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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/97770] [ICELAKE]Missing vectorization for
 vpopcnt
Date: Fri, 04 Jun 2021 07:41:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97770

--- Comment #15 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Richard Biener from comment #14)
> So we vectorize to
>=20
>   _18 =3D .POPCOUNT (vect__5.7_22);
>   _17 =3D .POPCOUNT (vect__5.7_21);
>   vect__6.8_16 =3D VEC_PACK_TRUNC_EXPR <_18, _17>;
>   _6 =3D 0;
>   _7 =3D dest_13(D) + _2;
>   vect__8.9_10 =3D [vec_unpack_lo_expr] vect__6.8_16;
>   vect__8.9_9 =3D [vec_unpack_hi_expr] vect__6.8_16;
>   _8 =3D (long long int) _6;
>=20
> which is exactly the issue that in the scalar code we have a 'int' produc=
ing
> popcount with long long argument but the vector IFN produces a result of =
the
> same width as the argument.  So the vectorizer compensates for that
> (VEC_PACK_TRUNC_EXPR) and then vectorizes the widening that's in the scal=
ar
> code (vec_unpack_{lo,hi}_expr).  The fix for this and for the missing
> byte and word variants is to add a pattern to tree-vect-patterns.c for th=
is
> case matching it to the .POPCOUNT internal function.  That possibly appli=
es
> to other bitops, too, like parity, ctz, ffs, etc.  There's quite some
> _widen helpers in the pattern recog code so I'm not sure how complicated
> it is to match
>=20
>  (long)popcountl(long)
>=20
> and
>=20
>  (short)popcount((int)short)
>=20
> Richard may have a good idea since he did the last "big" surgery there.

Any suggestion for this, should we change prototype of builtins or add
vec_recog_popcnt_pattern in vectorizer?=