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Re: Bug#1036158: gcc-13: Please raise baseline for alpha to EV56

Hi all,

On 17.05.23 11:27, John Paul Adrian Glaubitz wrote:

Hi Michael!

On Tue, 2023-05-16 at 20:25 +1200, Michael Cree wrote:

On Tue, May 16, 2023 at 09:38:56AM +0200, John Paul Adrian Glaubitz wrote:

After a long discussion on IRC and the mailing list, we have agreed to raise the
baseline for the alpha architecture to EV56 to improve the generated code and fix
a number of issues. The change is already being implemented in the glibc packages
which switches to EV56 [1] since hwcaps are no longer available with glibc 2.37 [2].

Could you raise the baseline for gcc on alpha to EV56?

I assume, it should be "--with-cpu=ev56" or "--with-arch=ev56".


Yes, please!

I suggest the following in debian/rules2:

ifneq (,$(findstring alpha,$(DEB_TARGET_ARCH)))
   CONFARGS += --with-cpu=ev56 --with-tune=ev6
endif

(the --with-tune only affects instruction scheduling and better tunes
code for ev6 and more recent machines, but allows execution down to
ev56.)  I have tested this in the past with a rebuild of most packages
that are in the base essential chroot in the past and it works well.


Doesn't that come with a speed penalty for EV56 machines? I'm asking because EV56 is
currently the baseline for QEMU when emulating Alpha.


How high will it be? I have some numbers from my PWS 500au for 7z 16.02
and openssl 3.0.7, so we could compare that later on.

With everything below EV56 dropped, I'd say let's get everything out of
the later (real) machines and use "ev67" here. Even my DS20E already
uses EV67s.

UPDATE: Reading through [1] and [2], it looks like there's no difference
between EV6 and EV67 for instruction scheduling. So fine as proposed.

[1]: https://gcc.gnu.org/onlinedocs/gcc/DEC-Alpha-Options.html
[2]:
https://uprrp2.uprrp.edu/help?key=SQLPRE72~SQLPRE_Command_Line~Arguments~ARCHITECTURE&title=VMS%20Help&referer=

Cheers,
Frank
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