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>
///
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="variable"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction /*?*/ PurgeUnary <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;
var operand = Purge(operand1, variable, canonicalizer);
if (operand != operand1)
{
return(null);
}
return(instruction);
}
/// <summary>
/// Rewrites Boolean expressions to exclude references to variables that have been updated.
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="variable"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction /*?*/ Purge <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 operand1 = instruction.Operand1 as Instruction;
if (operand1 == null)
{
return(PurgeNullary(instruction, variable));
}
var operand2 = instruction.Operand2 as Instruction;
if (operand2 != null)
{
return(PurgeBinary(instruction, variable, canonicalizer));
}
else if (instruction.Operand2 == null)
{
return(PurgeUnary(instruction, variable, canonicalizer));
}
else
{
return(PurgeNary(instruction, variable, canonicalizer));
}
}
/// <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);
}
/// <summary>
///
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="mappings"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction SimplifyUnary <Instruction>(Instruction instruction, ValueMappings <Instruction> mappings, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(mappings != null);
Contract.Requires(canonicalizer != null);
Contract.Ensures(Contract.Result <Instruction>() != null);
var operation = instruction.Operation;
Contract.Assume(instruction.Operand1 is Instruction);
var operand1 = (Instruction)instruction.Operand1;
var operand = Simplify(operand1, mappings, canonicalizer);
var compileTimeConstant = mappings.GetCompileTimeConstantValueFor(operand);
if (compileTimeConstant != null)
{
var constantResult = Evaluator.Evaluate(instruction.Operation, compileTimeConstant);
if (constantResult != null)
{
return(canonicalizer.GetAsCanonicalizedLoadConstant(constantResult, instruction));
}
}
switch (operation.OperationCode)
{
case OperationCode.Neg:
if (operand.Operation.OperationCode == OperationCode.Neg)
{
Contract.Assume(operand.Operand1 is Instruction);
return((Instruction)operand.Operand1);
}
//TODO: if the operand is a binary operation with arithmetic operands where one of them is a Neg
//distribute the neg over the binary operation, if doing so is safe w.r.t. overflow.
break;
case OperationCode.Not:
var simplerInverse = TryToGetSimplerLogicalInverse(operand);
if (simplerInverse != null)
{
return(simplerInverse);
}
if (operand != operand1)
{
var operation1 = operand1.Operation;
switch (operation1.OperationCode)
{
case OperationCode.Bne_Un:
case OperationCode.Bne_Un_S:
case OperationCode.Beq:
case OperationCode.Beq_S:
OperationCode newOpcode = GetInverse(operation1.OperationCode, operand1.Type.TypeCode == PrimitiveTypeCode.Float32 || operand1.Type.TypeCode == PrimitiveTypeCode.Float64);
return(new Instruction()
{
Operation = new Operation()
{
OperationCode = newOpcode, Offset = operation.Offset, Location = operation.Location
},
Operand1 = operand1.Operand1,
Operand2 = operand1.Operand2
});
}
}
return(new Instruction()
{
Operation = operation, Operand1 = operand
});
}
return(instruction);
}
private static Instruction SimplifyNary <Instruction>(Instruction instruction, ValueMappings <Instruction> mappings, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(mappings != null);
Contract.Requires(canonicalizer != null);
Contract.Ensures(Contract.Result <Instruction>() != null);
Contract.Assume(instruction.Operand1 is Instruction);
instruction.Operand1 = Simplify((Instruction)instruction.Operand1, mappings, canonicalizer);
var operand2 = instruction.Operand2 as Instruction;
if (operand2 != null)
{
instruction.Operand2 = Simplify(operand2, mappings, canonicalizer);
}
else
{
var operand2andBeyond = instruction.Operand2 as Instruction[];
Contract.Assume(operand2andBeyond != null);
for (int i = 0, n = operand2andBeyond.Length; i < n; i++)
{
Contract.Assume(operand2andBeyond[i] != null);
operand2andBeyond[i] = Simplify(operand2andBeyond[i], mappings, canonicalizer);
}
}
return(instruction);
}
/// <summary>
/// Uses Arithmetic and Boolean laws to simplify expressions.
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="mappings"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction Simplify <Instruction>(Instruction instruction, ValueMappings <Instruction> mappings, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(mappings != null);
Contract.Requires(canonicalizer != null);
Contract.Ensures(Contract.Result <Instruction>() != null);
var operand1 = instruction.Operand1 as Instruction;
if (operand1 == null)
{
return(SimplifyNullary(instruction, mappings));
}
var operand2 = instruction.Operand2 as Instruction;
if (operand2 != null)
{
return(SimplifyBinary(instruction, mappings, canonicalizer));
}
else if (instruction.Operand2 == null)
{
return(SimplifyUnary(instruction, mappings, canonicalizer));
}
else
{
return(SimplifyNary(instruction, mappings, canonicalizer));
}
}
/// <summary>
/// Uses Arithmetic and Boolean laws to simplify expressions.
/// </summary>
/// <typeparam name="Instruction"></typeparam>
/// <param name="instruction"></param>
/// <param name="mappings"></param>
/// <param name="canonicalizer"></param>
/// <returns></returns>
internal static Instruction SimplifyBinary <Instruction>(Instruction instruction, ValueMappings <Instruction> mappings, ExpressionCanonicalizer <Instruction> canonicalizer)
where Instruction : Microsoft.Cci.Analysis.Instruction, new()
{
Contract.Requires(instruction != null);
Contract.Requires(mappings != null);
Contract.Requires(canonicalizer != null);
Contract.Ensures(Contract.Result <Instruction>() != 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;
IMetadataConstant constantResult = null;
var compileTimeConstant1 = mappings.GetCompileTimeConstantValueFor(operand1);
var compileTimeConstant2 = mappings.GetCompileTimeConstantValueFor(operand2);
if (compileTimeConstant1 != null)
{
if (compileTimeConstant2 != null)
{
constantResult = Evaluator.Evaluate(instruction.Operation, compileTimeConstant1, compileTimeConstant2);
}
else
{
constantResult = Evaluator.Evaluate(instruction.Operation, compileTimeConstant1, operand2, mappings);
}
}
else if (compileTimeConstant2 != null)
{
constantResult = Evaluator.Evaluate(instruction.Operation, operand1, compileTimeConstant2, mappings);
}
else
{
constantResult = Evaluator.Evaluate(instruction.Operation, operand1, operand2, mappings);
}
if (constantResult != null)
{
return(canonicalizer.GetAsCanonicalizedLoadConstant(constantResult, instruction));
}
//If we get here, the instruction does not simplify to a constant, but it could still simplify to a simpler expression.
bool operand1IsZero = compileTimeConstant1 != null && MetadataExpressionHelper.IsIntegralZero(compileTimeConstant1);
bool operand1IsOne = compileTimeConstant1 != null && (operand1IsZero ? false : MetadataExpressionHelper.IsIntegralOne(compileTimeConstant1));
bool operand1IsMinusOne = compileTimeConstant1 != null && ((operand1IsZero || operand1IsOne) ? false : MetadataExpressionHelper.IsIntegralMinusOne(compileTimeConstant1));
bool operand2IsZero = compileTimeConstant2 != null && MetadataExpressionHelper.IsIntegralZero(compileTimeConstant2);
bool operand2IsOne = compileTimeConstant2 != null && (operand1IsZero ? false : MetadataExpressionHelper.IsIntegralOne(compileTimeConstant2));
bool operand2IsMinusOne = compileTimeConstant2 != null && ((operand2IsZero || operand2IsOne) ? false : MetadataExpressionHelper.IsIntegralMinusOne(compileTimeConstant2));
operand1 = Simplify(operand1, mappings, canonicalizer);
operand2 = Simplify(operand2, mappings, canonicalizer);
switch (operation.OperationCode)
{
case OperationCode.Add:
case OperationCode.Add_Ovf:
case OperationCode.Add_Ovf_Un:
if (operand1IsZero)
{
return(operand2);
}
if (operand2IsZero)
{
return(operand1);
}
//TODO: factor out common mults/divs/etc (subject to overflow checks).
break;
case OperationCode.And:
if (operand1IsZero)
{
return(operand1);
}
if (operand2IsZero)
{
return(operand2);
}
if (operand1IsMinusOne)
{
return(operand2);
}
if (operand2IsMinusOne)
{
return(operand1);
}
if (operand1.Operation.OperationCode == OperationCode.Not && operand2.Operation.OperationCode == OperationCode.Not)
{
var opnd11 = operand1.Operand1 as Instruction;
var opnd21 = operand2.Operand1 as Instruction;
Contract.Assume(opnd11 != null && opnd21 != null);
var or = new Operation()
{
OperationCode = OperationCode.Or, Location = operation.Location, Offset = operation.Offset
};
var orInst = new Instruction()
{
Operation = or, Operand1 = opnd11, Operand2 = opnd21, Type = instruction.Type
};
var not = new Operation {
OperationCode = OperationCode.Not, Location = operation.Location, Offset = operation.Offset
};
return(new Instruction()
{
Operation = not, Operand1 = orInst, Type = instruction.Type
});
}
break;
case OperationCode.Ceq:
//If one of the operands is const 0 and the other is a boolean expression, invert the boolean expression
if (operand2IsZero && operand1.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
var not = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Not
};
instruction = new Instruction()
{
Operation = not, Operand1 = operand1, Type = instruction.Type
};
return(SimplifyUnary(instruction, mappings, canonicalizer));
}
else if (operand1IsZero && operand2.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
var not = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Not
};
instruction = new Instruction()
{
Operation = not, Operand1 = operand2, Type = instruction.Type
};
return(SimplifyUnary(instruction, mappings, canonicalizer));
}
else
{
operation = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Beq
};
}
break;
case OperationCode.Cgt:
operation = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Bgt
};
break;
case OperationCode.Cgt_Un:
operation = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Bgt_Un
};
break;
case OperationCode.Clt:
operation = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Blt
};
break;
case OperationCode.Clt_Un:
operation = new Operation()
{
Location = instruction.Operation.Location, Offset = instruction.Operation.Offset, OperationCode = OperationCode.Blt_Un
};
break;
case OperationCode.Div:
case OperationCode.Div_Un:
if (operand2IsOne)
{
return(operand1);
}
break;
case OperationCode.Mul:
case OperationCode.Mul_Ovf:
case OperationCode.Mul_Ovf_Un:
if (operand1IsOne)
{
return(operand2);
}
if (operand2IsOne)
{
return(operand1);
}
break;
case OperationCode.Or:
if (operand1IsZero)
{
return(operand2);
}
if (operand2IsZero)
{
return(operand1);
}
if (operand1.Operation.OperationCode == OperationCode.Not && operand2.Operation.OperationCode == OperationCode.Not)
{
var opnd11 = operand1.Operand1 as Instruction;
var opnd21 = operand2.Operand1 as Instruction;
Contract.Assume(opnd11 != null && opnd21 != null);
var and = new Operation()
{
OperationCode = OperationCode.And, Location = operation.Location, Offset = operation.Offset
};
var andInst = new Instruction()
{
Operation = and, Operand1 = opnd11, Operand2 = opnd21, Type = instruction.Type
};
var not = new Operation {
OperationCode = OperationCode.Not, Location = operation.Location, Offset = operation.Offset
};
return(new Instruction()
{
Operation = not, Operand1 = andInst, Type = instruction.Type
});
}
if (operand1.Operand1 == operand2.Operand1 && operand1.Operand2 == operand2.Operand2 &&
operand1.Operation.OperationCode != operand2.Operation.OperationCode && operand2.Operand1 != null &&
operand1.Operation.OperationCode == GetInverse(operand2.Operation.OperationCode,
operand2.Operand1.Type.TypeCode == PrimitiveTypeCode.Float32 || operand2.Operand1.Type.TypeCode == PrimitiveTypeCode.Float64))
{
return(canonicalizer.GetAsCanonicalizedLoadConstant(new MetadataConstant()
{
Value = true, Type = instruction.Type
}, instruction));
}
break;
case OperationCode.Rem:
case OperationCode.Rem_Un:
break;
case OperationCode.Shl:
case OperationCode.Shr:
case OperationCode.Shr_Un:
if (operand2IsZero)
{
return(operand1);
}
break;
case OperationCode.Sub:
case OperationCode.Sub_Ovf:
case OperationCode.Sub_Ovf_Un:
if (operand2IsZero)
{
return(operand1);
}
break;
case OperationCode.Xor:
break;
case OperationCode.Beq:
case OperationCode.Beq_S:
if (operand1IsZero && operand2.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
var operand2inv = TryToGetSimplerLogicalInverse(operand2);
if (operand2inv != null)
{
return(operand2inv);
}
}
else if (operand2IsZero && operand1.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
var operand1inv = TryToGetSimplerLogicalInverse(operand1);
if (operand1inv != null)
{
return(operand1inv);
}
}
goto case OperationCode.Bge_S;
case OperationCode.Bne_Un:
case OperationCode.Bne_Un_S:
if (operand1IsZero && operand2.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
return(operand2);
}
if (operand2IsZero && operand1.Type.TypeCode == PrimitiveTypeCode.Boolean)
{
return(operand1);
}
goto case OperationCode.Bge_S;
case OperationCode.Bge_S:
case OperationCode.Bge_Un_S:
case OperationCode.Bgt_S:
case OperationCode.Bgt_Un_S:
case OperationCode.Ble_S:
case OperationCode.Ble_Un_S:
case OperationCode.Blt_S:
case OperationCode.Blt_Un_S:
operation = new Operation()
{
Location = operation.Location, Offset = operation.Offset,
OperationCode = LongVersionOf(operation.OperationCode), Value = operation.Value
};
break;
}
if (operation != instruction.Operation || operand1 != instruction.Operand1 || operand2 != instruction.Operand2)
{
return new Instruction()
{
Operation = operation, Operand1 = operand1, Operand2 = operand2, Type = instruction.Type
}
}
;
return(instruction);
}