tests/tcg/s390x: Test MVCRL with a large value in R0

Add a small test to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230704081506.276055-13-iii@linux.ibm.com>
[thuth: Apply fix for compiling with GCC 11]
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/tcg/s390x/mie3-mvcrl.c

@@ -1,29 +1,55 @@
+#include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
-
-static inline void mvcrl_8(const char *dst, const char *src)
+static void mvcrl(const char *dst, const char *src, size_t len)
 {
+    register long r0 asm("r0") = len;
+
     asm volatile (
-        "llill %%r0, 8\n"
         ".insn sse, 0xE50A00000000, 0(%[dst]), 0(%[src])"
-        : : [dst] "d" (dst), [src] "d" (src)
-        : "r0", "memory");
+        : : [dst] "d" (dst), [src] "d" (src), "r" (r0)
+        : "memory");
 }
 
-
-int main(int argc, char *argv[])
+static bool test(void)
 {
     const char *alpha = "abcdefghijklmnop";
 
     /* array missing 'i' */
-    char tstr[17] = "abcdefghjklmnop\0" ;
+    char tstr[17] = "abcdefghjklmnop\0";
 
     /* mvcrl reference use: 'open a hole in an array' */
-    mvcrl_8(tstr + 9, tstr + 8);
+    mvcrl(tstr + 9, tstr + 8, 8);
 
     /* place missing 'i' */
     tstr[8] = 'i';
 
-    return strncmp(alpha, tstr, 16ul);
+    return strncmp(alpha, tstr, 16ul) == 0;
+}
+
+static bool test_bad_r0(void)
+{
+    char src[256] = { 0 };
+
+    /*
+     * PoP says: Bits 32-55 of general register 0 should contain zeros;
+     * otherwise, the program may not operate compatibly in the future.
+     *
+     * Try it anyway in order to check whether this would crash QEMU itself.
+     */
+    mvcrl(src, src, (size_t)-1);
+
+    return true;
+}
+
+int main(void)
+{
+    bool ok = true;
+
+    ok &= test();
+    ok &= test_bad_r0();
+
+    return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 }