target/s390x: Fix cc_calc_sla_64() missing overflows

An overflow occurs for SLAG when at least one shifted bit is not equal
to sign bit. Therefore, we need to check that `shift + 1` bits are
neither all 0s nor all 1s. The current code checks only `shift` bits,
missing some overflows.

Fixes: cbe24bfa91d2 ("target-s390: Convert SHIFT, ROTATE SINGLE")
Co-developed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20220112165016.226996-4-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/target/s390x/tcg/cc_helper.c b/target/s390x/tcg/cc_helper.c
index c2c96c3..c9b7b0e 100644 (file)
--- a/target/s390x/tcg/cc_helper.c
+++ b/target/s390x/tcg/cc_helper.c
@@ -297,7 +297,7 @@ static uint32_t cc_calc_sla_32(uint32_t src, int shift)
 
 static uint32_t cc_calc_sla_64(uint64_t src, int shift)
 {
-    uint64_t mask = ((1ULL << shift) - 1ULL) << (64 - shift);
+    uint64_t mask = -1ULL << (63 - shift);
     uint64_t sign = 1ULL << 63;
     uint64_t match;
     int64_t r;