https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111151
--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #11) > Perhaps > --- fold-const.cc.jj8 2024-03-11 22:37:29.000000000 +0100 > +++ fold-const.cc 2024-03-22 19:31:44.189686120 +0100 > @@ -7104,6 +7104,27 @@ extract_muldiv_1 (tree t, tree c, enum t > if (TYPE_UNSIGNED (ctype) != TYPE_UNSIGNED (type)) > break; > > + /* Punt for multiplication altogether. > + MAX (1U + INT_MAX, 1U) * 2U is not equivalent to > + MAX ((1U + INT_MAX) * 2U, 1U * 2U), the former is > + 0U, the latter is 2U. > + MAX (INT_MIN / 2, 0) * -2 is not equivalent to > + MIN (INT_MIN / 2 * -2, 0 * -2), the former is > + well defined 0, the latter invokes UB. > + MAX (INT_MIN / 2, 5) * 5 is not equivalent to > + MAX (INT_MIN / 2 * 5, 5 * 5), the former is > + well defined 25, the latter invokes UB. */ > + if (code == MULT_EXPR) > + break; > + /* For division/modulo, punt on c being -1 for MAX, as > + MAX (INT_MIN, 0) / -1 is not equivalent to > + MIN (INT_MIN / -1, 0 / -1), the former is well defined > + 0, the latter invokes UB (or for -fwrapv is INT_MIN). > + MIN (INT_MIN, 0) / -1 already invokes UB, so the > + transformation won't make it worse. */ > + else if (tcode == MAX_EXPR && integer_minus_onep (c)) > + break; > + > /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */ > sub_strict_overflow_p = false; > if ((t1 = extract_muldiv (op0, c, code, wide_type, > ? I think that looks reasonable.
