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From: "juzhe.zhong at rivai dot ai" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/113583] Main loop in 519.lbm not vectorized.
Date: Wed, 24 Jan 2024 15:00:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113583

--- Comment #3 from JuzheZhong <juzhe.zhong at rivai dot ai> ---
Ok I see.

If we change NN into 8, then we can vectorize it with load_lanes/store_lanes
with group size =3D 8:

https://godbolt.org/z/doe9c3hfo

We will use vlseg8e64 which is RVVM1DF[8] =3D=3D RVVM1x8DFmode.

Here there is report:

/app/example.c:47:21: missed:   no array mode for RVVM1DF[20]
/app/example.c:47:21: missed:   no array mode for RVVM1DF[20]

I believe we enable vec_load_lanes/vec_store_lanes for RVVM1DF[20] which
RVVM1x20DF mode, then we can vectorize it.

But it's not reasonable and not general way to do that. This code require a=
rray
size =3D 20. How about other codes, we may have codes require array size  =
=3D 21,
22,..
23, ....etc... The array size can be any number. We can't leverage this
approach
for infinite array size.

So, the idea is that we try to find vec_load_lanes/vec_store_lanes first ch=
eck
whether it support lanes vectorization for specific array size.

If not, we should be able to lower them into multiple gather/scatter or str=
ided
load/stores.=