Add InlineReturnTransform

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -71,6 +71,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				new SplitVariables(),
 				new ILInlining(),
 				new DetectPinnedRegions(), // must run after inlining but before non-critical control flow transforms
+				new InlineReturnTransform(),
 				new YieldReturnDecompiler(), // must run after inlining but before loop detection
 				new AsyncAwaitDecompiler(),  // must run after inlining but before loop detection
 				new DetectCatchWhenConditionBlocks(), // must run after inlining but before loop detection

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -273,6 +273,7 @@
     <Compile Include="DotNetCore\UnresolvedAssemblyNameReference.cs" />
     <Compile Include="IL\Instructions\StringToInt.cs" />
     <Compile Include="IL\Instructions\UsingInstruction.cs" />
+    <Compile Include="IL\Transforms\InlineReturnTransform.cs" />
     <Compile Include="IL\Transforms\SwitchOnStringTransform.cs" />
     <Compile Include="IL\Transforms\UsingTransform.cs" />
     <Compile Include="IL\ControlFlow\AsyncAwaitDecompiler.cs" />

ICSharpCode.Decompiler/IL/Transforms/InlineReturnTransform.cs

@@ -0,0 +1,83 @@
+// Copyright (c) 2017 Siegfried Pammer
+// 
+// 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.Collections.Generic;
+using System.Linq;
+
+namespace ICSharpCode.Decompiler.IL.Transforms
+{
+	/// <summary>
+	/// This transform duplicates return blocks if they return a local variable that was assigned right before thie return.
+	/// </summary>
+	class InlineReturnTransform : IILTransform
+	{
+		public void Run(ILFunction function, ILTransformContext context)
+		{
+			var instructionsToModify = new List<(BlockContainer, Block, Branch)>();
+			var possibleReturnVars = new Queue<(ILVariable, Block)>();
+			var tempList = new List<(BlockContainer, Block, Branch)>();
+
+			foreach (var leave in function.Descendants.OfType<Leave>()) {
+				if (!(leave.Parent is Block b && b.Instructions.Count == 1))
+					continue;
+				if (!leave.Value.MatchLdLoc(out var returnVar) || returnVar.Kind != VariableKind.Local)
+					continue;
+				possibleReturnVars.Enqueue((returnVar, b));
+			}
+
+			while (possibleReturnVars.Count > 0) {
+				var (returnVar, leaveBlock) = possibleReturnVars.Dequeue();
+				bool transform = true;
+				foreach (StLoc store in returnVar.StoreInstructions.OfType<StLoc>()) {
+					if (!(store.Parent is Block storeBlock)) {
+						transform = false;
+						break;
+					} 
+					if (store.ChildIndex + 2 != storeBlock.Instructions.Count) {
+						transform = false;
+						break;
+					}
+					if (!(storeBlock.Instructions[store.ChildIndex + 1] is Branch br)) {
+						transform = false;
+						break;
+					}
+					if (br.TargetBlock != leaveBlock) {
+						transform = false;
+						break;
+					}
+					var targetBlockContainer = BlockContainer.FindClosestContainer(store);
+					if (targetBlockContainer == null) {
+						transform = false;
+						break;
+					}
+					tempList.Add((targetBlockContainer, leaveBlock, br));
+				}
+				if (transform)
+					instructionsToModify.AddRange(tempList);
+				tempList.Clear();
+			}
+
+			foreach (var (container, block, br) in instructionsToModify) {
+				var newBlock = (Block)block.Clone();
+				container.Blocks.Add(newBlock);
+				br.TargetBlock = newBlock;
+			}
+		}
+	}
+}