ringtest: use link-time optimization

By using -flto and -fwhole-program, all functions from the ring implementation
can be treated as static and possibly inlined.  Force this to happen through
the GCC flatten attribute.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio/ringtest/Makefile

@@ -3,8 +3,8 @@ all:
 all: ring virtio_ring_0_9 virtio_ring_poll virtio_ring_inorder ptr_ring noring
 
 CFLAGS += -Wall
-CFLAGS += -pthread -O2 -ggdb
-LDFLAGS += -pthread -O2 -ggdb
+CFLAGS += -pthread -O2 -ggdb -flto -fwhole-program
+LDFLAGS += -pthread -O2 -ggdb -flto -fwhole-program
 
 main.o: main.c main.h
 ring.o: ring.c main.h

tools/virtio/ringtest/main.c

@@ -96,7 +96,7 @@ void set_affinity(const char *arg)
 	assert(!ret);
 }
 
-static void run_guest(void)
+static void __attribute__((__flatten__)) run_guest(void)
 {
 	int completed_before;
 	int completed = 0;
@@ -149,7 +149,7 @@ static void run_guest(void)
 	}
 }
 
-static void run_host(void)
+static void __attribute__((__flatten__)) run_host(void)
 {
 	int completed_before;
 	int completed = 0;