[PATCH] D107083: [AArch64] Unroll loop with iv of pointer type

[JinGu Kang via Phabricator via llvm-commits]

jaykang10 added a comment.

In D107083#2913968 <https://reviews.llvm.org/D107083#2913968>, @nikic wrote:

> This looks very dubious. `UP.Force` means that you are unrolling without folding //anything//. You just repeat the loop body and keep //all// the branches. This is unlikely to be profitable in general.
>
> Note that this has nothing to do with pointer types -- you simply have a loop where the only exit is unpredictable.

@nikic Thanks for your comment. Let me explain something more.

If the IV's type is pointer type, we can see `gep` for the IV.

AArch64 has pre/post indexing address mode. If we unroll loop with IV of pointer type which is `gep`, there will be more opportunities in order to generate instructions with the pre/post indexing address mode. That's why I mentioned the IV of pointer type and try to unroll the loop with it even though the exit count is not computable.

I need to add heuristics to recognize the profitable case in general. I am trying to get performance number in order to do it.

I am sorry for poor example and explanation...

If you feel something wrong, please let me know. I would like to discuss it and get ideas more.


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