llvm-readobj -h doesn't display caps on mach-o files

[glandium]

% touch foo.c
% clang -o foo.o -c foo.c --target=arm64e-apple-darwin  # using Xcode clang
% llvm-otool -h foo.o
      magic cputype cpusubtype  caps    filetype ncmds sizeofcmds      flags
 0xfeedfacf 16777228          2  0x80           1     4        360 0x00002000
% llvm-readobj -h foo.o

File: foo.o
Format: Mach-O arm64
Arch: aarch64
AddressSize: 64bit
MachHeader {
  Magic: Magic64 (0xFEEDFACF)
  CpuType: Arm64 (0x100000C)
  CpuSubType: CPU_SUBTYPE_ARM64E (0x2)
  FileType: Relocatable (0x1)
  NumOfLoadCommands: 4
  SizeOfLoadCommands: 360
  Flags [ (0x2000)
    MH_SUBSECTIONS_VIA_SYMBOLS (0x2000)
  ]
  Reserved: 0x0
}

That 0x80 is nowhere to be seen in llvm-readobj's output.

[MaskRay]

Nice finding! This bitmask seems undocumented. Upstream clang does not set cpusubtype & CPU_SUBTYPE_MASK.

[glandium]

FWIW, this specific value is CPU_SUBTYPE_PTRAUTH_ABI, per mach/machine.h. See also #80200.