llvm dev - Mar 2019 - LLVM target as loadable module

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

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
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


-- 
With best regards, Anton Korobeynikov
Department of Statistical Modelling, Saint Petersburg State University