[llvm-dev] LLVM target as loadable module

[Anton Korobeynikov via llvm-dev]

Hello

You're not missed anything – targets can only be built-in due to way
how they are registered, etc.

On Wed, Mar 20, 2019 at 7:55 AM Ottet Loïc via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Hi,
>
> I’m trying to implement a custom target for LLVM (version 6.0.1) based on the X86 target as a loadable module to use it with llc’s -load option. I have defined the module in the CMakeLists.txt file in the target folder as:
>
> add_llvm_loadable_module(MyTarget ${sources}
>   AsmParser/X86AsmInstrumentation.cpp
>   AsmParser/X86AsmParser.cpp
>   Disassembler/X86Disassembler.cpp
>   Disassembler/X86DisassemblerDecoder.cpp
>   InstPrinter/X86ATTInstPrinter.cpp
>   InstPrinter/X86IntelInstPrinter.cpp
>   InstPrinter/X86InstComments.cpp
>   MCTargetDesc/X86AsmBackend.cpp
>   MCTargetDesc/X86MCTargetDesc.cpp
>   MCTargetDesc/X86MCAsmInfo.cpp
>   MCTargetDesc/X86MCCodeEmitter.cpp
>   MCTargetDesc/X86MachObjectWriter.cpp
>   MCTargetDesc/X86ELFObjectWriter.cpp
>   MCTargetDesc/X86WinCOFFObjectWriter.cpp
>   MCTargetDesc/X86WinCOFFStreamer.cpp
>   MCTargetDesc/X86WinCOFFTargetStreamer.cpp
>   TargetInfo/X86TargetInfo.cpp
>   Utils/X86ShuffleDecode.cpp
> )
>
> I also defined new versions of the LLVMInitializeMyTarget(AsmPrinter|Target|AsmParser|Disassembler|TargetMC|TargetInfo) functions. The shared module gets created, but when I load it into llc the target is not present in the list of loaded targets (from llc -version) and I cannot use it with -march=mytarget. However, when I use the llc binary that was compiled with my custom target, and load the module with it, I get errors because of duplicated options, meaning that the custom target is, in fact, loaded from the module in this case.
>
> What am I missing here? The documentation I’ve been able to find on loadable modules seems to be targeted at previous versions of LLVM which use the LOADABLE_MODULE makefile value instead of the current cmake compilation pipeline.
>
> Cheers,
>
> Loïc
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-- 
With best regards, Anton Korobeynikov
Department of Statistical Modelling, Saint Petersburg State University