WinDbg is unable to disassemble the x86/x64 UD1 instruction

[JamesMcNellis]

In a 64-bit debugging session:

0:000> u 00005555`5bb50b24
[symbol redacted]
00005555`5bb50b24 67              ???
00005555`5bb50b25 0f              ???
00005555`5bb50b26 b94002cccc      mov     ecx,0CCCC0240h
00005555`5bb50b2b cc              int     3
00005555`5bb50b2c cc              int     3
00005555`5bb50b2d cc              int     3
00005555`5bb50b2e cc              int     3
00005555`5bb50b2f cc              int     3

67 is an address size prefix; 0f b9 is the opcode for UD1. Clang/LLVM generates this instruction for various fatal runtime errors (like int 29h in Visual C++).