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Re: [RFC, PATCH]: Introduction of callgraph annotation class
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Martin LiÅka <mliska at suse dot cz>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 16 Oct 2014 13:45:48 +0200
- Subject: Re: [RFC, PATCH]: Introduction of callgraph annotation class
- Authentication-results: sourceware.org; auth=none
- References: <543EA03A dot 7000000 at suse dot cz> <CAFiYyc12P-DMR=7otSYN+G6DJLK=y+EN7c4sBFZBk1=Lgz9Mzw at mail dot gmail dot com> <543FAF1A dot 8030907 at suse dot cz>
On Thu, Oct 16, 2014 at 1:42 PM, Martin LiÅka <firstname.lastname@example.org> wrote:
> On 10/16/2014 01:31 PM, Richard Biener wrote:
>> On Wed, Oct 15, 2014 at 6:26 PM, Martin LiÅka <email@example.com> wrote:
>>> Following patch introduces a new class called callgraph_annotation. Idea
>>> behind the patch is to provide a generic interface one can use to
>>> custom info related to a cgraph_node. As you know, symbol_table provides
>>> hooks for creation, deletion and duplication of a cgraph_node. If you
>>> have a
>>> pass, you need to handle all these hooks and store custom data in your
>>> As an example, after discussion with Martin, I chose usage in ipa-prop.h:
>>> data structure:
>>> vec<ipa_node_params> ipa_node_params_vector
>>> if the pass handles an event, following chunk is executed:
>>> if (ipa_node_params_vector.length () <= (unsigned)
>>> ipa_node_params_vector.safe_grow_cleared (symtab->cgraph_max_uid +
>>> The problem is that you can have sparse UIDs of cgraph_nodes and every
>>> you have to allocate a vector of size equal to cgraph_max_uid.
>>> As a replacement, I implemented first version of cgraph_annotation that
>>> internally uses hash_map<cgraph_unique_identifier, T>.
>>> Every time a node is deleted, we remove corresponding data associated to
>>> What do you think about it?
>> I don't like "generic annotation" facilities at all. Would it be possible
>> to make cgraph UIDs not sparse? (keep a free-list of cgraph nodes
>> with UID < cgraph_max_uid, only really free nodes at the end)
>> Using a different data structure than a vector indexed by cgraph UID
>> should also be easily possible (a map from UID to data, hash_map <int,
> If I recall correctly, we recycle cgraph_nodes and it's possible that an UID
> is given to different nodes:
> symbol_table::allocate_cgraph_symbol (void). Such uid is problematic from
> perspective that it cannot be used as a index to a vector.
> It was also Honza's note that one can choose inner implementation of such
> annotation class. We can implement both sparse (hash_map) and consecutive
> vector data structure.
> According to first numbers I was given, Inkscape allocates about ~64k
> cgraph_nodes in WPA. After function merging is processed, it shrinks to
> about a half. So that, our free list contains the half of nodes. If we use
> consecutive vector, our memory impact is bigger thank necessary.
I don't think there is anything that forces us to retain the original
UID allocation after WPA merging? So why not compact it?
>>> Thank you,