[LLVMdev] Code generation support in llvm for windows phone

Sat Jun 7 10:06:37 PDT 2014

Hi Saleem,
I have a similar situation - I'd appreciate your inputs on it. I noticed
that the obj file generated using llvm does not contain "thumb"
instructions. I suspect that is what is causing runtime crash for me.

Here's what I've tried -
Start with a.c (on my linux machine where I have llvm/clang built as of
yesterday)
                      int add(int i, int j) {int k = i + j; return k; }
clang  -S  -O0  a.c
llc -filetype=obj -mtriple=thumbv7-windows -O0 a.ll

I get a.obj from the above steps.

I take this a.obj over to my windows 8.1 machine where I have VS2013 update
2 installed

I open up a command window and run
C:\Users\kck\arm>"c:\Program Files (x86)\Microsoft Visual Studio
12.0\vc\bin\x86_arm\vcvarsx86_arm.bat"

I create a file file m.c
int main() { return add(20,30);}

I build the whole thing like this -

cl m.c a.obj

Things seem  to work fine and m.exe gets generated.

However I noticed a difference in the dumpbin output for a.obj and m.obj -
In m.obj, I can see "Thumb instructions" where as in a.obj, I don't see
that.

I'd appreciate any pointers on this.

Regards,
Kashyap

On Fri, May 30, 2014 at 10:45 PM, Saleem Abdulrasool <abdulras at fb.com>
wrote:

>
> On May 28, 2014, at 5:18 AM, Rajat Mahajan <rmahajan at adobe.com> wrote:
>
> > I am talking about Windows Mobile 8 and 8.1 and not CE.
> > Not sure though that the Windows 8 (ARM NT) is similar to Windows Mobile
> 8 platform.
> >
> > I used the following command to generate the obj file
> >    Llc.exe -mtriple=thumbv7-windows  -filetype=obj  <some_name>.bc
> >
> > The object file generated in the above object doesn't get linked when I
> try to link it with the windows mobile library as it fails to recognize the
> object format.  ( Not a valid object file )
> >
> > Hope I am clear.
>
> Unfortunately, you have merely repeated your previous statement.  I don’t
> have enough here to diagnose nor even speculate what is going on.
>
> If you can provide the object file, it would be helpful as I am unable to
> reproduce this issue.  Although, I ran it via clang, I see no reason that
> the output would be different as the backend is the same.
>
> The triple is certainly correct (particularly for llc, clang will treat
> armv7-windows as thumbv7-windows).  How did you generate the bit code?  My
> testing has usually started from C or LLVM IR rather than bit code, but, I
> suspect that shouldn’t be a real issue.
>
> With the given information, the only thing that comes to mind is that your
> environment is setup improperly, resulting in the wrong link.exe being
> invoked.
>
> > ~rajat
> >
> > -----Original Message-----
> > From: Saleem Abdulrasool [mailto:abdulras at fb.com]
> > Sent: Friday, May 16, 2014 11:23 PM
> > To: Rajat Mahajan
> > Cc: llvmdev at cs.uiuc.edu
> > Subject: Re: [LLVMdev] Code generation support in llvm for windows phone
> >
> >
> > On May 16, 2014, at 6:53 AM, Rajat Mahajan <rmahajan at adobe.com> wrote:
> >
> >> Hi,
> >>
> >> Is there support available in llc to convert llvm bytecode to Windows
> Mobile binary?
> >> I have tried triples like arm-pc-win32 , thumbv7-window ... but the
> object file generated is not getting linked to the windows native project.
> >> Any pointers will be greatly appreciated?
> >
> > As Reid mentioned, I have been working on this recently.  Just to make
> sure that we are talking about the same environment, I assume that you are
> talking about Windows 8 (ARM NT) rather than the Windows CE based
> environment.
> >
> > Can you please explain what exactly you mean by "the object file
> generated is not getting linked to the windows native project".  The object
> file that we generate should be pretty compatible with MSVC.  If you have
> specific cases where we are generating something that is incompatible, I
> would be quite interested in hearing about that.
> >
> >> Thanks,
> >> ~rajat
> >> _______________________________________________
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> >
> > --
> > Saleem Abdulrasool
> > abdulras (at) fb (dot) com
> >
> >
> >
> >
> >
>
> --
> Saleem Abdulrasool
> abdulras (at) fb (dot) com
>
>
>
>
>
>
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