Handle InlineSig in MethodRewriter

[Miista]

Please refer to tonerdo/pose#30

This has low priority until we have investigated the impact on not being able to handle the instruction.

[Miista]

I'm changing this to medium priority since we are seeing the issue on .NET 6 as noted in #9

[Miista]

Resources:

• http://khyperia.blogspot.com/2013/01/creating-asgpupart-1.html

[Miista]

The following is a minimal working example:

var dateTimeShim = Shim.Replace(() => DateTime.Now).With(() => new DateTime(2004, 1, 1));
PoseContext.Isolate(
    () =>
    {
        Console.WriteLine(DateTime.UtcNow);
    }, dateTimeShim);

Invoking the above code results in System.NotSupportedException: InlineSig due to the opcode not being supported.

Adding support

It seems we can add support by:

1. Add a case in the switch in method MethodRewriter.Rewrite
2. Emit calli instruction

Update MethodRewriter.Rewrite

case OperandType.InlineSig:
    EmitILForInlineSig(ilGenerator, instruction);
    break;

Emit instruction

private void EmitILForInlineSig(ILGenerator ilGenerator, Instruction instruction)
{
    ilGenerator.EmitCalli(OpCodes.Calli, CallingConvention.StdCall, typeof(void), new Type[]{typeof(ulong)});
}

These two changes makes it so there's no longer an exception when running the code. In fact, the code now prints the expected result. Please see below.

05-06-2024 06:53:46

Concerns

I am not certain this covers all uses of InlineSig. I cannot know if the opcode will ever take on a different form which makes this translation incorrect.

For now, the assumption is that the InlineSig opcode always:

• Returns void
• Takes a pointer to an unsigned ulong