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Date: Thu, 08 May 2003 18:52:00 -0000
Message-ID: <20030508185226.1292.qmail@sources.redhat.com>
To: Joerg-Cyril.Hoehle@T-Systems.com, bruno@clisp.org, gcc-bugs@gcc.gnu.org,
  gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org, sds@gnu.org
From: ehrhardt@mathematik.uni-ulm.de
Reply-To: ehrhardt@mathematik.uni-ulm.de, Joerg-Cyril.Hoehle@T-Systems.com,
  bruno@clisp.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org,
  nobody@gcc.gnu.org, sds@gnu.org, gcc-gnats@gcc.gnu.org
Subject: Re: optimization/10684: register variable update disappears when using -O
X-SW-Source: 2003-05/txt/msg00638.txt.bz2
List-Id: <gcc-prs.sourceware.org>

Synopsis: register variable update disappears when using -O

State-Changed-From-To: open->analyzed
State-Changed-By: cae
State-Changed-When: Thu May  8 18:52:25 2003
State-Changed-Why:
    Confirmed, still present in 3.4-cvs. This is a reduced testcase:
    
    register int STACK __asm__("%ebx");
    static void (*p) ();
    void f ()
    {
            STACK += 1;
            p ();
            STACK -= 1;
    }
    
    Looking at the assembly shows that STACK += 1 ist lost if compiled
    with -O. The problem seems to be that life analysis adds a REG_DEAD
    note to the call to (*p) which makes STACK += 1 a dead store.
    
       regards  Christian
    

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10684