implement basic support for custom short circuit operators + unit test; fixes #193

ICSharpCode.Decompiler/ILAst/ILAstOptimizer.cs

@@ -44,6 +44,7 @@ namespace ICSharpCode.Decompiler.ILAst
 		JoinBasicBlocks,
 		TransformDecimalCtorToConstant,
 		SimplifyLdObjAndStObj,
+		SimplifyCustomShortCircuit,
 		TransformArrayInitializers,
 		TransformObjectInitializers,
 		MakeAssignmentExpression,
@@ -136,6 +137,9 @@ namespace ICSharpCode.Decompiler.ILAst
 					if (abortBeforeStep == ILAstOptimizationStep.SimplifyLdObjAndStObj) return;
 					modified |= block.RunOptimization(SimplifyLdObjAndStObj);
 					
+					if (abortBeforeStep == ILAstOptimizationStep.SimplifyCustomShortCircuit) return;
+					modified |= block.RunOptimization(new SimpleControlFlow(context, method).SimplifyCustomShortCircuit);
+					
 					if (abortBeforeStep == ILAstOptimizationStep.TransformArrayInitializers) return;
 					modified |= block.RunOptimization(TransformArrayInitializers);
 					

ICSharpCode.Decompiler/ILAst/SimpleControlFlow.cs

@@ -165,7 +165,7 @@ namespace ICSharpCode.Decompiler.ILAst
 			ILBasicBlock rightBB;
 			ILExpression rightExpr;
 			if (head.Body.Count >= 3 &&
-				head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out v, out leftExpr) &&
+			    head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out v, out leftExpr) &&
 			    leftExpr.Match(ILCode.Ldloc, out leftVar) &&
 			    head.MatchLastAndBr(ILCode.Brtrue, out endBBLabel, out leftExpr2, out rightBBLabel) &&
 			    leftExpr2.MatchLdloc(leftVar) &&
@@ -234,6 +234,84 @@ namespace ICSharpCode.Decompiler.ILAst
 			return false;
 		}
 		
+		public bool SimplifyCustomShortCircuit(List<ILNode> body, ILBasicBlock head, int pos)
+		{
+			Debug.Assert(body.Contains(head));
+			
+			// --- looking for the following pattern ---
+			// stloc(targetVar, leftVar)
+			// brtrue(exitLabel, call(op_False, leftVar)
+			// br(followingBlock)
+			//
+			// FollowingBlock:
+			// stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
+			// br(exitLabel)
+			// ---
+			
+			if (head.Body.Count < 3)
+				return false;
+			
+			// looking for:
+			// stloc(targetVar, leftVar)
+			ILVariable targetVar;
+			ILExpression targetVarInitExpr;
+			if (!head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out targetVar, out targetVarInitExpr))
+				return false;
+			
+			// looking for:
+			// brtrue(exitLabel, call(op_False, leftVar)
+			// br(followingBlock)
+			ILExpression callExpr;
+			ILLabel exitLabel;
+			ILLabel followingBlock;
+			if(!head.MatchLastAndBr(ILCode.Brtrue, out exitLabel, out callExpr, out followingBlock))
+				return false;
+			
+			MethodDefinition opFalse;
+			ILExpression leftVar;
+			if (!callExpr.Match(ILCode.Call, out opFalse, out leftVar))
+				return false;
+			
+			if (!leftVar.MatchLdloc(targetVarInitExpr.Operand as ILVariable))
+				return false;
+			
+			ILBasicBlock followingBasicBlock = labelToBasicBlock[followingBlock];
+			
+			// FollowingBlock:
+			// stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
+			// br(exitLabel)
+			ILVariable _targetVar;
+			ILExpression opBitwiseCallExpr;
+			ILLabel _exitLabel;
+			if (!followingBasicBlock.MatchSingleAndBr(ILCode.Stloc, out _targetVar, out opBitwiseCallExpr, out _exitLabel))
+				return false;
+			
+			if (_targetVar != targetVar)
+				return false;
+			
+			MethodDefinition opBitwise;
+			ILExpression leftVarExpression;
+			ILExpression rightExpression;
+			if (!opBitwiseCallExpr.Match(ILCode.Call, out opBitwise, out leftVarExpression, out rightExpression))
+				return false;
+			
+			if (!leftVar.MatchLdloc(leftVarExpression.Operand as ILVariable))
+				return false;
+			
+			// insert:
+			// stloc(targetVar, LogicAnd(C::op_BitwiseAnd, leftVar, rightExpression)
+			// br(exitLabel)
+			ILExpression shortCircuitExpr = MakeLeftAssociativeShortCircuit(opBitwise.Name == "op_BitwiseAnd" ? ILCode.LogicAnd : ILCode.LogicOr, leftVar, rightExpression);
+			shortCircuitExpr.Operand = opBitwise;
+			
+			head.Body.RemoveTail(ILCode.Stloc, ILCode.Brtrue, ILCode.Br);
+			head.Body.Add(new ILExpression(ILCode.Stloc, targetVar, shortCircuitExpr));
+			head.Body.Add(new ILExpression(ILCode.Br, exitLabel));
+			body.Remove(followingBasicBlock);
+			
+			return true;
+		}
+		
 		ILExpression MakeLeftAssociativeShortCircuit(ILCode code, ILExpression left, ILExpression right)
 		{
 			// Assuming that the inputs are already left associative

ICSharpCode.Decompiler/ILAst/TypeAnalysis.cs

@@ -267,6 +267,10 @@ namespace ICSharpCode.Decompiler.ILAst
 					return typeSystem.Boolean;
 				case ILCode.LogicAnd:
 				case ILCode.LogicOr:
+					// if Operand is set the logic and/or expression is a custom operator
+					// we can deal with it the same as a normal invocation.
+					if (expr.Operand != null)
+						goto case ILCode.Call;
 					if (forceInferChildren) {
 						InferTypeForExpression(expr.Arguments[0], typeSystem.Boolean);
 						InferTypeForExpression(expr.Arguments[1], typeSystem.Boolean);

ICSharpCode.Decompiler/Tests/CustomShortCircuitOperators.cs

@@ -0,0 +1,43 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
+
+using System;
+
+public static class CustomShortCircuitOperators
+{
+	private class B
+	{
+		public static bool operator true(CustomShortCircuitOperators.B x)
+		{
+			return true;
+		}
+
+		public static bool operator false(CustomShortCircuitOperators.B x)
+		{
+			return false;
+		}
+	}
+
+	private class C : CustomShortCircuitOperators.B
+	{
+		public static CustomShortCircuitOperators.C operator &(CustomShortCircuitOperators.C x, CustomShortCircuitOperators.C y)
+		{
+			return null;
+		}
+		
+		public static CustomShortCircuitOperators.C operator |(CustomShortCircuitOperators.C x, CustomShortCircuitOperators.C y)
+		{
+			return null;
+		}
+
+		private static void Main()
+		{
+			CustomShortCircuitOperators.C c = new CustomShortCircuitOperators.C();
+			CustomShortCircuitOperators.C c2 = new CustomShortCircuitOperators.C();
+			CustomShortCircuitOperators.C c3 = c && c2;
+			CustomShortCircuitOperators.C c4 = c || c2;
+			Console.WriteLine(c3.ToString());
+			Console.WriteLine(c4.ToString());
+		}
+	}
+}

ICSharpCode.Decompiler/Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -57,6 +57,7 @@
   <ItemGroup>
     <Compile Include="CallOverloadedMethod.cs" />
     <Compile Include="CheckedUnchecked.cs" />
+    <Compile Include="CustomShortCircuitOperators.cs" />
     <Compile Include="Helpers\CodeAssert.cs" />
     <Compile Include="IncrementDecrement.cs" />
     <Compile Include="PInvoke.cs" />

ICSharpCode.Decompiler/Tests/TestRunner.cs

@@ -49,6 +49,12 @@ namespace ICSharpCode.Decompiler.Tests
 			TestFile(@"..\..\Tests\Generics.cs");
 		}
 		
+		[Test]
+		public void CustomShortCircuitOperators()
+		{
+			TestFile(@"..\..\Tests\CustomShortCircuitOperators.cs");
+		}
+		
 		[Test]
 		public void IncrementDecrement()
 		{