search for: stencil_poli

Does it happen due to loop carried dependence? if yes what is the solution to vectorize such codes? please reply. i m waiting. On Jul 1, 2017 12:30 PM, "hameeza ahmed" <hahmed2305 at gmail.com> wrote: > 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

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] +

I am able to vectorize it with the following code; #include <stdio.h> #define N 100351 // This function computes 2D-5 point Jacobi stencil void stencil(int a[][N], int b[][N]) { int i, j, k; for (k = 0; k < N; k++) { for (i = 1; i <= N-2; i++) for (j = 1; j <= N-2; j++) b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] + a[i][j+1]); for

<div> </div><div> </div><div>Hello,</div><div> </div><div>To me this is an issue in llvm loop vectorizer (if N is large enough to prevent complete unrolling of j-loop).</div><div> </div><div>Woud you mind to share stencil.ll than I would say more definitely what the issue

Your problem is due to GVN partial reduction elimination (PRE) which introduces a PHI node the current loop vectorizer cannot handle: opt -O3 stencil.ll -pass-remarks=loop-vectorize -pass-remarks-missed=loop-vectorize -pass-remarks-analysis=loop-vectorize remark: <unknown>:0:0: loop not vectorized: value that could not be identified as reduction is used outside the loop remark: