clang:
```
% llvm-objdump -d --disassemble-symbols=membarrier_action_seqcst /usr/obj/usr/src/freebsd/amd64.amd64/sys/GENERIC/kernel
/usr/obj/usr/src/freebsd/amd64.amd64/sys/GENERIC/kernel: file format elf64-x86-64
Disassembly of section .text:
ffffffff80b1d020 <membarrier_action_seqcst>:
ffffffff80b1d020: 55 pushq %rbp
ffffffff80b1d021: 48 89 e5 movq %rsp, %rbp
ffffffff80b1d024: f0 lock
ffffffff80b1d025: 65 83 04 25 00 01 00 00 00 addl $0x0, %gs:0x100
ffffffff80b1d02e: 5d popq %rbp
ffffffff80b1d02f: c3 retq
```
gcc13:
```
% llvm-objdump -d --disassemble-symbols=membarrier_action_seqcst /usr/obj/gcc13/usr/src/freebsd/amd64.amd64/sys/GENERIC/kernel
/usr/obj/gcc13/usr/src/freebsd/amd64.amd64/sys/GENERIC/kernel: file format elf64-x86-64
Disassembly of section .text:
ffffffff81448550 <membarrier_action_seqcst>:
ffffffff81448550: f0 lock
ffffffff81448551: 65 83 04 25 00 01 00 00 00 addl $0x0, %gs:0x100
ffffffff8144855a: c3 retq
ffffffff8144855b: 0f 1f 44 00 00 nopl (%rax,%rax)
```