commit 1ccde533425a4ba9d379510206ad680ff9702129
Author: Fangrui Song <maskray@google.com>
Date:   Tue Apr 28 18:53:12 2020 -0700

    [ELF] --gdb-index: support .debug_loclists
    
    --gdb-index currently crashes when reading a translation unit with
    DWARF v5 .debug_loclists . Call stack:
    
    ```
    SyntheticSections.cpp GdbIndexSection::create
    SyntheticSections.cpp readAddressAreas
    DWARFUnit.cpp DWARFUnit::tryExtractDIEsIfNeeded
    DWARFListTable.cpp DWARFListTableHeader::extract
    ...
    DWARFDataExtractor.cpp DWARFDataExtractor::getRelocatedValue
    lld/ELF/DWARF.cpp LLDDwarfObj<ELFT>::find (sec.sec is nullptr)
    ...
    
    ```
    
    This patch adds support for .debug_loclists to make `DWARFUnit::tryExtractDIEsIfNeeded` happy.
    Building --gdb-index does not need .debug_loclists
    
    Reviewed By: dblaikie, grimar
    
    Differential Revision: https://reviews.llvm.org/D79061

diff --git a/lld/ELF/DWARF.cpp b/lld/ELF/DWARF.cpp
index bf4fff76c31..f1587d93e53 100644
--- a/lld/ELF/DWARF.cpp
+++ b/lld/ELF/DWARF.cpp
@@ -36,6 +36,7 @@ template <class ELFT> LLDDwarfObj<ELFT>::LLDDwarfObj(ObjFile<ELFT> *obj) {
                 .Case(".debug_gnu_pubnames", &gnuPubnamesSection)
                 .Case(".debug_gnu_pubtypes", &gnuPubtypesSection)
                 .Case(".debug_info", &infoSection)
+                .Case(".debug_loclists", &loclistsSection)
                 .Case(".debug_ranges", &rangesSection)
                 .Case(".debug_rnglists", &rnglistsSection)
                 .Case(".debug_str_offsets", &strOffsetsSection)
diff --git a/lld/ELF/DWARF.h b/lld/ELF/DWARF.h
index 51ec9092f17..8609e35faf9 100644
--- a/lld/ELF/DWARF.h
+++ b/lld/ELF/DWARF.h
@@ -32,6 +32,10 @@ public:
     f(infoSection);
   }
 
+  const llvm::DWARFSection &getLoclistsSection() const override {
+    return loclistsSection;
+  }
+
   const llvm::DWARFSection &getRangesSection() const override {
     return rangesSection;
   }
@@ -81,6 +85,7 @@ private:
   LLDDWARFSection gnuPubnamesSection;
   LLDDWARFSection gnuPubtypesSection;
   LLDDWARFSection infoSection;
+  LLDDWARFSection loclistsSection;
   LLDDWARFSection rangesSection;
   LLDDWARFSection rnglistsSection;
   LLDDWARFSection strOffsetsSection;
diff --git a/lld/test/ELF/gdb-index-loclists.s b/lld/test/ELF/gdb-index-loclists.s
new file mode 100644
index 00000000000..e3769b69537
--- /dev/null
+++ b/lld/test/ELF/gdb-index-loclists.s
@@ -0,0 +1,37 @@
+# REQUIRES: x86
+## Regression test that we don't crash on DWARF v5 .debug_loclists
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: ld.lld --gdb-index %t.o -o /dev/null
+
+.section .debug_abbrev,"",@progbits
+  .byte 1            # Abbreviation Code
+  .byte 17           # DW_TAG_compile_unit
+  .byte 0            # DW_CHILDREN_no
+  .ascii "\214\001"  # DW_AT_loclists_base
+  .byte 23           # DW_FORM_sec_offset
+  .byte 0            # EOM(1)
+  .byte 0            # EOM(2)
+  .byte 0
+
+.section .debug_info,"",@progbits
+.Lcu_begin0:
+  .long .Lcu_end0-.Lcu_begin0-4  # Length of Unit
+  .short 5                       # DWARF version number
+  .byte  1                       # DWARF Unit Type
+  .byte  8                       # Address Size
+  .long  0                       # Offset Into Abbrev. Section
+  .byte  1                       # Abbrev [1] DW_TAG_compile_unit
+  .long  .Lloclists_table_base0  # DW_AT_loclists_base
+.Lcu_end0:
+
+.section .debug_loclists,"",@progbits
+  .long .Ldebug_loclist_table_end0-.Ldebug_loclist_table_start0 # Length
+.Ldebug_loclist_table_start0:
+  .short 5                # Version
+  .byte  8                # Address size
+  .byte  0                # Segment selector size
+  .long  0                # Offset entry count
+.Lloclists_table_base0:
+  .byte  0                # DW_LLE_end_of_list
+.Ldebug_loclist_table_end0: