void GarbageCollection::stripSections()
{
// Traverse all the input Regular and BSS sections, if a section is not found
// in the ReferencedSections, then it should be garbage collected
Module::obj_iterator obj, objEnd = m_Module.obj_end();
for (obj = m_Module.obj_begin(); obj != objEnd; ++obj) {
LDContext::sect_iterator sect, sectEnd = (*obj)->context()->sectEnd();
for (sect = (*obj)->context()->sectBegin(); sect != sectEnd; ++sect) {
LDSection* section = *sect;
if (LDFileFormat::Regular != section->kind() &&
LDFileFormat::BSS != section->kind())
continue;
if (m_ReferencedSections.find(section) == m_ReferencedSections.end())
section->setKind(LDFileFormat::Ignore);
}
}
// Traverse all the relocation sections, if its target section is set to
// Ignore, then set the relocation section to Ignore as well
Module::obj_iterator input, inEnd = m_Module.obj_end();
for (input = m_Module.obj_begin(); input != inEnd; ++input) {
LDContext::sect_iterator rs, rsEnd = (*input)->context()->relocSectEnd();
for (rs = (*input)->context()->relocSectBegin(); rs != rsEnd; ++rs) {
LDSection* reloc_sect = *rs;
if (LDFileFormat::Ignore == reloc_sect->getLink()->kind())
reloc_sect->setKind(LDFileFormat::Ignore);
}
}
}
bool ARMGNULDBackend::mergeSection(Module& pModule,
const Input& pInput,
LDSection& pSection)
{
switch (pSection.type()) {
case llvm::ELF::SHT_ARM_ATTRIBUTES: {
return attribute().merge(pInput, pSection);
}
case llvm::ELF::SHT_ARM_EXIDX: {
assert(NULL != pSection.getLink());
if ((pSection.getLink()->kind() == LDFileFormat::Ignore) ||
(pSection.getLink()->kind() == LDFileFormat::Folded)) {
// if the target section of the .ARM.exidx is Ignore, then it should be
// ignored as well
pSection.setKind(LDFileFormat::Ignore);
return true;
}
}
/** fall through **/
default: {
ObjectBuilder builder(pModule);
builder.MergeSection(pInput, pSection);
return true;
}
} // end of switch
return true;
}
void IdenticalCodeFolding::foldIdenticalCode() {
// 1. Find folding candidates.
FoldingCandidates candidate_list;
findCandidates(candidate_list);
// 2. Initialize constant section content
for (size_t i = 0; i < candidate_list.size(); ++i) {
candidate_list[i].initConstantContent(m_Backend, m_KeptSections);
}
// 3. Find identical code until convergence
bool converged = false;
size_t iterations = 0;
while (!converged && (iterations < m_Config.options().getICFIterations())) {
converged = matchCandidates(candidate_list);
++iterations;
}
if (m_Config.options().printICFSections()) {
debug(diag::debug_icf_iterations) << iterations;
}
// 4. Fold the identical code
typedef std::set<Input*> FoldedObjects;
FoldedObjects folded_objs;
KeptSections::iterator kept, keptEnd = m_KeptSections.end();
size_t index = 0;
for (kept = m_KeptSections.begin(); kept != keptEnd; ++kept, ++index) {
LDSection* sect = (*kept).first;
Input* obj = (*kept).second.first;
size_t kept_index = (*kept).second.second;
if (index != kept_index) {
sect->setKind(LDFileFormat::Folded);
folded_objs.insert(obj);
if (m_Config.options().printICFSections()) {
KeptSections::iterator it = m_KeptSections.begin() + kept_index;
LDSection* kept_sect = (*it).first;
Input* kept_obj = (*it).second.first;
debug(diag::debug_icf_folded_section) << sect->name() << obj->name()
<< kept_sect->name()
<< kept_obj->name();
}
}
}
// Adjust the fragment reference of the folded symbols.
FoldedObjects::iterator fobj, fobjEnd = folded_objs.end();
for (fobj = folded_objs.begin(); fobj != fobjEnd; ++fobj) {
LDContext::sym_iterator sym, symEnd = (*fobj)->context()->symTabEnd();
for (sym = (*fobj)->context()->symTabBegin(); sym != symEnd; ++sym) {
if ((*sym)->hasFragRef() && ((*sym)->type() == ResolveInfo::Function)) {
LDSymbol* out_sym = (*sym)->resolveInfo()->outSymbol();
FragmentRef* frag_ref = out_sym->fragRef();
LDSection* sect = &(frag_ref->frag()->getParent()->getSection());
if (sect->kind() == LDFileFormat::Folded) {
size_t kept_index = m_KeptSections[sect].second;
LDSection* kept_sect = (*(m_KeptSections.begin() + kept_index)).first;
frag_ref->assign(kept_sect->getSectionData()->front(),
frag_ref->offset());
}
}
} // for each symbol
} // for each folded object
}
