[glibc] x86: Expand the comment on when REP STOSB is used on memset

[glibc] x86: Expand the comment on when REP STOSB is used on memset

[H.J. Lu]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=491e55beab7457ed310a4a47496f4a333c5d1032

commit 491e55beab7457ed310a4a47496f4a333c5d1032
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Feb 8 10:08:40 2024 -0300

    x86: Expand the comment on when REP STOSB is used on memset
    
    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Diff:
---
 sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
index 9984c3ca0f..97839a2248 100644
--- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
@@ -21,7 +21,9 @@
    2. If size is less than VEC, use integer register stores.
    3. If size is from VEC_SIZE to 2 * VEC_SIZE, use 2 VEC stores.
    4. If size is from 2 * VEC_SIZE to 4 * VEC_SIZE, use 4 VEC stores.
-   5. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with
+   5. On machines ERMS feature, if size is greater or equal than
+      __x86_rep_stosb_threshold then REP STOSB will be used.
+   6. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with
       4 VEC stores and store 4 * VEC at a time until done.  */
 
 #include <sysdep.h>