public override CGExpr PEval(PEnv pEnv, bool hasDynamicControl)
{
// Partial evaluation may encounter a cached expression in conditionals
// etc, and should simply partially evaluate the expression inside the cache.
// No duplication of cached expression happens in the residual program because
// a cached expression appears only once in the regular code, and no occurrence
// from evaluation conditions is added to the residual program; see ComputeCell.PEval.
// New evaluation conditions are added later; see ProgramLines.CompileToDelegate.
return(expr.PEval(pEnv, hasDynamicControl));
}
// Returns residual ComputeCell or null if no cell needed
public ComputeCell PEval(PEnv pEnv)
{
CGExpr rCond = null;
if (evalCond != null) // Never the case for an output cell
{
rCond = evalCond.PEval(pEnv, false /* not dynamic control */);
}
if (rCond is CGNumberConst)
{
if ((rCond as CGNumberConst).number.value != 0.0)
{
rCond = null; // eval cond constant TRUE, discard eval cond
}
else
{
return(null); // eval cond constant FALSE, discard entire compute cell
}
}
// If residual eval cond is not TRUE then expr has dynamic control
CGExpr rExpr = expr.PEval(pEnv, rCond != null);
if (rExpr is CGConst && var != null)
{
// If cell's value is constant and it is not an output cell just put in PEnv
pEnv[cellAddr] = rExpr;
return(null);
}
else
{
// Else create fresh local variable for the residual cell, and make
// PEnv map cell address to that local variable:
Variable newVar = var != null?var.Fresh() : null;
pEnv[cellAddr] = new CGCellRef(cellAddr, newVar);
ComputeCell result = new ComputeCell(rExpr, newVar, cellAddr);
// result.EvalCond = rCond; // Don't save residual eval cond, we compute it accurately later...
return(result);
}
}
