[DWARFDebugRnglists] Add a callback-based version of the getAbsoluteRanges function

[labath]

Summary

The dump() function already accepts a callback. This makes
getAbsoluteRanges do the same. The existing DWARFUnit overload is
implemented on top of the new function.

This enables usage of the debug_rnglists parser from within lldb (which
has it's own dwarf parser).

[dblaikie]

Sounds good

llvm/include/llvm/DebugInfo/DWARF/DWARFDebugRnglists.h

struct RangeListEntry : public DWARFListEntryBase {
   bool isSentinel() const { return EntryKind == dwarf::DW_RLE_end_of_list; }
 };
 
 /// A class representing a single rangelist.
 class DWARFDebugRnglist : public DWARFListType<RangeListEntry> {
 public:
   /// Build a DWARFAddressRangesVector from a rangelist.
   DWARFAddressRangesVector
+  getAbsoluteRanges(Optional<object::SectionedAddress> BaseAddr,
+                    function_ref<Optional<object::SectionedAddress>(uint32_t)>
+                        LookupPooledAddress) const;
+
+  /// Build a DWARFAddressRangesVector from a rangelist.
+  DWARFAddressRangesVector
   getAbsoluteRanges(llvm::Optional<object::SectionedAddress> BaseAddr,
                     DWARFUnit &U) const;
 };
 
 class DWARFDebugRnglistTable : public DWARFListTableBase<DWARFDebugRnglist> {
 public:
   DWARFDebugRnglistTable()
       : DWARFListTableBase(/* SectionName    = */ ".debug_rnglists",
                            /* HeaderString   = */ "ranges:",
                            /* ListTypeString = */ "range") {}
 };
 
 } // end namespace llvm
 
 #endif // LLVM_DEBUGINFO_DWARFDEBUGRNGLISTS_H

llvm/lib/DebugInfo/DWARF/DWARFDebugRnglists.cpp

Error RangeListEntry::extract(DWARFDataExtractor Data, uint64_t End,
   }
 
   EntryKind = Encoding;
   return Error::success();
 }
 
 DWARFAddressRangesVector DWARFDebugRnglist::getAbsoluteRanges(
     llvm::Optional<object::SectionedAddress> BaseAddr, DWARFUnit &U) const {
+  return getAbsoluteRanges(BaseAddr, [&](uint32_t Index) {
+    return U.getAddrOffsetSectionItem(Index);
+  });
+}
+
+DWARFAddressRangesVector DWARFDebugRnglist::getAbsoluteRanges(
+    Optional<object::SectionedAddress> BaseAddr,
+    function_ref<Optional<object::SectionedAddress>(uint32_t)>
+        LookupPooledAddress) const {
   DWARFAddressRangesVector Res;
   for (const RangeListEntry &RLE : Entries) {
     if (RLE.EntryKind == dwarf::DW_RLE_end_of_list)
       break;
     if (RLE.EntryKind == dwarf::DW_RLE_base_addressx) {
-      BaseAddr = U.getAddrOffsetSectionItem(RLE.Value0);
+      BaseAddr = LookupPooledAddress(RLE.Value0);
       if (!BaseAddr)
         BaseAddr = {RLE.Value0, -1ULL};
       continue;
     }
     if (RLE.EntryKind == dwarf::DW_RLE_base_address) {
       BaseAddr = {RLE.Value0, RLE.SectionIndex};
       continue;
     }
case dwarf::DW_RLE_start_end:
       E.LowPC = RLE.Value0;
       E.HighPC = RLE.Value1;
       break;
     case dwarf::DW_RLE_start_length:
       E.LowPC = RLE.Value0;
       E.HighPC = E.LowPC + RLE.Value1;
       break;
     case dwarf::DW_RLE_startx_length: {
-      auto Start = U.getAddrOffsetSectionItem(RLE.Value0);
+      auto Start = LookupPooledAddress(RLE.Value0);
       if (!Start)
         Start = {0, -1ULL};
       E.SectionIndex = Start->SectionIndex;
       E.LowPC = Start->Address;
       E.HighPC = E.LowPC + RLE.Value1;
       break;
     }
     default: