https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84433

--- Comment #8 from acsawdey at gcc dot gnu.org --- It looks like both gcc 7 and 8 assume that the statement ptrA->sA[ptrB->int1].zt = parm1; will only be executed 14+1 times because of the declaration sA[15]. However gcc 7 assumes the whole loop will only execute that number of times: Statement ptrA_14(D)->sA[ptrB__int1_lsm.11_22].zt = _34; is executed at most 14 (bounded by 14) + 1 times in loop 1. Analyzing # of iterations of loop 1 exit condition [15, + , 4294967295] != 0 bounds on difference of bases: -15 ... -15 result: # of iterations 15, bounded by 15 Loop 1 iterates 15 times. Loop 1 iterates at most 14 times. Loop 1 likely iterates at most 14 times. Analyzing # of iterations of loop 1 exit condition [15, + , 4294967295] != 0 bounds on difference of bases: -15 ... -15 result: # of iterations 15, bounded by 15 Removed pointless exit: if (ivtmp_24 != 0) were gcc8 does not: Statement ptrA_13(D)->sA[ptrB__int1_lsm.5_22].zt = _20; is executed at most 14 (bounded by 14) + 1 times in loop 1. Analyzing # of iterations of loop 1 exit condition [15, + , 4294967295] != 0 bounds on difference of bases: -15 ... -15 result: # of iterations 15, bounded by 15 Loop 1 iterates 15 times. Loop 1 iterates at most 15 times. Loop 1 likely iterates at most 15 times. Neither gcc 7 nor 8 produce any warnings for the revised test case with -Wall.