[llvm] [VPlan] Add VPIRInstruction, use for exit block live-outs. (PR #100735)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-rhel` running on `ppc64le-clang-rhel-test` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/145/builds/1845

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
10.777 [159/10/348] Creating library symlink lib/libclangTidyCERTModule.so
10.834 [157/11/349] Linking CXX shared library lib/libclangTidyPlugin.so.20.0git
10.834 [156/11/350] Linking CXX shared library lib/libclangTidyMain.so.20.0git
10.840 [155/11/351] Creating library symlink lib/libclangTidyPlugin.so
10.841 [155/10/352] Creating library symlink lib/libclangTidyMain.so
10.895 [154/10/353] Linking CXX executable bin/clang-tidy
10.976 [154/9/354] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlanSLP.cpp.o
11.963 [154/8/355] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlanHCFGBuilder.cpp.o
12.315 [154/7/356] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlanAnalysis.cpp.o
14.285 [154/6/357] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o
FAILED: lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o 
ccache /home/docker/llvm-external-buildbots/clang.17.0.6/bin/clang++ --gcc-toolchain=/gcc-toolchain/usr -DGTEST_HAS_RTTI=0 -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/lib/Transforms/Vectorize -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/lib/Transforms/Vectorize -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/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 -fPIC  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o -MF lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o.d -o lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:8729:15: error: variable 'ExitBB' set but not used [-Werror,-Wunused-but-set-variable]
 8729 |   BasicBlock *ExitBB = nullptr;
      |               ^
1 error generated.
16.806 [154/5/358] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlanRecipes.cpp.o
17.849 [154/4/359] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlanTransforms.cpp.o
18.514 [154/3/360] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/VPlan.cpp.o
23.377 [154/2/361] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/AsmPrinter.cpp.o
23.628 [154/1/362] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/100735