Dear Maintainer,
This bug causes data corruption in the ARM64 code compiled with Scalable Vector
Extensions (SVE) enabled for the 256-bit SVE processor but executed on 128-bit
SVE processors.
Example is AWS workload built for Graviton3, but executed on Graviton4.
When the compiler was compiling the ~ConstA (Not ConstA) expression to compute
the index into the vector it was actually computing -ConstA (minus ConstA),
e.g. ~4 instead of -5 produced -4.
Graviton 4 processes a 256-bit vector in two passes. For the second pass it
runs into this bug when computing indices into the second half of the vector
and ends up with {-4, -5, -6, -7}, processing the last element of the first
half twice and never touching the last element of the vector.
This data corruption may cause data loss, failing checksums, and potentially
security issues.
The upstream patch fixes the typo that caused this corruption.
In Ubuntu, the attached patch was applied to achieve the following:
* d/p/pr118976.diff: Fix memory corruption when executing 256-bit
Scalable Vector Extensions code on 128-bit CPUs (LP: #2101084).
Thanks for considering the patch.
We believe that the bug you reported is fixed in the latest version of
gcc-11, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to 1123631@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Matthias Klose <doko@debian.org> (supplier of updated gcc-11 package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Tue, 03 Mar 2026 09:59:37 +0100
Source: gcc-11
Architecture: source
Version: 11.5.0-10
Distribution: unstable
Urgency: medium
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Changed-By: Matthias Klose <doko@debian.org>
Closes: 1123631
Changes:
gcc-11 (11.5.0-10) unstable; urgency=medium
.
* Fix PR tree-optimization/118976, taken from the gcc-12 branch.
Closes: #1123631.
Checksums-Sha1:
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fcbea2ce31de844d22baaae3404f0b3a65735864 553452 gcc-11_11.5.0-10.debian.tar.xz
0cce0df7c8e71f44f8494529275a0872560808cf 9030 gcc-11_11.5.0-10_source.buildinfo
Checksums-Sha256:
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Files:
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20047d1c4a60a0a2ecc8f969a8cb6a0f 553452 devel optional gcc-11_11.5.0-10.debian.tar.xz
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