9d4094ae80
Add a new intrinsic, similar to llvm.amdgcn.set.inactive, but used only in functions with the `amdgpu_cs_chain` or `amdgpu_cs_chain_preserve` calling conventions. It allows setting the inactive lanes to those of a value received as a VGPR argument (whereas llvm.amdgcn.set.inactive usually takes a constant as the value of the inactive lanes). Differential Revision: https://reviews.llvm.org/D158604