This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Proposal for merging scalar-storage-order branch into mainline
- From: pinskia at gmail dot com
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Eric Botcazou <ebotcazou at adacore dot com>, GCC Development <gcc at gcc dot gnu dot org>
- Date: Tue, 9 Jun 2015 20:03:20 +0800
- Subject: Re: Proposal for merging scalar-storage-order branch into mainline
- Authentication-results: sourceware.org; auth=none
- References: <2354857 dot 0uXrE6NL1R at polaris> <24307404 dot yEd3bIJVu1 at polaris> <CAFiYyc3UYWMKCE=qRwY=iPjtscB3o3nyQBLDBjLrnX4d5NKNvg at mail dot gmail dot com> <5929917 dot 788V8UTWHt at polaris> <CAFiYyc0aVBYeT2Utr9=NxKVLGMEPWMBR7Qb+=ataQG93fgw55w at mail dot gmail dot com>
> On Jun 9, 2015, at 7:53 PM, Richard Biener <richard.guenther@gmail.com> wrote:
>
> On Tue, Jun 9, 2015 at 1:12 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>>> Yes, but I'd expect them to be optimized away (well, hopefully).
>>
>> OK, but you cannot reasonably expose everything in GENERIC/GIMPLE, for example
>> the mask-and-shift operations to extract bitfields in reverse SSO, only the
>> RTL expander has the (quite complex) logic and I doubt you want to teach the
>> GIMPLE optimizers about this low-level mess.
>
> Why would you want to support this on bitfields ... (/me runs away).
Because some folks don't want to audit their code to where to add byteswaps. I am serious people have legacy big-endian code they want to run little endian. There is a reason this is around in the first place. Developers are lazy.
Thanks,
Andrew
>
>>> Anwyay, and I thought use of the feature would be rare so that "every load
>>> and store" is still very few?
>>
>> Experience has shown that, when users start to use it, they use it extensively
>> (too extensively if you ask me) so the implementation cannot be too dumb.
>
> :/
>
>> --
>> Eric Botcazou