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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/115018] Incorrect data read/written at -O3 on aarch64
 with 256-bit SVE SIMD width specified
Date: Thu, 09 May 2024 21:05:49 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 13.2.0
X-Bugzilla-Keywords: wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115018

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
First I can't reproduce it with the official releases GCC 13.2.0.

Second with the trunk, I am not sure if this is a bug or not.

With the trunk with `-O3 -Wall -Wextra -fno-strict-aliasing -fwrapv
-fno-aggressive-loop-optimizations -march=3Darmv8.2-a+sve -msve-vector-bits=
=3D256 `
Running under qemu like this:

[apinski@xeond2 upstream-cross-aarch64]$ ./install-qemu/bin/qemu-aarch64 -c=
pu
max,sve128=3Don,sve256=3Don a.out
x[ 0]: 0 0 0
x[ 1]: 0 0 0
x[ 2]: 0 0 0
x[ 3]: 0 0 0
x[ 4]: 0 0 0
x[ 5]: 0 0 0
x[ 6]: 0 0 0
x[ 7]: 0 0 0
x[ 8]: 0 0 0
x[ 9]: 0 0 0
x[ 0]: 0 10 0
x[ 1]: 0 10 0
x[ 2]: 0 10 0
x[ 3]: 0 10 0
x[ 4]: 0 10 0
x[ 5]: 0 10 0
x[ 6]: 0 10 0
x[ 7]: 0 10 0
x[ 8]: 0 10 0
x[ 9]: 0 10 0


Works.
But if I enable SVE512, it fails like you are describing:
[apinski@xeond2 upstream-cross-aarch64]$ ./install-qemu/bin/qemu-aarch64 -c=
pu
max,sve128=3Don,sve256=3Don,sve512=3Don a.out
x[ 0]: 0 0 0
x[ 1]: 0 0 0
x[ 2]: 0 0 0
x[ 3]: 0 0 0
x[ 4]: 0 0 0
x[ 5]: 0 0 0
x[ 6]: 0 0 0
x[ 7]: 0 0 0
x[ 8]: 0 0 0
x[ 9]: 0 0 0
x[ 0]: 0 10 0
x[ 1]: 0 10 0
x[ 2]: 0 10 0
x[ 3]: 0 0 0
x[ 4]: 0 0 0
x[ 5]: 0 10 0
x[ 6]: 0 10 0
x[ 7]: 0 10 0
x[ 8]: 0 0 0
x[ 9]: 0 0 0=