[DebugInfo] Print the actual value of an unknown section identifier.

[ikudrin]

Summary

This is a follow-up for D75609. As @dblaikie suggested, it prints the actual number for an unknown section identifier when dumping unit index sections.

[dblaikie]

Looks good - thanks!

llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp

121

Might be simpler to write this as return "";

[jhenderson]

LGTM too.

[ikudrin]

llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp

121

I believe I would better stick with StringRef(). This is the same way as other stringify functions are written, in particular, in Dwarf.cpp, and, as I checked, the compiler generates a bit better code with the default constructor of StringRef.

llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp

switch (DS) {
     CASE(TYPES);
     CASE(ABBREV);
     CASE(LINE);
     CASE(LOC);
     CASE(STR_OFFSETS);
     CASE(MACINFO);
     CASE(MACRO);
   }
-  return "<unknown>";
+  return StringRef();
 }
 
 void DWARFUnitIndex::dump(raw_ostream &OS) const {
   if (!*this)
     return;
 
   Header.dump(OS);
   OS << "Index Signature         ";
-  for (unsigned i = 0; i != Header.NumColumns; ++i)
-    OS << ' ' << left_justify(getColumnHeader(ColumnKinds[i]), 24);
+  for (unsigned i = 0; i != Header.NumColumns; ++i) {
+    DWARFSectionKind Kind = ColumnKinds[i];
+    StringRef Name = getColumnHeader(Kind);
+    if (!Name.empty())
+      OS << ' ' << left_justify(Name, 24);
+    else
+      OS << format(" Unknown: %-15u", static_cast<unsigned>(Kind));
+  }
   OS << "\n----- ------------------";
   for (unsigned i = 0; i != Header.NumColumns; ++i)
     OS << " ------------------------";
   OS << '\n';
   for (unsigned i = 0; i != Header.NumBuckets; ++i) {
     auto &Row = Rows[i];
     if (auto *Contribs = Row.Contributions.get()) {
       OS << format("%5u 0x%016" PRIx64 " ", i + 1, Row.Signature);

llvm/test/DebugInfo/X86/debug-cu-index-unknown-section.s

 # RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
 # RUN:   llvm-dwarfdump -debug-cu-index - | \
-# RUN:   FileCheck %s
+# RUN:   FileCheck %s --strict-whitespace
 
 # CHECK:      .debug_cu_index contents:
 # CHECK-NEXT: version = 2 slots = 2
 # CHECK-EMPTY:
-# CHECK-NEXT: Index Signature          INFO                     <unknown>
+# CHECK-NEXT: Index Signature          Unknown: 9               INFO
 # CHECK-NEXT: ----- ------------------ ------------------------ ------------------------
 # CHECK-NEXT:     1 0x1100001122222222 [0x00001000, 0x00001010) [0x00002000, 0x00002020)
 
     .section .debug_cu_index, "", @progbits
 ## Header:
     .long 2             # Version
     .long 2             # 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 9             # Unknown section identifier
     .long 1             # DW_SECT_INFO
-    .long 9             # Invalid section identifier
-# Row 1:
-    .long 0x1000        # Offset in .debug_info.dwo
-    .long 0x2000
+## Row 1:
+    .long 0x1000        # Offset in an unknown section
+    .long 0x2000        # Offset in .debug_info.dwo
 ## Table of Section Sizes:
-    .long 0x10          # Size in .debug_info.dwo
-    .long 0x20
+    .long 0x10          # Size in an unknown section
+    .long 0x20          # Size in .debug_info.dwo