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Re: Obsolete powerpc*-*-*spe*
- From: Olivier Hainque <hainque at adacore dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: Olivier Hainque <hainque at adacore dot com>, Andrew Jenner <andrew at codesourcery dot com>, David Edelsohn <dje dot gcc at gmail dot com>, GCC Development <gcc at gcc dot gnu dot org>, Sandra Loosemore <sandra at codesourcery dot com>, Arnaud Charlet <charlet at adacore dot com>, Joel Brobecker <brobecker at adacore dot com>
- Date: Wed, 15 Mar 2017 17:16:06 +0100
- Subject: Re: Obsolete powerpc*-*-*spe*
- Authentication-results: sourceware.org; auth=none
- References: <20170214030703.GS21840@gate.crashing.org> <58A61E7B.4060903@codesourcery.com> <20170216221937.GB21840@gate.crashing.org> <58A63B91.1040102@codesourcery.com> <CAGWvny=aWTzSta=jwZS8HwmWU4riN7ee46CZP8MwS2PcYPC0mw@mail.gmail.com> <452E2837-FC8A-4DA2-A2B9-F58151841F58@adacore.com> <CAGWvnymQjd=k4Hv6PgWW2kuCinQTOQvSRvSEnVRN-C-RnvmKig@mail.gmail.com> <45cf27b1-2e27-460c-cb32-3be93f16b6d2@codesourcery.com> <D3FAA9C8-C011-4701-A148-0A19AF3B10E1@adacore.com> <20170315142623.GN4402@gate.crashing.org>
> On Mar 15, 2017, at 15:26 , Segher Boessenkool <segher@kernel.crashing.org> wrote:
> I do not think VLE can get in, not in its current shape at least. VLE
> is very unlike PowerPC in many ways so it comes at a very big cost to
> the port (maintenance and otherwise -- maintenance is what I care about
> most).
>
> Since SPE and VLE only share the part of the rs6000 port that doesn't
> change at all (except for a bug fix once or twice a year), and everything
> else needs special cases all over the place, it seems to me it would be
> best for everyone if we split the rs6000 port in two, one for SPE and VLE
> and one for the rest. Both ports could then be very significantly
> simplified.
>
> I am assuming SPE and VLE do not support AltiVec or 64-bit PowerPC,
> please correct me if that is incorrect. Also, is "normal" floating
> point supported at all?
>
> Do you (AdaCore and Mentor) think splitting the port is a good idea?
That's actually an option we considered.
We haven't gone very far in studying what this would entail and were still
unclear on how much of a clean separation we could get without risking the
introduction of (too much) instability.
It seemed like avoiding code duplication (that would otherwise be a maintenance
issue) might require refactoring in sensitive areas, e.g. prologue/epilogue
expansion, but the perspective of getting two variants simpler to grasp on top
of common code definitely sounds attractive and worth some effort.
Olivier