https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100499
--- Comment #24 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- (In reply to Aldy Hernandez from comment #23) > The above yields overflow for the 16-bit expression in question: > > (gdb) p debug(top) > g_2823_lsm.5_6 * 7854 + 57682 > > (gdb) p may_overflow_p (top) > $6 = true > > This is because the range of the above expression in unsigned 16-bit yields > VARYING (R), whereas in 32-bit unsigned yields [57682, 514769572] (W). Which, I will note, matches Andrew's hand calculation of: >so the original expression is in 16 bit math, and if it was evaluated as > [0, 65535] * [7854, 7854] + [57682, 57682] > in 32 bit precision, it would come back with the answer [57682, 514769572].
