RE: [libatomic PATCH] Fix testsuite regressions on ARM [raspberry pi].

["Roger Sayle" <roger@nextmovesoftware.com>]

Hi Richard,
As you've recommended, this issue has now been filed in bugzilla
as PR other/113336.  As explained in the new PR, libatomic's testsuite
used to pass on armv6 (raspberry pi) in previous GCC releases, but
the code was incorrect/non-synchronous; this was reported as
PR target/107567 and PR target/109166.  Now that those issues
have been fixed, we now see that there's a missing dependency in
libatomic that's required to implement this functionality correctly.

I'm more convinced that my fix is correct, but it's perhaps a little
disappointing that libatomic doesn't have a (multi-threaded) run-time
test to search for race conditions, and confirm its implementations
are correctly serializing.

Please let me know what you think.
Best regards,
Roger
--

> -----Original Message-----
> From: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>
> Sent: 10 January 2024 15:34
> To: Roger Sayle <roger@nextmovesoftware.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [libatomic PATCH] Fix testsuite regressions on ARM [raspberry pi].
> 
> 
> 
> On 08/01/2024 16:07, Roger Sayle wrote:
> >
> > Bootstrapping GCC on arm-linux-gnueabihf with --with-arch=armv6
> > currently has a large number of FAILs in libatomic (regressions since
> > last time I attempted this).  The failure mode is related to IFUNC
> > handling with the file tas_8_2_.o containing an unresolved reference
> > to the function libat_test_and_set_1_i2.
> >
> > Bearing in mind I've no idea what's going on, the following one line
> > change, to build tas_1_2_.o when building tas_8_2_.o, resolves the
> > problem for me and restores the libatomic testsuite to 44 expected
> > passes and 5 unsupported tests [from 22 unexpected failures and 22 unresolved
> testcases].
> >
> > If this looks like the correct fix, I'm not confident with rebuilding
> > Makefile.in with correct version of automake, so I'd very much
> > appreciate it if someone/the reviewer/mainainer could please check this in for
> me.
> > Thanks in advance.
> >
> >
> > 2024-01-08  Roger Sayle  <roger@nextmovesoftware.com>
> >
> > libatomic/ChangeLog
> >          * Makefile.am: Build tas_1_2_.o on ARCH_ARM_LINUX
> >          * Makefile.in: Regenerate.
> >
> >
> > Roger
> > --
> >
> 
> Hi Roger,
> 
> I don't really understand all this make foo :( so I'm not sure if this is the right fix
> either.  If this is, as you say, a regression, have you been able to track down when
> it first started to occur?  That might also help me to understand what changed to
> cause this.
> 
> Perhaps we should have a PR for this, to make tracking the fixes easier.
> 
> R.