[llvm] [SelectOpt] Refactor to prepare for support more select-like operations (PR #115745)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `sanitizer-x86_64-linux-android` running on `sanitizer-buildbot-android` while building `llvm` at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/4314

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

```
Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure)
...
[2228/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetIntrinsicInfo.cpp.o
[2229/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetMachine.cpp.o
[2230/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetLoweringObjectFile.cpp.o
[2231/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetMachineC.cpp.o
[2232/5317] Building AArch64GenInstrInfo.inc...
[2233/5317] Building AArch64GenSubtargetInfo.inc...
[2234/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64CallLowering.cpp.o
[2235/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64GlobalISelUtils.cpp.o
[2236/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64InstructionSelector.cpp.o
[2237/5317] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build0/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build64/lib/CodeGen -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build64/include -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -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 -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o -c /var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen/SelectOptimize.cpp
/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen/SelectOptimize.cpp:828:29: error: missing field 'Selects' initializer [-Werror,-Wmissing-field-initializers]
  828 |     SelectGroup SIGroup{Cond};
      |                             ^
1 error generated.
[2238/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64LegalizerInfo.cpp.o
[2239/5317] Building CXX object lib/MC/MCParser/CMakeFiles/LLVMMCParser.dir/AsmParser.cpp.o
[2240/5317] Building AMDGPUGenCallingConv.inc...
[2241/5317] Building AMDGPUGenDisassemblerTables.inc...
[2242/5317] Building AMDGPUGenMCPseudoLowering.inc...
[2243/5317] Building AMDGPUGenPostLegalizeGICombiner.inc...
[2244/5317] Building AMDGPUGenMCCodeEmitter.inc...
[2245/5317] Building AMDGPUGenAsmMatcher.inc...
[2246/5317] Building AMDGPUGenAsmWriter.inc...
[2247/5317] Building AMDGPUGenPreLegalizeGICombiner.inc...
[2248/5317] Building AMDGPUGenDAGISel.inc...
[2249/5317] Building AMDGPUGenGlobalISel.inc...
[2250/5317] Building AMDGPUGenInstrInfo.inc...
ninja: build stopped: subcommand failed.

How to reproduce locally: https://github.com/google/sanitizers/wiki/SanitizerBotReproduceBuild

@@@STEP_FAILURE@@@
Step 8 (bootstrap clang) failure: bootstrap clang (failure)
...
[2228/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetIntrinsicInfo.cpp.o
[2229/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetMachine.cpp.o
[2230/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetLoweringObjectFile.cpp.o
[2231/5317] Building CXX object lib/Target/CMakeFiles/LLVMTarget.dir/TargetMachineC.cpp.o
[2232/5317] Building AArch64GenInstrInfo.inc...
[2233/5317] Building AArch64GenSubtargetInfo.inc...
[2234/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64CallLowering.cpp.o
[2235/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64GlobalISelUtils.cpp.o
[2236/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64InstructionSelector.cpp.o
[2237/5317] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build0/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build64/lib/CodeGen -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm_build64/include -I/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror -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 -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SelectOptimize.cpp.o -c /var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen/SelectOptimize.cpp
/var/lib/buildbot/sanitizer-buildbot6/sanitizer-x86_64-linux-android/build/llvm-project/llvm/lib/CodeGen/SelectOptimize.cpp:828:29: error: missing field 'Selects' initializer [-Werror,-Wmissing-field-initializers]
  828 |     SelectGroup SIGroup{Cond};
      |                             ^
1 error generated.
[2238/5317] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64LegalizerInfo.cpp.o
[2239/5317] Building CXX object lib/MC/MCParser/CMakeFiles/LLVMMCParser.dir/AsmParser.cpp.o
[2240/5317] Building AMDGPUGenCallingConv.inc...
[2241/5317] Building AMDGPUGenDisassemblerTables.inc...
[2242/5317] Building AMDGPUGenMCPseudoLowering.inc...
[2243/5317] Building AMDGPUGenPostLegalizeGICombiner.inc...
[2244/5317] Building AMDGPUGenMCCodeEmitter.inc...
[2245/5317] Building AMDGPUGenAsmMatcher.inc...
[2246/5317] Building AMDGPUGenAsmWriter.inc...
[2247/5317] Building AMDGPUGenPreLegalizeGICombiner.inc...
[2248/5317] Building AMDGPUGenDAGISel.inc...
[2249/5317] Building AMDGPUGenGlobalISel.inc...
[2250/5317] Building AMDGPUGenInstrInfo.inc...
ninja: build stopped: subcommand failed.

How to reproduce locally: https://github.com/google/sanitizers/wiki/SanitizerBotReproduceBuild
program finished with exit code 2
elapsedTime=95.662853

```

</details>

https://github.com/llvm/llvm-project/pull/115745