// Merge identical COMDAT sections.
// Two sections are considered the same if their section headers,
// contents and relocations are all the same.
void ICF::run(const std::vector<Chunk *> &Vec) {
// Collect only mergeable sections and group by hash value.
parallel_for_each(Vec.begin(), Vec.end(), [&](Chunk *C) {
if (auto *SC = dyn_cast<SectionChunk>(C)) {
bool Global = SC->Sym && SC->Sym->isExternal();
bool Writable = SC->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_WRITE;
if (SC->isCOMDAT() && SC->isLive() && Global && !Writable)
SC->GroupID = getHash(SC) | (uint64_t(1) << 63);
}
});
std::vector<SectionChunk *> Chunks;
for (Chunk *C : Vec) {
if (auto *SC = dyn_cast<SectionChunk>(C)) {
if (SC->GroupID) {
Chunks.push_back(SC);
} else {
SC->GroupID = NextID++;
}
}
}
// From now on, sections in Chunks are ordered so that sections in
// the same group are consecutive in the vector.
std::sort(Chunks.begin(), Chunks.end(),
[](SectionChunk *A, SectionChunk *B) {
return A->GroupID < B->GroupID;
});
// Split groups until we get a convergence.
int Cnt = 1;
forEachGroup(Chunks, equalsConstant);
for (;;) {
if (!forEachGroup(Chunks, equalsVariable))
break;
++Cnt;
}
if (Config->Verbose)
llvm::outs() << "\nICF needed " << Cnt << " iterations.\n";
// Merge sections in the same group.
for (auto It = Chunks.begin(), End = Chunks.end(); It != End;) {
SectionChunk *Head = *It++;
auto Bound = std::find_if(It, End, [&](SectionChunk *SC) {
return Head->GroupID != SC->GroupID;
});
if (It == Bound)
continue;
if (Config->Verbose)
llvm::outs() << "Selected " << Head->getDebugName() << "\n";
while (It != Bound) {
SectionChunk *SC = *It++;
if (Config->Verbose)
llvm::outs() << " Removed " << SC->getDebugName() << "\n";
Head->replace(SC);
}
}
}
static ArrayRef<uint8_t> getDebugSection(ObjectFile *File, StringRef SecName) {
SectionChunk *Sec = findByName(File->getDebugChunks(), SecName);
if (!Sec)
return {};
// First 4 bytes are section magic.
ArrayRef<uint8_t> Data = Sec->getContents();
if (Data.size() < 4)
fatal(SecName + " too short");
if (read32le(Data.data()) != COFF::DEBUG_SECTION_MAGIC)
fatal(SecName + " has an invalid magic");
return Data.slice(4);
}
// Set live bit on for each reachable chunk. Unmarked (unreachable)
// COMDAT chunks will be ignored by Writer, so they will be excluded
// from the final output.
void markLive(ArrayRef<Chunk *> Chunks) {
ScopedTimer T(GCTimer);
// We build up a worklist of sections which have been marked as live. We only
// push into the worklist when we discover an unmarked section, and we mark
// as we push, so sections never appear twice in the list.
SmallVector<SectionChunk *, 256> Worklist;
// COMDAT section chunks are dead by default. Add non-COMDAT chunks.
for (Chunk *C : Chunks)
if (auto *SC = dyn_cast<SectionChunk>(C))
if (SC->isLive())
Worklist.push_back(SC);
auto Enqueue = [&](SectionChunk *C) {
if (C->isLive())
return;
C->markLive();
Worklist.push_back(C);
};
auto AddSym = [&](Symbol *B) {
if (auto *Sym = dyn_cast<DefinedRegular>(B))
Enqueue(Sym->getChunk());
else if (auto *Sym = dyn_cast<DefinedImportData>(B))
Sym->File->Live = true;
else if (auto *Sym = dyn_cast<DefinedImportThunk>(B))
Sym->WrappedSym->File->Live = Sym->WrappedSym->File->ThunkLive = true;
};
// Add GC root chunks.
for (Symbol *B : Config->GCRoot)
AddSym(B);
while (!Worklist.empty()) {
SectionChunk *SC = Worklist.pop_back_val();
assert(SC->isLive() && "We mark as live when pushing onto the worklist!");
// Mark all symbols listed in the relocation table for this section.
for (Symbol *B : SC->symbols())
if (B)
AddSym(B);
// Mark associative sections if any.
for (SectionChunk *C : SC->children())
Enqueue(C);
}
}
template <typename PEHeaderTy> void Writer::writeHeader() {
// Write DOS stub
uint8_t *Buf = Buffer->getBufferStart();
auto *DOS = reinterpret_cast<dos_header *>(Buf);
Buf += DOSStubSize;
DOS->Magic[0] = 'M';
DOS->Magic[1] = 'Z';
DOS->AddressOfRelocationTable = sizeof(dos_header);
DOS->AddressOfNewExeHeader = DOSStubSize;
// Write PE magic
memcpy(Buf, PEMagic, sizeof(PEMagic));
Buf += sizeof(PEMagic);
// Write COFF header
auto *COFF = reinterpret_cast<coff_file_header *>(Buf);
Buf += sizeof(*COFF);
COFF->Machine = Config->Machine;
COFF->NumberOfSections = OutputSections.size();
COFF->Characteristics = IMAGE_FILE_EXECUTABLE_IMAGE;
if (Config->LargeAddressAware)
COFF->Characteristics |= IMAGE_FILE_LARGE_ADDRESS_AWARE;
if (!Config->is64())
COFF->Characteristics |= IMAGE_FILE_32BIT_MACHINE;
if (Config->DLL)
COFF->Characteristics |= IMAGE_FILE_DLL;
if (!Config->Relocatable)
COFF->Characteristics |= IMAGE_FILE_RELOCS_STRIPPED;
COFF->SizeOfOptionalHeader =
sizeof(PEHeaderTy) + sizeof(data_directory) * NumberfOfDataDirectory;
// Write PE header
auto *PE = reinterpret_cast<PEHeaderTy *>(Buf);
Buf += sizeof(*PE);
PE->Magic = Config->is64() ? PE32Header::PE32_PLUS : PE32Header::PE32;
PE->ImageBase = Config->ImageBase;
PE->SectionAlignment = PageSize;
PE->FileAlignment = SectorSize;
PE->MajorImageVersion = Config->MajorImageVersion;
PE->MinorImageVersion = Config->MinorImageVersion;
PE->MajorOperatingSystemVersion = Config->MajorOSVersion;
PE->MinorOperatingSystemVersion = Config->MinorOSVersion;
PE->MajorSubsystemVersion = Config->MajorOSVersion;
PE->MinorSubsystemVersion = Config->MinorOSVersion;
PE->Subsystem = Config->Subsystem;
PE->SizeOfImage = SizeOfImage;
PE->SizeOfHeaders = SizeOfHeaders;
if (!Config->NoEntry) {
Defined *Entry = cast<Defined>(Config->Entry->repl());
PE->AddressOfEntryPoint = Entry->getRVA();
// Pointer to thumb code must have the LSB set, so adjust it.
if (Config->Machine == ARMNT)
PE->AddressOfEntryPoint |= 1;
}
PE->SizeOfStackReserve = Config->StackReserve;
PE->SizeOfStackCommit = Config->StackCommit;
PE->SizeOfHeapReserve = Config->HeapReserve;
PE->SizeOfHeapCommit = Config->HeapCommit;
if (Config->DynamicBase)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE;
if (Config->HighEntropyVA)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA;
if (!Config->AllowBind)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_BIND;
if (Config->NxCompat)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NX_COMPAT;
if (!Config->AllowIsolation)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_ISOLATION;
if (Config->TerminalServerAware)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_TERMINAL_SERVER_AWARE;
PE->NumberOfRvaAndSize = NumberfOfDataDirectory;
if (OutputSection *Text = findSection(".text")) {
PE->BaseOfCode = Text->getRVA();
PE->SizeOfCode = Text->getRawSize();
}
PE->SizeOfInitializedData = getSizeOfInitializedData();
// Write data directory
auto *Dir = reinterpret_cast<data_directory *>(Buf);
Buf += sizeof(*Dir) * NumberfOfDataDirectory;
if (OutputSection *Sec = findSection(".edata")) {
Dir[EXPORT_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[EXPORT_TABLE].Size = Sec->getVirtualSize();
}
if (!Idata.empty()) {
Dir[IMPORT_TABLE].RelativeVirtualAddress = Idata.getDirRVA();
Dir[IMPORT_TABLE].Size = Idata.getDirSize();
Dir[IAT].RelativeVirtualAddress = Idata.getIATRVA();
Dir[IAT].Size = Idata.getIATSize();
}
if (!DelayIdata.empty()) {
Dir[DELAY_IMPORT_DESCRIPTOR].RelativeVirtualAddress =
DelayIdata.getDirRVA();
Dir[DELAY_IMPORT_DESCRIPTOR].Size = DelayIdata.getDirSize();
}
if (OutputSection *Sec = findSection(".rsrc")) {
Dir[RESOURCE_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[RESOURCE_TABLE].Size = Sec->getVirtualSize();
}
if (OutputSection *Sec = findSection(".reloc")) {
Dir[BASE_RELOCATION_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[BASE_RELOCATION_TABLE].Size = Sec->getVirtualSize();
}
if (OutputSection *Sec = findSection(".pdata")) {
Dir[EXCEPTION_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[EXCEPTION_TABLE].Size = Sec->getVirtualSize();
}
if (Symbol *Sym = Symtab->findUnderscore("_tls_used")) {
if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
Dir[TLS_TABLE].RelativeVirtualAddress = B->getRVA();
Dir[TLS_TABLE].Size = Config->is64()
? sizeof(object::coff_tls_directory64)
: sizeof(object::coff_tls_directory32);
}
}
if (Symbol *Sym = Symtab->findUnderscore("_load_config_used")) {
if (auto *B = dyn_cast<DefinedRegular>(Sym->Body)) {
SectionChunk *SC = B->getChunk();
assert(B->getRVA() >= SC->getRVA());
uint64_t OffsetInChunk = B->getRVA() - SC->getRVA();
if (!SC->hasData() || OffsetInChunk + 4 > SC->getSize())
fatal("_load_config_used is malformed");
ArrayRef<uint8_t> SecContents = SC->getContents();
uint32_t LoadConfigSize =
*reinterpret_cast<const ulittle32_t *>(&SecContents[OffsetInChunk]);
if (OffsetInChunk + LoadConfigSize > SC->getSize())
fatal("_load_config_used is too large");
Dir[LOAD_CONFIG_TABLE].RelativeVirtualAddress = B->getRVA();
Dir[LOAD_CONFIG_TABLE].Size = LoadConfigSize;
}
}
// Write section table
for (OutputSection *Sec : OutputSections) {
Sec->writeHeaderTo(Buf);
Buf += sizeof(coff_section);
}
if (OutputSymtab.empty())
return;
COFF->PointerToSymbolTable = PointerToSymbolTable;
uint32_t NumberOfSymbols = OutputSymtab.size();
COFF->NumberOfSymbols = NumberOfSymbols;
auto *SymbolTable = reinterpret_cast<coff_symbol16 *>(
Buffer->getBufferStart() + COFF->PointerToSymbolTable);
for (size_t I = 0; I != NumberOfSymbols; ++I)
SymbolTable[I] = OutputSymtab[I];
// Create the string table, it follows immediately after the symbol table.
// The first 4 bytes is length including itself.
Buf = reinterpret_cast<uint8_t *>(&SymbolTable[NumberOfSymbols]);
write32le(Buf, Strtab.size() + 4);
if (!Strtab.empty())
memcpy(Buf + 4, Strtab.data(), Strtab.size());
}
