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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 #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/MemoryBuffer.h"
     33 #include "llvm/Support/Path.h"
     34 #include "llvm/Support/SourceMgr.h"
     35 #include "llvm/Support/TargetRegistry.h"
     36 #include "llvm/Support/TargetSelect.h"
     37 #include "llvm/Support/system_error.h"
     38 #include "llvm/Target/TargetRegisterInfo.h"
     39 using namespace llvm;
     40 
     41 static cl::opt<bool>
     42 EnableFPMAD("enable-fp-mad",
     43   cl::desc("Enable less precise MAD instructions to be generated"),
     44   cl::init(false));
     45 
     46 static cl::opt<bool>
     47 DisableFPElim("disable-fp-elim",
     48   cl::desc("Disable frame pointer elimination optimization"),
     49   cl::init(false));
     50 
     51 static cl::opt<bool>
     52 DisableFPElimNonLeaf("disable-non-leaf-fp-elim",
     53   cl::desc("Disable frame pointer elimination optimization for non-leaf funcs"),
     54   cl::init(false));
     55 
     56 static cl::opt<bool>
     57 EnableUnsafeFPMath("enable-unsafe-fp-math",
     58   cl::desc("Enable optimizations that may decrease FP precision"),
     59   cl::init(false));
     60 
     61 static cl::opt<bool>
     62 EnableNoInfsFPMath("enable-no-infs-fp-math",
     63   cl::desc("Enable FP math optimizations that assume no +-Infs"),
     64   cl::init(false));
     65 
     66 static cl::opt<bool>
     67 EnableNoNaNsFPMath("enable-no-nans-fp-math",
     68   cl::desc("Enable FP math optimizations that assume no NaNs"),
     69   cl::init(false));
     70 
     71 static cl::opt<bool>
     72 EnableHonorSignDependentRoundingFPMath("enable-sign-dependent-rounding-fp-math",
     73   cl::Hidden,
     74   cl::desc("Force codegen to assume rounding mode can change dynamically"),
     75   cl::init(false));
     76 
     77 static cl::opt<bool>
     78 GenerateSoftFloatCalls("soft-float",
     79   cl::desc("Generate software floating point library calls"),
     80   cl::init(false));
     81 
     82 static cl::opt<llvm::FloatABI::ABIType>
     83 FloatABIForCalls("float-abi",
     84   cl::desc("Choose float ABI type"),
     85   cl::init(FloatABI::Default),
     86   cl::values(
     87     clEnumValN(FloatABI::Default, "default",
     88                "Target default float ABI type"),
     89     clEnumValN(FloatABI::Soft, "soft",
     90                "Soft float ABI (implied by -soft-float)"),
     91     clEnumValN(FloatABI::Hard, "hard",
     92                "Hard float ABI (uses FP registers)"),
     93     clEnumValEnd));
     94 
     95 static cl::opt<llvm::FPOpFusion::FPOpFusionMode>
     96 FuseFPOps("fp-contract",
     97   cl::desc("Enable aggresive formation of fused FP ops"),
     98   cl::init(FPOpFusion::Standard),
     99   cl::values(
    100     clEnumValN(FPOpFusion::Fast, "fast",
    101                "Fuse FP ops whenever profitable"),
    102     clEnumValN(FPOpFusion::Standard, "on",
    103                "Only fuse 'blessed' FP ops."),
    104     clEnumValN(FPOpFusion::Strict, "off",
    105                "Only fuse FP ops when the result won't be effected."),
    106     clEnumValEnd));
    107 
    108 static cl::opt<bool>
    109 DontPlaceZerosInBSS("nozero-initialized-in-bss",
    110   cl::desc("Don't place zero-initialized symbols into bss section"),
    111   cl::init(false));
    112 
    113 static cl::opt<bool>
    114 EnableGuaranteedTailCallOpt("tailcallopt",
    115   cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
    116   cl::init(false));
    117 
    118 static cl::opt<bool>
    119 DisableTailCalls("disable-tail-calls",
    120   cl::desc("Never emit tail calls"),
    121   cl::init(false));
    122 
    123 static cl::opt<unsigned>
    124 OverrideStackAlignment("stack-alignment",
    125   cl::desc("Override default stack alignment"),
    126   cl::init(0));
    127 
    128 static cl::opt<bool>
    129 EnableRealignStack("realign-stack",
    130   cl::desc("Realign stack if needed"),
    131   cl::init(true));
    132 
    133 static cl::opt<std::string>
    134 TrapFuncName("trap-func", cl::Hidden,
    135   cl::desc("Emit a call to trap function rather than a trap instruction"),
    136   cl::init(""));
    137 
    138 static cl::opt<bool>
    139 EnablePIE("enable-pie",
    140   cl::desc("Assume the creation of a position independent executable."),
    141   cl::init(false));
    142 
    143 static cl::opt<bool>
    144 SegmentedStacks("segmented-stacks",
    145   cl::desc("Use segmented stacks if possible."),
    146   cl::init(false));
    147 
    148 static cl::opt<bool>
    149 UseInitArray("use-init-array",
    150   cl::desc("Use .init_array instead of .ctors."),
    151   cl::init(false));
    152 
    153 static cl::opt<unsigned>
    154 SSPBufferSize("stack-protector-buffer-size", cl::init(8),
    155               cl::desc("Lower bound for a buffer to be considered for "
    156                        "stack protection"));
    157 
    158 LTOModule::LTOModule(llvm::Module *m, llvm::TargetMachine *t)
    159   : _module(m), _target(t),
    160     _context(*_target->getMCAsmInfo(), *_target->getRegisterInfo(), NULL),
    161     _mangler(_context, *_target->getDataLayout()) {}
    162 
    163 /// isBitcodeFile - Returns 'true' if the file (or memory contents) is LLVM
    164 /// bitcode.
    165 bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
    166   return llvm::sys::IdentifyFileType((const char*)mem, length)
    167     == llvm::sys::Bitcode_FileType;
    168 }
    169 
    170 bool LTOModule::isBitcodeFile(const char *path) {
    171   return llvm::sys::Path(path).isBitcodeFile();
    172 }
    173 
    174 /// isBitcodeFileForTarget - Returns 'true' if the file (or memory contents) is
    175 /// LLVM bitcode for the specified triple.
    176 bool LTOModule::isBitcodeFileForTarget(const void *mem, size_t length,
    177                                        const char *triplePrefix) {
    178   MemoryBuffer *buffer = makeBuffer(mem, length);
    179   if (!buffer)
    180     return false;
    181   return isTargetMatch(buffer, triplePrefix);
    182 }
    183 
    184 bool LTOModule::isBitcodeFileForTarget(const char *path,
    185                                        const char *triplePrefix) {
    186   OwningPtr<MemoryBuffer> buffer;
    187   if (MemoryBuffer::getFile(path, buffer))
    188     return false;
    189   return isTargetMatch(buffer.take(), triplePrefix);
    190 }
    191 
    192 /// isTargetMatch - Returns 'true' if the memory buffer is for the specified
    193 /// target triple.
    194 bool LTOModule::isTargetMatch(MemoryBuffer *buffer, const char *triplePrefix) {
    195   std::string Triple = getBitcodeTargetTriple(buffer, getGlobalContext());
    196   delete buffer;
    197   return strncmp(Triple.c_str(), triplePrefix, strlen(triplePrefix)) == 0;
    198 }
    199 
    200 /// makeLTOModule - Create an LTOModule. N.B. These methods take ownership of
    201 /// the buffer.
    202 LTOModule *LTOModule::makeLTOModule(const char *path, std::string &errMsg) {
    203   OwningPtr<MemoryBuffer> buffer;
    204   if (error_code ec = MemoryBuffer::getFile(path, buffer)) {
    205     errMsg = ec.message();
    206     return NULL;
    207   }
    208   return makeLTOModule(buffer.take(), errMsg);
    209 }
    210 
    211 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    212                                     size_t size, std::string &errMsg) {
    213   return makeLTOModule(fd, path, size, size, 0, errMsg);
    214 }
    215 
    216 LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
    217                                     size_t file_size,
    218                                     size_t map_size,
    219                                     off_t offset,
    220                                     std::string &errMsg) {
    221   OwningPtr<MemoryBuffer> buffer;
    222   if (error_code ec = MemoryBuffer::getOpenFile(fd, path, buffer, file_size,
    223                                                 map_size, offset, false)) {
    224     errMsg = ec.message();
    225     return NULL;
    226   }
    227   return makeLTOModule(buffer.take(), errMsg);
    228 }
    229 
    230 LTOModule *LTOModule::makeLTOModule(const void *mem, size_t length,
    231                                     std::string &errMsg) {
    232   OwningPtr<MemoryBuffer> buffer(makeBuffer(mem, length));
    233   if (!buffer)
    234     return NULL;
    235   return makeLTOModule(buffer.take(), errMsg);
    236 }
    237 
    238 void LTOModule::getTargetOptions(TargetOptions &Options) {
    239   Options.LessPreciseFPMADOption = EnableFPMAD;
    240   Options.NoFramePointerElim = DisableFPElim;
    241   Options.NoFramePointerElimNonLeaf = DisableFPElimNonLeaf;
    242   Options.AllowFPOpFusion = FuseFPOps;
    243   Options.UnsafeFPMath = EnableUnsafeFPMath;
    244   Options.NoInfsFPMath = EnableNoInfsFPMath;
    245   Options.NoNaNsFPMath = EnableNoNaNsFPMath;
    246   Options.HonorSignDependentRoundingFPMathOption =
    247     EnableHonorSignDependentRoundingFPMath;
    248   Options.UseSoftFloat = GenerateSoftFloatCalls;
    249   if (FloatABIForCalls != FloatABI::Default)
    250     Options.FloatABIType = FloatABIForCalls;
    251   Options.NoZerosInBSS = DontPlaceZerosInBSS;
    252   Options.GuaranteedTailCallOpt = EnableGuaranteedTailCallOpt;
    253   Options.DisableTailCalls = DisableTailCalls;
    254   Options.StackAlignmentOverride = OverrideStackAlignment;
    255   Options.RealignStack = EnableRealignStack;
    256   Options.TrapFuncName = TrapFuncName;
    257   Options.PositionIndependentExecutable = EnablePIE;
    258   Options.EnableSegmentedStacks = SegmentedStacks;
    259   Options.UseInitArray = UseInitArray;
    260   Options.SSPBufferSize = SSPBufferSize;
    261 }
    262 
    263 LTOModule *LTOModule::makeLTOModule(MemoryBuffer *buffer,
    264                                     std::string &errMsg) {
    265   static bool Initialized = false;
    266   if (!Initialized) {
    267     InitializeAllTargets();
    268     InitializeAllTargetMCs();
    269     InitializeAllAsmParsers();
    270     Initialized = true;
    271   }
    272 
    273   // parse bitcode buffer
    274   OwningPtr<Module> m(getLazyBitcodeModule(buffer, getGlobalContext(),
    275                                            &errMsg));
    276   if (!m) {
    277     delete buffer;
    278     return NULL;
    279   }
    280 
    281   std::string TripleStr = m->getTargetTriple();
    282   if (TripleStr.empty())
    283     TripleStr = sys::getDefaultTargetTriple();
    284   llvm::Triple Triple(TripleStr);
    285 
    286   // find machine architecture for this module
    287   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
    288   if (!march)
    289     return NULL;
    290 
    291   // construct LTOModule, hand over ownership of module and target
    292   SubtargetFeatures Features;
    293   Features.getDefaultSubtargetFeatures(Triple);
    294   std::string FeatureStr = Features.getString();
    295   // Set a default CPU for Darwin triples.
    296   std::string CPU;
    297   if (Triple.isOSDarwin()) {
    298     if (Triple.getArch() == llvm::Triple::x86_64)
    299       CPU = "core2";
    300     else if (Triple.getArch() == llvm::Triple::x86)
    301       CPU = "yonah";
    302   }
    303   TargetOptions Options;
    304   getTargetOptions(Options);
    305   TargetMachine *target = march->createTargetMachine(TripleStr, CPU, FeatureStr,
    306                                                      Options);
    307   LTOModule *Ret = new LTOModule(m.take(), target);
    308   if (Ret->parseSymbols(errMsg)) {
    309     delete Ret;
    310     return NULL;
    311   }
    312 
    313   return Ret;
    314 }
    315 
    316 /// makeBuffer - Create a MemoryBuffer from a memory range.
    317 MemoryBuffer *LTOModule::makeBuffer(const void *mem, size_t length) {
    318   const char *startPtr = (const char*)mem;
    319   return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), "", false);
    320 }
    321 
    322 /// objcClassNameFromExpression - Get string that the data pointer points to.
    323 bool
    324 LTOModule::objcClassNameFromExpression(const Constant *c, std::string &name) {
    325   if (const ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
    326     Constant *op = ce->getOperand(0);
    327     if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
    328       Constant *cn = gvn->getInitializer();
    329       if (ConstantDataArray *ca = dyn_cast<ConstantDataArray>(cn)) {
    330         if (ca->isCString()) {
    331           name = ".objc_class_name_" + ca->getAsCString().str();
    332           return true;
    333         }
    334       }
    335     }
    336   }
    337   return false;
    338 }
    339 
    340 /// addObjCClass - Parse i386/ppc ObjC class data structure.
    341 void LTOModule::addObjCClass(const GlobalVariable *clgv) {
    342   const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
    343   if (!c) return;
    344 
    345   // second slot in __OBJC,__class is pointer to superclass name
    346   std::string superclassName;
    347   if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
    348     NameAndAttributes info;
    349     StringMap<NameAndAttributes>::value_type &entry =
    350       _undefines.GetOrCreateValue(superclassName);
    351     if (!entry.getValue().name) {
    352       const char *symbolName = entry.getKey().data();
    353       info.name = symbolName;
    354       info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    355       info.isFunction = false;
    356       info.symbol = clgv;
    357       entry.setValue(info);
    358     }
    359   }
    360 
    361   // third slot in __OBJC,__class is pointer to class name
    362   std::string className;
    363   if (objcClassNameFromExpression(c->getOperand(2), className)) {
    364     StringSet::value_type &entry = _defines.GetOrCreateValue(className);
    365     entry.setValue(1);
    366 
    367     NameAndAttributes info;
    368     info.name = entry.getKey().data();
    369     info.attributes = LTO_SYMBOL_PERMISSIONS_DATA |
    370       LTO_SYMBOL_DEFINITION_REGULAR | LTO_SYMBOL_SCOPE_DEFAULT;
    371     info.isFunction = false;
    372     info.symbol = clgv;
    373     _symbols.push_back(info);
    374   }
    375 }
    376 
    377 /// addObjCCategory - Parse i386/ppc ObjC category data structure.
    378 void LTOModule::addObjCCategory(const GlobalVariable *clgv) {
    379   const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
    380   if (!c) return;
    381 
    382   // second slot in __OBJC,__category is pointer to target class name
    383   std::string targetclassName;
    384   if (!objcClassNameFromExpression(c->getOperand(1), targetclassName))
    385     return;
    386 
    387   NameAndAttributes info;
    388   StringMap<NameAndAttributes>::value_type &entry =
    389     _undefines.GetOrCreateValue(targetclassName);
    390 
    391   if (entry.getValue().name)
    392     return;
    393 
    394   const char *symbolName = entry.getKey().data();
    395   info.name = symbolName;
    396   info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    397   info.isFunction = false;
    398   info.symbol = clgv;
    399   entry.setValue(info);
    400 }
    401 
    402 /// addObjCClassRef - Parse i386/ppc ObjC class list data structure.
    403 void LTOModule::addObjCClassRef(const GlobalVariable *clgv) {
    404   std::string targetclassName;
    405   if (!objcClassNameFromExpression(clgv->getInitializer(), targetclassName))
    406     return;
    407 
    408   NameAndAttributes info;
    409   StringMap<NameAndAttributes>::value_type &entry =
    410     _undefines.GetOrCreateValue(targetclassName);
    411   if (entry.getValue().name)
    412     return;
    413 
    414   const char *symbolName = entry.getKey().data();
    415   info.name = symbolName;
    416   info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    417   info.isFunction = false;
    418   info.symbol = clgv;
    419   entry.setValue(info);
    420 }
    421 
    422 /// addDefinedDataSymbol - Add a data symbol as defined to the list.
    423 void LTOModule::addDefinedDataSymbol(const GlobalValue *v) {
    424   // Add to list of defined symbols.
    425   addDefinedSymbol(v, false);
    426 
    427   if (!v->hasSection() /* || !isTargetDarwin */)
    428     return;
    429 
    430   // Special case i386/ppc ObjC data structures in magic sections:
    431   // The issue is that the old ObjC object format did some strange
    432   // contortions to avoid real linker symbols.  For instance, the
    433   // ObjC class data structure is allocated statically in the executable
    434   // that defines that class.  That data structures contains a pointer to
    435   // its superclass.  But instead of just initializing that part of the
    436   // struct to the address of its superclass, and letting the static and
    437   // dynamic linkers do the rest, the runtime works by having that field
    438   // instead point to a C-string that is the name of the superclass.
    439   // At runtime the objc initialization updates that pointer and sets
    440   // it to point to the actual super class.  As far as the linker
    441   // knows it is just a pointer to a string.  But then someone wanted the
    442   // linker to issue errors at build time if the superclass was not found.
    443   // So they figured out a way in mach-o object format to use an absolute
    444   // symbols (.objc_class_name_Foo = 0) and a floating reference
    445   // (.reference .objc_class_name_Bar) to cause the linker into erroring when
    446   // a class was missing.
    447   // The following synthesizes the implicit .objc_* symbols for the linker
    448   // from the ObjC data structures generated by the front end.
    449 
    450   // special case if this data blob is an ObjC class definition
    451   if (v->getSection().compare(0, 15, "__OBJC,__class,") == 0) {
    452     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    453       addObjCClass(gv);
    454     }
    455   }
    456 
    457   // special case if this data blob is an ObjC category definition
    458   else if (v->getSection().compare(0, 18, "__OBJC,__category,") == 0) {
    459     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    460       addObjCCategory(gv);
    461     }
    462   }
    463 
    464   // special case if this data blob is the list of referenced classes
    465   else if (v->getSection().compare(0, 18, "__OBJC,__cls_refs,") == 0) {
    466     if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
    467       addObjCClassRef(gv);
    468     }
    469   }
    470 }
    471 
    472 /// addDefinedFunctionSymbol - Add a function symbol as defined to the list.
    473 void LTOModule::addDefinedFunctionSymbol(const Function *f) {
    474   // add to list of defined symbols
    475   addDefinedSymbol(f, true);
    476 }
    477 
    478 /// addDefinedSymbol - Add a defined symbol to the list.
    479 void LTOModule::addDefinedSymbol(const GlobalValue *def, bool isFunction) {
    480   // ignore all llvm.* symbols
    481   if (def->getName().startswith("llvm."))
    482     return;
    483 
    484   // string is owned by _defines
    485   SmallString<64> Buffer;
    486   _mangler.getNameWithPrefix(Buffer, def, false);
    487 
    488   // set alignment part log2() can have rounding errors
    489   uint32_t align = def->getAlignment();
    490   uint32_t attr = align ? CountTrailingZeros_32(def->getAlignment()) : 0;
    491 
    492   // set permissions part
    493   if (isFunction) {
    494     attr |= LTO_SYMBOL_PERMISSIONS_CODE;
    495   } else {
    496     const GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
    497     if (gv && gv->isConstant())
    498       attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
    499     else
    500       attr |= LTO_SYMBOL_PERMISSIONS_DATA;
    501   }
    502 
    503   // set definition part
    504   if (def->hasWeakLinkage() || def->hasLinkOnceLinkage() ||
    505       def->hasLinkerPrivateWeakLinkage())
    506     attr |= LTO_SYMBOL_DEFINITION_WEAK;
    507   else if (def->hasCommonLinkage())
    508     attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
    509   else
    510     attr |= LTO_SYMBOL_DEFINITION_REGULAR;
    511 
    512   // set scope part
    513   if (def->hasHiddenVisibility())
    514     attr |= LTO_SYMBOL_SCOPE_HIDDEN;
    515   else if (def->hasProtectedVisibility())
    516     attr |= LTO_SYMBOL_SCOPE_PROTECTED;
    517   else if (def->hasExternalLinkage() || def->hasWeakLinkage() ||
    518            def->hasLinkOnceLinkage() || def->hasCommonLinkage() ||
    519            def->hasLinkerPrivateWeakLinkage())
    520     attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    521   else if (def->hasLinkOnceODRAutoHideLinkage())
    522     attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
    523   else
    524     attr |= LTO_SYMBOL_SCOPE_INTERNAL;
    525 
    526   StringSet::value_type &entry = _defines.GetOrCreateValue(Buffer);
    527   entry.setValue(1);
    528 
    529   // fill information structure
    530   NameAndAttributes info;
    531   StringRef Name = entry.getKey();
    532   info.name = Name.data();
    533   assert(info.name[Name.size()] == '\0');
    534   info.attributes = attr;
    535   info.isFunction = isFunction;
    536   info.symbol = def;
    537 
    538   // add to table of symbols
    539   _symbols.push_back(info);
    540 }
    541 
    542 /// addAsmGlobalSymbol - Add a global symbol from module-level ASM to the
    543 /// defined list.
    544 void LTOModule::addAsmGlobalSymbol(const char *name,
    545                                    lto_symbol_attributes scope) {
    546   StringSet::value_type &entry = _defines.GetOrCreateValue(name);
    547 
    548   // only add new define if not already defined
    549   if (entry.getValue())
    550     return;
    551 
    552   entry.setValue(1);
    553 
    554   NameAndAttributes &info = _undefines[entry.getKey().data()];
    555 
    556   if (info.symbol == 0) {
    557     // FIXME: This is trying to take care of module ASM like this:
    558     //
    559     //   module asm ".zerofill __FOO, __foo, _bar_baz_qux, 0"
    560     //
    561     // but is gross and its mother dresses it funny. Have the ASM parser give us
    562     // more details for this type of situation so that we're not guessing so
    563     // much.
    564 
    565     // fill information structure
    566     info.name = entry.getKey().data();
    567     info.attributes =
    568       LTO_SYMBOL_PERMISSIONS_DATA | LTO_SYMBOL_DEFINITION_REGULAR | scope;
    569     info.isFunction = false;
    570     info.symbol = 0;
    571 
    572     // add to table of symbols
    573     _symbols.push_back(info);
    574     return;
    575   }
    576 
    577   if (info.isFunction)
    578     addDefinedFunctionSymbol(cast<Function>(info.symbol));
    579   else
    580     addDefinedDataSymbol(info.symbol);
    581 
    582   _symbols.back().attributes &= ~LTO_SYMBOL_SCOPE_MASK;
    583   _symbols.back().attributes |= scope;
    584 }
    585 
    586 /// addAsmGlobalSymbolUndef - Add a global symbol from module-level ASM to the
    587 /// undefined list.
    588 void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
    589   StringMap<NameAndAttributes>::value_type &entry =
    590     _undefines.GetOrCreateValue(name);
    591 
    592   _asm_undefines.push_back(entry.getKey().data());
    593 
    594   // we already have the symbol
    595   if (entry.getValue().name)
    596     return;
    597 
    598   uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;;
    599   attr |= LTO_SYMBOL_SCOPE_DEFAULT;
    600   NameAndAttributes info;
    601   info.name = entry.getKey().data();
    602   info.attributes = attr;
    603   info.isFunction = false;
    604   info.symbol = 0;
    605 
    606   entry.setValue(info);
    607 }
    608 
    609 /// addPotentialUndefinedSymbol - Add a symbol which isn't defined just yet to a
    610 /// list to be resolved later.
    611 void
    612 LTOModule::addPotentialUndefinedSymbol(const GlobalValue *decl, bool isFunc) {
    613   // ignore all llvm.* symbols
    614   if (decl->getName().startswith("llvm."))
    615     return;
    616 
    617   // ignore all aliases
    618   if (isa<GlobalAlias>(decl))
    619     return;
    620 
    621   SmallString<64> name;
    622   _mangler.getNameWithPrefix(name, decl, false);
    623 
    624   StringMap<NameAndAttributes>::value_type &entry =
    625     _undefines.GetOrCreateValue(name);
    626 
    627   // we already have the symbol
    628   if (entry.getValue().name)
    629     return;
    630 
    631   NameAndAttributes info;
    632 
    633   info.name = entry.getKey().data();
    634 
    635   if (decl->hasExternalWeakLinkage())
    636     info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
    637   else
    638     info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
    639 
    640   info.isFunction = isFunc;
    641   info.symbol = decl;
    642 
    643   entry.setValue(info);
    644 }
    645 
    646 namespace {
    647   class RecordStreamer : public MCStreamer {
    648   public:
    649     enum State { NeverSeen, Global, Defined, DefinedGlobal, Used };
    650 
    651   private:
    652     StringMap<State> Symbols;
    653 
    654     void markDefined(const MCSymbol &Symbol) {
    655       State &S = Symbols[Symbol.getName()];
    656       switch (S) {
    657       case DefinedGlobal:
    658       case Global:
    659         S = DefinedGlobal;
    660         break;
    661       case NeverSeen:
    662       case Defined:
    663       case Used:
    664         S = Defined;
    665         break;
    666       }
    667     }
    668     void markGlobal(const MCSymbol &Symbol) {
    669       State &S = Symbols[Symbol.getName()];
    670       switch (S) {
    671       case DefinedGlobal:
    672       case Defined:
    673         S = DefinedGlobal;
    674         break;
    675 
    676       case NeverSeen:
    677       case Global:
    678       case Used:
    679         S = Global;
    680         break;
    681       }
    682     }
    683     void markUsed(const MCSymbol &Symbol) {
    684       State &S = Symbols[Symbol.getName()];
    685       switch (S) {
    686       case DefinedGlobal:
    687       case Defined:
    688       case Global:
    689         break;
    690 
    691       case NeverSeen:
    692       case Used:
    693         S = Used;
    694         break;
    695       }
    696     }
    697 
    698     // FIXME: mostly copied for the obj streamer.
    699     void AddValueSymbols(const MCExpr *Value) {
    700       switch (Value->getKind()) {
    701       case MCExpr::Target:
    702         // FIXME: What should we do in here?
    703         break;
    704 
    705       case MCExpr::Constant:
    706         break;
    707 
    708       case MCExpr::Binary: {
    709         const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
    710         AddValueSymbols(BE->getLHS());
    711         AddValueSymbols(BE->getRHS());
    712         break;
    713       }
    714 
    715       case MCExpr::SymbolRef:
    716         markUsed(cast<MCSymbolRefExpr>(Value)->getSymbol());
    717         break;
    718 
    719       case MCExpr::Unary:
    720         AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
    721         break;
    722       }
    723     }
    724 
    725   public:
    726     typedef StringMap<State>::const_iterator const_iterator;
    727 
    728     const_iterator begin() {
    729       return Symbols.begin();
    730     }
    731 
    732     const_iterator end() {
    733       return Symbols.end();
    734     }
    735 
    736     RecordStreamer(MCContext &Context)
    737         : MCStreamer(SK_RecordStreamer, Context) {}
    738 
    739     virtual void EmitInstruction(const MCInst &Inst) {
    740       // Scan for values.
    741       for (unsigned i = Inst.getNumOperands(); i--; )
    742         if (Inst.getOperand(i).isExpr())
    743           AddValueSymbols(Inst.getOperand(i).getExpr());
    744     }
    745     virtual void EmitLabel(MCSymbol *Symbol) {
    746       Symbol->setSection(*getCurrentSection());
    747       markDefined(*Symbol);
    748     }
    749     virtual void EmitDebugLabel(MCSymbol *Symbol) {
    750       EmitLabel(Symbol);
    751     }
    752     virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
    753       // FIXME: should we handle aliases?
    754       markDefined(*Symbol);
    755     }
    756     virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) {
    757       if (Attribute == MCSA_Global)
    758         markGlobal(*Symbol);
    759     }
    760     virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    761                               uint64_t Size , unsigned ByteAlignment) {
    762       markDefined(*Symbol);
    763     }
    764     virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    765                                   unsigned ByteAlignment) {
    766       markDefined(*Symbol);
    767     }
    768 
    769     virtual void EmitBundleAlignMode(unsigned AlignPow2) {}
    770     virtual void EmitBundleLock(bool AlignToEnd) {}
    771     virtual void EmitBundleUnlock() {}
    772 
    773     // Noop calls.
    774     virtual void ChangeSection(const MCSection *Section) {}
    775     virtual void InitToTextSection() {}
    776     virtual void InitSections() {}
    777     virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
    778     virtual void EmitThumbFunc(MCSymbol *Func) {}
    779     virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
    780     virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {}
    781     virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
    782     virtual void EmitCOFFSymbolStorageClass(int StorageClass) {}
    783     virtual void EmitCOFFSymbolType(int Type) {}
    784     virtual void EndCOFFSymbolDef() {}
    785     virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
    786     virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    787                                        unsigned ByteAlignment) {}
    788     virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    789                                 uint64_t Size, unsigned ByteAlignment) {}
    790     virtual void EmitBytes(StringRef Data, unsigned AddrSpace) {}
    791     virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
    792                                unsigned AddrSpace) {}
    793     virtual void EmitULEB128Value(const MCExpr *Value) {}
    794     virtual void EmitSLEB128Value(const MCExpr *Value) {}
    795     virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
    796                                       unsigned ValueSize,
    797                                       unsigned MaxBytesToEmit) {}
    798     virtual void EmitCodeAlignment(unsigned ByteAlignment,
    799                                    unsigned MaxBytesToEmit) {}
    800     virtual bool EmitValueToOffset(const MCExpr *Offset,
    801                                    unsigned char Value ) { return false; }
    802     virtual void EmitFileDirective(StringRef Filename) {}
    803     virtual void EmitDwarfAdvanceLineAddr(int64_t LineDelta,
    804                                           const MCSymbol *LastLabel,
    805                                           const MCSymbol *Label,
    806                                           unsigned PointerSize) {}
    807     virtual void FinishImpl() {}
    808 
    809     static bool classof(const MCStreamer *S) {
    810       return S->getKind() == SK_RecordStreamer;
    811     }
    812   };
    813 } // end anonymous namespace
    814 
    815 /// addAsmGlobalSymbols - Add global symbols from module-level ASM to the
    816 /// defined or undefined lists.
    817 bool LTOModule::addAsmGlobalSymbols(std::string &errMsg) {
    818   const std::string &inlineAsm = _module->getModuleInlineAsm();
    819   if (inlineAsm.empty())
    820     return false;
    821 
    822   OwningPtr<RecordStreamer> Streamer(new RecordStreamer(_context));
    823   MemoryBuffer *Buffer = MemoryBuffer::getMemBuffer(inlineAsm);
    824   SourceMgr SrcMgr;
    825   SrcMgr.AddNewSourceBuffer(Buffer, SMLoc());
    826   OwningPtr<MCAsmParser> Parser(createMCAsmParser(SrcMgr,
    827                                                   _context, *Streamer,
    828                                                   *_target->getMCAsmInfo()));
    829   const Target &T = _target->getTarget();
    830   OwningPtr<MCSubtargetInfo>
    831     STI(T.createMCSubtargetInfo(_target->getTargetTriple(),
    832                                 _target->getTargetCPU(),
    833                                 _target->getTargetFeatureString()));
    834   OwningPtr<MCTargetAsmParser> TAP(T.createMCAsmParser(*STI, *Parser.get()));
    835   if (!TAP) {
    836     errMsg = "target " + std::string(T.getName()) +
    837       " does not define AsmParser.";
    838     return true;
    839   }
    840 
    841   Parser->setTargetParser(*TAP);
    842   if (Parser->Run(false))
    843     return true;
    844 
    845   for (RecordStreamer::const_iterator i = Streamer->begin(),
    846          e = Streamer->end(); i != e; ++i) {
    847     StringRef Key = i->first();
    848     RecordStreamer::State Value = i->second;
    849     if (Value == RecordStreamer::DefinedGlobal)
    850       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_DEFAULT);
    851     else if (Value == RecordStreamer::Defined)
    852       addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_INTERNAL);
    853     else if (Value == RecordStreamer::Global ||
    854              Value == RecordStreamer::Used)
    855       addAsmGlobalSymbolUndef(Key.data());
    856   }
    857 
    858   return false;
    859 }
    860 
    861 /// isDeclaration - Return 'true' if the global value is a declaration.
    862 static bool isDeclaration(const GlobalValue &V) {
    863   if (V.hasAvailableExternallyLinkage())
    864     return true;
    865 
    866   if (V.isMaterializable())
    867     return false;
    868 
    869   return V.isDeclaration();
    870 }
    871 
    872 /// parseSymbols - Parse the symbols from the module and model-level ASM and add
    873 /// them to either the defined or undefined lists.
    874 bool LTOModule::parseSymbols(std::string &errMsg) {
    875   // add functions
    876   for (Module::iterator f = _module->begin(), e = _module->end(); f != e; ++f) {
    877     if (isDeclaration(*f))
    878       addPotentialUndefinedSymbol(f, true);
    879     else
    880       addDefinedFunctionSymbol(f);
    881   }
    882 
    883   // add data
    884   for (Module::global_iterator v = _module->global_begin(),
    885          e = _module->global_end(); v !=  e; ++v) {
    886     if (isDeclaration(*v))
    887       addPotentialUndefinedSymbol(v, false);
    888     else
    889       addDefinedDataSymbol(v);
    890   }
    891 
    892   // add asm globals
    893   if (addAsmGlobalSymbols(errMsg))
    894     return true;
    895 
    896   // add aliases
    897   for (Module::alias_iterator a = _module->alias_begin(),
    898          e = _module->alias_end(); a != e; ++a) {
    899     if (isDeclaration(*a->getAliasedGlobal()))
    900       // Is an alias to a declaration.
    901       addPotentialUndefinedSymbol(a, false);
    902     else
    903       addDefinedDataSymbol(a);
    904   }
    905 
    906   // make symbols for all undefines
    907   for (StringMap<NameAndAttributes>::iterator u =_undefines.begin(),
    908          e = _undefines.end(); u != e; ++u) {
    909     // If this symbol also has a definition, then don't make an undefine because
    910     // it is a tentative definition.
    911     if (_defines.count(u->getKey())) continue;
    912     NameAndAttributes info = u->getValue();
    913     _symbols.push_back(info);
    914   }
    915 
    916   return false;
    917 }
    918