[llvm] [IR2Vec] Initial infrastructure for MIR2Vec (PR #161463)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-solaris11-sparcv9` running on `solaris11-sparcv9` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/13/builds/9929

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
...
[745/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/DroppedVariableStatsMIRTest.cpp.o
[746/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/LowLevelTypeTest.cpp.o
[747/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/CCStateTest.cpp.o
[748/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/DIETest.cpp.o
[749/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MachineInstrBundleIteratorTest.cpp.o
[750/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/GCMetadata.cpp.o
[751/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/AsmPrinterDwarfTest.cpp.o
[752/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MachineBasicBlockTest.cpp.o
[753/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/LexicalScopesTest.cpp.o
[754/1314] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MIR2VecTest.cpp.o
FAILED: unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MIR2VecTest.cpp.o 
/opt/llvm/21/bin/clang++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_FILE_OFFSET_BITS=64 -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_USE_CXX11_ABI=1 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/unittests/CodeGen -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/CodeGen -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/include -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/Solaris -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/third-party/unittest/googletest/include -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/third-party/unittest/googlemock/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections  -O -DNDEBUG  -Wno-variadic-macros -Wno-gnu-zero-variadic-macro-arguments -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -std=c++17 -MD -MT unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MIR2VecTest.cpp.o -MF unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MIR2VecTest.cpp.o.d -o unittests/CodeGen/CMakeFiles/CodeGenTests.dir/MIR2VecTest.cpp.o -c /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/CodeGen/MIR2VecTest.cpp
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/CodeGen/MIR2VecTest.cpp:58:5: error: use of undeclared identifier 'LLVMInitializeX86TargetInfo'; did you mean 'LLVMInitializeSparcTargetInfo'?
   58 |     LLVMInitializeX86TargetInfo();
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
      |     LLVMInitializeSparcTargetInfo
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeSparcTargetInfo' declared here
   26 | LLVM_TARGET(Sparc)
      | ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/TargetSelect.h:24:17: note: expanded from macro 'LLVM_TARGET'
   24 |   LLVM_ABI void LLVMInitialize##TargetName##TargetInfo();
      |                 ^
<scratch space>:66:1: note: expanded from here
   66 | LLVMInitializeSparcTargetInfo
      | ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/CodeGen/MIR2VecTest.cpp:59:5: error: use of undeclared identifier 'LLVMInitializeX86Target'; did you mean 'LLVMInitializeSparcTarget'?
   59 |     LLVMInitializeX86Target();
      |     ^~~~~~~~~~~~~~~~~~~~~~~
      |     LLVMInitializeSparcTarget
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeSparcTarget' declared here
   26 | LLVM_TARGET(Sparc)
      | ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/TargetSelect.h:28:17: note: expanded from macro 'LLVM_TARGET'
   28 |   LLVM_ABI void LLVMInitialize##TargetName##Target();
      |                 ^
<scratch space>:68:1: note: expanded from here
   68 | LLVMInitializeSparcTarget
      | ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/CodeGen/MIR2VecTest.cpp:60:5: error: use of undeclared identifier 'LLVMInitializeX86TargetMC'; did you mean 'LLVMInitializeSparcTargetMC'?
   60 |     LLVMInitializeX86TargetMC();
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~
      |     LLVMInitializeSparcTargetMC
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/stage1/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeSparcTargetMC' declared here
   26 | LLVM_TARGET(Sparc)
      | ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/TargetSelect.h:33:17: note: expanded from macro 'LLVM_TARGET'
   33 |   LLVM_ABI void LLVMInitialize##TargetName##TargetMC();
      |                 ^
<scratch space>:70:1: note: expanded from here

```

</details>

https://github.com/llvm/llvm-project/pull/161463