maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[ELF] Replace InputBaseSection::{areRelocsRela,firstRelocation,numRelocation} with relSecIdx 

For `InputSection` `.foo`, its `InputBaseSection::{areRelocsRela,firstRelocation,numRelocation}` basically
encode the information of `.rel[a].foo`. However, one uint32_t (the relocation section index)
suffices. See the implementation of `relsOrRelas`.

This change decreases sizeof(InputSection) from 184 to 176 on 64-bit Linux.

The maximum resident set size linking a large application (1.2G output) decreases by 0.39%.

Differential Revision: https://reviews.llvm.org/D112513
This commit is contained in:
Fangrui Song 2021-10-27 09:51:06 -07:00
parent 156f10c840
commit ecc93ed2d7
11 changed files with 107 additions and 96 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
lld/ELF/Arch/PPC64.cpp
View File

@ -279,9 +279,6 @@ void elf::addPPC64SaveRestore() {
template <typename ELFT>
static std::pair<Defined *, int64_t>
getRelaTocSymAndAddend(InputSectionBase *tocSec, uint64_t offset) {
if (tocSec->numRelocations == 0)
return {};
// .rela.toc contains exclusively R_PPC64_ADDR64 relocations sorted by
// r_offset: 0, 8, 16, etc. For a given Offset, Offset / 8 gives us the
// relocation index in most cases.
@ -291,7 +288,10 @@ getRelaTocSymAndAddend(InputSectionBase *tocSec, uint64_t offset) {
// points to a relocation with larger r_offset. Do a linear probe then.
// Constants are extremely uncommon in .toc and the extra number of array
// accesses can be seen as a small constant.
ArrayRef<typename ELFT::Rela> relas = tocSec->template relas<ELFT>();
ArrayRef<typename ELFT::Rela> relas =
tocSec->template relsOrRelas<ELFT>().relas;
if (relas.empty())
return {};
uint64_t index = std::min<uint64_t>(offset / 8, relas.size() - 1);
for (;;) {
if (relas[index].r_offset == offset) {

7
lld/ELF/DWARF.cpp
View File

@ -137,9 +137,10 @@ template <class ELFT>
Optional<RelocAddrEntry> LLDDwarfObj<ELFT>::find(const llvm::DWARFSection &s,
uint64_t pos) const {
auto &sec = static_cast<const LLDDWARFSection &>(s);
if (sec.sec->areRelocsRela)
return findAux(*sec.sec, pos, sec.sec->template relas<ELFT>());
return findAux(*sec.sec, pos, sec.sec->template rels<ELFT>());
const RelsOrRelas<ELFT> rels = sec.sec->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
return findAux(*sec.sec, pos, rels.rels);
return findAux(*sec.sec, pos, rels.relas);
}
template class elf::LLDDwarfObj<ELF32LE>;

7
lld/ELF/Driver.cpp
View File

@ -1913,10 +1913,11 @@ template <typename ELFT>
static void readSymbolPartitionSection(InputSectionBase *s) {
// Read the relocation that refers to the partition's entry point symbol.
Symbol *sym;
if (s->areRelocsRela)
sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template relas<ELFT>()[0]);
const RelsOrRelas<ELFT> rels = s->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
sym = &s->getFile<ELFT>()->getRelocTargetSym(rels.rels[0]);
else
sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template rels<ELFT>()[0]);
sym = &s->getFile<ELFT>()->getRelocTargetSym(rels.relas[0]);
if (!isa<Defined>(sym) || !sym->includeInDynsym())
return;

29
lld/ELF/ICF.cpp
View File

@ -239,6 +239,8 @@ template <class ELFT>
template <class RelTy>
bool ICF<ELFT>::constantEq(const InputSection *secA, ArrayRef<RelTy> ra,
const InputSection *secB, ArrayRef<RelTy> rb) {
if (ra.size() != rb.size())
return false;
for (size_t i = 0; i < ra.size(); ++i) {
if (ra[i].r_offset != rb[i].r_offset ||
ra[i].getType(config->isMips64EL) != rb[i].getType(config->isMips64EL))
@ -312,8 +314,8 @@ bool ICF<ELFT>::constantEq(const InputSection *secA, ArrayRef<RelTy> ra,
// except relocation targets.
template <class ELFT>
bool ICF<ELFT>::equalsConstant(const InputSection *a, const InputSection *b) {
if (a->numRelocations != b->numRelocations || a->flags != b->flags ||
a->getSize() != b->getSize() || a->data() != b->data())
if (a->flags != b->flags || a->getSize() != b->getSize() ||
a->data() != b->data())
return false;
// If two sections have different output sections, we cannot merge them.
@ -321,10 +323,10 @@ bool ICF<ELFT>::equalsConstant(const InputSection *a, const InputSection *b) {
if (a->getParent() != b->getParent())
return false;
if (a->areRelocsRela)
return constantEq(a, a->template relas<ELFT>(), b,
b->template relas<ELFT>());
return constantEq(a, a->template rels<ELFT>(), b, b->template rels<ELFT>());
const RelsOrRelas<ELFT> ra = a->template relsOrRelas<ELFT>();
const RelsOrRelas<ELFT> rb = b->template relsOrRelas<ELFT>();
return ra.areRelocsRel() ? constantEq(a, ra.rels, b, rb.rels)
: constantEq(a, ra.relas, b, rb.relas);
}
// Compare two lists of relocations. Returns true if all pairs of
@ -369,10 +371,10 @@ bool ICF<ELFT>::variableEq(const InputSection *secA, ArrayRef<RelTy> ra,
// Compare "moving" part of two InputSections, namely relocation targets.
template <class ELFT>
bool ICF<ELFT>::equalsVariable(const InputSection *a, const InputSection *b) {
if (a->areRelocsRela)
return variableEq(a, a->template relas<ELFT>(), b,
b->template relas<ELFT>());
return variableEq(a, a->template rels<ELFT>(), b, b->template rels<ELFT>());
const RelsOrRelas<ELFT> ra = a->template relsOrRelas<ELFT>();
const RelsOrRelas<ELFT> rb = b->template relsOrRelas<ELFT>();
return ra.areRelocsRel() ? variableEq(a, ra.rels, b, rb.rels)
: variableEq(a, ra.relas, b, rb.relas);
}
template <class ELFT> size_t ICF<ELFT>::findBoundary(size_t begin, size_t end) {
@ -499,10 +501,11 @@ template <class ELFT> void ICF<ELFT>::run() {
// a large time complexity will have less work to do.
for (unsigned cnt = 0; cnt != 2; ++cnt) {
parallelForEach(sections, [&](InputSection *s) {
if (s->areRelocsRela)
combineRelocHashes<ELFT>(cnt, s, s->template relas<ELFT>());
const RelsOrRelas<ELFT> rels = s->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
combineRelocHashes<ELFT>(cnt, s, rels.rels);
else
combineRelocHashes<ELFT>(cnt, s, s->template rels<ELFT>());
combineRelocHashes<ELFT>(cnt, s, rels.relas);
});
}

25
lld/ELF/InputFiles.cpp
View File

@ -612,7 +612,7 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
.second;
if (keepGroup) {
if (config->relocatable)
this->sections[i] = createInputSection(sec, shstrtab);
this->sections[i] = createInputSection(i, sec, shstrtab);
selectedGroups.push_back(entries);
continue;
}
@ -636,7 +636,7 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
case SHT_NULL:
break;
default:
this->sections[i] = createInputSection(sec, shstrtab);
this->sections[i] = createInputSection(i, sec, shstrtab);
}
}
@ -653,7 +653,7 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
const Elf_Shdr &sec = objSections[i];
if (sec.sh_type == SHT_REL || sec.sh_type == SHT_RELA)
this->sections[i] = createInputSection(sec, shstrtab);
this->sections[i] = createInputSection(i, sec, shstrtab);
// A SHF_LINK_ORDER section with sh_link=0 is handled as if it did not have
// the flag.
@ -862,7 +862,8 @@ static InputSection *toRegularSection(MergeInputSection *sec) {
}
template <class ELFT>
InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec,
InputSectionBase *ObjFile<ELFT>::createInputSection(uint32_t idx,
const Elf_Shdr &sec,
StringRef shstrtab) {
StringRef name = CHECK(getObj().getSectionName(sec, shstrtab), this);
@ -952,22 +953,10 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec,
this->sections[sec.sh_info] = target;
}
if (target->firstRelocation)
if (target->relSecIdx != 0)
fatal(toString(this) +
": multiple relocation sections to one section are not supported");
if (sec.sh_type == SHT_RELA) {
ArrayRef<Elf_Rela> rels = CHECK(getObj().relas(sec), this);
target->firstRelocation = rels.begin();
target->numRelocations = rels.size();
target->areRelocsRela = true;
} else {
ArrayRef<Elf_Rel> rels = CHECK(getObj().rels(sec), this);
target->firstRelocation = rels.begin();
target->numRelocations = rels.size();
target->areRelocsRela = false;
}
assert(isUInt<31>(target->numRelocations));
target->relSecIdx = idx;
// Relocation sections are usually removed from the output, so return
// `nullptr` for the normal case. However, if -r or --emit-relocs is

3
lld/ELF/InputFiles.h
View File

@ -260,7 +260,8 @@ private:
void initializeJustSymbols();
InputSectionBase *getRelocTarget(const Elf_Shdr &sec);
InputSectionBase *createInputSection(const Elf_Shdr &sec, StringRef shstrtab);
InputSectionBase *createInputSection(uint32_t idx, const Elf_Shdr &sec,
StringRef shstrtab);
bool shouldMerge(const Elf_Shdr &sec, StringRef name);

47
lld/ELF/InputSection.cpp
View File

@ -70,9 +70,6 @@ InputSectionBase::InputSectionBase(InputFile *file, uint64_t flags,
if (sectionKind == SectionBase::Merge && rawData.size() > UINT32_MAX)
error(toString(this) + ": section too large");
numRelocations = 0;
areRelocsRela = false;
// The ELF spec states that a value of 0 means the section has
// no alignment constraints.
uint32_t v = std::max<uint32_t>(alignment, 1);
@ -162,6 +159,25 @@ uint64_t InputSectionBase::getOffsetInFile() const {
return secStart - fileStart;
}
template <class ELFT> RelsOrRelas<ELFT> InputSectionBase::relsOrRelas() const {
if (relSecIdx == 0)
return {};
RelsOrRelas<ELFT> ret;
const ELFFile<ELFT> obj = cast<ELFFileBase>(file)->getObj<ELFT>();
typename ELFT::Shdr shdr = cantFail(obj.sections())[relSecIdx];
if (shdr.sh_type == SHT_REL) {
ret.rels = makeArrayRef(reinterpret_cast<const typename ELFT::Rel *>(
obj.base() + shdr.sh_offset),
shdr.sh_size / sizeof(typename ELFT::Rel));
} else {
assert(shdr.sh_type == SHT_RELA);
ret.relas = makeArrayRef(reinterpret_cast<const typename ELFT::Rela *>(
obj.base() + shdr.sh_offset),
shdr.sh_size / sizeof(typename ELFT::Rela));
}
return ret;
}
uint64_t SectionBase::getOffset(uint64_t offset) const {
switch (kind()) {
case Output: {
@ -993,12 +1009,15 @@ void InputSectionBase::relocate(uint8_t *buf, uint8_t *bufEnd) {
}
auto *sec = cast<InputSection>(this);
if (config->relocatable)
if (config->relocatable) {
relocateNonAllocForRelocatable(sec, buf);
else if (sec->areRelocsRela)
sec->relocateNonAlloc<ELFT>(buf, sec->template relas<ELFT>());
else
sec->relocateNonAlloc<ELFT>(buf, sec->template rels<ELFT>());
} else {
const RelsOrRelas<ELFT> rels = sec->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
sec->relocateNonAlloc<ELFT>(buf, rels.rels);
else
sec->relocateNonAlloc<ELFT>(buf, rels.relas);
}
}
void InputSectionBase::relocateAlloc(uint8_t *buf, uint8_t *bufEnd) {
@ -1312,10 +1331,11 @@ static unsigned getReloc(IntTy begin, IntTy size, const ArrayRef<RelTy> &rels,
// .eh_frame is a sequence of CIE or FDE records.
// This function splits an input section into records and returns them.
template <class ELFT> void EhInputSection::split() {
if (areRelocsRela)
split<ELFT>(relas<ELFT>());
const RelsOrRelas<ELFT> rels = relsOrRelas<ELFT>();
if (rels.areRelocsRel())
split<ELFT>(rels.rels);
else
split<ELFT>(rels<ELFT>());
split<ELFT>(rels.relas);
}
template <class ELFT, class RelTy>
@ -1452,6 +1472,11 @@ template void InputSection::writeTo<ELF32BE>(uint8_t *);
template void InputSection::writeTo<ELF64LE>(uint8_t *);
template void InputSection::writeTo<ELF64BE>(uint8_t *);
template RelsOrRelas<ELF32LE> InputSectionBase::relsOrRelas<ELF32LE>() const;
template RelsOrRelas<ELF32BE> InputSectionBase::relsOrRelas<ELF32BE>() const;
template RelsOrRelas<ELF64LE> InputSectionBase::relsOrRelas<ELF64LE>() const;
template RelsOrRelas<ELF64BE> InputSectionBase::relsOrRelas<ELF64BE>() const;
template MergeInputSection::MergeInputSection(ObjFile<ELF32LE> &,
const ELF32LE::Shdr &, StringRef);
template MergeInputSection::MergeInputSection(ObjFile<ELF32BE> &,

31
lld/ELF/InputSection.h
View File

@ -33,6 +33,13 @@ class OutputSection;
extern std::vector<Partition> partitions;
// Returned by InputSectionBase::relsOrRelas. At least one member is empty.
template <class ELFT> struct RelsOrRelas {
ArrayRef<typename ELFT::Rel> rels;
ArrayRef<typename ELFT::Rela> relas;
bool areRelocsRel() const { return rels.size(); }
};
// This is the base class of all sections that lld handles. Some are sections in
// input files, some are sections in the produced output file and some exist
// just as a convenience for implementing special ways of combining some
@ -114,10 +121,8 @@ public:
static bool classof(const SectionBase *s) { return s->kind() != Output; }
// Relocations that refer to this section.
unsigned numRelocations : 31;
unsigned areRelocsRela : 1;
const void *firstRelocation = nullptr;
// Section index of the relocation section if exists.
uint32_t relSecIdx = 0;
// The file which contains this section. Its dynamic type is always
// ObjFile<ELFT>, but in order to avoid ELFT, we use InputFile as
@ -170,19 +175,7 @@ public:
// used by --gc-sections.
InputSectionBase *nextInSectionGroup = nullptr;
template <class ELFT> ArrayRef<typename ELFT::Rel> rels() const {
assert(!areRelocsRela);
return llvm::makeArrayRef(
static_cast<const typename ELFT::Rel *>(firstRelocation),
numRelocations);
}
template <class ELFT> ArrayRef<typename ELFT::Rela> relas() const {
assert(areRelocsRela);
return llvm::makeArrayRef(
static_cast<const typename ELFT::Rela *>(firstRelocation),
numRelocations);
}
template <class ELFT> RelsOrRelas<ELFT> relsOrRelas() const;
// InputSections that are dependent on us (reverse dependency for GC)
llvm::TinyPtrVector<InputSection *> dependentSections;
@ -392,9 +385,9 @@ private:
};
#ifdef _WIN32
static_assert(sizeof(InputSection) <= 192, "InputSection is too big");
#else
static_assert(sizeof(InputSection) <= 184, "InputSection is too big");
#else
static_assert(sizeof(InputSection) <= 176, "InputSection is too big");
#endif
inline bool isDebugSection(const InputSectionBase &sec) {

23
lld/ELF/MarkLive.cpp
View File

@ -252,13 +252,12 @@ template <class ELFT> void MarkLive<ELFT>::run() {
// referenced by .eh_frame sections, so we scan them for that here.
if (auto *eh = dyn_cast<EhInputSection>(sec)) {
eh->markLive();
if (!eh->numRelocations)
continue;
if (eh->areRelocsRela)
scanEhFrameSection(*eh, eh->template relas<ELFT>());
else
scanEhFrameSection(*eh, eh->template rels<ELFT>());
const RelsOrRelas<ELFT> rels = eh->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
scanEhFrameSection(*eh, rels.rels);
else if (rels.relas.size())
scanEhFrameSection(*eh, rels.relas);
}
if (sec->flags & SHF_GNU_RETAIN) {
@ -288,13 +287,11 @@ template <class ELFT> void MarkLive<ELFT>::mark() {
while (!queue.empty()) {
InputSectionBase &sec = *queue.pop_back_val();
if (sec.areRelocsRela) {
for (const typename ELFT::Rela &rel : sec.template relas<ELFT>())
resolveReloc(sec, rel, false);
} else {
for (const typename ELFT::Rel &rel : sec.template rels<ELFT>())
resolveReloc(sec, rel, false);
}
const RelsOrRelas<ELFT> rels = sec.template relsOrRelas<ELFT>();
for (const typename ELFT::Rel &rel : rels.rels)
resolveReloc(sec, rel, false);
for (const typename ELFT::Rela &rel : rels.relas)
resolveReloc(sec, rel, false);
for (InputSectionBase *isec : sec.dependentSections)
enqueue(isec, 0);

7
lld/ELF/Relocations.cpp
View File

@ -1611,10 +1611,11 @@ static void scanRelocs(InputSectionBase &sec, ArrayRef<RelTy> rels) {
}
template <class ELFT> void elf::scanRelocations(InputSectionBase &s) {
if (s.areRelocsRela)
scanRelocs<ELFT>(s, s.relas<ELFT>());
const RelsOrRelas<ELFT> rels = s.template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
scanRelocs<ELFT>(s, rels.rels);
else
scanRelocs<ELFT>(s, s.rels<ELFT>());
scanRelocs<ELFT>(s, rels.relas);
}
static bool mergeCmp(const InputSection *a, const InputSection *b) {

16
lld/ELF/SyntheticSections.cpp
View File

@ -431,10 +431,11 @@ template <class ELFT>
void EhFrameSection::addSectionAux(EhInputSection *sec) {
if (!sec->isLive())
return;
if (sec->areRelocsRela)
addRecords<ELFT>(sec, sec->template relas<ELFT>());
const RelsOrRelas<ELFT> rels = sec->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
addRecords<ELFT>(sec, rels.rels);
else
addRecords<ELFT>(sec, sec->template rels<ELFT>());
addRecords<ELFT>(sec, rels.relas);
}
void EhFrameSection::addSection(EhInputSection *sec) {
@ -483,12 +484,11 @@ void EhFrameSection::iterateFDEWithLSDA(
DenseSet<size_t> ciesWithLSDA;
for (EhInputSection *sec : sections) {
ciesWithLSDA.clear();
if (sec->areRelocsRela)
iterateFDEWithLSDAAux<ELFT>(*sec, sec->template relas<ELFT>(),
ciesWithLSDA, fn);
const RelsOrRelas<ELFT> rels = sec->template relsOrRelas<ELFT>();
if (rels.areRelocsRel())
iterateFDEWithLSDAAux<ELFT>(*sec, rels.rels, ciesWithLSDA, fn);
else
iterateFDEWithLSDAAux<ELFT>(*sec, sec->template rels<ELFT>(),
ciesWithLSDA, fn);
iterateFDEWithLSDAAux<ELFT>(*sec, rels.relas, ciesWithLSDA, fn);
}
}