Hello,
I am looking for a loop unfolding procedure implemented in LLVM that helps
to transform a while-loop to n-layer If-statements. The transformation
should be on IR, although the example below is illustrated on the source
level.
original loop:
* WHILE (condition) DO
action
ENDWHILE*
Expected unfolded loop (2-layer):
* IF (condition) THEN*
* action*
* IF (condition) THEN*
* action*
* WHILE (condition) DO
action
ENDWHILE
*
* ENDIF*
* ENDIF*
(I thought such transformation is somewhat standard but do not find it the
related API of LLVM:loop:
http://llvm.org/docs/doxygen/html/classllvm_1_1Loop.html)
Thanks for your help.
Sincerely,
Zhoulai
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20150607/4c3b0313/attachment.html>
What is the use-case that makes this better than the following?
WHILE (condition) DO
action
IF (condition) THEN
action
IF (condition) THEN
action
ENDIF
ENDIF
ENDWHILE
If your loop normally gets executed a lot of times, then even this should
be better, with one fewer duplication of "action"?
WHILE (condition) DO
action
IF (condition) THEN
action
ENDIF
ENDWHILE
On Sun, Jun 7, 2015 at 8:24 PM, Zhoulai <zell08v at gmail.com> wrote:
> Hello,
>
> I am looking for a loop unfolding procedure implemented in LLVM that helps
> to transform a while-loop to n-layer If-statements. The transformation
> should be on IR, although the example below is illustrated on the source
> level.
>
> original loop:
>
> * WHILE (condition) DO
> action
> ENDWHILE*
>
> Expected unfolded loop (2-layer):
>
>
> * IF (condition) THEN*
>
>
> * action*
>
>
> * IF (condition) THEN*
>
>
> * action*
>
> * WHILE (condition) DO
> action
> ENDWHILE
> *
>
>
> * ENDIF*
> * ENDIF*
>
>
> (I thought such transformation is somewhat standard but do not find it the
> related API of LLVM:loop:
> http://llvm.org/docs/doxygen/html/classllvm_1_1Loop.html
>
<https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_docs_doxygen_html_classllvm-5F1-5F1Loop.html&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=Mfk2qtn1LTDThVkh6-oGglNfMADXfJdty4_bhmuhMHA&m=yM0Vi5USSIlDTpHDzlYOLQJuCxxBQnb1HDijbKLUPIA&s=kcfE20E9Tv_peJ2EC7XSVgW0btFfF-joP8HfqPyWes4&e=>
> )
>
> Thanks for your help.
>
> Sincerely,
> Zhoulai
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20150608/01837def/attachment.html>
Thanks Bruce. I agree your way to unfold can be shown more interesting. My question was *how to do this kind of unfolding in LLVM *? Because such program transformation is standard in compiler textbooks, one may expect it is already implemented in LLVM, so we do not need to do this by ourselves (such as, detecting the loop head, inserting conditional statement, copying basic blocks, etc, which can be tedious). As mentioned earlier, I would like to unfold the loops at the IR level, although the source code was being used as illustration. Thanks. Zhoulai On Mon, Jun 8, 2015 at 1:21 AM, Bruce Hoult <bruce at hoult.org> wrote:> What is the use-case that makes this better than the following? > > WHILE (condition) DO > action > IF (condition) THEN > action > IF (condition) THEN > action > ENDIF > ENDIF > ENDWHILE > > > If your loop normally gets executed a lot of times, then even this should > be better, with one fewer duplication of "action"? > > WHILE (condition) DO > action > IF (condition) THEN > action > ENDIF > ENDWHILE > > > > On Sun, Jun 7, 2015 at 8:24 PM, Zhoulai <zell08v at gmail.com> wrote: > >> Hello, >> >> I am looking for a loop unfolding procedure implemented in LLVM that >> helps to transform a while-loop to n-layer If-statements. The >> transformation should be on IR, although the example below is illustrated >> on the source level. >> >> original loop: >> >> * WHILE (condition) DO >> action >> ENDWHILE* >> >> Expected unfolded loop (2-layer): >> >> >> * IF (condition) THEN* >> >> >> * action* >> >> >> * IF (condition) THEN* >> >> >> * action* >> >> * WHILE (condition) DO >> action >> ENDWHILE >> * >> >> >> * ENDIF* >> * ENDIF* >> >> >> (I thought such transformation is somewhat standard but do not find it >> the related API of LLVM:loop: >> http://llvm.org/docs/doxygen/html/classllvm_1_1Loop.html >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_docs_doxygen_html_classllvm-5F1-5F1Loop.html&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=Mfk2qtn1LTDThVkh6-oGglNfMADXfJdty4_bhmuhMHA&m=yM0Vi5USSIlDTpHDzlYOLQJuCxxBQnb1HDijbKLUPIA&s=kcfE20E9Tv_peJ2EC7XSVgW0btFfF-joP8HfqPyWes4&e=> >> ) >> >> Thanks for your help. >> >> Sincerely, >> Zhoulai >> >> _______________________________________________ >> LLVM Developers mailing list >> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev >> >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150608/e662474d/attachment.html>