hameeza ahmed via llvm-dev
2017-Jul-01 11:08 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
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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hameeza ahmed via llvm-dev
2017-Jul-01 12:30 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
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 > > > > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170701/3d645cb2/attachment.html>
hameeza ahmed via llvm-dev
2017-Jul-01 20:54 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
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 -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 >> >> >> >> >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170702/6381642e/attachment-0001.html>