[clang] [llvm] [HLSL] Implement ddx and ddy HLSL intrinsics (PR #168887)

[Sarah Spall via llvm-commits]

https://github.com/spall commented:

Looking at your similar PR (https://github.com/llvm/llvm-project/pull/168874), do you also need to add SPIRV::OpDPdy and SPIRV::OpDPdx to https://github.com/llvm/llvm-project/pull/168874/files#diff-ba9921ea1bab49f211b472854e8609ffc38debd428641ebd1b68512314ab9b6dR2155

https://github.com/llvm/llvm-project/pull/168887