Re: RFA (hash-map): PATCH to support GTY((cache)) with hash_map

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

On Fri, Sep 15, 2017 at 11:45 PM, Jason Merrill <jason@redhat.com> wrote:
> The hash_map interface is a lot more convenient than that of
> hash_table for cases where it makes sense, but there hasn't been a way
> to get the ggc_cache_remove behavior with a hash_map.  In other words,
> not marking elements during the initial ggc marking phase, but maybe
> marking them during the clear_caches phase based on keep_cache_entry.
>
> This patch implements that by:
>
> Adding a ggc_maybe_mx member function to ggc_remove, and overriding
> that instead of ggc_mx in ggc_cache_remove.
> Calling H::ggc_maybe_mx instead of H::ggc_mx in gt_ggc_mx (hash_table *).
> Calling H::ggc_mx in gt_cleare_caches (hash_table *) rather than
> relying on an extern declaration of a plain function that cannot be
> declared for hash_map::hash_entry.
> Adding ggc_maybe_mx and keep_cache_entry to hash_map::hash_entry.
> Adding gt_cleare_cache for hash_map.
> Adding a boolean constant to the hash-map traits indicating whether we
> want the cache behavior above.
>
> I then define a typedef tree_cache_map to use this functionality, and
> use it in a few places in the C++ front end.
>
> Tested x86_64-pc-linux-gnu, OK for trunk?

Ok.

Richard.