| Message ID | 20220112165016.226996-4-iii@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | target/s390x: Fix shift instructions | expand |
On 12.01.22 17:50, Ilya Leoshkevich wrote: > 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> > --- > target/s390x/tcg/cc_helper.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/target/s390x/tcg/cc_helper.c b/target/s390x/tcg/cc_helper.c > index c2c96c3a3c..c9b7b0e8c6 100644 > --- 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; Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/target/s390x/tcg/cc_helper.c b/target/s390x/tcg/cc_helper.c index c2c96c3a3c..c9b7b0e8c6 100644 --- 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;
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> --- target/s390x/tcg/cc_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)