On Tue, Dec 13, 2022 at 06:15:16AM +0100, John Paul Adrian Glaubitz wrote: > Hello! > > On 12/12/22 20:45, Michael Cree wrote: > > Either the arch baseline is raised to something that is easier to > > maintain (which, frankly, I think is essential if the Alpha port is to > > survive any longer), someone else steps up to fix the brokenness that > > arises from non-atomic multi-cpu-instruction 8-bit and 16-bit memory > > accesses, or I bail out of maintaining Debian-Ports Alpha. > > So what baseline do we want? Would EV56 be sufficient? Because that would > still work with my AlphaStation 433au and XP1000 and gets us BWX.
Yes. The first extension added is the byte-word extension which came in with EV56. That provides CPU instructions for byte and word (16-bit) memory accesses. That is the most important one: possibly a third of the bugs in the repository extend from non-atomic byte and word accesses. The kernel developers have expressed a view that they would like to assume on all arches that byte and word memory accesses are atomic and the only architecture that is holding them back from that assumption are old Alphas without BWX. There is an old open bug on gcc related to the non-atomic memory accesses of old Alphas and that one is basically cannot fix. If we went to BWX (i.e. EV56) then as you say that means the personal workstations (e.g. PWS433au and PWS500au), which a lot of Alpha users have and AlphaStations such as the 433au will still be supported. > I don't want to use something like EV67 as I think that would limit the > usable hardware too much. Yes, that's the problem going fully to EV67. The CPU extensions we would get are MVI (motion video instructions) that came in with PCA56, CIX (count integer instructions with the like of counting trailing zeros) that came in with EV67 and FIX (floating point extensions primarily for efficient conversion between float and integer and a sqrt instruction) with EV6, but these are nowhere near as important as BWX in terms of reducing bug fixing workload in maintaining the port. > I guess I can live with dropping EV4 since NetBSD > and Gentoo would still run on these. Gentoo has the advantage (and disadvantage) of compiling from source so one can optimise their own installation for their hardware. > I am still interested in fixing the glibc bug and will work on bisecting it. > > If EV56 is the baseline we can agree on, please go ahead and rebuild glibc > and gcc using this baseline. I am currently building gcc-12 to default to EV56/BWX. In the test suite now so probably won't be finished till tomorrow. Then I will try building latest glibc (2.36-6) with that gcc. I suspect there will still be a couple of test suite failures so there will probably be a further delay before I have it ready to upload to the repository. In any case I will give fair warning before I do. Cheers, Michael.