[WIP][DebugInfo] Lazily parse debug_loclist offsets
Parsing DWARFv5 debug_loclist offsets when a CU is parsed is weighing
down memory usage of symbolizers that don't need to parse this data at
all. There's not much benefit to caching these anyway - since they are
O(1) lookup and reading once you know where the offset list starts (and
can do bounds checking with the offset list size too).
In general, I think it might be time to start paying down some of the
technical debt of loc/loclist/range/rnglist parsing to try to unify it a
bit more.
eg:
* Currently DWARFUnit has: RangeSection, RangeSectionBase, LocSection,
LocSectionBase, LocTable, RngListTable, LoclistTableHeader (be nice if
these were all wrapped up in two variables - one for loclists, one for
rnglists)
* rnglists and loclists are handled differently (see:
LoclistTableHeader, but no RnglistTableHeader)
* maybe all these types could be less stateful - lazily parse what they
need to, even reparsing rather than caching because it doesn't seem
too expensive, for instance. (though admittedly so long as it's
constantcost/overead per compilatiton that's probably adequate)
* Maybe implementing and using a DWARFDataExtractor that can be
sub-ranged (so we could slice it up to just the single contribution) -
though maybe that's not so useful because loc/ranges need to refer to
it by absolute, not contribution-relative mechanisms
Differential Revision: https://reviews.llvm.org/D86110
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index 3bcde8f..96ba579 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -255,7 +255,7 @@
break;
Offset = TableOffset + Length;
} else {
- Rnglists.dump(OS, LookupPooledAddress, DumpOpts);
+ Rnglists.dump(rnglistData, OS, LookupPooledAddress, DumpOpts);
}
}
}
@@ -316,7 +316,7 @@
return;
}
- Header.dump(OS, DumpOpts);
+ Header.dump(Data, OS, DumpOpts);
uint64_t EndOffset = Header.length() + Header.getHeaderOffset();
Data.setAddressSize(Header.getAddrSize());
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFListTable.cpp b/llvm/lib/DebugInfo/DWARF/DWARFListTable.cpp
index 2124a49..c876af1 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFListTable.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFListTable.cpp
@@ -71,12 +71,12 @@
") than there is space for",
SectionName.data(), HeaderOffset, HeaderData.OffsetEntryCount);
Data.setAddressSize(HeaderData.AddrSize);
- for (uint32_t I = 0; I < HeaderData.OffsetEntryCount; ++I)
- Offsets.push_back(Data.getRelocatedValue(OffsetByteSize, OffsetPtr));
+ *OffsetPtr += HeaderData.OffsetEntryCount * OffsetByteSize;
return Error::success();
}
-void DWARFListTableHeader::dump(raw_ostream &OS, DIDumpOptions DumpOpts) const {
+void DWARFListTableHeader::dump(DataExtractor Data, raw_ostream &OS,
+ DIDumpOptions DumpOpts) const {
if (DumpOpts.Verbose)
OS << format("0x%8.8" PRIx64 ": ", HeaderOffset);
int OffsetDumpWidth = 2 * dwarf::getDwarfOffsetByteSize(Format);
@@ -91,7 +91,8 @@
if (HeaderData.OffsetEntryCount > 0) {
OS << "offsets: [";
- for (const auto &Off : Offsets) {
+ for (uint32_t I = 0; I < HeaderData.OffsetEntryCount; ++I) {
+ auto Off = *getOffsetEntry(Data, I);
OS << format("\n0x%0*" PRIx64, OffsetDumpWidth, Off);
if (DumpOpts.Verbose)
OS << format(" => 0x%08" PRIx64,
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 0527f29..b871e6e 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -548,17 +548,13 @@
uint64_t HeaderSize = DWARFListTableHeader::getHeaderSize(Header.getFormat());
uint64_t Offset = getLocSectionBase();
- DWARFDataExtractor Data(Context.getDWARFObj(), *LocSection,
- isLittleEndian, getAddressByteSize());
+ const DWARFDataExtractor &Data = LocTable->getData();
if (Offset < HeaderSize)
return createStringError(errc::invalid_argument,
"did not detect a valid"
" list table with base = 0x%" PRIx64 "\n",
Offset);
Offset -= HeaderSize;
- if (auto *IndexEntry = Header.getIndexEntry())
- if (const auto *Contrib = IndexEntry->getContribution(DW_SECT_LOCLISTS))
- Offset += Contrib->Offset;
if (Error E = LoclistTableHeader->extract(Data, &Offset))
return createStringError(errc::invalid_argument,
"parsing a loclist table: " +
@@ -1009,3 +1005,13 @@
return DescOrError.takeError();
return *DescOrError;
}
+
+Optional<uint64_t> DWARFUnit::getRnglistOffset(uint32_t Index) {
+ if (!RngListTable)
+ return None;
+ DataExtractor RangesData(RangeSection->Data, isLittleEndian,
+ getAddressByteSize());
+ if (Optional<uint64_t> Off = RngListTable->getOffsetEntry(RangesData, Index))
+ return *Off + RangeSectionBase;
+ return None;
+}