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	// Subsequent blocks, if any. The number and order depend on the block kind.
	Succs []Edge

	// Inverse of successors.
	// The order is significant to Phi nodes in the block.
	// TODO: predecessors is a pain to maintain. Can we somehow order phi
	// arguments by block id and have this field computed explicitly when needed?
	Preds []Edge

	// A list of values that determine how the block is exited. The number

    AnalyzeRegion(region);
  }

  SideEffectAnalysisInfo(SideEffectAnalysisInfo&&) = default;

  // Returns a vector of ops that are direct control predecessors of `op`,
  // sorted in program order. If `filter` is provided, only predecessors that
  // pass the filter (returning true) will be included.
  const llvm::SmallVector<Operation*, 4>& DirectControlPredecessors(
      Operation* op) const;

  for (auto& entry : control_predecessors_) {
    auto op = entry.getFirst();
    auto& predecessors = entry.getSecond();
    auto& sorted_predecessors = sorted_control_predecessors_[op];
    for (Operation* predecessor : predecessors) {
      sorted_predecessors.push_back(predecessor);
      sorted_control_successors_[predecessor].push_back(op);
    }
  }
  control_predecessors_.clear();

                // Node must be at the predecessor state before calculating dependencies
                NodeAtState predecessor = new NodeAtState(getPath(), getTargetState().previous());
                dependencies.add(graph.nodeAtState(predecessor));
                // Transition any other nodes that depend on the predecessor state
                dependencies.add(new TransitionDependents(predecessor));
                seenPredecessor = true;

	}
}

// An integrator tracks a position in a utilization function and
// integrates it.
type integrator struct {
	u *mmuSeries
	// pos is the index in u.util of the current time's non-strict
	// predecessor.
	pos int
}

// advance returns the integral of the utilization function from 0 to
// time. advance must be called on monotonically increasing values of
// times.

				}
				if m.Op == ssa.OpPhi {
					break
				}
			}
			// Find the two predecessor blocks (write barrier on and write barrier off)
			if len(m.Args) != 2 {
				lv.f.Fatalf("phi before write barrier end mark has %d args, want 2", len(m.Args))
			}
			c := b.Preds[0].Block()
			d := b.Preds[1].Block()

			// Find their common predecessor block (the one that branches based on wb on/off).

			// cannot determine the real line number.
			if f.begin > expand {
				f.begin -= expand
			} else if f.begin > 1 {
				f.begin = 1
			}
		} else {
			// Find gap from predecessor and divide between predecessor and f.
			halfGap := (f.begin - funcs[i-1].end) / 2
			if halfGap > expand {
				halfGap = expand
			}
			funcs[i-1].end += halfGap
			f.begin -= halfGap
		}
		funcs[i] = f
	}

// Creates a pass that propagates TPU devices to users.
std::unique_ptr<OperationPass<func::FuncOp>> CreateTPUDevicePropagationPass();

// Create a pass that colocates each `Split` with its predecessor.
std::unique_ptr<OperationPass<func::FuncOp>> CreateTPUColocateSplitsPass();

// Creates a pass that replicates the tf._TPUCompileMlir op on each host that

	{name: "FMA", argLength: 3}, // compute (a*b)+c without intermediate rounding

	// Data movement. Max argument length for Phi is indefinite.
	{name: "Phi", argLength: -1, zeroWidth: true}, // select an argument based on which predecessor block we came from
	{name: "Copy", argLength: 1},                  // output = arg0
	// Convert converts between pointers and integers.
	// We have a special op for this so as to not confuse GC