private readonly Format16OpCode inverseOpCode; //should we wish to invert this operator, because (a<b)==!(a>=b), therefore BGE
private CompareOp(IntExpression lhs, IntExpression rhs, Format16OpCode branchOpCode, Format16OpCode inverseOpCode)
{
this.lhs = lhs;
this.rhs = rhs;
this.branchOpCode = branchOpCode;
this.inverseOpCode = inverseOpCode;
}
private CompareOp(IntExpression lhs, IntExpression rhs, Format16OpCode branchOpCode, Format16OpCode inverseOpCode)
{
this.lhs=lhs;
this.rhs=rhs;
this.branchOpCode=branchOpCode;
this.inverseOpCode=inverseOpCode;
}
public void Emit(Format16OpCode opCode, int target)
{
var offset = target - (CurrentAddress + 4);
CheckRange(offset, -(1 << 8) + 1, (1 << 8) - 1, 1);
var fluentComment = opCode.ToHumanReadable() + " " + ((short)target).ToHex();
var offsetBits = (offset >> 1) & 0xff;
EmitHelper(null, 16, fluentComment, 13, 4, (int)opCode, 4, offsetBits, 8);
}
// branchOpCode: the normal case: (a<b) therefore BLT
// flipOpCode: the flipped case: (a<b)==(b>a), therefore BGT
// inverseOpCode: the inverse case: (a<b)==!(a>=b), therefore BGE
// flipInverseOpCode: the flipped inverse case: (a<b)==!(b<=a), therefore BLE
private static CompareOp CreateHelper(IntExpression lhs, IntExpression rhs,
Format16OpCode branchOpCode, Format16OpCode flipOpCode, Format16OpCode inverseOpCode, Format16OpCode flipInverseOpCode)
{
if (lhs.IsConstant())
{
if (rhs.IsConstant())
{
throw new Exception("ridiculous");
}
//flip the constant over to the right side, for better code generation
return(new CompareOp(rhs, lhs, flipOpCode, flipInverseOpCode));
}
return(new CompareOp(lhs, rhs, branchOpCode, inverseOpCode));
}
public void Emit(Format16OpCode opCode, int target)
{
var offset=target-(CurrentAddress+4);
CheckRange(offset, -(1<<8)+1, (1<<8)-1, 1);
var fluentComment=opCode.ToHumanReadable()+" "+((short)target).ToHex();
var offsetBits=(offset>>1)&0xff;
EmitHelper(null, 16, fluentComment, 13, 4, (int)opCode, 4, offsetBits, 8);
}
// branchOpCode: the normal case: (a<b) therefore BLT
// flipOpCode: the flipped case: (a<b)==(b>a), therefore BGT
// inverseOpCode: the inverse case: (a<b)==!(a>=b), therefore BGE
// flipInverseOpCode: the flipped inverse case: (a<b)==!(b<=a), therefore BLE
private static CompareOp CreateHelper(IntExpression lhs, IntExpression rhs,
Format16OpCode branchOpCode, Format16OpCode flipOpCode, Format16OpCode inverseOpCode, Format16OpCode flipInverseOpCode)
{
if(lhs.IsConstant()) {
if(rhs.IsConstant()) {
throw new Exception("ridiculous");
}
//flip the constant over to the right side, for better code generation
return new CompareOp(rhs, lhs, flipOpCode, flipInverseOpCode);
}
return new CompareOp(lhs, rhs, branchOpCode, inverseOpCode);
}
public static string ToHumanReadable(this Format16OpCode opCode)
{
return("BEQBNEBCSBCCBMIBPLBVSBVCBHIBLSBGEBLTBGTBLE".Substring((int)opCode * 3, 3));
}