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

[hameeza ahmed via llvm-dev]

I even tried polly but still my llvm IR does not contain vector
instructions. i used the following command;

clang  -S -emit-llvm stencil.c -march=knl -O3 -mllvm -polly -mllvm
-polly-vectorizer=stripmine -o stencil_poly.ll

Please specify what is wrong with my code?


On Sat, Jul 1, 2017 at 4:08 PM, hameeza ahmed <hahmed2305 at gmail.com> wrote:

> 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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