Comment 7 for bug 2001932

(In reply to H.J. Lu from comment #5)
> (In reply to Sunil Pandey from comment #4)
> > Created attachment 12601 [details]
> > strncmp_avx2 patch for pr25933
> >
> > Tested attached patch on
> >
> > https://gitlab.com/x86-glibc/glibc/-/commits/users/hjl/pr25933/master
>
> Looks good. Please try this
>
> diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> index 48d03a9f46..dabc3e7590 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> @@ -256,6 +256,11 @@ L(next_3_vectors):
> vpmovmskb %ymm0, %ecx
> testl %ecx, %ecx
> jne L(return_3_vec_size)
> +# ifdef USE_AS_STRNCMP
> + /* Check if VEC_SIZE * 4 already exceeded max compare count %r11 */
> + cmpq $(VEC_SIZE * 4), %r11
> + jbe L(zero)
> +# endif
> L(main_loop_header):
> leaq (VEC_SIZE * 4)(%rdi), %rdx
> movl $PAGE_SIZE, %ecx

It fixes the issue on my setup as expected.

$ ./test-strncmp
                        simple_strncmp stupid_strncmp __strncmp_avx2 __strncmp_sse42 __strncmp_ssse3 __strncmp_sse2
$ echo $?
0

$ git diff
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 48d03a9f46..84ffe2cd5c 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -256,6 +256,11 @@ L(next_3_vectors):
        vpmovmskb %ymm0, %ecx
        testl %ecx, %ecx
        jne L(return_3_vec_size)
+# ifdef USE_AS_STRNCMP
+ /* Check if VEC_SIZE * 4 already exceeded max compare count %r11 */
+ cmpq $(VEC_SIZE * 4), %r11
+ jbe L(zero)
+# endif
 L(main_loop_header):
        leaq (VEC_SIZE * 4)(%rdi), %rdx
        movl $PAGE_SIZE, %ecx