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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 rtl-optimization/114211] [13 Regression] wrong code with -O
 -fno-tree-coalesce-vars since r13-1907
Date: Fri, 15 Mar 2024 23:29:15 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114211

--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:df3994a1be3565ad450d552dc94b696748a7807a

commit r13-8447-gdf3994a1be3565ad450d552dc94b696748a7807a
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Mar 5 10:32:38 2024 +0100

    lower-subreg: Fix ROTATE handling [PR114211]

    On the following testcase, we have
    (insn 10 7 11 2 (set (reg/v:TI 106 [ h ])
            (rotate:TI (reg/v:TI 106 [ h ])
                (const_int 64 [0x40]))) "pr114211.c":8:5 1042
{rotl64ti2_doubleword}
         (nil))
    before subreg1 and the pass decides to use
    (reg:DI 127 [ h ]) / (reg:DI 128 [ h+8 ])
    register pair instead of (reg/v:TI 106 [ h ]).
    resolve_operand_for_swap_move_operator implements it by pretending it is
    an assignment from
    (concatn (reg:DI 127 [ h ]) (reg:DI 128 [ h+8 ]))
    to
    (concatn (reg:DI 128 [ h+8 ]) (reg:DI 127 [ h ]))
    The problem is that if the rotate argument is the same as destination or
    if there is even an overlap between the first half of the destination w=
ith
    second half of the source we emit incorrect code, because the store to
    (reg:DI 128 [ h+8 ]) overwrites what we need for source of the second
    move.  The following patch detects that case and uses a temporary pseudo
    to hold the original (reg:DI 128 [ h+8 ]) value across the first store.

    2024-03-05  Jakub Jelinek  <jakub@redhat.com>

            PR rtl-optimization/114211
            * lower-subreg.cc (resolve_simple_move): For double-word
            rotates by BITS_PER_WORD if there is overlap between source
            and destination use a temporary.

            * gcc.dg/pr114211.c: New test.

    (cherry picked from commit aed445b0fd0c7ed16124c61e7eb732992426f103)=