On 1/11/24 15:55, Roger Sayle wrote:
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
--
I do think that if the regression is caused by HAVE_ATOMIC_TAS now being
detected as false due to a bugfix elsewhere as you kindly pointed out,
then the fix perhaps ought to change the compile-time behavior for TAS
alone.
As I point out in Bugzilla, we can get away with replacing the proposed
libatomic_la_LIBADD += $(addsuffix _1_2_.lo,$(SIZEOBJS))
with
libatomic_la_LIBADD += tas_1_2_.lo
so that we generate the missing `libat_test_and_set_1_i2' specifically.
I've not manage to detect the need for any other *_1_i2 thus far and
this alone appears sufficient to fix all observed regressions.
Happy to investigate further, but my initial findings seem to be that
this may be a better fix.
Let me know if you disagree ;).
Regards,
Victor
-----Original Message-----
From: Richard Earnshaw <richard.earns...@foss.arm.com>
Sent: 10 January 2024 15:34
To: Roger Sayle <ro...@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 <ro...@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.
