[Bug target/104610] memcmp () == 0 can be optimized better for avx512f

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104610

--- Comment #13 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Hongtao.liu from comment #8)
> Created attachment 52495 [details]
> untested patch.

I see these regressions with -m32:

FAIL: gcc.dg/lower-subreg-1.c scan-rtl-dump subreg1 "Splitting reg"
FAIL: gcc.target/i386/iamcu/test_basic_64bit_returning.c execution,  -O0 
FAIL: gcc.target/i386/iamcu/test_basic_64bit_returning.c execution,  -O1 
FAIL: gcc.target/i386/iamcu/test_basic_64bit_returning.c execution,  -O2 
FAIL: gcc.target/i386/iamcu/test_basic_64bit_returning.c execution,  -O3 -g 
FAIL: gcc.target/i386/iamcu/test_basic_64bit_returning.c execution,  -Os 
FAIL: gcc.target/i386/iamcu/test_struct_returning.c execution,  -O0 
FAIL: gcc.target/i386/iamcu/test_struct_returning.c execution,  -O1 
FAIL: gcc.target/i386/iamcu/test_struct_returning.c execution,  -Og -g