[llvm-dev] bug report on mem2reg

[David Blaikie via llvm-dev]

This is still a rather long test case - I expect it should be able to be
reduced further while still demonstrating the problem.

I also don't understand what the correct/incorrect behavior it is you're
looking for - at least casually, the program prints the same result at -O0,
which doesn't run mem2reg, and at -O3 which does run mem2reg.

On Thu, May 14, 2020 at 5:14 PM liubaosen at tsinghua.edu.cn <
liubaosen at tsinghua.edu.cn> wrote:

> Hi, David, and anyone regards,
> Thanks for discussing. I meant you can run the main.c with what I affixed
> in last mail. Anyway, I reprepared a complete while least pack of codes,
> which is affixed. I've tried it with following process,
>
> clang colapse.c -o colapse
> ./colapse
> valgrind --tool=memcheck --leak-check=yes ./colapse
>  clang colapse.c -emit-llvm -g -c -S -o colapse.ll -Xclang
> -disable-O0-optnone
>  opt -mem2reg -da -analyze colapse.ll
>
> so, principly, it is for sure able to recur. There are totally 3 functions
> can cause collapses (maybe by a same reason), and all of them are contained
> in the file. Please help me debug it.
>
> Thanks again.
>
> ------------------------------
> liubaosen at tsinghua.edu.cn
>
>
> *From:* David Blaikie <dblaikie at gmail.com>
> *Date:* 2020-05-15 06:31
> *To:* liubaosen at tsinghua.edu.cn; llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* Re: Re: [llvm-dev] bug report on mem2reg
> Sorry, I'm not sure I'll be able to help you - main.c uses other code
> (optsfind/check/etc) that I don't have/don't know what that code is, and
> even with it it's probably a bit big/complicated for me to
> debug/reduce/etc. If you can reconstruct the smallest complete (reducing
> the total lines of all source/header files needed to reproduce the problem)
> example that might be more practical to discuss here & see whether it's a
> mem2reg bug, etc.
>
> On Wed, May 13, 2020 at 6:52 PM liubaosen at tsinghua.edu.cn <
> liubaosen at tsinghua.edu.cn> wrote:
>
>> Hi, David and anyone relevent,
>>
>> Thank you for replying, first.
>> I tried it with valgrind, no error is reported, so I'm sure it's not our
>> problem.
>> The valgrind log is affixed and a mian.c which you may need to generate
>> an executable is also affixed.
>> Please do me a favor and investigate what causes the colapse. Your help
>> will be greatly appreciated.
>>
>> Best regards
>>
>> ------------------------------
>> liubaosen at tsinghua.edu.cn
>>
>>
>> *From:* David Blaikie <dblaikie at gmail.com>
>> *Date:* 2020-05-12 11:45
>> *To:* liubaosen at tsinghua.edu.cn
>> *CC:* llvm-dev <llvm-dev at lists.llvm.org>
>> *Subject:* Re: [llvm-dev] bug report on mem2reg
>> Tried testing it with things like Undefined Behaivor Sanitizer (or other
>> sanitizers - memory/address) or valgrind?
>>
>> Often "program works sometimes and doesn't work other times" is
>> because the program has undefined behavior in it & the times its working
>> are just luck.
>>
>> On Mon, May 11, 2020 at 8:41 PM liubaosen at tsinghua.edu.cn via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi, all,
>>>
>>> I think I found a bug on mem2reg in a particular case.
>>> When I ran opt -mem2reg -basicaa -scalar-evolution -loops -da -analyze
>>> opts.ll, it collapsed. While without mem2reg option, it runs well. so I
>>> guess it has something to do with mem2reg.
>>> The relative files have been affixed, please check them for me.
>>> Thanks in advance.
>>>
>>> ------------------------------
>>> liubaosen at tsinghua.edu.cn
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
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