[clang] [llvm] [HLSL] Adding Flatten and Branch if attributes (PR #116331)

[Henry Jiang via llvm-commits]

mustartt wrote:

Hi @joaosaffran I believe this patch is causing an build error in `clang-ppc64le-rhel` build bot. https://lab.llvm.org/buildbot/#/builders/145/builds/4252

```
FAILED: tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenFunction.cpp.o 
ccache /home/docker/llvm-external-buildbots/clang.17.0.6/bin/clang++ --gcc-toolchain=/gcc-toolchain/usr -DCLANG_EXPORTS -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/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/tools/clang/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang/lib/CodeGen -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/build/tools/clang/include -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 -fno-common -Woverloaded-virtual -Wno-nested-anon-types -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenFunction.cpp.o -MF tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenFunction.cpp.o.d -o tools/clang/lib/CodeGen/CMakeFiles/obj.clangCodeGen.dir/CodeGenFunction.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang/lib/CodeGen/CodeGenFunction.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-rhel-test/clang-ppc64le-rhel/llvm-project/clang/lib/CodeGen/CodeGenFunction.cpp:2089:11: error: enumeration value 'SpellingNotCalculated' not handled in switch [-Werror,-Wswitch]
 2089 |   switch (HLSLControlFlowAttr) {
      |           ^~~~~~~~~~~~~~~~~~~
1 error generated.
```

https://github.com/llvm/llvm-project/pull/116331