Re: [PATCH GCC]Improve candidate selecting in IVOPT

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Sep 30, 2014 at 11:59 AM, Bin Cheng <bin.cheng@arm.com> wrote:
> Hi,
> As analyzed in PR62178, IVOPT can't find the optimal iv set for that case.
> The problem with current heuristic algorithm is it only replaces candidate
> with ones not in current solution one by one, starting from small solution.
> This patch adds another heuristic which starts from assigning the best
> candidate for each iv use, then replaces candidate with ones in the current
> solution.
> Before this patch, there are two runs of find_optimal_set_1 to find the
> optimal iv sets, we name them as set_a and set_b.  After this patch we will
> have set_c.  At last, IVOPT chooses the best one from set_a/set_b/set_c.  To
> prove that this patch is necessary, I collected instrumental data for gcc
> bootstrap, spec2k, eembc and can confirm for some cases only the newly added
> heuristic can find the optimal iv set.  The number of these cases in which
> set_c is the optimal one is on the same level of set_b.
> As for the compilation time, the newly added function actually is one
> iteration of previous selection algorithm, it should be much faster than
> previous process.
>
> I also added one target dependent test case.
> Bootstrap and test on x86_64, test on aarch64.  Any comments?

Ok.

Thanks,
Richard.

> 2014-09-30  Bin Cheng  <bin.cheng@arm.com>
>
>         PR tree-optimization/62178
>         * tree-ssa-loop-ivopts.c (enum sel_type): New.
>         (iv_ca_add_use): Add parameter RELATED_P and find the best cand
>         for iv use if it's true.
>         (try_add_cand_for, get_initial_solution): Change paramter ORIGINALP
>         to SELECT_TYPE and handle it.
>         (find_optimal_iv_set_1): Ditto.
>         (try_prune_iv_set, find_optimal_iv_set_2): New functions.
>         (find_optimal_iv_set): Call find_optimal_iv_set_2 and choose the
>         best candidate set.
>
> gcc/testsuite/ChangeLog
> 2014-09-30  Bin Cheng  <bin.cheng@arm.com>
>
>         PR tree-optimization/62178
>         * gcc.target/aarch64/pr62178.c: New test.