[Bug middle-end/60960] New: Wrong result when a vector variable is divided by a literal constant

[Bug middle-end/60960] New: Wrong result when a vector variable is divided by a literal constant

[uranus at tinlans dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

            Bug ID: 60960
           Summary: Wrong result when a vector variable is divided by a
                    literal constant
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: uranus at tinlans dot org

> gcc -v
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.8.2/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.8.2/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.8.2/work/gcc-4.8.2/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.8.2
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.2
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.2/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.2/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.2/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-cloog --disable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --enable-multilib
--with-multilib-list=m32,m64 --enable-libmudflap --disable-libssp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.8.2/python
--enable-checking=release --enable-java-awt=gtk --enable-libstdcxx-time
--enable-objc-gc --enable-languages=c,c++,java,objc,obj-c++,fortran
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --enable-targets=all --with-bugurl=http://bugs.gentoo.org/
--with-pkgversion='Gentoo 4.8.2 p1.0, pie-0.5.8'
Thread model: posix
gcc version 4.8.2 (Gentoo 4.8.2 p1.0, pie-0.5.8)

---------------
Example code (2 files to avoid the interference from the automatic inline
feature):

/* vec.c */
typedef unsigned char v4qi __attribute__ ((vector_size (4)));

v4qi f1 (v4qi v);
v4qi f2 (v4qi v);
v4qi f3 (v4qi x, v4qi y);
void print (v4qi v);

int
main ()
{
  v4qi x = { 5, 5, 5, 5 };
  v4qi y = { 2, 2, 2, 2 };
  v4qi z;

  z = f1 (x);
  print (z);

  z = f2 (x);
  print (z);

  z = f3 (x, y);
  print (z);

  return 0;
}

/* vec-impl.c */
#include <stdio.h>

typedef unsigned char v4qi __attribute__ ((vector_size (4)));

v4qi
f1 (v4qi v)
{
  return v / 2;
}

v4qi
f2 (v4qi v)
{
  return v / (v4qi) { 2, 2, 2, 2 };
}

v4qi
f3 (v4qi x, v4qi y)
{
  return x / y;
}

void
print (v4qi v)
{
  printf ("%d %d %d %d\n", v[3], v[2], v[1], v[0]);
}

---------------
Command line:
> gcc -O3 -c vec.c
> gcc -O3 -c vec-impl.c
> gcc -O3 vec.o vec-impl.o -o test
> ./test

Output:
2 130 130 130
2 130 130 130
2 2 2 2
---------------

Although the target doesn't support this operation, I remember GCC is able to
expand it to proper scalar operations.
I expected all of the 3 outputs should be identical, but the results returned
by f1 () and f2 () are wrong.
The whole vector is treated as an integer variable and right shifted by 1 in f1
() and f2 ().
By using the command "gcc -O3 -fdump-tree-all -da -S vec-impl.c", we can see
the assembly code of f1 () and f2 () is wrong:
f1:
.LFB24:
        .cfi_startproc  
        movl    %edi, %eax
        shrl    %eax
        ret
        .cfi_endproc
.LFE24:
        .size   f1, .-f1  
        .p2align 4,,15   
        .globl  f2
        .type   f2, @function
I don't show the assembly code of f2 () because is the same.

Here is the RTL expansion result of the function f1 () in the file
vec-impl.c.166r.expand:
(note 4 1 2 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(insn 2 4 3 2 (set (reg/v:SI 61 [ v ])
        (reg:SI 5 di [ v ])) vec-impl.c:7 -1
     (nil))
(note 3 2 6 2 NOTE_INSN_FUNCTION_BEG)
(insn 6 3 7 2 (parallel [
            (set (reg:SI 62 [ D.2425 ])
                (lshiftrt:SI (reg/v:SI 61 [ v ])
                    (const_int 1 [0x1])))
            (clobber (reg:CC 17 flags))
        ]) vec-impl.c:8 -1
     (nil))
(insn 7 6 11 2 (set (reg:SI 60 [ <retval> ])
        (reg:SI 62 [ D.2425 ])) vec-impl.c:8 -1
     (nil))
(insn 11 7 14 2 (set (reg/i:SI 0 ax)
        (reg:SI 60 [ <retval> ])) vec-impl.c:9 -1
     (nil))
(insn 14 11 0 2 (use (reg/i:SI 0 ax)) vec-impl.c:9 -1
     (nil))

And here is its corresponding GIMPLE:
f1 (v4qi v)
{
  vector(4) unsigned char _4;

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  _4 = v_1(D) >> 1;
  return _4;
;;    succ:       EXIT

}

I'm not sure whether it's correct or not; anyway, I can make sure the
transformation was done by the veclower pass.
We could see it was a vector operation in the file vec-impl.c.121t.loopdone:
;; Function f1 (f1, funcdef_no=24, decl_uid=2380, cgraph_uid=24)

f1 (v4qi v)
{
  v4qi _2;

  <bb 2>:
  _2 = v_1(D) / { 2, 2, 2, 2 };
  return _2;

}
And it was altered in the file vec-impl.c.122t.veclower21:
;; Function f1 (f1, funcdef_no=24, decl_uid=2380, cgraph_uid=24)

f1 (v4qi v)
{
  v4qi _2;
  vector(4) unsigned char _4;

  <bb 2>:
  _4 = v_1(D) >> 1;
  _2 = _4;
  return _2;

}

On the contrary, the transformed GIMPLE of f3 () is the one I expected:
;; Function f3 (f3, funcdef_no=26, decl_uid=2388, cgraph_uid=26)

f3 (v4qi x, v4qi y)
{
  v4qi _3;
  unsigned char _5;
  unsigned char _6;
  unsigned char _7;
  unsigned char _8;
  unsigned char _9;
  unsigned char _10;
  unsigned char _11;
  unsigned char _12;
  unsigned char _13;
  unsigned char _14;
  unsigned char _15;
  unsigned char _16;

  <bb 2>:
  _5 = BIT_FIELD_REF <x_1(D), 8, 0>;
  _6 = BIT_FIELD_REF <y_2(D), 8, 0>;
  _7 = _5 / _6;
  _8 = BIT_FIELD_REF <x_1(D), 8, 8>;
  _9 = BIT_FIELD_REF <y_2(D), 8, 8>;
  _10 = _8 / _9;
  _11 = BIT_FIELD_REF <x_1(D), 8, 16>;
  _12 = BIT_FIELD_REF <y_2(D), 8, 16>;
  _13 = _11 / _12;
  _14 = BIT_FIELD_REF <x_1(D), 8, 24>;
  _15 = BIT_FIELD_REF <y_2(D), 8, 24>;
  _16 = _14 / _15;
  _3 = {_7, _10, _13, _16};
  return _3;

}

[Bug middle-end/60960] Wrong result when a vector variable is divided by a literal constant

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-04-25
     Ever confirmed|0                           |1

[Bug middle-end/60960] [4.8/4.9/4.10 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
   Target Milestone|---                         |4.8.3
            Summary|Wrong result when a vector  |[4.8/4.9/4.10 Regression]
                   |variable is divided by a    |Wrong result when a vector
                   |literal constant            |variable is divided by a
                   |                            |literal constant

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
typedef unsigned char v4qi __attribute__ ((vector_size (4)));

__attribute__((noinline, noclone)) v4qi
f1 (v4qi v)
{
  return v / 2;
}

__attribute__((noinline, noclone)) v4qi
f2 (v4qi v)
{
  return v / (v4qi) { 2, 2, 2, 2 };
}

__attribute__((noinline, noclone)) v4qi
f3 (v4qi x, v4qi y)
{
  return x / y;
}

int
main ()
{
  v4qi x = { 5, 5, 5, 5 };
  v4qi y = { 2, 2, 2, 2 };
  v4qi z = f1 (x);
  if (__builtin_memcmp (&y, &z, sizeof (y)) != 0)
    __builtin_abort ();
  z = f2 (x);
  if (__builtin_memcmp (&y, &z, sizeof (y)) != 0)
    __builtin_abort ();
  z = f3 (x, y);
  if (__builtin_memcmp (&y, &z, sizeof (y)) != 0)
    __builtin_abort ();
  return 0;
}

Started with my r189043.  Will have a look.

[Bug tree-optimization/60960] [4.8/4.9/4.10 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

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

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 32680
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32680&action=edit
gcc49-pr60960.patch

Untested fix.

[Bug tree-optimization/60960] [4.8/4.9/4.10 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Fri Apr 25 13:52:52 2014
New Revision: 209802

URL: http://gcc.gnu.org/viewcvs?rev=209802&root=gcc&view=rev
Log:
    PR tree-optimization/60960
    * tree-vect-generic.c (expand_vector_operation): Only call
    expand_vector_divmod if type's mode satisfies VECTOR_MODE_P.

    * gcc.c-torture/execute/pr60960.c: New test.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/pr60960.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-generic.c

[Bug tree-optimization/60960] [4.8/4.9/4.10 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Fri Apr 25 13:53:45 2014
New Revision: 209803

URL: http://gcc.gnu.org/viewcvs?rev=209803&root=gcc&view=rev
Log:
    PR tree-optimization/60960
    * tree-vect-generic.c (expand_vector_operation): Only call
    expand_vector_divmod if type's mode satisfies VECTOR_MODE_P.

    * gcc.c-torture/execute/pr60960.c: New test.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr60960.c
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_9-branch/gcc/tree-vect-generic.c

[Bug tree-optimization/60960] [4.8 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.8/4.9/4.10 Regression]   |[4.8 Regression] Wrong
                   |Wrong result when a vector  |result when a vector
                   |variable is divided by a    |variable is divided by a
                   |literal constant            |literal constant

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 4.9.1+ so far.

[Bug tree-optimization/60960] [4.8 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon May  5 08:16:43 2014
New Revision: 210064

URL: http://gcc.gnu.org/viewcvs?rev=210064&root=gcc&view=rev
Log:
    Backported from mainline
    2014-04-25  Jakub Jelinek  <jakub@redhat.com>

    PR tree-optimization/60960
    * tree-vect-generic.c (expand_vector_operation): Only call
    expand_vector_divmod if type's mode satisfies VECTOR_MODE_P.

    * gcc.c-torture/execute/pr60960.c: New test.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/gcc.c-torture/execute/pr60960.c
Modified:
    branches/gcc-4_8-branch/gcc/ChangeLog
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_8-branch/gcc/tree-vect-generic.c

[Bug tree-optimization/60960] [4.8 Regression] Wrong result when a vector variable is divided by a literal constant

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60960

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.