[DebugInfo][llvm-dwarfdump] Fix dumping of unit header with DW_UT_partial type

[alok]

Summary

Currently llvm-dwarfdump crashes for Unit header with DW_UT_partial type.
-------------
llvm-dwarfdump: /tmp/llvm/include/llvm/ADT/Optional.h:197: T& llvm::optional_detail::OptionalStorage<T, true>::getValue() &
[with T = long unsigned int]: Assertion `hasVal' failed.
PLEASE submit a bug report to the technical support section of https://developer.amd.com/amd-aocc and include the crash backtrace.
Stack dump:
0.      Program arguments: llvm-dwarfdump -v /tmp/test/DebugInfo/X86/Output/dwarfdump-he
ader.s.tmp.o
 #0 0x00007f37d5ad8838 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /tmp/llvm/lib/Support/Unix/Signals.inc:565:0
 #1 0x00007f37d5ad88ef PrintStackTraceSignalHandler(void*) /tmp/llvm/lib/Support/Unix/Signals.inc:632:0
 #2 0x00007f37d5ad65bd llvm::sys::RunSignalHandlers() /tmp/llvm/lib/Support/Signals.cpp:71:0
 #3 0x00007f37d5ad81b9 SignalHandler(int) /tmp/llvm/lib/Support/Unix/Signals.inc:407:0
 #4 0x00007f37d4c26040 (/lib/x86_64-linux-gnu/libc.so.6+0x3f040)
 #5 0x00007f37d4c25fb7 raise /build/glibc-S9d2JN/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #6 0x00007f37d4c27921 abort /build/glibc-S9d2JN/glibc-2.27/stdlib/abort.c:81:0
 #7 0x00007f37d4c1748a __assert_fail_base /build/glibc-S9d2JN/glibc-2.27/assert/assert.c:89:0
 #8 0x00007f37d4c17502 (/lib/x86_64-linux-gnu/libc.so.6+0x30502)
 #9 0x00007f37d7576b81 llvm::optional_detail::OptionalStorage<unsigned long, true>::getValue() & /tmp/llvm/include/llvm/ADT/Optional.h:198:0
 #10 0x00007f37d75726ac llvm::Optional<unsigned long>::operator*() && /tmp/llvm/include/llvm/ADT/Optional.h:309:0
 #11 0x00007f37d7582968 llvm::DWARFCompileUnit::dump(llvm::raw_ostream&, llvm::DIDumpOptions) /tmp/llvm/lib/DebugInfo/DWARF/DWARFCompileUnit.cpp:30:0
--------------

This was due to tool expecting DW_AT_dwo_id for DW_UT_partial type which should be expected only for DW_UT_skeleton and DW_UT_split_compile. This is fixed now.

Thanks to @jini.susan.george for providing the fix.

[alok]

Updated to do minor correction in comment of test case.

[probinson]

LGTM. Not sure how we missed partial units the first time around--thanks!

[alok]

In D101255#2717420, @probinson wrote:

LGTM. Not sure how we missed partial units the first time around--thanks!

Thanks Paul.

llvm/lib/DebugInfo/DWARF/DWARFCompileUnit.cpp

OS << format("0x%08" PRIx64, getOffset()) << ": Compile Unit:"
      << ", format = " << dwarf::FormatString(getFormat())
      << ", version = " << format("0x%04x", getVersion());
   if (getVersion() >= 5)
     OS << ", unit_type = " << dwarf::UnitTypeString(getUnitType());
   OS << ", abbr_offset = " << format("0x%04" PRIx64, getAbbrOffset());
   if (!getAbbreviations())
     OS << " (invalid)";
   OS << ", addr_size = " << format("0x%02x", getAddressByteSize());
-  if (getVersion() >= 5 && getUnitType() != dwarf::DW_UT_compile)
+  if (getVersion() >= 5 && (getUnitType() == dwarf::DW_UT_skeleton ||
+                            getUnitType() == dwarf::DW_UT_split_compile))
     OS << ", DWO_id = " << format("0x%016" PRIx64, *getDWOId());
   OS << " (next unit at " << format("0x%08" PRIx64, getNextUnitOffset())
      << ")\n";
 
   if (DWARFDie CUDie = getUnitDIE(false))
     CUDie.dump(OS, 0, DumpOpts);
   else
     OS << "<compile unit can't be parsed!>\n\n";
 }
 
 // VTable anchor.
 DWARFCompileUnit::~DWARFCompileUnit() = default;

llvm/test/DebugInfo/X86/dwarfdump-header.s

# All CUs/TUs use the same abbrev section for simplicity.
         .byte 0x00  # EOM(2)
         .byte 0x03  # Abbrev code
         .byte 0x13  # DW_TAG_structure_type
         .byte 0x00  # DW_CHILDREN_no (no members)
         .byte 0x03  # DW_AT_name
         .byte 0x0e  # DW_FORM_strp
         .byte 0x00  # EOM(1)
         .byte 0x00  # EOM(2)
+        .byte 0x04  # Abbrev code
+        .byte 0x3c  # DW_TAG_partial_unit
+        .byte 0x00  # DW_CHILDREN_no
+        .byte 0x03  # DW_AT_name
+        .byte 0x0e  # DW_FORM_strp
+        .byte 0x00  # EOM(1)
+        .byte 0x00  # EOM(2)
         .byte 0x00  # EOM(3)
 
 # And a .dwo copy for the .dwo sections.
         .section .debug_abbrev.dwo,"e",@progbits
         .byte 0x01  # Abbrev code
         .byte 0x11  # DW_TAG_compile_unit
         .byte 0x00  # DW_CHILDREN_no
         .byte 0x25  # DW_AT_producer
# The compile-unit DIE, with DW_AT_producer, DW_AT_name, DW_AT_stmt_list.
         .long str_CU_5
         .long LH_5_start
         .byte 0 # NULL
 CU_5_end:
 
 # CHECK: 0x00000019: Compile Unit: length = 0x00000016, format = DWARF32, version = 0x0005, unit_type = DW_UT_compile, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000033)
 # CHECK: 0x00000025: DW_TAG_compile_unit
 
+# DWARF v5 CU header (Unit Type = DW_UT_partial).
+        .long  CU_5_partial_end-CU_5_partial_version  # Length of Unit
+CU_5_partial_version:
+        .short 5               # DWARF version number
+        .byte 3                # DWARF Unit Type
+        .byte 8                # Address Size (in bytes)
+        .long .debug_abbrev    # Offset Into Abbrev. Section
+# The partial-unit DIE, with DW_AT_name
+        .byte 4
+        .long str_CU_5
+        .byte 0 # NULL
+CU_5_partial_end:
+
+# CHECK: 0x00000033: Compile Unit: length = 0x0000000e, format = DWARF32, version = 0x0005, unit_type = DW_UT_partial, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000045)
+# CHECK: 0x0000003f: DW_TAG_partial_unit
+
         .section .debug_info.dwo,"e",@progbits
 # CHECK-LABEL: .debug_info.dwo
 
 # DWARF v5 split CU header.
         .long  CU_split_5_end-CU_split_5_version # Length of Unit
 CU_split_5_version:
         .short 5                # DWARF version number
         .byte 5                 # DWARF Unit Type