path: root/contrib/libs/llvm12/lib/Object/IRSymtab.cpp

//===- IRSymtab.cpp - implementation of IR symbol tables ------------------===// 
// 
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 
// See https://llvm.org/LICENSE.txt for license information. 
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 
// 
//===----------------------------------------------------------------------===// 
 
#include "llvm/Object/IRSymtab.h" 
#include "llvm/ADT/ArrayRef.h" 
#include "llvm/ADT/DenseMap.h" 
#include "llvm/ADT/SmallPtrSet.h" 
#include "llvm/ADT/SmallString.h" 
#include "llvm/ADT/SmallVector.h" 
#include "llvm/ADT/StringRef.h" 
#include "llvm/ADT/Triple.h" 
#include "llvm/Config/llvm-config.h" 
#include "llvm/IR/Comdat.h" 
#include "llvm/IR/DataLayout.h" 
#include "llvm/IR/GlobalAlias.h" 
#include "llvm/IR/GlobalObject.h" 
#include "llvm/IR/Mangler.h" 
#include "llvm/IR/Metadata.h" 
#include "llvm/IR/Module.h" 
#include "llvm/Bitcode/BitcodeReader.h" 
#include "llvm/MC/StringTableBuilder.h" 
#include "llvm/Object/IRObjectFile.h" 
#include "llvm/Object/ModuleSymbolTable.h" 
#include "llvm/Object/SymbolicFile.h" 
#include "llvm/Support/Allocator.h" 
#include "llvm/Support/Casting.h" 
#include "llvm/Support/Error.h" 
#include "llvm/Support/StringSaver.h" 
#include "llvm/Support/VCSRevision.h" 
#include "llvm/Support/raw_ostream.h" 
#include <cassert> 
#include <string> 
#include <utility> 
#include <vector> 
 
using namespace llvm; 
using namespace irsymtab; 
 
static const char *LibcallRoutineNames[] = { 
#define HANDLE_LIBCALL(code, name) name, 
#include "llvm/IR/RuntimeLibcalls.def" 
#undef HANDLE_LIBCALL 
}; 
 
namespace { 
 
const char *getExpectedProducerName() { 
  static char DefaultName[] = LLVM_VERSION_STRING 
#ifdef LLVM_REVISION 
      " " LLVM_REVISION 
#endif 
      ; 
  // Allows for testing of the irsymtab writer and upgrade mechanism. This 
  // environment variable should not be set by users. 
  if (char *OverrideName = getenv("LLVM_OVERRIDE_PRODUCER")) 
    return OverrideName; 
  return DefaultName; 
} 
 
const char *kExpectedProducerName = getExpectedProducerName(); 
 
/// Stores the temporary state that is required to build an IR symbol table. 
struct Builder { 
  SmallVector<char, 0> &Symtab; 
  StringTableBuilder &StrtabBuilder; 
  StringSaver Saver; 
 
  // This ctor initializes a StringSaver using the passed in BumpPtrAllocator. 
  // The StringTableBuilder does not create a copy of any strings added to it, 
  // so this provides somewhere to store any strings that we create. 
  Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder, 
          BumpPtrAllocator &Alloc) 
      : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {} 
 
  DenseMap<const Comdat *, int> ComdatMap; 
  Mangler Mang; 
  Triple TT; 
 
  std::vector<storage::Comdat> Comdats; 
  std::vector<storage::Module> Mods; 
  std::vector<storage::Symbol> Syms; 
  std::vector<storage::Uncommon> Uncommons; 
 
  std::string COFFLinkerOpts; 
  raw_string_ostream COFFLinkerOptsOS{COFFLinkerOpts}; 
 
  std::vector<storage::Str> DependentLibraries; 
 
  void setStr(storage::Str &S, StringRef Value) { 
    S.Offset = StrtabBuilder.add(Value); 
    S.Size = Value.size(); 
  } 
 
  template <typename T> 
  void writeRange(storage::Range<T> &R, const std::vector<T> &Objs) { 
    R.Offset = Symtab.size(); 
    R.Size = Objs.size(); 
    Symtab.insert(Symtab.end(), reinterpret_cast<const char *>(Objs.data()), 
                  reinterpret_cast<const char *>(Objs.data() + Objs.size())); 
  } 
 
  Expected<int> getComdatIndex(const Comdat *C, const Module *M); 
 
  Error addModule(Module *M); 
  Error addSymbol(const ModuleSymbolTable &Msymtab, 
                  const SmallPtrSet<GlobalValue *, 8> &Used, 
                  ModuleSymbolTable::Symbol Sym); 
 
  Error build(ArrayRef<Module *> Mods); 
}; 
 
Error Builder::addModule(Module *M) { 
  if (M->getDataLayoutStr().empty()) 
    return make_error<StringError>("input module has no datalayout", 
                                   inconvertibleErrorCode()); 
 
  SmallPtrSet<GlobalValue *, 8> Used; 
  collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false); 
 
  ModuleSymbolTable Msymtab; 
  Msymtab.addModule(M); 
 
  storage::Module Mod; 
  Mod.Begin = Syms.size(); 
  Mod.End = Syms.size() + Msymtab.symbols().size(); 
  Mod.UncBegin = Uncommons.size(); 
  Mods.push_back(Mod); 
 
  if (TT.isOSBinFormatCOFF()) { 
    if (auto E = M->materializeMetadata()) 
      return E; 
    if (NamedMDNode *LinkerOptions = 
            M->getNamedMetadata("llvm.linker.options")) { 
      for (MDNode *MDOptions : LinkerOptions->operands()) 
        for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands()) 
          COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString(); 
    } 
  } 
 
  if (TT.isOSBinFormatELF()) { 
    if (auto E = M->materializeMetadata()) 
      return E; 
    if (NamedMDNode *N = M->getNamedMetadata("llvm.dependent-libraries")) { 
      for (MDNode *MDOptions : N->operands()) { 
        const auto OperandStr = 
            cast<MDString>(cast<MDNode>(MDOptions)->getOperand(0))->getString(); 
        storage::Str Specifier; 
        setStr(Specifier, OperandStr); 
        DependentLibraries.emplace_back(Specifier); 
      } 
    } 
  } 
 
  for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols()) 
    if (Error Err = addSymbol(Msymtab, Used, Msym)) 
      return Err; 
 
  return Error::success(); 
} 
 
Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) { 
  auto P = ComdatMap.insert(std::make_pair(C, Comdats.size())); 
  if (P.second) { 
    std::string Name; 
    if (TT.isOSBinFormatCOFF()) { 
      const GlobalValue *GV = M->getNamedValue(C->getName()); 
      if (!GV) 
        return make_error<StringError>("Could not find leader", 
                                       inconvertibleErrorCode()); 
      // Internal leaders do not affect symbol resolution, therefore they do not 
      // appear in the symbol table. 
      if (GV->hasLocalLinkage()) { 
        P.first->second = -1; 
        return -1; 
      } 
      llvm::raw_string_ostream OS(Name); 
      Mang.getNameWithPrefix(OS, GV, false); 
    } else { 
      Name = std::string(C->getName()); 
    } 
 
    storage::Comdat Comdat; 
    setStr(Comdat.Name, Saver.save(Name)); 
    Comdats.push_back(Comdat); 
  } 
 
  return P.first->second; 
} 
 
Error Builder::addSymbol(const ModuleSymbolTable &Msymtab, 
                         const SmallPtrSet<GlobalValue *, 8> &Used, 
                         ModuleSymbolTable::Symbol Msym) { 
  Syms.emplace_back(); 
  storage::Symbol &Sym = Syms.back(); 
  Sym = {}; 
 
  storage::Uncommon *Unc = nullptr; 
  auto Uncommon = [&]() -> storage::Uncommon & { 
    if (Unc) 
      return *Unc; 
    Sym.Flags |= 1 << storage::Symbol::FB_has_uncommon; 
    Uncommons.emplace_back(); 
    Unc = &Uncommons.back(); 
    *Unc = {}; 
    setStr(Unc->COFFWeakExternFallbackName, ""); 
    setStr(Unc->SectionName, ""); 
    return *Unc; 
  }; 
 
  SmallString<64> Name; 
  { 
    raw_svector_ostream OS(Name); 
    Msymtab.printSymbolName(OS, Msym); 
  } 
  setStr(Sym.Name, Saver.save(StringRef(Name))); 
 
  auto Flags = Msymtab.getSymbolFlags(Msym); 
  if (Flags & object::BasicSymbolRef::SF_Undefined) 
    Sym.Flags |= 1 << storage::Symbol::FB_undefined; 
  if (Flags & object::BasicSymbolRef::SF_Weak) 
    Sym.Flags |= 1 << storage::Symbol::FB_weak; 
  if (Flags & object::BasicSymbolRef::SF_Common) 
    Sym.Flags |= 1 << storage::Symbol::FB_common; 
  if (Flags & object::BasicSymbolRef::SF_Indirect) 
    Sym.Flags |= 1 << storage::Symbol::FB_indirect; 
  if (Flags & object::BasicSymbolRef::SF_Global) 
    Sym.Flags |= 1 << storage::Symbol::FB_global; 
  if (Flags & object::BasicSymbolRef::SF_FormatSpecific) 
    Sym.Flags |= 1 << storage::Symbol::FB_format_specific; 
  if (Flags & object::BasicSymbolRef::SF_Executable) 
    Sym.Flags |= 1 << storage::Symbol::FB_executable; 
 
  Sym.ComdatIndex = -1; 
  auto *GV = Msym.dyn_cast<GlobalValue *>(); 
  if (!GV) { 
    // Undefined module asm symbols act as GC roots and are implicitly used. 
    if (Flags & object::BasicSymbolRef::SF_Undefined) 
      Sym.Flags |= 1 << storage::Symbol::FB_used; 
    setStr(Sym.IRName, ""); 
    return Error::success(); 
  } 
 
  setStr(Sym.IRName, GV->getName()); 
 
  bool IsBuiltinFunc = false; 
 
  for (const char *LibcallName : LibcallRoutineNames) 
    if (GV->getName() == LibcallName) 
      IsBuiltinFunc = true; 
 
  if (Used.count(GV) || IsBuiltinFunc) 
    Sym.Flags |= 1 << storage::Symbol::FB_used; 
  if (GV->isThreadLocal()) 
    Sym.Flags |= 1 << storage::Symbol::FB_tls; 
  if (GV->hasGlobalUnnamedAddr()) 
    Sym.Flags |= 1 << storage::Symbol::FB_unnamed_addr; 
  if (GV->canBeOmittedFromSymbolTable()) 
    Sym.Flags |= 1 << storage::Symbol::FB_may_omit; 
  Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility; 
 
  if (Flags & object::BasicSymbolRef::SF_Common) { 
    auto *GVar = dyn_cast<GlobalVariable>(GV); 
    if (!GVar) 
      return make_error<StringError>("Only variables can have common linkage!", 
                                     inconvertibleErrorCode()); 
    Uncommon().CommonSize = GV->getParent()->getDataLayout().getTypeAllocSize( 
        GV->getType()->getElementType()); 
    Uncommon().CommonAlign = GVar->getAlignment(); 
  } 
 
  const GlobalObject *Base = GV->getBaseObject(); 
  if (!Base) 
    return make_error<StringError>("Unable to determine comdat of alias!", 
                                   inconvertibleErrorCode()); 
  if (const Comdat *C = Base->getComdat()) { 
    Expected<int> ComdatIndexOrErr = getComdatIndex(C, GV->getParent()); 
    if (!ComdatIndexOrErr) 
      return ComdatIndexOrErr.takeError(); 
    Sym.ComdatIndex = *ComdatIndexOrErr; 
  } 
 
  if (TT.isOSBinFormatCOFF()) { 
    emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang); 
 
    if ((Flags & object::BasicSymbolRef::SF_Weak) && 
        (Flags & object::BasicSymbolRef::SF_Indirect)) { 
      auto *Fallback = dyn_cast<GlobalValue>( 
          cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts()); 
      if (!Fallback) 
        return make_error<StringError>("Invalid weak external", 
                                       inconvertibleErrorCode()); 
      std::string FallbackName; 
      raw_string_ostream OS(FallbackName); 
      Msymtab.printSymbolName(OS, Fallback); 
      OS.flush(); 
      setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName)); 
    } 
  } 
 
  if (!Base->getSection().empty()) 
    setStr(Uncommon().SectionName, Saver.save(Base->getSection())); 
 
  return Error::success(); 
} 
 
Error Builder::build(ArrayRef<Module *> IRMods) { 
  storage::Header Hdr; 
 
  assert(!IRMods.empty()); 
  Hdr.Version = storage::Header::kCurrentVersion; 
  setStr(Hdr.Producer, kExpectedProducerName); 
  setStr(Hdr.TargetTriple, IRMods[0]->getTargetTriple()); 
  setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName()); 
  TT = Triple(IRMods[0]->getTargetTriple()); 
 
  for (auto *M : IRMods) 
    if (Error Err = addModule(M)) 
      return Err; 
 
  COFFLinkerOptsOS.flush(); 
  setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts)); 
 
  // We are about to fill in the header's range fields, so reserve space for it 
  // and copy it in afterwards. 
  Symtab.resize(sizeof(storage::Header)); 
  writeRange(Hdr.Modules, Mods); 
  writeRange(Hdr.Comdats, Comdats); 
  writeRange(Hdr.Symbols, Syms); 
  writeRange(Hdr.Uncommons, Uncommons); 
  writeRange(Hdr.DependentLibraries, DependentLibraries); 
  *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr; 
  return Error::success(); 
} 
 
} // end anonymous namespace 
 
Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab, 
                      StringTableBuilder &StrtabBuilder, 
                      BumpPtrAllocator &Alloc) { 
  return Builder(Symtab, StrtabBuilder, Alloc).build(Mods); 
} 
 
// Upgrade a vector of bitcode modules created by an old version of LLVM by 
// creating an irsymtab for them in the current format. 
static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) { 
  FileContents FC; 
 
  LLVMContext Ctx; 
  std::vector<Module *> Mods; 
  std::vector<std::unique_ptr<Module>> OwnedMods; 
  for (auto BM : BMs) { 
    Expected<std::unique_ptr<Module>> MOrErr = 
        BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true, 
                         /*IsImporting*/ false); 
    if (!MOrErr) 
      return MOrErr.takeError(); 
 
    Mods.push_back(MOrErr->get()); 
    OwnedMods.push_back(std::move(*MOrErr)); 
  } 
 
  StringTableBuilder StrtabBuilder(StringTableBuilder::RAW); 
  BumpPtrAllocator Alloc; 
  if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc)) 
    return std::move(E); 
 
  StrtabBuilder.finalizeInOrder(); 
  FC.Strtab.resize(StrtabBuilder.getSize()); 
  StrtabBuilder.write((uint8_t *)FC.Strtab.data()); 
 
  FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()}, 
                  {FC.Strtab.data(), FC.Strtab.size()}}; 
  return std::move(FC); 
} 
 
Expected<FileContents> irsymtab::readBitcode(const BitcodeFileContents &BFC) { 
  if (BFC.Mods.empty()) 
    return make_error<StringError>("Bitcode file does not contain any modules", 
                                   inconvertibleErrorCode()); 
 
  if (BFC.StrtabForSymtab.empty() || 
      BFC.Symtab.size() < sizeof(storage::Header)) 
    return upgrade(BFC.Mods); 
 
  // We cannot use the regular reader to read the version and producer, because 
  // it will expect the header to be in the current format. The only thing we 
  // can rely on is that the version and producer will be present as the first 
  // struct elements. 
  auto *Hdr = reinterpret_cast<const storage::Header *>(BFC.Symtab.data()); 
  unsigned Version = Hdr->Version; 
  StringRef Producer = Hdr->Producer.get(BFC.StrtabForSymtab); 
  if (Version != storage::Header::kCurrentVersion || 
      Producer != kExpectedProducerName) 
    return upgrade(BFC.Mods); 
 
  FileContents FC; 
  FC.TheReader = {{BFC.Symtab.data(), BFC.Symtab.size()}, 
                  {BFC.StrtabForSymtab.data(), BFC.StrtabForSymtab.size()}}; 
 
  // Finally, make sure that the number of modules in the symbol table matches 
  // the number of modules in the bitcode file. If they differ, it may mean that 
  // the bitcode file was created by binary concatenation, so we need to create 
  // a new symbol table from scratch. 
  if (FC.TheReader.getNumModules() != BFC.Mods.size()) 
    return upgrade(std::move(BFC.Mods)); 
 
  return std::move(FC); 
}