on 2021/7/22 下午8:56, Richard Biener wrote: > On Tue, Jul 20, 2021 at 4:37 > PM Kewen.Lin wrote: >> >> Hi, >> >> This v2 has addressed some review comments/suggestions: >> >> - Use "!=" instead of "<" in function operator!= (const Iter &rhs) >> - Add new CTOR loops_list (struct loops *loops, unsigned flags) >> to support loop hierarchy tree rather than just a function, >> and adjust to use loops* accordingly. > > I actually meant struct loop *, not struct loops * ;) At the point > we pondered to make loop invariant motion work on single > loop nests we gave up not only but also because it iterates > over the loop nest but all the iterators only ever can process > all loops, not say, all loops inside a specific 'loop' (and > including that 'loop' if LI_INCLUDE_ROOT). So the > CTOR would take the 'root' of the loop tree as argument. > > I see that doesn't trivially fit how loops_list works, at least > not for LI_ONLY_INNERMOST. But I guess FROM_INNERMOST > could be adjusted to do ONLY_INNERMOST as well? > Thanks for the clarification! I just realized that the previous version with struct loops* is problematic, all traversal is still bounded with outer_loop == NULL. I think what you expect is to respect the given loop_p root boundary. Since we just record the loops' nums, I think we still need the function* fn? So I add one optional argument loop_p root and update the visiting codes accordingly. Before this change, the previous visiting uses the outer_loop == NULL as the termination condition, it perfectly includes the root itself, but with this given root, we have to use it as the termination condition to avoid to iterate onto its possible existing next. For LI_ONLY_INNERMOST, I was thinking whether we can use the code like: struct loops *fn_loops = loops_for_fn (fn)->larray; for (i = 0; vec_safe_iterate (fn_loops, i, &aloop); i++) if (aloop != NULL && aloop->inner == NULL && flow_loop_nested_p (tree_root, aloop)) this->to_visit.quick_push (aloop->num); it has the stable bound, but if the given root only has several child loops, it can be much worse if there are many loops in fn. It seems impossible to predict the given root loop hierarchy size, maybe we can still use the original linear searching for the case loops_for_fn (fn) == root? But since this visiting seems not so performance critical, I chose to share the code originally used for FROM_INNERMOST, hope it can have better readability and maintainability. Bootstrapped and regtested on powerpc64le-linux-gnu P9, x86_64-redhat-linux and aarch64-linux-gnu, also bootstrapped on ppc64le P9 with bootstrap-O3 config. Does the attached patch meet what you expect? BR, Kewen ----- gcc/ChangeLog: * cfgloop.h (loops_list::loops_list): Add one optional argument root and adjust accordingly.