tree 8b7e6f36b177d2de6195c7d3bd2d292c542ba67e
parent 7b3b2f50953c5143d4b14b59d322d8a793f411dd
author Jinyang He <hejinyang@loongson.cn> 1668667132 +0800
committer Lulu Cheng <chenglulu@loongson.cn> 1668754947 +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.