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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/110557] [13/14 Regression] Wrong code for
 x86_64-linux-gnu with -O3 -mavx2: vectorized loop mishandles signed
 bit-fields
Date: Mon, 10 Jul 2023 10:36:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110557

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Xi Ruoyao <xry111@gcc.gnu.org>:

https://gcc.gnu.org/g:63ae6bc60c0f67fb2791991bf4b6e7e0a907d420

commit r14-2407-g63ae6bc60c0f67fb2791991bf4b6e7e0a907d420
Author: Xi Ruoyao <xry111@xry111.site>
Date:   Thu Jul 6 23:08:57 2023 +0800

    vect: Fix vectorized BIT_FIELD_REF for signed bit-fields [PR110557]

    If a bit-field is signed and it's wider than the output type, we must
    ensure the extracted result sign-extended.  But this was not handled
    correctly.

    For example:

        int x : 8;
        long y : 55;
        bool z : 1;

    The vectorized extraction of y was:

        vect__ifc__49.29_110 =3D
          MEM <vector(2) long unsigned int> [(struct Item *)vectp_a.27_108];
        vect_patt_38.30_112 =3D
          vect__ifc__49.29_110 & { 9223372036854775552, 9223372036854775552=
 };
        vect_patt_39.31_113 =3D vect_patt_38.30_112 >> 8;
        vect_patt_40.32_114 =3D
          VIEW_CONVERT_EXPR<vector(2) long int>(vect_patt_39.31_113);

    This is obviously incorrect.  This pach has implemented it as:

        vect__ifc__25.16_62 =3D
          MEM <vector(2) long unsigned int> [(struct Item *)vectp_a.14_60];
        vect_patt_31.17_63 =3D
          VIEW_CONVERT_EXPR<vector(2) long int>(vect__ifc__25.16_62);
        vect_patt_32.18_64 =3D vect_patt_31.17_63 << 1;
        vect_patt_33.19_65 =3D vect_patt_32.18_64 >> 9;

    gcc/ChangeLog:

            PR tree-optimization/110557
            * tree-vect-patterns.cc (vect_recog_bitfield_ref_pattern):
            Ensure the output sign-extended if necessary.

    gcc/testsuite/ChangeLog:

            PR tree-optimization/110557
            * g++.dg/vect/pr110557.cc: New test.=