[llvm-dev] Replace "while" "for" loops with "If-Else"

[Michael Kruse via llvm-dev]

I am not sure I understand the problem statement. If the max iteration
count is statically known, any loop nest can be unrolled. Otherwise, I
don't see how one can remove such loops. Recursion maybe?

Polly does not implement loop flattening. That is, there's a "flatten
schedule" pass which would theoretically do this (if loop iteration
count is known), but it is not meant for production use.

Michael


2017-10-23 15:02 GMT+02:00 陳韋任 via llvm-dev <llvm-dev at lists.llvm.org>:
> You can give Polly [1] a shot. I'm not aware of existing pass does similar
> work.
>
> [1] http://polly.llvm.org/
>
> 2017-10-23 2:32 GMT+08:00 Shen Liu <sxl463 at gmail.com>:
>>
>> Hi weiren,
>>
>> Thanks for your suggestion! Yes, I am trying to do this "nested
>> flattening". It seems that I need a post-dominator tree-based algorithm to
>> flatten the nested loops from the innermost to the outermost, level by
>> level.
>>
>> Is there any feature already existed in LLVM tools? Or similar?
>>
>>
>>
>> On Sun, Oct 22, 2017 at 2:31 AM, 陳韋任 <chenwj.cs97g at g2.nctu.edu.tw> wrote:
>>>
>>> If the inner loop can be flatten [1] (not sure if I use the right word),
>>> which means transforming the nested loop into 1-level loop, I think you can
>>> continue using your pass on it.
>>>
>>> [1]
>>> https://stackoverflow.com/questions/18369260/flattening-a-very-nested-loop
>>>
>>> HTH,
>>> chenwj
>>>
>>>
>>> 2017-10-22 13:51 GMT+08:00 Shen Liu via llvm-dev
>>> <llvm-dev at lists.llvm.org>:
>>>>
>>>> Hi everyone,
>>>>
>>>> I hope to implement a feature to transform an IR with "while" or "for"
>>>> loops to a new IR with no loop. Instead, I just want to use if-else
>>>> statements in the new IR to implement the original semantics.
>>>>
>>>> I can easily write a transform pass to handle the 1-level loop case, but
>>>> for nested loops it seems a little harder.
>>>>
>>>> Can you show me some hints? Thank you very much!
>>>>
>>>> Best regards,
>>>>
>>>> Shen
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>
>>>
>>>
>>> --
>>> Wei-Ren Chen (陳韋任)
>>> Homepage: https://people.cs.nctu.edu.tw/~chenwj
>>
>>
>
>
>
> --
> Wei-Ren Chen (陳韋任)
> Homepage: https://people.cs.nctu.edu.tw/~chenwj
>
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