Re: [PING][PATCH 0/3] Small step in supporting AVX instructions

[Guinevere Larsen <blarsen@redhat.com>]

On 6/6/24 05:16, Willgerodt, Felix wrote:
>> -----Original Message-----
>> From: Guinevere Larsen <blarsen@redhat.com>
>> Sent: Dienstag, 4. Juni 2024 21:10
>> To: Guinevere Larsen <blarsen@redhat.com>; gdb-patches@sourceware.org
>> Subject: [PING][PATCH 0/3] Small step in supporting AVX instructions
>>
>> Ping!
>>
>> Since this patch is only x86 record full, if there are no comments until
>> next week, I will push this change.
>>
>> --
>> Cheers,
>> Guinevere Larsen
>> She/Her/Hers
>>
> I didn't yet find the time to review this, nor do I really have much expertise
> in VEX nor record full. I also don't really know if/when I will find the time.
> But if you are confident enough I would be ok to merging this, after skimming
> over it once, I didn't see much beyond what Tom already pointed out.
>
>
> What I did is run some testing on your patches. I found this failure on two nodes
> (Fedora 39 and Ubuntu 22.04, just using gcc and unix.exp and parallel testing):
>
> (gdb) PASS: gdb.reverse/step-precsave.exp: breakpoint at end of main
> continue^M
> Continuing.^M
> Process record does not support VEX instruction 0x78 at address 0x7ffff7e53315.^M
> Process record: inferior program stopped.^M
> ^M
> Program stopped.^M
> 0x00007ffff7e53315 in __memset_avx2_unaligned_erms () from /lib64/libc.so.6^M
> (gdb) FAIL: gdb.reverse/step-precsave.exp: run to end of main
>
>
> Though I didn't see this when I ran it manually on a different Ubuntu 22.04 node.
> There I saw this:
>
> (gdb) PASS: gdb.reverse/step-precsave.exp: breakpoint at end of main
> continue^M
> Continuing.^M
> Process record does not support instruction bound.^M
> Process record does not support instruction 0x62 at address 0x7ffff7f289c7.^M
> Process record: failed to record execution log.^M
> ^M
> Program stopped.^M
> 0x00007ffff7f289c7 in __memset_evex_unaligned_erms () at ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:182^M
> warning: 182    ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S: No such file or directory^M
> (gdb) KFAIL: gdb.reverse/step-precsave.exp: run to end of main (PRMS: record/30807)
>
> I didn't have the time to investigate further. Not sure if the error messages tell you enough.

Yeah, that's enough to give me a sense of what's up. These are the 
motivators for this series (though the second one is further in the 
future). GDB doesn't know how to disassemble AVX, AVX2 and AVX512 
instructions, which is what leads to "process record does not support 
(...)".

The KFAIL (second error) is with regard to AVX-512, identified by the 
prefix 0x62. The first one used to have a KFAIL too, but I changed the 
output message so now it just shows up as FAIL (used to point to 
https://sourceware.org/bugzilla/show_bug.cgi?id=23188). I will update 
the step-precsave regexp to identify the current issue and emit a KFAIL 
again.

> I can help if you want to know more about the CPUs or libraries.
> Note that the two machines where it failed, it didn't fail for master.
I don't understand how it could have passed on the same machines. I'm 
more curious about the output when it did pass, if you still have it. 
Did it use a different path for memset?

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

>
> Regards,
> Felix
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