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[ELF] Don't use multiple inheritance for OutputSection. NFC
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Add an OutputDesc class inheriting from SectionCommand. An OutputDesc wraps an
OutputSection. This change allows InputSection::getParent to be inlined.

Differential Revision: https://reviews.llvm.org/D120650
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@MaskRay
MaskRay committed Mar 8, 2022
1 parent 8321579 commit 6c81493
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Showing 10 changed files with 165 additions and 157 deletions.
4 changes: 2 additions & 2 deletions lld/ELF/Driver.cpp
View file
Expand Up @@ -2690,8 +2690,8 @@ void LinkerDriver::link(opt::InputArgList &args) {
// point onwards InputSectionDescription::sections should be used instead of
// sectionBases.
for (SectionCommand *cmd : script->sectionCommands)
if (auto *sec = dyn_cast<OutputSection>(cmd))
sec->finalizeInputSections();
if (auto *osd = dyn_cast<OutputDesc>(cmd))
osd->osec.finalizeInputSections();
llvm::erase_if(inputSections, [](InputSectionBase *s) {
return isa<MergeInputSection>(s);
});
Expand Down
4 changes: 2 additions & 2 deletions lld/ELF/ICF.cpp
View file
Expand Up @@ -568,8 +568,8 @@ template <class ELFT> void ICF<ELFT>::run() {
// InputSectionDescription::sections is populated by processSectionCommands().
// ICF may fold some input sections assigned to output sections. Remove them.
for (SectionCommand *cmd : script->sectionCommands)
if (auto *sec = dyn_cast<OutputSection>(cmd))
for (SectionCommand *subCmd : sec->commands)
if (auto *osd = dyn_cast<OutputDesc>(cmd))
for (SectionCommand *subCmd : osd->osec.commands)
if (auto *isd = dyn_cast<InputSectionDescription>(subCmd))
llvm::erase_if(isd->sections,
[](InputSection *isec) { return !isec->isLive(); });
Expand Down
116 changes: 59 additions & 57 deletions lld/ELF/LinkerScript.cpp
View file
Expand Up @@ -130,26 +130,26 @@ uint64_t ExprValue::getSectionOffset() const {
return getValue() - getSecAddr();
}

OutputSection *LinkerScript::createOutputSection(StringRef name,
StringRef location) {
OutputSection *&secRef = nameToOutputSection[CachedHashStringRef(name)];
OutputSection *sec;
if (secRef && secRef->location.empty()) {
OutputDesc *LinkerScript::createOutputSection(StringRef name,
StringRef location) {
OutputDesc *&secRef = nameToOutputSection[CachedHashStringRef(name)];
OutputDesc *sec;
if (secRef && secRef->osec.location.empty()) {
// There was a forward reference.
sec = secRef;
} else {
sec = make<OutputSection>(name, SHT_PROGBITS, 0);
sec = make<OutputDesc>(name, SHT_PROGBITS, 0);
if (!secRef)
secRef = sec;
}
sec->location = std::string(location);
sec->osec.location = std::string(location);
return sec;
}

OutputSection *LinkerScript::getOrCreateOutputSection(StringRef name) {
OutputSection *&cmdRef = nameToOutputSection[CachedHashStringRef(name)];
OutputDesc *LinkerScript::getOrCreateOutputSection(StringRef name) {
OutputDesc *&cmdRef = nameToOutputSection[CachedHashStringRef(name)];
if (!cmdRef)
cmdRef = make<OutputSection>(name, SHT_PROGBITS, 0);
cmdRef = make<OutputDesc>(name, SHT_PROGBITS, 0);
return cmdRef;
}

Expand Down Expand Up @@ -279,7 +279,7 @@ getSymbolAssignmentValues(ArrayRef<SectionCommand *> sectionCommands) {
assign->sym->value));
continue;
}
for (SectionCommand *subCmd : cast<OutputSection>(cmd)->commands)
for (SectionCommand *subCmd : cast<OutputDesc>(cmd)->osec.commands)
if (auto *assign = dyn_cast<SymbolAssignment>(subCmd))
if (assign->sym)
ret.try_emplace(assign->sym, std::make_pair(assign->sym->section,
Expand All @@ -305,25 +305,25 @@ getChangedSymbolAssignment(const SymbolAssignmentMap &oldValues) {
// Process INSERT [AFTER|BEFORE] commands. For each command, we move the
// specified output section to the designated place.
void LinkerScript::processInsertCommands() {
SmallVector<OutputSection *, 0> moves;
SmallVector<OutputDesc *, 0> moves;
for (const InsertCommand &cmd : insertCommands) {
for (StringRef name : cmd.names) {
// If base is empty, it may have been discarded by
// adjustOutputSections(). We do not handle such output sections.
auto from = llvm::find_if(sectionCommands, [&](SectionCommand *subCmd) {
return isa<OutputSection>(subCmd) &&
cast<OutputSection>(subCmd)->name == name;
return isa<OutputDesc>(subCmd) &&
cast<OutputDesc>(subCmd)->osec.name == name;
});
if (from == sectionCommands.end())
continue;
moves.push_back(cast<OutputSection>(*from));
moves.push_back(cast<OutputDesc>(*from));
sectionCommands.erase(from);
}

auto insertPos =
llvm::find_if(sectionCommands, [&cmd](SectionCommand *subCmd) {
auto *to = dyn_cast<OutputSection>(subCmd);
return to != nullptr && to->name == cmd.where;
auto *to = dyn_cast<OutputDesc>(subCmd);
return to != nullptr && to->osec.name == cmd.where;
});
if (insertPos == sectionCommands.end()) {
error("unable to insert " + cmd.names[0] +
Expand Down Expand Up @@ -352,10 +352,10 @@ void LinkerScript::declareSymbols() {
// we can't say for sure if it is going to be included or not.
// Skip such sections for now. Improve the checks if we ever
// need symbols from that sections to be declared early.
auto *sec = cast<OutputSection>(cmd);
if (sec->constraint != ConstraintKind::NoConstraint)
const OutputSection &sec = cast<OutputDesc>(cmd)->osec;
if (sec.constraint != ConstraintKind::NoConstraint)
continue;
for (SectionCommand *cmd : sec->commands)
for (SectionCommand *cmd : sec.commands)
if (auto *assign = dyn_cast<SymbolAssignment>(cmd))
declareSymbol(assign);
}
Expand Down Expand Up @@ -645,18 +645,20 @@ void LinkerScript::processSectionCommands() {

// Process OVERWRITE_SECTIONS first so that it can overwrite the main script
// or orphans.
DenseMap<CachedHashStringRef, OutputSection *> map;
DenseMap<CachedHashStringRef, OutputDesc *> map;
size_t i = 0;
for (OutputSection *osec : overwriteSections)
for (OutputDesc *osd : overwriteSections) {
OutputSection *osec = &osd->osec;
if (process(osec) &&
!map.try_emplace(CachedHashStringRef(osec->name), osec).second)
!map.try_emplace(CachedHashStringRef(osec->name), osd).second)
warn("OVERWRITE_SECTIONS specifies duplicate " + osec->name);
}
for (SectionCommand *&base : sectionCommands)
if (auto *osec = dyn_cast<OutputSection>(base)) {
if (OutputSection *overwrite =
map.lookup(CachedHashStringRef(osec->name))) {
log(overwrite->location + " overwrites " + osec->name);
overwrite->sectionIndex = i++;
if (auto *osd = dyn_cast<OutputDesc>(base)) {
OutputSection *osec = &osd->osec;
if (OutputDesc *overwrite = map.lookup(CachedHashStringRef(osec->name))) {
log(overwrite->osec.location + " overwrites " + osec->name);
overwrite->osec.sectionIndex = i++;
base = overwrite;
} else if (process(osec)) {
osec->sectionIndex = i++;
Expand All @@ -666,9 +668,9 @@ void LinkerScript::processSectionCommands() {
// If an OVERWRITE_SECTIONS specified output section is not in
// sectionCommands, append it to the end. The section will be inserted by
// orphan placement.
for (OutputSection *osec : overwriteSections)
if (osec->partition == 1 && osec->sectionIndex == UINT32_MAX)
sectionCommands.push_back(osec);
for (OutputDesc *osd : overwriteSections)
if (osd->osec.partition == 1 && osd->osec.sectionIndex == UINT32_MAX)
sectionCommands.push_back(osd);
}

void LinkerScript::processSymbolAssignments() {
Expand All @@ -690,7 +692,7 @@ void LinkerScript::processSymbolAssignments() {
if (auto *assign = dyn_cast<SymbolAssignment>(cmd))
addSymbol(assign);
else
for (SectionCommand *subCmd : cast<OutputSection>(cmd)->commands)
for (SectionCommand *subCmd : cast<OutputDesc>(cmd)->osec.commands)
if (auto *assign = dyn_cast<SymbolAssignment>(subCmd))
addSymbol(assign);
}
Expand All @@ -701,22 +703,20 @@ void LinkerScript::processSymbolAssignments() {
static OutputSection *findByName(ArrayRef<SectionCommand *> vec,
StringRef name) {
for (SectionCommand *cmd : vec)
if (auto *sec = dyn_cast<OutputSection>(cmd))
if (sec->name == name)
return sec;
if (auto *osd = dyn_cast<OutputDesc>(cmd))
if (osd->osec.name == name)
return &osd->osec;
return nullptr;
}

static OutputSection *createSection(InputSectionBase *isec,
StringRef outsecName) {
OutputSection *sec = script->createOutputSection(outsecName, "<internal>");
sec->recordSection(isec);
return sec;
static OutputDesc *createSection(InputSectionBase *isec, StringRef outsecName) {
OutputDesc *osd = script->createOutputSection(outsecName, "<internal>");
osd->osec.recordSection(isec);
return osd;
}

static OutputSection *
addInputSec(StringMap<TinyPtrVector<OutputSection *>> &map,
InputSectionBase *isec, StringRef outsecName) {
static OutputDesc *addInputSec(StringMap<TinyPtrVector<OutputSection *>> &map,
InputSectionBase *isec, StringRef outsecName) {
// Sections with SHT_GROUP or SHF_GROUP attributes reach here only when the -r
// option is given. A section with SHT_GROUP defines a "section group", and
// its members have SHF_GROUP attribute. Usually these flags have already been
Expand All @@ -743,8 +743,9 @@ addInputSec(StringMap<TinyPtrVector<OutputSection *>> &map,
return nullptr;
}

out->relocationSection = createSection(isec, outsecName);
return out->relocationSection;
OutputDesc *osd = createSection(isec, outsecName);
out->relocationSection = &osd->osec;
return osd;
}

// The ELF spec just says
Expand Down Expand Up @@ -813,15 +814,15 @@ addInputSec(StringMap<TinyPtrVector<OutputSection *>> &map,
return nullptr;
}

OutputSection *sec = createSection(isec, outsecName);
v.push_back(sec);
return sec;
OutputDesc *osd = createSection(isec, outsecName);
v.push_back(&osd->osec);
return osd;
}

// Add sections that didn't match any sections command.
void LinkerScript::addOrphanSections() {
StringMap<TinyPtrVector<OutputSection *>> map;
SmallVector<OutputSection *, 0> v;
SmallVector<OutputDesc *, 0> v;

auto add = [&](InputSectionBase *s) {
if (s->isLive() && !s->parent) {
Expand All @@ -833,8 +834,8 @@ void LinkerScript::addOrphanSections() {
} else if (OutputSection *sec = findByName(sectionCommands, name)) {
sec->recordSection(s);
} else {
if (OutputSection *os = addInputSec(map, s, name))
v.push_back(os);
if (OutputDesc *osd = addInputSec(map, s, name))
v.push_back(osd);
assert(isa<MergeInputSection>(s) ||
s->getOutputSection()->sectionIndex == UINT32_MAX);
}
Expand Down Expand Up @@ -1138,9 +1139,9 @@ void LinkerScript::adjustOutputSections() {

SmallVector<StringRef, 0> defPhdrs;
for (SectionCommand *&cmd : sectionCommands) {
auto *sec = dyn_cast<OutputSection>(cmd);
if (!sec)
if (!isa<OutputDesc>(cmd))
continue;
auto *sec = &cast<OutputDesc>(cmd)->osec;

// Handle align (e.g. ".foo : ALIGN(16) { ... }").
if (sec->alignExpr)
Expand Down Expand Up @@ -1192,7 +1193,8 @@ void LinkerScript::adjustSectionsAfterSorting() {
// Try and find an appropriate memory region to assign offsets in.
MemoryRegion *hint = nullptr;
for (SectionCommand *cmd : sectionCommands) {
if (auto *sec = dyn_cast<OutputSection>(cmd)) {
if (auto *osd = dyn_cast<OutputDesc>(cmd)) {
OutputSection *sec = &osd->osec;
if (!sec->lmaRegionName.empty()) {
if (MemoryRegion *m = memoryRegions.lookup(sec->lmaRegionName))
sec->lmaRegion = m;
Expand All @@ -1219,8 +1221,8 @@ void LinkerScript::adjustSectionsAfterSorting() {
// Walk the commands and propagate the program headers to commands that don't
// explicitly specify them.
for (SectionCommand *cmd : sectionCommands)
if (auto *sec = dyn_cast<OutputSection>(cmd))
maybePropagatePhdrs(*sec, defPhdrs);
if (auto *osd = dyn_cast<OutputDesc>(cmd))
maybePropagatePhdrs(osd->osec, defPhdrs);
}

static uint64_t computeBase(uint64_t min, bool allocateHeaders) {
Expand Down Expand Up @@ -1315,7 +1317,7 @@ const Defined *LinkerScript::assignAddresses() {
assign->size = dot - assign->addr;
continue;
}
assignOffsets(cast<OutputSection>(cmd));
assignOffsets(&cast<OutputDesc>(cmd)->osec);
}

ctx = nullptr;
Expand Down
10 changes: 5 additions & 5 deletions lld/ELF/LinkerScript.h
View file
Expand Up @@ -32,6 +32,7 @@ class InputSectionBase;
class OutputSection;
class SectionBase;
class ThunkSection;
struct OutputDesc;

// This represents an r-value in the linker script.
struct ExprValue {
Expand Down Expand Up @@ -267,8 +268,7 @@ class LinkerScript final {
uint64_t tbssAddr = 0;
};

llvm::DenseMap<llvm::CachedHashStringRef, OutputSection *>
nameToOutputSection;
llvm::DenseMap<llvm::CachedHashStringRef, OutputDesc *> nameToOutputSection;

void addSymbol(SymbolAssignment *cmd);
void assignSymbol(SymbolAssignment *cmd, bool inSec);
Expand Down Expand Up @@ -304,8 +304,8 @@ class LinkerScript final {
uint64_t dot;

public:
OutputSection *createOutputSection(StringRef name, StringRef location);
OutputSection *getOrCreateOutputSection(StringRef name);
OutputDesc *createOutputSection(StringRef name, StringRef location);
OutputDesc *getOrCreateOutputSection(StringRef name);

bool hasPhdrsCommands() { return !phdrsCommands.empty(); }
uint64_t getDot() { return dot; }
Expand Down Expand Up @@ -357,7 +357,7 @@ class LinkerScript final {
SmallVector<InsertCommand, 0> insertCommands;

// OutputSections specified by OVERWRITE_SECTIONS.
SmallVector<OutputSection *, 0> overwriteSections;
SmallVector<OutputDesc *, 0> overwriteSections;

// Sections that will be warned/errored by --orphan-handling.
SmallVector<const InputSectionBase *, 0> orphanSections;
Expand Down
2 changes: 1 addition & 1 deletion lld/ELF/MapFile.cpp
View file
Expand Up @@ -168,7 +168,7 @@ static void writeMapFile(raw_fd_ostream &os) {
continue;
}

osec = cast<OutputSection>(cmd);
osec = &cast<OutputDesc>(cmd)->osec;
writeHeader(os, osec->addr, osec->getLMA(), osec->size, osec->alignment);
os << osec->name << '\n';

Expand Down
7 changes: 1 addition & 6 deletions lld/ELF/OutputSections.cpp
View file
Expand Up @@ -68,8 +68,7 @@ void OutputSection::writeHeaderTo(typename ELFT::Shdr *shdr) {
}

OutputSection::OutputSection(StringRef name, uint32_t type, uint64_t flags)
: SectionCommand(OutputSectionKind),
SectionBase(Output, name, flags, /*Entsize*/ 0, /*Alignment*/ 1, type,
: SectionBase(Output, name, flags, /*Entsize*/ 0, /*Alignment*/ 1, type,
/*Info*/ 0, /*Link*/ 0) {}

// We allow sections of types listed below to merged into a
Expand Down Expand Up @@ -251,10 +250,6 @@ uint64_t elf::getHeaderSize() {
return Out::elfHeader->size + Out::programHeaders->size;
}

bool OutputSection::classof(const SectionCommand *c) {
return c->kind == OutputSectionKind;
}

void OutputSection::sort(llvm::function_ref<int(InputSectionBase *s)> order) {
assert(isLive());
for (SectionCommand *b : commands)
Expand Down
14 changes: 11 additions & 3 deletions lld/ELF/OutputSections.h
View file
Expand Up @@ -31,16 +31,14 @@ struct CompressedData {
// It is composed of multiple InputSections.
// The writer creates multiple OutputSections and assign them unique,
// non-overlapping file offsets and VAs.
class OutputSection final : public SectionCommand, public SectionBase {
class OutputSection final : public SectionBase {
public:
OutputSection(StringRef name, uint32_t type, uint64_t flags);

static bool classof(const SectionBase *s) {
return s->kind() == SectionBase::Output;
}

static bool classof(const SectionCommand *c);

uint64_t getLMA() const { return ptLoad ? addr + ptLoad->lmaOffset : addr; }
template <typename ELFT> void writeHeaderTo(typename ELFT::Shdr *sHdr);

Expand Down Expand Up @@ -119,6 +117,16 @@ class OutputSection final : public SectionCommand, public SectionBase {
std::array<uint8_t, 4> getFiller();
};

struct OutputDesc final : SectionCommand {
OutputSection osec;
OutputDesc(StringRef name, uint32_t type, uint64_t flags)
: SectionCommand(OutputSectionKind), osec(name, type, flags) {}

static bool classof(const SectionCommand *c) {
return c->kind == OutputSectionKind;
}
};

int getPriority(StringRef s);

InputSection *getFirstInputSection(const OutputSection *os);
Expand Down

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