public LHSAssign() {
Prev = null;
Exp = new ExpDesc();
}
// check whether, in an assignment to an upvalue/local variable, the
// upvalue/local variable is begin used in a previous assignment to a
// table. If so, save original upvalue/local value in a safe place and
// use this safe copy in the previous assignment.
private void CheckConflict( LHSAssign lh, ExpDesc v )
{
var fs = CurFunc;
// eventual position to save local variable
int extra = fs.FreeReg;
bool conflict = false;
// check all previous assignments
for( ; lh != null; lh = lh.Prev )
{
var e = lh.Exp;
// assign to a table?
if( e.Kind == ExpKind.VINDEXED )
{
// table is the upvalue/local being assigned now?
if( e.Ind.Vt == v.Kind && e.Ind.T == v.Info )
{
conflict = true;
e.Ind.Vt = ExpKind.VLOCAL;
e.Ind.T = extra; // previous assignment will use safe copy
}
// index is the local being assigned? (index cannot be upvalue)
if( v.Kind == ExpKind.VLOCAL && e.Ind.Idx == v.Info )
{
conflict = true;
e.Ind.Idx = extra; // previous assignment will use safe copy
}
}
}
if( conflict )
{
// copy upvalue/local value to a temporary (in position 'extra')
var op = (v.Kind == ExpKind.VLOCAL) ? OpCode.OP_MOVE : OpCode.OP_GETUPVAL;
Coder.CodeABC( fs, op, extra, v.Info, 0 );
Coder.ReserveRegs( fs, 1 );
}
}
// assignment -> ',' suffixedexp assignment
private void Assignment( LHSAssign lh, int nvars )
{
CheckCondition( ExpKindUtl.VKIsVar( lh.Exp.Kind ), "syntax error" );
ExpDesc e = new ExpDesc();
if( TestNext( (int)',' ) )
{
var nv = new LHSAssign();
nv.Prev = lh;
SuffixedExp( nv.Exp );
if( nv.Exp.Kind != ExpKind.VINDEXED )
CheckConflict( lh, nv.Exp );
CheckLimit( CurFunc, nvars + Lua.NumCSharpCalls,
LuaLimits.LUAI_MAXCCALLS, "C# levels" );
Assignment( nv, nvars+1 );
}
else
{
CheckNext( (int)'=' );
int nexps = ExpList( e );
if( nexps != nvars )
{
AdjustAssign( nvars, nexps, e );
if( nexps > nvars )
{
// remove extra values
CurFunc.FreeReg -= (nexps - nvars);
}
}
else
{
Coder.SetOneRet( CurFunc, e );
Coder.StoreVar( CurFunc, lh.Exp, e );
return;
}
}
// default assignment
InitExp( e, ExpKind.VNONRELOC, CurFunc.FreeReg-1 );
Coder.StoreVar( CurFunc, lh.Exp, e );
}
// stat -> func | assignment
private void ExprStat()
{
var v = new LHSAssign();
SuffixedExp( v.Exp );
// stat -> assignment ?
if( Lexer.Token.TokenType == (int)'=' ||
Lexer.Token.TokenType == (int)',' )
{
v.Prev = null;
Assignment( v, 1 );
}
// stat -> func
else
{
if( v.Exp.Kind != ExpKind.VCALL )
Lexer.SyntaxError("syntax error");
var pi = CurFunc.GetCode( v.Exp );
pi.Value = pi.Value.SETARG_C( 1 ); // call statment uses no results
}
}
