//
// Author:
// Miguel de Icaza (miguel@ximian.com)
-// Martin Baulig (martin@gnome.org)
+// Martin Baulig (martin@ximian.com)
//
// (C) 2001, 2002, 2003 Ximian, Inc.
+// (C) 2004 Novell, Inc
//
using System;
using System.Reflection;
/// </remarks>
public interface IAssignMethod {
//
- // This method will emit the code for the actual assignment
+ // This is an extra version of Emit. If leave_copy is `true'
+ // A copy of the expression will be left on the stack at the
+ // end of the code generated for EmitAssign
//
- void EmitAssign (EmitContext ec, Expression source);
-
- //
- // This method is invoked before any code generation takes
- // place, and it is a mechanism to inform that the expression
- // will be invoked more than once, and that the method should
- // use temporary values to avoid having side effects
+ void Emit (EmitContext ec, bool leave_copy);
+
//
- // Example: a [ g () ] ++
+ // This method does the assignment
+ // `source' will be stored into the location specified by `this'
+ // if `leave_copy' is true, a copy of `source' will be left on the stack
+ // if `prepare_for_load' is true, when `source' is emitted, there will
+ // be data on the stack that it can use to compuatate its value. This is
+ // for expressions like a [f ()] ++, where you can't call `f ()' twice.
//
- void CacheTemporaries (EmitContext ec);
+ void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool prepare_for_load);
+
+ /*
+ For simple assignments, this interface is very simple, EmitAssign is called with source
+ as the source expression and leave_copy and prepare_for_load false.
+
+ For compound assignments it gets complicated.
+
+ EmitAssign will be called as before, however, prepare_for_load will be
+ true. The @source expression will contain an expression
+ which calls Emit. So, the calls look like:
+
+ this.EmitAssign (ec, source, false, true) ->
+ source.Emit (ec); ->
+ [...] ->
+ this.Emit (ec, false); ->
+ end this.Emit (ec, false); ->
+ end [...]
+ end source.Emit (ec);
+ end this.EmitAssign (ec, source, false, true)
+
+
+ When prepare_for_load is true, EmitAssign emits a `token' on the stack that
+ Emit will use for its state.
+
+ Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
+
+ Here is the call tree again. This time, each call is annotated with the IL
+ it produces:
+
+ this.EmitAssign (ec, source, false, true)
+ call f
+ dup
+
+ Binary.Emit ()
+ this.Emit (ec, false);
+ ldfld y
+ end this.Emit (ec, false);
+
+ IntConstant.Emit ()
+ ldc.i4.1
+ end IntConstant.Emit
+
+ add
+ end Binary.Emit ()
+
+ stfld
+ end this.EmitAssign (ec, source, false, true)
+
+ Observe two things:
+ 1) EmitAssign left a token on the stack. It was the result of f ().
+ 2) This token was used by Emit
+
+ leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
+ of the expression at that point in evaluation. This is used for pre/post inc/dec
+ and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
+
+ this.EmitAssign (ec, source, true, true)
+ call f
+ dup
+
+ Binary.Emit ()
+ this.Emit (ec, false);
+ ldfld y
+ end this.Emit (ec, false);
+
+ IntConstant.Emit ()
+ ldc.i4.1
+ end IntConstant.Emit
+
+ add
+ end Binary.Emit ()
+
+ dup
+ stloc temp
+ stfld
+ ldloc temp
+ end this.EmitAssign (ec, source, true, true)
+
+ And with it true in Emit
+
+ this.EmitAssign (ec, source, false, true)
+ call f
+ dup
+
+ Binary.Emit ()
+ this.Emit (ec, true);
+ ldfld y
+ dup
+ stloc temp
+ end this.Emit (ec, true);
+
+ IntConstant.Emit ()
+ ldc.i4.1
+ end IntConstant.Emit
+
+ add
+ end Binary.Emit ()
+
+ stfld
+ ldloc temp
+ end this.EmitAssign (ec, source, false, true)
+
+ Note that these two examples are what happens for ++x and x++, respectively.
+ */
}
/// <summary>
/// The local temporary is used to alter the normal flow of code generation
/// basically it creates a local variable, and its emit instruction generates
/// code to access this value, return its address or save its value.
+ ///
+ /// If `is_address' is true, then the value that we store is the address to the
+ /// real value, and not the value itself.
+ ///
+ /// This is needed for a value type, because otherwise you just end up making a
+ /// copy of the value on the stack and modifying it. You really need a pointer
+ /// to the origional value so that you can modify it in that location. This
+ /// Does not happen with a class because a class is a pointer -- so you always
+ /// get the indirection.
+ ///
+ /// The `is_address' stuff is really just a hack. We need to come up with a better
+ /// way to handle it.
/// </remarks>
public class LocalTemporary : Expression, IMemoryLocation {
LocalBuilder builder;
+ bool is_address;
- public LocalTemporary (EmitContext ec, Type t)
+ public LocalTemporary (EmitContext ec, Type t) : this (ec, t, false) {}
+
+ public LocalTemporary (EmitContext ec, Type t, bool is_address)
{
type = t;
eclass = ExprClass.Value;
loc = Location.Null;
- builder = ec.GetTemporaryLocal (t);
+ builder = ec.GetTemporaryLocal (is_address ? TypeManager.GetReferenceType (t): t);
+ this.is_address = is_address;
}
- public void Release (EmitContext ec)
- {
- ec.FreeTemporaryLocal (builder, type);
- builder = null;
- }
-
public LocalTemporary (LocalBuilder b, Type t)
{
type = t;
loc = Location.Null;
builder = b;
}
+
+ public void Release (EmitContext ec)
+ {
+ ec.FreeTemporaryLocal (builder, type);
+ builder = null;
+ }
public override Expression DoResolve (EmitContext ec)
{
public override void Emit (EmitContext ec)
{
- ec.ig.Emit (OpCodes.Ldloc, builder);
+ ILGenerator ig = ec.ig;
+
+ ig.Emit (OpCodes.Ldloc, builder);
+ // we need to copy from the pointer
+ if (is_address)
+ LoadFromPtr (ig, type);
}
+ // NB: if you have `is_address' on the stack there must
+ // be a managed pointer. Otherwise, it is the type from
+ // the ctor.
public void Store (EmitContext ec)
{
- ec.ig.Emit (OpCodes.Stloc, builder);
+ ILGenerator ig = ec.ig;
+ ig.Emit (OpCodes.Stloc, builder);
}
public void AddressOf (EmitContext ec, AddressOp mode)
{
- ec.ig.Emit (OpCodes.Ldloca, builder);
+ // if is_address, than this is just the address anyways,
+ // so we just return this.
+ ILGenerator ig = ec.ig;
+
+ if (is_address)
+ ig.Emit (OpCodes.Ldloc, builder);
+ else
+ ig.Emit (OpCodes.Ldloca, builder);
+ }
+
+ public bool PointsToAddress {
+ get {
+ return is_address;
+ }
}
}
source = embedded = ((Assign) source).GetEmbeddedAssign (loc);
real_source = source = source.Resolve (ec);
- if (source == null)
+ if (source == null) {
+ // Ensure that we don't propagate the error as spurious "uninitialized variable" errors.
+ target = target.ResolveLValue (ec, EmptyExpression.Null, Location);
return null;
+ }
//
// This is used in an embedded assignment.
if (embedded != null)
source = (embedded.temp != null) ? embedded.temp : embedded.source;
- target = target.ResolveLValue (ec, source);
+ target = target.ResolveLValue (ec, source, Location);
if (target == null)
return null;
+ if (source.Equals (target)) {
+ Report.Warning (1717, 3, loc, "Assignment made to same variable; did you mean to assign something else?");
+ }
+
Type target_type = target.Type;
Type source_type = real_source.Type;
}
}
}
-
- if (source is New && target_type.IsValueType &&
- (target.eclass != ExprClass.IndexerAccess) && (target.eclass != ExprClass.PropertyAccess)){
- New n = (New) source;
- if (n.SetValueTypeVariable (target))
- return n;
- else
+ FieldExpr field_exp = target as FieldExpr;
+ if (field_exp != null && field_exp.DeclaringType.IsValueType && !ec.IsConstructor && !ec.IsFieldInitializer) {
+ field_exp = field_exp.InstanceExpression as FieldExpr;
+ if (field_exp != null && field_exp.FieldInfo.IsInitOnly) {
+ if (field_exp.IsStatic) {
+ Report.Error (1650, loc, "Members of static readonly field '{0}' cannot be assigned to " +
+ "(except in a static constructor or a variable initializer)", TypeManager.GetFullNameSignature (field_exp.FieldInfo));
+ } else {
+ Report.Error (1648, loc, "Members of readonly field '{0}' cannot be assigned to " +
+ "(except in a constructor or a variable initializer)", TypeManager.GetFullNameSignature (field_exp.FieldInfo));
+ }
return null;
+ }
}
if (!(target is IAssignMethod) && (target.eclass != ExprClass.EventAccess)) {
}
if ((source.eclass == ExprClass.Type) && (source is TypeExpr)) {
- source.Error_UnexpectedKind ("variable or value");
+ source.Error_UnexpectedKind ("variable or value", loc);
return null;
- } else if (!RootContext.V2 && (source is MethodGroupExpr)){
+ } else if ((RootContext.Version == LanguageVersion.ISO_1) &&
+ (source is MethodGroupExpr)){
((MethodGroupExpr) source).ReportUsageError ();
return null;
}
- if (target_type == source_type)
+ if (target_type == source_type){
+ if (source is New && target_type.IsValueType &&
+ (target.eclass != ExprClass.IndexerAccess) && (target.eclass != ExprClass.PropertyAccess)){
+ New n = (New) source;
+
+ if (n.SetValueTypeVariable (target))
+ return n;
+ else
+ return null;
+ }
+
return this;
-
+ }
+
//
// If this assignemnt/operator was part of a compound binary
// operator, then we allow an explicit conversion, as detailed
// 2. and the original right side is implicitly convertible to
// the type of target
//
- if (Convert.ImplicitStandardConversionExists (a.original_source, target_type))
+ if (Convert.ImplicitStandardConversionExists (ec, a.original_source, target_type))
return this;
//
}
Expression temp_source = (temp != null) ? temp : source;
- ((IAssignMethod) target).EmitAssign (ec, temp_source);
+ ((IAssignMethod) target).EmitAssign (ec, temp_source, false, false);
return temp_source;
}
((EventExpr) target).EmitAddOrRemove (ec, source);
return;
}
-
- bool use_temporaries = false;
- //
- // FIXME! We need a way to "probe" if the process can
- // just use `dup' to propagate the result
- //
IAssignMethod am = (IAssignMethod) target;
-
- if (this is CompoundAssign)
- am.CacheTemporaries (ec);
-
- if (!is_statement)
- use_temporaries = true;
Expression temp_source;
if (embedded != null) {
}
} else
temp_source = source;
-
- if (use_temporaries){
- //
- // Doing this for every path is too expensive
- // I wonder if we can work around this and have a less
- // expensive path
- //
- LocalTemporary tempo;
-
- tempo = new LocalTemporary (ec, source.Type);
-
- temp_source.Emit (ec);
- tempo.Store (ec);
- am.EmitAssign (ec, tempo);
- if (!is_statement)
- tempo.Emit (ec);
-
- tempo.Release (ec);
- } else {
- am.EmitAssign (ec, temp_source);
- }
+
+ am.EmitAssign (ec, temp_source, !is_statement, this is CompoundAssign);
if (embedded != null) {
if (temp != null)
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