public static (bool wasChanged, IReadOnlyList <Instruction> instruction) CommonExprElimination(IReadOnlyList <Instruction> instructions)
{
var exprToResults = new StringToStrings();
var argToExprs = new StringToStrings();
var resultToExpr = new Dictionary <string, string>();
var wasChanged = false;
var newInstructions = new List <Instruction>(instructions.Count);
string uniqueExpr(Instruction instr) =>
string.Format(IsCommutative(instr) && string.Compare(instr.Argument1, instr.Argument2) > 0 ?
"{2}{1}{0}" : "{0}{1}{2}", instr.Argument1, instr.Operation, instr.Argument2);
void addLink(StringToStrings dict, string key, string value)
{
if (key != null)
{
if (dict.ContainsKey(key))
{
dict[key].Add(value);
}
else
{
dict[key] = new HashSet <string>()
{
value
};
}
}
}
for (var i = 0; i < instructions.Count; ++i)
{
if (instructions[i].Operation == "noop")
{
continue;
}
var expr = uniqueExpr(instructions[i]);
if (instructions[i].Operation != "assign" && exprToResults.TryGetValue(expr, out var results) && results.Count != 0)
{
wasChanged = true;
newInstructions.Add(new Instruction(instructions[i].Label, "assign", results.First(), "", instructions[i].Result));
}
else
{
newInstructions.Add(instructions[i].Copy());
addLink(argToExprs, instructions[i].Argument1, expr);
addLink(argToExprs, instructions[i].Argument2, expr);
}
if (resultToExpr.TryGetValue(instructions[i].Result, out var oldExpr))
{
if (exprToResults.ContainsKey(oldExpr))
{
exprToResults[oldExpr].Remove(instructions[i].Result);
}
}
resultToExpr[instructions[i].Result] = expr;
addLink(exprToResults, expr, instructions[i].Result);
if (argToExprs.ContainsKey(instructions[i].Result))
{
foreach (var delExpr in argToExprs[instructions[i].Result])
{
if (exprToResults.ContainsKey(delExpr))
{
foreach (var res in exprToResults[delExpr])
{
resultToExpr.Remove(res);
}
}
exprToResults.Remove(delExpr);
}
}
}
return(wasChanged, newInstructions);
}
static public Tuple <bool, List <Instruction> > CommonExprElimination(List <Instruction> instructions)
{
var exprToResults = new StringToStrings();
var argToExprs = new StringToStrings();
var resultToExpr = new Dictionary <string, string>();
var changed = false;
var newInstructions = new List <Instruction>(instructions.Count);
Func <Instruction, string> uniqueExpr = (Instruction instr) =>
string.Format(IsCommutative(instr) && string.Compare(instr.Argument1, instr.Argument2) > 0 ?
"{2}{1}{0}" : "{0}{1}{2}", instr.Argument1, instr.Operation, instr.Argument2);
Action <StringToStrings, string, string> addLink = (StringToStrings dict, string key, string value) =>
{
if (key != null)
{
if (dict.ContainsKey(key))
{
dict[key].Add(value);
}
else
{
dict[key] = new HashSet <string>()
{
value
}
};
}
};
for (int i = 0; i < instructions.Count; ++i)
{
var expr = uniqueExpr(instructions[i]);
if (instructions[i].Operation != "assign" && exprToResults.TryGetValue(expr, out HashSet <string> results) && results.Count != 0)
{
changed = true;
newInstructions.Add(new Instruction(instructions[i].Label, "assign", results.First(), "", instructions[i].Result));
}
else
{
newInstructions.Add(instructions[i].Copy());
addLink(argToExprs, instructions[i].Argument1, expr);
addLink(argToExprs, instructions[i].Argument2, expr);
}
if (resultToExpr.TryGetValue(instructions[i].Result, out string oldExpr))
{
if (exprToResults.ContainsKey(oldExpr))
{
exprToResults[oldExpr].Remove(instructions[i].Result);
}
}
resultToExpr[instructions[i].Result] = expr;
addLink(exprToResults, expr, instructions[i].Result);
if (argToExprs.ContainsKey(instructions[i].Result))
{
foreach (var delExpr in argToExprs[instructions[i].Result])
{
if (exprToResults.ContainsKey(delExpr))
{
foreach (var res in exprToResults[delExpr])
{
resultToExpr.Remove(res);
}
}
exprToResults.Remove(delExpr);
}
}
}
return(Tuple.Create(changed, newInstructions));
}
}
