llvm-project

839a8fec - AMDGPU: Copy SubtargetPredicate from pseudo to real for dpp16 and dpp8 (#84517)

AMDGPU: Copy SubtargetPredicate from pseudo to real for dpp16 and dpp8 (#84517) We usually expect to copy SubtargetPredicate (and OtherPredicates) from pseudo to real. However, in dpp16 and dpp8, there are assignments like SubtargetPredicate = HasDPP/HasDPP16/HasDpp8. These assignments override predicates copied from pseudo, and thus the predicates used to define pseudo get lost. Losing predicates is a subtle issue usually not easy to be found. It may result in instructions being generated on GPUs that do not support the features to generate them. https://github.com/llvm/llvm-project/pull/84354 addressed one of such issues, and inspired this work. Fortunately, we found that the assignment of SubtargetPredicate usually comes together with assignment of AssemblerPredicate, and with the same value. For example: let AssemblerPredicate = HasDPP16; let SubtargetPredicate = HasDPP16; One of them is redundant and can be removed. In this work, we remove the redundant assignment of SubtargetPredicate, and then copy it from pseudo for VOP*_DPP and VOP*_DPP8. With this change, we can safely use SubtargetPredicate to define pseudo instructions.