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Off by 256 error in generated IL code for label.  #21799

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Off by 256 error in generated IL code for label. #21799
@manjaroman2

Description

@manjaroman2
manjaroman2
opened on Sep 9, 2024

The code:

public static OneParameter<ulong, Item> GenerateILGetRankIL()
{
    DynamicMethod dynamicMethod = new(
        "getRank",
        typeof(ulong),
        new[] { typeof(Item) }
    );

    ILGenerator il = dynamicMethod.GetILGenerator();
    Label[] labels = new Label[8];
    for (int i = 0; i < labels.Length; i++) labels[i] = il.DefineLabel();

    // ulong num = 0uL;
    il.Emit(OpCodes.Ldc_I4_0);
    il.Emit(OpCodes.Conv_I8);
    il.Emit(OpCodes.Stloc_0);
    // if (item == null)
    il.Emit(OpCodes.Ldarg_0);
    il.Emit(OpCodes.Brtrue_S, labels[0]);
    // return num;
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ret);
    // ulong num2 = 9223372036854775808uL;
    il.MarkLabel(labels[0]);
    il.Emit(OpCodes.Ldc_I8, -9223372036854775808);
    il.Emit(OpCodes.Stloc_1);
    // int num3 = 64;
    il.Emit(OpCodes.Ldc_I4_S, 64);
    il.Emit(OpCodes.Stloc_2);


    // if (item.IsUnique)
    il.Emit(OpCodes.Ldarg_0);
    il.EmitCall(OpCodes.Callvirt, Item__GetUnique, null);
    il.Emit(OpCodes.Brfalse_S, labels[1]);
    // num |= num2;
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Or);
    il.Emit(OpCodes.Stloc_0);
    // num2 >>= 1;
    il.MarkLabel(labels[1]);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_1);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Stloc_1);
    // num3--;
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Ldc_I4_1);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Stloc_2);


    // num |= num2 >> (int)(6 - item.Rarity);
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_6);
    il.Emit(OpCodes.Ldarg_0);
    il.EmitCall(OpCodes.Callvirt, Item__GetRarity, null);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Ldc_I4_S, 63);
    il.Emit(OpCodes.And);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Or);
    il.Emit(OpCodes.Stloc_0);
    // num2 >>= 6;
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_6);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Stloc_1);
    // num3 -= 6;
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Ldc_I4_6);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Stloc_2);


    // num |= num2 >> 5 - item.Tier.Id;
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_5);
    il.Emit(OpCodes.Ldarg_0);
    il.EmitCall(OpCodes.Callvirt, Item__GetTier, null);
    il.Emit(OpCodes.Stloc_3);
    il.Emit(OpCodes.Ldloca_S, 3);
    il.EmitCall(OpCodes.Callvirt, TierId__GetId, null);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Ldc_I4_S, 63);
    il.Emit(OpCodes.And);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Or);
    il.Emit(OpCodes.Stloc_0);
    // num2 >>= 5;
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_5);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Stloc_1);
    // num3 -= 5;
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Ldc_I4_5);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Stloc_2);


    // num |= num2 >> (int)item.Type;
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldarg_0);
    il.EmitCall(OpCodes.Callvirt, Item__GetType, null);
    il.Emit(OpCodes.Ldc_I4_S, 63);
    il.Emit(OpCodes.And);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Or);
    // num2 >>= 11;
    il.Emit(OpCodes.Stloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldc_I4_S, 11);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Stloc_1);
    // num3 -= 11;
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Ldc_I4_S, 11);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Stloc_2);
    // num3 -= 26;
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Ldc_I4_S, 26);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Stloc_2);


    // string subtypeCode = item.SubtypeCode;
    il.Emit(OpCodes.Ldarg_0);
    il.EmitCall(OpCodes.Callvirt, Item__GetSubtypeCode, null);
    il.Emit(OpCodes.Stloc_S, 4);
    // (no C# code)
    il.Emit(OpCodes.Ldc_I4_0);
    il.Emit(OpCodes.Stloc_S, 5);
    // 	foreach (int num4 in subtypeCode)
    // 	{
    // 		int num5 = num4;
    // 		if (num5 < 65)
    // 		{
    // 			continue;
    // 		}
    // 		if (num4 > 65 + num3)
    // 		{
    // 			if (num5 > 96 && num5 < 123)
    // 			{
    // 				num ^= num2 >> num4 - 97 + num3;
    // 			}
    // 		}
    // 		else
    // 		{
    // 			num ^= num2 >> num4 - 65;
    // 		}
    // 	}
    il.Emit(OpCodes.Br_S, labels[7]);
    MelonLogger.Msg($"MarkLabel 2 {il.ILOffset}"); 
    il.MarkLabel(labels[2]);
    MelonLogger.Msg($"MarkLabel 2 {il.ILOffset}"); 
    il.Emit(OpCodes.Ldloc_S, 4);
    il.Emit(OpCodes.Ldloc_S, 5);
    il.EmitCall(OpCodes.Callvirt,String__GetChars, null);
    il.Emit(OpCodes.Stloc_S, 6);
    // int num5 = num4;
    il.Emit(OpCodes.Ldloc_S, 6);
    il.Emit(OpCodes.Stloc_S, 7);
    // if (num5 < 65)
    il.Emit(OpCodes.Ldloc_S, 7);
    il.Emit(OpCodes.Ldc_I4_S, 65);
    il.Emit(OpCodes.Bge_S, labels[4]);
    // if (num5 > 96 && num5 < 123)
    il.Emit(OpCodes.Br_S, labels[6]);
    // loop start (head: IL_00b0)
    il.MarkLabel(labels[3]);
    il.Emit(OpCodes.Ldloc_S, 7);
    il.Emit(OpCodes.Ldc_I4_S, 96);
    il.Emit(OpCodes.Ble_S, labels[6]);
    il.Emit(OpCodes.Ldloc_S, 7);
    il.Emit(OpCodes.Ldc_I4_S, 123);
    MelonLogger.Msg($"Blt_S {il.ILOffset}"); 
    il.Emit(OpCodes.Blt_S, labels[5]);
    MelonLogger.Msg($"Blt_S {il.ILOffset}"); 
    
    // if (num4 > 65 + num3)
    il.Emit(OpCodes.Br_S, labels[6]);
    il.MarkLabel(labels[4]);
    il.Emit(OpCodes.Ldloc_S, 6);
    il.Emit(OpCodes.Ldc_I4_S, 65);
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Add);
    il.Emit(OpCodes.Bgt_S, labels[3]);
    // end loop
    // num ^= num2 >> num4 - 65;
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldloc_S, 6);
    il.Emit(OpCodes.Ldc_I4_S, 65);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Ldc_I4_S, 63);
    il.Emit(OpCodes.And);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Xor);
    il.Emit(OpCodes.Stloc_0);
    // num ^= num2 >> num4 - 97 + num3;
    il.Emit(OpCodes.Br_S, labels[6]);
    MelonLogger.Msg($"MarkLabel 5 {il.ILOffset}"); 
    il.MarkLabel(labels[5]);
    MelonLogger.Msg($"MarkLabel 5 {il.ILOffset}"); 
    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldloc_S, 6);
    il.Emit(OpCodes.Ldc_I4_S, 97);
    il.Emit(OpCodes.Sub);
    il.Emit(OpCodes.Ldloc_2);
    il.Emit(OpCodes.Add);
    il.Emit(OpCodes.Ldc_I4_S, 63);
    il.Emit(OpCodes.And);
    il.Emit(OpCodes.Shr_Un);
    il.Emit(OpCodes.Xor);
    il.Emit(OpCodes.Stloc_0);
    // (no C# code)
    il.MarkLabel(labels[6]);
    il.Emit(OpCodes.Ldloc_S, 5);
    il.Emit(OpCodes.Ldc_I4_1);
    il.Emit(OpCodes.Add);
    il.Emit(OpCodes.Stloc_S, 5);
    // return num;
    il.MarkLabel(labels[7]);
    il.Emit(OpCodes.Ldloc_S, 5);
    il.Emit(OpCodes.Ldloc_S, 4);
    il.EmitCall(OpCodes.Callvirt, String__GetLength, null);
    MelonLogger.Msg($"Blt_S {il.ILOffset}"); 
    il.Emit(OpCodes.Blt_S, labels[2]);
    MelonLogger.Msg($"Blt_S {il.ILOffset}"); 
    // end loop


    il.Emit(OpCodes.Ldloc_0);
    il.Emit(OpCodes.Ret);

    OneParameter<ulong, Item> del =
        (OneParameter<ulong, Item>)dynamicMethod.CreateDelegate(typeof(OneParameter<ulong, Item>));
    return del;
    // OneParameter<ulong, Item> getRankIL =
    //     (OneParameter<ulong, Item>)dynamicMethod.CreateDelegate(typeof(OneParameter<ulong, Item>));
    // return del;
}

The console log:

[14:05:20.761] [MoreQOD] MarkLabel 2 169
[14:05:20.763] [MoreQOD] MarkLabel 2 169
[14:05:20.764] [MoreQOD] Blt_S 235
[14:05:20.764] [MoreQOD] Blt_S 237
[14:05:20.765] [MoreQOD] MarkLabel 5 277
[14:05:20.766] [MoreQOD] MarkLabel 5 277
[14:05:20.767] [MoreQOD] Blt_S 328
[14:05:20.768] [MoreQOD] Blt_S 330
[14:05:20.770] [MoreQOD] [ERROR] System.InvalidProgramException: Invalid IL code in (wrapper dynamic-method) object:getRank (Death.Items.Item): IL_0148: blt.s     IL_01a9


  at (wrapper managed-to-native) System.Delegate.CreateDelegate_internal(System.Type,object,System.Reflection.MethodInfo,bool)
  at System.Delegate.CreateDelegate (System.Type type, System.Object firstArgument, System.Reflection.MethodInfo method, System.Boolean throwOnBindFailure, System.Boolean allowClosed) [0x002f0] in <9aad1b3a47484d63ba2b3985692d80e9>:0
  at System.Delegate.CreateDelegate (System.Type type, System.Object firstArgument, System.Reflection.MethodInfo method) [0x00000] in <9aad1b3a47484d63ba2b3985692d80e9>:0
  at System.Reflection.Emit.DynamicMethod.CreateDelegate (System.Type delegateType) [0x00029] in <9aad1b3a47484d63ba2b3985692d80e9>:0
  at MQOD.Sort.GenerateILGetRankIL () [0x00957] in <1efc024047cc4f579f5b6f749046551d>:0
  at MQOD.SortShop.sortShop () [0x00028] in <1efc024047cc4f579f5b6f749046551d>:0
  at MQOD.MQOD.OnLateUpdate () [0x0037a] in <1efc024047cc4f579f5b6f749046551d>:0
  at MelonLoader.MelonEvent+<>c.<Invoke>b__1_0 (MelonLoader.LemonAction x) [0x00000] in <6425afb6ac6a429aaf770255d2f7de57>:0
  at MelonLoader.MelonEventBase`1[T].Invoke (System.Action`1[T] delegateInvoker) [0x00018] in <6425afb6ac6a429aaf770255d2f7de57>:0

I have tracked the issue down to that last call of Blt_S, because we can see from the error that the offending code happens at offset IL_0148 which corresponds to 328 in decimal in the log:

...
    il.Emit(OpCodes.Blt_S, labels[2]);
...

The generated IL uses the address IL_01a9 for labels[2] but from my logging I can see that MarkLabel(labels[2]) happens at ILOffset '169' decimal or 'A9' in hex. So IL_01a9 is off by exactly 100 in hex or 256 in decimal. So the generated IL should be "IL_0148: blt.s IL_00a9" and not "IL_0148: blt.s IL_01a9", right?

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