298 changes: 298 additions & 0 deletions llvm/include/llvm/Object/IRSymtab.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,298 @@
//===- IRSymtab.h - data definitions for IR symbol tables -------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains data definitions and a reader and builder for a symbol
// table for LLVM IR. Its purpose is to allow linkers and other consumers of
// bitcode files to efficiently read the symbol table for symbol resolution
// purposes without needing to construct a module in memory.
//
// As with most object files the symbol table has two parts: the symbol table
// itself and a string table which is referenced by the symbol table.
//
// A symbol table corresponds to a single bitcode file, which may consist of
// multiple modules, so symbol tables may likewise contain symbols for multiple
// modules.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_OBJECT_IRSYMTAB_H
#define LLVM_OBJECT_IRSYMTAB_H

#include "llvm/ADT/ArrayRef.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/Object/SymbolicFile.h"
#include "llvm/Support/Endian.h"

namespace llvm {
namespace irsymtab {
namespace storage {

// The data structures in this namespace define the low-level serialization
// format. Clients that just want to read a symbol table should use the
// irsymtab::Reader class.

typedef support::ulittle32_t Word;

/// A reference to a string in the string table.
struct Str {
Word Offset;
StringRef get(StringRef Strtab) const {
return Strtab.data() + Offset;
}
};

/// A reference to a range of objects in the symbol table.
template <typename T> struct Range {
Word Offset, Size;
ArrayRef<T> get(StringRef Symtab) const {
return {reinterpret_cast<const T *>(Symtab.data() + Offset), Size};
}
};

/// Describes the range of a particular module's symbols within the symbol
/// table.
struct Module {
Word Begin, End;
};

/// This is equivalent to an IR comdat.
struct Comdat {
Str Name;
};

/// Contains the information needed by linkers for symbol resolution, as well as
/// by the LTO implementation itself.
struct Symbol {
/// The mangled symbol name.
Str Name;

/// The unmangled symbol name, or the empty string if this is not an IR
/// symbol.
Str IRName;

/// The index into Header::Comdats, or -1 if not a comdat member.
Word ComdatIndex;

Word Flags;
enum FlagBits {
FB_visibility, // 2 bits
FB_undefined = FB_visibility + 2,
FB_weak,
FB_common,
FB_indirect,
FB_used,
FB_tls,
FB_may_omit,
FB_global,
FB_format_specific,
FB_unnamed_addr,
};

/// The index into the Uncommon table, or -1 if this symbol does not have an
/// Uncommon.
Word UncommonIndex;
};

/// This data structure contains rarely used symbol fields and is optionally
/// referenced by a Symbol.
struct Uncommon {
Word CommonSize, CommonAlign;

/// COFF-specific: the name of the symbol that a weak external resolves to
/// if not defined.
Str COFFWeakExternFallbackName;
};

struct Header {
Range<Module> Modules;
Range<Comdat> Comdats;
Range<Symbol> Symbols;
Range<Uncommon> Uncommons;

Str SourceFileName;

/// COFF-specific: linker directives.
Str COFFLinkerOpts;
};

}

/// Fills in Symtab and Strtab with a valid symbol and string table for Mods.
Error build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
SmallVector<char, 0> &Strtab);

/// This represents a symbol that has been read from a storage::Symbol and
/// possibly a storage::Uncommon.
struct Symbol {
// Copied from storage::Symbol.
StringRef Name, IRName;
int ComdatIndex;
uint32_t Flags;

// Copied from storage::Uncommon.
uint32_t CommonSize, CommonAlign;
StringRef COFFWeakExternFallbackName;

/// Returns the mangled symbol name.
StringRef getName() const { return Name; }

/// Returns the unmangled symbol name, or the empty string if this is not an
/// IR symbol.
StringRef getIRName() const { return IRName; }

/// Returns the index into the comdat table (see Reader::getComdatTable()), or
/// -1 if not a comdat member.
int getComdatIndex() const { return ComdatIndex; }

using S = storage::Symbol;
GlobalValue::VisibilityTypes getVisibility() const {
return GlobalValue::VisibilityTypes((Flags >> S::FB_visibility) & 3);
}
bool isUndefined() const { return (Flags >> S::FB_undefined) & 1; }
bool isWeak() const { return (Flags >> S::FB_weak) & 1; }
bool isCommon() const { return (Flags >> S::FB_common) & 1; }
bool isIndirect() const { return (Flags >> S::FB_indirect) & 1; }
bool isUsed() const { return (Flags >> S::FB_used) & 1; }
bool isTLS() const { return (Flags >> S::FB_tls) & 1; }
bool canBeOmittedFromSymbolTable() const {
return (Flags >> S::FB_may_omit) & 1;
}
bool isGlobal() const { return (Flags >> S::FB_global) & 1; }
bool isFormatSpecific() const { return (Flags >> S::FB_format_specific) & 1; }
bool isUnnamedAddr() const { return (Flags >> S::FB_unnamed_addr) & 1; }

size_t getCommonSize() const {
assert(isCommon());
return CommonSize;
}
uint32_t getCommonAlignment() const {
assert(isCommon());
return CommonAlign;
}

/// COFF-specific: for weak externals, returns the name of the symbol that is
/// used as a fallback if the weak external remains undefined.
StringRef getCOFFWeakExternalFallback() const {
assert(isWeak() && isIndirect());
return COFFWeakExternFallbackName;
}
};

/// This class can be used to read a Symtab and Strtab produced by
/// irsymtab::build.
class Reader {
StringRef Symtab, Strtab;

ArrayRef<storage::Module> Modules;
ArrayRef<storage::Comdat> Comdats;
ArrayRef<storage::Symbol> Symbols;
ArrayRef<storage::Uncommon> Uncommons;

StringRef str(storage::Str S) const { return S.get(Strtab); }
template <typename T> ArrayRef<T> range(storage::Range<T> R) const {
return R.get(Symtab);
}
const storage::Header &header() const {
return *reinterpret_cast<const storage::Header *>(Symtab.data());
}

public:
class SymbolRef;

Reader() = default;
Reader(StringRef Symtab, StringRef Strtab) : Symtab(Symtab), Strtab(Strtab) {
Modules = range(header().Modules);
Comdats = range(header().Comdats);
Symbols = range(header().Symbols);
Uncommons = range(header().Uncommons);
}

typedef iterator_range<object::content_iterator<SymbolRef>> symbol_range;

/// Returns the symbol table for the entire bitcode file.
/// The symbols enumerated by this method are ephemeral, but they can be
/// copied into an irsymtab::Symbol object.
symbol_range symbols() const;

/// Returns a slice of the symbol table for the I'th module in the file.
/// The symbols enumerated by this method are ephemeral, but they can be
/// copied into an irsymtab::Symbol object.
symbol_range module_symbols(unsigned I) const;

/// Returns the source file path specified at compile time.
StringRef getSourceFileName() const { return str(header().SourceFileName); }

/// Returns a table with all the comdats used by this file.
std::vector<StringRef> getComdatTable() const {
std::vector<StringRef> ComdatTable;
ComdatTable.reserve(Comdats.size());
for (auto C : Comdats)
ComdatTable.push_back(str(C.Name));
return ComdatTable;
}

/// COFF-specific: returns linker options specified in the input file.
StringRef getCOFFLinkerOpts() const { return str(header().COFFLinkerOpts); }
};

/// Ephemeral symbols produced by Reader::symbols() and
/// Reader::module_symbols().
class Reader::SymbolRef : public Symbol {
const storage::Symbol *SymI, *SymE;
const Reader *R;

public:
SymbolRef(const storage::Symbol *SymI, const storage::Symbol *SymE,
const Reader *R)
: SymI(SymI), SymE(SymE), R(R) {
read();
}

void read() {
if (SymI == SymE)
return;

Name = R->str(SymI->Name);
IRName = R->str(SymI->IRName);
ComdatIndex = SymI->ComdatIndex;
Flags = SymI->Flags;

uint32_t UncI = SymI->UncommonIndex;
if (UncI != -1u) {
const storage::Uncommon &Unc = R->Uncommons[UncI];
CommonSize = Unc.CommonSize;
CommonAlign = Unc.CommonAlign;
COFFWeakExternFallbackName = R->str(Unc.COFFWeakExternFallbackName);
}
}
void moveNext() {
++SymI;
read();
}

bool operator==(const SymbolRef &Other) const { return SymI == Other.SymI; }
};

inline Reader::symbol_range Reader::symbols() const {
return {SymbolRef(Symbols.begin(), Symbols.end(), this),
SymbolRef(Symbols.end(), Symbols.end(), this)};
}

inline Reader::symbol_range Reader::module_symbols(unsigned I) const {
const storage::Module &M = Modules[I];
const storage::Symbol *MBegin = Symbols.begin() + M.Begin,
*MEnd = Symbols.begin() + M.End;
return {SymbolRef(MBegin, MEnd, this), SymbolRef(MEnd, MEnd, this)};
}

}

}

#endif
212 changes: 85 additions & 127 deletions llvm/lib/LTO/LTO.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -305,14 +305,6 @@ void llvm::thinLTOInternalizeAndPromoteInIndex(
thinLTOInternalizeAndPromoteGUID(I.second, I.first, isExported);
}

struct InputFile::InputModule {
BitcodeModule BM;
std::unique_ptr<Module> Mod;

// The range of ModuleSymbolTable entries for this input module.
size_t SymBegin, SymEnd;
};

// Requires a destructor for std::vector<InputModule>.
InputFile::~InputFile() = default;

Expand All @@ -333,87 +325,51 @@ Expected<std::unique_ptr<InputFile>> InputFile::create(MemoryBufferRef Object) {
return make_error<StringError>("Bitcode file does not contain any modules",
inconvertibleErrorCode());

// Create an InputModule for each module in the InputFile, and add it to the
// ModuleSymbolTable.
File->Mods = *BMsOrErr;

LLVMContext Ctx;
std::vector<Module *> Mods;
std::vector<std::unique_ptr<Module>> OwnedMods;
for (auto BM : *BMsOrErr) {
Expected<std::unique_ptr<Module>> MOrErr =
BM.getLazyModule(File->Ctx, /*ShouldLazyLoadMetadata*/ true,
BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
/*IsImporting*/ false);
if (!MOrErr)
return MOrErr.takeError();

size_t SymBegin = File->SymTab.symbols().size();
File->SymTab.addModule(MOrErr->get());
size_t SymEnd = File->SymTab.symbols().size();

for (const auto &C : (*MOrErr)->getComdatSymbolTable()) {
auto P = File->ComdatMap.insert(
std::make_pair(&C.second, File->Comdats.size()));
assert(P.second);
(void)P;
File->Comdats.push_back(C.first());
}

File->Mods.push_back({BM, std::move(*MOrErr), SymBegin, SymEnd});
}

return std::move(File);
}
if ((*MOrErr)->getDataLayoutStr().empty())
return make_error<StringError>("input module has no datalayout",
inconvertibleErrorCode());

Expected<int> InputFile::Symbol::getComdatIndex() const {
if (!isGV())
return -1;
const GlobalObject *GO = getGV()->getBaseObject();
if (!GO)
return make_error<StringError>("Unable to determine comdat of alias!",
inconvertibleErrorCode());
if (const Comdat *C = GO->getComdat()) {
auto I = File->ComdatMap.find(C);
assert(I != File->ComdatMap.end());
return I->second;
Mods.push_back(MOrErr->get());
OwnedMods.push_back(std::move(*MOrErr));
}
return -1;
}

Expected<std::string> InputFile::getLinkerOpts() {
std::string LinkerOpts;
raw_string_ostream LOS(LinkerOpts);
// Extract linker options from module metadata.
for (InputModule &Mod : Mods) {
std::unique_ptr<Module> &M = Mod.Mod;
if (auto E = M->materializeMetadata())
return std::move(E);
if (Metadata *Val = M->getModuleFlag("Linker Options")) {
MDNode *LinkerOptions = cast<MDNode>(Val);
for (const MDOperand &MDOptions : LinkerOptions->operands())
for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
LOS << " " << cast<MDString>(MDOption)->getString();
}
SmallVector<char, 0> Symtab;
if (Error E = irsymtab::build(Mods, Symtab, File->Strtab))
return std::move(E);

irsymtab::Reader R({Symtab.data(), Symtab.size()},
{File->Strtab.data(), File->Strtab.size()});
File->SourceFileName = R.getSourceFileName();
File->COFFLinkerOpts = R.getCOFFLinkerOpts();
File->ComdatTable = R.getComdatTable();

for (unsigned I = 0; I != Mods.size(); ++I) {
size_t Begin = File->Symbols.size();
for (const irsymtab::Reader::SymbolRef &Sym : R.module_symbols(I))
// Skip symbols that are irrelevant to LTO. Note that this condition needs
// to match the one in Skip() in LTO::addRegularLTO().
if (Sym.isGlobal() && !Sym.isFormatSpecific())
File->Symbols.push_back(Sym);
File->ModuleSymIndices.push_back({Begin, File->Symbols.size()});
}

// Synthesize export flags for symbols with dllexport storage.
const Triple TT(Mods[0].Mod->getTargetTriple());
Mangler M;
for (const ModuleSymbolTable::Symbol &Sym : SymTab.symbols())
if (auto *GV = Sym.dyn_cast<GlobalValue*>())
emitLinkerFlagsForGlobalCOFF(LOS, GV, TT, M);
LOS.flush();
return LinkerOpts;
return std::move(File);
}

StringRef InputFile::getName() const {
return Mods[0].BM.getModuleIdentifier();
}

StringRef InputFile::getSourceFileName() const {
return Mods[0].Mod->getSourceFileName();
}

iterator_range<InputFile::symbol_iterator>
InputFile::module_symbols(InputModule &IM) {
return llvm::make_range(
symbol_iterator(SymTab.symbols().data() + IM.SymBegin, SymTab, this),
symbol_iterator(SymTab.symbols().data() + IM.SymEnd, SymTab, this));
return Mods[0].getModuleIdentifier();
}

LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
Expand All @@ -437,21 +393,17 @@ LTO::LTO(Config Conf, ThinBackend Backend,
LTO::~LTO() = default;

// Add the given symbol to the GlobalResolutions map, and resolve its partition.
void LTO::addSymbolToGlobalRes(SmallPtrSet<GlobalValue *, 8> &Used,
const InputFile::Symbol &Sym,
void LTO::addSymbolToGlobalRes(const InputFile::Symbol &Sym,
SymbolResolution Res, unsigned Partition) {
GlobalValue *GV = Sym.isGV() ? Sym.getGV() : nullptr;

auto &GlobalRes = GlobalResolutions[Sym.getName()];
if (GV) {
GlobalRes.UnnamedAddr &= GV->hasGlobalUnnamedAddr();
if (Res.Prevailing)
GlobalRes.IRName = GV->getName();
}
GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
if (Res.Prevailing)
GlobalRes.IRName = Sym.getIRName();

// Set the partition to external if we know it is used elsewhere, e.g.
// it is visible to a regular object, is referenced from llvm.compiler_used,
// or was already recorded as being referenced from a different partition.
if (Res.VisibleToRegularObj || (GV && Used.count(GV)) ||
if (Res.VisibleToRegularObj || Sym.isUsed() ||
(GlobalRes.Partition != GlobalResolution::Unknown &&
GlobalRes.Partition != Partition)) {
GlobalRes.Partition = GlobalResolution::External;
Expand Down Expand Up @@ -495,41 +447,32 @@ Error LTO::add(std::unique_ptr<InputFile> Input,
writeToResolutionFile(*Conf.ResolutionFile, Input.get(), Res);

const SymbolResolution *ResI = Res.begin();
for (InputFile::InputModule &IM : Input->Mods)
if (Error Err = addModule(*Input, IM, ResI, Res.end()))
for (unsigned I = 0; I != Input->Mods.size(); ++I)
if (Error Err = addModule(*Input, I, ResI, Res.end()))
return Err;

assert(ResI == Res.end());
return Error::success();
}

Error LTO::addModule(InputFile &Input, InputFile::InputModule &IM,
Error LTO::addModule(InputFile &Input, unsigned ModI,
const SymbolResolution *&ResI,
const SymbolResolution *ResE) {
// FIXME: move to backend
Module &M = *IM.Mod;

if (M.getDataLayoutStr().empty())
return make_error<StringError>("input module has no datalayout",
inconvertibleErrorCode());

if (!Conf.OverrideTriple.empty())
M.setTargetTriple(Conf.OverrideTriple);
else if (M.getTargetTriple().empty())
M.setTargetTriple(Conf.DefaultTriple);

Expected<bool> HasThinLTOSummary = IM.BM.hasSummary();
Expected<bool> HasThinLTOSummary = Input.Mods[ModI].hasSummary();
if (!HasThinLTOSummary)
return HasThinLTOSummary.takeError();

auto ModSyms = Input.module_symbols(ModI);
if (*HasThinLTOSummary)
return addThinLTO(IM.BM, M, Input.module_symbols(IM), ResI, ResE);
return addThinLTO(Input.Mods[ModI], ModSyms, ResI, ResE);
else
return addRegularLTO(IM.BM, ResI, ResE);
return addRegularLTO(Input.Mods[ModI], ModSyms, ResI, ResE);
}

// Add a regular LTO object to the link.
Error LTO::addRegularLTO(BitcodeModule BM, const SymbolResolution *&ResI,
Error LTO::addRegularLTO(BitcodeModule BM,
ArrayRef<InputFile::Symbol> Syms,
const SymbolResolution *&ResI,
const SymbolResolution *ResE) {
if (!RegularLTO.CombinedModule) {
RegularLTO.CombinedModule =
Expand All @@ -550,9 +493,6 @@ Error LTO::addRegularLTO(BitcodeModule BM, const SymbolResolution *&ResI,
ModuleSymbolTable SymTab;
SymTab.addModule(&M);

SmallPtrSet<GlobalValue *, 8> Used;
collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);

std::vector<GlobalValue *> Keep;

for (GlobalVariable &GV : M.globals())
Expand All @@ -564,17 +504,35 @@ Error LTO::addRegularLTO(BitcodeModule BM, const SymbolResolution *&ResI,
if (GlobalObject *GO = GA.getBaseObject())
AliasedGlobals.insert(GO);

for (const InputFile::Symbol &Sym :
make_range(InputFile::symbol_iterator(SymTab.symbols().begin(), SymTab,
nullptr),
InputFile::symbol_iterator(SymTab.symbols().end(), SymTab,
nullptr))) {
// In this function we need IR GlobalValues matching the symbols in Syms
// (which is not backed by a module), so we need to enumerate them in the same
// order. The symbol enumeration order of a ModuleSymbolTable intentionally
// matches the order of an irsymtab, but when we read the irsymtab in
// InputFile::create we omit some symbols that are irrelevant to LTO. The
// Skip() function skips the same symbols from the module as InputFile does
// from the symbol table.
auto MsymI = SymTab.symbols().begin(), MsymE = SymTab.symbols().end();
auto Skip = [&]() {
while (MsymI != MsymE) {
auto Flags = SymTab.getSymbolFlags(*MsymI);
if ((Flags & object::BasicSymbolRef::SF_Global) &&
!(Flags & object::BasicSymbolRef::SF_FormatSpecific))
return;
++MsymI;
}
};
Skip();

for (const InputFile::Symbol &Sym : Syms) {
assert(ResI != ResE);
SymbolResolution Res = *ResI++;
addSymbolToGlobalRes(Used, Sym, Res, 0);
addSymbolToGlobalRes(Sym, Res, 0);

if (Sym.isGV()) {
GlobalValue *GV = Sym.getGV();
assert(MsymI != MsymE);
ModuleSymbolTable::Symbol Msym = *MsymI++;
Skip();

if (GlobalValue *GV = Msym.dyn_cast<GlobalValue *>()) {
if (Res.Prevailing) {
if (Sym.isUndefined())
continue;
Expand Down Expand Up @@ -612,30 +570,26 @@ Error LTO::addRegularLTO(BitcodeModule BM, const SymbolResolution *&ResI,
if (Sym.isCommon()) {
// FIXME: We should figure out what to do about commons defined by asm.
// For now they aren't reported correctly by ModuleSymbolTable.
auto &CommonRes = RegularLTO.Commons[Sym.getGV()->getName()];
auto &CommonRes = RegularLTO.Commons[Sym.getIRName()];
CommonRes.Size = std::max(CommonRes.Size, Sym.getCommonSize());
CommonRes.Align = std::max(CommonRes.Align, Sym.getCommonAlignment());
CommonRes.Prevailing |= Res.Prevailing;
}

// FIXME: use proposed local attribute for FinalDefinitionInLinkageUnit.
}
assert(MsymI == MsymE);

return RegularLTO.Mover->move(std::move(*MOrErr), Keep,
[](GlobalValue &, IRMover::ValueAdder) {},
/* IsPerformingImport */ false);
}

// Add a ThinLTO object to the link.
// FIXME: This function should not need to take as many parameters once we have
// a bitcode symbol table.
Error LTO::addThinLTO(BitcodeModule BM, Module &M,
iterator_range<InputFile::symbol_iterator> Syms,
Error LTO::addThinLTO(BitcodeModule BM,
ArrayRef<InputFile::Symbol> Syms,
const SymbolResolution *&ResI,
const SymbolResolution *ResE) {
SmallPtrSet<GlobalValue *, 8> Used;
collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);

Expected<std::unique_ptr<ModuleSummaryIndex>> SummaryOrErr = BM.getSummary();
if (!SummaryOrErr)
return SummaryOrErr.takeError();
Expand All @@ -645,11 +599,15 @@ Error LTO::addThinLTO(BitcodeModule BM, Module &M,
for (const InputFile::Symbol &Sym : Syms) {
assert(ResI != ResE);
SymbolResolution Res = *ResI++;
addSymbolToGlobalRes(Used, Sym, Res, ThinLTO.ModuleMap.size() + 1);
addSymbolToGlobalRes(Sym, Res, ThinLTO.ModuleMap.size() + 1);

if (Res.Prevailing && Sym.isGV())
ThinLTO.PrevailingModuleForGUID[Sym.getGV()->getGUID()] =
BM.getModuleIdentifier();
if (Res.Prevailing) {
if (!Sym.getIRName().empty()) {
auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
}
}
}

if (!ThinLTO.ModuleMap.insert({BM.getModuleIdentifier(), BM}).second)
Expand Down
1 change: 1 addition & 0 deletions llvm/lib/Object/CMakeLists.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ add_llvm_library(LLVMObject
ELFObjectFile.cpp
Error.cpp
IRObjectFile.cpp
IRSymtab.cpp
MachOObjectFile.cpp
MachOUniversal.cpp
ModuleSummaryIndexObjectFile.cpp
Expand Down
228 changes: 228 additions & 0 deletions llvm/lib/Object/IRSymtab.cpp
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,228 @@
//===- IRSymtab.cpp - implementation of IR symbol tables --------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Object/IRSymtab.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ModuleSymbolTable.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/StringSaver.h"

using namespace llvm;
using namespace irsymtab;

namespace {

/// Stores the temporary state that is required to build an IR symbol table.
struct Builder {
SmallVector<char, 0> &Symtab;
SmallVector<char, 0> &Strtab;
Builder(SmallVector<char, 0> &Symtab, SmallVector<char, 0> &Strtab)
: Symtab(Symtab), Strtab(Strtab) {}

StringTableBuilder StrtabBuilder{StringTableBuilder::ELF};

BumpPtrAllocator Alloc;
StringSaver Saver{Alloc};

DenseMap<const Comdat *, unsigned> ComdatMap;
ModuleSymbolTable Msymtab;
SmallPtrSet<GlobalValue *, 8> Used;
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};

void setStr(storage::Str &S, StringRef Value) {
S.Offset = StrtabBuilder.add(Value);
}
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()));
}

Error addModule(Module *M);
Error addSymbol(ModuleSymbolTable::Symbol Sym);

Error build(ArrayRef<Module *> Mods);
};

Error Builder::addModule(Module *M) {
collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false);

storage::Module Mod;
Mod.Begin = Msymtab.symbols().size();
Msymtab.addModule(M);
Mod.End = Msymtab.symbols().size();
Mods.push_back(Mod);

if (TT.isOSBinFormatCOFF()) {
if (auto E = M->materializeMetadata())
return E;
if (Metadata *Val = M->getModuleFlag("Linker Options")) {
MDNode *LinkerOptions = cast<MDNode>(Val);
for (const MDOperand &MDOptions : LinkerOptions->operands())
for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString();
}
}

return Error::success();
}

Error Builder::addSymbol(ModuleSymbolTable::Symbol Msym) {
Syms.emplace_back();
storage::Symbol &Sym = Syms.back();
Sym = {};

Sym.UncommonIndex = -1;
storage::Uncommon *Unc = nullptr;
auto Uncommon = [&]() -> storage::Uncommon & {
if (Unc)
return *Unc;
Sym.UncommonIndex = Uncommons.size();
Uncommons.emplace_back();
Unc = &Uncommons.back();
*Unc = {};
setStr(Unc->COFFWeakExternFallbackName, "");
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;

Sym.ComdatIndex = -1;
auto *GV = Msym.dyn_cast<GlobalValue *>();
if (!GV) {
setStr(Sym.IRName, "");
return Error::success();
}

setStr(Sym.IRName, GV->getName());

if (Used.count(GV))
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 (canBeOmittedFromSymbolTable(GV))
Sym.Flags |= 1 << storage::Symbol::FB_may_omit;
Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility;

if (Flags & object::BasicSymbolRef::SF_Common) {
Uncommon().CommonSize = GV->getParent()->getDataLayout().getTypeAllocSize(
GV->getType()->getElementType());
Uncommon().CommonAlign = GV->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()) {
auto P = ComdatMap.insert(std::make_pair(C, Comdats.size()));
Sym.ComdatIndex = P.first->second;

if (P.second) {
storage::Comdat Comdat;
setStr(Comdat.Name, C->getName());
Comdats.push_back(Comdat);
}
}

if (TT.isOSBinFormatCOFF()) {
emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang);

if ((Flags & object::BasicSymbolRef::SF_Weak) &&
(Flags & object::BasicSymbolRef::SF_Indirect)) {
std::string FallbackName;
raw_string_ostream OS(FallbackName);
Msymtab.printSymbolName(
OS, cast<GlobalValue>(
cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts()));
OS.flush();
setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName));
}
}

return Error::success();
}

Error Builder::build(ArrayRef<Module *> IRMods) {
storage::Header Hdr;

assert(!IRMods.empty());
setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName());
TT = Triple(IRMods[0]->getTargetTriple());

// This adds the symbols for each module to Msymtab.
for (auto *M : IRMods)
if (Error Err = addModule(M))
return Err;

for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols())
if (Error Err = addSymbol(Msym))
return Err;

COFFLinkerOptsOS.flush();
setStr(Hdr.COFFLinkerOpts, 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);

*reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr;

raw_svector_ostream OS(Strtab);
StrtabBuilder.finalizeInOrder();
StrtabBuilder.write(OS);

return Error::success();
}

} // anonymous namespace

Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
SmallVector<char, 0> &Strtab) {
return Builder(Symtab, Strtab).build(Mods);
}
4 changes: 2 additions & 2 deletions llvm/tools/gold/gold-plugin.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -465,7 +465,7 @@ static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
EC == object::object_error::bitcode_section_not_found)
*claimed = 0;
else
message(LDPL_ERROR,
message(LDPL_FATAL,
"LLVM gold plugin has failed to create LTO module: %s",
EI.message().c_str());
});
Expand Down Expand Up @@ -536,7 +536,7 @@ static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,

sym.size = 0;
sym.comdat_key = nullptr;
int CI = check(Sym.getComdatIndex());
int CI = Sym.getComdatIndex();
if (CI != -1) {
StringRef C = Obj->getComdatTable()[CI];
sym.comdat_key = strdup(C.str().c_str());
Expand Down