https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79536
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> --- The problem here is that we have a NOP_EXPR: (int) -x. negate_expr_p returns true for that, which means that fold_negate_expr cannot return NULL_TREE. But that's what happens, and that leads to a crash in fold_build2: 581 case COMPLEX_EXPR: 582 if (negate_expr_p (t)) 583 return fold_build2_loc (loc, COMPLEX_EXPR, type, 584 fold_negate_expr (loc, TREE_OPERAND (t, 0)), 585 fold_negate_expr (loc, TREE_OPERAND (t, 1))); I see that negate_expr_p has STRIP_SIGN_NOPS, so the "(int) -x" becomes "-x", but fold_negate_expr doesn't have any STRIP_SIGN_NOPS.