Hi! On Wed, Jun 07, 2023 at 04:21:11PM +0800, Jiufu Guo wrote: > This patch tries to optimize "(X - N * M) / N" to "X / N - M". > For C code, "/" towards zero (trunc_div), and "X - N * M" maybe > wrap/overflow/underflow. So, it is valid that "X - N * M" does > not cross zero and does not wrap/overflow/underflow.
Is it ever valid semi-generally when N does not divide X? Say X=5, N=2, M=3. Then the original expression evaluates to 0, but the new one to -1. Whenever one of the divisions rounds up and the other rounds down you have this problem. Segher
