[PATCH] D93734: [LoopDeletion] Insert an early exit from dead path in loop

Florian Hahn via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Jan 29 10:49:09 PST 2021


fhahn added a comment.

In D93734#2529365 <https://reviews.llvm.org/D93734#2529365>, @jonpa wrote:

> In D93734#2524218 <https://reviews.llvm.org/D93734#2524218>, @jdoerfert wrote:
>
>>> I may be doing something wrong, but D95468 <https://reviews.llvm.org/D95468> did not help very much looking at these numbers it seems...
>>
>> Maybe outer loops have been skipped and therefore you avoided duplication of outer and inner loops (with D95468 <https://reviews.llvm.org/D95468>). The statistics we have are too coarse grained to exactly pinpoint what happened.
>
> I wonder what loops are those which where "partially unrolled", and which were not. Do the partially unrolled ones get some recognizable name maybe in the header blocks?

Do you mean partially unswitched or partially unrolled? I don't think so unfortunately. But  I think most cases where already caught with D95468 <https://reviews.llvm.org/D95468> and only in a few cases we now skip duplication. Also note that D95468 <https://reviews.llvm.org/D95468> adds the shortcut outside the loop, so `loop-deletion` will still insert an early exit as before (long term I think we could also just turn the branch in the loop into an early exit).


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