From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-361819-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 14270 invoked by alias); 5 Jul 2011 12:19:34 -0000
Received: (qmail 14259 invoked by uid 22791); 5 Jul 2011 12:19:29 -0000
X-SWARE-Spam-Status: No, hits=-2.7 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
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; Tue, 05 Jul 2011 12:19:15 +0000
From: "sebastian.huber@embedded-brains.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/49641] New: [ARM] Wrong code for ARMv4T and stmia
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: sebastian.huber@embedded-brains.de
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-49641-4@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: Tue, 05 Jul 2011 12:19:00 -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/msg00303.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49641

           Summary: [ARM] Wrong code for ARMv4T and stmia
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: sebastian.huber@embedded-brains.de
            Target: arm-rtemseabi4.11


Created attachment 24689
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24689
Sample code.

The attached source code generates the following assembler code:

00000000 <_Watchdog_Handler_initialization>:
   0:   2200            movs    r2, #0
   2:   4b06            ldr     r3, [pc, #24]   ; (1c
<_Watchdog_Handler_initialization+0x1c>)
   4:   601a            str     r2, [r3, #0]
   6:   4b06            ldr     r3, [pc, #24]   ; (20
<_Watchdog_Handler_initialization+0x20>)
   8:   601a            str     r2, [r3, #0]
   a:   4b06            ldr     r3, [pc, #24]   ; (24
<_Watchdog_Handler_initialization+0x24>)
   c:   601a            str     r2, [r3, #0]
   e:   4b06            ldr     r3, [pc, #24]   ; (28
<_Watchdog_Handler_initialization+0x28>)
  10:   1d19            adds    r1, r3, #4
  12:   c30e            stmia   r3!, {r1, r2, r3}
  14:   4b05            ldr     r3, [pc, #20]   ; (2c
<_Watchdog_Handler_initialization+0x2c>)
  16:   1d19            adds    r1, r3, #4
  18:   c30e            stmia   r3!, {r1, r2, r3}
  1a:   4770            bx      lr

In particular it generates: stmia r3!, {r1, r2, r3}

This instruction leads to UNPREDICTABLE behavior.  According to "ARM
Architecture Reference Manual, Issue I" we have in section "A7.1.57 STMIA",
"Operand restrictions":

"If <Rn> is specified in <registers>:
 o If <Rn> is the lowest-numbered register specified in <registers>, the
original value of <Rn> is stored.
 o Otherwise, the stored value of <Rn> is UNPREDICTABLE."

Since r3 is not the lowest-numbered register specified in {r1, r2, r3} the
stored value of r3 is UNPREDICTABLE.