libsystem_pthread.dylib`pthread_mutex_lock:
-> 0x181581388 <+0>: ldr x8, [x0]
0x18158138c <+4>: movz w9, #0x4d55, lsl #16
0x181581390 <+8>: movk w9, #0x545a
0x181581394 <+12>: cmp x8, x9
0x181581398 <+16>: b.ne 0x1815813fc ; <+116>
0x18158139c <+20>: add x8, x0, #31 ; =31
0x1815813a0 <+24>: and x8, x8, #0xfffffffffffffff8
0x1815813a4 <+28>: mrs x9, TPIDRRO_EL0
0x1815813a8 <+32>: and x9, x9, #0xfffffffffffffff8
0x1815813ac <+36>: ldr x9, [x9]
0x1815813b0 <+40>: ldr x9, [x9, #216]
0x1815813b4 <+44>: add x10, x0, #39 ; =39
0x1815813b8 <+48>: and x10, x10, #0xfffffffffffffff8
0x1815813bc <+52>: b 0x1815813c4 ; <+60>
0x1815813c0 <+56>: clrex
0x1815813c4 <+60>: ldr x11, [x10]
0x1815813c8 <+64>: ldr x2, [x8]
0x1815813cc <+68>: and x12, x11, #0xffffffff00000000
0x1815813d0 <+72>: add w13, w11, #256 ; =256
0x1815813d4 <+76>: and x13, x13, #0xfffffffc
0x1815813d8 <+80>: orr x12, x12, x13
0x1815813dc <+84>: orr x1, x12, #0x3
0x1815813e0 <+88>: ldaxr x12, [x10]
0x1815813e4 <+92>: cmp x12, x11
0x1815813e8 <+96>: b.ne 0x1815813c0 ; <+56>
0x1815813ec <+100>: stxr w12, x1, [x10]
0x1815813f0 <+104>: cbnz w12, 0x1815813e0 ; <+88>
0x1815813f4 <+108>: tbz w11, #1, 0x181581404 ; <+124>
0x1815813f8 <+112>: b 0x181586d54 ; _pthread_mutex_lock_wait
0x1815813fc <+116>: movz w1, #0
0x181581400 <+120>: b 0x181586e90 ; _pthread_mutex_lock_slow
0x181581404 <+124>: str x9, [x8]
0x181581408 <+128>: movz w0, #0
0x18158140c <+132>: ret

i don't understand this issue