private static Instruction /*?*/ PurgeNary <Instruction>(Instruction instruction, INamedEntity variable, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(variable != null);
Contract.Requires(canonicalizer != null);
Contract.Assume(instruction.Operand1 is Instruction);
var operand1 = Purge((Instruction)instruction.Operand1, variable, canonicalizer);
if (operand1 == null)
{
return(null);
}
var operand2andBeyond = instruction.Operand2 as Instruction[];
Contract.Assume(operand2andBeyond != null);
var n = operand2andBeyond.Length;
Instruction[] copy = null;
for (int i = 0; i < n; i++)
{
Contract.Assume(operand2andBeyond[i] != null);
var opi = Purge(operand2andBeyond[i], variable, canonicalizer);
if (opi == null)
{
return(null);
}
if (opi != operand2andBeyond[i])
{
if (copy == null)
{
copy = new Instruction[n];
for (int j = 0; j < i; j++)
{
copy[j] = operand2andBeyond[j];
}
}
Contract.Assume(copy.Length == n);
copy[i] = opi;
}
}
if (operand1 != instruction.Operand1 || copy != null)
{
return(canonicalizer.GetCanonicalExpression(instruction, operand1, null, copy));
}
return(instruction);
}
/// <summary>
/// Uses Arithmetic and Boolean laws to simplify expressions.
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="variable"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction /*?*/ PurgeBinary <Instruction>(Instruction instruction, INamedEntity variable, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(variable != null);
Contract.Requires(canonicalizer != null);
var operation = instruction.Operation;
Contract.Assume(instruction.Operand1 is Instruction);
var operand1 = (Instruction)instruction.Operand1;
Contract.Assume(instruction.Operand2 is Instruction);
var operand2 = (Instruction)instruction.Operand2;
operand1 = Purge(operand1, variable, canonicalizer);
operand2 = Purge(operand2, variable, canonicalizer);
switch (operation.OperationCode)
{
case OperationCode.And:
case OperationCode.Or:
if (operand1 == null)
{
return(operand2);
}
if (operand2 == null)
{
return(operand1);
}
if (operand1 != instruction.Operand1 || operand2 != instruction.Operand2)
{
return(canonicalizer.GetCanonicalExpression(instruction, operand1, operand2));
}
break;
}
if (operand1 != instruction.Operand1 || operand2 != instruction.Operand2)
{
return(null);
}
return(instruction);
}