[LLVMdev] Question about SPARC target status
clattner at apple.com
Tue Nov 11 11:01:23 PST 2008
On Nov 11, 2008, at 10:48 AM, Luke K. Dalessandro wrote:
> On Tue, 11 Nov 2008, Peter Shugalev wrote:
>> Anton Korobeynikov wrote:
>>>> I thought llvm-gcc isn't meant to compile for specific target (at
>>>> with -emit-llvm flag I'm using).
>>> No, it is not. C language is highly target-specific, thus LLVM IR
>>> obtained from such sources also has the same nice 'property'
>> 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?
> I had trouble with this too -- I still haven't entirely figured it
> Try browsing through http://www.gaisler.com/doc/sparc-abi.pdf which is
> the SPARC ABI. It explains things like structure padding and stack
> layout/function calling. llvm-gcc has to make lots of decisions
> on this ABI when converting C/C++ to IR. I imagine that every
> platform has
> its own rules.
> The SPARC rules actually seem relatively straightforward.
I'd expect llvm-gcc to get the structure layout rules "for free". You
could write some testcases to verify this. The case that requires a
bit of work are the various parameter passing cases if there is
weirdness. When I was working on the sparc backend, just about
everything was passing in llvm-test, so I think it is pretty close to
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