From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 2947D385802E; Wed,  3 Nov 2021 18:25:56 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2947D385802E
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/102876] GCC fails to use constant initialization even when
 it knows the value to initialize
Date: Wed, 03 Nov 2021 18:25:55 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 11.2.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: jakub at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: assigned_to bug_status attachments.created
Message-ID: <bug-102876-4-Gxap34qnrv@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-102876-4@http.gcc.gnu.org/bugzilla/>
References: <bug-102876-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 03 Nov 2021 18:25:56 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102876

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gn=
u.org
             Status|NEW                         |ASSIGNED

--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51731
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D51731&action=3Dedit
gcc12-pr102876.patch

Untested implementation of the optimization.
So far a little bit limited, either it handles initialization of the whole =
var
at once (usually scalar vars), or uses native_{encode,interpret}*
infrastructure
and in that case it can't handle unions or anything that needs relocations =
in
the initializers.  I guess in some cases it could be improved, but especial=
ly
unions can be harder or very hard if the access path is not visible in the
stores.=