From 5adc88672a91b0ccc5af2d192fc79446ce868de9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Srbeck=C3=BD?= <dsrbecky@gmail.com>
Date: Fri, 28 Mar 2008 22:11:13 +0000
Subject: [PATCH] Use the new representation to handle 'dup' instruction
 better. The outputted code is now just 'count++;'.  This access to field
 previously involved a temporary variable.

---
 bin/Debug/output.cs                 | 14 +++++++-------
 src/ByteCodeExpression.cs           | 25 +++++++++++++++++++++++++
 src/ByteCodeExpressionCollection.cs | 24 +++++++++++++++++++++---
 3 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/bin/Debug/output.cs b/bin/Debug/output.cs
index 9241f0da0..8e335cf7a 100644
--- a/bin/Debug/output.cs
+++ b/bin/Debug/output.cs
@@ -162,27 +162,27 @@ namespace Reversi
                         }
                     }
                     if (squares[i, j] == Black) {
-                        expr122.blackCount = blackCount + 1;
+                        blackCount++;
                         if (flag2) {
-                            expr134.blackFrontierCount = blackFrontierCount + 1;
+                            blackFrontierCount++;
                         }
                         if (safeDiscs[i, j]) {
-                            expr151.blackSafeCount = blackSafeCount + 1;
+                            blackSafeCount++;
                         }
                     } else {
                         if (squares[i, j] == White) {
-                            expr175.whiteCount = whiteCount + 1;
+                            whiteCount++;
                             if (flag2) {
-                                expr187.whiteFrontierCount = whiteFrontierCount + 1;
+                                whiteFrontierCount++;
                             }
                             if (safeDiscs[i, j]) {
-                                expr1A4.whiteSafeCount = whiteSafeCount + 1;
+                                whiteSafeCount++;
                                 goto BasicBlock_327;
                             } else {
                                 goto BasicBlock_327;
                             }
                         }
-                        expr1B4.emptyCount = emptyCount + 1;
+                        emptyCount++;
                     }
                     BasicBlock_327:
                 }
diff --git a/src/ByteCodeExpression.cs b/src/ByteCodeExpression.cs
index 8a926e0f5..7c2bee6d5 100644
--- a/src/ByteCodeExpression.cs
+++ b/src/ByteCodeExpression.cs
@@ -108,5 +108,30 @@ namespace Decompiler
 		{
 			return string.Format("[ByteCodeExpression OpCode={0}]", this.opCode);
 		}
+		
+		public ByteCodeExpression Clone()
+		{
+			ByteCodeExpression clone = (ByteCodeExpression)this.MemberwiseClone();
+			clone.branchTarget = null;
+			clone.branchesHere = new List<ByteCodeExpression>();
+			return clone;
+		}
+		
+		public bool IsConstant()
+		{
+			if (!IsOpCodeConstant()) return false;
+			foreach(ByteCodeExpression arg in this.Arguments) {
+				if (!arg.IsConstant()) return false;
+			}
+			return true;
+		}
+		
+		bool IsOpCodeConstant()
+		{
+			switch(this.OpCode.Code) {
+				case Code.Ldarg: return true;
+				default: return false;
+			}
+		}
 	}
 }
diff --git a/src/ByteCodeExpressionCollection.cs b/src/ByteCodeExpressionCollection.cs
index 904369db9..7d3b0eb5a 100644
--- a/src/ByteCodeExpressionCollection.cs
+++ b/src/ByteCodeExpressionCollection.cs
@@ -21,7 +21,7 @@ namespace Decompiler
 					string name = string.Format("expr{0:X2}", byteCode.Offset);
 					ByteCodeExpression stExpr = ByteCodeExpression.Stloc(name);
 					stExpr.Arguments.Add(newExpr);
-					stExpr.IsSSASR = true;
+					stExpr.IsSSASR = byteCode.PushCount == 1;
 					newExpr = stExpr;
 				}
 				
@@ -38,16 +38,34 @@ namespace Decompiler
 			}
 		}
 		
+		Dictionary<ByteCodeExpression, object> alreadyDuplicated = new Dictionary<ByteCodeExpression, object>();
+		
 		public void Optimize()
 		{
-			// Try to in-line stloc into following expression
-			
 			for(int i = 0; i < this.Count - 1; i++) {
 				if (i < 0) continue;
 				
 				ByteCodeExpression expr = this[i];
 				ByteCodeExpression nextExpr = this[i + 1];
 				
+				// Duplicate 'dup' expressions
+				
+				if (expr.OpCode.Code == Code.Stloc &&
+				    expr.Arguments[0].OpCode.Code == Code.Dup &&
+				    expr.Arguments[0].Arguments[0].IsConstant() &&
+				    !alreadyDuplicated.ContainsKey(expr))
+				{
+					Options.NotifyCollapsingExpression();
+					this.Insert(i + 1, expr.Clone());
+					this[i].IsSSASR = true;
+					this[i + 1].IsSSASR = true;
+					alreadyDuplicated.Add(this[i], null);
+					alreadyDuplicated.Add(this[i + 1], null);
+					continue;
+				}
+				
+				// Try to in-line stloc into following expression
+				
 				if (expr.OpCode.Code == Code.Stloc &&
 				    expr.IsSSASR &&
 				    !nextExpr.IsBranchTarget) {