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[LLVM][DebugInfo] Refactor some code for easier sharing. (#82153)
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Refactor the code that calculates the offsets for the various pieces of
the DWARF .debug_names index section, to make it easier to share the
code with other tools, such as LLD.
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@cmtice
cmtice committed Feb 22, 2024
1 parent 0107c88 commit 43f1fa9
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Showing 2 changed files with 65 additions and 34 deletions.
26 changes: 19 additions & 7 deletions llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -562,6 +562,17 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
uint64_t getEntryOffset() const { return EntryOffset; }
};

/// Offsets for the start of various important tables from the start of the
/// section.
struct DWARFDebugNamesOffsets {
uint64_t CUsBase;
uint64_t BucketsBase;
uint64_t HashesBase;
uint64_t StringOffsetsBase;
uint64_t EntryOffsetsBase;
uint64_t EntriesBase;
};

/// Represents a single accelerator table within the DWARF v5 .debug_names
/// section.
class NameIndex {
Expand All @@ -572,12 +583,7 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
// Base of the whole unit and of various important tables, as offsets from
// the start of the section.
uint64_t Base;
uint64_t CUsBase;
uint64_t BucketsBase;
uint64_t HashesBase;
uint64_t StringOffsetsBase;
uint64_t EntryOffsetsBase;
uint64_t EntriesBase;
DWARFDebugNamesOffsets Offsets;

void dumpCUs(ScopedPrinter &W) const;
void dumpLocalTUs(ScopedPrinter &W) const;
Expand Down Expand Up @@ -638,7 +644,7 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
/// Returns the Entry at the relative `Offset` from the start of the Entry
/// pool.
Expected<Entry> getEntryAtRelativeOffset(uint64_t Offset) const {
auto OffsetFromSection = Offset + this->EntriesBase;
auto OffsetFromSection = Offset + this->Offsets.EntriesBase;
return getEntry(&OffsetFromSection);
}

Expand Down Expand Up @@ -793,6 +799,12 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
const NameIndex *getCUNameIndex(uint64_t CUOffset);
};

/// Calculates the starting offsets for various sections within the
/// .debug_names section.
void findDebugNamesOffsets(DWARFDebugNames::DWARFDebugNamesOffsets &Offsets,
uint64_t HdrSize, const dwarf::DwarfFormat Format,
const DWARFDebugNames::Header &Hdr);

/// If `Name` is the name of a templated function that includes template
/// parameters, returns a substring of `Name` containing no template
/// parameters.
Expand Down
73 changes: 46 additions & 27 deletions llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -510,7 +510,7 @@ DWARFDebugNames::Abbrev DWARFDebugNames::AbbrevMapInfo::getTombstoneKey() {

Expected<DWARFDebugNames::AttributeEncoding>
DWARFDebugNames::NameIndex::extractAttributeEncoding(uint64_t *Offset) {
if (*Offset >= EntriesBase) {
if (*Offset >= Offsets.EntriesBase) {
return createStringError(errc::illegal_byte_sequence,
"Incorrectly terminated abbreviation table.");
}
Expand All @@ -536,7 +536,7 @@ DWARFDebugNames::NameIndex::extractAttributeEncodings(uint64_t *Offset) {

Expected<DWARFDebugNames::Abbrev>
DWARFDebugNames::NameIndex::extractAbbrev(uint64_t *Offset) {
if (*Offset >= EntriesBase) {
if (*Offset >= Offsets.EntriesBase) {
return createStringError(errc::illegal_byte_sequence,
"Incorrectly terminated abbreviation table.");
}
Expand All @@ -552,32 +552,50 @@ DWARFDebugNames::NameIndex::extractAbbrev(uint64_t *Offset) {
return Abbrev(Code, dwarf::Tag(Tag), AbbrevOffset, std::move(*AttrEncOr));
}

void llvm::findDebugNamesOffsets(
DWARFDebugNames::DWARFDebugNamesOffsets &Offsets, uint64_t HdrSize,
dwarf::DwarfFormat Format, const DWARFDebugNames::Header &Hdr) {
uint32_t DwarfSize = (Format == llvm::dwarf::DwarfFormat::DWARF64) ? 8 : 4;
uint64_t Offset = HdrSize;
Offsets.CUsBase = Offset;
Offset += Hdr.CompUnitCount * DwarfSize;
Offset += Hdr.LocalTypeUnitCount * DwarfSize;
Offset += Hdr.ForeignTypeUnitCount * 8;

Offsets.BucketsBase = Offset;
Offset += Hdr.BucketCount * 4;

Offsets.HashesBase = Offset;
if (Hdr.BucketCount > 0)
Offset += Hdr.NameCount * 4;

Offsets.StringOffsetsBase = Offset;
Offset += Hdr.NameCount * DwarfSize;

Offsets.EntryOffsetsBase = Offset;
Offset += Hdr.NameCount * DwarfSize;

Offset += Hdr.AbbrevTableSize;
Offsets.EntriesBase = Offset;
}

Error DWARFDebugNames::NameIndex::extract() {
const DWARFDataExtractor &AS = Section.AccelSection;
uint64_t Offset = Base;
if (Error E = Hdr.extract(AS, &Offset))
uint64_t hdrSize = Base;
if (Error E = Hdr.extract(AS, &hdrSize))
return E;

const unsigned SectionOffsetSize = dwarf::getDwarfOffsetByteSize(Hdr.Format);
CUsBase = Offset;
Offset += Hdr.CompUnitCount * SectionOffsetSize;
Offset += Hdr.LocalTypeUnitCount * SectionOffsetSize;
Offset += Hdr.ForeignTypeUnitCount * 8;
BucketsBase = Offset;
Offset += Hdr.BucketCount * 4;
HashesBase = Offset;
if (Hdr.BucketCount > 0)
Offset += Hdr.NameCount * 4;
StringOffsetsBase = Offset;
Offset += Hdr.NameCount * SectionOffsetSize;
EntryOffsetsBase = Offset;
Offset += Hdr.NameCount * SectionOffsetSize;
findDebugNamesOffsets(Offsets, hdrSize, Hdr.Format, Hdr);

uint64_t Offset =
Offsets.EntryOffsetsBase + (Hdr.NameCount * SectionOffsetSize);

if (!AS.isValidOffsetForDataOfSize(Offset, Hdr.AbbrevTableSize))
return createStringError(errc::illegal_byte_sequence,
"Section too small: cannot read abbreviations.");

EntriesBase = Offset + Hdr.AbbrevTableSize;
Offsets.EntriesBase = Offset + Hdr.AbbrevTableSize;

for (;;) {
auto AbbrevOr = extractAbbrev(&Offset);
Expand Down Expand Up @@ -679,7 +697,7 @@ void DWARFDebugNames::Entry::dumpParentIdx(
return;
}

auto AbsoluteOffset = NameIdx->EntriesBase + FormValue.getRawUValue();
auto AbsoluteOffset = NameIdx->Offsets.EntriesBase + FormValue.getRawUValue();
W.getOStream() << "Entry @ 0x" + Twine::utohexstr(AbsoluteOffset);
}

Expand Down Expand Up @@ -708,22 +726,23 @@ std::error_code DWARFDebugNames::SentinelError::convertToErrorCode() const {
uint64_t DWARFDebugNames::NameIndex::getCUOffset(uint32_t CU) const {
assert(CU < Hdr.CompUnitCount);
const unsigned SectionOffsetSize = dwarf::getDwarfOffsetByteSize(Hdr.Format);
uint64_t Offset = CUsBase + SectionOffsetSize * CU;
uint64_t Offset = Offsets.CUsBase + SectionOffsetSize * CU;
return Section.AccelSection.getRelocatedValue(SectionOffsetSize, &Offset);
}

uint64_t DWARFDebugNames::NameIndex::getLocalTUOffset(uint32_t TU) const {
assert(TU < Hdr.LocalTypeUnitCount);
const unsigned SectionOffsetSize = dwarf::getDwarfOffsetByteSize(Hdr.Format);
uint64_t Offset = CUsBase + SectionOffsetSize * (Hdr.CompUnitCount + TU);
uint64_t Offset =
Offsets.CUsBase + SectionOffsetSize * (Hdr.CompUnitCount + TU);
return Section.AccelSection.getRelocatedValue(SectionOffsetSize, &Offset);
}

uint64_t DWARFDebugNames::NameIndex::getForeignTUSignature(uint32_t TU) const {
assert(TU < Hdr.ForeignTypeUnitCount);
const unsigned SectionOffsetSize = dwarf::getDwarfOffsetByteSize(Hdr.Format);
uint64_t Offset =
CUsBase +
Offsets.CUsBase +
SectionOffsetSize * (Hdr.CompUnitCount + Hdr.LocalTypeUnitCount) + 8 * TU;
return Section.AccelSection.getU64(&Offset);
}
Expand Down Expand Up @@ -759,28 +778,28 @@ DWARFDebugNames::NameIndex::getNameTableEntry(uint32_t Index) const {
assert(0 < Index && Index <= Hdr.NameCount);
const unsigned SectionOffsetSize = dwarf::getDwarfOffsetByteSize(Hdr.Format);
uint64_t StringOffsetOffset =
StringOffsetsBase + SectionOffsetSize * (Index - 1);
Offsets.StringOffsetsBase + SectionOffsetSize * (Index - 1);
uint64_t EntryOffsetOffset =
EntryOffsetsBase + SectionOffsetSize * (Index - 1);
Offsets.EntryOffsetsBase + SectionOffsetSize * (Index - 1);
const DWARFDataExtractor &AS = Section.AccelSection;

uint64_t StringOffset =
AS.getRelocatedValue(SectionOffsetSize, &StringOffsetOffset);
uint64_t EntryOffset = AS.getUnsigned(&EntryOffsetOffset, SectionOffsetSize);
EntryOffset += EntriesBase;
EntryOffset += Offsets.EntriesBase;
return {Section.StringSection, Index, StringOffset, EntryOffset};
}

uint32_t
DWARFDebugNames::NameIndex::getBucketArrayEntry(uint32_t Bucket) const {
assert(Bucket < Hdr.BucketCount);
uint64_t BucketOffset = BucketsBase + 4 * Bucket;
uint64_t BucketOffset = Offsets.BucketsBase + 4 * Bucket;
return Section.AccelSection.getU32(&BucketOffset);
}

uint32_t DWARFDebugNames::NameIndex::getHashArrayEntry(uint32_t Index) const {
assert(0 < Index && Index <= Hdr.NameCount);
uint64_t HashOffset = HashesBase + 4 * (Index - 1);
uint64_t HashOffset = Offsets.HashesBase + 4 * (Index - 1);
return Section.AccelSection.getU32(&HashOffset);
}

Expand Down

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