[PATCH v2 01/17] vhost: use previous value atomic fetch operations

[Tyler Retzlaff]

Use __atomic_fetch_{add,and,or,sub,xor} instead of
__atomic_{add,and,or,sub,xor}_fetch when we have no interest in the
result of the operation.

Reduces unnecessary codegen that provided the result of the atomic
operation that was not used.

Change brings closer alignment with atomics available in C11 standard
and will reduce review effort when they are integrated.

Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com>
Acked-by: Morten Brørup <m...@smartsharesystems.com>
Reviewed-by: Maxime Coquelin <maxime.coque...@redhat.com>
---
 lib/vhost/virtio_net.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 51dc3c9..dc49a54 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -298,7 +298,7 @@
 
        vhost_log_cache_sync(dev, vq);
 
-       __atomic_add_fetch(&vq->used->idx, vq->shadow_used_idx,
+       __atomic_fetch_add(&vq->used->idx, vq->shadow_used_idx,
                           __ATOMIC_RELEASE);
        vq->shadow_used_idx = 0;
        vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
@@ -2311,7 +2311,7 @@
                        vhost_vring_call_packed(dev, vq);
                } else {
                        write_back_completed_descs_split(vq, n_descs);
-                       __atomic_add_fetch(&vq->used->idx, n_descs, 
__ATOMIC_RELEASE);
+                       __atomic_fetch_add(&vq->used->idx, n_descs, 
__ATOMIC_RELEASE);
                        vhost_vring_call_split(dev, vq);
                }
        } else {
@@ -3683,7 +3683,7 @@
                vhost_vring_call_packed(dev, vq);
        } else {
                write_back_completed_descs_split(vq, nr_cpl_pkts);
-               __atomic_add_fetch(&vq->used->idx, nr_cpl_pkts, 
__ATOMIC_RELEASE);
+               __atomic_fetch_add(&vq->used->idx, nr_cpl_pkts, 
__ATOMIC_RELEASE);
                vhost_vring_call_split(dev, vq);
        }
        vq->async->pkts_inflight_n -= nr_cpl_pkts;
-- 
1.8.3.1