From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-327161-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 30035 invoked by alias); 7 Aug 2010 16:25:51 -0000
Received: (qmail 29943 invoked by uid 48); 7 Aug 2010 16:25:35 -0000
Date: Sat, 07 Aug 2010 16:25:00 -0000
Message-ID: <20100807162535.29942.qmail@sourceware.org>
X-Bugzilla-Reason: CC
References: <bug-45221-17658@http.gcc.gnu.org/bugzilla/>
Subject: [Bug c++/45221] missed optimization with multiple bases and casting
In-Reply-To: <bug-45221-17658@http.gcc.gnu.org/bugzilla/>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org
From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2010-08/txt/msg00534.txt.bz2



------- Comment #8 from rguenth at gcc dot gnu dot org  2010-08-07 16:25 -------
Which means that if the language guarantees that for

Base2* fooA(Derived* x)
{
    Base2& y = *x;
    return &y;
}

x being a null pointer invokes undefined behavior (because references can't
bind to nothing(?)) then the frontend should emit not

<<cleanup_point   struct Base2 & y = (struct Base2 &) (NON_LVALUE_EXPR <x> !=
0B ? &NON_LVALUE_EXPR <x>->D.1702 : 0B);>>;

but instead

<<cleanup_point   struct Base2 & y = (struct Base2 &) &NON_LVALUE_EXPR
<x>->D.1702;>>;

CCing Jason.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45221