From 0cf43014897b3fe735c720edb74c82445a5ee96d Mon Sep 17 00:00:00 2001
From: Frank Laub <frank.laub@gmail.com>
Date: Mon, 15 Mar 2010 13:42:59 -0700
Subject: [PATCH] OptmizeReturn in order to replace gotos to a single return
 with a duplicate return for each branch

---
 .../Core/ControlFlowGraph.cs                  | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/src/DotWeb.Decompiler/Core/ControlFlowGraph.cs b/src/DotWeb.Decompiler/Core/ControlFlowGraph.cs
index 8fc5980..98c4663 100644
--- a/src/DotWeb.Decompiler/Core/ControlFlowGraph.cs
+++ b/src/DotWeb.Decompiler/Core/ControlFlowGraph.cs
@@ -33,6 +33,7 @@ public ControlFlowGraph()
 
 		public void Structure() {
 			CompoundConditionals();
+			OptimizeReturn();
 			StructureLoops();
 			StructureConditionals();
 			StructureExceptions();
@@ -329,5 +330,32 @@ public ControlFlowGraph()
 				}
 			}
 		}
+
+		public void OptimizeReturn() {
+			var returns = this.Nodes.Cast<BasicBlock>().Where(x => x.FlowControl == FlowControl.Return);
+			if (returns.Count() == 1) {
+				var exit = returns.Single();
+				if (exit.Statements.Count == 1) {
+					var returnStmt = exit.Statements.Single() as CodeReturnStatement;
+					if (returnStmt != null) {
+						var variableRef = returnStmt.Expression as CodeVariableReference;
+						if (variableRef != null) {
+							foreach (BasicBlock pred in exit.Predecessors) {
+								pred.Successors.Remove(exit);
+								var copy = new CodeReturnStatement {
+									Expression = returnStmt.Expression
+								};
+								pred.Statements.Add(copy);
+								if (pred.LastInstruction.OpCode.FlowControl == FlowControl.Branch) {
+									pred.Instructions.Remove(pred.LastInstruction);
+								}
+								pred.Instructions.AddRange(exit.Instructions);
+							}
+							this.Nodes.Remove(exit);
+						}
+					}
+				}
+			}
+		}
 	}
 }