diff --git a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
index 0233473ae..13afba293 100644
--- a/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
+++ b/ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs
@@ -50,6 +50,7 @@ namespace ICSharpCode.Decompiler.CSharp
new IntroduceExitPoints(),
new ConditionDetection(),
new ILInlining(),
+ new CopyPropagation(),
new InlineCompilerGeneratedVariables(),
new TransformingVisitor(),
new ExpressionTransforms(),
diff --git a/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj b/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
index 0771f4856..01f563017 100644
--- a/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
+++ b/ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj
@@ -113,6 +113,7 @@
+
diff --git a/ICSharpCode.Decompiler/IL/Transforms/CopyPropagation.cs b/ICSharpCode.Decompiler/IL/Transforms/CopyPropagation.cs
new file mode 100644
index 000000000..087fcd4b1
--- /dev/null
+++ b/ICSharpCode.Decompiler/IL/Transforms/CopyPropagation.cs
@@ -0,0 +1,103 @@
+// Copyright (c) 2011-2015 Daniel Grunwald
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Linq;
+
+namespace ICSharpCode.Decompiler.IL
+{
+ ///
+ /// Runs a very simple form of copy propagation.
+ /// Copy propagation is used in two cases:
+ /// 1) assignments from arguments to local variables
+ /// If the target variable is assigned to only once (so always is that argument) and the argument is never changed (no ldarga/starg),
+ /// then we can replace the variable with the argument.
+ /// 2) assignments of address-loading instructions to local variables
+ ///
+ public class CopyPropagation : IILTransform
+ {
+ public void Run(ILFunction function, ILTransformContext context)
+ {
+ foreach (var block in function.Descendants.OfType()) {
+ for (int i = 0; i < block.Instructions.Count; i++) {
+ ILVariable v;
+ ILInstruction copiedExpr;
+ if (block.Instructions[i].MatchStLoc(out v, out copiedExpr)) {
+ if (v.StoreCount == 1 && v.AddressCount == 0 && v.Kind != VariableKind.Parameter && CanPerformCopyPropagation(v, copiedExpr)) {
+ // un-inline the arguments of the ldArg instruction
+ ILVariable[] uninlinedArgs = new ILVariable[copiedExpr.Children.Count];
+ for (int j = 0; j < uninlinedArgs.Length; j++) {
+ var arg = copiedExpr.Children[j];
+ var type = context.TypeSystem.Compilation.FindType(arg.ResultType.ToKnownTypeCode());
+ uninlinedArgs[j] = new ILVariable(VariableKind.StackSlot, type, arg.ResultType, arg.ILRange.Start) {
+ Name = "C_" + arg.ILRange.Start
+ };
+ block.Instructions.Insert(i++, new StLoc(uninlinedArgs[j], arg));
+ }
+ // perform copy propagation:
+ foreach (var expr in function.Descendants) {
+ if (expr.MatchLdLoc(v)) {
+ var clone = copiedExpr.Clone();
+ for (int j = 0; j < uninlinedArgs.Length; j++) {
+ clone.Children[j].ReplaceWith(new LdLoc(uninlinedArgs[j]));
+ }
+ expr.ReplaceWith(clone);
+ }
+ }
+ block.Instructions.RemoveAt(i);
+ int c = new ILInlining().InlineInto(block, i, aggressive: false);
+ i -= uninlinedArgs.Length + c + 1;
+ }
+ }
+ }
+ }
+ }
+
+ static bool CanPerformCopyPropagation(ILVariable target, ILInstruction value)
+ {
+ switch (value.OpCode) {
+ case OpCode.LdLoca:
+ case OpCode.LdElema:
+ case OpCode.LdFlda:
+ case OpCode.LdsFlda:
+ // All address-loading instructions always return the same value for a given operand/argument combination,
+ // so they can be safely copied.
+ return true;
+ case OpCode.LdLoc:
+ var v = ((LdLoc)value).Variable;
+ switch (v.Kind) {
+ case VariableKind.This:
+ case VariableKind.Parameter:
+ // Parameters can be copied only if they aren't assigned to (directly or indirectly via ldarga)
+ // note: the initialization by the caller is the first store -> StoreCount must be 1
+ return v.StoreCount == 1 && v.AddressCount == 0;
+ case VariableKind.StackSlot:
+ // Variables are be copied only if both they and the target copy variable are generated,
+ // and if the variable has only a single assignment
+ return v.StoreCount == 1 && v.AddressCount == 0 && v.Kind == VariableKind.StackSlot && target.Kind == VariableKind.StackSlot;
+ default:
+ return false;
+ }
+ default:
+ return false;
+ }
+ }
+ }
+}
+
+