From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-370814-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 5011 invoked by alias); 16 Oct 2011 22:34:56 -0000
Received: (qmail 4937 invoked by uid 22791); 16 Oct 2011 22:34:55 -0000
X-SWARE-Spam-Status: No, hits=-2.9 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; Sun, 16 Oct 2011 22:34:39 +0000
From: "oleg.endo@t-online.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/50750] New: SH Target: Pre-decrement addressing used only for first memory access
Date: Sun, 16 Oct 2011 22:34:00 -0000
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: enhancement
X-Bugzilla-Who: oleg.endo@t-online.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-50750-4@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
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: 2011-10/txt/msg01558.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50750

             Bug #: 50750
           Summary: SH Target: Pre-decrement addressing used only for
                    first memory access
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: oleg.endo@t-online.de
                CC: kkojima@gcc.gnu.org
            Target: sh*-*-*


Pre-decrement addressing is generated only for the first
memory access. Any subsequent memory access does not use 
pre-decrement addressing.
The following is a reduced example.
The problem exists with any number of memory accesses > 1
and at any optimization level.


int test_func_2_1 (int* p, int c)
{
  int r = 0;
  do
  {
    r += *--p;
    r += *--p;
    r += *--p;
  } while (--c);
  return r;
}

compiled with -fno-tree-loop-optimize -Os -m4-single -ml:

    mov    #0,r0
.L11:
    mov    r4,r1
    add    #-64,r1
    mov.l    @(60,r1),r2
    dt    r5
    add    #-12,r4
    add    r2,r0
    mov.l    @(56,r1),r2
    mov.l    @(52,r1),r1
    add    r2,r0
    bf/s    .L11
    add    r1,r0
    rts    
    nop


would be better as:

    mov    #0,r0
.L11:
    mov.l    @-r4,r1
    dt    r5
    mov.l    @-r4,r2
    add    r1,r0
    mov.l    @-r4,r3
    add    r2,r0
    bf/s    .L11
    add    r3,r0
    rts    
    nop



Using built-in specs.
COLLECT_GCC=sh-elf-gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/sh-elf/4.7.0/lto-wrapper
Target: sh-elf
Configured with: ../gcc-trunk/configure --target=sh-elf --prefix=/usr/local
--enable-languages=c,c++ --enable-multilib --disable-libssp --disable-nls
--disable-werror --enable-lto --with-newlib --with-gnu-as --with-gnu-ld
--with-system-zlib
Thread model: single
gcc version 4.7.0 20111016 (experimental) (GCC)