https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70527
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to amker from comment #0) > Seems "(long int) x * 12 - (long int)(x + 1) * 12" is missed in > generic-simplify. Interestingly, we manage just fine if 12 is replaced with a variable. The issue seems to be that we replace a-y*12 by a+y*-12 before we detect the common factor, so it might be as simple as moving code around. Although recognizing constant factors that differ only by their sign seems useful as well.
