[DebugInfo] Fix reading range lists of v5 units in DWP.

[ikudrin]

Summary

In package files, the base offset provided by index sections should be used to find the contribution of a unit. The patch adds that base offset when reading range list tables.

[dblaikie]

Looks good - thanks!

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

if (!StringOffsetOrError)
                                    toString(StringOffsetOrError.takeError()));
 
     StringOffsetsTableContribution = *StringOffsetOrError;
   }
 
   // DWARF v5 uses the .debug_rnglists and .debug_rnglists.dwo sections to
   // describe address ranges.
   if (getVersion() >= 5) {
-    if (IsDWO)
-      setRangesSection(&Context.getDWARFObj().getRnglistsDWOSection(), 0);
-    else
+    // In case of DWP, the base offset from the index has to be added.
+    uint64_t ContributionBaseOffset = 0;
+    if (IsDWO) {
+      if (auto *IndexEntry = Header.getIndexEntry())
+        if (auto *Contrib = IndexEntry->getContribution(DW_SECT_RNGLISTS))
+          ContributionBaseOffset = Contrib->Offset;
+      setRangesSection(
+          &Context.getDWARFObj().getRnglistsDWOSection(),
+          ContributionBaseOffset +
+              DWARFListTableHeader::getHeaderSize(Header.getFormat()));
+    } else
       setRangesSection(&Context.getDWARFObj().getRnglistsSection(),
                        toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0));
     if (RangeSection->Data.size()) {
       // Parse the range list table header. Individual range lists are
       // extracted lazily.
       DWARFDataExtractor RangesDA(Context.getDWARFObj(), *RangeSection,
                                   isLittleEndian, 0);
       auto TableOrError = parseListTableHeader<DWARFDebugRnglistTable>(
           RangesDA, RangeSectionBase, Header.getFormat());
       if (!TableOrError)
         return createStringError(errc::invalid_argument,
                                  "parsing a range list table: " +
                                      toString(TableOrError.takeError()));
 
       RngListTable = TableOrError.get();
 
       // In a split dwarf unit, there is no DW_AT_rnglists_base attribute.
       // Adjust RangeSectionBase to point past the table header.
       if (IsDWO && RngListTable)
-        RangeSectionBase = RngListTable->getHeaderSize();
+        RangeSectionBase =
+            ContributionBaseOffset + RngListTable->getHeaderSize();
     }
 
     // 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

llvm/test/DebugInfo/X86/dwp-v5-rnglists.s

+## The test checks that ranges for compile units in package files are read
+## correctly, i.e. the base offset in the index section is taken into account.
+
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
+# RUN:   llvm-dwarfdump -v -debug-info -debug-rnglists - | \
+# RUN:   FileCheck %s
+
+# CHECK:      .debug_info.dwo contents:
+# CHECK:      Compile Unit:
+# CHECK:      DW_TAG_compile_unit [1]
+# CHECK-NEXT:   DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000022
+# CHECK-NEXT:     [0x00000005, 0x0000000f))
+
+# CHECK:      .debug_rnglists.dwo contents:
+# CHECK:      0x00000000: range list header:
+# CHECK:      0x0000000d: range list header:
+# CHECK-NEXT: offsets: [
+# CHECK-NEXT: 0x00000008 => 0x00000021
+# CHECK-NEXT: 0x00000009 => 0x00000022
+# CHECK-NEXT: ]
+# CHECK-NEXT: ranges:
+# CHECK-NEXT: 0x00000021: [DW_RLE_end_of_list]
+# CHECK-NEXT: 0x00000022: [DW_RLE_offset_pair]:  0x00000005, 0x0000000f => [0x00000005, 0x0000000f)
+# CHECK-NEXT: 0x00000025: [DW_RLE_end_of_list]
+
+    .section .debug_abbrev.dwo, "e", @progbits
+.LAbbrev:
+    .byte 0x01                          # Abbrev code
+    .byte 0x11                          # DW_TAG_compile_unit
+    .byte 0x00                          # DW_CHILDREN_no
+    .byte 0x55                          # DW_AT_ranges
+    .byte 0x23                          # DW_FORM_rnglistx
+    .byte 0x00                          # EOM(1)
+    .byte 0x00                          # EOM(2)
+    .byte 0x00                          # EOM(3)
+.LAbbrevEnd:
+    
+    .section .debug_info.dwo, "e", @progbits
+.LCU:
+    .long .LCUEnd-.LCUVersion           # Length
+.LCUVersion:
+    .short 5                            # Version
+    .byte 5                             # DW_UT_split_compile
+    .byte 4                             # Address Size (in bytes)
+    .long 0                             # Offset Into Abbrev Section
+    .quad 0x1100001122222222            # DWO id
+    .uleb128 1                          # Abbrev [1] DW_TAG_compile_unit
+    .uleb128 1                          # DW_AT_ranges (DW_FORM_rnglistx)
+.LCUEnd:
+
+    .section .debug_rnglists.dwo,"e",@progbits
+.LRLT0:
+    .long .LRLT0End-.LRLT0Version       # Length
+.LRLT0Version:
+    .short 5
+    .byte 4
+    .byte 0
+    .long 0
+.LRLT0List0:
+    .byte 0                             # DW_RLE_end_of_list
+.LRLT0End:
+
+.LRLT1:
+    .long .LRLT1End-.LRLT1Version
+.LRLT1Version:
+    .short 5                            # Version
+    .byte 4                             # Address size
+    .byte 0                             # Segment selector size
+    .long 2                             # Offset entry count
+.LRLT1Base:
+    .long .LRLT1List0-.LRLT1Base
+    .long .LRLT1List1-.LRLT1Base
+.LRLT1List0:
+    .byte 0                             # DW_RLE_end_of_list
+.LRLT1List1:
+    .byte 4                             # DW_RLE_offset_pair
+    .uleb128 5                          # Starting offset
+    .uleb128 15                         # Ending offset
+    .byte 0                             # DW_RLE_end_of_list
+.LRLT1End:
+
+    .section .debug_cu_index, "", @progbits
+## Header:
+    .short 5                            # Version
+    .space 2                            # Padding
+    .long 3                             # Section count
+    .long 1                             # Unit count
+    .long 2                             # Slot count
+## Hash Table of Signatures:
+    .quad 0x1100001122222222
+    .quad 0
+## Parallel Table of Indexes:
+    .long 1
+    .long 0
+## Table of Section Offsets:
+## Row 0:
+    .long 1                             # DW_SECT_INFO
+    .long 3                             # DW_SECT_ABBREV
+    .long 8                             # DW_SECT_RNGLISTS
+## Row 1:
+    .long 0                             # Offset in .debug_info.dwo
+    .long 0                             # Offset in .debug_abbrev.dwo
+    .long .LRLT1-.debug_rnglists.dwo    # Offset in .debug_rnglists.dwo
+## Table of Section Sizes:
+    .long .LCUEnd-.LCU                  # Size in .debug_info.dwo
+    .long .LAbbrevEnd-.LAbbrev          # Size in .debug_abbrev.dwo
+    .long .LRLT1End-.LRLT1              # Size in .debug_rnglists.dwo