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From: "hubicka at kam dot mff.cuni.cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/105728] dead store to static var not optimized out
Date: Wed, 25 May 2022 16:21:37 +0000	[thread overview]
Message-ID: <bug-105728-4-8EU5PoQZTy@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-105728-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105728

--- Comment #1 from hubicka at kam dot mff.cuni.cz ---
> To me, all of these do the same thing and should generate the same code.
> As nobody else can see removeme, and we aren't leaking its address, shouldn't
> the compiler be able to deduce that all accesses to removeme are
> inconsequential and can be removed?
> 
> My gcc 11.3 generates a condidion and a store and a return 0 for dummy1, the
> same thing for dummy2, but for dummy3 it understands that it only needs to emit
> a return 0.

GCC detects "write olny" variables and that is what matches for dummy3.
I am not 100% sure it is valid to do the optimization in other two cases
since when multiple threads are considered. In any case we lack tracking
of constants stored to global variables which is something ipa-cp can be
extended to.

Honza

  parent reply	other threads:[~2022-05-25 16:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-25 14:14 [Bug c/105728] New: " felix-gcc at fefe dot de
2022-05-25 16:21 ` Jan Hubicka
2022-05-25 16:21 ` hubicka at kam dot mff.cuni.cz [this message]
2022-05-27  6:25 ` [Bug ipa/105728] " rguenth at gcc dot gnu.org
2022-05-27 12:24 ` rguenth at gcc dot gnu.org
2022-05-27 13:16 ` felix-gcc at fefe dot de

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