This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH][RFC] Make expansion of balanced binary trees of switches on tree level.
- From: Jeff Law <law at redhat dot com>
- To: Jan Hubicka <hubicka at ucw dot cz>, Martin Liška <mliska at suse dot cz>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Martin Jambor <mjambor at suse dot cz>
- Date: Thu, 3 Aug 2017 10:11:31 -0600
- Subject: Re: [PATCH][RFC] Make expansion of balanced binary trees of switches on tree level.
- Authentication-results: sourceware.org; auth=none
- Authentication-results: ext-mx01.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com
- Authentication-results: ext-mx01.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=law at redhat dot com
- Dmarc-filter: OpenDMARC Filter v1.3.2 mx1.redhat.com BAE4880E75
- References: <b9bed4ff-cbb3-4d33-f54f-0f5a45b421e9@suse.cz> <CAFiYyc04cS6qBcReZqx77_=sLw99gfYEPC7YFMsYpOoRRrZxWQ@mail.gmail.com> <1e0f407d-2d23-c4c6-b65f-60b44a1a05fc@suse.cz> <20170803090246.GA98906@kam.mff.cuni.cz>
On 08/03/2017 03:02 AM, Jan Hubicka wrote:
>> On 08/02/2017 01:51 PM, Richard Biener wrote:
>>> On Wed, Aug 2, 2017 at 1:20 PM, Martin Liška <mliska@suse.cz> wrote:
>>>> Hello.
>>>>
>>>> After some discussions with Honza, I've decided to convert current code in stmt.c that
>>>> is responsible for switch expansion. More precisely, I would like to convert the code
>>>> to expand gswitch statements on tree level. Currently the newly created pass is executed
>>>> at the end of tree optimizations.
>>>>
>>>> My plan for future is to inspire in [1] and come up with some more sophisticated switch
>>>> expansions. For that I've been working on a paper where I'll summarize statistics based
>>>> on what I've collected in openSUSE distribution with specially instrumented GCC. If I'll be
>>>> happy I can also fit in to schedule of this year's Cauldron with a talk.
>>>>
>>>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>>>>
>>>> Thoughts?
>>>
>>> First of all thanks.
>>>
>>> I think part of switch expansion moved to switch-conversion some time ago
>>> (emit_case_bit_tests). So maybe the full lowering should be in at least
>>> the same source file and it should maybe applied earlier for a subset of
>>> cases (very low number of cases for example).
>>
>> Yep, good idea. I'll take a look.
>>
>>>
>>> Did you base the code on the RTL expansion code or did you re-write it from
>>> scratch?
>>
>> It's based, I've just changed the function that create CFG.
>
> I have talked Martin to do this in first step. Switch expansion is infinitely
> difficult problem and I think changing representation first and keeping the
> basic algorithm is easiest way to get something done. Algorithm will be
> improved next as far as I know :)
I can support that approach :-)
jeff