[llvm-dev] unable to emit vectorized code in LLVM IR

[Nemanja Ivanovic via llvm-dev]

Move the printf out of the loop and it should vectorize just fine.

On Thu, Aug 17, 2017 at 6:52 PM, hameeza ahmed <hahmed2305 at gmail.com> wrote:

> I want to vectorize the user given inputs. when opt does vectorization
> user supplied inputs (from a text file) will be added using AVX vector
> instructions.
>
> as you pointed; When i changed my code to following:
>
> int main(int argc, char** argv) {
> int a[1000], b[1000], c[1000];
> int aa=atoi(argv[1]), bb=atoi(argv[2]);
> for (int i=0; i<1000; i++) {
> a[i]=aa, b[i]=bb;
>  c[i]=a[i] + b[i];
> printf("sum: %d\n", c[i]);
>
> }
>
> I am getting error remark: <unknown>:0:0: loop not vectorized: call
> instruction cannot be vectorized.
>
> I am running following commands:
> clang  -S -emit-llvm sum-vec.c -march=knl -O3 -mllvm -disable-llvm-optzns
> -o sum-vec.ll
> opt  -S -O3 -force-vector-width=64 sum-vec.ll -o sum-vec03.ll
>
> How to achieve this? Please help.
>
>
>
>
>
> On Thu, Aug 17, 2017 at 10:44 AM, Nemanja Ivanovic <
> nemanja.i.ibm at gmail.com> wrote:
>
>> I'm not sure what you expect to have vectorized here. If you look at the
>> emitted code, there's no loop. It's just an add and a multiply as you might
>> expect when adding a loop-invariant sum 1000 times in a loop.
>>
>> On Wed, Aug 16, 2017 at 11:38 PM, hameeza ahmed via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hello,
>>> I have written the following code. when i try to vectorize it through
>>> opt. i am not getting vectorized instructions.
>>>
>>> #include <stdio.h>
>>> #include<stdlib.h>
>>> int main(int argc, char** argv) {
>>> int sum=0; int a=atoi(argv[1]); int b=atoi(argv[2]);
>>> for (int i=0;i<1000;i++)
>>> {
>>> sum+=a+b;
>>> }
>>>
>>> printf("sum: %d\n", sum);
>>> return 0;
>>> }
>>> i use following commands:
>>> clang  -S -emit-llvm sum-main.c -march=knl -O3 -mllvm
>>> -disable-llvm-optzns -o sum-main.ll
>>> opt  -S -O3 -force-vector-width=64 sum-main.ll -o sum-main03.ll
>>>
>>> why is that so? where am i doing mistake? i am not getting vectorized
>>> operations rather getting scalar operations.
>>>
>>> Please help.
>>>
>>> Thank You
>>>
>>> Regards
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>
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