Obsolete powerpc*-*-*spe*

Olivier Hainque hainque@adacore.com
Wed Mar 15 16:16:00 GMT 2017


> 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



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