From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-363230-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 19283 invoked by alias); 21 Jul 2011 07:40:16 -0000
Received: (qmail 19266 invoked by uid 22791); 21 Jul 2011 07:40:14 -0000
X-SWARE-Spam-Status: No, hits=-2.7 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,TW_BF,TW_OV,TW_SX,TW_VH
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 21 Jul 2011 07:40:01 +0000
From: "carrot at google dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/49799] New: gcc arm generates illegal sbfx instruction
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: carrot at google dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-49799-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Thu, 21 Jul 2011 07:40:00 -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
X-SW-Source: 2011-07/txt/msg01714.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49799

           Summary: gcc arm generates illegal sbfx instruction
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: carrot@google.com
              Host: linux
            Target: armeabi


Compile the following code with options -march=armv7-a -O2

extern __inline int bar(int a)
{
    int tmp;

    if (a <= 0) a ^= 0xFFFFFFFF;

    return tmp - 1;
}

void foo(short *K)
{
    short tmp;
    short *pptr, P[14];

    pptr = P;
    tmp = bar(*K);
    *pptr = (*K << tmp) >> 16;

    if (*P < tmp)
        *K++ = 0;
}

gcc 4.7 generates

foo:
    ldrsh    r3, [r0, #0]
    sbfx    r3, r3, #17, #16    // A
    sxth    r3, r3
    cmn    r3, #1
    movlt    r3, #0
    strlth    r3, [r0, #0]    @ movhi
    bx    lr

The sbfx instruction is illegal since the bit position + width > 32.

Although the source code is ill formed (function bar returns undefined value),
compiler should never generate illegal instructions.

gcc4.6 has the same problem.