/// <summary>
/// Compiles the topologically sorted list of Expr to a list (program)
/// of ComputeCells, encapsulating CGExprs. Builds a map from cellAddr to
/// local variable ids, for compiling sheet-internal cellrefs to ldloc instructions.
/// </summary>
public void AddComputeCells(DependencyGraph dpGraph, IList <FullCellAddr> cellList)
{
Debug.Assert(dpGraph.outputCell == cellList[cellList.Count - 1]);
CGExpr outputExpr;
if (cellList.Count == 0 || cellList.Count == 1 && dpGraph.inputCellSet.Contains(cellList.Single()))
{
// The output cell is also an input cell; load it:
outputExpr = new CGCellRef(dpGraph.outputCell, addressToVariable[dpGraph.outputCell]);
}
else
{
// First process all non-output cells, and ignore all input cells:
foreach (FullCellAddr cellAddr in cellList)
{
if (cellAddr.Equals(dpGraph.outputCell))
{
continue;
}
HashSet <FullCellAddr> dependents = dpGraph.GetDependents(cellAddr);
int minUses = dependents.Count;
if (minUses == 1)
{
FullCellAddr fromFca = dependents.First();
minUses = Math.Max(minUses, GetCount(fromFca, cellAddr));
}
// Now if minUses==1 then there is at most one use of the cell at cellAddr,
// and no local variable is needed. Otherwise, allocate a local variable:
if (minUses > 1)
{
CGExpr newExpr = CGExpressionBuilder.BuildExpression(cellAddr, addressToVariable);
Variable var = new LocalVariable(cellAddr.ToString(), newExpr.Type());
AddComputeCell(cellAddr, new ComputeCell(newExpr, var, cellAddr));
}
}
// Then process the output cell:
outputExpr = CGExpressionBuilder.BuildExpression(dpGraph.outputCell, addressToVariable);
}
// Add the output cell expression last, without a variable to bind it to; hence the null,
// also indicating that (only) the output cell is in tail position:
AddComputeCell(dpGraph.outputCell, new ComputeCell(outputExpr, null, dpGraph.outputCell));
}
