Fix BOF in the last channel handling logic of SSE ShuffleChannel

[junwha]

Fix #5734

• apply SSE logic until size-1
• apply linear logic for the last n elements

[tencent-adm]

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❌ junwha
❌ nihui
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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.58%. Comparing base (8c18666) to head (0d663ae).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5735      +/-   ##
==========================================
- Coverage   93.59%   93.58%   -0.01%     
==========================================
  Files         933      933              
  Lines      299557   299664     +107     
==========================================
+ Hits       280360   280446      +86     
- Misses      19197    19218      +21     

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[junwha]

Hi @nihui,
Thank you for the fast response and review!
I will reflect the unrolling part.

Could I ask why do you think the out-of-bound risk does not exist in pack8/16 codes?
As far as I think, it also accesses (start of the channel) + (size-1)*(element size) + (element size)/2 in the same manner, which is beyond the size of the channel.

Thank you for your effort on this issue!

[nihui]

Thanks for your contribution !