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Optimize rule-matching by reordering the OutSection-Rule-Sections loop #820

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Optimize rule-matching by reordering the OutSection-Rule-Sections loop #820

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143 changes: 70 additions & 73 deletions lib/Object/ObjectBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,6 @@ void ObjectBuilder::doPluginIterateSections(eld::InputFile *Obj,
}

void ObjectBuilder::assignInputFromOutput(eld::InputFile *Obj) {
std::unordered_map<Section *, bool> RetrySections;
bool IsPartialLink = (ThisConfig.codeGenType() == LinkerConfig::Object);
bool IsGnuCompatible =
(ThisConfig.options().getScriptOption() == GeneralOptions::MatchGNU);
Expand All @@ -273,82 +272,78 @@ void ObjectBuilder::assignInputFromOutput(eld::InputFile *Obj) {
SectionMap &SectionMap = ThisModule.getScript().sectionMap();
ObjectFile *ObjFile = llvm::dyn_cast<ObjectFile>(Obj);
std::vector<Section *> Sections = getInputSectionsForRuleMatching(ObjFile);
// For all output sections.
for (auto *Out : SectionMap) {
// For each input rule.
for (auto *In : *Out) {
auto Start = std::chrono::system_clock::now();
// For each input section.
for (Section *Section : Sections) {
ELFSection *ELFSect = llvm::dyn_cast<eld::ELFSection>(Section);
// For each input section.
for (Section *Sect : Sections) {
ELFSection *ELFSect = llvm::dyn_cast<eld::ELFSection>(Sect);

bool IsRetrySect = false;
bool IsRetrySect = false;

// Skip sections with merge strings and if there is no linker scripts
// provided.
if (IsPartialLink && (ELFSect && ELFSect->isMergeStr()) &&
!LinkerScriptHasSectionsCommand)
continue;
InputFile *Input = Obj;
bool IsCommonSection = false;
if (CommonELFSection *CommonSection =
llvm::dyn_cast<CommonELFSection>(Sect)) {
Input = CommonSection->getOrigin();
IsCommonSection = true;
}
if (Sect->getOldInputFile())
Input = Sect->getOldInputFile();
std::string const &PInputFile =
Input->getInput()->getResolvedPath().native();
std::string const &Name = Input->getInput()->getName();
bool IsArchive = Input->isArchive() ||
llvm::dyn_cast<eld::ArchiveMemberInput>(Input->getInput());
// Hash of all the required things for Match.
uint64_t InputFileHash = Input->getInput()->getResolvedPathHash();
uint64_t NameHash = Input->getInput()->getArchiveMemberNameHash();
std::string SectName = Sect->name().str();
uint64_t InputSectionHash = Sect->sectionNameHash();
if (ELFSection *ELFSect = llvm::dyn_cast<ELFSection>(Sect)) {
if (auto OptRThisSectionName =
ObjFile->getRuleMatchingSectName(ELFSect->getIndex())) {
SectName = OptRThisSectionName.value();
InputSectionHash = llvm::hash_combine(SectName);
}
}
// For all output sections.
for (auto *Out : SectionMap) {
if (ELFSect) {
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@quic-areg quic-areg Feb 13, 2026

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Suggested change
if (ELFSect) {
if (Section->getOutputSection() && !IsRetrySect)
break;
if (ELFSect) {

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@parth-07 parth-07 Mar 17, 2026

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if (Section->getOutputSection() && !IsRetrySect) check needs to stay within the input-section-description loop (for (auto *In : *Out)). Otherwise, we will keep traversing input section descriptions even though the section has already matched an input section description.

// If the rule needs to match on permissions, skip if the rule doesnot
// satisfy.
switch (Out->prolog().constraint()) {
case OutputSectDesc::NO_CONSTRAINT:
break;
case OutputSectDesc::ONLY_IF_RO:
if (ELFSect->isWritable())
continue;
break;
case OutputSectDesc::ONLY_IF_RW:
if (!ELFSect->isWritable())
continue;
break;
}
}
bool shouldSkipMatch = false;
// For each input rule.
for (auto *In : *Out) {
// If the section has an already assigned output section, skip.
// If the section needs to be retried, we may need to revisit the
// section to match the best rule.
if (Section->getOutputSection()) {
if (!RetrySections.size() ||
(RetrySections.find(Section) == RetrySections.end())) {
continue;
}
IsRetrySect = true;
}

if (ELFSect) {
// If the rule needs to match on permissions, skip if the rule doesnot
// satisfy.
switch (Out->prolog().constraint()) {
case OutputSectDesc::NO_CONSTRAINT:
break;
case OutputSectDesc::ONLY_IF_RO:
if (ELFSect->isWritable())
continue;
break;
case OutputSectDesc::ONLY_IF_RW:
if (!ELFSect->isWritable())
continue;
break;
}
}
// Skip sections with merge strings and if there is no linker scripts
// provided.
if (IsPartialLink && (ELFSect && ELFSect->isMergeStr()) &&
!LinkerScriptHasSectionsCommand)
continue;
InputFile *Input = Obj;
bool IsCommonSection = false;
if (CommonELFSection *CommonSection =
llvm::dyn_cast<CommonELFSection>(Section)) {
Input = CommonSection->getOrigin();
IsCommonSection = true;
}
if (Section->getOldInputFile())
Input = Section->getOldInputFile();
std::string const &PInputFile =
Input->getInput()->getResolvedPath().native();
std::string const &Name = Input->getInput()->getName();
bool IsArchive =
Input->isArchive() ||
llvm::dyn_cast<eld::ArchiveMemberInput>(Input->getInput());
// Hash of all the required things for Match.
uint64_t InputFileHash = Input->getInput()->getResolvedPathHash();
uint64_t NameHash = Input->getInput()->getArchiveMemberNameHash();
std::string SectName = Section->name().str();
uint64_t InputSectionHash = Section->sectionNameHash();
if (ELFSection *ELFSect = llvm::dyn_cast<ELFSection>(Section)) {
if (auto OptRThisSectionName =
ObjFile->getRuleMatchingSectName(ELFSect->getIndex())) {
SectName = OptRThisSectionName.value();
InputSectionHash = llvm::hash_combine(SectName);
}
if (Sect->getOutputSection() && !IsRetrySect) {
shouldSkipMatch = true;
break;
}
// auto Start = std::chrono::system_clock::now();
if (SectionMap.matched(*In, Input, PInputFile, SectName, IsArchive,
Name, InputSectionHash, InputFileHash, NameHash,
IsGnuCompatible, IsCommonSection)) {
In->incMatchCount();
Section->setOutputSection(Out);
Section->setMatchedLinkerScriptRule(In);
Sect->setOutputSection(Out);
Sect->setMatchedLinkerScriptRule(In);
// FIXME: Shouldn't we set ELFSect to LDFileFormat::Discard?
if (ELFSect && Out->isDiscard()) {
ELFSect->setKind(LDFileFormat::Ignore);
Expand All @@ -359,15 +354,17 @@ void ObjectBuilder::assignInputFromOutput(eld::InputFile *Obj) {
<< ObjFile->getInput()->decoratedPath();
}
if (IsRetrySect && !In->isSpecial())
RetrySections.erase(Section);
IsRetrySect = false;
// Retry the match until the closest match is found.
if (In->isSpecial())
RetrySections.insert(std::make_pair(Section, true));
IsRetrySect = true;
} // end match
} // end each input section
In->addMatchTime(std::chrono::system_clock::now() - Start);
} // end each rule
} // end each output section
// RuleMatchTimes[In] += std::chrono::system_clock::now() - Start;
} // end each rule
if (shouldSkipMatch)
break;
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@quic-areg quic-areg Feb 13, 2026

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Suggested change
break;

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@parth-07 parth-07 Mar 17, 2026

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We need shouldBreak here to signal that more output sections do not need to be traversed for this input section.

} // end each output section
} // end each input section
}

bool ObjectBuilder::initializePluginsAndProcess(
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