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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100076] eembc/automotive/basefp01 has 30.3%
 regression compare -O2 -ftree-vectorize with -O2 on CLX/Znver3
Date: Wed, 14 Apr 2021 05:28:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100076

--- Comment #2 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to H.J. Lu from comment #1)
> Is -O3 slower than -O3 -fno-tree-vectorize? If not, why?

For this case O3 is Ok, because O3 will enable pass_cunroll to complete unr=
oll
the loop1/loop2/loop3, and later pass_fre will elimiate redudant load of po=
lyX1
in loop2 and loop3 for both -O3 and -O3 -fno-tree-vectorize.=