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From: "zeranoe at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/100366] [11/12/13 Regression] spurious
 warning - std::vector::clear followed by std::vector::insert(vec.end(), ...)
 with -O2
Date: Sat, 26 Nov 2022 15:53:12 +0000
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X-Bugzilla-Component: tree-optimization
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X-Bugzilla-Keywords: diagnostic, missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100366

Kyle Schwarz <zeranoe at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |zeranoe at gmail dot com

--- Comment #14 from Kyle Schwarz <zeranoe at gmail dot com> ---
I also ran into this with:
> auto data =3D std::make_shared<std::vector<uint8_t>>();
> data->insert(data->end(), {0xAA, 0xBB, 0xCC});

I do not hit it with:
> std::vector<uint8_t> data;
> data.insert(data.end(), {0xAA, 0xBB, 0xCC});

Bisecting shows it was introduced with
81d6cdd335ffc60c216a020d5c99306f659377a2. In gcc/gimple-ssa-warn-access.cc
pass_waccess::check() there's now a call to the new
pass_waccess::check_builtin() which throws this warning (BUILT_IN_MEMMOVE,
check_memop_access()). The old behavior had these checks scattered througho=
ut
builtins.c but now with it being part of pass_waccess::check() it is called=
 for
each bb as part of pass_waccess::execute().=