static FieldDefinition CreateProfilerMarkerField(MethodDefinition methodContainingLambdaJob, ModuleDefinition moduleDefinition, JobStructForLambdaJob generatedJobStruct)
        {
            var             profilerMarkerName = generatedJobStruct.TypeDefinition.Name.Replace("<>c__DisplayClass_", "");
            FieldDefinition runWithoutJobSystemProfilerMarkerField =
                new FieldDefinition($"<>{profilerMarkerName}_profilerMarker", FieldAttributes.Private, moduleDefinition.ImportReference(typeof(ProfilerMarker)));

            methodContainingLambdaJob.DeclaringType.Fields.Add(runWithoutJobSystemProfilerMarkerField);

            // Insert instructions to create ProfilerMarker in OnCreateForCompiler
            var profilerMarkerConstructor =
                moduleDefinition.ImportReference(typeof(ProfilerMarker).GetConstructors().FirstOrDefault(
                                                     m => m.GetParameters().Count() == 1 && m.GetParameters()[0].ParameterType == typeof(string)));
            var instructionsToCreateProfilerMarker = new List <Instruction>()
            {
                Instruction.Create(OpCodes.Ldarg_0),
                Instruction.Create(OpCodes.Ldstr, profilerMarkerName),
                Instruction.Create(OpCodes.Newobj, profilerMarkerConstructor),
                Instruction.Create(OpCodes.Stfld, runWithoutJobSystemProfilerMarkerField)
            };

            InjectAndInitializeEntityQueryField.InsertIntoOnCreateForCompilerMethod(methodContainingLambdaJob.DeclaringType, instructionsToCreateProfilerMarker.ToArray());
            return(runWithoutJobSystemProfilerMarkerField);
        }
Example #2
0
        public static (JobStructForLambdaJob, List <DiagnosticMessage>) Rewrite(MethodDefinition methodContainingLambdaJob, LambdaJobDescriptionConstruction lambdaJobDescriptionConstruction)
        {
            var diagnosticMessages = new List <DiagnosticMessage>();

            if (methodContainingLambdaJob.DeclaringType.CustomAttributes.Any(c => (c.AttributeType.Name == "ExecuteAlways" && c.AttributeType.Namespace == "UnityEngine")))
            {
                diagnosticMessages.Add(UserError.DC0032(methodContainingLambdaJob.DeclaringType, methodContainingLambdaJob, lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction));
            }

            if (keepUnmodifiedVersionAroundForDebugging)
            {
                CecilHelpers.CloneMethodForDiagnosingProblems(methodContainingLambdaJob);
            }

            //in order to make it easier and safer to operate on IL, we're going to "Simplify" it.  This means transforming opcodes that have short variants, into the full one
            //so that when you analyze, you can assume (ldarg, 0) opcode + operand pair,  and don't have to go check for the shorthand version of ldarg_0, without an operand.
            //more importantly, it also rewrites branch.s (branch to a instruction that is closeby enough that the offset fits within a byte), to a regular branch instructions.
            //this is the only sane thing to do, because when we rewrite IL code, we add instructions, so it can happen that by adding instructions, what was possible to be a short
            //branch instruction, now is no longer a valid short branch target,  and cecil doesn't warn against that, it will just generate broken IL, and you'll spend a long time
            //figuring out what is going on.
            methodContainingLambdaJob.Body.SimplifyMacros();

            var methodLambdaWasEmittedAs = lambdaJobDescriptionConstruction.MethodLambdaWasEmittedAs;

            if (methodLambdaWasEmittedAs.DeclaringType.TypeReferenceEquals(methodContainingLambdaJob.DeclaringType) &&
                !lambdaJobDescriptionConstruction.AllowReferenceTypes)
            {
                // Sometimes roslyn emits the lambda as an instance method in the same type of the method that contains the lambda expression.
                // it does this only in the situation where the lambda captures a field _and_ does not capture any locals. In this case
                // there's no displayclass being created. We should figure out exactly what instruction caused this behaviour, and tell the user
                // she can't read a field like that.
                // Here is an example: https://sharplab.io/#v2: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
                var illegalFieldRead = methodLambdaWasEmittedAs.Body.Instructions.FirstOrDefault(IsIllegalFieldRead);
                if (illegalFieldRead != null)
                {
                    UserError.DC0001(methodContainingLambdaJob, illegalFieldRead, (FieldReference)illegalFieldRead.Operand).Throw();
                }

                // Similarly, we could end up here because the lambda captured neither a field nor a local but simply
                // uses the this-reference. This could be the case if the user calls a function that takes this as a
                // parameter, either explicitly (static) or implicitly (extension or member method).
                var illegalInvocations = methodLambdaWasEmittedAs.Body.Instructions.Where(IsIllegalInvocation).ToArray();
                if (illegalInvocations.Any())
                {
                    foreach (var illegalInvocation in illegalInvocations)
                    {
                        if (!IsPermittedIllegalInvocation(illegalInvocation))
                        {
                            UserError.DC0002(methodContainingLambdaJob, illegalInvocation,
                                             (MethodReference)illegalInvocation.Operand, methodLambdaWasEmittedAs.DeclaringType).Throw();
                        }
                    }

                    // We only had illegal invocations where we were invoking an allowed method on our declaring type.
                    // This is allowed as we will rewrite these invocations.
                    // When we clone this method we need to rewrite it correctly to reflect that this is the case.
                    lambdaJobDescriptionConstruction.HasAllowedMethodInvokedWithThis = true;
                }

                // This should never hit, but is here to make sure that in case we have a bug in detecting
                // why roslyn emitted it like this, we can at least report an error, instead of silently generating invalid code.
                // We do need to allow this case when we have an allowed method invoked with this that is later replaced with codegen.
                if (!lambdaJobDescriptionConstruction.HasAllowedMethodInvokedWithThis)
                {
                    InternalCompilerError.DCICE001(methodContainingLambdaJob).Throw();
                }

                bool IsIllegalFieldRead(Instruction i)
                {
                    if (i.Previous == null)
                    {
                        return(false);
                    }
                    if (i.OpCode != OpCodes.Ldfld && i.OpCode != OpCodes.Ldflda)
                    {
                        return(false);
                    }
                    return(i.Previous.OpCode == OpCodes.Ldarg_0);
                }

                bool IsIllegalInvocation(Instruction i)
                {
                    if (!i.IsInvocation(out _))
                    {
                        return(false);
                    }
                    var declaringType = methodContainingLambdaJob.DeclaringType;
                    var method        = (MethodReference)i.Operand;

                    // is it an instance method?
                    var resolvedMethod = method.Resolve();

                    if (declaringType.TypeReferenceEqualsOrInheritsFrom(method.DeclaringType) && !resolvedMethod.IsStatic)
                    {
                        return(true);
                    }

                    // is it a method that potentially takes this as a parameter?
                    foreach (var param in method.Parameters)
                    {
                        if (declaringType.TypeReferenceEqualsOrInheritsFrom(param.ParameterType) || declaringType.TypeImplements(param.ParameterType))
                        {
                            return(true);
                        }
                    }
                    return(false);
                }

                // Check for permitted illegal invocations
                // These are due to calling a method that we later stub out with codegen or also can be due to calling
                // a local method that contains a method that we stub out with codegen.
                bool IsPermittedIllegalInvocation(Instruction instruction)
                {
                    // Check to see if this method is permitted
                    if (instruction.OpCode == OpCodes.Call || instruction.OpCode == OpCodes.Callvirt)
                    {
                        var methodRef = instruction.Operand as MethodReference;
                        if (JobStructForLambdaJob.IsPermittedMethodToInvokeWithThis(methodRef))
                        {
                            return(true);
                        }
                        else
                        {
                            // Recurse into methods if they are compiler generated local methods
                            var methodDef = methodRef.Resolve();
                            if (methodDef != null && methodDef.CustomAttributes.Any(c =>
                                                                                    c.AttributeType.Name == nameof(CompilerGeneratedAttribute) &&
                                                                                    c.AttributeType.Namespace == typeof(CompilerGeneratedAttribute).Namespace))
                            {
                                foreach (var methodInstruction in methodDef.Body.Instructions)
                                {
                                    if (IsIllegalInvocation(methodInstruction) && !IsPermittedIllegalInvocation(methodInstruction))
                                    {
                                        return(false);
                                    }
                                }

                                return(true);
                            }
                        }
                    }

                    return(false);
                }
            }

            var moduleDefinition = methodContainingLambdaJob.Module;

            var body        = methodContainingLambdaJob.Body;
            var ilProcessor = body.GetILProcessor();

            VariableDefinition displayClassVariable = null;

            if (lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
            {
                bool allDelegatesAreGuaranteedNotToOutliveMethod = lambdaJobDescriptionConstruction.DisplayClass.IsValueType() || CecilHelpers.AllDelegatesAreGuaranteedNotToOutliveMethodFor(methodContainingLambdaJob);

                displayClassVariable = body.Variables.Single(v => v.VariableType.TypeReferenceEquals(lambdaJobDescriptionConstruction.DisplayClass));

                //in this step we want to get rid of the heap allocation for the delegate. In order to make the rest of the code easier to reason about and write,
                //we'll make sure that while we do this, we don't change the total stackbehaviour. Because this used to push a delegate onto the evaluation stack,
                //we also have to write something to the evaluation stack.  Later in this method it will be popped, so it doesn't matter what it is really.  I use Ldc_I4_0,
                //as I found it introduced the most reasonable artifacts when the code is decompiled back into C#.
                lambdaJobDescriptionConstruction.DelegateProducingSequence.RewriteToKeepDisplayClassOnEvaluationStack();

                if (allDelegatesAreGuaranteedNotToOutliveMethod)
                {
                    ChangeAllDisplayClassesToStructs(methodContainingLambdaJob);
                }
            }
            else
            {
                //if the lambda is not capturing, roslyn will recycle the delegate in a static field. not so great for us. let's nop out all that code.
                var instructionThatPushedDelegate = CecilHelpers.FindInstructionThatPushedArg(methodContainingLambdaJob, 1, lambdaJobDescriptionConstruction.WithCodeInvocationInstruction);

                var result = CecilHelpers.MatchesDelegateProducingPattern(methodContainingLambdaJob, instructionThatPushedDelegate, CecilHelpers.DelegateProducingPattern.MatchSide.Start);
                result?.RewriteToProduceSingleNullValue();
            }

            FieldDefinition entityQueryField = null;

            if (lambdaJobDescriptionConstruction.Kind != LambdaJobDescriptionKind.Job)
            {
                entityQueryField = InjectAndInitializeEntityQueryField.InjectAndInitialize(methodContainingLambdaJob, lambdaJobDescriptionConstruction, methodLambdaWasEmittedAs.Parameters);
            }

            var generatedJobStruct = JobStructForLambdaJob.CreateNewJobStruct(lambdaJobDescriptionConstruction);

            if (generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst != null)
            {
                var constructorInfo = generatedJobStruct.ExecuteDelegateType.GetConstructors().First(c => c.GetParameters().Length == 2);

                var instructions = new List <Instruction>()
                {
                    Instruction.Create(OpCodes.Ldnull),
                    Instruction.Create(OpCodes.Ldftn, generatedJobStruct.RunWithoutJobSystemMethod),
                    Instruction.Create(OpCodes.Newobj, moduleDefinition.ImportReference(constructorInfo)),
                    Instruction.Create(OpCodes.Stsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst)
                };
                if (generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst != null)
                {
                    instructions.Add(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));

                    var methodInfo = typeof(InternalCompilerInterface)
                                     .GetMethods(BindingFlags.Static | BindingFlags.Public)
                                     .Where(m => m.Name == nameof(InternalCompilerInterface.BurstCompile))
                                     .Single(m => m.GetParameters().First().ParameterType == generatedJobStruct.ExecuteDelegateType);

                    instructions.Add(Instruction.Create(OpCodes.Call, moduleDefinition.ImportReference(methodInfo)));
                    instructions.Add(Instruction.Create(OpCodes.Stsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst));
                }
                InjectAndInitializeEntityQueryField.InsertIntoOnCreateForCompilerMethod(methodContainingLambdaJob.DeclaringType, instructions.ToArray());
            }

            IEnumerable <Instruction> InstructionsToReplaceScheduleInvocationWith()
            {
                var newJobStructVariable = new VariableDefinition(generatedJobStruct.TypeDefinition);

                body.Variables.Add(newJobStructVariable);

                bool storeJobHandleInVariable = (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule ||
                                                 lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.ScheduleParallel);
                VariableDefinition tempStorageForJobHandle = null;

                if (storeJobHandleInVariable)
                {
                    tempStorageForJobHandle = new VariableDefinition(moduleDefinition.ImportReference(typeof(JobHandle)));
                    body.Variables.Add(tempStorageForJobHandle);

                    // If we aren't using an implicit system dependency and we're replacing the .Schedule() function on the description,
                    // the lambdajobdescription and the jobhandle argument to that function will be on the stack.
                    // we're going to need the jobhandle later when we call JobChunkExtensions.Schedule(), so lets stuff it in a variable.

                    // If we are using implicit system dependency, lets put that in our temp instead.
                    if (lambdaJobDescriptionConstruction.UseImplicitSystemDependency)
                    {
                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Call, moduleDefinition.ImportReference(typeof(SystemBase).GetMethod("get_Dependency", BindingFlags.Instance | BindingFlags.NonPublic))));
                    }
                    yield return(Instruction.Create(OpCodes.Stloc, tempStorageForJobHandle));
                }

                //pop the Description struct off the stack, its services are no longer required
                yield return(Instruction.Create(OpCodes.Pop));

                yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                yield return(Instruction.Create(OpCodes.Initobj, generatedJobStruct.TypeDefinition));

                // Call ScheduleTimeInitializeMethod
                yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                yield return(Instruction.Create(OpCodes.Ldarg_0));

                if (lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
                {
                    //only when the lambda is capturing, did we emit the ScheduleTimeInitialize method to take a displayclass argument
                    var opcode = methodLambdaWasEmittedAs.DeclaringType.IsValueType() ? OpCodes.Ldloca : OpCodes.Ldloc;
                    yield return(Instruction.Create(opcode, displayClassVariable));
                }

                yield return(Instruction.Create(OpCodes.Call, generatedJobStruct.ScheduleTimeInitializeMethod));

                MethodInfo FindRunOrScheduleMethod()
                {
                    switch (lambdaJobDescriptionConstruction.Kind)
                    {
                    case LambdaJobDescriptionKind.Entities:
                    case LambdaJobDescriptionKind.Chunk:
                        if (lambdaJobDescriptionConstruction.IsInSystemBase)
                        {
                            switch (lambdaJobDescriptionConstruction.ExecutionMode)
                            {
                            case ExecutionMode.Run:
                                return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunJobChunk)));

                            case ExecutionMode.Schedule:
                                return(typeof(JobChunkExtensions).GetMethod(nameof(JobChunkExtensions.ScheduleSingle)));

                            case ExecutionMode.ScheduleParallel:
                                return(typeof(JobChunkExtensions).GetMethod(nameof(JobChunkExtensions.ScheduleParallel)));

                            default:
                                throw new ArgumentOutOfRangeException();
                            }
                        }
                        else
                        {
                            // Keep legacy behaviour in JobComponentSystems intact (aka "Schedule" equals "ScheduleParallel")
                            if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                            {
                                return(typeof(JobChunkExtensions).GetMethod(nameof(JobChunkExtensions.ScheduleParallel)));
                            }
                            return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunJobChunk)));
                        }

                    case LambdaJobDescriptionKind.Job:
                        if (lambdaJobDescriptionConstruction.IsInSystemBase)
                        {
                            switch (lambdaJobDescriptionConstruction.ExecutionMode)
                            {
                            case ExecutionMode.Run:
                                return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunIJob)));

                            case ExecutionMode.Schedule:
                                return(typeof(IJobExtensions).GetMethod(nameof(IJobExtensions.Schedule)));

                            default:
                                throw new ArgumentOutOfRangeException();
                            }
                        }
                        else
                        {
                            if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                            {
                                return(typeof(IJobExtensions).GetMethod(nameof(IJobExtensions.Schedule)));
                            }
                            return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunIJob)));
                        }

                    default:
                        throw new ArgumentOutOfRangeException();
                    }
                }

                // Call CompleteDependency method to complete previous dependencies if we are running in SystemBase
                if (lambdaJobDescriptionConstruction.IsInSystemBase && lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Run)
                {
                    yield return(Instruction.Create(OpCodes.Ldarg_0));

                    yield return(Instruction.Create(OpCodes.Call,
                                                    moduleDefinition.ImportReference(typeof(SystemBase).GetMethod("CompleteDependency", BindingFlags.Instance | BindingFlags.NonPublic))));
                }

                MethodReference runOrScheduleMethod;

                if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    runOrScheduleMethod = generatedJobStruct.TypeDefinition.Methods.First(definition => definition.Name == "Execute");
                }
                else
                {
                    runOrScheduleMethod = moduleDefinition.ImportReference(FindRunOrScheduleMethod())
                                          .MakeGenericInstanceMethod(generatedJobStruct.TypeDefinition);
                }

                if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));
                }
                else
                {
                    yield return(Instruction.Create(runOrScheduleMethod.Parameters.First().ParameterType.IsByReference ? OpCodes.Ldloca : OpCodes.Ldloc, newJobStructVariable));
                }

                switch (lambdaJobDescriptionConstruction.Kind)
                {
                case LambdaJobDescriptionKind.Entities:
                case LambdaJobDescriptionKind.Chunk:
                    if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                    {
                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldfld, entityQueryField));
                    }
                    else
                    {
                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldfld, entityQueryField));
                    }
                    break;

                case LambdaJobDescriptionKind.Job:
                    //job.Schedule() takes no entityQuery...
                    break;
                }

                // Store returned JobHandle in temp varaible or back in SystemBase.depenedency
                if (storeJobHandleInVariable)
                {
                    yield return(Instruction.Create(OpCodes.Ldloc, tempStorageForJobHandle));
                }
                else if (lambdaJobDescriptionConstruction.UseImplicitSystemDependency)
                {
                    yield return(Instruction.Create(OpCodes.Ldarg_0));

                    yield return(Instruction.Create(OpCodes.Call,
                                                    moduleDefinition.ImportReference(typeof(SystemBase).GetMethod("get_Dependency", BindingFlags.Instance | BindingFlags.NonPublic))));
                }

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Run &&
                    !lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    if (!lambdaJobDescriptionConstruction.UsesBurst)
                    {
                        yield return(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));
                    }
                    else
                    {
                        yield return(Instruction.Create(OpCodes.Call, moduleDefinition.ImportReference(typeof(JobsUtility).GetMethod("get_" + nameof(JobsUtility.JobCompilerEnabled)))));

                        var targetInstruction = Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst);
                        yield return(Instruction.Create(OpCodes.Brtrue, targetInstruction));

                        yield return(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));

                        var finalBranchDestination = Instruction.Create(OpCodes.Nop);
                        yield return(Instruction.Create(OpCodes.Br, finalBranchDestination));

                        yield return(targetInstruction);

                        yield return(finalBranchDestination);
                    }
                }

                yield return(Instruction.Create(OpCodes.Call, runOrScheduleMethod));

                if (lambdaJobDescriptionConstruction.UseImplicitSystemDependency)
                {
                    yield return(Instruction.Create(OpCodes.Stloc, tempStorageForJobHandle));

                    yield return(Instruction.Create(OpCodes.Ldarg_0));

                    yield return(Instruction.Create(OpCodes.Ldloc, tempStorageForJobHandle));

                    yield return(Instruction.Create(OpCodes.Call,
                                                    moduleDefinition.ImportReference(typeof(SystemBase).GetMethod("set_Dependency", BindingFlags.Instance | BindingFlags.NonPublic))));
                }

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Run &&
                    generatedJobStruct.WriteToDisplayClassMethod != null && lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
                {
                    yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                    var opcode = methodLambdaWasEmittedAs.DeclaringType.IsValueType() ? OpCodes.Ldloca : OpCodes.Ldloc;
                    yield return(Instruction.Create(opcode, displayClassVariable));

                    yield return(Instruction.Create(OpCodes.Call, generatedJobStruct.WriteToDisplayClassMethod));
                }
            }

            foreach (var invokedMethod in lambdaJobDescriptionConstruction.InvokedConstructionMethods)
            {
                bool invokedMethodServesNoPurposeAtRuntime =
                    invokedMethod.MethodName != nameof(LambdaJobQueryConstructionMethods.WithSharedComponentFilter);

                if (invokedMethodServesNoPurposeAtRuntime)
                {
                    CecilHelpers.EraseMethodInvocationFromInstructions(ilProcessor, invokedMethod.InstructionInvokingMethod);
                }
                else
                {
                    // Rewrite WithSharedComponentFilter calls as they need to modify EntityQuery dynamically
                    if (invokedMethod.MethodName ==
                        nameof(LambdaJobQueryConstructionMethods.WithSharedComponentFilter))
                    {
                        var setSharedComponentFilterOnQueryMethod
                            = moduleDefinition.ImportReference(
                                  (lambdaJobDescriptionConstruction.Kind == LambdaJobDescriptionKind.Entities ? typeof(ForEachLambdaJobDescription_SetSharedComponent) : typeof(LambdaJobChunkDescription_SetSharedComponent)).GetMethod(
                                      nameof(LambdaJobChunkDescription_SetSharedComponent.SetSharedComponentFilterOnQuery)));
                        var callingTypeReference = lambdaJobDescriptionConstruction.IsInSystemBase
                            ? moduleDefinition.ImportReference(typeof(ForEachLambdaJobDescription))
                            : moduleDefinition.ImportReference(typeof(ForEachLambdaJobDescriptionJCS));
                        MethodReference genericSetSharedComponentFilterOnQueryMethod
                            = setSharedComponentFilterOnQueryMethod.MakeGenericInstanceMethod(
                                  new TypeReference[] { callingTypeReference }.Concat(invokedMethod.TypeArguments).ToArray());

                        // Change invocation to invocation of helper method and add EntityQuery parameter to be modified
                        var setSharedComponentFilterOnQueryInstructions = new List <Instruction>
                        {
                            Instruction.Create(OpCodes.Ldarg_0),
                            Instruction.Create(OpCodes.Ldfld, entityQueryField),
                            Instruction.Create(OpCodes.Call, genericSetSharedComponentFilterOnQueryMethod)
                        };

                        ilProcessor.Replace(invokedMethod.InstructionInvokingMethod, setSharedComponentFilterOnQueryInstructions);
                    }
                }
            }

            var scheduleInstructions = InstructionsToReplaceScheduleInvocationWith().ToList();

            ilProcessor.InsertAfter(lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction, scheduleInstructions);
            lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction.MakeNOP();

            var codegenInitializeMethod = GetOrMakeOnCreateForCompilerMethod(lambdaJobDescriptionConstruction.ContainingMethod.DeclaringType);

            return(generatedJobStruct, diagnosticMessages);
        }
        public static JobStructForLambdaJob Rewrite(MethodDefinition methodContainingLambdaJob, LambdaJobDescriptionConstruction lambdaJobDescriptionConstruction, List <DiagnosticMessage> warnings)
        {
            if (methodContainingLambdaJob.DeclaringType.CustomAttributes.Any(c => (c.AttributeType.Name == "ExecuteAlways" && c.AttributeType.Namespace == "UnityEngine")))
            {
                warnings.Add(UserError.DC0032(methodContainingLambdaJob.DeclaringType, methodContainingLambdaJob, lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction));
            }

            if (keepUnmodifiedVersionAroundForDebugging)
            {
                CecilHelpers.CloneMethodForDiagnosingProblems(methodContainingLambdaJob);
            }

            //in order to make it easier and safer to operate on IL, we're going to "Simplify" it.  This means transforming opcodes that have short variants, into the full one
            //so that when you analyze, you can assume (ldarg, 0) opcode + operand pair,  and don't have to go check for the shorthand version of ldarg_0, without an operand.
            //more importantly, it also rewrites branch.s (branch to a instruction that is closeby enough that the offset fits within a byte), to a regular branch instructions.
            //this is the only sane thing to do, because when we rewrite IL code, we add instructions, so it can happen that by adding instructions, what was possible to be a short
            //branch instruction, now is no longer a valid short branch target,  and cecil doesn't warn against that, it will just generate broken IL, and you'll spend a long time
            //figuring out what is going on.
            methodContainingLambdaJob.Body.SimplifyMacros();

            var methodLambdaWasEmittedAs = lambdaJobDescriptionConstruction.MethodLambdaWasEmittedAs;

            if (methodLambdaWasEmittedAs.DeclaringType.TypeReferenceEquals(methodContainingLambdaJob.DeclaringType) && !lambdaJobDescriptionConstruction.AllowReferenceTypes)
            {
                //sometimes roslyn emits the lambda as an instance method in the same type of the method that contains the lambda expression.
                //it does this only in the situation where the lambda captures a field _and_ does not capture any locals.  in this case
                //there's no displayclass being created.  We should figure out exactly what instruction caused this behaviour, and tell the user
                //she can't read a field like that.

                var illegalFieldRead = methodLambdaWasEmittedAs.Body.Instructions.FirstOrDefault(i => i.OpCode == OpCodes.Ldfld && i.Previous?.OpCode == OpCodes.Ldarg_0);
                if (illegalFieldRead != null)
                {
                    UserError.DC0001(methodContainingLambdaJob, illegalFieldRead, (FieldReference)illegalFieldRead.Operand).Throw();
                }

                var illegalInvocation = methodLambdaWasEmittedAs.Body.Instructions.FirstOrDefault(i => i.IsInvocation() && methodContainingLambdaJob.DeclaringType.TypeReferenceEqualsOrInheritsFrom(((MethodReference)i.Operand).DeclaringType));
                if (illegalInvocation != null)
                {
                    UserError.DC0002(methodContainingLambdaJob, illegalInvocation, (MethodReference)illegalInvocation.Operand).Throw();
                }

                //this should never hit, but is here to make sure that in case we have a bug in detecting why roslyn emitted it like this, we can at least report an error, instead of silently generating invalid code.
                InternalCompilerError.DCICE001(methodContainingLambdaJob).Throw();
            }

            var moduleDefinition = methodContainingLambdaJob.Module;

            var body        = methodContainingLambdaJob.Body;
            var ilProcessor = body.GetILProcessor();

            VariableDefinition displayClassVariable = null;

            if (lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
            {
                bool allDelegatesAreGuaranteedNotToOutliveMethod = lambdaJobDescriptionConstruction.DisplayClass.IsValueType || CecilHelpers.AllDelegatesAreGuaranteedNotToOutliveMethodFor(methodContainingLambdaJob);


                displayClassVariable = body.Variables.Single(v => v.VariableType.TypeReferenceEquals(lambdaJobDescriptionConstruction.DisplayClass));

                //in this step we want to get rid of the heap allocation for the delegate. In order to make the rest of the code easier to reason about and write,
                //we'll make sure that while we do this, we don't change the total stackbehaviour. Because this used to push a delegate onto the evaluation stack,
                //we also have to write something to the evaluation stack.  Later in this method it will be popped, so it doesn't matter what it is really.  I use Ldc_I4_0,
                //as I found it introduced the most reasonable artifacts when the code is decompiled back into C#.
                lambdaJobDescriptionConstruction.DelegateProducingSequence.RewriteToKeepDisplayClassOnEvaluationStack();

                if (allDelegatesAreGuaranteedNotToOutliveMethod)
                {
                    ChangeAllDisplayClassesToStructs(methodContainingLambdaJob);
                }
            }
            else
            {
                //if the lambda is not capturing, roslyn will recycle the delegate in a static field. not so great for us. let's nop out all that code.
                var instructionThatPushedDelegate = CecilHelpers.FindInstructionThatPushedArg(methodContainingLambdaJob, 1, lambdaJobDescriptionConstruction.WithCodeInvocationInstruction);

                var result = CecilHelpers.MatchesDelegateProducingPattern(methodContainingLambdaJob, instructionThatPushedDelegate, CecilHelpers.DelegateProducingPattern.MatchSide.Start);
                result?.RewriteToProduceSingleNullValue();
            }

            FieldDefinition entityQueryField = null;

            if (lambdaJobDescriptionConstruction.Kind != LambdaJobDescriptionKind.Job)
            {
                entityQueryField = InjectAndInitializeEntityQueryField.InjectAndInitialize(methodContainingLambdaJob, lambdaJobDescriptionConstruction, methodLambdaWasEmittedAs.Parameters);
            }

            var generatedJobStruct = JobStructForLambdaJob.CreateNewJobStruct(lambdaJobDescriptionConstruction);

            if (generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst != null)
            {
                var constructorInfo = generatedJobStruct.ExecuteDelegateType.GetConstructors().First(c => c.GetParameters().Length == 2);

                var instructions = new List <Instruction>()
                {
                    Instruction.Create(OpCodes.Ldnull),
                    Instruction.Create(OpCodes.Ldftn, generatedJobStruct.RunWithoutJobSystemMethod),
                    Instruction.Create(OpCodes.Newobj, moduleDefinition.ImportReference(constructorInfo)),
                    Instruction.Create(OpCodes.Stsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst)
                };
                if (generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst != null)
                {
                    instructions.Add(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));

                    var methodInfo = typeof(InternalCompilerInterface)
                                     .GetMethods(BindingFlags.Static | BindingFlags.Public)
                                     .Where(m => m.Name == nameof(InternalCompilerInterface.BurstCompile))
                                     .Single(m => m.GetParameters().First().ParameterType == generatedJobStruct.ExecuteDelegateType);

                    instructions.Add(Instruction.Create(OpCodes.Call, moduleDefinition.ImportReference(methodInfo)));
                    instructions.Add(Instruction.Create(OpCodes.Stsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst));
                }
                InjectAndInitializeEntityQueryField.InsertIntoOnCreateForCompilerMethod(methodContainingLambdaJob.DeclaringType, instructions.ToArray());
            }

            IEnumerable <Instruction> InstructionsToReplaceScheduleInvocationWith()
            {
                var newJobStructVariable = new VariableDefinition(generatedJobStruct.TypeDefinition);

                body.Variables.Add(newJobStructVariable);

                VariableDefinition tempStorageForJobHandle = null;

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                {
                    tempStorageForJobHandle = new VariableDefinition(moduleDefinition.ImportReference(typeof(JobHandle)));
                    body.Variables.Add(tempStorageForJobHandle);

                    //since we're replacing the .Schedule() function on the description, the lambdajobdescription and the jobhandle argument to that function will be on the stack.
                    //we're going to need the jobhandle later when we call JobChunkExtensions.Schedule(), so lets stuff it in a variable.
                    yield return(Instruction.Create(OpCodes.Stloc, tempStorageForJobHandle));
                }

                //pop the Description struct off the stack, its services are no longer required
                yield return(Instruction.Create(OpCodes.Pop));

                yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                yield return(Instruction.Create(OpCodes.Initobj, generatedJobStruct.TypeDefinition));

                // Call ScheduleTimeInitializeMethod
                yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                yield return(Instruction.Create(OpCodes.Ldarg_0));

                if (lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
                {
                    //only when the lambda is capturing, did we emit the ScheduleTimeInitialize method to take a displayclass argument
                    var opcode = methodLambdaWasEmittedAs.DeclaringType.IsValueType ? OpCodes.Ldloca : OpCodes.Ldloc;
                    yield return(Instruction.Create(opcode, displayClassVariable));
                }

                yield return(Instruction.Create(OpCodes.Call, generatedJobStruct.ScheduleTimeInitializeMethod));

                MethodInfo FindRunOrScheduleMethod()
                {
                    switch (lambdaJobDescriptionConstruction.Kind)
                    {
                    case LambdaJobDescriptionKind.Entities:
                    case LambdaJobDescriptionKind.Chunk:
                        if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                        {
                            return(typeof(JobChunkExtensions).GetMethod(nameof(JobChunkExtensions.Schedule)));
                        }
                        return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunJobChunk)));

                    case LambdaJobDescriptionKind.Job:
                        if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                        {
                            return(typeof(IJobExtensions).GetMethod(nameof(IJobExtensions.Schedule)));
                        }
                        return(typeof(InternalCompilerInterface).GetMethod(nameof(InternalCompilerInterface.RunIJob)));

                    default:
                        throw new ArgumentOutOfRangeException();
                    }
                }

                MethodReference runOrScheduleMethod;

                if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    runOrScheduleMethod = generatedJobStruct.TypeDefinition.Methods.First(definition => definition.Name == "Execute");
                }
                else
                {
                    runOrScheduleMethod = moduleDefinition.ImportReference(FindRunOrScheduleMethod())
                                          .MakeGenericInstanceMethod(generatedJobStruct.TypeDefinition);
                }

                if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));
                }
                else
                {
                    yield return(Instruction.Create(runOrScheduleMethod.Parameters.First().ParameterType.IsByReference ? OpCodes.Ldloca : OpCodes.Ldloc, newJobStructVariable));
                }

                switch (lambdaJobDescriptionConstruction.Kind)
                {
                case LambdaJobDescriptionKind.Entities:
                case LambdaJobDescriptionKind.Chunk:
                    if (lambdaJobDescriptionConstruction.WithStructuralChanges)
                    {
                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldfld, entityQueryField));
                    }
                    else
                    {
                        yield return(Instruction.Create(OpCodes.Ldarg_0));

                        yield return(Instruction.Create(OpCodes.Ldfld, entityQueryField));
                    }
                    break;

                case LambdaJobDescriptionKind.Job:
                    //job.Schedule() takes no entityQuery...
                    break;
                }

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Schedule)
                {
                    yield return(Instruction.Create(OpCodes.Ldloc, tempStorageForJobHandle));
                }

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Run &&
                    !lambdaJobDescriptionConstruction.WithStructuralChanges)
                {
                    if (!lambdaJobDescriptionConstruction.UsesBurst)
                    {
                        yield return(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));
                    }
                    else
                    {
                        yield return(Instruction.Create(OpCodes.Call, moduleDefinition.ImportReference(typeof(JobsUtility).GetMethod("get_" + nameof(JobsUtility.JobCompilerEnabled)))));

                        var targetInstruction = Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldBurst);
                        yield return(Instruction.Create(OpCodes.Brtrue, targetInstruction));

                        yield return(Instruction.Create(OpCodes.Ldsfld, generatedJobStruct.RunWithoutJobSystemDelegateFieldNoBurst));

                        var finalBranchDestination = Instruction.Create(OpCodes.Nop);
                        yield return(Instruction.Create(OpCodes.Br, finalBranchDestination));

                        yield return(targetInstruction);

                        yield return(finalBranchDestination);
                    }
                }

                yield return(Instruction.Create(OpCodes.Call, runOrScheduleMethod));

                if (lambdaJobDescriptionConstruction.ExecutionMode == ExecutionMode.Run &&
                    generatedJobStruct.WriteToDisplayClassMethod != null && lambdaJobDescriptionConstruction.DelegateProducingSequence.CapturesLocals)
                {
                    yield return(Instruction.Create(OpCodes.Ldloca, newJobStructVariable));

                    var opcode = methodLambdaWasEmittedAs.DeclaringType.IsValueType ? OpCodes.Ldloca : OpCodes.Ldloc;
                    yield return(Instruction.Create(opcode, displayClassVariable));

                    yield return(Instruction.Create(OpCodes.Call, generatedJobStruct.WriteToDisplayClassMethod));
                }
            }

            foreach (var invokedMethod in lambdaJobDescriptionConstruction.InvokedConstructionMethods)
            {
                bool invokedMethodServesNoPurposeAtRuntime =
                    invokedMethod.MethodName != nameof(LambdaJobQueryConstructionMethods.WithSharedComponentFilter);

                if (invokedMethodServesNoPurposeAtRuntime)
                {
                    CecilHelpers.EraseMethodInvocationFromInstructions(ilProcessor, invokedMethod.InstructionInvokingMethod);
                }
                else
                {
                    // Rewrite WithSharedComponentFilter calls as they need to modify EntityQuery dynamically
                    if (invokedMethod.MethodName ==
                        nameof(LambdaJobQueryConstructionMethods.WithSharedComponentFilter))
                    {
                        var setSharedComponentFilterOnQueryMethod
                            = moduleDefinition.ImportReference(
                                  (lambdaJobDescriptionConstruction.Kind == LambdaJobDescriptionKind.Entities ? typeof(ForEachLambdaJobDescription_SetSharedComponent) : typeof(LambdaJobChunkDescription_SetSharedComponent)).GetMethod(
                                      nameof(LambdaJobChunkDescription_SetSharedComponent
                                             .SetSharedComponentFilterOnQuery)));
                        MethodReference genericSetSharedComponentFilterOnQueryMethod
                            = setSharedComponentFilterOnQueryMethod.MakeGenericInstanceMethod(invokedMethod.TypeArguments);

                        // Change invocation to invocation of helper method and add EntityQuery parameter to be modified
                        var setSharedComponentFilterOnQueryInstructions = new List <Instruction>
                        {
                            Instruction.Create(OpCodes.Ldarg_0),
                            Instruction.Create(OpCodes.Ldfld, entityQueryField),
                            Instruction.Create(OpCodes.Call, genericSetSharedComponentFilterOnQueryMethod)
                        };

                        ilProcessor.Replace(invokedMethod.InstructionInvokingMethod,
                                            setSharedComponentFilterOnQueryInstructions);
                    }
                }
            }

            var scheduleInstructions = InstructionsToReplaceScheduleInvocationWith().ToList();

            ilProcessor.InsertAfter(lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction, scheduleInstructions);
            lambdaJobDescriptionConstruction.ScheduleOrRunInvocationInstruction.MakeNOP();

            var codegenInitializeMethod = GetOrMakeOnCreateForCompilerMethod(lambdaJobDescriptionConstruction.ContainingMethod.DeclaringType);

            return(generatedJobStruct);
        }