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s390x/tcg: MVC: Increment the length once

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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.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
This commit is contained in:
David Hildenbrand 2019-08-21 10:04:19 +02:00
parent f1c2e27cb5
commit d573ffde0c
1 changed files with 12 additions and 8 deletions
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20
target/s390x/mem_helper.c
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@ -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);
}