[DebugInfo] Do not error on unsupported CIE version

[rafauler]

Summary

D81469 introduced a check to error on CIE version different
than 1 for eh_frame, but older compilers mistakenly create binaries
with this version set to 3 for DWARF4 or 4 to DWARF5. Move the check
to dump time instead of eh_frame parse time, so we can be tolerant
with older binaries.

[aprantl]

As long as the rest of the code is hardened against errors, this is fine. It's only the dumping code.

[rafauler]

Rebasing

llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp

if (IsEH && Length == 0) {
     return;
   }
 
   OS << format("%08" PRIx64, Offset)
      << format(" %0*" PRIx64, IsDWARF64 ? 16 : 8, Length)
      << format(" %0*" PRIx64, IsDWARF64 && !IsEH ? 16 : 8,
                getCIEId(IsDWARF64, IsEH))
      << " CIE\n"
-     << "  Format:                " << FormatString(IsDWARF64) << "\n"
-     << format("  Version:               %d\n", Version)
+     << "  Format:                " << FormatString(IsDWARF64) << "\n";
+  if (IsEH && Version != 1)
+    OS << "WARNING: unsupported CIE version\n";
+  OS << format("  Version:               %d\n", Version)
      << "  Augmentation:          \"" << Augmentation << "\"\n";
   if (Version >= 4) {
     OS << format("  Address size:          %u\n", (uint32_t)AddressSize);
     OS << format("  Segment desc size:     %u\n",
                  (uint32_t)SegmentDescriptorSize);
   }
   OS << format("  Code alignment factor: %u\n", (uint32_t)CodeAlignmentFactor);
   OS << format("  Data alignment factor: %d\n", (int32_t)DataAlignmentFactor);
uint64_t Id = Data.getRelocatedValue((IsDWARF64 && !IsEH) ? 8 : 4, &Offset,
                                          /*SectionIndex=*/nullptr, &Err);
     if (Err)
       return Err;
 
     if (Id == getCIEId(IsDWARF64, IsEH)) {
       uint8_t Version = Data.getU8(&Offset);
       const char *Augmentation = Data.getCStr(&Offset);
       StringRef AugmentationString(Augmentation ? Augmentation : "");
-      // TODO: we should provide a way to report a warning and continue dumping.
-      if (IsEH && Version != 1)
-        return createStringError(errc::not_supported,
-                                 "unsupported CIE version: %" PRIu8, Version);
-
       uint8_t AddressSize = Version < 4 ? Data.getAddressSize() :
                                           Data.getU8(&Offset);
       Data.setAddressSize(AddressSize);
       uint8_t SegmentDescriptorSize = Version < 4 ? 0 : Data.getU8(&Offset);
       uint64_t CodeAlignmentFactor = Data.getULEB128(&Offset);
       int64_t DataAlignmentFactor = Data.getSLEB128(&Offset);
       uint64_t ReturnAddressRegister =
           Version == 1 ? Data.getU8(&Offset) : Data.getULEB128(&Offset);

llvm/test/DebugInfo/X86/eh-frame-invalid-version-zero.s

 ## Check we do not support .eh_frame sections of version 0.
 
 # RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t
-# RUN: not llvm-dwarfdump -debug-frame %t 2>&1 | FileCheck %s
+# RUN: llvm-dwarfdump -debug-frame %t 2>&1 | FileCheck %s
 
-# CHECK: unsupported CIE version: 0
+# CHECK: unsupported CIE version
 
 .section .eh_frame,"a",@unwind
  .long .Lend - .LCIEptr ## Length
 .LCIEptr:
  .long 0x00000000       ## CIE ID
  .byte 0                ## Version
 .Lend:

llvm/test/DebugInfo/X86/eh-frame-invalid-version.s

 ## Check we do not support .eh_frame sections of versions greater than 1.
 
 # RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t
-# RUN: not llvm-dwarfdump -debug-frame %t 2>&1 | FileCheck %s
+# RUN: llvm-dwarfdump -debug-frame %t 2>&1 | FileCheck %s
 
-# CHECK: unsupported CIE version: 2
+# CHECK: unsupported CIE version
 
 .section .eh_frame,"a",@unwind
  .long .Lend - .LCIEptr ## Length
 .LCIEptr:
  .long 0x00000000       ## CIE ID
  .byte 2                ## Version
 .Lend: