Linker error while building a new back end in the latest LLVM from GitHub

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1

Hello.
I am trying to build against the latest LLVM source from GitHub (from Jan 23 2021) my Connex processor back end, which is mostly inspired from the BPF and Mips back end.
I did my best to correct all the errors that appeared, but I now get a rather strange linker error that I don't know exactly how to solve (maybe somebody is more experienced than me on this). Maybe I have an error in lib/Target/Connex/CMakeLists.txt.

The error I get while building LLVM is:
   <<cd /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/build/lib/Target/Connex && /usr/bin/cmake \-E cmake\_link\_script CMakeFiles/LLVMConnexCodeGen\.dir/link\.txt \-\-verbose=1
   /usr/bin/c\+\+ \-fPIC  \-fPIC \-fvisibility\-inlines\-hidden \-Werror=date\-time \-Wall \-Wextra \-Wno\-unused\-parameter \-Wwrite\-strings \-Wcast\-qual \-Wno\-missing\-field\-initializers \-pedantic \-Wno\-long\-long \-Wimplicit\-fallthrough \-Wno\-maybe\-uninitialized \-Wno\-class\-memaccess \-Wno\-redundant\-move \-Wno\-noexcept\-type \-Wdelete\-non\-virtual\-dtor \-Wsuggest\-override \-Wno\-comment \-g   \-Wl,\-rpath\-link,/home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/build/\./lib   \-Wl,\-z,defs \-Wl,\-z,nodelete \-shared \-Wl,\-soname,libLLVMConnexCodeGen\.so\.12git \-o \.\./\.\./libLLVMConnexCodeGen\.so\.12git CMakeFiles/LLVMConnexCodeGen\.dir/ConnexAsmPrinter\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexFrameLowering\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexHazardRecognizer\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexInstrInfo\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexISelDAGToDAG\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexISelLowering\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexMCInstLower\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexRegisterInfo\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexSelectionDAGInfo\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexSubtarget\.cpp\.o CMakeFiles/LLVMConnexCodeGen\.dir/ConnexTargetMachine\.cpp\.o  \-Wl,\-rpath,"\\$ORIGIN/\.\./lib" \.\./\.\./libLLVMAsmPrinter\.so\.12git \.\./\.\./libLLVMConnexDesc\.so\.12git \.\./\.\./libLLVMConnexInfo\.so\.12git \.\./\.\./libLLVMSelectionDAG\.so\.12git \.\./\.\./libLLVMCodeGen\.so\.12git \.\./\.\./libLLVMTarget\.so\.12git \.\./\.\./libLLVMMC\.so\.12git \.\./\.\./libLLVMCore\.so\.12git \.\./\.\./libLLVMSupport\.so\.12git \-Wl,\-rpath\-link,/home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/build/lib
   /usr/bin/ld: CMakeFiles/LLVMConnexCodeGen\.dir/ConnexTargetMachine\.cpp\.o: in function \`llvm::TargetTransformInfo::Model<llvm::ConnexTTIImpl>::\~Model\(\)':
   /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/llvm/include/llvm/Analysis/TargetTransformInfo\.h:1672: undefined reference to \`llvm::TargetTransformInfo::Concept::\~Concept\(\)'
   /usr/bin/ld: CMakeFiles/LLVMConnexCodeGen\.dir/ConnexTargetMachine\.cpp\.o: in function \`llvm::TargetTransformInfoImplCRTPBase<llvm::ConnexTTIImpl>::getUserCost\(llvm::User const\*, llvm::ArrayRef<llvm::Value const\*>, llvm::TargetTransformInfo::TargetCostKind\)':
   /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/llvm/include/llvm/Analysis/TargetTransformInfoImpl\.h:911: undefined reference to \`llvm::IntrinsicCostAttributes::IntrinsicCostAttributes\(unsigned int, llvm::CallBase const&\)'
   /usr/bin/ld: /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/llvm/include/llvm/Analysis/TargetTransformInfoImpl\.h:953: undefined reference to \`llvm::TargetTransformInfo::getOperandInfo\(llvm::Value const\*, llvm::TargetTransformInfo::OperandValueProperties&\)'
   \.\.\.
   /usr/bin/ld: /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/llvm/include/llvm/CodeGen/BasicTTIImpl\.h:1805: undefined reference to \`llvm::IntrinsicCostAttributes::IntrinsicCostAttributes\(unsigned int, llvm::Type\*, llvm::ArrayRef<llvm::Type\*>\)'
   /usr/bin/ld: /home/asusu/LLVM/llvm2021\_01\_23/llvm\-project/llvm/include/llvm/CodeGen/BasicTTIImpl\.h:1826: undefined reference to \`llvm::IntrinsicCostAttributes::IntrinsicCostAttributes\(unsigned int, llvm::Type\*, llvm::ArrayRef<llvm::Type\*>, llvm::FastMathFlags\)'
   collect2: error: ld returned 1 exit status>>

 Please find if you have the time also most of the source files of my Connex LLVM back end in the ZIP archive at this address: https://sites.google.com/site/alexsusu/myfilecabinet/Connex_be.zip \(please note the file ERROR\_LINKER\.txt contains the above mentioned linker error\)\.

     Please let me know if you want me to provide any further information about my build.

Thank you very much,
Alex

2

Hello.
     I would like to come back to this message.
     It seems the reason of these linker errors are some changes performed in LLVM itself in the last 2 years, since I am able to run my back end in an older LLVM build downloaded from the source repository in Mar 2019. I apologize for being a bit in the haze - I didn't follow closely the changes performed to LLVM lately.

     If interested please find my main CMakeLists.txt for my Connex LLVM back end:
         add_llvm_component_group(Connex)

         set(LLVM_TARGET_DEFINITIONS Connex.td)

         tablegen(LLVM ConnexGenRegisterInfo.inc -gen-register-info)
         tablegen(LLVM ConnexGenInstrInfo.inc -gen-instr-info)
         tablegen(LLVM ConnexGenAsmWriter.inc -gen-asm-writer)
         tablegen(LLVM ConnexGenAsmMatcher.inc -gen-asm-matcher)
         tablegen(LLVM ConnexGenDAGISel.inc -gen-dag-isel)
         tablegen(LLVM ConnexGenMCCodeEmitter.inc -gen-emitter)
         tablegen(LLVM ConnexGenCallingConv.inc -gen-callingconv)
         tablegen(LLVM ConnexGenSubtargetInfo.inc -gen-subtarget)
         add_public_tablegen_target(ConnexCommonTableGen)

         add_llvm_target(ConnexCodeGen
           ConnexAsmPrinter.cpp
           ConnexFrameLowering.cpp
           ConnexHazardRecognizer.cpp
           # ConnexHazardRecognizerPreRAScheduler.cpp
           ConnexInstrInfo.cpp
           ConnexISelDAGToDAG.cpp
           ConnexISelLowering.cpp
           ConnexMCInstLower.cpp
           ConnexRegisterInfo.cpp
           ConnexSelectionDAGInfo.cpp
           ConnexSubtarget.cpp
           ConnexTargetMachine.cpp

           LINK_COMPONENTS
           #Analysis
           AsmPrinter
           CodeGen
           Core
           ConnexDesc
           ConnexInfo
           MC
           SelectionDAG
           Support
           Target
           #TransformUtils

           ADD_TO_COMPONENT
           Connex
           )

         #add_subdirectory(AsmParser) # 2021_01
         #add_subdirectory(InstPrinter)
         #add_subdirectory(Disassembler)
         add_subdirectory(MCTargetDesc)
         add_subdirectory(TargetInfo)

     Please keep in mind that the source files of my Connex LLVM back
  end are in a ZIP archive at this address:
  https://sites.google.com/site/alexsusu/myfilecabinet/Connex_be.zip .

   Thank you very much,
     Alex

3

Hello.
     I would like to inform that I managed to solve the problem mentioned here and to build LLVM today.
     What I had to do was to add (uncomment) in the lib/Target/Connex/CMakeLists.txt (my main back end CMakeLists file), in the section LINK_COMPONENTS the following 2 lines:
           Analysis
           TransformUtils

     I got inspired a bit from the XCore back end's main CMakeLists.txt since my back end's ConnexTargetTransformInfo.h is inspired from XCore.

     If ever, you can find the corrected CMakeLists.txt at https://sites.google.com/site/alexsusu/myfilecabinet/Connex_be.zip.

     However, I still have issues. While running llc I get the following error:
         ********** EXPANDING POST-RA PSEUDO INSTRS **********
         ********** Function: MatMul_BTransposed
         real copy: $r5 = COPY $r0
         Target didn't implement TargetInstrInfo::copyPhysReg!
         UNREACHABLE executed at /home/asusu/LLVM/llvm2021_01_23/llvm-project/llvm/include/llvm/CodeGen/TargetInstrInfo.h:951!
         ...
          #8 0x00007fce772ce4b6 llvm::TargetInstrInfo::isCopyInstrImpl(llvm::MachineInstr const&) const /home/asusu/LLVM/llvm2021_01_23/llvm-project/llvm/include/llvm/CodeGen/TargetInstrInfo.h:960:3
          #9 0x00007fce712082c8 (anonymous namespace)::ExpandPostRA::LowerCopy(llvm::MachineInstr*) /home/asusu/LLVM/llvm2021_01_23/llvm-project/llvm/lib/CodeGen/ExpandPostRAPseudos.cpp:166:19
         #10 0x00007fce71208611 (anonymous namespace)::ExpandPostRA::runOnMachineFunction(llvm::MachineFunction&) /home/asusu/LLVM/llvm2021_01_23/llvm-project/llvm/lib/CodeGen/ExpandPostRAPseudos.cpp:215:20
        ...
         #17 0x00005560165771f7 compileModule(char**, llvm::LLVMContext&) /home/asusu/LLVM/llvm2021_01_23/llvm-project/llvm/tools/llc/llc.cpp:661:66

     But actually I did implement TargetInstrInfo::copyPhysReg() in ConnexInstrInfo.cpp in my back end (you can see my back end code at https://sites.google.com/site/alexsusu/myfilecabinet/Connex_be.zip).

     Can somebody help me with this new llc runtime error that just appeared? (It looks like llc does not load the object file of ConnexInstrInfo.cpp, so it might be a hidden linker issue).

   Thank you very much,
     Alex

4

Hello.
     I solved this last runtime error. TargetInstrInfo::copyPhysReg() has changed the method prototype. Before it was:
   void copyPhysReg(MachineBasicBlock &MBB,
                    MachineBasicBlock::iterator I, const DebugLoc &DL,
                    unsigned DestReg, unsigned SrcReg,
                    bool KillSrc) const override;

     In the last version of LLVM from GitHub, they changed:
         unsigned DestReg, unsigned SrcReg
       to:
         MCRegister DestReg, MCRegister SrcReg .

     There was also the override keyword but I took it out without noticing the method prototype changed...
     After updating the method prototype everything now works.

   Best regards,
     Alex