[llvm-dev] Passing llvm option -mem2reg to clang

Tue Mar 22 08:05:25 PDT 2016

I tried with -mllvm -mem2reg in different ways to fit mem2reg with
clang. I used the following command:

clang -Xclang -mllvm -mem2reg -Xclang -load -Xclang myPass.so -c
../../tests/testIfElse.c

However, it does not work as it gives the error below:
clang-3.8: error: unknown argument: '-mem2reg'

Then I wrote a pass similar to PmotePass (mem2reg), added it as
dependency pass. It works fine with opt. Then I tried to load my
passes with clang using this command:

clang -Xclang -load -Xclang myPass.so -c ../../tests/testIfElse.c

 It does not throw any error, however, I found that my pass did not
run and I became sure of that as I could not see any debug messages.
Also, the clang command did not create the corresponding binary.

Could any of you please give any hint what I am doing wrong with clang?

Thanks,
Syed

On Tue, Mar 22, 2016 at 10:15 AM, mats petersson <mats at planetcatfish.com> wrote:
> Unless mem2reg does something other than my understanding of it, I can't see
> why any pass would "require" that... It is not guaranteed to do anything to
> any particular piece of code, so relying on it seems very unreliable, I
> would think.
>
> --
> Mats
>
> On 22 March 2016 at 04:32, Kevin Hu via llvm-dev <llvm-dev at lists.llvm.org>
> wrote:
>>
>> Hi,
>>
>> > Is there any way that I can mention mem2reg (PromotePass) pass as a
>> > pre-requisite in my own pass's implementation?
>>
>> I think you can consider overriding the
>> Pass::getAnalysisUsage(AnalysisUsage &)
>> method. Described as follows in manual:
>>
>>
>> http://www.llvm.org/docs/doxygen/html/classllvm_1_1Pass.html#a048082a5be9ae0d8901ea64de59e5c8f
>>
>> In your own pass in method getAnalysisUsage(Analysis &AU), you can add
>> required
>> pass by:
>>
>> AU.addRequired<PassName>();
>>
>> And get the analysis from the pass:
>>
>> PassName &P = getAnalysis<PassName>();
>>
>> See:
>>
>>
>> http://www.llvm.org/docs/doxygen/html/classllvm_1_1Pass.html#ab78af013d3a11515403da8517f8f3d4a
>>
>> Remember to include the necessary header files. This is a way of making
>> sure your
>> pass always rely on the other passes you want.
>>
>> BTW I also have a question for the mailing list, is it acceptable to allow
>> an analysis
>> pass to depend on a transformation pass (like -mem2reg pass)? Is this
>> acceptable so long
>> as it doesn't cause loop dependencies?
>>
>>
>> Regards,
>> Kevin
>>
>>
>> On Mon, Mar 21, 2016 at 09:30:32PM -0400, Syed Rafiul Hussain via llvm-dev
>> wrote:
>> > I have used the following command for my pass (without -mem2reg):
>> >
>> > clang -Xclang -load -Xclang MYPASS.so -c ../../tests/test1.c
>> >
>> >
>> > For mem2reg, I tried the following:
>> >
>> > clang -mllvm -mem2reg -Xclang -load -Xclang MYPASS.so -c
>> > ../../tests/test1.c
>> >
>> >
>> >
>> >
>> > On Mon, Mar 21, 2016 at 9:26 PM, Mehdi Amini <mehdi.amini at apple.com>
>> > wrote:
>> > >
>> > >> On Mar 21, 2016, at 6:23 PM, Syed Rafiul Hussain
>> > >> <rafiul1906 at gmail.com> wrote:
>> > >>
>> > >> I have my own llvm pass which requires mem2reg.  It worked fine with
>> > >> opt. However, I was trying to make it work with clang as I needed it
>> > >> to run some spec cpu benchmarks.
>> > >>
>> > >> Is there any way that I can mention mem2reg (PromotePass) pass as a
>> > >> pre-requisite in my own pass's implementation?
>> > >
>> > > How are you inserting your pass in the pipeline setup by clang?
>> > > You should be able to insert mem2reg before the same way.
>> > > Also mem2reg is ran by clang when optimizations are enabled, depending
>> > > on what your pass is doing it may be a matter of inserting it at the right
>> > > place.
>> > >
>> > > --
>> > > Mehdi
>> > >
>> > >
>> > >>
>> > >>
>> > >> On Mon, Mar 21, 2016 at 9:01 PM, Mehdi Amini <mehdi.amini at apple.com>
>> > >> wrote:
>> > >>> Hi,
>> > >>>
>> > >>> You can't schedule passes from the command line using clang, only
>> > >>> `opt` has this ability (AFAIK).
>> > >>>
>> > >>> If you tell us what is your use-case, we may be able to point you to
>> > >>> an alternative solution.
>> > >>>
>> > >>> --
>> > >>> Mehdi
>> > >>>
>> > >>>> On Mar 21, 2016, at 5:52 PM, Syed Rafiul Hussain via llvm-dev
>> > >>>> <llvm-dev at lists.llvm.org> wrote:
>> > >>>>
>> > >>>> Hi,
>> > >>>>
>> > >>>> I was trying to pass llvm option -mem2reg to clang using -mllvm and
>> > >>>> I
>> > >>>> found the following error:
>> > >>>>
>> > >>>> clang (LLVM option parsing): Unknown command line argument
>> > >>>> '-mem2reg'.
>> > >>>> Try: 'clang (LLVM option parsing) -help'
>> > >>>> clang (LLVM option parsing): Did you mean '-debug'?
>> > >>>>
>> > >>>> I would appreciate if anyone could help me.
>> > >>>>
>> > >>>> --
>> > >>>> Syed Rafiul Hussain
>> > >>>> _______________________________________________
>> > >>>> LLVM Developers mailing list
>> > >>>> llvm-dev at lists.llvm.org
>> > >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> > >>>
>> > >>
>> > >>
>> > >>
>> > >> --
>> > >> Rafi
>> > >
>> >
>> >
>> >
>> > --
>> > Rafi
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > llvm-dev at lists.llvm.org
>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
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>
>

-- 
Rafi