStacks;
    245   Options.UseInitArray = UseInitArray;
    246 }
    247 
    248 LTOModule *LTOModule::makeLTOModule(MemoryBuffer *buffer,
    249                                     std::string &errMsg) {
    250   static bool Initialized = false;
    251   if (!Initialized) {
    252     InitializeAllTargets();
    253     InitializeAllTargetMCs();
    254     InitializeAllAsmParsers();
    255     Initialized = true;
    256   }
    257 
    258   // parse bitcode buffer
    259   OwningPtr<Module> m(getLazyBitcodeModule(buffer, getGlobalContext(),
    260                                            &errMsg));
    261   if (!m) {
    262     delete buffer;
    263     return NULL;
    264   }
    265 
    266   std::string TripleStr = m->getTargetTriple();
    267   if (TripleStr.empty())
    268     TripleStr = sys::getDefaultTargetTriple();
    269   llvm::Triple Triple(TripleStr);
    270 
    271   // find machine architecture for this module
    272   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
    273   if (!march)
    274     return NULL;
    275 
    276   // construct LTOModule, hand over ownership of module and target
    277   SubtargetFeatures Features;
    278   Features.getDefaultSubtargetFeatures(Triple);
    279   std::string FeatureStr = Features.getString();
    280   // Set a default CPU for Darwin triples.
    281   std::string CPU;
    282   if (Triple.isOSDarwin()) {
    283     if (Triple.getArch() == llvm::Triple::x86_64)
    284       CPU = "core2";
    285     else if (Triple.getArch() == llvm::Triple::x86)
    286       CPU = "yonah";
    287   }
    288   TargetOptions Options;
    289   getTargetOptions(Options);
    290   TargetMachine *target = march->createTargetMachine(TripleStr, CPU, FeatureStr,
    291                                                      Options);
    292   LTOModule *Ret = new LTOModule(m.take(), target);
    293   if (Ret->parseSymbols(errMsg)) {
    294     delete Ret;
    295     return NULL;
    296   }
    297 
    298   return Ret;
    299 }
    300 
    301 /// makeBuffer - Create a MemoryBuffer from a memory range.
    302 MemoryBuffer *LTOModule::makeBuffer(const void *mem, size_t length) {
    303   const char *startPtr = (const char*)mem;
    304   return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), "", false);
    305 }
    306 
    307 /// objcClassNameFromExpression - Get string that the data pointer points to.
    308 bool
    309 LTOModule::objcClassNameFromExpression(const Constant *c, std::string &name) {
    310   if (const ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
    311     Constant *op = ce->getOperand(0);
    312     if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
    313       Constant *cn = gvn->getInitializer();
    314       if (ConstantDataArray *ca = dyn_cast<ConstantDataArray>(cn)) {
    315         if (ca->isCString()) {
    316           name = ".objc_class_name_" + ca->getAsCString().str();
    317           return true;
    318         }
    319       }
    320     }
    321   }
    322   return false;
    323 }
    324 
    325 /// addObjCClass - Parse i386/ppc ObjC class data structure.
    326 void LTOModule::addObjCClass(const GlobalVariable *clgv) {
    327   const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
    328   if (!c) return;
    329 
    330   // second slot in __OBJC,__class is pointer to superclass name
    331   std::string superclassName;
    332   if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
    333     NameAndAttributes info;
    334     StringMap<NameAndAttributes>::value_type &entry =
    335       _undefines.GetOrCreateValue(superclassName);
    336     if (!entry.getValue().name) {
    337       const char *symbolName = entry.getKey().data();
    338       info.name = symbolName;
    339       info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    340       info.isFunction = false;
    341       info.symbol = clgv;
    342       entry.setValue(info);
    343     }
    344   }
    345 
    346   // third slot in __OBJC,__class is pointer to class name
    347   std::string className;
    348   if (objcClassNameFromExpression(c->getOperand(2), className)) {
    349     StringSet::value_type &entry = _defines.GetOrCreateValue(className);
    350     entry.setValue(1);
    351 
    352     NameAndAttributes info;
    353     info.name = entry.getKey().data();
    354     info.attributes = LTO_SYMBOL_PERMISSIONS_DATA |
    355       LTO_SYMBOL_DEFINITION_REGULAR | LTO_SYMBOL_SCOPE_DEFAULT;
    356     info.isFunction = false;
    357     info.symbol = clgv;
    358     _symbols.push_back(info);
    359   }
    360 }
    361 
    362 /// addObjCCategory - Parse i386/ppc ObjC category data structure.
    363 void LTOModule::addObjCCategory(const GlobalVariable *clgv) {
    364   const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
    365   if (!c) return;
    366 
    367   // second slot in __OBJC,__category is pointer to target class name
    368   std::string targetclassName;
    369   if (!objcClassNameFromExpression(c->getOperand(1), targetclassName))
    370     return;
    371 
    372   NameAndAttributes info;
    373   StringMap<NameAndAttributes>::value_type &entry =
    374     _undefines.GetOrCreateValue(targetclassName);
    375 
    376   if (entry.getValue().name)
    377     return;
    378 
    379   const char *symbolName = entry.getKey().data();
    380   info.name = symbolName;
    381   info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    382   info.isFunction = false;
    383   info.symbol = clgv;
    384   entry.setValue(info);
    385 }
    386 
    387 /// addObjCClassRef - Parse i386/ppc ObjC class list data structure.
    388 void LTOModule::addObjCClassRef(const GlobalVariable *clgv) {
    389   std::string targetclassName;
    390   if (!objcClassNameFromExpression(clgv->getInitializer(), targetclassName))
    391     return;
    392 
    393   NameAndAttributes info;
    394   StringMap<NameAndAttributes>::value_type &entry =
    395     _undefines.GetOrCreateValue(targetclassName);
    396   if (entry.getValue().name)
    397     return;
    398 
    399   const char *symbolName = entry.getKey().data();
    400   info.name = symbolName;
    401   info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    402   info.isFunction = false;
    403   info.symbol = clgv;
    404   entry.setValue(info);
    405 }
    406 
    407 /// addDefinedDataSymbol - Add a data symbol as defined to the list.
    408 void LTOModule::addDefinedDataSymbol(const GlobalValue *v) {
    409   // Add to list of defined symbols.
    410   addDefinedSymbol(v, false);
    411 
    412   if (!v->hasSection() /* || !isTargetDarwin */)
    413     return;
    414 
    415   // Special case i386/ppc ObjC data structures in magic sections:
    416   // The issue is that the old ObjC object format did some strange
    417   // contortions to avoid real linker symbols.  For instance, the
    418   // ObjC class data structure is allocated statically in the executable
    419   // that defines that class.  That data structures contains a pointer to
    420   // its superclass.  But instead of just initializing that part of the
    421   // struct to the address of its superclass, and letting the static and
    422   // dynamic linkers do the rest, the runtime works by having that field
    423   // instead point to a C-string that is the name of the superclass.
    424   // At runtime the objc initialization updates that pointer and sets
    425   // it to point to the actual super class.  As far as the linker
    426   // knows it is just a pointer to a string.  But then someone wanted the
    427   // linker to issue errors at build time if the superclass was not found.
    428   // So they figured out a way in mach-o object format to use an absolute
    429   // symbols (.objc_class_name_Foo = 0) and a floating reference
    430   // (.reference .objc_class_name_Bar) to cause the linker into erroring when
    431   // a class was missing.
    432   // The following synthesizes the implicit .objc_* symbols for the linker
    433   // from the ObjC data structures generated by the front end.
    434 
    435   // special case if this data blob is an ObjC class definition
    436   if (v->getSection().compare(0, 15, "__OBJC,__class,") == 0) {
    437     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    438       addObjCClass(gv);
    439     }
    440   }
    441 
    442   // special case if this data blob is an ObjC category definition
    443   else if (v->getSection().compare(0, 18, "__OBJC,__category,") == 0) {
    444     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    445       addObjCCategory(gv);
    446     }
    447   }
    448 
    449   // special case if this data blob is the list of referenced classes
    450   else if (v->getSection().compare(0, 18, "__OBJC,__cls_refs,") == 0) {
    451     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    452       addObjCClassRef(gv);
    453     }
    454   }
    455 }
    456 
    457 /// addDefinedFunctionSymbol - Add a function symbol as defined to the list.
    458 void LTOModule::addDefinedFunctionSymbol(const Function *f) {
    459   // add to list of defined symbols
    460   addDefinedSymbol(f, true);
    461 }
    462 
    463 /// addDefinedSymbol - Add a defined symbol to the list.
    464 void LTOModule::addDefinedSymbol(const GlobalValue *def, bool isFunction) {
    465   // ignore all llvm.* symbols
    466   if (def->getName().startswith("llvm."))
    467     return;
    468 
    469   // string is owned by _defines
    470   SmallString<64> Buffer;
    471   _mangler.getNameWithPrefix(Buffer, def, false);
    472 
    473   // set alignment part log2() can have rounding errors
    474   uint32_t align = def->getAlignment();
    475   uint32_t attr = align ? countTrailingZeros(def->getAlignment()) : 0;
    476 
    477   // set permissions part
    478   if (isFunction) {
    479     attr |= LTO_SYMBOL_PERMISSIONS_CODE;
    480   } else {
    481     const GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
    482     if (gv && gv->isConstant())
    483       attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
    484     else
    485       attr |= LTO_SYMBOL_PERMISSIONS_DATA;
    486   }
    487 
    488   // set definition part
    489   if (def->hasWeakLinkage() || def->hasLinkOnceLinkage() ||
    490       def->hasLinkerPrivateWeakLinkage())
    491     attr |= LTO_SYMBOL_DEFINITION_WEAK;
    492   else if (def->hasCommonLinkage())
    493     attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
    494   else
    495     attr |= LTO_SYMBOL_DEFINITION_REGULAR;
    496 
    497   // set scope part
    498   if (def->hasHiddenVisibility())
    499     attr |= LTO_SYMBOL_SCOPE_HIDDEN;
    500   else if (def->hasProtectedVisibility())
    501     attr |= LTO_SYMBOL_SCOPE_PROTECTED;
    502   else if (def->hasExternalLinkage() || def->hasWeakLinkage() ||
    503            def->hasLinkOnceLinkage() || def->hasCommonLinkage() ||
    504            def->hasLinkerPrivateWeakLinkage())
    505     attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    506   else if (def->hasLinkOnceODRAutoHideLinkage())
    507     attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
    508   else
    509     attr |= LTO_SYMBOL_SCOPE_INTERNAL;
    510 
    511   StringSet::value_type &entry = _defines.GetOrCreateValue(Buffer);
    512   entry.setValue(1);
    513 
    514   // fill information structure
    515   NameAndAttributes info;
    516   StringRef Name = entry.getKey();
    517   info.name = Name.data();
    518   assert(info.name[Name.size()] == '\0');
    519   info.attributes = attr;
    520   info.isFunction = isFunction;
    521   info.symbol = def;
    522 
    523   // add to table of symbols
    524   _symbols.push_back(info);
    525 }
    526 
    527 /// addAsmGlobalSymbol - Add a global symbol from module-level ASM to the
    528 /// defined list.
    529 void LTOModule::addAsmGlobalSymbol(const char *name,
    530                                    lto_symbol_attributes scope) {
    531   StringSet::value_type &entry = _defines.GetOrCreateValue(name);
    532 
    533   // only add new define if not already defined
    534   if (entry.getValue())
    535     return;
    536 
    537   entry.setValue(1);
    538 
    539   NameAndAttributes &info = _undefines[entry.getKey().data()];
    540 
    541   if (info.symbol == 0) {
    542     // FIXME: This is trying to take care of module ASM like this:
    543     //
    544     //   module asm ".zerofill __FOO, __foo, _bar_baz_qux, 0"
    545     //
    546     // but is gross and its mother dresses it funny. Have the ASM parser give us
    547     // more details for this type of situation so that we're not guessing so
    548     // much.
    549 
    550     // fill information structure
    551     info.name = entry.getKey().data();
    552     info.attributes =
    553       LTO_SYMBOL_PERMISSIONS_DATA | LTO_SYMBOL_DEFINITION_REGULAR | scope;
    554     info.isFunction = false;
    555     info.symbol = 0;
    556 
    557     // add to table of symbols
    558     _symbols.push_back(info);
    559     return;
    560   }
    561 
    562   if (info.isFunction)
    563     addDefinedFunctionSymbol(cast<Function>(info.symbol));
    564   else
    565     addDefinedDataSymbol(info.symbol);
    566 
    567   _symbols.back().attributes &= ~LTO_SYMBOL_SCOPE_MASK;
    568   _symbols.back().attributes |= scope;
    569 }
    570 
    571 /// addAsmGlobalSymbolUndef - Add a global symbol from module-level ASM to the
    572 /// undefined list.
    573 void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
    574   StringMap<NameAndAttributes>::value_type &entry =
    575     _undefines.GetOrCreateValue(name);
    576 
    577   _asm_undefines.push_back(entry.getKey().data());
    578 
    579   // we already have the symbol
    580   if (entry.getValue().name)
    581     return;
    582 
    583   uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;;
    584   attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    585   NameAndAttributes info;
    586   info.name = entry.getKey().data();
    587   info.attributes = attr;
    588   info.isFunction = false;
    589   info.symbol = 0;
    590 
    591   entry.setValue(info);
    592 }
    593 
    594 /// addPotentialUndefinedSymbol - Add a symbol which isn't defined just yet to a
    595 /// list to be resolved later.
    596 void
    597 LTOModule::addPotentialUndefinedSymbol(const GlobalValue *decl, bool isFunc) {
    598   // ignore all llvm.* symbols
    599   if (decl->getName().startswith("llvm."))
    600     return;
    601 
    602   // ignore all aliases
    603   if (isa<GlobalAlias>(decl))
    604     return;
    605 
    606   SmallString<64> name;
    607   _mangler.getNameWithPrefix(name, decl, false);
    608 
    609   StringMap<NameAndAttributes>::value_type &entry =
    610     _undefines.GetOrCreateValue(name);
    611 
    612   // we already have the symbol
    613   if (entry.getValue().name)
    614     return;
    615 
    616   NameAndAttributes info;
    617 
    618   info.name = entry.getKey().data();
    619 
    620   if (decl->hasExternalWeakLinkage())
    621     info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
    622   else
    623     info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    624 
    625   info.isFunction = isFunc;
    626   info.symbol = decl;
    627 
    628   entry.setValue(info);
    629 }
    630 
    631 namespace {
    632   class RecordStreamer : public MCStreamer {
    633   public:
    634     enum State { NeverSeen, Global, Defined, DefinedGlobal, Used };
    635 
    636   private:
    637     StringMap<State> Symbols;
    638 
    639     void markDefined(const MCSymbol &Symbol) {
    640       State &S = Symbols[Symbol.getName()];
    641       switch (S) {
    642       case DefinedGlobal:
    643       case Global:
    644         S = DefinedGlobal;
    645         break;
    646       case NeverSeen:
    647       case Defined:
    648       case Used:
    649         S = Defined;
    650         break;
    651       }
    652     }
    653     void markGlobal(const MCSymbol &Symbol) {
    654       State &S = Symbols[Symbol.getName()];
    655       switch (S) {
    656       case DefinedGlobal:
    657       case Defined:
    658         S = DefinedGlobal;
    659         break;
    660 
    661       case NeverSeen:
    662       case Global:
    663       case Used:
    664         S = Global;
    665         break;
    666       }
    667     }
    668     void markUsed(const MCSymbol &Symbol) {
    669       State &S = Symbols[Symbol.getName()];
    670       switch (S) {
    671       case DefinedGlobal:
    672       case Defined:
    673       case Global:
    674         break;
    675 
    676       case NeverSeen:
    677       case Used:
    678         S = Used;
    679         break;
    680       }
    681     }
    682 
    683     // FIXME: mostly copied for the obj streamer.
    684     void AddValueSymbols(const MCExpr *Value) {
    685       switch (Value->getKind()) {
    686       case MCExpr::Target:
    687         // FIXME: What should we do in here?
    688         break;
    689 
    690       case MCExpr::Constant:
    691         break;
    692 
    693       case MCExpr::Binary: {
    694         const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
    695         AddValueSymbols(BE->getLHS());
    696         AddValueSymbols(BE->getRHS());
    697         break;
    698       }
    699 
    700       case MCExpr::SymbolRef:
    701         markUsed(cast<MCSymbolRefExpr>(Value)->getSymbol());
    702         break;
    703 
    704       case MCExpr::Unary:
    705         AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
    706         break;
    707       }
    708     }
    709 
    710   public:
    711     typedef StringMap<State>::const_iterator const_iterator;
    712 
    713     const_iterator begin() {
    714       return Symbols.begin();
    715     }
    716 
    717     const_iterator end() {
    718       return Symbols.end();
    719     }
    720 
    721     RecordStreamer(MCContext &Context)
    722         : MCStreamer(SK_RecordStreamer, Context) {}
    723 
    724     virtual void EmitInstruction(const MCInst &Inst) {
    725       // Scan for values.
    726       for (unsigned i = Inst.getNumOperands(); i--; )
    727         if (Inst.getOperand(i).isExpr())
    728           AddValueSymbols(Inst.getOperand(i).getExpr());
    729     }
    730     virtual void EmitLabel(MCSymbol *Symbol) {
    731       Symbol->setSection(*getCurrentSection().first);
    732       markDefined(*Symbol);
    733     }
    734     virtual void EmitDebugLabel(MCSymbol *Symbol) {
    735       EmitLabel(Symbol);
    736     }
    737     virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
    738       // FIXME: should we handle aliases?
    739       markDefined(*Symbol);
    740     }
    741     virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) {
    742       if (Attribute == MCSA_Global)
    743         markGlobal(*Symbol);
    744     }
    745     virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    746                               uint64_t Size , unsigned ByteAlignment) {
    747       markDefined(*Symbol);
    748     }
    749     virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    750                                   unsigned ByteAlignment) {
    751       markDefined(*Symbol);
    752     }
    753 
    754     virtual void EmitBundleAlignMode(unsigned AlignPow2) {}
    755     virtual void EmitBundleLock(bool AlignToEnd) {}
    756     virtual void EmitBundleUnlock() {}
    757 
    758     // Noop calls.
    759     virtual void ChangeSection(const MCSection *Section,
    760                                const MCExpr *Subsection) {}
    761     virtual void InitToTextSection() {}
    762     virtual void InitSections() {}
    763     virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
    764     virtual void EmitThumbFunc(MCSymbol *Func) {}
    765     virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
    766     virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {}
    767     virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
    768     virtual void EmitCOFFSymbolStorageClass(int StorageClass) {}
    769     virtual void EmitCOFFSymbolType(int Type) {}
    770     virtual void EndCOFFSymbolDef() {}
    771     virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
    772     virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    773                                        unsigned ByteAlignment) {}
    774     virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    775                                 uint64_t Size, unsigned ByteAlignment) {}
    776     virtual void EmitBytes(StringRef Data) {}
    777     virtual void EmitValueImpl(const MCExpr *Value, unsigned Size) {}
    778     virtual void EmitULEB128Value(const MCExpr *Value) {}
    779     virtual void EmitSLEB128Value(const MCExpr *Value) {}
    780     virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
    781                                       unsigned ValueSize,
    782                                       unsigned MaxBytesToEmit) {}
    783     virtual void EmitCodeAlignment(unsigned ByteAlignment,
    784                                    unsigned MaxBytesToEmit) {}
    785     virtual bool EmitValueToOffset(const MCExpr *Offset,
    786                                    unsigned char Value ) { return false; }
    787     virtual void EmitFileDirective(StringRef Filename) {}
    788     virtual void EmitDwarfAdvanceLineAddr(int64_t LineDelta,
    789                                           const MCSymbol *LastLabel,
    790                                           const MCSymbol *Label,
    791                                           unsigned PointerSize) {}
    792     virtual void FinishImpl() {}
    793 
    794     static bool classof(const MCStreamer *S) {
    795       return S->getKind() == SK_RecordStreamer;
    796     }
    797   };
    798 } // end anonymous namespace
    799 
    800 /// addAsmGlobalSymbols - Add global symbols from module-level ASM to the
    801 /// defined or undefined lists.
    802 bool LTOModule::addAsmGlobalSymbols(std::string &errMsg) {
    803   const std::string &inlineAsm = _module->getModuleInlineAsm();
    804   if (inlineAsm.empty())
    805     return false;
    806 
    807   OwningPtr<RecordStreamer> Streamer(new RecordStreamer(_context));
    808   MemoryBuffer *Buffer = MemoryBuffer::getMemBuffer(inlineAsm);
    809   SourceMgr SrcMgr;
    810   SrcMgr.AddNewSourceBuffer(Buffer, SMLoc());
    811   OwningPtr<MCAsmParser> Parser(createMCAsmParser(SrcMgr,
    812                                                   _context, *Streamer,
    813                                                   *_target->getMCAsmInfo()));
    814   const Target &T = _target->getTarget();
    815   OwningPtr<MCSubtargetInfo>
    816     STI(T.createMCSubtargetInfo(_target->getTargetTriple(),
    817                                 _target->getTargetCPU(),
    818                                 _target->getTargetFeatureString()));
    819   OwningPtr<MCTargetAsmParser> TAP(T.createMCAsmParser(*STI, *Parser.get()));
    820   if (!TAP) {
    821     errMsg = "target " + std::string(T.getName()) +
    822       " does not define AsmParser.";
    823     return true;
    824   }
    825 
    826   Parser->setTargetParser(*TAP);
    827   if (Parser->Run(false))
    828     return true;
    829 
    830   for (RecordStreamer::const_iterator i = Streamer->begin(),
    831          e = Streamer->end(); i != e; ++i) {
    832     StringRef Key = i->first();
    833     RecordStreamer::State Value = i->second;
    834     if (Value == RecordStreamer::DefinedGlobal)
    835       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_DEFAULT);
    836     else if (Value == RecordStreamer::Defined)
    837       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_INTERNAL);
    838     else if (Value == RecordStreamer::Global ||
    839              Value == RecordStreamer::Used)
    840       addAsmGlobalSymbolUndef(Key.data());
    841   }
    842 
    843   return false;
    844 }
    845 
    846 /// isDeclaration - Return 'true' if the global value is a declaration.
    847 static bool isDeclaration(const GlobalValue &V) {
    848   if (V.hasAvailableExternallyLinkage())
    849     return true;
    850 
    851   if (V.isMaterializable())
    852     return false;
    853 
    854   return V.isDeclaration();
    855 }
    856 
    857 /// parseSymbols - Parse the symbols from the module and model-level ASM and add
    858 /// them to either the defined or undefined lists.
    859 bool LTOModule::parseSymbols(std::string &errMsg) {
    860   // add functions
    861   for (Module::iterator f = _module->begin(), e = _module->end(); f != e; ++f) {
    862     if (isDeclaration(*f))
    863       addPotentialUndefinedSymbol(f, true);
    864     else
    865       addDefinedFunctionSymbol(f);
    866   }
    867 
    868   // add data
    869   for (Module::global_iterator v = _module->global_begin(),
    870          e = _module->global_end(); v !=  e; ++v) {
    871     if (isDeclaration(*v))
    872       addPotentialUndefinedSymbol(v, false);
    873     else
    874       addDefinedDataSymbol(v);
    875   }
    876 
    877   // add asm globals
    878   if (addAsmGlobalSymbols(errMsg))
    879     return true;
    880 
    881   // add aliases
    882   for (Module::alias_iterator a = _module->alias_begin(),
    883          e = _module->alias_end(); a != e; ++a) {
    884     if (isDeclaration(*a->getAliasedGlobal()))
    885       // Is an alias to a declaration.
    886       addPotentialUndefinedSymbol(a, false);
    887     else
    888       addDefinedDataSymbol(a);
    889   }
    890 
    891   // make symbols for all undefines
    892   for (StringMap<NameAndAttributes>::iterator u =_undefines.begin(),
    893          e = _undefines.end(); u != e; ++u) {
    894     // If this symbol also has a definition, then don't make an undefine because
    895     // it is a tentative definition.
    896     if (_defines.count(u->getKey())) continue;
    897     NameAndAttributes info = u->getValue();
    898     _symbols.push_back(info);
    899   }
    900 
    901   return false;
    902 }
    903