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using ChocolArm64.Instruction;
using ChocolArm64.Memory;
using System;
using System.Collections.Generic;
using System.Reflection.Emit;
namespace ChocolArm64.Decoder
{
static class ADecoder
{
public static (ABlock[] Graph, ABlock Root) DecodeSubroutine(ATranslator Translator, long Start)
{
Dictionary<long, ABlock> Visited = new Dictionary<long, ABlock>();
Dictionary<long, ABlock> VisitedEnd = new Dictionary<long, ABlock>();
Queue<ABlock> Blocks = new Queue<ABlock>();
ABlock Enqueue(long Position)
{
if (!Visited.TryGetValue(Position, out ABlock Output))
{
Output = new ABlock(Position);
Blocks.Enqueue(Output);
Visited.Add(Position, Output);
}
return Output;
}
ABlock Root = Enqueue(Start);
while (Blocks.Count > 0)
{
ABlock Current = Blocks.Dequeue();
FillBlock(Translator.Thread.Memory, Current);
//Set child blocks. "Branch" is the block the branch instruction
//points to (when taken), "Next" is the block at the next address,
//executed when the branch is not taken. For Unconditional Branches
//(except BL/BLR that are sub calls) or end of executable, Next is null.
if (Current.OpCodes.Count > 0)
{
bool HasCachedSub = false;
AOpCode LastOp = Current.GetLastOp();
if (LastOp is AOpCodeBImm Op)
{
if (Op.Emitter == AInstEmit.Bl)
{
HasCachedSub = Translator.HasCachedSub(Op.Imm);
}
else
{
Current.Branch = Enqueue(Op.Imm);
}
}
if ((!(LastOp is AOpCodeBImmAl) &&
!(LastOp is AOpCodeBReg)) || HasCachedSub)
{
Current.Next = Enqueue(Current.EndPosition);
}
}
//If we have on the tree two blocks with the same end position,
//then we need to split the bigger block and have two small blocks,
//the end position of the bigger "Current" block should then be == to
//the position of the "Smaller" block.
while (VisitedEnd.TryGetValue(Current.EndPosition, out ABlock Smaller))
{
if (Current.Position > Smaller.Position)
{
ABlock Temp = Smaller;
Smaller = Current;
Current = Temp;
}
Current.EndPosition = Smaller.Position;
Current.Next = Smaller;
Current.Branch = null;
Current.OpCodes.RemoveRange(
Current.OpCodes.Count - Smaller.OpCodes.Count,
Smaller.OpCodes.Count);
VisitedEnd[Smaller.EndPosition] = Smaller;
}
VisitedEnd.Add(Current.EndPosition, Current);
}
//Make and sort Graph blocks array by position.
ABlock[] Graph = new ABlock[Visited.Count];
while (Visited.Count > 0)
{
ulong FirstPos = ulong.MaxValue;
foreach (ABlock Block in Visited.Values)
{
if (FirstPos > (ulong)Block.Position)
FirstPos = (ulong)Block.Position;
}
ABlock Current = Visited[(long)FirstPos];
do
{
Graph[Graph.Length - Visited.Count] = Current;
Visited.Remove(Current.Position);
Current = Current.Next;
}
while (Current != null);
}
return (Graph, Root);
}
private static void FillBlock(AMemory Memory, ABlock Block)
{
long Position = Block.Position;
AOpCode OpCode;
do
{
OpCode = DecodeOpCode(Memory, Position);
Block.OpCodes.Add(OpCode);
Position += 4;
}
while (!(IsBranch(OpCode) || IsException(OpCode)));
Block.EndPosition = Position;
}
private static bool IsBranch(AOpCode OpCode)
{
return OpCode is AOpCodeBImm ||
OpCode is AOpCodeBReg;
}
private static bool IsException(AOpCode OpCode)
{
return OpCode.Emitter == AInstEmit.Brk ||
OpCode.Emitter == AInstEmit.Svc ||
OpCode.Emitter == AInstEmit.Und;
}
public static AOpCode DecodeOpCode(AMemory Memory, long Position)
{
int OpCode = Memory.ReadInt32(Position);
AInst Inst = AOpCodeTable.GetInst(OpCode);
AOpCode DecodedOpCode = new AOpCode(AInst.Undefined, Position, OpCode);
if (Inst.Type != null)
{
DecodedOpCode = CreateOpCode(Inst.Type, Inst, Position, OpCode);
}
return DecodedOpCode;
}
private delegate object OpActivator(AInst Inst, long Position, int OpCode);
private static Dictionary<Type, OpActivator> Activators = new Dictionary<Type, OpActivator>();
private static AOpCode CreateOpCode(Type Type, AInst Inst, long Position, int OpCode)
{
if (Type == null)
{
throw new ArgumentNullException(nameof(Type));
}
if (!Activators.TryGetValue(Type, out OpActivator CreateInstance))
{
Type[] ArgTypes = new Type[] { typeof(AInst), typeof(long), typeof(int) };
DynamicMethod Mthd = new DynamicMethod($"{Type.Name}_Create", Type, ArgTypes);
ILGenerator Generator = Mthd.GetILGenerator();
Generator.Emit(OpCodes.Ldarg_0);
Generator.Emit(OpCodes.Ldarg_1);
Generator.Emit(OpCodes.Ldarg_2);
Generator.Emit(OpCodes.Newobj, Type.GetConstructor(ArgTypes));
Generator.Emit(OpCodes.Ret);
CreateInstance = (OpActivator)Mthd.CreateDelegate(typeof(OpActivator));
Activators.Add(Type, CreateInstance);
}
return (AOpCode)CreateInstance(Inst, Position, OpCode);
}
}
}
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