// It must be called when there are no other file system operations happening.
func sysWriteBits() fs.FileMode {
	// Read current umask. There's no way to read it without also setting it,
	// so set it conservatively and then restore the original one.
	m := syscall.Umask(0o777)
	syscall.Umask(m)    // restore bits
	if m&0o22 == 0o22 { // group and world are unwritable by default
		return 0o700
	}

			switch {
			case typVal.IsType():
				// Type conversion, which is safe.
			case typVal.IsBuiltin():
				// Builtin func, conservatively assumed to not
				// be safe for now.
				safe = false
				return false
			default:
				// A non-builtin func or method call.
				// Conservatively assume that all of them have
				// side effects for now.
				safe = false
				return false
			}
		case *ast.UnaryExpr:

// size of input tensors. The exception is that ops whose cost is irrelevant to
// input sizes, such as tf.Shape and tf.Reshape, are whitelisted to have cheap
// cost. This cost analysis is expected to be used conservatively (eg. use a low
// threshold to decide whether a cost is cheap or expensive), as it might not be
// accurate in some cases.
//
class CostAnalysis {
 public:
  explicit CostAnalysis(

// and 32 trailing zero bits, y should have less than 30 significant bits.
//
//	y < 1<<30  -> floor(x*4/Pi) < 1<<30 -> x < (1<<30 - 1) * Pi/4
//
// So, conservatively we can take x < 1<<29.
// Above this threshold Payne-Hanek range reduction must be used.
const reduceThreshold = 1 << 29

// trigReduce implements Payne-Hanek range reduction by Pi/4

    const llvm::SmallDenseSet<int64_t>& resource_ids,
    bool previous_unknown_resource_access) {
  // If we had any unknown resource access before, then we conservatively assume
  // that `resource` has been accessed before.
  // If `resource` is an unknown resource, then we conservatively assume that
  // the same resource has been accessed before.
  if (previous_unknown_resource_access ||
      resource_analysis_info.IsUnknownResource(resource))

		case *ast.Ident:
			if decl, ok := findDecl(arg).(*ast.CallExpr); ok {
				chanDecl = decl
			}
		case *ast.CallExpr:
			// Only signal.Notify(make(chan os.Signal), os.Interrupt) is safe,
			// conservatively treat others as not safe, see golang/go#45043
			if isBuiltinMake(pass.TypesInfo, arg) {
				return
			}
			chanDecl = arg
		}
		if chanDecl == nil || len(chanDecl.Args) != 1 {
			return
		}

			// registers for the asynchronously stopped
			// parent frame. Scan the parent
			// conservatively.
			state.conservative = true
		} else {
			// We only wanted to scan those two frames
			// conservatively. Clear the flag for future
			// frames.
			state.conservative = false
		}
		return
	}

	locals, args, objs := frame.getStackMap(false)

  // Converts from read/write state that relates ops with the same parallel id
  // to a set of last accesses for use with other parallel ids. Reads/writes
  // between parallel ids are conservatively approximated as writes.
  absl::flat_hash_set<Operation*> GetLastWrites(ResourceId resource_id);

  // Sets the read/write state for ops within the same parallel id.
  void SetLastWrites(ResourceId resource_id,

// RUN: tf-opt %s -tf-device-mark-input-output-aliases | FileCheck %s

// The following tests check if the aliasing pairs are conservatively marked
// correctly. In the following tests tf_device.cluster_func has inputs
// coming from ReadVariableOp and outputs written to a resource using
// AssignVariableOp. If a pair of input-output (say input at index `a` and
// output at index `b`) read and write to the same resource, then those
// input-output pairs alias each other.

      // only self-dependent conservatively, i.e., we do add dependencies
      // to/from unknown resource types. Currently, we don't have such cases and
      // there is no indication that we will need to support them in the future.
      LOG(WARNING) << "Self-dependent-only resource types are treated "
                      "conservatively for value-based side effects.";
    }