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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102622] [12 Regression] Wrong code with -O3
 for skylake-avx512 and icelake-server by r12-3903
Date: Wed, 06 Oct 2021 12:55:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102622

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Aldy Hernandez from comment #4)
> (In reply to Andrew Pinski from comment #3)
> > (In reply to Andrew Pinski from comment #2)
> > > Here is a slightly more reduced testcase (without the reasonable valu=
es):
> >=20
> > Looks like the store to var_22 was fully removed, I think this is not a
> > vectorizer bug really, but rather some issue with jump threading ....
>=20
> I'm getting an illegal instruction, so perhaps I don't have a machine with
> the appropriate hardware.  I even get the illegal instruction with
> -fno-thread-jumps:
>=20
> (base) abulafia:~/bld/t/gcc$ ./xg++ -B./ a.c -O3
> -L/usr/lib/gcc/x86_64-redhat-linux/11/ -march=3Dskylake-avx512=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20
> (base) abulafia:~/bld/t/gcc$ ./a.out
> Illegal instruction (core dumped)

You can download Intel SDE to run it:

https://software.intel.com/content/www/us/en/develop/articles/intel-softwar=
e-development-emulator.html

> Can you try with -fno-thread-jumps to make sure its really the threader at
> play?

I will give it a try.=