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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100366] spurious warning - std::vector::clear
 followed by std::vector::insert(vec.end(), ...) with -O2
Date: Wed, 12 May 2021 23:44:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100366

--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> ---
Just to clarify: when I said the warning is justified I meant that there is
nothing in the IL to keep the warning from triggering.  I.e., it works as
designed.  The problem may be solved by optimizing the code better, which m=
ight
be possible by enhancing the optimizers or by changing or annotating the
libstdc++ code to enable existing optimizations.  In the latter case it wil=
l of
course only help libstdc++ and not other code like it.  A third possibility=
 is
to make the warning itself smarter than the optimizer and figure out the co=
de
is unreachable without its help.=