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[ELF] Use SmallVector for many SyntheticSections. NFC
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This decreases struct sizes and usually decreases the lld executable
size (39KiB for my x86-64 executable) (unless in some cases smaller
SmallVector leads to more inlining, e.g. StringTableBuilder).
For --gdb-index, there may be memory usage saving.
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@MaskRay
MaskRay committed Dec 18, 2021
1 parent 212e6c9 commit 552d844
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Showing 2 changed files with 32 additions and 31 deletions.
15 changes: 8 additions & 7 deletions lld/ELF/SyntheticSections.cpp
View file
Expand Up @@ -2427,10 +2427,10 @@ static uint32_t hashGnu(StringRef name) {
// Add symbols to this symbol hash table. Note that this function
// destructively sort a given vector -- which is needed because
// GNU-style hash table places some sorting requirements.
void GnuHashTableSection::addSymbols(std::vector<SymbolTableEntry> &v) {
void GnuHashTableSection::addSymbols(SmallVectorImpl<SymbolTableEntry> &v) {
// We cannot use 'auto' for Mid because GCC 6.1 cannot deduce
// its type correctly.
std::vector<SymbolTableEntry>::iterator mid =
auto mid =
std::stable_partition(v.begin(), v.end(), [&](const SymbolTableEntry &s) {
return !s.sym->isDefined() || s.sym->partition != partition;
});
Expand Down Expand Up @@ -2716,16 +2716,17 @@ void GdbIndexSection::initOutputSize() {
}
}

static std::vector<GdbIndexSection::CuEntry> readCuList(DWARFContext &dwarf) {
std::vector<GdbIndexSection::CuEntry> ret;
static SmallVector<GdbIndexSection::CuEntry, 0>
readCuList(DWARFContext &dwarf) {
SmallVector<GdbIndexSection::CuEntry, 0> ret;
for (std::unique_ptr<DWARFUnit> &cu : dwarf.compile_units())
ret.push_back({cu->getOffset(), cu->getLength() + 4});
return ret;
}

static std::vector<GdbIndexSection::AddressEntry>
static SmallVector<GdbIndexSection::AddressEntry, 0>
readAddressAreas(DWARFContext &dwarf, InputSection *sec) {
std::vector<GdbIndexSection::AddressEntry> ret;
SmallVector<GdbIndexSection::AddressEntry, 0> ret;

uint32_t cuIdx = 0;
for (std::unique_ptr<DWARFUnit> &cu : dwarf.compile_units()) {
Expand Down Expand Up @@ -2758,7 +2759,7 @@ readAddressAreas(DWARFContext &dwarf, InputSection *sec) {
template <class ELFT>
static std::vector<GdbIndexSection::NameAttrEntry>
readPubNamesAndTypes(const LLDDwarfObj<ELFT> &obj,
const std::vector<GdbIndexSection::CuEntry> &cus) {
const SmallVectorImpl<GdbIndexSection::CuEntry> &cus) {
const LLDDWARFSection &pubNames = obj.getGnuPubnamesSection();
const LLDDWARFSection &pubTypes = obj.getGnuPubtypesSection();

Expand Down
48 changes: 24 additions & 24 deletions lld/ELF/SyntheticSections.h
View file
Expand Up @@ -61,7 +61,7 @@ class SyntheticSection : public InputSection {

struct CieRecord {
EhSectionPiece *cie = nullptr;
std::vector<EhSectionPiece *> fdes;
SmallVector<EhSectionPiece *, 0> fdes;
};

// Section for .eh_frame.
Expand All @@ -79,7 +79,7 @@ class EhFrameSection final : public SyntheticSection {

void addSection(EhInputSection *sec);

std::vector<EhInputSection *> sections;
SmallVector<EhInputSection *, 0> sections;
size_t numFdes = 0;

struct FdeData {
Expand Down Expand Up @@ -115,7 +115,7 @@ class EhFrameSection final : public SyntheticSection {

uint64_t getFdePc(uint8_t *buf, size_t off, uint8_t enc) const;

std::vector<CieRecord *> cieRecords;
SmallVector<CieRecord *, 0> cieRecords;

// CIE records are uniquified by their contents and personality functions.
llvm::DenseMap<std::pair<ArrayRef<uint8_t>, Symbol *>, CieRecord *> cieMap;
Expand Down Expand Up @@ -387,7 +387,7 @@ class GotPltSection final : public SyntheticSection {
bool hasGotPltOffRel = false;

private:
std::vector<const Symbol *> entries;
SmallVector<const Symbol *, 0> entries;
};

// The IgotPltSection is a Got associated with the PltSection for GNU Ifunc
Expand All @@ -403,7 +403,7 @@ class IgotPltSection final : public SyntheticSection {
bool isNeeded() const override { return !entries.empty(); }

private:
std::vector<const Symbol *> entries;
SmallVector<const Symbol *, 0> entries;
};

class StringTableSection final : public SyntheticSection {
Expand All @@ -420,7 +420,7 @@ class StringTableSection final : public SyntheticSection {
uint64_t size = 0;

llvm::DenseMap<StringRef, unsigned> stringMap;
std::vector<StringRef> strings;
SmallVector<StringRef, 0> strings;
};

class DynamicReloc {
Expand Down Expand Up @@ -540,7 +540,7 @@ class RelocationBaseSection : public SyntheticSection {
d->type == llvm::ELF::SHT_RELR);
}
int32_t dynamicTag, sizeDynamicTag;
std::vector<DynamicReloc> relocs;
SmallVector<DynamicReloc, 0> relocs;

protected:
size_t numRelativeRelocs = 0;
Expand Down Expand Up @@ -588,7 +588,7 @@ class RelrBaseSection : public SyntheticSection {
public:
RelrBaseSection();
bool isNeeded() const override { return !relocs.empty(); }
std::vector<RelativeReloc> relocs;
SmallVector<RelativeReloc, 0> relocs;
};

// RelrSection is used to encode offsets for relative relocations.
Expand All @@ -608,7 +608,7 @@ template <class ELFT> class RelrSection final : public RelrBaseSection {
}

private:
std::vector<Elf_Relr> relrRelocs;
SmallVector<Elf_Relr, 0> relrRelocs;
};

struct SymbolTableEntry {
Expand All @@ -630,7 +630,7 @@ class SymbolTableBaseSection : public SyntheticSection {
void sortSymTabSymbols();

// A vector of symbols and their string table offsets.
std::vector<SymbolTableEntry> symbols;
SmallVector<SymbolTableEntry, 0> symbols;

StringTableSection &strTabSec;

Expand Down Expand Up @@ -669,7 +669,7 @@ class GnuHashTableSection final : public SyntheticSection {

// Adds symbols to the hash table.
// Sorts the input to satisfy GNU hash section requirements.
void addSymbols(std::vector<SymbolTableEntry> &symbols);
void addSymbols(llvm::SmallVectorImpl<SymbolTableEntry> &symbols);

private:
// See the comment in writeBloomFilter.
Expand All @@ -682,7 +682,7 @@ class GnuHashTableSection final : public SyntheticSection {
uint32_t bucketIdx;
};

std::vector<Entry> symbols;
SmallVector<Entry, 0> symbols;
size_t maskWords;
size_t nBuckets = 0;
size_t size = 0;
Expand Down Expand Up @@ -722,15 +722,15 @@ class PltSection : public SyntheticSection {

size_t headerSize;

std::vector<const Symbol *> entries;
SmallVector<const Symbol *, 0> entries;
};

// Used for non-preemptible ifuncs. It does not have a header. Each entry is
// associated with an IRELATIVE relocation, which will be resolved eagerly at
// runtime. PltSection can only contain entries associated with JUMP_SLOT
// relocations, so IPLT entries are in a separate section.
class IpltSection final : public SyntheticSection {
std::vector<const Symbol *> entries;
SmallVector<const Symbol *, 0> entries;

public:
IpltSection();
Expand All @@ -747,7 +747,7 @@ class PPC32GlinkSection : public PltSection {
void writeTo(uint8_t *buf) override;
size_t getSize() const override;

std::vector<const Symbol *> canonical_plts;
SmallVector<const Symbol *, 0> canonical_plts;
static constexpr size_t footerSize = 64;
};

Expand Down Expand Up @@ -780,13 +780,13 @@ class GdbIndexSection final : public SyntheticSection {

struct GdbChunk {
InputSection *sec;
std::vector<AddressEntry> addressAreas;
std::vector<CuEntry> compilationUnits;
SmallVector<AddressEntry, 0> addressAreas;
SmallVector<CuEntry, 0> compilationUnits;
};

struct GdbSymbol {
llvm::CachedHashStringRef name;
std::vector<uint32_t> cuVector;
SmallVector<uint32_t, 0> cuVector;
uint32_t nameOff;
uint32_t cuVectorOff;
};
Expand Down Expand Up @@ -859,7 +859,7 @@ class VersionDefinitionSection final : public SyntheticSection {
StringRef getFileDefName();

unsigned fileDefNameOff;
std::vector<unsigned> verDefNameOffs;
SmallVector<unsigned, 0> verDefNameOffs;
};

// The .gnu.version section specifies the required version of each symbol in the
Expand Down Expand Up @@ -898,7 +898,7 @@ class VersionNeedSection final : public SyntheticSection {
std::vector<Vernaux> vernauxs;
};

std::vector<Verneed> verneeds;
SmallVector<Verneed, 0> verneeds;

public:
VersionNeedSection();
Expand All @@ -915,7 +915,7 @@ class VersionNeedSection final : public SyntheticSection {
class MergeSyntheticSection : public SyntheticSection {
public:
void addSection(MergeInputSection *ms);
std::vector<MergeInputSection *> sections;
SmallVector<MergeInputSection *, 0> sections;

protected:
MergeSyntheticSection(StringRef name, uint32_t type, uint64_t flags,
Expand Down Expand Up @@ -962,7 +962,7 @@ class MergeNoTailSection final : public MergeSyntheticSection {

// String table contents
constexpr static size_t numShards = 32;
std::vector<llvm::StringTableBuilder> shards;
SmallVector<llvm::StringTableBuilder, 0> shards;
size_t shardOffsets[numShards];
};

Expand Down Expand Up @@ -1120,7 +1120,7 @@ class ThunkSection : public SyntheticSection {
bool roundUpSizeForErrata = false;

private:
std::vector<Thunk *> thunks;
SmallVector<Thunk *, 0> thunks;
size_t size = 0;
};

Expand Down Expand Up @@ -1151,7 +1151,7 @@ class PPC64LongBranchTargetSection final : public SyntheticSection {
void finalizeContents() override { finalized = true; }

private:
std::vector<std::pair<const Symbol *, int64_t>> entries;
SmallVector<std::pair<const Symbol *, int64_t>, 0> entries;
llvm::DenseMap<std::pair<const Symbol *, int64_t>, uint32_t> entry_index;
bool finalized = false;
};
Expand Down

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