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mold/main.cc

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#include "mold.h"
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#include <iostream>
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using namespace llvm;
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using namespace llvm::ELF;
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using llvm::object::Archive;
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using llvm::opt::InputArgList;
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Config config;
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//
// Command-line option processing
//
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enum {
OPT_INVALID = 0,
#define OPTION(_1, _2, ID, _4, _5, _6, _7, _8, _9, _10, _11, _12) OPT_##ID,
#include "options.inc"
#undef OPTION
};
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// Create prefix string literals used in Options.td
#define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
#include "options.inc"
#undef PREFIX
// Create table mapping all options defined in Options.td
static const llvm::opt::OptTable::Info opt_info[] = {
#define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12) \
{X1, X2, X10, X11, OPT_##ID, llvm::opt::Option::KIND##Class, \
X9, X8, OPT_##GROUP, OPT_##ALIAS, X7, X12},
#include "options.inc"
#undef OPTION
};
class MyOptTable : llvm::opt::OptTable {
public:
MyOptTable() : OptTable(opt_info) {}
InputArgList parse(int argc, char **argv);
};
InputArgList MyOptTable::parse(int argc, char **argv) {
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unsigned missing_index = 0;
unsigned missing_count = 0;
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SmallVector<const char *, 256> vec(argv, argv + argc);
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InputArgList args = this->ParseArgs(vec, missing_index, missing_count);
if (missing_count)
error(Twine(args.getArgString(missing_index)) + ": missing argument");
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for (auto *arg : args.filtered(OPT_UNKNOWN))
error("unknown argument '" + arg->getAsString(args) + "'");
return args;
}
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//
// Main
//
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static std::vector<MemoryBufferRef> get_archive_members(MemoryBufferRef mb) {
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std::unique_ptr<Archive> file =
CHECK(Archive::create(mb), mb.getBufferIdentifier() + ": failed to parse archive");
std::vector<MemoryBufferRef> vec;
Error err = Error::success();
for (const Archive::Child &c : file->children(err)) {
MemoryBufferRef mbref =
CHECK(c.getMemoryBufferRef(),
mb.getBufferIdentifier() +
": could not get the buffer for a child of the archive");
vec.push_back(mbref);
}
if (err)
error(mb.getBufferIdentifier() + ": Archive::children failed: " +
toString(std::move(err)));
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file.release(); // leak
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return vec;
}
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static void read_file(std::vector<ObjectFile *> &files, StringRef path) {
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MemoryBufferRef mb = readFile(path);
switch (identify_magic(mb.getBuffer())) {
case file_magic::archive:
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for (MemoryBufferRef member : get_archive_members(mb))
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files.push_back(new ObjectFile(member, path));
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break;
case file_magic::elf_relocatable:
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files.push_back(new ObjectFile(mb, ""));
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break;
default:
error(path + ": unknown file type");
}
}
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template <typename T>
static std::vector<ArrayRef<T>> split(const std::vector<T> &input, int unit) {
ArrayRef<T> arr(input);
std::vector<ArrayRef<T>> vec;
while (arr.size() >= unit) {
vec.push_back(arr.slice(0, unit));
arr = arr.slice(unit);
}
if (!arr.empty())
vec.push_back(arr);
return vec;
}
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static ObjectFile *create_internal_file() {
// Create a dummy object file.
static char buf[256];
std::unique_ptr<MemoryBuffer> mb =
MemoryBuffer::getMemBuffer(StringRef(buf, sizeof(buf)));
auto *obj = new ObjectFile(mb->getMemBufferRef(), "");
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obj->name = "<internal>";
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mb.release();
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// Create linker-synthesized symbols.
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auto *elf_syms = new std::vector<ELF64LE::Sym>;
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auto create = [&](StringRef name) {
Symbol *sym = Symbol::intern(name);
sym->file = obj;
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obj->symbols.push_back(sym);
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ELF64LE::Sym esym = {};
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esym.setType(STT_NOTYPE);
esym.setBinding(STB_GLOBAL);
elf_syms->push_back(esym);
return sym;
};
out::__bss_start = create("__bss_start");
out::__ehdr_start = create("__ehdr_start");
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out::__rela_iplt_start = create("__rela_iplt_start");
out::__rela_iplt_end = create("__rela_iplt_end");
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obj->elf_syms = *elf_syms;
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return obj;
}
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static void bin_sections(std::vector<ObjectFile *> &files) {
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#if 1
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int unit = (files.size() + 127) / 128;
std::vector<ArrayRef<ObjectFile *>> slices = split(files, unit);
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std::vector<std::vector<std::vector<InputSection *>>> groups(slices.size());
for (int i = 0; i < groups.size(); i++)
groups[i].resize(OutputSection::instances.size());
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tbb::parallel_for(0, (int)slices.size(), [&](int i) {
for (ObjectFile *file : slices[i]) {
for (InputSection *isec : file->sections) {
if (!isec)
continue;
OutputSection *osec = isec->output_section;
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groups[i][osec->idx].push_back(isec);
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}
}
});
std::vector<int> sizes(OutputSection::instances.size());
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for (ArrayRef<std::vector<InputSection *>> group : groups)
for (int i = 0; i < group.size(); i++)
sizes[i] += group[i].size();
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for (int i = 0; i < sizes.size(); i++)
OutputSection::instances[i]->sections.reserve(sizes[i]);
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for (ArrayRef<std::vector<InputSection *>> group : groups) {
for (int i = 0; i < group.size(); i++) {
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std::vector<InputSection *> &sections = OutputSection::instances[i]->sections;
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sections.insert(sections.end(), group[i].begin(), group[i].end());
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}
}
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#else
for (ObjectFile *file : files) {
for (InputSection *isec : file->sections) {
if (!isec)
continue;
OutputSection *osec = isec->output_section;
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osec->sections.push_back(isec);
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}
}
#endif
}
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static void set_isec_offsets() {
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#if 1
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for_each(OutputSection::instances, [&](OutputSection *osec) {
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if (osec->sections.empty())
return;
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std::vector<ArrayRef<InputSection *>> slices = split(osec->sections, 100000);
std::vector<u64> size(slices.size());
std::vector<u32> alignments(slices.size());
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tbb::parallel_for(0, (int)slices.size(), [&](int i) {
u64 off = 0;
u32 align = 1;
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for (InputSection *isec : slices[i]) {
off = align_to(off, isec->shdr.sh_addralign);
isec->offset = off;
off += isec->shdr.sh_size;
align = std::max<u32>(align, isec->shdr.sh_addralign);
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}
size[i] = off;
alignments[i] = align;
});
u32 align = *std::max_element(alignments.begin(), alignments.end());
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std::vector<u64> start(slices.size());
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for (int i = 1; i < slices.size(); i++)
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start[i] = align_to(start[i - 1] + size[i], align);
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tbb::parallel_for(1, (int)slices.size(), [&](int i) {
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for (InputSection *isec : slices[i])
isec->offset += start[i];
});
osec->shdr.sh_size = start.back() + size.back();
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osec->shdr.sh_addralign = align;
});
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#else
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for_each(OutputSection::instances, [&](OutputSection *osec) {
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if (osec->sections.empty())
return;
u64 off = 0;
u32 align = 0;
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for (InputSection *isec : osec->sections) {
off = align_to(off, isec->shdr.sh_addralign);
isec->offset = off;
off += isec->shdr.sh_size;
align = std::max<u32>(align, isec->shdr.sh_addralign);
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}
osec->shdr.sh_size = off;
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osec->shdr.sh_addralign = align;
});
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#endif
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}
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// We want to sort output sections in the following order.
//
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// alloc readonly data
// alloc readonly code
// alloc writable tdata
// alloc writable tbss
// alloc writable data
// alloc writable bss
// nonalloc
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static int get_rank(const ELF64LE::Shdr shdr) {
bool alloc = shdr.sh_flags & SHF_ALLOC;
bool writable = shdr.sh_flags & SHF_WRITE;
bool exec = shdr.sh_flags & SHF_EXECINSTR;
bool tls = shdr.sh_flags & SHF_TLS;
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bool nobits = shdr.sh_type == SHT_NOBITS;
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return (alloc << 5) | (!writable << 4) | (!exec << 3) | (tls << 2) | !nobits;
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}
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static void sort_output_chunks(std::vector<OutputChunk *> &chunks) {
std::sort(chunks.begin(), chunks.end(), [](OutputChunk *a, OutputChunk *b) {
int x = get_rank(a->shdr);
int y = get_rank(b->shdr);
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if (x != y)
return x > y;
// Tie-break to make output deterministic.
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if (a->shdr.sh_flags != b->shdr.sh_flags)
return a->shdr.sh_flags < b->shdr.sh_flags;
if (a->shdr.sh_type != b->shdr.sh_type)
return a->shdr.sh_type < b->shdr.sh_type;
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return a->name < b->name;
});
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}
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static std::vector<ELF64LE::Shdr *>
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create_shdrs(ArrayRef<OutputChunk *> output_chunks) {
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static ELF64LE::Shdr null_entry = {};
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std::vector<ELF64LE::Shdr *> vec;
vec.push_back(&null_entry);
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int shndx = 1;
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for (OutputChunk *chunk : output_chunks) {
if (!chunk->name.empty()) {
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vec.push_back(&chunk->shdr);
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chunk->shndx = shndx++;
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}
}
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return vec;
}
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static void fill_shdrs(ArrayRef<OutputChunk *> output_chunks) {
int i = 1;
for (OutputChunk *chunk : output_chunks) {
if (chunk->name.empty())
continue;
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chunk->shdr.sh_size = chunk->get_size();
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}
}
static u64 set_osec_offsets(ArrayRef<OutputChunk *> output_chunks) {
u64 fileoff = 0;
u64 vaddr = 0x200000;
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for (OutputChunk *chunk : output_chunks) {
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if (chunk->starts_new_ptload)
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vaddr = align_to(vaddr, PAGE_SIZE);
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if (!chunk->is_bss()) {
if (vaddr % PAGE_SIZE > fileoff % PAGE_SIZE)
fileoff += vaddr % PAGE_SIZE - fileoff % PAGE_SIZE;
else if (vaddr % PAGE_SIZE < fileoff % PAGE_SIZE)
fileoff = align_to(fileoff, PAGE_SIZE) + vaddr % PAGE_SIZE;
}
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fileoff = align_to(fileoff, chunk->shdr.sh_addralign);
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vaddr = align_to(vaddr, chunk->shdr.sh_addralign);
chunk->shdr.sh_offset = fileoff;
if (chunk->shdr.sh_flags & SHF_ALLOC)
chunk->shdr.sh_addr = vaddr;
if (!chunk->is_bss())
fileoff += chunk->get_size();
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#if 1
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bool is_tbss = chunk->is_bss() && (chunk->shdr.sh_flags & SHF_TLS);
if (!is_tbss)
vaddr += chunk->get_size();
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#else
vaddr += chunk->get_size();
#endif
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}
return fileoff;
}
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static void unlink_async(tbb::task_group &tg, StringRef path) {
if (!sys::fs::exists(path) || !sys::fs::is_regular_file(path))
return;
int fd;
if (std::error_code ec = sys::fs::openFileForRead(path, fd))
return;
sys::fs::remove(path);
tg.run([=]() { close(fd); });
}
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static void write_symtab(u8 *buf, std::vector<ObjectFile *> files) {
std::vector<u64> symtab_off(files.size() + 1);
std::vector<u64> strtab_off(files.size() + 1);
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strtab_off[0] = 1;
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for (int i = 1; i < files.size() + 1; i++) {
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symtab_off[i] = symtab_off[i - 1] + files[i - 1]->local_symtab_size;
strtab_off[i] = strtab_off[i - 1] + files[i - 1]->local_strtab_size;
}
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out::symtab->shdr.sh_info = symtab_off.back() / sizeof(ELF64LE::Sym);
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tbb::parallel_for((size_t)0, files.size(),
[&](size_t i) {
files[i]->write_local_symtab(buf, symtab_off[i], strtab_off[i]);
});
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symtab_off[0] = symtab_off.back();
strtab_off[0] = strtab_off.back();
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for (int i = 1; i < files.size() + 1; i++) {
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symtab_off[i] = symtab_off[i - 1] + files[i - 1]->global_symtab_size;
strtab_off[i] = strtab_off[i - 1] + files[i - 1]->global_strtab_size;
}
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assert(symtab_off.back() == out::symtab->size);
assert(strtab_off.back() == out::strtab->size);
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tbb::parallel_for((size_t)0, files.size(),
[&](size_t i) {
files[i]->write_global_symtab(buf, symtab_off[i], strtab_off[i]);
});
}
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class MyTimer {
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public:
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MyTimer(StringRef name) {
timer = new Timer(name, name);
timer->startTimer();
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}
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MyTimer(StringRef name, llvm::TimerGroup &tg) {
timer = new Timer(name, name, tg);
timer->startTimer();
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}
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~MyTimer() { timer->stopTimer(); }
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private:
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llvm::Timer *timer;
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};
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static int get_thread_count(InputArgList &args) {
if (auto *arg = args.getLastArg(OPT_thread_count)) {
int n;
if (!llvm::to_integer(arg->getValue(), n) || n <= 0)
error(arg->getSpelling() + ": expected a positive integer, but got '" +
arg->getValue() + "'");
return n;
}
return tbb::global_control::active_value(tbb::global_control::max_allowed_parallelism);
}
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int main(int argc, char **argv) {
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// Parse command line options
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MyOptTable opt_table;
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InputArgList args = opt_table.parse(argc - 1, argv + 1);
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tbb::global_control tbb_cont(tbb::global_control::max_allowed_parallelism,
get_thread_count(args));
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if (auto *arg = args.getLastArg(OPT_o))
config.output = arg->getValue();
else
error("-o option is missing");
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config.print_map = args.hasArg(OPT_print_map);
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std::vector<ObjectFile *> files;
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llvm::TimerGroup before_copy("before_copy", "before_copy");
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// Open input files
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{
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MyTimer t("parse");
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for (auto *arg : args)
if (arg->getOption().getID() == OPT_INPUT)
read_file(files, arg->getValue());
// Parse input files
for_each(files, [](ObjectFile *file) { file->parse(); });
}
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// Set priorities to files
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int priority = 1;
for (ObjectFile *file : files)
if (!file->is_in_archive())
file->priority = priority++;
for (ObjectFile *file : files)
if (file->is_in_archive())
file->priority = priority++;
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// Resolve symbols
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{
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MyTimer t("resolve_symbols", before_copy);
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for_each(files, [](ObjectFile *file) { file->register_defined_symbols(); });
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// Add defined symbols
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std::vector<ObjectFile *> objs;
for (ObjectFile *file : files)
if (!file->is_in_archive())
objs.push_back(file);
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// Add undefined symbols
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tbb::parallel_do(
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objs.begin(), objs.end(),
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[&](ObjectFile *file, tbb::parallel_do_feeder<ObjectFile *>& feeder) {
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file->register_undefined_symbols(feeder);
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});
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// Eliminate unused archive members.
files.erase(std::remove_if(files.begin(), files.end(),
[](ObjectFile *file){ return !file->is_alive; }),
files.end());
// Convert weak symbols to absolute symbols with value 0.
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for_each(files, [](ObjectFile *file) { file->hanlde_undefined_weak_symbols(); });
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}
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files.push_back(create_internal_file());
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// Eliminate duplicate comdat groups.
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{
MyTimer t("comdat", before_copy);
for_each(files, [](ObjectFile *file) { file->eliminate_duplicate_comdat_groups(); });
}
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// Create .bss sections for common symbols.
{
MyTimer t("common", before_copy);
for_each(files, [](ObjectFile *file) { file->convert_common_symbols(); });
}
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// Bin input sections into output sections
{
MyTimer t("bin_sections", before_copy);
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bin_sections(files);
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}
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// Assign offsets within an output section to input sections.
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{
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MyTimer t("isec_offsets", before_copy);
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set_isec_offsets();
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}
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// Create linker-synthesized sections.
out::ehdr = new OutputEhdr;
out::phdr = new OutputPhdr;
out::shdr = new OutputShdr;
// out::interp = new InterpSection;
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out::got = new GotSection(".got");
out::gotplt = new GotSection(".got.plt");
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out::plt = new PltSection;
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out::relplt = new RelPltSection;
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out::shstrtab = new ShstrtabSection;
out::symtab = new SymtabSection;
out::strtab = new StrtabSection;
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// Scan relocations to fix the sizes of .got, .plt, .got.plt, .dynstr,
// .rela.dyn, .rela.plt.
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{
MyTimer t("scan_rel", before_copy);
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std::atomic_int32_t num_got = 0;
std::atomic_int32_t num_gotplt = 0;
std::atomic_int32_t num_plt = 0;
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std::atomic_int32_t num_relplt = 0;
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for_each(files, [&](ObjectFile *file) {
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for (InputSection *isec : file->sections)
if (isec)
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isec->scan_relocations();
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num_got += file->num_got;
num_gotplt += file->num_gotplt;
num_plt += file->num_plt;
num_relplt += file->num_relplt;
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});
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out::got->size = num_got * 8;
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out::gotplt->size = num_gotplt * 8;
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out::plt->size = num_plt * 16;
out::relplt->size = num_relplt * sizeof(ELF64LE::Rela);
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}
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// Compute .symtab and .strtab sizes
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{
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MyTimer t("symtab_size", before_copy);
for_each(files, [](ObjectFile *file) { file->compute_symtab(); });
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for (ObjectFile *file : files) {
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out::symtab->size += file->local_symtab_size + file->global_symtab_size;
out::strtab->size += file->local_strtab_size + file->global_strtab_size;
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}
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}
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// Assign symbols to GOT offsets
{
MyTimer t("got");
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u32 got_offset = 0;
u32 gotplt_offset = 0;
u32 plt_offset = 0;
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out::got->symbols.reserve(out::got->size / 8);
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out::gotplt->symbols.reserve(out::gotplt->size / 8);
out::plt->symbols.reserve(out::plt->size / 16);
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for (ObjectFile *file : files) {
for (Symbol *sym : file->symbols) {
// _nl_current_LC_ADDRESS
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if (sym->file != file)
continue;
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if (sym->got_offset == -1) {
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out::got->symbols.push_back({GotSection::REGULAR, sym});
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sym->got_offset = got_offset;
got_offset += 8;
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}
if (sym->gottp_offset == -1) {
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out::got->symbols.push_back({GotSection::TPOFF, sym});
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sym->gottp_offset = got_offset;
got_offset += 8;
}
if (sym->gotplt_offset == -1) {
assert(sym->type == STT_GNU_IFUNC);
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out::gotplt->symbols.push_back({GotSection::IREL, sym});
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sym->gotplt_offset = gotplt_offset;
gotplt_offset += 8;
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}
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if (sym->plt_offset == -1) {
out::plt->symbols.push_back(sym);
sym->plt_offset = plt_offset;
plt_offset += 16;
}
}
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}
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llvm::outs().flush();
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assert(got_offset == out::got->size);
assert(gotplt_offset == out::gotplt->size);
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assert(plt_offset == out::plt->size);
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}
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// Add output sections.
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std::vector<OutputChunk *> output_chunks;
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for (OutputSection *osec : OutputSection::instances)
if (!osec->empty())
output_chunks.push_back(osec);
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if (out::got->size)
output_chunks.push_back(out::got);
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if (out::plt->size)
output_chunks.push_back(out::plt);
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if (out::gotplt->size)
output_chunks.push_back(out::gotplt);
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if (out::relplt->size)
output_chunks.push_back(out::relplt);
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sort_output_chunks(output_chunks);
// Add ELF header, program header and .interp to the output.
output_chunks.insert(output_chunks.begin(), out::ehdr);
output_chunks.insert(output_chunks.begin() + 1, out::phdr);
// output_chunks.insert(output_chunks.begin() + 2, out::interp);
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// Add a string table for section names.
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output_chunks.push_back(out::shstrtab);
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// Add a section header.
output_chunks.push_back(out::shdr);
// Add .symtab and .strtab.
output_chunks.push_back(out::symtab);
output_chunks.push_back(out::strtab);
// Fix .shstrtab contents.
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for (OutputChunk *chunk : output_chunks)
if (!chunk->name.empty())
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chunk->shdr.sh_name = out::shstrtab->add_string(chunk->name);
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// Create section header and program header contents.
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out::shdr->entries = create_shdrs(output_chunks);
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out::phdr->construct(output_chunks);
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out::symtab->shdr.sh_link = out::strtab->shndx;
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// Fill section header.
fill_shdrs(output_chunks);
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// Assign offsets to output sections
u64 filesize = 0;
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{
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MyTimer t("osec_offset", before_copy);
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filesize = set_osec_offsets(output_chunks);
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}
2020-10-19 17:37:29 +03:00
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// Attach linker-synthesized symbols to sections.
{
// __bss_start
for (OutputChunk *chunk : output_chunks) {
if (chunk->name == ".bss" && !chunk->sections.empty()) {
out::__bss_start->input_section = chunk->sections[0];
break;
}
}
// __ehdr_start
for (OutputChunk *chunk : output_chunks) {
if (chunk->shndx == 1) {
out::__ehdr_start->input_section = chunk->sections[0];
out::__ehdr_start->addr = out::ehdr->shdr.sh_addr - chunk->shdr.sh_addr;
break;
}
}
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// __rela_iplt_start and __rela_iplt_end
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out::__rela_iplt_start->addr = out::relplt->shdr.sh_addr;
out::__rela_iplt_end->addr = out::relplt->shdr.sh_addr + out::relplt->shdr.sh_size;
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}
// Fix symbol addresses.
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{
MyTimer t("sym_addr");
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for_each(files, [](ObjectFile *file) { file->fix_sym_addrs(); });
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for (OutputChunk *chunk : output_chunks)
if (chunk->shdr.sh_flags & SHF_TLS)
out::tls_end = chunk->shdr.sh_addr + chunk->shdr.sh_size;
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}
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tbb::task_group unlink_tg;
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{
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MyTimer t("unlink");
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unlink_async(unlink_tg, config.output);
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}
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// Create an output file
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std::unique_ptr<FileOutputBuffer> output_buffer;
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{
MyTimer t("open");
Expected<std::unique_ptr<FileOutputBuffer>> buf_or_err =
FileOutputBuffer::create(config.output, filesize, FileOutputBuffer::F_executable);
if (!buf_or_err)
error("failed to open " + config.output + ": " +
llvm::toString(buf_or_err.takeError()));
output_buffer = std::move(*buf_or_err);
}
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u8 *buf = output_buffer->getBufferStart();
2020-10-20 03:20:52 +03:00
2020-10-27 15:38:52 +03:00
// Fill .symtab and .strtab
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tbb::task_group tg_symtab;
tg_symtab.run([&]() {
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MyTimer t("write_symtab");
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write_symtab(buf, files);
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});
2020-10-27 15:38:52 +03:00
2020-10-20 03:20:52 +03:00
// Copy input sections to the output file
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{
MyTimer t("copy");
for_each(output_chunks, [&](OutputChunk *chunk) { chunk->copy_to(buf); });
}
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{
MyTimer t("reloc");
for_each(output_chunks, [&](OutputChunk *chunk) { chunk->relocate(buf); });
}
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{
MyTimer t("symtab_wait");
tg_symtab.wait();
}
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out::shdr->copy_to(buf);
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{
MyTimer t("commit");
if (auto e = output_buffer->commit())
error("failed to write to the output file: " + toString(std::move(e)));
}
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int num_input_chunks = 0;
for (ObjectFile *file : files)
num_input_chunks += file->sections.size();
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{
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MyTimer t("unlink_wait");
unlink_tg.wait();
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}
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if (config.print_map) {
MyTimer t("print_map");
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print_map(files, output_chunks);
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}
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#if 0
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for (ObjectFile *file : files)
for (InputSection *isec : file->sections)
if (isec)
llvm::outs() << toString(isec) << "\n";
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#endif
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#if 1
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llvm::outs() << " input_chunks=" << num_input_chunks << "\n"
<< "output_chunks=" << output_chunks.size() << "\n"
<< " files=" << files.size() << "\n"
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<< " filesize=" << filesize << "\n"
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<< " num_all_syms=" << num_all_syms << "\n"
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<< " num_defined=" << num_defined << "\n"
<< "num_undefined=" << num_undefined << "\n"
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<< " num_comdats=" << num_comdats << "\n"
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<< "num_regular_sections=" << num_regular_sections << "\n"
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<< " num_relocs=" << num_relocs << "\n"
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<< "num_relocs_alloc=" << num_relocs_alloc << "\n"
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<< " num_str=" << num_string_pieces << "\n";
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llvm::TimerGroup::printAll(llvm::outs());
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#endif
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llvm::outs().flush();
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_exit(0);
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}