certain[b.ID] = blEXIT

			// Ret, it depends.
		case BlockRet, BlockRetJmp:
			local[b.ID] = blRET
			certain[b.ID] = blRET

			// Calls. TODO not all calls are equal, names give useful clues.
			// Any name-based heuristics are only relative to other calls,
			// and less influential than inferences from loop structure.
		case BlockDefer:
			local[b.ID] = blCALL