[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing

[hameeza ahmed via llvm-dev]

Hello,

I am trying to vectorize following stencil code;

#include <stdio.h>
#define N 100351

// This function computes 2D-5 point Jacobi stencil
void stencil(int a[restrict][N])
{
   int i, j, k;
   for (k = 0; k < 100; k++)
     {  for (i = 1; i <= N-2; i++)
         {  for (j = 1; j <= N-2; j++)
        { a[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] +
a[i][j+1]);
              }
}
}}

I have used the following commands

clang  -S -emit-llvm stencil.c -march=knl -O3 -mllvm -disable-llvm-optzns
-o stencil.ll

opt  -S -O3 stencil.ll -o stencil_o3.ll

llc -x86-asm-syntax=intel stencil_o3.ll -o stencil.s

But the code is not vectorized. It still uses the scalar instructions;

Please correct me.

Thank You
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