[llvm] [CodeGen] Refactor rematerializer unit tests to reduce boilerplate (NFC) (PR #197575)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-5` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/43874

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
66.332 [1/10/6585] Linking CXX static library lib/libbenchmark_main.a
66.339 [1/9/6586] Copying llvm-locstats into /Users/buildbot/buildbot-root/aarch64-darwin/build/./bin
66.434 [1/8/6587] Linking CXX executable unittests/tools/llvm-profdata/LLVMProfdataTests
66.449 [1/7/6588] Linking CXX executable unittests/tools/llvm-profgen/LLVMProfgenTests
66.475 [1/6/6589] Linking CXX executable unittests/XRay/XRayTests
66.519 [1/5/6590] Linking CXX executable unittests/tools/llvm-mca/LLVMMCATests
66.585 [1/4/6591] Linking CXX executable unittests/Transforms/Utils/UtilsTests
66.641 [1/3/6592] Linking CXX executable unittests/Transforms/Scalar/ScalarTests
66.706 [1/2/6593] Linking CXX executable unittests/tools/llvm-exegesis/LLVMExegesisTests
67.319 [1/1/6594] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/RematerializerTest.cpp.o
FAILED: [code=1] unittests/CodeGen/CMakeFiles/CodeGenTests.dir/RematerializerTest.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /opt/homebrew/bin/ccache /usr/bin/clang++ -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/Users/buildbot/buildbot-root/aarch64-darwin/build/unittests/CodeGen -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/unittests/CodeGen -I/Users/buildbot/buildbot-root/aarch64-darwin/build/include -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/include -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/third-party/unittest/googletest/include -I/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/third-party/unittest/googlemock/include -isystem /opt/homebrew/include -fPIC -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 -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -Xclang -fno-pch-timestamp -O3 -DNDEBUG -std=c++17 -arch arm64 -UNDEBUG -Wno-variadic-macros -Wno-gnu-zero-variadic-macro-arguments -fno-exceptions -funwind-tables -fno-rtti -Wno-suggest-override -Winvalid-pch -Xclang -include-pch -Xclang /Users/buildbot/buildbot-root/aarch64-darwin/build/lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/cmake_pch.hxx.pch -Xclang -include -Xclang /Users/buildbot/buildbot-root/aarch64-darwin/build/lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/cmake_pch.hxx -MD -MT unittests/CodeGen/CMakeFiles/CodeGenTests.dir/RematerializerTest.cpp.o -MF unittests/CodeGen/CMakeFiles/CodeGenTests.dir/RematerializerTest.cpp.o.d -o unittests/CodeGen/CMakeFiles/CodeGenTests.dir/RematerializerTest.cpp.o -c /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/unittests/CodeGen/RematerializerTest.cpp
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/unittests/CodeGen/RematerializerTest.cpp:96:5: error: use of undeclared identifier 'LLVMInitializeAMDGPUTargetInfo'; did you mean 'LLVMInitializeAArch64TargetInfo'?
    LLVMInitializeAMDGPUTargetInfo();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    LLVMInitializeAArch64TargetInfo
/Users/buildbot/buildbot-root/aarch64-darwin/build/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeAArch64TargetInfo' declared here
LLVM_TARGET(AArch64)
^
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/include/llvm/Support/TargetSelect.h:24:17: note: expanded from macro 'LLVM_TARGET'
  LLVM_ABI void LLVMInitialize##TargetName##TargetInfo();
                ^
<scratch space>:74:1: note: expanded from here
LLVMInitializeAArch64TargetInfo
^
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/unittests/CodeGen/RematerializerTest.cpp:97:5: error: use of undeclared identifier 'LLVMInitializeAMDGPUTarget'; did you mean 'LLVMInitializeAArch64Target'?
    LLVMInitializeAMDGPUTarget();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~
    LLVMInitializeAArch64Target
/Users/buildbot/buildbot-root/aarch64-darwin/build/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeAArch64Target' declared here
LLVM_TARGET(AArch64)
^
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/include/llvm/Support/TargetSelect.h:28:17: note: expanded from macro 'LLVM_TARGET'
  LLVM_ABI void LLVMInitialize##TargetName##Target();
                ^
<scratch space>:76:1: note: expanded from here
LLVMInitializeAArch64Target
^
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/unittests/CodeGen/RematerializerTest.cpp:98:5: error: use of undeclared identifier 'LLVMInitializeAMDGPUTargetMC'; did you mean 'LLVMInitializeAArch64TargetMC'?
    LLVMInitializeAMDGPUTargetMC();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
    LLVMInitializeAArch64TargetMC
/Users/buildbot/buildbot-root/aarch64-darwin/build/include/llvm/Config/Targets.def:26:1: note: 'LLVMInitializeAArch64TargetMC' declared here
LLVM_TARGET(AArch64)
^
/Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/llvm/include/llvm/Support/TargetSelect.h:33:17: note: expanded from macro 'LLVM_TARGET'
  LLVM_ABI void LLVMInitialize##TargetName##TargetMC();
                ^
<scratch space>:78:1: note: expanded from here

```

</details>

https://github.com/llvm/llvm-project/pull/197575