public Function ParseFunction(Node funcNode)
{
// Left node is identifier, right node is funcNode
Expect(funcNode.Left, TokenType.Identifier);
Expect(funcNode.Right, TokenType.Block);
var func = new Function(funcNode, funcNode.Left.Value);
if (funcNode.Right.Right == null)
{
return(func);
}
// Create a data label for this functions lr store
var data = new Data(DataType.Return)
{
Name = "return" + Data.Count,
Type = DataType.Word,
Value = "0"
};
Data.Add(data);
var lrRegister = func.AddRegister(data);
func.StoreLr(data, lrRegister);
// Iterate through statements in this functions block
// Parse return separately
var statement = funcNode.Right.Right;
do
{
if (statement.Type == TokenType.Return)
{
func.AddReturn(ParseReturn(func, statement));
}
else
{
func.AddData(ParseStatement(func, statement));
}
statement = statement.Right;
} while (statement != null);
func.LoadLr(data, lrRegister);
return(func);
}
/// <summary>
/// Generate assembly code to load an identifier into a register.
/// </summary>
/// <param name="identifierNode">Node to generate for</param>
/// <param name="parent">Parent containing assembly code</param>
/// <param name="register">Register to load into</param>
private void LoadIdentifier(Node identifierNode, Function parent, int register)
{
Logger.Instance.Debug("LoadIdentifier() {0}", identifierNode.ToString());
var locData = GetDataWithName(parent, identifierNode.Value);
// If this is an identifier we just load it into the right register
var data = locData as Statement;
if (data != null && data.Type != DataType.Function)
{
var s = data;
if (register != s.Register) // Don't load it in if it is already in the right register
{
parent.Lines.Add(string.Format("\tmov r{0}, r{1}\n", register, s.Register));
}
return;
}
// Otherwise, take a different action dpeending on data type
switch (locData.Type)
{
case DataType.Global: // if global, find the global and assemble from this parent
var global = (Global)locData;
parent.AssembleData(global.Datas, false, false);
break;
case DataType.Number:
parent.Lines.Add(string.Format("\tmov r{0}, #{1}\n", register, locData.Value));
break;
case DataType.Asciz:
parent.Lines.Add(string.Format("\tldr r{0}, addr_{1}\n", register, locData.Name));
break;
case DataType.Function:
// Check if anything is already in r0 (function return)
int?backupReg = null;
var backupData = parent.Registers.ElementAtOrDefault(0);
if (backupData != null)
{
// Move into an unused register
backupReg = parent.AddRegister(backupData) + 1;
parent.Lines.Add(string.Format("\tmov r{0}, r0\n", backupReg));
}
// Call function
parent.Lines.Add(string.Format("\tbl {0}\n", locData.Value));
// Result of function is in r0
// Move that into the required register
if (register != 0)
{
parent.Lines.Add(string.Format("\tmov r{0}, r0\n", register));
}
// If data was backed up restore it
if (backupReg != null)
{
parent.Lines.Add(string.Format("\tmov r0, r{0}\n", backupReg));
}
break;
case DataType.Operator:
// Data is in a register in parent, find it and load it
var regData = parent.Registers.FirstOrDefault(r => r.Name == locData.Name);
if (regData == null)
{
throw new Exception("Missing variable");
}
// Useless moving data into a register its already in
var existingRegister = ((Statement)regData).Register;
if (existingRegister != register)
{
parent.Lines.Add(string.Format("\tmov r{0}, r{1}\n", register, existingRegister));
}
break;
default:
throw new NotImplementedException("Cannot load this data type as an identifier");
}
}