[Bug tree-optimization/66272] New: wrong code at -O3 on x86_64-linux-gnu

[Bug tree-optimization/66272] New: wrong code at -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

            Bug ID: 66272
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-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 at -O3 in
both 32-bit and 64-bit modes.  

It also affects gcc 5.1.x and 4.9.2 (but not 4.9.0 and I didn't check 4.9.1). 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-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 20150524 (experimental) [trunk revision 223630] (GCC) 
$ 
$ gcc-trunk -O2 small.c; ./a.out
$ gcc-4.9.0 -O3 small.c; ./a.out
$ 
$ gcc-trunk -O3 small.c  
$ ./a.out
Aborted (core dumped)
$ gcc-4.9.2 -O3 small.c
$ ./a.out
Aborted (core dumped)
$ gcc-5.1.0 -O3 small.c
$ ./a.out
Aborted (core dumped)
$ 


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


struct S
{
  int f0;
  int f1;
} a[2], c;

int b;

int
main ()
{
  struct S d = { 0, 1 };

  for (b = 0; b < 2; b++)
    {
      a[b] = d;
      c = d = a[0];
    }

  if (c.f1 != 1)
    __builtin_abort ();

  return 0;
}

[Bug tree-optimization/66272] [4.9.2/5/6 Regression] wrong code at -O3 on x86_64-linux-gnu

[miyuki at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

Mikhail Maltsev <miyuki at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |4.8.4
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2015-05-24
                 CC|                            |miyuki at gcc dot gnu.org
     Ever confirmed|0                           |1
            Summary|wrong code at -O3 on        |[4.9.2/5/6 Regression]
                   |x86_64-linux-gnu            |wrong code at -O3 on
                   |                            |x86_64-linux-gnu
      Known to fail|                            |4.9.2, 5.1.0, 6.0

--- Comment #1 from Mikhail Maltsev <miyuki at gcc dot gnu.org> ---
The testcase can be simplified a bit (I eliminated variable c and moved array a
inside main, so it's now local).

struct S
{
  int f0;
  int f1;
};

int b;

int main ()
{
    struct S a[2] = { 0 };
    struct S d = { 0, 1 };
    for (b = 0; b < 2; b++) {
        a[b] = d;
        d = a[0];
    }
    if (d.f1 != 1)
        __builtin_abort ();
}

Wrong transformation is made in predictive commoning pass (the program compiled
with -O3 -fno-predictive-commoning does not abort). The store d.f1 = a[0].f1;
is assumed to be independent of the previous store to a[b] (which is obviously
wrong) and it is hoisted out of the loop.

I think the reason is that find_data_references_in_stmt or some related
function misenterprets MEM[(struct S[2] *)&a + 4B] as some object that does not
alias with MEM[(struct S *)&a]'s SCEV.
By the way, the expression itself looks strange: struct S * should be "a", not
"&a".

(Data Dep:
#(Data Ref:
#  bb: 3
#  stmt: MEM[(struct S *)_4 + 4B] = d$f1_7;
#  ref: MEM[(struct S *)_4 + 4B];
#  base_object: MEM[(struct S *)&a];
#  Access function 0: {4B, +, 8}_1
#)
#(Data Ref:
#  bb: 3
#  stmt: d$f1_16 = MEM[(struct S[2] *)&a + 4B];
#  ref: MEM[(struct S[2] *)&a + 4B];
#  base_object: MEM[(struct S[2] *)&a + 4B];
#)
    (no dependence)
)

If I scalarize the assignment d = a[0] (I mean, in the source), the bug
disappears.

[Bug tree-optimization/66272] [4.9/5/6 Regression] wrong code at -O3 on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
   Target Milestone|---                         |4.9.3
            Summary|[4.9.2/5/6 Regression]      |[4.9/5/6 Regression] wrong
                   |wrong code at -O3 on        |code at -O3 on
                   |x86_64-linux-gnu            |x86_64-linux-gnu

[Bug tree-optimization/66272] [4.9/5/6 Regression] wrong code at -O3 on x86_64-linux-gnu

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r214006.

[Bug tree-optimization/66272] [4.9/5/6 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Bah, mine.

[Bug tree-optimization/66272] [4.9/5/6 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed May 27 14:20:48 2015
New Revision: 223759

URL: https://gcc.gnu.org/viewcvs?rev=223759&root=gcc&view=rev
Log:
2015-05-27  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66272
        Revert parts of
        2014-08-15  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/62031
        * tree-data-ref.c (dr_analyze_indices): Do not set
        DR_UNCONSTRAINED_BASE.
        (dr_may_alias_p): All indirect accesses have to go the
        formerly DR_UNCONSTRAINED_BASE path.
        * tree-data-ref.h (struct indices): Remove
        unconstrained_base member.
        (DR_UNCONSTRAINED_BASE): Remove.

        * gcc.dg/torture/pr66272.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr66272.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-data-ref.c
    trunk/gcc/tree-data-ref.h

[Bug tree-optimization/66272] [4.9/5 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |6.0
            Summary|[4.9/5/6 Regression] wrong  |[4.9/5 Regression] wrong
                   |code at -O3 on              |code at -O3 on
                   |x86_64-linux-gnu            |x86_64-linux-gnu
      Known to fail|6.0                         |

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk sofar.

[Bug tree-optimization/66272] [4.8/4.9/5 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed Jun  3 07:39:06 2015
New Revision: 224059

URL: https://gcc.gnu.org/viewcvs?rev=224059&root=gcc&view=rev
Log:
2015-06-03  Richard Biener  <rguenther@suse.de>

        Backport from mainline
        2015-06-02  Richard Biener  <rguenther@suse.de>

        PR debug/65549
        * dwarf2out.c (lookup_context_die): New function.
        (resolve_addr): Avoid forcing a full DIE for the
        target of a DW_TAG_GNU_call_site during late compilation.
        Instead create a stub DIE without a type if we have a
        context DIE present.

        * g++.dg/lto/pr65549_0.C: New testcase.

        2015-06-01  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66280
        * tree-vect-slp.c (vect_detect_hybrid_slp_stmts): Fix pattern
        def-use walking.

        * g++.dg/torture/pr66280.C: New testcase.
        * g++.dg/torture/pr66280-2.C: Likewise.

        2015-05-27  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66272
        Revert parts of
        2014-08-15  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/62031
        * tree-data-ref.c (dr_analyze_indices): Do not set
        DR_UNCONSTRAINED_BASE.
        (dr_may_alias_p): All indirect accesses have to go the
        formerly DR_UNCONSTRAINED_BASE path.
        * tree-data-ref.h (struct indices): Remove
        unconstrained_base member.
        (DR_UNCONSTRAINED_BASE): Remove.

        * gcc.dg/torture/pr66272.c: New testcase.

        2015-05-21  Richard Biener  <rguenther@suse.de>

        PR c++/66211
        * match.pd: Guard pattern optimzing (int)(float)int
        conversions to apply only on GIMPLE.

        * g++.dg/conversion/pr66211.C: New testcase.
        * gcc.dg/tree-ssa/forwprop-18.c: Adjust.

        2015-05-13  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66123
        * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found
        a taken edge.

        * gcc.dg/torture/pr66123.c: New testcase.

Added:
    branches/gcc-5-branch/gcc/testsuite/g++.dg/conversion/pr66211.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/lto/pr65549_0.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/torture/pr66280-2.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/torture/pr66280.C
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/torture/pr66123.c
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/torture/pr66272.c
Modified:
    branches/gcc-5-branch/gcc/ChangeLog
    branches/gcc-5-branch/gcc/dwarf2out.c
    branches/gcc-5-branch/gcc/match.pd
    branches/gcc-5-branch/gcc/testsuite/ChangeLog
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/tree-ssa/forwprop-18.c
    branches/gcc-5-branch/gcc/tree-data-ref.c
    branches/gcc-5-branch/gcc/tree-data-ref.h
    branches/gcc-5-branch/gcc/tree-ssa-dom.c
    branches/gcc-5-branch/gcc/tree-vect-slp.c

[Bug tree-optimization/66272] [4.8/4.9 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed Jun  3 11:03:26 2015
New Revision: 224072

URL: https://gcc.gnu.org/viewcvs?rev=224072&root=gcc&view=rev
Log:
2015-06-03  Richard Biener  <rguenther@suse.de>

        Backport from mainline
        2015-05-26  Michael Matz  <matz@suse.de>

        PR middle-end/66251
        * tree-vect-stmts.c (vect_create_vectorized_demotion_stmts): Always set
        STMT_VINFO_VEC_STMT, also with SLP.

        * gcc.dg/vect/pr66251.c: New test.

        2015-05-22  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66251
        * tree-vect-stmts.c (vectorizable_conversion): Properly
        set STMT_VINFO_VEC_STMT even for the SLP case.

        * gfortran.fortran-torture/compile/pr66251.f90: New testcase.

        2015-05-27  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66272
        Revert parts of
        2014-08-15  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/62031
        * tree-data-ref.c (dr_analyze_indices): Do not set
        DR_UNCONSTRAINED_BASE.
        (dr_may_alias_p): All indirect accesses have to go the
        formerly DR_UNCONSTRAINED_BASE path.
        * tree-data-ref.h (struct indices): Remove
        unconstrained_base member.
        (DR_UNCONSTRAINED_BASE): Remove.

        * gcc.dg/torture/pr66272.c: New testcase.

        2015-05-13  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66123
        * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found
        a taken edge.

        * gcc.dg/torture/pr66123.c: New testcase.

        2015-06-02  Richard Biener  <rguenther@suse.de>

        PR debug/65549
        * dwarf2out.c (lookup_context_die): New function.
        (resolve_addr): Avoid forcing a full DIE for the
        target of a DW_TAG_GNU_call_site during late compilation.
        Instead create a stub DIE without a type if we have a
        context DIE present.

        * g++.dg/lto/pr65549_0.C: New testcase.

        2015-03-23  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/65518
        * tree-vect-stmts.c (vectorizable_load): Reject single-element
        interleaving cases we generate absymal code for.

        * gcc.dg/vect/pr65518.c: New testcase.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/g++.dg/lto/pr65549_0.C
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/torture/pr66123.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/torture/pr66272.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/pr65518.c
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/pr66251.c
   
branches/gcc-4_9-branch/gcc/testsuite/gfortran.fortran-torture/compile/pr66251.f90
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/dwarf2out.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_9-branch/gcc/tree-data-ref.c
    branches/gcc-4_9-branch/gcc/tree-data-ref.h
    branches/gcc-4_9-branch/gcc/tree-ssa-dom.c
    branches/gcc-4_9-branch/gcc/tree-vect-stmts.c

[Bug tree-optimization/66272] [4.8 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed Jun  3 13:50:11 2015
New Revision: 224081

URL: https://gcc.gnu.org/viewcvs?rev=224081&root=gcc&view=rev
Log:
2015-06-03  Richard Biener  <rguenther@suse.de>

        Backport from mainline
        2015-05-26  Michael Matz  <matz@suse.de>

        PR middle-end/66251
        * tree-vect-stmts.c (vect_create_vectorized_demotion_stmts): Always set
        STMT_VINFO_VEC_STMT, also with SLP.

        * gcc.dg/vect/pr66251.c: New test.

        2015-05-22  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66251
        * tree-vect-stmts.c (vectorizable_conversion): Properly
        set STMT_VINFO_VEC_STMT even for the SLP case.

        * gfortran.fortran-torture/compile/pr66251.f90: New testcase.

        2015-03-23  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/65518
        * tree-vect-stmts.c (vectorizable_load): Reject single-element
        interleaving cases we generate absymal code for.

        * gcc.dg/vect/pr65518.c: New testcase.

        2015-05-13  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66123
        * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found
        a taken edge.

        * gcc.dg/torture/pr66123.c: New testcase.

        2015-05-27  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66272
        Revert parts of
        2014-08-15  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/62031
        * tree-data-ref.c (dr_analyze_indices): Do not set
        DR_UNCONSTRAINED_BASE.
        (dr_may_alias_p): All indirect accesses have to go the
        formerly DR_UNCONSTRAINED_BASE path.
        * tree-data-ref.h (struct indices): Remove
        unconstrained_base member.
        (DR_UNCONSTRAINED_BASE): Remove.

        * gcc.dg/torture/pr66272.c: New testcase.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr66123.c
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr66272.c
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/vect/pr65518.c
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/vect/pr66251.c
   
branches/gcc-4_8-branch/gcc/testsuite/gfortran.fortran-torture/compile/pr66251.f90
Modified:
    branches/gcc-4_8-branch/gcc/ChangeLog
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_8-branch/gcc/tree-data-ref.c
    branches/gcc-4_8-branch/gcc/tree-data-ref.h
    branches/gcc-4_8-branch/gcc/tree-ssa-dom.c
    branches/gcc-4_8-branch/gcc/tree-vect-stmts.c

[Bug tree-optimization/66272] [4.8 Regression] wrong code at -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66272

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to work|4.8.4                       |
         Resolution|---                         |FIXED

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.