[RFC/PATCH] Use range-based for loops for traversing loops

[Richard Biener]

On Mon, Jul 19, 2021 at 8:20 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi,
>
> This patch follows Martin's suggestion here[1], to support
> range-based for loops for traversing loops, analogously to
> the patch for vec[2].
>
> 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.
>
> Any comments are appreciated.

Since you are touching all FOR_EACH_LOOP please
make implicit 'cfun' uses explicit.  I'm not sure ALL_LOOPS
should scream, I think all_loops (function *, flags) would be
nicer.

Note I'm anticipating iteration over a subset of the loop tree
which would ask for specifying the 'root' of the loop tree to
iterate over so it could be

  loops_list (class loop *root, unsigned flags)

and the "all" cases use loops_list (loops_for_fn (cfun), flags) then.
Providing an overload with struct function is of course OK.

Richard.

> BR,
> Kewen
>
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2021-June/573424.html
> [2] https://gcc.gnu.org/pipermail/gcc-patches/2021-June/572315.html
> -----
> gcc/ChangeLog:
>
>         * cfgloop.h (class loop_iterator): Rename to ...
>         (class loops_list): ... this.
>         (loop_iterator::next): Rename to ...
>         (loops_list::iterator::fill_curr_loop): ... this and adjust.
>         (loop_iterator::loop_iterator): Rename to ...
>         (loops_list::loops_list): ... this and adjust.
>         (FOR_EACH_LOOP): Rename to ...
>         (ALL_LOOPS): ... this.
>         (FOR_EACH_LOOP_FN): Rename to ...
>         (ALL_LOOPS_FN): this.
>         (loops_list::iterator): New class.
>         (loops_list::begin): New function.
>         (loops_list::end): Likewise.
>         * cfgloop.c (flow_loops_dump): Adjust FOR_EACH_LOOP* with ALL_LOOPS*.
>         (sort_sibling_loops): Likewise.
>         (disambiguate_loops_with_multiple_latches): Likewise.
>         (verify_loop_structure): Likewise.
>         * cfgloopmanip.c (create_preheaders): Likewise.
>         (force_single_succ_latches): Likewise.
>         * config/aarch64/falkor-tag-collision-avoidance.c
>         (execute_tag_collision_avoidance): Likewise.
>         * config/mn10300/mn10300.c (mn10300_scan_for_setlb_lcc): Likewise.
>         * config/s390/s390.c (s390_adjust_loops): Likewise.
>         * doc/loop.texi: Likewise.
>         * gimple-loop-interchange.cc (pass_linterchange::execute): Likewise.
>         * gimple-loop-jam.c (tree_loop_unroll_and_jam): Likewise.
>         * gimple-loop-versioning.cc (loop_versioning::analyze_blocks): Likewise.
>         (loop_versioning::make_versioning_decisions): Likewise.
>         * gimple-ssa-split-paths.c (split_paths): Likewise.
>         * graphite-isl-ast-to-gimple.c (graphite_regenerate_ast_isl): Likewise.
>         * graphite.c (canonicalize_loop_form): Likewise.
>         (graphite_transform_loops): Likewise.
>         * ipa-fnsummary.c (analyze_function_body): Likewise.
>         * ipa-pure-const.c (analyze_function): Likewise.
>         * loop-doloop.c (doloop_optimize_loops): Likewise.
>         * loop-init.c (loop_optimizer_finalize): Likewise.
>         (fix_loop_structure): Likewise.
>         * loop-invariant.c (calculate_loop_reg_pressure): Likewise.
>         (move_loop_invariants): Likewise.
>         * loop-unroll.c (decide_unrolling): Likewise.
>         (unroll_loops): Likewise.
>         * modulo-sched.c (sms_schedule): Likewise.
>         * predict.c (predict_loops): Likewise.
>         (pass_profile::execute): Likewise.
>         * profile.c (branch_prob): Likewise.
>         * sel-sched-ir.c (sel_finish_pipelining): Likewise.
>         (sel_find_rgns): Likewise.
>         * tree-cfg.c (replace_loop_annotate): Likewise.
>         (replace_uses_by): Likewise.
>         (move_sese_region_to_fn): Likewise.
>         * tree-if-conv.c (pass_if_conversion::execute): Likewise.
>         * tree-loop-distribution.c (loop_distribution::execute): Likewise.
>         * tree-parloops.c (parallelize_loops): Likewise.
>         * tree-predcom.c (tree_predictive_commoning): Likewise.
>         * tree-scalar-evolution.c (scev_initialize): Likewise.
>         (scev_reset): Likewise.
>         * tree-ssa-dce.c (find_obviously_necessary_stmts): Likewise.
>         * tree-ssa-live.c (remove_unused_locals): Likewise.
>         * tree-ssa-loop-ch.c (ch_base::copy_headers): Likewise.
>         * tree-ssa-loop-im.c (analyze_memory_references): Likewise.
>         (tree_ssa_lim_initialize): Likewise.
>         * tree-ssa-loop-ivcanon.c (canonicalize_induction_variables): Likewise.
>         * tree-ssa-loop-ivopts.c (tree_ssa_iv_optimize): Likewise.
>         * tree-ssa-loop-manip.c (get_loops_exits): Likewise.
>         * tree-ssa-loop-niter.c (estimate_numbers_of_iterations): Likewise.
>         (free_numbers_of_iterations_estimates): Likewise.
>         * tree-ssa-loop-prefetch.c (tree_ssa_prefetch_arrays): Likewise.
>         * tree-ssa-loop-split.c (tree_ssa_split_loops): Likewise.
>         * tree-ssa-loop-unswitch.c (tree_ssa_unswitch_loops): Likewise.
>         * tree-ssa-loop.c (gate_oacc_kernels): Likewise.
>         (pass_scev_cprop::execute): Likewise.
>         * tree-ssa-propagate.c (clean_up_loop_closed_phi): Likewise.
>         * tree-ssa-sccvn.c (do_rpo_vn): Likewise.
>         * tree-ssa-threadupdate.c
>         (jump_thread_path_registry::thread_through_all_blocks): Likewise.
>         * tree-vectorizer.c (vectorize_loops): Likewise.
>         * tree-vrp.c (vrp_asserts::find_assert_locations): Likewise.