[LLVMdev] LLVM IR on different platforms

[Andreas Weber]

As far as I know Java follows "compile once, run anywhere", so as long as
you target the same Java edition (Java EE/Java SE/Java ME/etc.) every
standard compliant JVM should execute the same bytecode correctly.

2015-07-07 10:04 GMT+02:00 Sandeep Kumar Singh <deepdondo007 at gmail.com>:

> Hi Andreas,
>
> Thanks for detailed explanation. Now it is very clear to me that I should
> write first platform independent code to make it work correct.
> As I know, Java is platform independent, will I face the same issue with
> it?
>
> Thanks and Regards,
> Sandeep
>
> On Tue, Jul 7, 2015 at 1:14 PM, Andreas Weber <andreas.c.weber at gmail.com>
> wrote:
>
>> Hi Sandeep,
>>
>> As far as I know, it depends: If you have portable C/C++ source (e.g.
>> with ifdefs to handle platform specific stuff) you can compile this source
>> with the Linux-defines on Linux to generate a working Linux binary or you
>> can compile the same source on Windows with the Windows-defines to generate
>> a working Windows binary.
>>
>> As LLVM/clang is inherently a cross-compiler you can also generate the
>> windows object files on Linux when you pass the correct target triple and
>> the Windows-defines to your Linux-clang or vice-versa. Note that this will
>> only give you object files which you still need to link to obtain a working
>> executable (usually with your system linker, link.exe on Windows, ld on
>> Linux).
>>
>> What will not work is compiling the source with a Linux target triple and
>> Linux-defines into bitcode and then compile this bitcode into a Windows
>> object file and expect it to link and run correctly. The reason is that the
>> bitcode already encodes target specific information as it represents
>> preprocessed code and was generated to target a specific platform ABI
>> defining stuff like name mangeling, struct and vtable layout, exception
>> handling, calling convention, etc.
>>
>> You might get away compiling a Linux-bitcode file into a working Windows
>> object file when you restrict yourself to platform independent C (the
>> preprocessed source is identical on Windows on Linux) and have only scalar
>> values as function parameters but I would not recommend this approach.
>>
>> Best regards
>> Andreas
>>
>> 2015-07-07 8:13 GMT+02:00 Sandeep Kumar Singh <deepdondo007 at gmail.com>:
>>
>>> Hi,
>>>
>>> I am curious to know about LLVM IR as platform independent feature.
>>> I have compiler some C and C++ applications that compiled on Linux 64bit
>>> machine, now I want to generate bit code file on Windows 64bit machine.
>>>
>>> 1) Will this execute without any issues?
>>> 2) Do I pass any option for making it operating system portable?
>>> 3) Can I generate bit code file also on Linux machine and then run on
>>> Windows machine?
>>>
>>> Please give me some pointers?
>>>
>>> Any help will be highly appreciated.
>>>
>>>
>>> Thanks and Regards,
>>> Sandeep
>>>
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>>>
>>>
>>
>
>
> --
>
> Thanks and Regards,
> Sandeep Kumar Singh
>
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