[DWARF] Support for loclist.dwo section in llvm and llvm-dwarfdump.

This patch adds support for debug_loclists.dwo section in llvm and llvm-dwarfdump.
Also Fixes PR43622, PR43623.

Reviewers: dblaikie, probinson, labath, aprantl, jini.susan.george

https://reviews.llvm.org/D69462

2 files changed, 37 insertions, 8 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index f7b3fb495f9..012bab35460 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -404,6 +404,14 @@ void DWARFContext::dump(
     dumpLoclistsSection(OS, LLDumpOpts, Data, getRegisterInfo(), *Off);
   }
   if (const auto *Off =
+          shouldDump(ExplicitDWO, ".debug_loclists.dwo", DIDT_ID_DebugLoclists,
+                     DObj->getLoclistsDWOSection().Data)) {
+    DWARFDataExtractor Data(*DObj, DObj->getLoclistsDWOSection(),
+                            isLittleEndian(), 0);
+    dumpLoclistsSection(OS, LLDumpOpts, Data, getRegisterInfo(), *Off);
+  }
+
+  if (const auto *Off =
           shouldDump(ExplicitDWO, ".debug_loc.dwo", DIDT_ID_DebugLoc,
                      DObj->getLocDWOSection().Data)) {
     DWARFDataExtractor Data(*DObj, DObj->getLocDWOSection(), isLittleEndian(),
@@ -1385,6 +1393,7 @@ class DWARFObjInMemory final : public DWARFObject {
 
   DWARFSectionMap LocSection;
   DWARFSectionMap LoclistsSection;
+  DWARFSectionMap LoclistsDWOSection;
   DWARFSectionMap LineSection;
   DWARFSectionMap RangesSection;
   DWARFSectionMap RnglistsSection;
@@ -1411,6 +1420,7 @@ class DWARFObjInMemory final : public DWARFObject {
     return StringSwitch<DWARFSectionMap *>(Name)
         .Case("debug_loc", &LocSection)
         .Case("debug_loclists", &LoclistsSection)
+        .Case("debug_loclists.dwo", &LoclistsDWOSection)
         .Case("debug_line", &LineSection)
         .Case("debug_frame", &FrameSection)
         .Case("eh_frame", &EHFrameSection)
@@ -1741,6 +1751,9 @@ public:
   const DWARFSection &getRnglistsDWOSection() const override {
     return RnglistsDWOSection;
   }
+  const DWARFSection &getLoclistsDWOSection() const override {
+    return LoclistsDWOSection;
+  }
   const DWARFSection &getAddrSection() const override { return AddrSection; }
   StringRef getCUIndexSection() const override { return CUIndexSection; }
   StringRef getGdbIndexSection() const override { return GdbIndexSection; }
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index e5d33e13644..b662e88816f 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -186,9 +186,16 @@ DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
     if (auto *IndexEntry = Header.getIndexEntry())
       if (const auto *C = IndexEntry->getOffset(DW_SECT_LOC))
         Data = Data.substr(C->Offset, C->Length);
-    LocTable = std::make_unique<DWARFDebugLoclists>(
-        DWARFDataExtractor(Data, isLittleEndian, getAddressByteSize()),
-        Header.getVersion());
+
+    DWARFDataExtractor DWARFData =
+        Header.getVersion() >= 5
+            ? DWARFDataExtractor(Context.getDWARFObj(),
+                                 Context.getDWARFObj().getLoclistsDWOSection(),
+                                 isLittleEndian, getAddressByteSize())
+            : DWARFDataExtractor(Data, isLittleEndian, getAddressByteSize());
+    LocTable =
+        std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
+
   } else if (Header.getVersion() >= 5) {
     LocTable = std::make_unique<DWARFDebugLoclists>(
         DWARFDataExtractor(Context.getDWARFObj(),
@@ -502,14 +509,23 @@ Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
         RangeSectionBase = RngListTable->getHeaderSize();
     }
 
-    // FIXME: add loclists.dwo support
-    setLocSection(&Context.getDWARFObj().getLoclistsSection(),
-                  toSectionOffset(UnitDie.find(DW_AT_loclists_base), 0));
+    // In a split dwarf unit, there is no DW_AT_loclists_base attribute.
+    // Setting LocSectionBase to point past the table header.
+    if (IsDWO)
+      setLocSection(&Context.getDWARFObj().getLoclistsDWOSection(),
+                    DWARFListTableHeader::getHeaderSize(Header.getFormat()));
+    else
+      setLocSection(&Context.getDWARFObj().getLoclistsSection(),
+                    toSectionOffset(UnitDie.find(DW_AT_loclists_base), 0));
 
     if (LocSection->Data.size()) {
-      LoclistTableHeader.emplace(".debug_loclists", "locations");
-      uint64_t Offset = LocSectionBase;
+      if (IsDWO)
+        LoclistTableHeader.emplace(".debug_loclists.dwo", "locations");
+      else
+        LoclistTableHeader.emplace(".debug_loclists", "locations");
+
       uint64_t HeaderSize = DWARFListTableHeader::getHeaderSize(Header.getFormat());
+      uint64_t Offset = getLocSectionBase();
       DWARFDataExtractor Data(Context.getDWARFObj(), *LocSection,
                               isLittleEndian, getAddressByteSize());
       if (Offset < HeaderSize)