private string GetRType(Command command, bool suppressRdWarning = false)
{
var instruction = OperationCodes.Instructions[command.Tokens[0]];
if (instruction.Instruction == "jr")
{
ValidateTokens(command.Tokens, 2);
var jumpReg = ParseRegisterIndex(command.Tokens[1]);
return String.Format("{0}{1}{2}",
instruction.OpCode,
DecToBinary(0, 3),
DecToBinary(jumpReg, 3),
DecToBinary(0, 6));
}
ValidateTokens(command.Tokens, 4);
var rd = ParseRegisterIndex(command.Tokens[1]);
WarnRd(rd, suppressRdWarning);
var rs = ParseRegisterIndex(command.Tokens[2]);
var rt = ParseRegisterIndex(command.Tokens[3]);
return String.Format("{0}{1}{2}{3}{4}",
instruction.OpCode,
DecToBinary(rd, 3),
DecToBinary(rs, 3),
DecToBinary(rt, 3),
instruction.ALUCode);
}
private string GetJType(Command command, List<Label> labels)
{
ValidateTokens(command.Tokens, 2);
var instruction = OperationCodes.Instructions[command.Tokens[0]];
var immediate = 0;
var isLabel = true;
try
{
immediate = ParseImmediate(command.Tokens[1]);
isLabel = false;
}
catch (Exception e) { } // Do nothing; we have the flag
if (isLabel)
{
var label = labels.FirstOrDefault(l => l.Name == command.Tokens[1]);
if (label == null)
{
throw new Exception(String.Format("Cannot find label {0}", command.Tokens[1]));
}
immediate = label.Index;
}
return String.Format("{0}{1}{2}",
instruction.OpCode,
DecToBinary(0, 6),
DecToBinary(immediate, 6));
}
private string GetNoOp(Command command)
{
// Use: Add $0 to $0 and store to $0 as our noop
var noopCommand = new Command
{
Index = command.Index,
Tokens = new string[] { "add", "$0", "$0", "$0" }
};
return GetRType(noopCommand, true);
}
private string GetIType(Command command, List<Label> labels)
{
var instruction = OperationCodes.Instructions[command.Tokens[0]];
var code = instruction.Instruction;
var rd = ParseRegisterIndex(command.Tokens[1]);
WarnRd(rd);
var rs = 0;
var immediate = 0;
if (code == "beq" || code == "bne")
{
// Format: beq $rd, $rs, label
ValidateTokens(command.Tokens, 4);
rs = ParseRegisterIndex(command.Tokens[2]);
var label = labels.FirstOrDefault(l => l.Name == command.Tokens[3]);
if (label == null)
{
throw new Exception("Cannot find label");
}
immediate = label.Index;
}
else if (code == "lw" || code == "sw")
{
// Format: lw $rd, offset($rs)
ValidateTokens(command.Tokens, 3);
var thirdVal = command.Tokens[2];
ValidateParenthesis(thirdVal);
var offsetAndRegister = thirdVal.Split(new char[] { '(', ')' }, StringSplitOptions.RemoveEmptyEntries);
immediate = ParseOffset(offsetAndRegister[0]);
rs = ParseRegisterIndex(offsetAndRegister[1]);
}
else
{
// Format: XXXX $rd, $rs, imm
ValidateTokens(command.Tokens, 4);
rs = ParseRegisterIndex(command.Tokens[2]);
immediate = ParseImmediate(command.Tokens[3]);
}
return String.Format("{0}{1}{2}{3}",
instruction.OpCode,
DecToBinary(rd, 3),
DecToBinary(rs, 3),
DecToBinary(immediate, 6));
}