6846a68073
atomic_fetchadd_32. Without it gcc would use it as input register for v and sometimes generate following code for function call like atomic_fetchadd_32(&(fp)->f_count, -1): 801238b4: 2402ffff li v0,-1 801238b8: c2230018 ll v1,24(s1) 801238bc: 00431021 addu v0,v0,v1 801238c0: e2220018 sc v0,24(s1) 801238c4: 1040fffc beqz v0,801238b8 <dupfdopen+0x2e8> 801238c8: 00000000 nop Which is definitly wrong because if sc fails v0 is set to 0 and previous value of -1 is overriden hence whole operation turns to bogus