[clang] [llvm] [DXIL][SPIRV] Lower WaveActiveCountBits intrinsic (PR #113382)

[Greg Roth via cfe-commits]

https://github.com/pow2clk commented:

Looks good! The only change I think is essential is the missing `constrainAllUses`

https://github.com/llvm/llvm-project/pull/113382