llvm dev - May 2016 - Passing structs in C calling convention

Hi,

I want to declare a function that matches C ABI. Do I need to transform
declarations like void @f(%struct.A %a) into void @f(%struct.A* byval %a)
myself or LLVM can do it for me? Is this what "ccc" calling convention
means?

- Paweł
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LLVM doesn't have enough information to do it for you. The LLVM type system
just isn't as expressive as the C type system, so frontends end up bearing
some of the lowering burden.

You should consider using clang to do the lowering for you:
http://llvm.org/devmtg/2014-10/Slides/Skip%20the%20FFI.pdf

On Fri, May 6, 2016 at 4:32 AM, Paweł Bylica <llvm-dev at lists.llvm.org>
wrote:
> Hi,
>
> I want to declare a function that matches C ABI. Do I need to transform
> declarations like void @f(%struct.A %a) into void @f(%struct.A* byval %a)
> myself or LLVM can do it for me? Is this what "ccc" calling
convention
> means?
>
> - Paweł
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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Thanks for explaining that to me.

So the conclusion is to use IRGen from Clang to handle the lowering, right?
I will take a look there and try to use it. But that adds additional
dependency what's is not ideal.

On Fri, May 6, 2016 at 10:08 PM Reid Kleckner <rnk at google.com> wrote:
> LLVM doesn't have enough information to do it for you. The LLVM type
> system just isn't as expressive as the C type system, so frontends end
up
> bearing some of the lowering burden.
>
> You should consider using clang to do the lowering for you:
> http://llvm.org/devmtg/2014-10/Slides/Skip%20the%20FFI.pdf
>
> On Fri, May 6, 2016 at 4:32 AM, Paweł Bylica <llvm-dev at
lists.llvm.org>
> wrote:
>
>> Hi,
>>
>> I want to declare a function that matches C ABI. Do I need to transform
>> declarations like void @f(%struct.A %a) into void @f(%struct.A* byval
%a)
>> myself or LLVM can do it for me? Is this what "ccc" calling
convention
>> means?
>>
>> - Paweł
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
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