[PATCH] D99354: [SimpleLoopUnswitch] Port partially invariant unswitch from LoopUnswitch to SimpleLoopUnswitch

[JinGu Kang via Phabricator via llvm-commits]

jaykang10 added a comment.

In D99354#2951701 <https://reviews.llvm.org/D99354#2951701>, @jaykang10 wrote:

> In D99354#2949165 <https://reviews.llvm.org/D99354#2949165>, @jaykang10 wrote:
>
>> In D99354#2949059 <https://reviews.llvm.org/D99354#2949059>, @xbolva00 wrote:
>>
>>> In D99354#2912791 <https://reviews.llvm.org/D99354#2912791>, @jaykang10 wrote:
>>>
>>>> In D99354#2903817 <https://reviews.llvm.org/D99354#2903817>, @fhahn wrote:
>>>>
>>>>> @jaykang10 it looks like this patch regressed codegen in some cases: https://bugs.llvm.org/show_bug.cgi?id=51139. It would be great if you could take a look.
>>>>
>>>> Ah, let me have a look.
>>>
>>> Maybe revert while investigating?
>>
>> As I mentioned on https://bugs.llvm.org/show_bug.cgi?id=51141, I am not sure the unswitch pass has to detect the cases which the loop load pre, sccp or other passes can optimize and the pass do not unswitch the loop...
>> I am creating a patch to fix https://bugs.llvm.org/show_bug.cgi?id=51141 first. The patch does not fix https://bugs.llvm.org/show_bug.cgi?id=51139. Once I create it, let me add you as reviewer.
>
> For https://bugs.llvm.org/show_bug.cgi?id=51139, I have added below comment on it.
>
>   In this case, the inliner pass fails to inline the function g after unswitch because of the cost as below debug message.
>   
>   NOT Inlining (cost=250, threshold=250), Call:   call void @g(i32 %2) #3
>   
>   Originally, after inlining function g, the JumpThreading pass made the block with call @foo dead and SimplifyCFG pass deleted it.
>   
>   If you add `always_inline` attribute to the function g's prototype as below, you can see the callfoo is gone.
>   
>   void g(int h) __attribute__((always_inline));
>
> In this case, as I mentioned previously, I am not sure the unswitch pass has to check the inline cost or something like that... If someone has idea about it, please let me know.

The SimpleUnswitchPass checks the cost of duplicating the loop so we could adjust it. Let me try to adjust the cost calculation for partially invariant unswitch.


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