[llvm-dev] What's LLVM{target}CodeGen vs {target}CodeGen?

[Justin Bogner via llvm-dev]

Robert Baruch via llvm-dev <llvm-dev at lists.llvm.org> writes:
> Hi all,
>
> *TL;DR:* I have a target TMS9900CodeGen but cmake is looking for LLVMTMS9900
> or LLVMTMS9900CodeGen which I don't have, and cmake dies. But the MSP430 target
> doesn't have that either, and cmake is happy with it. What am I missing?
>
> *The premise:*
>
> I may be making a huge mistake, but I'm trying to develop an LLVM backend.
> I'm writing up some notes while I do so, and I hope to update the
> documentation. However, I ran into a bit of a problem running cmake. Note
> that I built the trunk release just fine, right now I'm modifying it.
>
> *The setup:*
>
> My target is called TMS9900 because I'm a masochist, and I'm just trying to
> make a bare do-nothing skeleton to start with. I have this:
>
> lib/Target/TMS9900
>   - CMakeLists.txt
>   - LLVMBuild.txt
>   - TMS9900TargetMachine.cpp
>   - TMS9900TargetMachine.h
>   - TMS9900.td
>
> TMS9900TargetMachine is the barest class I could make. It derives from
> LLVMTargetMachine, and passes everything through (although it defines the
> DataLayout).
>
> CMakeLists.txt is also pretty small:
>
> set(LLVM_TARGET_DEFINITIONS TMS9900.td)
>
> add_llvm_library(TMS9900CodeGen
>   TMS9900TargetMachine.cpp
>   )

This should be add_llvm_target, rather than add_llvm_library. This does
some extra work, including calling the target LLVMXYZ rather than just
XYZ.

> LLVMBuild.txt is as minimal as I could guess at:
>
> [common]
> subdirectories =
>
> [component_0]
> type = TargetGroup
> name = TMS9900
> parent = Target
>
> [component_1]
> type = Library
> name = TMS9900CodeGen
> parent = TMS9900
> required_libraries = Analysis AsmPrinter CodeGen Core MC Scalar
> SelectionDAG Support Target TransformUtils
> add_to_library_groups = TMS9900
>
> And finally, TMS9900.td contains:
>
> include "llvm/Target/Target.td"
> def TMS9900 : Target { }
>
> I also updated lib/Target/LLVMBuild.txt's [common] subdirectories to
> include TMS9900.
>
> *The punchline:*
>
> Now, I tried to run cmake:
>
> $ cd build
> $ cmake -G "Unix Makefiles" -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=TMS9900
> ../llvm
> ... stuff ...
> CMake Error at cmake/modules/LLVM-Config.cmake:178 (message):
>   Target TMS9900 is not in the set of libraries.
> Call Stack (most recent call first):
>   cmake/modules/AddLLVM.cmake:525 (llvm_map_components_to_libnames)
>   cmake/modules/AddLLVM.cmake:574 (llvm_add_library)
>   tools/lto/CMakeLists.txt:19 (add_llvm_library)
>
> (Line numbers may be off slightly, since I added some message() lines). So
> I tracked this error down to where LLVM-Config.cmake is looking for targets
> whose name, given {target}, is either LLVM{target} or LLVM{target}CodeGen.
>
> Of course, I have no such targets.
>
> The weird thing is that I looked at the MSP430 directory, and it does not
> have LLVMMSP430 or LLVMMSP430CodeGen, either. It just has MSP430CodeGen yet
> somehow that target works just fine.
>
> *What am I missing?*
>
> Thanks!
>
> --Rob
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