https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64715
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 35073 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35073&action=edit WIP patch So, on top of what you've committed, here is my unfinished attempt to disable for __bos undesirable transformations. On the: int main () { struct A { char buf1[9]; char buf2[1]; } a; char *p = a.buf1; char *q = p + 1; char *r = q + 4; char *t = r - 1; strcpy (t, str1 + 5); return 0; } main of this PRs testcase, the match.pd snippet doesn't work (genmatch thinks ADDR_EXPR operand must be a SSA_NAME, where that is not valid gimple), we end up with q_2 = &a.buf1 + 1; t_4 = &MEM[(void *)q_2 + 3B]; which would be better expressed as t_4 = &a.buf1 + 4; and then FRE folds that into: t_4 = &MEM[(void *)&a + 4B]; so if we went this way, we'd need to change genmatch to handle ADDR_EXPRs specially, and FRE to avoid forwarding into &MEM if that would lose info. Or, as discussed on IRC we can consider MEM_REFs where first operand isn't just SSA_NAME or ADDR_EXPR of a decl, but allow also ADDR_EXPR of handled_component_p (with base being a decl or MEM_REF with SSA_NAME first operand). Or add a new tree code, like OFFSETTED_ADDR_EXPR which would be like ADDR_EXPR, but with integer offset address to the ADDR_EXPR.
