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using ChocolArm64.Instructions;
using ChocolArm64.Memory;
using ChocolArm64.State;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Reflection.Emit;
namespace ChocolArm64.Decoders
{
static class Decoder
{
private delegate object OpActivator(Inst inst, long position, int opCode);
private static ConcurrentDictionary<Type, OpActivator> _opActivators;
static Decoder()
{
_opActivators = new ConcurrentDictionary<Type, OpActivator>();
}
public static Block DecodeBasicBlock(CpuThreadState state, MemoryManager memory, long start)
{
Block block = new Block(start);
FillBlock(state, memory, block);
return block;
}
public static (Block[] Graph, Block Root) DecodeSubroutine(
TranslatorCache cache,
CpuThreadState state,
MemoryManager memory,
long start)
{
Dictionary<long, Block> visited = new Dictionary<long, Block>();
Dictionary<long, Block> visitedEnd = new Dictionary<long, Block>();
Queue<Block> blocks = new Queue<Block>();
Block Enqueue(long position)
{
if (!visited.TryGetValue(position, out Block output))
{
output = new Block(position);
blocks.Enqueue(output);
visited.Add(position, output);
}
return output;
}
Block root = Enqueue(start);
while (blocks.Count > 0)
{
Block current = blocks.Dequeue();
FillBlock(state, 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;
OpCode64 lastOp = current.GetLastOp();
if (lastOp is OpCodeBImm64 op)
{
if (op.Emitter == InstEmit.Bl)
{
hasCachedSub = cache.HasSubroutine(op.Imm);
}
else
{
current.Branch = Enqueue(op.Imm);
}
}
if (!((lastOp is OpCodeBImmAl64) ||
(lastOp is OpCodeBReg64)) || hasCachedSub)
{
current.Next = Enqueue(current.EndPosition);
}
}
//If we have on the graph 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 Block smaller))
{
if (current.Position > smaller.Position)
{
Block 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.
Block[] graph = new Block[visited.Count];
while (visited.Count > 0)
{
ulong firstPos = ulong.MaxValue;
foreach (Block block in visited.Values)
{
if (firstPos > (ulong)block.Position)
firstPos = (ulong)block.Position;
}
Block 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(CpuThreadState state, MemoryManager memory, Block block)
{
long position = block.Position;
OpCode64 opCode;
do
{
//TODO: This needs to be changed to support both AArch32 and AArch64,
//once JIT support is introduced on AArch32 aswell.
opCode = DecodeOpCode(state, memory, position);
block.OpCodes.Add(opCode);
position += 4;
}
while (!(IsBranch(opCode) || IsException(opCode)));
block.EndPosition = position;
}
private static bool IsBranch(OpCode64 opCode)
{
return opCode is OpCodeBImm64 ||
opCode is OpCodeBReg64;
}
private static bool IsException(OpCode64 opCode)
{
return opCode.Emitter == InstEmit.Brk ||
opCode.Emitter == InstEmit.Svc ||
opCode.Emitter == InstEmit.Und;
}
public static OpCode64 DecodeOpCode(CpuThreadState state, MemoryManager memory, long position)
{
int opCode = memory.ReadInt32(position);
Inst inst;
if (state.ExecutionMode == ExecutionMode.AArch64)
{
inst = OpCodeTable.GetInstA64(opCode);
}
else
{
//TODO: Thumb support.
inst = OpCodeTable.GetInstA32(opCode);
}
OpCode64 decodedOpCode = new OpCode64(Inst.Undefined, position, opCode);
if (inst.Type != null)
{
decodedOpCode = MakeOpCode(inst.Type, inst, position, opCode);
}
return decodedOpCode;
}
private static OpCode64 MakeOpCode(Type type, Inst inst, long position, int opCode)
{
if (type == null)
{
throw new ArgumentNullException(nameof(type));
}
OpActivator createInstance = _opActivators.GetOrAdd(type, CacheOpActivator);
return (OpCode64)createInstance(inst, position, opCode);
}
private static OpActivator CacheOpActivator(Type type)
{
Type[] argTypes = new Type[] { typeof(Inst), typeof(long), typeof(int) };
DynamicMethod mthd = new DynamicMethod($"Make{type.Name}", 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);
return (OpActivator)mthd.CreateDelegate(typeof(OpActivator));
}
}
}
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