[DWARF][BOLT] Fix handling of converting range accesss from ofset to index.

[ayermolo]

Summary

Wasn't handling correctly creating DW_AT_rnglists_base in UnitDie when
converting access pattern for DW_AT_ranges from offset to index for DWARF5.

[rafauler]

LGTM

bolt/lib/Rewrite/DWARFRewriter.cpp

865

[ayermolo]

nit

bolt/lib/Rewrite/DWARFRewriter.cpp

if (Optional<AttrInfo> AttrVal =
     if (!RangesBase) {
       if (LowPCAttrInfo &&
           LowPCAttrInfo->V.getForm() != dwarf::DW_FORM_GNU_addr_index &&
           LowPCAttrInfo->V.getForm() != dwarf::DW_FORM_addrx)
         DebugInfoPatcher.addLE64Patch(LowPCAttrInfo->Offset, LowPCToUse);
       return;
     }
 
-    // Convert DW_AT_low_pc into DW_AT_GNU_ranges_base.
-    if (!LowPCAttrInfo) {
-      errs() << "BOLT-ERROR: skeleton CU at 0x"
-             << Twine::utohexstr(DIE.getOffset())
-             << " does not have DW_AT_GNU_ranges_base or DW_AT_low_pc to"
-                " convert to update ranges base\n";
+    if (DIE.getOffset() != DIE.getDwarfUnit()->getUnitDIE().getOffset())
       return;
-    }
 
+    // If we are at this point we are in the CU/Skeleton CU, and
+    // DW_AT_GNU_ranges_base or DW_AT_rnglists_base doesn't exist.
+    if (DIE.getDwarfUnit()->getVersion() >= 5) {
+      AbbrevWriter.addAttribute(*DIE.getDwarfUnit(), AbbreviationDecl,
+                                dwarf::DW_AT_rnglists_base,
+                                dwarf::DW_FORM_sec_offset);
+    } else {
       AbbrevWriter.addAttribute(*DIE.getDwarfUnit(), AbbreviationDecl,
                                 dwarf::DW_AT_GNU_ranges_base,
                                 dwarf::DW_FORM_sec_offset);
+    }
     reinterpret_cast<DebugInfoBinaryPatcher &>(DebugInfoPatcher)
         .insertNewEntry(DIE, *RangesBase);
 
     return;
   }
 
   // Case 2: The object has both DW_AT_low_pc and DW_AT_high_pc emitted back
   // to back. Replace with new attributes and patch the DIE.

bolt/test/X86/dwarf5-rangeoffset-to-rangeindex.s

 # POSTCHECK: Addrs: [
 # POSTCHECK-NEXT: 0x[[#%.16x,ADDR:]]
 # POSTCHECK-NEXT: 0x[[#%.16x,ADDR1:]]
 # POSTCHECK: version = 0x0005
 # POSTCHECK: DW_AT_ranges [DW_FORM_rnglistx]
 # POSTCHECK-SAME: (indexed (0x0) rangelist = 0x00000018
 # POSTCHECK-NEXT: [0x[[#ADDR]], 0x[[#ADDR + 11]]
 # POSTCHECK-NEXT: [0x[[#ADDR1]], 0x[[#ADDR1 + 11]]
+# POSTCHECK-NEXT:  DW_AT_low_pc [DW_FORM_addr]
+# POSTCHECK-NEXT:  DW_AT_stmt_list [DW_FORM_sec_offset]
+# POSTCHECK-NEXT:  DW_AT_rnglists_base [DW_FORM_sec_offset]  (0x0000000c)
+# POSTCHECK-NEXT:  DW_AT_addr_base [DW_FORM_sec_offset]  (0x00000008)
+
 
 # int foo() {
 #   return 3;
 # }
 #
 # int main() {
 #   return foo();
 # }