[Bug rtl-optimization/67124] New: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[Bug rtl-optimization/67124] New: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

            Bug ID: 67124
           Summary: wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc trunk miscompiles the following code on x86_64-linux-gnu at
-O1, -O2 and -O3 in the 64-bit mode (but not in the 32-bit mode). 

This is a regression from 5.1.x.

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20150804 (experimental) [trunk revision 226592] (GCC) 
$ 
$ gcc-trunk -O0 small.c; ./a.out
$ gcc-5.1 -O1 small.c; ./a.out
$ 
$ gcc-trunk -O1 small.c
$ ./a.out
Aborted (core dumped)
$ 


--------------------------------------------------


struct S1
{
  int:11;
  char f1;
  short f2;
  int f3;
  int f4;
} a[2] = {{0, 0, 0, 0}, {1, 0, 1, 0}}, *b = &a[0];

int
main ()
{
  struct S1 c = a[1];
  c.f2 = 0;
  *b = c;
  for (;;)
    if (c.f1)
      break;

  if (a[0].f3 != 1) 
    __builtin_abort (); 

  return 0;
}

[Bug rtl-optimization/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-08-05
                 CC|                            |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |6.0
            Summary|wrong code at -O1, -O2 and  |[6 Regression] wrong code
                   |-O3 on x86_64-linux-gnu     |at -O1, -O2 and -O3 on
                   |                            |x86_64-linux-gnu
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.

[Bug target/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-*-*
          Component|rtl-optimization            |target

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, looks like a target issue.  We expand from

  c = a[1];
  c$2_10 = MEM[(struct S1[2] *)&a + 18B];
  b.0_4 = b;
  MEM[(struct S1 *)&c + 2B] = c$2_10;
  MEM[(struct S1 *)&c + 4B] = 0;
  *b.0_4 = c;
  if (c$2_10 != 0)
..
  _6 = a[0].f3;
  if (_6 != 1)
...

and get

        movzbl  a+18(%rip), %eax
        movdqa  a+16(%rip), %xmm0
        movq    %xmm0, %rdx
        movq    %rax, %rcx
        salq    $16, %rax
        andq    $-16711681, %rdx
        orq     %rax, %rdx
        xorl    %eax, %eax
        testb   %cl, %cl
        movq    %rdx, 8(%rsp)
        movq    8(%rsp), %xmm0
        pinsrw  $2, %eax, %xmm0
        movq    b(%rip), %rax
        movups  %xmm0, (%rax)   <---
        jne     .L2
.L3:
        jmp     .L3
        .p2align 4,,10
        .p2align 3
.L2:
        cmpl    $1, a+8(%rip)
        jne     .L7


but <--- stores the wrong value here.  -mno-sse2 fixes the testcase.

[Bug target/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r225852.

[Bug rtl-optimization/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra
                 CC|                            |vmakarov at gcc dot gnu.org
          Component|middle-end                  |rtl-optimization

--- Comment #7 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to rsandifo@gcc.gnu.org from comment #6)

> The expand code looks OK to me.  Assigning to one DImode word
> of a TImode isn't supposed to change the other half.
> 
> I think the problem is in LRA.  It tries to reload the low half
> of the TImode as follows:

Thanks for your analysis!

Reconfirmed as RA problem, adding another CC.
>From gcc-bugs-return-494329-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Aug 06 22:40:26 2015
Return-Path: <gcc-bugs-return-494329-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Delivered-To: listarch-gcc-bugs@gcc.gnu.org
Received: (qmail 99378 invoked by alias); 6 Aug 2015 22:40:26 -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
Delivered-To: mailing list gcc-bugs@gcc.gnu.org
Received: (qmail 99325 invoked by uid 48); 6 Aug 2015 22:40:22 -0000
From: "kargl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/67140] undefined reference to _gfortran_mvbits_i16
Date: Thu, 06 Aug 2015 22:40:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 4.8.4
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: kargl at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution:
X-Bugzilla-Priority: P4
X-Bugzilla-Assigned-To: kargl at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: priority bug_status cf_reconfirmed_on cc assigned_to everconfirmed cf_known_to_fail
Message-ID: <bug-67140-4-oC8fSN3icM@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-67140-4@http.gcc.gnu.org/bugzilla/>
References: <bug-67140-4@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: 2015-08/txt/msg00471.txt.bz2
Content-length: 841

https://gcc.gnu.org/bugzilla/show_bug.cgi?idg140

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-08-06
                 CC|                            |kargl at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |kargl at gcc dot gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.5, 4.9.4, 5.2.1, 6.0

--- Comment #1 from kargl at gcc dot gnu.org ---
I have a patch.  Don't know if it actaully works
as your test program has no output and no indication
of the expected result.

[Bug target/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

--- Comment #11 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #10)
> I think a fix is required for *movdi_internal.  Back to target bug.

Even in the light of Comment #6 ?
>From gcc-bugs-return-499011-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Oct 08 08:49:08 2015
Return-Path: <gcc-bugs-return-499011-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Delivered-To: listarch-gcc-bugs@gcc.gnu.org
Received: (qmail 54008 invoked by alias); 8 Oct 2015 08:49:06 -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
Delivered-To: mailing list gcc-bugs@gcc.gnu.org
Received: (qmail 51587 invoked by uid 48); 8 Oct 2015 08:49:00 -0000
From: "dominiq at lps dot ens.fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/67884] Missing error message on required allocatable attribute
Date: Thu, 08 Oct 2015 08:49:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 5.2.1
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: dominiq at lps dot ens.fr
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution:
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: bug_status cf_reconfirmed_on everconfirmed
Message-ID: <bug-67884-4-5vaFZeyiNB@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-67884-4@http.gcc.gnu.org/bugzilla/>
References: <bug-67884-4@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: 2015-10/txt/msg00566.txt.bz2
Content-length: 520

https://gcc.gnu.org/bugzilla/show_bug.cgi?idg884

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-10-08
     Ever confirmed|0                           |1

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Confirmed from 4.8 up to trunk (6.0).

[Bug rtl-optimization/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |rtl-optimization

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, indeed we fail to preserve the (subreg:DI (reg:TI xmm0)) in LRA

(insn 53 52 16 2 (set (reg:DI 21 xmm0 [orig:90 c ] [90])
        (mem/c:DI (plus:DI (reg/f:DI 7 sp)
                (const_int 8 [0x8])) [0 %sfp+-8 S8 A64])) t.c:16 85
{*movdi_internal}
     (nil))
...
(insn 17 16 49 2 (set (reg:V8HI 21 xmm0 [100])
        (vec_merge:V8HI (vec_duplicate:V8HI (reg:HI 0 ax [99]))
            (reg:V8HI 21 xmm0 [orig:90 c ] [90])
            (const_int 4 [0x4]))) t.c:16 3597 {sse2_pinsrw}
     (nil))

from

(insn 15 14 16 2 (parallel [
            (set (subreg:DI (reg/v:TI 90 [ c ]) 0)
                (ior:DI (reg:DI 97)
                    (reg:DI 95)))
            (clobber (reg:CC 17 flags))
        ]) t.c:16 398 {*iordi_1}
     (expr_list:REG_DEAD (reg:DI 97)
        (expr_list:REG_DEAD (reg:DI 95)
            (expr_list:REG_UNUSED (reg:CC 17 flags)
                (nil)))))
...
(insn 17 16 49 2 (set (reg:V8HI 100)
        (vec_merge:V8HI (vec_duplicate:V8HI (subreg:HI (reg:DI 99) 0))
            (subreg:V8HI (reg/v:TI 90 [ c ]) 0)
            (const_int 4 [0x4]))) t.c:16 3597 {sse2_pinsrw}

A plain DImode move to a DImode reg does not preserve the upper halves.  Not
sure if

(insn 53 52 16 2 (set (subreg:DI (reg:TI xmm0 0) [orig:90 c ] [90])
        (mem/c:DI (plus:DI (reg/f:DI 7 sp)
                (const_int 8 [0x8])) [0 %sfp+-8 S8 A64])) t.c:16 85
{*movdi_internal}
     (nil))

would be valid after "reload" though.

Maybe the bug is that we allocate a DImode register to a subreg of a TImode
destination at all.

[Bug rtl-optimization/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

--- Comment #13 from Uroš Bizjak <ubizjak at gmail dot com> ---
Almost identical problem is reported in PR 67609, but with:

(insn 7 6 0 (set (subreg:DF (reg/v:TI 90 [ v ]) 0)
        (reg/v:DF 88 [ b ])) pr67609.c:8 -1
     (nil))
>From gcc-bugs-return-499035-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Oct 08 14:26:51 2015
Return-Path: <gcc-bugs-return-499035-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Delivered-To: listarch-gcc-bugs@gcc.gnu.org
Received: (qmail 40207 invoked by alias); 8 Oct 2015 14:26:50 -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
Delivered-To: mailing list gcc-bugs@gcc.gnu.org
Received: (qmail 39280 invoked by uid 48); 8 Oct 2015 14:26:42 -0000
From: "clyon at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/67843] experimental/filesystem/iterators/directory_iterator.cc fails on armv5t
Date: Thu, 08 Oct 2015 14:26:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: unknown
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: clyon at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution:
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: redi at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-67843-4-bccamqjERH@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-67843-4@http.gcc.gnu.org/bugzilla/>
References: <bug-67843-4@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: 2015-10/txt/msg00590.txt.bz2
Content-length: 391

https://gcc.gnu.org/bugzilla/show_bug.cgi?idg843

--- Comment #7 from Christophe Lyon <clyon at gcc dot gnu.org> ---
You are probably correct: I recompiled my cross-toolchain to default to armv5t
and the test now passes.

(as opposed to armv7-a toolchain + -march=armv5t to compile the testcase).

I agree that a linker error would be good, though I don't fully understand your
patch :-)