[Bug target/107713] Wrong implementation atomic_exchange<short> on LoongArch
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri Nov 18 07:05:20 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107713
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by LuluCheng <chenglulu@gcc.gnu.org>:
https://gcc.gnu.org/g:f0024bfb228f94e60e06dc32a4983e40a9b90be5
commit r13-4136-gf0024bfb228f94e60e06dc32a4983e40a9b90be5
Author: Jinyang He <hejinyang@loongson.cn>
Date: Thu Nov 17 14:38:52 2022 +0800
LoongArch: Fix atomic_exchange expanding [PR107713]
We used to expand atomic_exchange_n(ptr, new, mem_order) for subword types
into something like:
{
__typeof__(*ptr) t = atomic_load_n(ptr, mem_order);
atomic_compare_exchange_n(ptr, &t, new, true, mem_order, mem_order);
return t;
}
It's incorrect because another thread may store a different value into *ptr
after atomic_load_n. Then atomic_compare_exchange_n will not store into
*ptr, but atomic_exchange_n should always perform the store.
gcc/ChangeLog:
PR target/107713
* config/loongarch/sync.md
(atomic_cas_value_exchange_7_<mode>): New define_insn.
(atomic_exchange): Use atomic_cas_value_exchange_7_si instead of
atomic_cas_value_cmp_and_7_si.
gcc/testsuite/ChangeLog:
PR target/107713
* gcc.target/loongarch/pr107713-1.c: New test.
* gcc.target/loongarch/pr107713-2.c: New test.
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