From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-440388-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 1484 invoked by alias); 15 Jan 2014 07:23:50 -0000
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
Received: (qmail 1439 invoked by uid 48); 15 Jan 2014 07:23:44 -0000
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/59813] tail-call elimintation didn't fired with left-shift of char to cout
Date: Wed, 15 Jan 2014 07:23:00 -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: 4.8.2
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-59813-4-ZJuG1N5NH6@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-59813-4@http.gcc.gnu.org/bugzilla/>
References: <bug-59813-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2014-01/txt/msg01530.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59813

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
If you only care about tail recursion and not tail call optimization, perhaps,
but either solution would be very dumb.  We now have var ={v} {CLOBBER}; stmts,
even if those vars escape and are address taken, if there is a clobber stmt for
those vars on every path from the escape point to the tail call candidate, we
could perform tail recursion or tail call optimization, what we are really
after is that the address of no automatic variable from the current function
can escape to the tail recursion/call candidate.
As in:
void bar (char *);
void
foo (char *p)
{
  char c;
  bar (&c);
  bar (NULL); // We can't tail call optimize this
}

void
baz (char *p)
{
  {
    char c;
    bar (&c);
  }
  bar (NULL); // We could tail call optimize this
}