[llvm-dev] Building A Project Against LLVM

Sat May 16 23:55:23 PDT 2020

The "all" option did work on the LLVM 6 that was bundled with Ubuntu.
Unfortunately I jumped from that up to LLVM 10 (downloaded from
https://releases.llvm.org/download.html and extracted into /usr/local), so
can't say whether it worked on LLVM 9.

On Sat, May 16, 2020 at 9:21 PM Mehdi AMINI <joker.eph at gmail.com> wrote:

>
>
> On Sat, May 16, 2020 at 12:07 AM Rarrum <rarrum at gmail.com> wrote:
>
>> I've managed to get 10.0.0 working now.. there were a couple things I had
>> to adjust.
>>
>> The Kaleidoscope example had me doing this before creating the object
>> file:
>> llvm::InitializeAllTargetInfos();
>> llvm::InitializeAllTargets();
>> llvm::InitializeAllTargetMCs();
>> llvm::InitializeAllAsmParsers();
>> llvm::InitializeAllAsmPrinters();
>>
>> It turns out I can get away with just this, since I'm not (yet) worried
>> about targeting other machines:
>> llvm::InitializeNativeTarget();
>> llvm::InitializeNativeTargetAsmPrinter();
>>
>> Since "all" doesn't work anymore for some reason
>>
>
> Did it use to work with LLVM 9? It may be worth investigating if this is
> the case.
>
>
>> , I've managed to (through trial and error, guessing at different names
>> shown from llvm-config --components) end up with this set of libnames:
>> llvm_map_components_to_libnames(llvm_libs core executionengine support
>> nativecodegen)
>>
>> That left me with 2 link errors referring to llvm::raw_ostream and
>> llvm::raw_pwrite_stream.  After much more digging through similar
>> complaints on the internet.. the last fix turned out to be adding this to
>> CMakeLists.txt:
>> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
>>
>> I am a little worried that the rtti flag may come back and bite me later
>> when I get around to building this on windows again (since I do use
>> exceptions), but that's a problem for another day.
>>
>
> You can build LLVM with RTTI enable if you need it.
>
>
>>
>>
>> One last question.. is there a good way to know which libnames I need,
>> based on which #includes I pull in or which classes I'm using?  I didn't
>> see anything obvious in the doxygen documentation.
>>
>
> LLVM includes are organized by subdirectory with a directory in the
> `include/llvm/` folder matching directories in `lib/` in general, and the
> lib name matches the component's name. If you include
> "llvm/Support/raw_ostream.h" you need `support`, if you include
>  "include/llvm/IRReader/IRReader.h" you need "irreader", etc. In general
> for the IR-level library this is fairly straightforward I think, but it
> becomes a bit more complex for the backends, jit, and these kind of things.
> There are also "pseudo components" like providing the name of a target
> would link all aspects of this targets, while using "AllTargetsAsmParsers"
> would link only the assembly parser for all available targets... I don't
> find a good doc on this unfortunately.
>
> --
> Mehdi
>
>
>
>
>>
>>
>> On Fri, May 15, 2020 at 8:57 PM Rarrum <rarrum at gmail.com> wrote:
>>
>>> I'd rather avoid updating my OS at the moment or setting up a VM.  But
>>> the cmake comments were a hint.. I suspect something is going wrong in
>>> there preventing it from adding the actual library files to the linker
>>> commandline.
>>>
>>> I added this to my CMakeLists.txt:
>>> set(CMAKE_VERBOSE_MAKEFILE on)
>>>
>>> Which shows no LLVM libs at all being passed in:
>>>
>>> [  8%] Linking CXX executable ../bin/CBreakCompiler
>>> /usr/bin/c++     CMakeFiles/CBreakCompiler.dir/src/main.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/Parser.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/SourceTokenizer.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/IRCompiler.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/JIT.cpp.o  -o ../bin/CBreakCompiler
>>>
>>> If I change this:
>>> llvm_map_components_to_libnames(llvm_libs all)
>>> to:
>>> llvm_map_components_to_libnames(llvm_libs core)
>>>
>>> Then I start to see libraries being added:
>>> [  8%] Linking CXX executable ../bin/CBreakCompiler
>>> /usr/bin/c++     CMakeFiles/CBreakCompiler.dir/src/main.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/Parser.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/SourceTokenizer.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/IRCompiler.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o
>>> CMakeFiles/CBreakCompiler.dir/src/JIT.cpp.o  -o ../bin/CBreakCompiler
>>> /usr/local/lib/libLLVMCore.a /usr/local/lib/libLLVMBinaryFormat.a
>>> /usr/local/lib/libLLVMRemarks.a /usr/local/lib/libLLVMBitstreamReader.a
>>> /usr/local/lib/libLLVMSupport.a -lrt -ldl -ltinfo -lpthread -lm
>>> /usr/local/lib/libLLVMDemangle.a
>>>
>>> Perhaps I can figure out which ones I need and manually specify them
>>> all, rather than using "all".
>>>
>>> On Fri, May 15, 2020 at 8:17 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>>>
>>>>
>>>>
>>>> On Fri, May 15, 2020 at 6:53 PM Neil Nelson via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Rarrum,
>>>>>
>>>>> Kubuntu 20.04 LTS is available. You may be able to upgrade to 19.10,
>>>>> and then to 20.04 without reinstalling. It can be done on Xubuntu. A direct
>>>>> upgrade to 20.04 should become available. LLVM 10 then installs from the
>>>>> distribution packages. I put all this on a VM using KVM/QEMU to keep it
>>>>> isolated from my primary desktop environment. Building a 20.04 VM after
>>>>> upgrading to 20.04 appears to give a faster VM. Use llvm's linker lld.
>>>>>
>>>>> The cmake version for 20.04 is 3.16.3 which should help with llvm's
>>>>> recommended version.
>>>>>
>>>>
>>>> Do you believe the error listed have to do with the CMake version?
>>>>
>>>>
>>>>
>>>>
>>>>> Neil
>>>>> On 5/15/20 12:05 AM, Rarrum via llvm-dev wrote:
>>>>>
>>>>> I decided to start playing around with building my own programming
>>>>> language recently, and to use LLVM to handle the assembly-level details.
>>>>> I'm on Kubuntu 18.04, and I started out using LLVM 6.0 from Kubuntu's
>>>>> packages.  I put together code for dealing with my language, then went over
>>>>> the Kaleidoscope tutorials (which have been extremely helpful btw!).  I was
>>>>> able to successfully get my own compiler to generate IR using LLVM, use
>>>>> PassManager to write that to a native .o file, use gcc to link that, and
>>>>> execute a tiny program written in my own language.
>>>>>
>>>>> I also decided it was a good time to learn CMake, so I set up my
>>>>> project using that.  The CMakeLists.txt file I'm using is essentially just
>>>>> taken from:
>>>>> https://llvm.org/docs/CMake.html#embedding-llvm-in-your-project -
>>>>> though originally it would not link.  From scouring the internet I made 2
>>>>> changes to get that working: replaced "support core irreader" with "all",
>>>>> and replaced "${llvm_libs}" with just "LLVM".
>>>>>
>>>>> However as I was starting to play with setting up JIT, I hit more
>>>>> differences between the version of LLVM in Kubuntu and the version the
>>>>> examples and documentation were written against.  So I decided to try to
>>>>> update to a newer version of LLVM.. and this is where I've been stuck for
>>>>> several days now.  Here are the steps I've taken:
>>>>>
>>>>> * Uninstalled any llvm packages I could find from Kubuntu's package
>>>>> manager.
>>>>> * Followed the getting started guide:
>>>>> https://llvm.org/docs/GettingStarted.html - I git cloned LLVM,
>>>>> checked out the 10.0.0 tag, ran cmake as instructed, with the Release
>>>>> type.  When that completed successfully I ran sudo ninja install.
>>>>> * I then went back to my project and adjusted a couple places to
>>>>> successfully compile against the new version.
>>>>> * At this point I put "${llvm_libs}" in the CMakeLists.txt file back
>>>>> to match the example.  However I was getting a massive wall of link errors.
>>>>> * I assumed I must have built LLVM incorrectly somehow, so in an
>>>>> effort to undo that install, I deleted everything I could find under
>>>>> /usr/local that had LLVM in its name, downloaded the 10.0 release from
>>>>> https://releases.llvm.org/download.html for ubuntu 18.04, and
>>>>> extracted that all to /usr/local.
>>>>> * I can still successfully compile, but not link.
>>>>>
>>>>> At this point I'm not sure what to try next.  Is there additional
>>>>> documentation somewhere for how to "install" a current release of LLVM
>>>>> correctly?
>>>>>
>>>>>
>>>>> For reference here's my final CMakeLists.txt file:
>>>>>
>>>>> cmake_minimum_required(VERSION 3.10)
>>>>>
>>>>> project(CBreakCompiler)
>>>>>
>>>>> set(CMAKE_CXX_STANDARD 17)
>>>>> set(CMAKE_CXX_STANDARD_REQUIRED True)
>>>>> add_compile_options(-Wall)
>>>>>
>>>>> find_package(LLVM 10.0.0 REQUIRED CONFIG)
>>>>>
>>>>> message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
>>>>> message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
>>>>>
>>>>> include_directories(${LLVM_INCLUDE_DIRS})
>>>>> add_definitions(${LLVM_DEFINITIONS})
>>>>>
>>>>> add_executable(CBreakCompiler
>>>>>     src/main.cpp
>>>>>     src/Parser.cpp
>>>>>     src/SourceTokenizer.cpp
>>>>>     src/IRCompiler.cpp
>>>>>     src/CompiledOutput.cpp)
>>>>>
>>>>> llvm_map_components_to_libnames(llvm_libs all)
>>>>> target_link_libraries(CBreakCompiler ${llvm_libs})
>>>>>
>>>>>
>>>>> And a snippet from the cmake output corresponding to those message
>>>>> lines:
>>>>>
>>>>> -- Found LLVM 10.0.0
>>>>> -- Using LLVMConfig.cmake in: /usr/local/lib/cmake/llvm
>>>>>
>>>>>
>>>>> There are dozens of link errors.. the first few and last few are:
>>>>>
>>>>> CMakeFiles/CBreakCompiler.dir/src/main.cpp.o:(.data.rel+0x0):
>>>>> undefined reference to `llvm::DisableABIBreakingChecks'
>>>>> CMakeFiles/CBreakCompiler.dir/src/main.cpp.o: In function
>>>>> `std::default_delete<llvm::LLVMContext>::operator()(llvm::LLVMContext*)
>>>>> const':
>>>>> main.cpp:(.text._ZNKSt14default_deleteIN4llvm11LLVMContextEEclEPS1_[_ZNKSt14default_deleteIN4llvm11LLVMContextEEclEPS1_]+0x1e):
>>>>> undefined reference to `llvm::LLVMContext::~LLVMContext()'
>>>>> ...
>>>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0xe0):
>>>>> undefined reference to `llvm::raw_ostream::anchor()'
>>>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0xf8):
>>>>> undefined reference to `typeinfo for llvm::raw_pwrite_stream'
>>>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0x110):
>>>>> undefined reference to `typeinfo for llvm::raw_ostream'
>>>>>
>>>>>
>>>> Seems like `llvm_map_components_to_libnames` wasn't populated well?
>>>> I'd start by printing `${llvm_libs}` in your CMake to check the output
>>>> of llvm_map_components_to_libnames, I don't know how the "all" works for
>>>> external builds? You may have to list the components you need more
>>>> explicitly instead?
>>>>
>>>> --
>>>> Mehdi
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>
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