Add a simple test to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---

Sorry, I just realized that in v2 that I sent the iteration count was
not increased. For v3 I've decided to bump it further to 1m, since it's
still fast enough:

$ time -p ./qemu-s390x ./tests/tcg/s390x-linux-user/cdsg
real 0.15

v2 -> v3: Increase iteration count to 1m.
v1 -> v2: Add cdsg() wrapper.

 tests/tcg/s390x/Makefile.target |  4 ++
 tests/tcg/s390x/cdsg.c          | 85 +++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 tests/tcg/s390x/cdsg.c

diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
index 1d454270c0e..523214dac33 100644
--- a/tests/tcg/s390x/Makefile.target
+++ b/tests/tcg/s390x/Makefile.target
@@ -27,6 +27,7 @@ TESTS+=noexec
 TESTS+=div
 TESTS+=clst
 TESTS+=long-double
+TESTS+=cdsg
 
 Z13_TESTS=vistr
 $(Z13_TESTS): CFLAGS+=-march=z13 -O2
@@ -66,3 +67,6 @@ sha512-mvx: sha512.c
 	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $< -o $@ $(LDFLAGS)
 
 TESTS+=sha512-mvx
+
+cdsg: CFLAGS+=-pthread
+cdsg: LDFLAGS+=-pthread
diff --git a/tests/tcg/s390x/cdsg.c b/tests/tcg/s390x/cdsg.c
new file mode 100644
index 00000000000..c7a5246181d
--- /dev/null
+++ b/tests/tcg/s390x/cdsg.c
@@ -0,0 +1,85 @@
+#include <assert.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+static volatile bool start;
+typedef unsigned long aligned_quadword[2] __attribute__((__aligned__(16)));
+static aligned_quadword val;
+static const int n_iterations = 1000000;
+
+static inline int cdsg(unsigned long *orig0, unsigned long *orig1,
+                       unsigned long new0, unsigned long new1,
+                       aligned_quadword *mem)
+{
+    register unsigned long r0 asm("r0");
+    register unsigned long r1 asm("r1");
+    register unsigned long r2 asm("r2");
+    register unsigned long r3 asm("r3");
+    int cc;
+
+    r0 = *orig0;
+    r1 = *orig1;
+    r2 = new0;
+    r3 = new1;
+    asm("cdsg %[r0],%[r2],%[db2]\n"
+        "ipm %[cc]"
+        : [r0] "+r" (r0)
+        , [r1] "+r" (r1)
+        , [db2] "+m" (*mem)
+        , [cc] "=r" (cc)
+        : [r2] "r" (r2)
+        , [r3] "r" (r3)
+        : "cc");
+    *orig0 = r0;
+    *orig1 = r1;
+
+    return (cc >> 28) & 3;
+}
+
+void *cdsg_loop(void *arg)
+{
+    unsigned long orig0, orig1, new0, new1;
+    int cc;
+    int i;
+
+    while (!start) {
+    }
+
+    orig0 = val[0];
+    orig1 = val[1];
+    for (i = 0; i < n_iterations;) {
+        new0 = orig0 + 1;
+        new1 = orig1 + 2;
+
+        cc = cdsg(&orig0, &orig1, new0, new1, &val);
+
+        if (cc == 0) {
+            orig0 = new0;
+            orig1 = new1;
+            i++;
+        } else {
+            assert(cc == 1);
+        }
+    }
+
+    return NULL;
+}
+
+int main(void)
+{
+    pthread_t thread;
+    int ret;
+
+    ret = pthread_create(&thread, NULL, cdsg_loop, NULL);
+    assert(ret == 0);
+    start = true;
+    cdsg_loop(NULL);
+    ret = pthread_join(thread, NULL);
+    assert(ret == 0);
+
+    assert(val[0] == n_iterations * 2);
+    assert(val[1] == n_iterations * 4);
+
+    return EXIT_SUCCESS;
+}
-- 
2.38.1