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Re: [C++ PATCH] Use RANGE_EXPRs in build_vec_init (PR c++/82294, PR c++/87436)


OK.
On Thu, Dec 13, 2018 at 6:03 PM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> The following patch makes use of RANGE_EXPRs in build_vec_init, instead of
> appending many ctor elements.
>
> E.g. on the PR87436 testcase the memory usage goes down from more than 5GB
> to a few megabytes and compile time decreases significantly too.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> Testcases not included, see follow-up patch.
>
> 2018-12-13  Jakub Jelinek  <jakub@redhat.com>
>
>         PR c++/82294
>         PR c++/87436
>         * init.c (build_vec_init): Change num_initialized_elts type from int
>         to HOST_WIDE_INT.  Build a RANGE_EXPR if e needs to be repeated more
>         than once.
>
> --- gcc/cp/init.c.jj    2018-11-13 09:49:33.150035688 +0100
> +++ gcc/cp/init.c       2018-12-13 15:08:08.446783069 +0100
> @@ -4104,7 +4104,7 @@ build_vec_init (tree base, tree maxindex
>    tree compound_stmt;
>    int destroy_temps;
>    tree try_block = NULL_TREE;
> -  int num_initialized_elts = 0;
> +  HOST_WIDE_INT num_initialized_elts = 0;
>    bool is_global;
>    tree obase = base;
>    bool xvalue = false;
> @@ -4539,10 +4539,13 @@ build_vec_init (tree base, tree maxindex
>
>           if (e)
>             {
> -             int max = tree_to_shwi (maxindex)+1;
> -             for (; num_initialized_elts < max; ++num_initialized_elts)
> +             HOST_WIDE_INT last = tree_to_shwi (maxindex);
> +             if (num_initialized_elts <= last)
>                 {
>                   tree field = size_int (num_initialized_elts);
> +                 if (num_initialized_elts != last)
> +                   field = build2 (RANGE_EXPR, sizetype, field,
> +                                   size_int (last));
>                   CONSTRUCTOR_APPEND_ELT (const_vec, field, e);
>                 }
>             }
>
>         Jakub


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