RyuKen/Ryujinx.HLE/HOS/Tamper/CodeEmitters/StartEndLoop.cs

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using Ryujinx.HLE.Exceptions;
using Ryujinx.HLE.HOS.Tamper.Operations;
namespace Ryujinx.HLE.HOS.Tamper.CodeEmitters
{
/// <summary>
/// Code type 3 allows for iterating in a loop a fixed number of times.
/// </summary>
class StartEndLoop
{
private const int StartOrEndIndex = 1;
private const int IterationRegisterIndex = 3;
private const int IterationsImmediateIndex = 8;
private const int IterationsImmediateSize = 8;
private const byte LoopBegin = 0;
private const byte LoopEnd = 1;
public static void Emit(byte[] instruction, CompilationContext context)
{
// 300R0000 VVVVVVVV
// R: Register to use as loop counter.
// V: Number of iterations to loop.
// 310R0000
byte mode = instruction[StartOrEndIndex];
byte iterationRegisterIndex = instruction[IterationRegisterIndex];
switch (mode)
{
case LoopBegin:
// Just start a new compilation block and parse the instruction itself at the end.
context.BlockStack.Push(new OperationBlock(instruction));
return;
case LoopEnd:
break;
default:
throw new TamperCompilationException($"Invalid loop {mode} in Atmosphere cheat");
}
// Use the loop begin instruction stored in the stack.
instruction = context.CurrentBlock.BaseInstruction;
CodeType codeType = InstructionHelper.GetCodeType(instruction);
if (codeType != CodeType.StartEndLoop)
{
throw new TamperCompilationException($"Loop end does not match code type {codeType} in Atmosphere cheat");
}
// Validate if the register in the beginning and end are the same.
byte oldIterationRegisterIndex = instruction[IterationRegisterIndex];
if (iterationRegisterIndex != oldIterationRegisterIndex)
{
throw new TamperCompilationException($"The register used for the loop changed from {oldIterationRegisterIndex} to {iterationRegisterIndex} in Atmosphere cheat");
}
Register iterationRegister = context.GetRegister(iterationRegisterIndex);
ulong immediate = InstructionHelper.GetImmediate(instruction, IterationsImmediateIndex, IterationsImmediateSize);
// Create a loop block with the current operations and nest it in the upper
// block of the stack.
ForBlock block = new ForBlock(immediate, iterationRegister, context.CurrentOperations);
context.BlockStack.Pop();
context.CurrentOperations.Add(block);
}
}
}