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Re: Obsolete powerpc*-*-*spe*

On Tue, Feb 14, 2017 at 03:26:09PM +0100, Sebastian Huber wrote:
> >>>I propose to mark powerpc*-*-*spe* as obsolete in GCC 7.  This includes
> >>>the spe.h installed header file, all the __builtin_spe* intrinsics, the
> >>>-mfloat-gprs= command-line option, and the support for the SPE ABIs.
> >>>
> >>>No one has properly tested these targets in a long time (the latest
> >>>testresults I could find are from July 2015, >1000 failures), and the
> >>>SPE support makes a lot of code much more complex.
> >>>
> >>>Any objections to this obsoletion?  GCC 7 will then be the last release
> >>>with support for SPE (it will need --enable-obsolete to build these
> >>>targets), and we will delete the SPE support during GCC 8 development.
> >>the SPE unit is still used in the embedded PowerPC processors from
> >>Freescale/NXP/Qualcomm, for example QorIQ P1020. These products are not
> >>obsolete or even not recommended for new designs. These chips have a
> >>long product life-cycle.

Yes.  SPE is part of some e500 and some e200 CPUs I think (but only
some, in both cases).

> >It is also used in many PPC based microcontrollers, which are used in
> >the automotive industry and other places where you need highly reliable
> >and robust but powerful microcontrollers.  However, gcc support for
> >these has traditionally been poor - there is little support for the
> >variety of cores and configurations available from Freescale/NXP.  I
> >believe there is a chicken-and-egg situation here - few people use gcc
> >with these devices because there is poorer device support compared to
> >Freescale CodeWarrior or Green Hills, and there is little incentive for
> >gcc developers (such as the CodeSourcery or IBM PPC folks) to support
> >devices in gcc if no one uses that combination.
> Yes, we use GCC also one these chips, however, due to the lack of VLE 
> support the situation is even worse. Looks like support for the non-IBM 
> PowerPC is dead in GCC. I can understand this pretty well.

It's not true though; we still support all those cores, just not the
VLE extension (we never have), and I propose GCC 7 will drop the SPE
extension as well -- not all other support we have for those cores.
They will have to use soft float, alas.

We also still support all non-IBM non-FSL cores.

> With the Qualcomm takeover of Freescale/NXP I guess the PowerPC has no 
> future in this area and they will move to ARM for the processor cores.

That is my understanding as well, yes.

> >>Its a pity that Freescale/NXP/Qualcomm stopped to support GCC
> >>development and IBM is burdened to take care of this. I can understand
> >>your reasoning, however, its not true that there are no users of the SPE
> >>unit.

(I never said there are no users, I'm well aware).  The burden is not
just IBM's, also all other GCC developers and users.

> >I think what would be needed would be for Freescale/NXP/Qualcomm to put
> >some money and effort in here, with the aim of making gcc their standard
> >compiler for these targets (as they have done for ARM, replacing the old
> >CodeWarrior compiler).
> >
> >Failing that, it is of course better to have no SPE support than broken
> >SPE support, especially if it makes development harder for other devices.
> Yes, in case Qualcomm shows no interest to support their PowerPC stuff 
> in GCC its quite understandable to remove the support for it eventually. 
> IBM already did a great job in keeping it up and running for a long time.

That is the unfortunate reality.


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