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From: "jdx at o2 dot pl" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/109166] Built-in  __atomic_test_and_set does not seem to
 be atomic on ARMv4T
Date: Sun, 19 Mar 2023 13:57:38 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109166

--- Comment #5 from Jan Dubiec <jdx at o2 dot pl> ---
I read that thread a few days ago and I understand concerns regarding SWP, =
in
particular on ARMv6 which has made SWP obsolete (AFAIR it is optional on
ARMv6-A/R, ARMv6-M has neither SWP nor LDREX/STREX). However I have never h=
eard
of an ARMv4T based MCU which does not have SWP. So I do not understand why =
gcc
targeting various "bare metal" ARMs for ARMv4T a) emits non-atomic
__atomic_test_and_set, b) does not use SWP in that code. Especially that the
code attached to the linked message for ARMv4T uses SWP.=