https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101145
--- Comment #5 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> --- (In reply to bin cheng from comment #4) > (In reply to Jiu Fu Guo from comment #3) > > Yes, while the code in adjust_cond_for_loop_until_wrap seems somehow tricky: > > > > /* Only support simple cases for the moment. */ > > if (TREE_CODE (iv0->base) != INTEGER_CST > > || TREE_CODE (iv1->base) != INTEGER_CST) > > return false; > > > > This code requires both sides are constant. > Actually it requires an IV with constant base. I also feel that the intention of this function may only require one side constant for IV0 CODE IV1. As tests, for below loop, adjust_cond_for_loop_until_wrap return false: foo (int *__restrict__ a, int *__restrict__ b, unsigned i) { while (++i > 100) *a++ = *b++ + 1; } For below code, adjust_cond_for_loop_until_wrap returns true: i = UINT_MAX - 200; while (++i > 100) *a++ = *b++ + 1;