public void Rewriter(ILProcessor processor)
{
var branches = processor.Instructions
.OfType <OperandInstruction <ILProcessorInstruction> >()
.Where(i => OpCodesMap.ContainsKey(i.OpCode))
.ToList();
if (!branches.Any())
{
return;
}
var offsets = new Dictionary <ILProcessorInstruction, int>();
var curOffset = 0;
foreach (var instruction in processor.Instructions)
{
offsets.Add(instruction, curOffset);
curOffset += GetInstructionSize(instruction);
}
while (branches.Any())
{
var branch = branches.FirstOrDefault(i =>
{
var deltaOffset = offsets[i.Operand] - offsets[i.Next];
return(deltaOffset >= sbyte.MinValue && deltaOffset <= sbyte.MaxValue);
});
if (branch == null)
{
break;
}
var shortFormOpCode = OpCodesMap[branch.OpCode];
var shortBranch = OperandInstruction.Create(shortFormOpCode, branch.Operand);
processor.Replace(branch, shortBranch);
//Update offsets
ILProcessorInstruction loop = shortBranch;
curOffset = offsets[branch];
while (loop != null)
{
offsets[loop] = curOffset;
curOffset += GetInstructionSize(loop);
loop = loop.Next;
}
offsets.Remove(branch);
branches.Remove(branch);
}
}
private static int GetInstructionSize(ILProcessorInstruction instruction)
{
var size = instruction.OpCode.Size;
switch (instruction.OpCode.OperandType)
{
case OperandType.InlineNone:
break;
case OperandType.ShortInlineBrTarget:
case OperandType.ShortInlineI:
case OperandType.ShortInlineVar:
size += 1;
break;
case OperandType.InlineVar:
size += 2;
break;
case OperandType.InlineBrTarget:
case OperandType.InlineI:
case OperandType.ShortInlineR:
case OperandType.InlineString:
case OperandType.InlineSig:
case OperandType.InlineMethod:
case OperandType.InlineField:
case OperandType.InlineType:
case OperandType.InlineTok:
size += 4;
break;
case OperandType.InlineI8:
case OperandType.InlineR:
size += 8;
break;
case OperandType.InlineSwitch:
size += 4 + 4 * ((OperandInstruction <IReadOnlyList <ILProcessorInstruction> >)instruction).Operand.Count;
break;
default:
throw new ArgumentOutOfRangeException();
}
return(size);
}
/// <summary>
/// Returns the overall effect of the given instruction on the stack.
/// Negative numbers means the stack shrinks, positive the stack grows
/// </summary>
/// <param name="instruction"></param>
/// <returns></returns>
private static int GetStackDelta(ILProcessorInstruction instruction)
{
var method = (instruction as OperandInstruction <MethodBase>)?.Operand;
var stackDelta = 0;
switch (instruction.OpCode.StackBehaviourPop)
{
case StackBehaviour.Pop0:
break;
case StackBehaviour.Pop1:
case StackBehaviour.Popi:
case StackBehaviour.Popref:
stackDelta -= 1;
break;
case StackBehaviour.Pop1_pop1:
case StackBehaviour.Popi_pop1:
case StackBehaviour.Popi_popi:
case StackBehaviour.Popi_popi8:
case StackBehaviour.Popi_popr4:
case StackBehaviour.Popi_popr8:
case StackBehaviour.Popref_pop1:
case StackBehaviour.Popref_popi:
stackDelta -= 2;
break;
case StackBehaviour.Popi_popi_popi:
case StackBehaviour.Popref_popi_pop1:
case StackBehaviour.Popref_popi_popi:
case StackBehaviour.Popref_popi_popi8:
case StackBehaviour.Popref_popi_popr4:
case StackBehaviour.Popref_popi_popr8:
case StackBehaviour.Popref_popi_popref:
stackDelta -= 3;
break;
case StackBehaviour.Varpop:
if (method?.IsStatic == false)
{
stackDelta -= 1;
}
stackDelta -= method?.GetParameters().Length ?? 0;
break;
default:
throw new ArgumentOutOfRangeException();
}
switch (instruction.OpCode.StackBehaviourPush)
{
case StackBehaviour.Push0:
break;
case StackBehaviour.Push1:
case StackBehaviour.Pushi:
case StackBehaviour.Pushi8:
case StackBehaviour.Pushr4:
case StackBehaviour.Pushr8:
case StackBehaviour.Pushref:
stackDelta += 1;
break;
case StackBehaviour.Push1_push1:
stackDelta += 2;
break;
case StackBehaviour.Varpush:
if ((method as MethodInfo)?.ReturnType != typeof(void))
{
stackDelta += 1;
}
break;
default:
throw new ArgumentOutOfRangeException();
}
return(stackDelta);
}
