Re: [PATCH] [alpha] adjust MEM alignment for block move [PR115459] (was: Re: [PATCH v2] [PR100106] Reject unaligned subregs when strict alignment is required)

["Maciej W. Rozycki" <macro@orcam.me.uk>]

On Thu, 13 Jun 2024, Maciej W. Rozycki wrote:

> > Maciej, would you be so kind as to give it a spin with a native
> > regstrap?  TIA,
> 
>  I will certainly run regression-testing once the job I started yesterday 
> has finished with my Alpha system, which should be fairly soon as it's 
> already well into libstdc++ testing.

 This has now completed successfully, with no regressions observed across 
all the GCC and library testsuites other than the gnat one.

 The gnat one obviously couldn't be run without the fix in place, not even 
in a build without libada, because it depends on gnattools, which in turn 
need libada.  Results with the change applied appear reasonable however, 
though they are not completely clean.  I trigerred issues while running 
this part of the testsuite and I have now posted a proposed fix, at: 
<https://inbox.sourceware.org/gcc-patches/alpine.DEB.2.21.2406161338480.9248@angie.orcam.me.uk/T/>.

 Also one of the libstdc++ test cases caused to lock the target machine up 
regardless of the fix due to memory exhaustion which took me some time to 
investigate and sort out (now dealt with `ulimit -d'), and a testsuite run 
takes 24 hours almost exactly, hence the total amount of time it took me 
to complete this verification.

>  I cannot make a native bootstrap however as I have only just set up my 
> Alpha to run at all and it has a very rudimentary and outdated userland, 
> suitable for remote regression testing only.  It's NFS-rooted too and due 
> to a failure in my lab last month I may not be able to recover from before 
> August it runs over backup 10Mbps Ethernet rather than intended 100Mbps 
> FDDI, so I can imagine performance would be abysmal even if I brought the 
> userland up to date.
> 
>  However Adrian (cc-ed) has recently told me he could be running all kinds 
> of stuff with his Alpha.  Adrian, would you be able to verify Alexandre's 
> proposed fix in a native regstrap?

 We've exchanged with Adrian a couple of messages off-list and I'm not 
sure after all whether he'll be able to run such a regstrap.  Given that 
this fix has addressed a problem affecting building a part of the compiler 
itself and the overall status of the Alpha port I do hope it can go ahead 
based on cross-compilation verification only.  Several of our targets are 
routinely verified in such a manner only.

 FAOD I run my builds with `--enable-werror-always' requested to have 
`-Werror' included in the compilation options just as a native regstrap 
has, so this part of verification has been covered as well.

  Maciej