public void Run(ILFunction function, ILTransformContext context)
{
var visitor = new DefiniteAssignmentVisitor(function, context.CancellationToken);
function.Body.AcceptVisitor(visitor);
foreach (var v in function.Variables)
{
if (v.Kind != VariableKind.Parameter && !visitor.IsPotentiallyUsedUninitialized(v))
{
v.HasInitialValue = false;
}
}
if (function.IsIterator || function.IsAsync)
{
// In yield return + async, the C# compiler tends to store null/default(T) to variables
// when the variable goes out of scope. Remove such useless stores.
foreach (var v in function.Variables)
{
if (v.Kind == VariableKind.Local && v.StoreCount == 1 && v.LoadCount == 0 && v.AddressCount == 0)
{
if (v.StoreInstructions[0] is StLoc stloc && (stloc.Value.MatchLdNull() || stloc.Value is DefaultValue) && stloc.Parent is Block block)
{
block.Instructions.Remove(stloc);
}
}
}
}
}
public void Run(ILFunction function, ILTransformContext context)
{
var visitor = new DefiniteAssignmentVisitor(function, context.CancellationToken);
function.Body.AcceptVisitor(visitor);
foreach (var v in function.Variables)
{
if (v.Kind != VariableKind.Parameter && !visitor.IsPotentiallyUsedUninitialized(v))
{
v.HasInitialValue = false;
}
}
// Remove dead stores to variables that are never read from.
// If the stored value has some side-effect, the value is unwrapped.
// This is necessary to remove useless stores generated by some compilers, e.g., the F# compiler.
// In yield return + async, the C# compiler tends to store null/default(T) to variables
// when the variable goes out of scope.
if (function.IsAsync || function.IsIterator || context.Settings.RemoveDeadCode)
{
var variableQueue = new Queue <ILVariable>(function.Variables);
while (variableQueue.Count > 0)
{
var v = variableQueue.Dequeue();
if (v.Kind != VariableKind.Local && v.Kind != VariableKind.StackSlot)
{
continue;
}
if (v.LoadCount != 0 || v.AddressCount != 0)
{
continue;
}
foreach (var stloc in v.StoreInstructions.OfType <StLoc>().ToArray())
{
if (stloc.Parent is Block block)
{
if (SemanticHelper.IsPure(stloc.Value.Flags))
{
block.Instructions.Remove(stloc);
}
else
{
stloc.ReplaceWith(stloc.Value);
}
if (stloc.Value is LdLoc ldloc)
{
variableQueue.Enqueue(ldloc.Variable);
}
}
}
}
}
}
internal static void ResetHasInitialValueFlag(ILFunction function, ILTransformContext context)
{
var visitor = new DefiniteAssignmentVisitor(function, context.CancellationToken);
function.AcceptVisitor(visitor);
foreach (var v in function.Variables)
{
if (v.Kind != VariableKind.Parameter && !visitor.IsPotentiallyUsedUninitialized(v))
{
v.HasInitialValue = false;
}
}
}
public void Run(ILFunction function, ILTransformContext context)
{
var visitor = new DefiniteAssignmentVisitor(function, context.CancellationToken);
function.Body.AcceptVisitor(visitor);
foreach (var v in function.Variables)
{
if (v.Kind != VariableKind.Parameter && !visitor.IsPotentiallyUsedUninitialized(v))
{
v.HasInitialValue = false;
}
}
// Remove dead stores to variables that are never read from.
// If the stored value has some side-effect, the value is unwrapped.
// This is necessary to remove useless stores generated by some compilers, e.g., the F# compiler.
// In yield return + async, the C# compiler tends to store null/default(T) to variables
// when the variable goes out of scope.
if (function.IsAsync || function.IsIterator || context.Settings.RemoveDeadCode)
{
var variableQueue = new Queue <ILVariable>(function.Variables);
while (variableQueue.Count > 0)
{
var v = variableQueue.Dequeue();
if (v.Kind != VariableKind.Local && v.Kind != VariableKind.StackSlot)
{
continue;
}
// Skip variables that are captured in a mcs yield state-machine
// loads of these will only be visible after DelegateConstruction step.
if (function.StateMachineCompiledWithMono && v.StateMachineField != null)
{
continue;
}
if (v.LoadCount != 0 || v.AddressCount != 0)
{
continue;
}
foreach (var stloc in v.StoreInstructions.OfType <StLoc>().ToArray())
{
if (stloc.Parent is Block block)
{
if (SemanticHelper.IsPure(stloc.Value.Flags))
{
block.Instructions.Remove(stloc);
}
else
{
stloc.ReplaceWith(stloc.Value);
}
if (stloc.Value is LdLoc ldloc)
{
variableQueue.Enqueue(ldloc.Variable);
}
}
}
}
}
// Try to infer IType of stack slots that are of StackType.Ref:
foreach (var v in function.Variables)
{
if (v.Kind == VariableKind.StackSlot && v.StackType == StackType.Ref && v.AddressCount == 0)
{
IType newType = null;
// Multiple store are possible in case of (c ? ref a : ref b) += 1, for example.
foreach (var stloc in v.StoreInstructions.OfType <StLoc>())
{
var inferredType = stloc.Value.InferType(context.TypeSystem);
// cancel, if types of values do not match exactly
if (newType != null && !newType.Equals(inferredType))
{
newType = SpecialType.UnknownType;
break;
}
newType = inferredType;
}
// Only overwrite existing type, if a "better" type was found.
if (newType != null && newType != SpecialType.UnknownType)
{
v.Type = newType;
}
}
}
}
