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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111791] RISC-V: Strange loop vectorizaion on
 popcount function
Date: Wed, 18 Oct 2023 23:17:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111791

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Vineet Gupta from comment #5)
> (In reply to Robin Dapp from comment #4)
>=20
> > Analyzing loop at pr111791.c:8
> > pr111791.c:8:25: note:  =3D=3D=3D analyze_loop_nest =3D=3D=3D
> > pr111791.c:8:25: note:   =3D=3D=3D vect_analyze_loop_form =3D=3D=3D
> > pr111791.c:8:25: note:    =3D=3D=3D get_loop_niters =3D=3D=3D
> > Matching expression match.pd:1919, generic-match-8.cc:27
> > Applying pattern match.pd:1975, generic-match-2.cc:4670
> > Matching expression match.pd:2707, generic-match-4.cc:36
> > Matching expression match.pd:2710, generic-match-3.cc:53
> > Matching expression match.pd:2717, generic-match-2.cc:23
> > Matching expression match.pd:2707, generic-match-4.cc:36
> > Matching expression match.pd:2710, generic-match-3.cc:53
> > Matching expression match.pd:2717, generic-match-2.cc:23
> > Matching expression match.pd:2707, generic-match-4.cc:36
> > Matching expression match.pd:2710, generic-match-3.cc:53
> > Matching expression match.pd:2717, generic-match-2.cc:23
> > Matching expression match.pd:148, generic-match-10.cc:27
> > Matching expression match.pd:148, generic-match-10.cc:27
> > Applying pattern match.pd:4519, generic-match-4.cc:2923
> > Applying pattern match.pd:201, generic-match-4.cc:3103
> > Applying pattern match.pd:3393, generic-match-2.cc:182
> > pr111791.c:8:25: note:   Symbolic number of iterations is (unsigned int=
D.4)
> > __builtin_popcountlD.1952 (value_4(D))
>=20
> Curious, how did you get this debug output - is this just one of
> -fdump-tree-?

The `applying pattern`/`matching expression` comes from `-folding` option of
`-fdump-tree-`. It is enabled with `-all` at the end too.
So in this case it looks like it was:
`-fdump-tree-vect-all` since both __builtin_popcount and the type `unsigned
int` has the decl ID at the end (that is what `D.4` and `D.1952` are).=