public override void WriteTo(FlashWriter output)
{
var marks = new Dictionary <ASInstruction, long>();
var sharedExits = new Dictionary <ASInstruction, List <ASInstruction> >();
var forwardCaseExits = new Dictionary <ASInstruction, Tuple <LookUpSwitchIns, int> >();
foreach (ASInstruction instruction in _instructions)
{
long previousPosition = output.Position;
marks.Add(instruction, previousPosition);
instruction.WriteTo(output);
List <ASInstruction> jumpers = null;
if (sharedExits.TryGetValue(instruction, out jumpers))
{
foreach (ASInstruction jumper in jumpers)
{
long position = marks[jumper];
var fixedOffset = (uint)(previousPosition - (position + 4));
((Jumper)jumper).Offset = fixedOffset;
Rewrite(output, jumper, position);
}
sharedExits.Remove(instruction);
}
Tuple <LookUpSwitchIns, int> switchIdentity = null;
if (forwardCaseExits.TryGetValue(instruction, out switchIdentity))
{
int caseIndex = switchIdentity.Item2;
LookUpSwitchIns lookUpSwitch = switchIdentity.Item1;
long position = marks[lookUpSwitch];
var fixedOffset = (uint)(previousPosition - position);
if (caseIndex == lookUpSwitch.CaseOffsets.Count)
{
lookUpSwitch.DefaultOffset = fixedOffset;
}
else
{
lookUpSwitch.CaseOffsets[caseIndex] = fixedOffset;
}
Rewrite(output, lookUpSwitch, position);
}
if (instruction.OP == OPCode.LookUpSwitch)
{
bool requiresRewrite = false;
var lookUpSwitch = (LookUpSwitchIns)instruction;
ASInstruction[] cases = SwitchExits[lookUpSwitch];
for (int i = 0; i < cases.Length; i++)
{
ASInstruction exit = cases[i];
if (exit.OP != OPCode.Label)
{
forwardCaseExits.Add(exit, Tuple.Create(lookUpSwitch, i));
}
else
{
requiresRewrite = true;
long exitPosition = marks[exit];
long jumpCount = (previousPosition - (exitPosition + 1));
uint fixedOffset = (uint)(uint.MaxValue - jumpCount);
if (i == (cases.Length - 1))
{
lookUpSwitch.DefaultOffset = fixedOffset;
}
else
{
lookUpSwitch.CaseOffsets[i] = fixedOffset;
}
}
}
if (requiresRewrite)
{
Rewrite(output, lookUpSwitch, previousPosition);
}
}
else if (Jumper.IsValid(instruction.OP))
{
var jumper = (Jumper)instruction;
if (jumper.Offset == 0)
{
continue;
}
ASInstruction exit = null;
if (!JumpExits.TryGetValue(jumper, out exit))
{
// An exit for this jump instruction could not be found, perhaps its' offset exceeds the index limit?
continue;
}
else if (exit.OP != OPCode.Label || !marks.ContainsKey(exit)) // Forward jumps can have a label for an exit, as long as it is located ahead.
{
jumpers = null;
if (!sharedExits.TryGetValue(exit, out jumpers))
{
jumpers = new List <ASInstruction>();
sharedExits.Add(exit, jumpers);
}
jumpers.Add(jumper);
}
else // Backward jumps must always have a label for an exit, and must be behind this instruction.
{
long exitPosition = marks[exit];
long jumpCount = (output.Position - (exitPosition + 1));
var fixedOffset = (uint)(uint.MaxValue - jumpCount);
jumper.Offset = fixedOffset;
Rewrite(output, jumper, previousPosition);
}
}
}
}
private int GetFinalJumpCount(ASMachine machine, Jumper jumper, List <ASInstruction> cleaned, Dictionary <int, List <ASInstruction> > localReferences, Stack <ASInstruction> valuePushers)
{
var magicCount = 0;
var locals = new List <Local>();
var pushers = new List <ASInstruction>();
bool?isJumping = jumper.RunCondition(machine);
// Get the instructions that pushed the values the jump instruction used.
int popCount = jumper.GetPopCount();
for (int i = 0; i < popCount; i++)
{
ASInstruction pusher = valuePushers.Pop();
if (!pushers.Contains(pusher))
{
pushers.Add(pusher);
// Get the instructions that were pushed by a GetLocal/N.
// These are used to determine whether the jump should be kept, since a local register could change within the jump body.
if (Local.IsValid(pusher.OP))
{
locals.Add((Local)pusher);
}
else if (Primitive.IsValid(pusher.OP) ||
pusher.OP == OPCode.Dup)
{
magicCount++;
}
}
}
// Output is not known, keep the instruction.
if (isJumping == null)
{
cleaned.Add(jumper);
return(0);
}
if (pushers.Count != (magicCount + locals.Count))
{
// One or more push instructions are wildcards, they have a 'history' of being modified.
// Keep this jump instruction, result could change.
cleaned.Add(jumper);
return(0);
}
// Gather information about the jump instruction, and it's 'block' of instructions that are being jumped over(if 'isJumping = true').
ASInstruction exit = null;
bool isBackwardsJump = false;
IEnumerable <ASInstruction> block = null;
if (!JumpExits.TryGetValue(jumper, out exit))
{
// This jump instruction should not be 'cleaned', keep it.
cleaned.Add(jumper);
return(0);
}
if (IsBackwardsJump(jumper))
{
isBackwardsJump = true;
block = cleaned
.Skip(cleaned.IndexOf(exit) + 1)
.TakeWhile(i => i != jumper);
}
else
{
block = (jumper.Offset > 0 ? GetJumpBlock(jumper) : null);
}
if (isJumping == true && block != null)
{
if (isBackwardsJump)
{
// Check if any of the locals used by the jump instruction is being set within the body.
// If the anwser is yes, removing the jump instruction is a bad idea, since the output of the condition could change.
foreach (Local local in locals)
{
foreach (ASInstruction instruction in block)
{
if (!Local.IsValid(instruction.OP))
{
continue;
}
if (Local.IsGetLocal(instruction.OP))
{
continue;
}
var bodyLocal = (Local)instruction;
if (bodyLocal.Register == local.Register)
{
// Do not remove the jump instruction, condition result may change.
cleaned.Add(jumper);
return(0);
}
}
}
}
foreach (KeyValuePair <Jumper, ASInstruction> jumpExit in JumpExits)
{
if (jumpExit.Key == jumper)
{
continue;
}
bool hasEntry = block.Contains(jumpExit.Key); // Does a jump instruction begin somewhere in the block?
bool hasExit = block.Contains(jumpExit.Value); // Does the jump instruction end somewhere in the block?
ASInstruction afterLast = _instructions[_indices[block.Last()] + 1];
bool isExitAfterLast = (jumpExit.Value == afterLast); // Does the exit of the jump that is in the block come after the final instruction of the current block?
if (hasEntry && !hasExit && !isExitAfterLast ||
hasExit && !hasEntry)
{
// Keep the jump instruction, since it will corrupt the other jump instruction that is using it.
cleaned.Add(jumper);
return(0);
}
}
foreach (KeyValuePair <LookUpSwitchIns, ASInstruction[]> switchExit in SwitchExits)
{
foreach (ASInstruction caseExit in switchExit.Value)
{
if (block.Contains(caseExit))
{
cleaned.Add(jumper);
return(0);
}
}
}
}
foreach (Local local in locals)
{
List <ASInstruction> references = localReferences[local.Register];
references.Remove(local);
}
// Remove the instructions that pushed values for the jump instruction that is to be removed.
foreach (ASInstruction pusher in pushers)
{
cleaned.Remove(pusher);
}
if (isJumping == false || isBackwardsJump)
{
block = null;
}
JumpExits.Remove(jumper);
return(block?.Count() ?? 0);
}