[llvm-dev] LLVM opt unable to vectorize PolyBench code

[hameeza ahmed via llvm-dev]

C- Code;

/**
 * 2mm.c: This file is part of the PolyBench/C 3.2 test suite.
 *
 *
 * Contact: Louis-Noel Pouchet <pouchet at cse.ohio-state.edu>
 * Web address: http://polybench.sourceforge.net
 */
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <math.h>

/* Include polybench common header. */
#include <polybench.h>

/* Include benchmark-specific header. */
/* Default data type is double, default size is 4000. */
#include "2mm.h"


/* Array initialization. */
static
void init_array(int ni, int nj, int nk, int nl,
        DATA_TYPE *alpha,
        DATA_TYPE *beta,
        DATA_TYPE POLYBENCH_2D(A,NI,NK,ni,nl),
        DATA_TYPE POLYBENCH_2D(B,NK,NJ,nk,nj),
        DATA_TYPE POLYBENCH_2D(C,NL,NJ,nl,nj),
        DATA_TYPE POLYBENCH_2D(D,NI,NL,ni,nl))
{
  int i, j;

  *alpha = 32412;
  *beta = 2123;
  for (i = 0; i < ni; i++)
    for (j = 0; j < nk; j++)
      A[i][j] = ((DATA_TYPE) i*j) / ni;
  for (i = 0; i < nk; i++)
    for (j = 0; j < nj; j++)
      B[i][j] = ((DATA_TYPE) i*(j+1)) / nj;
  for (i = 0; i < nl; i++)
    for (j = 0; j < nj; j++)
      C[i][j] = ((DATA_TYPE) i*(j+3)) / nl;
  for (i = 0; i < ni; i++)
    for (j = 0; j < nl; j++)
      D[i][j] = ((DATA_TYPE) i*(j+2)) / nk;
}


/* DCE code. Must scan the entire live-out data.
   Can be used also to check the correctness of the output. */
static
void print_array(int ni, int nl,
         DATA_TYPE POLYBENCH_2D(D,NI,NL,ni,nl))
{
  int i, j;

  for (i = 0; i < ni; i++)
    for (j = 0; j < nl; j++) {
    fprintf (stderr, DATA_PRINTF_MODIFIER, D[i][j]);
    if ((i * ni + j) % 20 == 0) fprintf (stderr, "\n");
    }
  fprintf (stderr, "\n");
}


/* Main computational kernel. The whole function will be timed,
   including the call and return. */
static
void kernel_2mm(int ni, int nj, int nk, int nl,
        DATA_TYPE alpha,
        DATA_TYPE beta,
        DATA_TYPE POLYBENCH_2D(tmp,NI,NJ,ni,nj),
        DATA_TYPE POLYBENCH_2D(A,NI,NK,ni,nk),
        DATA_TYPE POLYBENCH_2D(B,NK,NJ,nk,nj),
        DATA_TYPE POLYBENCH_2D(C,NL,NJ,nl,nj),
        DATA_TYPE POLYBENCH_2D(D,NI,NL,ni,nl))
{
  int i, j, k;

#pragma scop
  /* D := alpha*A*B*C + beta*D */
  for (i = 0; i < _PB_NI; i++)
    for (j = 0; j < _PB_NJ; j++)
      {
    tmp[i][j] = 0;
    for (k = 0; k < _PB_NK; ++k)
      tmp[i][j] += alpha * A[i][k] * B[k][j];
      }
  for (i = 0; i < _PB_NI; i++)
    for (j = 0; j < _PB_NL; j++)
      {
    D[i][j] *= beta;
    for (k = 0; k < _PB_NJ; ++k)
      D[i][j] += tmp[i][k] * C[k][j];
      }
#pragma endscop

}


int main(int argc, char** argv)
{
  /* Retrieve problem size. */
  int ni = NI;
  int nj = NJ;
  int nk = NK;
  int nl = NL;

  /* Variable declaration/allocation. */
  DATA_TYPE alpha;
  DATA_TYPE beta;
  POLYBENCH_2D_ARRAY_DECL(tmp,DATA_TYPE,NI,NJ,ni,nj);
  POLYBENCH_2D_ARRAY_DECL(A,DATA_TYPE,NI,NK,ni,nk);
  POLYBENCH_2D_ARRAY_DECL(B,DATA_TYPE,NK,NJ,nk,nj);
  POLYBENCH_2D_ARRAY_DECL(C,DATA_TYPE,NL,NJ,nl,nj);
  POLYBENCH_2D_ARRAY_DECL(D,DATA_TYPE,NI,NL,ni,nl);

  /* Initialize array(s). */
  init_array (ni, nj, nk, nl, &alpha, &beta,
          POLYBENCH_ARRAY(A),
          POLYBENCH_ARRAY(B),
          POLYBENCH_ARRAY(C),
          POLYBENCH_ARRAY(D));

  /* Start timer. */
  polybench_start_instruments;

  /* Run kernel. */
  kernel_2mm (ni, nj, nk, nl,
          alpha, beta,
          POLYBENCH_ARRAY(tmp),
          POLYBENCH_ARRAY(A),
          POLYBENCH_ARRAY(B),
          POLYBENCH_ARRAY(C),
          POLYBENCH_ARRAY(D));

  /* Stop and print timer. */
  polybench_stop_instruments;
  polybench_print_instruments;

  /* Prevent dead-code elimination. All live-out data must be printed
     by the function call in argument. */
  polybench_prevent_dce(print_array(ni, nl,  POLYBENCH_ARRAY(D)));

  /* Be clean. */
  POLYBENCH_FREE_ARRAY(tmp);
  POLYBENCH_FREE_ARRAY(A);
  POLYBENCH_FREE_ARRAY(B);
  POLYBENCH_FREE_ARRAY(C);
  POLYBENCH_FREE_ARRAY(D);

  return 0;
}

 clang  -S -emit-llvm -I utilities -I linear-algebra/kernels/2mm
utilities/polybench.c linear-algebra/kernels/2mm/2mm.c -march=knl -O3
-mllvm -disable-llvm-optzns


On Thu, Mar 15, 2018 at 3:31 AM, Craig Topper <craig.topper at gmail.com>
wrote:

> It would help if you sent the IR you're giving to opt or at least a
> complete C function and your clang command line.
>
> ~Craig
>
> On Wed, Mar 14, 2018 at 3:05 PM, hameeza ahmed <hahmed2305 at gmail.com>
> wrote:
>
>> Hello,
>>
>> I m unable to vectorize following kernel by opt tool;
>>
>> for (i = 0; i < _PB_NI; i++)
>>     for (j = 0; j < _PB_NJ; j++)
>>       {
>>     tmp[i][j] = 0;
>>     for (k = 0; k < _PB_NK; ++k)
>>       tmp[i][j] += alpha * A[i][k] * B[k][j];
>>       }
>>   for (i = 0; i < _PB_NI; i++)
>>     for (j = 0; j < _PB_NL; j++)
>>       {
>>     D[i][j] *= beta;
>>     for (k = 0; k < _PB_NJ; ++k)
>>       D[i][j] += tmp[i][k] * C[k][j];
>>       }
>>
>> i m using following command
>> $opt  -S -O3 -force-vector-width=64 -pass-remarks=loop-vectorize
>> -enable-load-pre=0 2mm.ll -o 2mm-64_o3.ll
>>
>> what is wrong here? what should i do?
>>
>> Please help..
>>
>>
>
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