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

[Steven Perron via cfe-commits]

================

----------------
s-perron wrote:

Is there a difference between this test and `llvm/test/CodeGen/SPIRV/HLSLControlFlowHint.ll`? If not, you probably only need one.

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