https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92712
--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> --- For A*B+A*C -> (B+C)*A the problematic cases are A==-1 and B > 0 and C==(max-B)+1 (i.e. when B+C overflows to min) or A==0 and B < 0 and C<min-B or A==0 and B > 0 and C>max-B (last two cases cover when B+C overflows) For A*B-A*C -> (B-C)*A the problematic cases are A==-1 and B > 0 and C==min+B (i.e. when B-C is min) or A==0 and B < -1 and C>B-min or A==0 and B >= 0 and C<B-max (last two cases cover when B-C overflows) Again, we perform the operation right now if A is not 0 and not -1 for certain. I guess we could handle those cases by using something like check_for_binary_op_overflow, except that for the case where A might be -1 and plusminus equal to MINUS_EXPR we also need to make sure the result of B-C is known not to be min.
