/// <summary>
/// Parses an instruction and generates the binary code for it.
/// </summary>
/// <param name="address">The address of the instruction being parsed in the .text segment.</param>
/// <param name="args">An array containing the arguments of the instruction.</param>
/// <returns>One or more 32-bit integers representing this instruction. If this interface is implemented
/// for a pseudo-instruction, this may return more than one instruction value.</returns>
public override IEnumerable <int> GenerateCodeForInstruction(int address, string[] args)
{
// we expect three arguments. if not, throw an ArgumentException
if (args.Length != 3)
{
throw new ArgumentException("Invalid number of arguments provided. Expected 3, received " + args.Length + '.');
}
IEnumerable <int> returnVal = null;
int rdReg = RegisterMap.GetNumericRegisterValue(args[0]);
int rs1Reg = RegisterMap.GetNumericRegisterValue(args[1]);
int shiftAmt = 0;
bool isValidImmediate = IntExtensions.TryParseEx(args[2], out shiftAmt);
// ensure our shift amount is 5 bits or less.
isValidImmediate = isValidImmediate && ((shiftAmt & 0xFFFFFFE0) == 0);
var instructionList = new List <int>();
if (isValidImmediate)
{
int instruction = 0;
instruction |= (0x1 << 30);
instruction |= (shiftAmt << 20);
instruction |= (rs1Reg << 15);
instruction |= (0x5 << 12);
instruction |= (rdReg << 7);
instruction |= 0x13;
instructionList.Add(instruction);
returnVal = instructionList;
}
else
{
// otherwise, emit three instructions. load the upper 20 bits of the immediate into the destination register,
// bitwise-or it with the remaining 12 bits, and then shift the target register by the destination register.
var luiProc = new LuiProcessor();
instructionList.AddRange(luiProc.GenerateCodeForInstruction(address, new string[] { args[0], (shiftAmt >> 12).ToString() }));
int orImmVal = shiftAmt & 0xFFF;
var oriProc = new OriProcessor();
instructionList.AddRange(oriProc.GenerateCodeForInstruction(address, new string[] { args[0], orImmVal.ToString() }));
var sraProc = new SraProcessor();
instructionList.AddRange(sraProc.GenerateCodeForInstruction(address, new string[] { args[0], args[1], args[0] }));
}
return(returnVal);
}
/// <summary>
/// Parses an instruction and generates the binary code for it.
/// </summary>
/// <param name="address">The address of the instruction being parsed in the .text segment.</param>
/// <param name="args">An array containing the arguments of the instruction.</param>
/// <returns>One or more 32-bit integers representing this instruction. If this interface is implemented
/// for a pseudo-instruction, this may return more than one instruction value.</returns>
public override IEnumerable <int> GenerateCodeForInstruction(int address, string[] args)
{
// we expect three arguments. if not, throw an ArgumentException
if (args.Length != 3)
{
throw new ArgumentException("Invalid number of arguments provided. Expected 3, received " + args.Length + '.');
}
int rdReg = RegisterMap.GetNumericRegisterValue(args[0]);
int rs1Reg = RegisterMap.GetNumericRegisterValue(args[1]);
uint immVal = 0;
bool isValidImmediate = IntExtensions.TryParseEx(args[2], out immVal);
// this is okay, as we expect an unsigned value.
isValidImmediate = isValidImmediate && ((immVal & 0xFFFFF000) == 0);
var instructionList = new List <int>();
if (isValidImmediate)
{
int instruction = GenerateUnexpandedInstruction(immVal, rs1Reg, rdReg);
instructionList.Add(instruction);
}
else
{
// otherwise, emit three instructions. load the upper 20 bits of the immediate into the destination register,
// bitwise-or it with the remaining 12 bits, and then use sltu (the s-type).
var luiProc = new LuiProcessor();
instructionList.AddRange(luiProc.GenerateCodeForInstruction(address, new string[] { args[0], (immVal >> 12).ToString() }));
uint orImmVal = immVal & 0xFFF;
var oriProc = new OriProcessor();
instructionList.AddRange(oriProc.GenerateCodeForInstruction(address, new string[] { args[0], orImmVal.ToString() }));
var sltuProc = new SltuProcessor();
instructionList.AddRange(sltuProc.GenerateCodeForInstruction(address, new string[] { args[0], args[1], args[0] }));
}
return(instructionList);
}
/// <summary>
/// Generates a list of instructions for the ADDI instruction, given that the immediate argument
/// is larger than 11 bits (neglecting the sign bit).
/// </summary>
/// <param name="address">The next address in the .text segment.</param>
/// <param name="immediate"></param>
/// <param name="args"></param>
/// <returns></returns>
private List <int> GenerateExpandedInstruction(int address, int immediate, string[] args)
{
// load the upper 20 bits of the immediate into the destination register
int shiftedImm = immediate >> 12;
IEnumerable <int> backingLuiInstructions = new LuiProcessor().GenerateCodeForInstruction(address, new[] { args[0], shiftedImm.ToString() });
// or that with the lower 12 bits of that immediate.
IEnumerable <int> backingOriInstructions = new OriProcessor().GenerateCodeForInstruction(address, new[] { args[0], args[0], (immediate & 0xFFF).ToString() });
// add the value of what we have in our register with the rs1 register.
IEnumerable <int> backingAddInstructions = new AddProcessor().GenerateCodeForInstruction(address, new[] { args[0], args[0], args[1] });
var instructionList = new List <int>();
instructionList.AddRange(backingLuiInstructions);
instructionList.AddRange(backingOriInstructions);
instructionList.AddRange(backingAddInstructions);
return(instructionList);
}