Check the CVD's and CVDG's corner cases.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/tcg/s390x/Makefile.target |  1 +
 tests/tcg/s390x/cvd.c           | 42 +++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 tests/tcg/s390x/cvd.c

diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
index 30994dcf9c2..04e4bddd83d 100644
--- a/tests/tcg/s390x/Makefile.target
+++ b/tests/tcg/s390x/Makefile.target
@@ -45,6 +45,7 @@ TESTS+=clc
 TESTS+=laalg
 TESTS+=add-logical-with-carry
 TESTS+=lae
+TESTS+=cvd
 
 cdsg: CFLAGS+=-pthread
 cdsg: LDFLAGS+=-pthread
diff --git a/tests/tcg/s390x/cvd.c b/tests/tcg/s390x/cvd.c
new file mode 100644
index 00000000000..4d12282c6aa
--- /dev/null
+++ b/tests/tcg/s390x/cvd.c
@@ -0,0 +1,42 @@
+/*
+ * Test the CONVERT TO DECIMAL instruction.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <stdint.h>
+
+static uint64_t cvd(int32_t x)
+{
+    uint64_t ret;
+
+    asm("cvd %[x],%[ret]" : [ret] "=R" (ret) : [x] "r" (x));
+
+    return ret;
+}
+
+static __uint128_t cvdg(int64_t x)
+{
+    __uint128_t ret;
+
+    asm("cvdg %[x],%[ret]" : [ret] "=T" (ret) : [x] "r" (x));
+
+    return ret;
+}
+
+int main(void)
+{
+    __uint128_t m = (((__uint128_t)0x9223372036854775) << 16) | 0x8070;
+
+    assert(cvd(0) == 0xc);
+    assert(cvd(1) == 0x1c);
+    assert(cvd(-1) == 0x1d);
+    assert(cvd(0x7fffffff) == 0x2147483647c);
+    assert(cvd(-0x7fffffff) == 0x2147483647d);
+
+    assert(cvdg(0) == 0xc);
+    assert(cvdg(1) == 0x1c);
+    assert(cvdg(-1) == 0x1d);
+    assert(cvdg(0x7fffffffffffffff) == (m | 0xc));
+    assert(cvdg(-0x7fffffffffffffff) == (m | 0xd));
+}
-- 
2.43.0