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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/111794] RISC-V: Missed SLP optimization due to mask mode
 precision
Date: Fri, 13 Oct 2023 08:13:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111794

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'm failing to see the issue as with -march=3Drv64gcv I run into

t.c:4:8: missed:   not vectorized: relevant stmt not supported: *x_50(D) =
=3D _6;
t.c:4:8: note:   removing SLP instance operations starting from: *x_50(D) =
=3D _6;
t.c:4:8: missed:  not vectorized: bad operation in basic block.

but just guessing, the issue is bool pattern recognition and

t.c:12:1: note:   using normal nonmask vectors for _2 =3D _1 =3D=3D 1;
t.c:12:1: note:   using normal nonmask vectors for _4 =3D _3 =3D=3D 2;
t.c:12:1: note:   using normal nonmask vectors for _5 =3D _2 & _4;
...

?  To vectorize you'd want to see

t.c:12:1: note:   using boolean precision 32 for _2 =3D _1 =3D=3D 1;
t.c:12:1: note:   using boolean precision 16 for _4 =3D _3 =3D=3D 2;
t.c:12:1: note:   using boolean precision 16 for _5 =3D _2 & _4;
...

and a pattern used for the value use:

t.c:12:1: note:   extra pattern stmt: patt_62 =3D _5 ? 1 : 0;

You need to see why this doesn't work (it's a very delicate area).=