Re: Proposal: PageLayout footprint

Gregory Stark wrote:
> "Zdenek Kotala" <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
>> By my opinion -fipa-struct-reorg GCC option could break structure. And maybe
>> there are more compiler magic switches and optimization on different platforms
>> which can modify structure alignment or member order. It probably does not
>> happen often but footprint should protect people to shot himself.
>
> My version of GCC doesn't have that option, what does it do?

From gcc man page:

> -fipa-struct-reorg
> Perform structure reorganization optimization, that change C-like
> structures layout in order to better utilize spatial locality.
> This transformation is affective for programs containing arrays of
> structures. Available in two compilation modes: profile-based
> (enabled with -fprofile-generate) or static (which uses built-in
> heuristics). Require -fipa-type-escape to provide the safety of
> this transformation. It works only in whole program mode, so it
> requires -fwhole-program and -combine to be enabled. Structures
> considered cold by this transformation are not affected (see
> --param struct-reorg-cold-struct-ratio=value).

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com