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Subject: [Bug tree-optimization/96271] Failure to optimize memcmp of doubles
 to avoid going through memory
Date: Sat, 16 Jan 2021 08:20:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96271

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:b673e7547fb95d1f0d5cd17ae9e3874742cade66

commit r11-6747-gb673e7547fb95d1f0d5cd17ae9e3874742cade66
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Jan 16 09:17:38 2021 +0100

    cd_dce: Return TODO_update_address_taken from last cd_dce [PR96271]

    On the following testcase, handle_builtin_memcmp in the strlen pass fol=
ds
    the memcmp into comparison of two MEM_REFs.  But nothing triggers updat=
ing
    of addressable vars afterwards, so even when the parameters are no long=
er
    address taken, we force the parameters to stack and back anyway.

    This patch causes TODO_update_address_taken to happen right before last
forwprop
    pass (at the end of last cd_dce), so after strlen1 too.

    2021-01-16  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/96271
            * passes.def: Pass false argument to first two pass_cd_dce
            instances and true to last instance.  Add comment that
            last instance rewrites no longer addressed locals.
            * tree-ssa-dce.c (pass_cd_dce): Add update_address_taken_p memb=
er
and
            initialize it.
            (pass_cd_dce::set_pass_param): New method.
            (pass_cd_dce::execute): Return TODO_update_address_taken from
            last cd_dce instance.

            * gcc.target/i386/pr96271.c: New test.=