llvm dev - Feb 2021 - [LAI] Question about getDependences

Hi,

I am using LAI->getDependences(), It returns a vector of Dependence objects
in a Loop.
If the loop is un-analyzable or parallel, an empty list is returned.

*for example:*

*Loop A:*
for (int i = 0; i < N; i ++) {
        a[i] = c[i] + d[i];
        b[i] = c[i] * d[i];
}
*Loop B:*
for (int i = 0; i < N; i++) {
     a[b[i]] = c[i] + d[i];
     c[i] = c[i  - 1] + 1;
}

Loop A is parallel and Loop B has non-simple dependences(LAI bails out) for
both the cases we get an empty set of dependences.

Is there an API that can tell if LAI was successful in dependence
computation?


-- 
Regards,
DTharun

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Hi,
> On 18 Feb 2021, at 18:17, Dangeti Tharun kumar via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> I am using LAI->getDependences(), It returns a vector of Dependence
objects in a Loop.
> If the loop is un-analyzable or parallel, an empty list is returned.
> 
> for example:
> 
> Loop A:
> for (int i = 0; i < N; i ++) {
>         a[i] = c[i] + d[i];
>         b[i] = c[i] * d[i];
> }
> Loop B:
> for (int i = 0; i < N; i++) {
>      a[b[i]] = c[i] + d[i];
>      c[i] = c[i  - 1] + 1; 
> }
> 
> Loop A is parallel and Loop B has non-simple dependences(LAI bails out) for
both the cases we get an empty set of dependences.
> 
> Is there an API that can tell if LAI was successful in dependence
computation?
I think canVectorizeMemory should do what you want (possibly in combination with
getMaxSafeDepDistBytes

Cheers,
Florian
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