Let's increment the length once.
While at it, cleanup the comment. The memset() example is given as a
programming note in the PoP, so drop the description.
Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
target/s390x/mem_helper.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index 2e22c183bd..2bc2cd09c1 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -320,16 +320,20 @@ static uint32_t do_helper_mvc(CPUS390XState *env,
uint32_t l, uint64_t dest,
HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
__func__, l, dest, src);
- /* mvc and memmove do not behave the same when areas overlap! */
- /* mvc with source pointing to the byte after the destination is the
- same as memset with the first source byte */
+ /* MVC always copies one more byte than specified - maximum is 256 */
+ l++;
+
+ /*
+ * "When the operands overlap, the result is obtained as if the operands
+ * were processed one byte at a time". Only non-destructive overlaps
+ * behave like memmove().
+ */
if (dest == src + 1) {
- fast_memset(env, dest, cpu_ldub_data_ra(env, src, ra), l + 1, ra);
- } else if (dest < src || src + l < dest) {
- fast_memmove(env, dest, src, l + 1, ra);
+ fast_memset(env, dest, cpu_ldub_data_ra(env, src, ra), l, ra);
+ } else if (dest < src || src + l <= dest) {
+ fast_memmove(env, dest, src, l, ra);
} else {
- /* slow version with byte accesses which always work */
- for (i = 0; i <= l; i++) {
+ for (i = 0; i < l; i++) {
uint8_t x = cpu_ldub_data_ra(env, src + i, ra);
cpu_stb_data_ra(env, dest + i, x, ra);
}
--
2.21.0
