[llvm] [MC][ELF] Eliminate some hash maps from ELFObjectWriter (PR #97421)
Alexis Engelke via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 3 02:39:02 PDT 2024
https://github.com/aengelke updated https://github.com/llvm/llvm-project/pull/97421
>From 11e95ce9dccbc19e9c0d22ef0a3ff587961a8692 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 19 Jun 2024 16:09:14 +0200
Subject: [PATCH 1/7] [MC][ELF] Replace SectionIndexMap with layout order
The section layout order is only used in MachO, so we can repurpose the
field as section table index.
---
llvm/lib/MC/ELFObjectWriter.cpp | 41 +++++++++++----------------------
1 file changed, 13 insertions(+), 28 deletions(-)
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index bcc6dfeeeccd6..12d746b99f03a 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -66,8 +66,6 @@ using namespace llvm;
namespace {
-using SectionIndexMapTy = DenseMap<const MCSectionELF *, uint32_t>;
-
class ELFObjectWriter;
struct ELFWriter;
@@ -181,10 +179,8 @@ struct ELFWriter {
/// Compute the symbol table data
///
/// \param Asm - The assembler.
- /// \param SectionIndexMap - Maps a section to its index.
/// \param RevGroupMap - Maps a signature symbol to the group section.
void computeSymbolTable(MCAssembler &Asm,
- const SectionIndexMapTy &SectionIndexMap,
const RevGroupMapTy &RevGroupMap,
SectionOffsetsTy &SectionOffsets);
@@ -194,7 +190,6 @@ struct ELFWriter {
const MCSectionELF &Sec);
void writeSectionHeader(const MCAssembler &Asm,
- const SectionIndexMapTy &SectionIndexMap,
const SectionOffsetsTy &SectionOffsets);
void writeSectionData(const MCAssembler &Asm, MCSection &Sec);
@@ -207,8 +202,7 @@ struct ELFWriter {
void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
uint64_t writeObject(MCAssembler &Asm);
- void writeSection(const SectionIndexMapTy &SectionIndexMap,
- uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
+ void writeSection(uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
const MCSectionELF &Section);
};
@@ -612,7 +606,6 @@ bool ELFWriter::isInSymtab(const MCAssembler &Asm, const MCSymbolELF &Symbol,
}
void ELFWriter::computeSymbolTable(MCAssembler &Asm,
- const SectionIndexMapTy &SectionIndexMap,
const RevGroupMapTy &RevGroupMap,
SectionOffsetsTy &SectionOffsets) {
MCContext &Ctx = Asm.getContext();
@@ -697,7 +690,7 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm,
if (Mode == NonDwoOnly && isDwoSection(Section))
continue;
- MSD.SectionIndex = SectionIndexMap.lookup(&Section);
+ MSD.SectionIndex = Section.getLayoutOrder();
assert(MSD.SectionIndex && "Invalid section index!");
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
HasLargeSectionIndex = true;
@@ -1030,8 +1023,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
}
}
-void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
- uint32_t GroupSymbolIndex, uint64_t Offset,
+void ELFWriter::writeSection(uint32_t GroupSymbolIndex, uint64_t Offset,
uint64_t Size, const MCSectionELF &Section) {
uint64_t sh_link = 0;
uint64_t sh_info = 0;
@@ -1050,7 +1042,7 @@ void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
sh_link = SymbolTableIndex;
assert(sh_link && ".symtab not found");
const MCSection *InfoSection = Section.getLinkedToSection();
- sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
+ sh_info = InfoSection->getLayoutOrder();
break;
}
@@ -1075,10 +1067,8 @@ void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
// If the value in the associated metadata is not a definition, Sym will be
// undefined. Represent this with sh_link=0.
const MCSymbol *Sym = Section.getLinkedToSymbol();
- if (Sym && Sym->isInSection()) {
- const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
- sh_link = SectionIndexMap.lookup(Sec);
- }
+ if (Sym && Sym->isInSection())
+ sh_link = Sym->getSection().getLayoutOrder();
}
WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getName()),
@@ -1088,7 +1078,6 @@ void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
}
void ELFWriter::writeSectionHeader(const MCAssembler &Asm,
- const SectionIndexMapTy &SectionIndexMap,
const SectionOffsetsTy &SectionOffsets) {
const unsigned NumSections = SectionTable.size();
@@ -1113,8 +1102,7 @@ void ELFWriter::writeSectionHeader(const MCAssembler &Asm,
else
Size = Offsets.second - Offsets.first;
- writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
- *Section);
+ writeSection(GroupSymbolIndex, Offsets.first, Size, *Section);
}
}
@@ -1127,7 +1115,6 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
StringTableIndex = addToSectionTable(StrtabSection);
RevGroupMapTy RevGroupMap;
- SectionIndexMapTy SectionIndexMap;
DenseMap<const MCSymbol *, SmallVector<const MCSectionELF *, 0>> GroupMembers;
@@ -1172,9 +1159,9 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Members.push_back(RelSection);
}
- SectionIndexMap[&Section] = addToSectionTable(&Section);
+ Section.setLayoutOrder(addToSectionTable(&Section));
if (RelSection) {
- SectionIndexMap[RelSection] = addToSectionTable(RelSection);
+ RelSection->setLayoutOrder(addToSectionTable(RelSection));
Relocations.push_back(RelSection);
}
@@ -1188,10 +1175,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
const MCSymbol *SignatureSymbol = Group->getGroup();
assert(SignatureSymbol);
write(uint32_t(Group->isComdat() ? unsigned(ELF::GRP_COMDAT) : 0));
- for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
- uint32_t SecIndex = SectionIndexMap.lookup(Member);
- write(SecIndex);
- }
+ for (const MCSectionELF *Member : GroupMembers[SignatureSymbol])
+ write(Member->getLayoutOrder());
uint64_t SecEnd = W.OS.tell();
SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
@@ -1210,7 +1195,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
}
// Compute symbol table information.
- computeSymbolTable(Asm, SectionIndexMap, RevGroupMap, SectionOffsets);
+ computeSymbolTable(Asm, RevGroupMap, SectionOffsets);
for (MCSectionELF *RelSection : Relocations) {
// Remember the offset into the file for this section.
@@ -1240,7 +1225,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
const uint64_t SectionHeaderOffset = align(is64Bit() ? Align(8) : Align(4));
// ... then the section header table ...
- writeSectionHeader(Asm, SectionIndexMap, SectionOffsets);
+ writeSectionHeader(Asm, SectionOffsets);
uint16_t NumSections = support::endian::byte_swap<uint16_t>(
(SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
>From a9f1734d2bd905083a4497fed2197c0b359a08a0 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 19 Jun 2024 16:26:33 +0200
Subject: [PATCH 2/7] [MC][ELF] Store section offsets in MCSectionELF
No need for a map, and especially not a std::map. Direct access to the
underlying (and easily modifyable) data structure is always faster.
---
llvm/include/llvm/MC/MCSectionELF.h | 12 ++++++++
llvm/lib/MC/ELFObjectWriter.cpp | 47 +++++++++++------------------
2 files changed, 30 insertions(+), 29 deletions(-)
diff --git a/llvm/include/llvm/MC/MCSectionELF.h b/llvm/include/llvm/MC/MCSectionELF.h
index 3d45d3da10ca1..d43ffbd885c96 100644
--- a/llvm/include/llvm/MC/MCSectionELF.h
+++ b/llvm/include/llvm/MC/MCSectionELF.h
@@ -46,6 +46,10 @@ class MCSectionELF final : public MCSection {
/// section header index of the section where LinkedToSym is defined.
const MCSymbol *LinkedToSym;
+ /// Start/end offset in file, used by ELFWriter.
+ uint64_t StartOffset;
+ uint64_t EndOffset;
+
private:
friend class MCContext;
@@ -92,6 +96,14 @@ class MCSectionELF final : public MCSection {
}
const MCSymbol *getLinkedToSymbol() const { return LinkedToSym; }
+ void setOffsets(uint64_t Start, uint64_t End) {
+ StartOffset = Start;
+ EndOffset = End;
+ }
+ std::pair<uint64_t, uint64_t> getOffsets() const {
+ return std::make_pair(StartOffset, EndOffset);
+ }
+
static bool classof(const MCSection *S) {
return S->getVariant() == SV_ELF;
}
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 12d746b99f03a..77a56878f6d81 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -134,8 +134,8 @@ struct ELFWriter {
unsigned SymbolTableIndex = ~0u;
// Sections in the order they are to be output in the section table.
- std::vector<const MCSectionELF *> SectionTable;
- unsigned addToSectionTable(const MCSectionELF *Sec);
+ std::vector<MCSectionELF *> SectionTable;
+ unsigned addToSectionTable(MCSectionELF *Sec);
// TargetObjectWriter wrappers.
bool is64Bit() const;
@@ -169,10 +169,6 @@ struct ELFWriter {
void writeSymbol(const MCAssembler &Asm, SymbolTableWriter &Writer,
uint32_t StringIndex, ELFSymbolData &MSD);
- // Start and end offset of each section
- using SectionOffsetsTy =
- std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>;
-
// Map from a signature symbol to the group section index
using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
@@ -181,16 +177,14 @@ struct ELFWriter {
/// \param Asm - The assembler.
/// \param RevGroupMap - Maps a signature symbol to the group section.
void computeSymbolTable(MCAssembler &Asm,
- const RevGroupMapTy &RevGroupMap,
- SectionOffsetsTy &SectionOffsets);
+ const RevGroupMapTy &RevGroupMap);
void writeAddrsigSection();
MCSectionELF *createRelocationSection(MCContext &Ctx,
const MCSectionELF &Sec);
- void writeSectionHeader(const MCAssembler &Asm,
- const SectionOffsetsTy &SectionOffsets);
+ void writeSectionHeader(const MCAssembler &Asm);
void writeSectionData(const MCAssembler &Asm, MCSection &Sec);
@@ -324,7 +318,7 @@ uint64_t ELFWriter::align(Align Alignment) {
return NewOffset;
}
-unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
+unsigned ELFWriter::addToSectionTable(MCSectionELF *Sec) {
SectionTable.push_back(Sec);
StrTabBuilder.add(Sec->getName());
return SectionTable.size();
@@ -606,8 +600,7 @@ bool ELFWriter::isInSymtab(const MCAssembler &Asm, const MCSymbolELF &Symbol,
}
void ELFWriter::computeSymbolTable(MCAssembler &Asm,
- const RevGroupMapTy &RevGroupMap,
- SectionOffsetsTy &SectionOffsets) {
+ const RevGroupMapTy &RevGroupMap) {
MCContext &Ctx = Asm.getContext();
SymbolTableWriter Writer(*this, is64Bit());
@@ -768,7 +761,7 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm,
}
uint64_t SecEnd = W.OS.tell();
- SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
+ SymtabSection->setOffsets(SecStart, SecEnd);
ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
if (ShndxIndexes.empty()) {
@@ -778,12 +771,11 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm,
assert(SymtabShndxSectionIndex != 0);
SecStart = W.OS.tell();
- const MCSectionELF *SymtabShndxSection =
- SectionTable[SymtabShndxSectionIndex - 1];
+ MCSectionELF *SymtabShndxSection = SectionTable[SymtabShndxSectionIndex - 1];
for (uint32_t Index : ShndxIndexes)
write(Index);
SecEnd = W.OS.tell();
- SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
+ SymtabShndxSection->setOffsets(SecStart, SecEnd);
}
void ELFWriter::writeAddrsigSection() {
@@ -1077,8 +1069,7 @@ void ELFWriter::writeSection(uint32_t GroupSymbolIndex, uint64_t Offset,
Section.getEntrySize());
}
-void ELFWriter::writeSectionHeader(const MCAssembler &Asm,
- const SectionOffsetsTy &SectionOffsets) {
+void ELFWriter::writeSectionHeader(const MCAssembler &Asm) {
const unsigned NumSections = SectionTable.size();
// Null section first.
@@ -1094,8 +1085,7 @@ void ELFWriter::writeSectionHeader(const MCAssembler &Asm,
else
GroupSymbolIndex = Section->getGroup()->getIndex();
- const std::pair<uint64_t, uint64_t> &Offsets =
- SectionOffsets.find(Section)->second;
+ std::pair<uint64_t, uint64_t> Offsets = Section->getOffsets();
uint64_t Size;
if (Type == ELF::SHT_NOBITS)
Size = Asm.getSectionAddressSize(*Section);
@@ -1122,7 +1112,6 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
writeHeader(Asm);
// ... then the sections ...
- SectionOffsetsTy SectionOffsets;
std::vector<MCSectionELF *> Groups;
std::vector<MCSectionELF *> Relocations;
for (MCSection &Sec : Asm) {
@@ -1139,7 +1128,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
writeSectionData(Asm, Section);
uint64_t SecEnd = W.OS.tell();
- SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
+ Section.setOffsets(SecStart, SecEnd);
MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
@@ -1179,7 +1168,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
write(Member->getLayoutOrder());
uint64_t SecEnd = W.OS.tell();
- SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
+ Group->setOffsets(SecStart, SecEnd);
}
if (Mode == DwoOnly) {
@@ -1195,7 +1184,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
}
// Compute symbol table information.
- computeSymbolTable(Asm, RevGroupMap, SectionOffsets);
+ computeSymbolTable(Asm, RevGroupMap);
for (MCSectionELF *RelSection : Relocations) {
// Remember the offset into the file for this section.
@@ -1205,27 +1194,27 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
cast<MCSectionELF>(*RelSection->getLinkedToSection()));
uint64_t SecEnd = W.OS.tell();
- SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
+ RelSection->setOffsets(SecStart, SecEnd);
}
if (OWriter.EmitAddrsigSection) {
uint64_t SecStart = W.OS.tell();
writeAddrsigSection();
uint64_t SecEnd = W.OS.tell();
- SectionOffsets[AddrsigSection] = std::make_pair(SecStart, SecEnd);
+ AddrsigSection->setOffsets(SecStart, SecEnd);
}
}
{
uint64_t SecStart = W.OS.tell();
StrTabBuilder.write(W.OS);
- SectionOffsets[StrtabSection] = std::make_pair(SecStart, W.OS.tell());
+ StrtabSection->setOffsets(SecStart, W.OS.tell());
}
const uint64_t SectionHeaderOffset = align(is64Bit() ? Align(8) : Align(4));
// ... then the section header table ...
- writeSectionHeader(Asm, SectionOffsets);
+ writeSectionHeader(Asm);
uint16_t NumSections = support::endian::byte_swap<uint16_t>(
(SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
>From ece182bea6a8ca0ac0c59e455bd2b5614a3a59b0 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 19 Jun 2024 16:46:24 +0200
Subject: [PATCH 3/7] [MC][ELF] Store signature group idx in MCSymbolELF
This removes the need for a reverse lookup map.
---
llvm/include/llvm/MC/MCSymbolELF.h | 6 ++++++
llvm/lib/MC/ELFObjectWriter.cpp | 19 ++++++-------------
2 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/llvm/include/llvm/MC/MCSymbolELF.h b/llvm/include/llvm/MC/MCSymbolELF.h
index 13c2c6b13f8e1..aa1531a897121 100644
--- a/llvm/include/llvm/MC/MCSymbolELF.h
+++ b/llvm/include/llvm/MC/MCSymbolELF.h
@@ -17,6 +17,9 @@ class MCSymbolELF : public MCSymbol {
/// symbol has no size this field will be NULL.
const MCExpr *SymbolSize = nullptr;
+ /// Group section index for signature symbols. Set by ELFWriter.
+ mutable unsigned GroupIndex = 0;
+
public:
MCSymbolELF(const MCSymbolTableEntry *Name, bool isTemporary)
: MCSymbol(SymbolKindELF, Name, isTemporary) {}
@@ -44,6 +47,9 @@ class MCSymbolELF : public MCSymbol {
void setIsSignature() const;
bool isSignature() const;
+ void setGroupIndex(unsigned Index) const { GroupIndex = Index; }
+ unsigned getGroupIndex() const { return GroupIndex; }
+
void setMemtag(bool Tagged);
bool isMemtag() const;
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 77a56878f6d81..64d0d43017c8e 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -169,15 +169,10 @@ struct ELFWriter {
void writeSymbol(const MCAssembler &Asm, SymbolTableWriter &Writer,
uint32_t StringIndex, ELFSymbolData &MSD);
- // Map from a signature symbol to the group section index
- using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
-
/// Compute the symbol table data
///
/// \param Asm - The assembler.
- /// \param RevGroupMap - Maps a signature symbol to the group section.
- void computeSymbolTable(MCAssembler &Asm,
- const RevGroupMapTy &RevGroupMap);
+ void computeSymbolTable(MCAssembler &Asm);
void writeAddrsigSection();
@@ -599,8 +594,7 @@ bool ELFWriter::isInSymtab(const MCAssembler &Asm, const MCSymbolELF &Symbol,
return true;
}
-void ELFWriter::computeSymbolTable(MCAssembler &Asm,
- const RevGroupMapTy &RevGroupMap) {
+void ELFWriter::computeSymbolTable(MCAssembler &Asm) {
MCContext &Ctx = Asm.getContext();
SymbolTableWriter Writer(*this, is64Bit());
@@ -658,7 +652,7 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm,
}
} else if (Symbol.isUndefined()) {
if (isSignature && !Used) {
- MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
+ MSD.SectionIndex = Symbol.getGroupIndex();
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
HasLargeSectionIndex = true;
} else {
@@ -1104,8 +1098,6 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
StringTableIndex = addToSectionTable(StrtabSection);
- RevGroupMapTy RevGroupMap;
-
DenseMap<const MCSymbol *, SmallVector<const MCSectionELF *, 0>> GroupMembers;
// Write out the ELF header ...
@@ -1133,11 +1125,12 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
if (SignatureSymbol) {
- unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
+ unsigned GroupIdx = SignatureSymbol->getGroupIndex();
if (!GroupIdx) {
MCSectionELF *Group =
Ctx.createELFGroupSection(SignatureSymbol, Section.isComdat());
GroupIdx = addToSectionTable(Group);
+ SignatureSymbol->setGroupIndex(GroupIdx);
Group->setAlignment(Align(4));
Groups.push_back(Group);
}
@@ -1184,7 +1177,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
}
// Compute symbol table information.
- computeSymbolTable(Asm, RevGroupMap);
+ computeSymbolTable(Asm);
for (MCSectionELF *RelSection : Relocations) {
// Remember the offset into the file for this section.
>From 7a844269e053e835a03cf27b4447ee12e4a0dca1 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 19 Jun 2024 17:13:06 +0200
Subject: [PATCH 4/7] [MC][ELF] Improve storage of groups and relocations
There's no point in having a DenseMap, the number of sections and groups
are reasonably small to use vectors.
---
llvm/lib/MC/ELFObjectWriter.cpp | 35 ++++++++++++++++++---------------
1 file changed, 19 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 64d0d43017c8e..de55bdc00301b 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1098,14 +1098,14 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
StringTableIndex = addToSectionTable(StrtabSection);
- DenseMap<const MCSymbol *, SmallVector<const MCSectionELF *, 0>> GroupMembers;
-
// Write out the ELF header ...
writeHeader(Asm);
// ... then the sections ...
- std::vector<MCSectionELF *> Groups;
- std::vector<MCSectionELF *> Relocations;
+ SmallVector<std::pair<MCSectionELF *, SmallVector<unsigned>>, 0> Groups;
+ // Map from group section index to group
+ SmallVector<unsigned, 0> GroupMap;
+ SmallVector<MCSectionELF *> Relocations;
for (MCSection &Sec : Asm) {
MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
if (Mode == NonDwoOnly && isDwoSection(Section))
@@ -1124,21 +1124,20 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
+ unsigned GroupIdx = 0;
if (SignatureSymbol) {
- unsigned GroupIdx = SignatureSymbol->getGroupIndex();
+ GroupIdx = SignatureSymbol->getGroupIndex();
if (!GroupIdx) {
MCSectionELF *Group =
Ctx.createELFGroupSection(SignatureSymbol, Section.isComdat());
GroupIdx = addToSectionTable(Group);
SignatureSymbol->setGroupIndex(GroupIdx);
Group->setAlignment(Align(4));
- Groups.push_back(Group);
+
+ GroupMap.resize(GroupIdx + 1);
+ GroupMap[GroupIdx] = Groups.size();
+ Groups.emplace_back(Group, SmallVector<unsigned>{});
}
- SmallVector<const MCSectionELF *, 0> &Members =
- GroupMembers[SignatureSymbol];
- Members.push_back(&Section);
- if (RelSection)
- Members.push_back(RelSection);
}
Section.setLayoutOrder(addToSectionTable(&Section));
@@ -1147,18 +1146,22 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Relocations.push_back(RelSection);
}
+ if (GroupIdx) {
+ auto &Members = Groups[GroupMap[GroupIdx]];
+ Members.second.push_back(Section.getLayoutOrder());
+ if (RelSection)
+ Members.second.push_back(RelSection->getLayoutOrder());
+ }
+
OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
}
- for (MCSectionELF *Group : Groups) {
+ for (auto &[Group, Members] : Groups) {
// Remember the offset into the file for this section.
const uint64_t SecStart = align(Group->getAlign());
- const MCSymbol *SignatureSymbol = Group->getGroup();
- assert(SignatureSymbol);
write(uint32_t(Group->isComdat() ? unsigned(ELF::GRP_COMDAT) : 0));
- for (const MCSectionELF *Member : GroupMembers[SignatureSymbol])
- write(Member->getLayoutOrder());
+ W.write<unsigned>(Members);
uint64_t SecEnd = W.OS.tell();
Group->setOffsets(SecStart, SecEnd);
>From 9be8065e04b8407afda55517d15648deffcb7e29 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 3 Jul 2024 08:16:07 +0000
Subject: [PATCH 5/7] Revert "[MC][ELF] Store signature group idx in
MCSymbolELF"
This reverts commit ece182bea6a8ca0ac0c59e455bd2b5614a3a59b0.
---
llvm/include/llvm/MC/MCSymbolELF.h | 6 ------
llvm/lib/MC/ELFObjectWriter.cpp | 33 ++++++++++++++++++------------
2 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/llvm/include/llvm/MC/MCSymbolELF.h b/llvm/include/llvm/MC/MCSymbolELF.h
index aa1531a897121..13c2c6b13f8e1 100644
--- a/llvm/include/llvm/MC/MCSymbolELF.h
+++ b/llvm/include/llvm/MC/MCSymbolELF.h
@@ -17,9 +17,6 @@ class MCSymbolELF : public MCSymbol {
/// symbol has no size this field will be NULL.
const MCExpr *SymbolSize = nullptr;
- /// Group section index for signature symbols. Set by ELFWriter.
- mutable unsigned GroupIndex = 0;
-
public:
MCSymbolELF(const MCSymbolTableEntry *Name, bool isTemporary)
: MCSymbol(SymbolKindELF, Name, isTemporary) {}
@@ -47,9 +44,6 @@ class MCSymbolELF : public MCSymbol {
void setIsSignature() const;
bool isSignature() const;
- void setGroupIndex(unsigned Index) const { GroupIndex = Index; }
- unsigned getGroupIndex() const { return GroupIndex; }
-
void setMemtag(bool Tagged);
bool isMemtag() const;
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index de55bdc00301b..41e3284eeeae9 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -169,10 +169,15 @@ struct ELFWriter {
void writeSymbol(const MCAssembler &Asm, SymbolTableWriter &Writer,
uint32_t StringIndex, ELFSymbolData &MSD);
+ // Map from a signature symbol to the group section index
+ using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
+
/// Compute the symbol table data
///
/// \param Asm - The assembler.
- void computeSymbolTable(MCAssembler &Asm);
+ /// \param RevGroupMap - Maps a signature symbol to the group section.
+ void computeSymbolTable(MCAssembler &Asm,
+ const RevGroupMapTy &RevGroupMap);
void writeAddrsigSection();
@@ -594,7 +599,8 @@ bool ELFWriter::isInSymtab(const MCAssembler &Asm, const MCSymbolELF &Symbol,
return true;
}
-void ELFWriter::computeSymbolTable(MCAssembler &Asm) {
+void ELFWriter::computeSymbolTable(MCAssembler &Asm,
+ const RevGroupMapTy &RevGroupMap) {
MCContext &Ctx = Asm.getContext();
SymbolTableWriter Writer(*this, is64Bit());
@@ -652,7 +658,7 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm) {
}
} else if (Symbol.isUndefined()) {
if (isSignature && !Used) {
- MSD.SectionIndex = Symbol.getGroupIndex();
+ MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
HasLargeSectionIndex = true;
} else {
@@ -1098,6 +1104,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
StringTableIndex = addToSectionTable(StrtabSection);
+ RevGroupMapTy RevGroupMap;
+
// Write out the ELF header ...
writeHeader(Asm);
@@ -1124,18 +1132,17 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
- unsigned GroupIdx = 0;
+ unsigned *GroupIdxEntry = nullptr;
if (SignatureSymbol) {
- GroupIdx = SignatureSymbol->getGroupIndex();
- if (!GroupIdx) {
+ GroupIdxEntry = &RevGroupMap[SignatureSymbol];
+ if (!*GroupIdxEntry) {
MCSectionELF *Group =
Ctx.createELFGroupSection(SignatureSymbol, Section.isComdat());
- GroupIdx = addToSectionTable(Group);
- SignatureSymbol->setGroupIndex(GroupIdx);
+ *GroupIdxEntry = addToSectionTable(Group);
Group->setAlignment(Align(4));
- GroupMap.resize(GroupIdx + 1);
- GroupMap[GroupIdx] = Groups.size();
+ GroupMap.resize(*GroupIdxEntry + 1);
+ GroupMap[*GroupIdxEntry] = Groups.size();
Groups.emplace_back(Group, SmallVector<unsigned>{});
}
}
@@ -1146,8 +1153,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
Relocations.push_back(RelSection);
}
- if (GroupIdx) {
- auto &Members = Groups[GroupMap[GroupIdx]];
+ if (GroupIdxEntry) {
+ auto &Members = Groups[GroupMap[*GroupIdxEntry]];
Members.second.push_back(Section.getLayoutOrder());
if (RelSection)
Members.second.push_back(RelSection->getLayoutOrder());
@@ -1180,7 +1187,7 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
}
// Compute symbol table information.
- computeSymbolTable(Asm);
+ computeSymbolTable(Asm, RevGroupMap);
for (MCSectionELF *RelSection : Relocations) {
// Remember the offset into the file for this section.
>From e940d6adced09129440a3e0b488e69cc3832705d Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 3 Jul 2024 08:26:03 +0000
Subject: [PATCH 6/7] use Ordinal instead of LayoutOrder
---
llvm/lib/MC/ELFObjectWriter.cpp | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 41e3284eeeae9..22179af534c02 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -683,7 +683,7 @@ void ELFWriter::computeSymbolTable(MCAssembler &Asm,
if (Mode == NonDwoOnly && isDwoSection(Section))
continue;
- MSD.SectionIndex = Section.getLayoutOrder();
+ MSD.SectionIndex = Section.getOrdinal();
assert(MSD.SectionIndex && "Invalid section index!");
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
HasLargeSectionIndex = true;
@@ -1034,7 +1034,7 @@ void ELFWriter::writeSection(uint32_t GroupSymbolIndex, uint64_t Offset,
sh_link = SymbolTableIndex;
assert(sh_link && ".symtab not found");
const MCSection *InfoSection = Section.getLinkedToSection();
- sh_info = InfoSection->getLayoutOrder();
+ sh_info = InfoSection->getOrdinal();
break;
}
@@ -1060,7 +1060,7 @@ void ELFWriter::writeSection(uint32_t GroupSymbolIndex, uint64_t Offset,
// undefined. Represent this with sh_link=0.
const MCSymbol *Sym = Section.getLinkedToSymbol();
if (Sym && Sym->isInSection())
- sh_link = Sym->getSection().getLayoutOrder();
+ sh_link = Sym->getSection().getOrdinal();
}
WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getName()),
@@ -1147,17 +1147,17 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm) {
}
}
- Section.setLayoutOrder(addToSectionTable(&Section));
+ Section.setOrdinal(addToSectionTable(&Section));
if (RelSection) {
- RelSection->setLayoutOrder(addToSectionTable(RelSection));
+ RelSection->setOrdinal(addToSectionTable(RelSection));
Relocations.push_back(RelSection);
}
if (GroupIdxEntry) {
auto &Members = Groups[GroupMap[*GroupIdxEntry]];
- Members.second.push_back(Section.getLayoutOrder());
+ Members.second.push_back(Section.getOrdinal());
if (RelSection)
- Members.second.push_back(RelSection->getLayoutOrder());
+ Members.second.push_back(RelSection->getOrdinal());
}
OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
>From 75a5d4489ebf58f8db3610ebd0f339d274ef4c0a Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 3 Jul 2024 09:38:46 +0000
Subject: [PATCH 7/7] clang-format
---
llvm/lib/MC/ELFObjectWriter.cpp | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 22179af534c02..5cba6eb15b5c9 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -176,8 +176,7 @@ struct ELFWriter {
///
/// \param Asm - The assembler.
/// \param RevGroupMap - Maps a signature symbol to the group section.
- void computeSymbolTable(MCAssembler &Asm,
- const RevGroupMapTy &RevGroupMap);
+ void computeSymbolTable(MCAssembler &Asm, const RevGroupMapTy &RevGroupMap);
void writeAddrsigSection();
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