[LLVMdev] Question about SPARC target status

[Owen Anderson]

On Nov 11, 2008, at 2:19 PM, Peter Shugalev wrote:

> Hi,
>
> Owen Anderson wrote:
>>> I can see only one reason for such dependence: inclusion of system
>>> headers in /usr/include. If I compile llvm-gcc with predefined set  
>>> of
>>> Linux headers (the way cross-compilers are usually made) will the IR
>>> output be the same no matter which platform is used for compilation?
>>>
>>
>> No.  Consider use of sizeof(), ABI issues, etc.
>
> Ooh, now I see llvm-gcc is not cross-compiler in the terms of GCC.  
> Okay,
> but what if I actually compile LLVM-gcc as cross-compiler for 64-bit
> x86-64 Linux. Then it is guaranteed to produce identical output on all
> the systems.
>
> Question is: how the resulting LLVM IR will run on 32-bit machine?
> Should I create stubs for all called functions to convert between 32  
> and
> 64-bit pointers? Or it won't run at all?

If you configure it as a cross-compiler for 64-bit x86 Linux and feed  
it the appropriate header files, it will produce the same output on  
any platform.  However, that output will not be executable on most  
platforms, just on 64-bit x86 Linux.  The problems go beyond pointer  
size.  The size of int is implementation dependent, etc.  The layout  
and padding of structs is implementation dependent.  While all  
implementations on a given target-triple will generally agree to  
ensure binary compatibility, there is no guarantee of things being the  
same once you go to another target-triple.

--Owen

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