llvm dev - Nov 2017 - unable to vectorize copy statement

Hello,
I am trying to vectorize copy statement in LLVM but unable to do so why? my
code is follows:

int main()

{

int c[2048], a[2048];

for (int j=0; j<2048; j++)

  { a[j]=2;
  c[j] = a[j];

}
}

the command is follows:
opt  -S -O3 -force-vector-width=64 s.ll -o s_o3.ll

how to do this?
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Nothing uses the array after the loop and the program exits after that.
Thus the compiler optimized out the loop because the computation was
unnecessary. It had not affect on the observable behavior of the program.

~Craig

On Fri, Nov 10, 2017 at 1:24 PM, hameeza ahmed <hahmed2305 at gmail.com>
wrote:
> Hello,
> I am trying to vectorize copy statement in LLVM but unable to do so why?
> my code is follows:
>
> int main()
>
> {
>
> int c[2048], a[2048];
>
> for (int j=0; j<2048; j++)
>
>   { a[j]=2;
>   c[j] = a[j];
>
> }
> }
>
> the command is follows:
> opt  -S -O3 -force-vector-width=64 s.ll -o s_o3.ll
>
> how to do this?
>
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> On Nov 10, 2017, at 15:24, hameeza ahmed via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hello,
> I am trying to vectorize copy statement in LLVM but unable to do so why? my
code is follows:
> 
> int main()
> 
> {
> 
> int c[2048], a[2048];
> 
> for (int j=0; j<2048; j++)
> 
> 	  { a[j]=2;
>   c[j] = a[j];
> 
> }
> }
> 
> the command is follows:
> opt  -S -O3 -force-vector-width=64 s.ll -o s_o3.ll
> 
> how to do this?
This seems to work, although I'm not entirely sure about the
-force-vector-width=64.

https://godbolt.org/g/oqzaHR


-- 
Stephen Checkoway