llvm-d

[Moritz Maxeiner]

On Saturday, 23 March 2013 at 10:31:30 UTC, Jens Mueller wrote:
> Moritz Maxeiner wrote:
>> On Saturday, 23 March 2013 at 09:30:07 UTC, Jens Mueller wrote:
>> >Moritz Maxeiner wrote:
>> >>A couple of more things I forgot to mention:
>> >>
>> >>- You will need to additionally add bindings for all the 
>> >>LLVMInitialize"TARGET_NAME"{TargetInfo,Target,TargetMC,AsmParser,AsmPrinter,Disassembler}
>> >>functions. They reside inside the target libraries and not
>> >>inside
>> >>llvm-c, which is why only translating the C API won't get you
>> >>them.
>> >>The LLVMInitializeNativeTarget function , which is necessary 
>> >>to
>> >>use
>> >>LLVM for jitting - otherwise you'll only have access to
>> >>interpreting, which is horribly slow - uses them, but it is a
>> >>static
>> >>inline function and as such does not get exposed because LLVM
>> >>builds
>> >>with the option to hide all inline functions. That is not a
>> >>problem
>> >>for C, as this function gets defined in the header, but for 
>> >>D it
>> >>is
>> >>a big problem, because you cannot access
>> >>LLVMInitializeNativeTarget.
>> >>You need to recreate it in D by using all the functions it
>> >>references. Of course, you'll also have to accomodate the 
>> >>fact
>> >>that
>> >>these referenced functions may or may not be compiled in
>> >>depending
>> >>on which target where selected when compiling LLVM.
>> >
>> >Do you happen to know why these functions are not declared in 
>> >the
>> >header
>> >files. I mean when using the C interface in C I wouldn't even 
>> >know
>> >that
>> >these functions exist.
>> 
>> I suspect it is because of LLVM's internal structure. Each 
>> supported
>> target is presented by its own directory and they are afaict
>> mutually independent from one another, "so their initialiation
>> routines should be part of them themselves" I would guess, but 
>> I
>> don't know, sorry.
>> Also, when using the C interface in C there is little need to 
>> know
>> them because they get encapsulated in LLVMInitializeAllTargets 
>> and
>> LLVMInitializeNativeTarget.
>
> Not sure whether this fixes the problem completely. Can you 
> check
> https://github.com/jkm/deimos-llvm/blob/master/deimos/llvm/c/target.d#L157
> I came up with this solution to replace the macros in the C 
> binding.

It looks mostly okay to me with one problem: Afaict the code 
enforces the presence of the initialization routines of all 
targets, e.g. if one target is missing LLVMInitializeAllTargets 
will not link, as there are undefined references for that missing 
target, but LLVM may or may not be compiled with that target so 
you cannot enforce its presence in the bindings. For runtime 
loading the solution I used was to check the function pointer for 
null; for linking you have this problem: When using linking, 
knowing which targets are available happens at link time (when 
the LLVM libraries are linked in), which means you cannot use any 
compile time tricks for automatic detection of which targets are 
available.
The only solution for that problem I can think of would be to use 
runtime reflection and check at runtime for each initialiation 
routine if it is a callable function, but afaik D only has 
compile time reflection.

- Moritz

PS: All your recent posts seem to create new threads, I don't 
know why, though, just mentioning it because some people not 
interested in this might get annoyed.