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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/106476] ICE generating FOLD_EXTRACT_LAST
Date: Thu, 15 Sep 2022 12:08:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106476

--- Comment #2 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.or=
g> ---
(In reply to Richard Biener from comment #1)
> I think EXTRACT_LAST_REDUCTION cannot simply do
>=20
>    /* Instead of doing ~x ? y : z do x ? z : y.  */
>    vec_compare =3D new_temp;
>    std::swap (vec_then_clause, vec_else_clause);
>=20
> So either the fix could be to not support bitop2 =3D=3D BIT_NOT_EXPR for
> EXTRACT_LAST_REDUCTION or we have to perform the BIT_NOT_EXPR as
> vector operation.
>=20
> Richard?
Agreed.  This case seems to be specific to EQ_EXPR on booleans,
and I'm not sure why we can't just emit an EQ_EXPR for that case.
Anything else would lead to redundant ops for EXTRACT_LAST_REDUCTION.

There again, having (predicate, predicate =E2=86=92 predicate) comparisons =
for
EQ_EXPR might be a weird special case, and might be similar to having
things like NAND and NOR (which we deliberately don't have).  So maybe
emitting the separate NOT_EXPR is better after all.=