[Bug tree-optimization/36281] New: vectorized code not parallelized

[Bug tree-optimization/36281] New: vectorized code not parallelized

[spop at gcc dot gnu dot org]

The testcase of PR36181 should be parallelized after being vectorized.

/* { dg-do compile } */
/* { dg-options "-O3 -ftree-parallelize-loops=2" } */

int foo ()
{
  int i, sum = 0, data[1024];

  for(i = 0; i<1024; i++)
    sum += data[i];

  return sum;
}

The fix for PR36181 was to disable the parallelization of a loop when
one of the phi nodes had a vector type.  This testcase should also be
parallelized.  See also the comments from the fix for PR36181:
http://gcc.gnu.org/ml/gcc-patches/2008-05/msg01217.html


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           Summary: vectorized code not parallelized
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: spop at gcc dot gnu dot org
        ReportedBy: spop at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36281

[Bug tree-optimization/36281] vectorized code not parallelized

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-05-20 19:42 -------
Even worse:
#define vector __attribute__((vector_size(16) ))
vector int foo ()
{
  vector int i, sum = 0, data[1024];

  for(i = 0; i<1024; i++)
    sum += data[i];

  return sum;
}

With -O2 -ftree-parallelize-loops=2, this does not get parallelized at all even
though we did not run the vectorizer.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36281

[Bug tree-optimization/36281] vector code is not parallelized

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-12-28 03:23 -------
Confirmed.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2008-12-28 03:23:49
               date|                            |
            Summary|vectorized code not         |vector code is not
                   |parallelized                |parallelized


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36281

[Bug tree-optimization/36281] vector code is not parallelized

[rob1weld at aol dot com]

------- Comment #3 from rob1weld at aol dot com  2010-07-19 08:25 -------
> ... this does not get parallelized at all ...
Also see 34501

Perhaps we could make some use of Pluto. It is a fully automatic (C to OpenMP
C) parallelizer that makes code amenable to auto-vectorization.

http://pluto-compiler.sourceforge.net/


Also see these Parallelizers:
http://cri.ensmp.fr/pips/ or http://pips4u.org/
There was something I found a few days ago from here that I can no longer
locate
http://en.wikipedia.org/wiki/Automatic_parallelization

It would be great to take that inner loop (if it were much larger) and
'Kernelize' it for co-processing on our Graphics Card. We could expand GCCs
'x-parallelize-x' and threading options to automatically find the sweeter spots
to offload for co=processing (on a GPU, using OpenCL).

Barra - NVIDIA G80 GPU Functional Simulator
http://gpgpu.univ-perp.fr/index.php/Barra

If we were 'allowed' to call a post-processor (like LTO used to do) we could
call ATI's GPU SDK which supports OpenCL and outputs code BOTH to x86 and it's
own GPUs. 


Commercial Projects:
Auto-parallelizer and SIMDinator by Dalsoft
http://www.dalsoft.com/documentation_simdinator.html

NVidia's PTX
http://en.wikipedia.org/wiki/Parallel_Thread_Execution

Cray's work with LLVM
http://llvm.org/devmtg/2009-10/Greene_180k_Cores.pdf

Larrabee
http://www.drdobbs.com/architecture-and-design/216402188?pgno=5


Rob


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36281