Add support for MCS 2.6.4 pinned region with string variable

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -1,14 +1,14 @@
 // Copyright (c) AlphaSierraPapa for the SharpDevelop Team
-// 
+//
 // 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
@@ -269,6 +269,12 @@ public async Task EmptyBodies()
 			await Run();
 		}
 
+		[Test]
+		public async Task MonoFixed()
+		{
+			await Run();
+		}
+
 		async Task Run([CallerMemberName] string testName = null, DecompilerSettings settings = null,
 			AssemblerOptions assemblerOptions = AssemblerOptions.Library)
 		{

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/MonoFixed.cs

@@ -0,0 +1,20 @@
+using System;
+
+public class MonoFixed
+{
+	public unsafe void FixMultipleStrings(string text)
+	{
+		fixed (char* ptr = text)
+		{
+			fixed (char* ptr2 = Environment.UserName)
+			{
+				fixed (char* ptr3 = text)
+				{
+					*ptr = 'c';
+					*ptr2 = 'd';
+					*ptr3 = 'e';
+				}
+			}
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/MonoFixed.il

@@ -0,0 +1,74 @@
+.assembly extern mscorlib
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
+  .ver 4:0:0:0
+}
+.assembly MonoFixed
+{
+  .ver 1:0:0:0
+}
+
+.module MonoFixed.exe
+.imagebase 0x00400000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003 // WindowsCui
+.corflags 0x00000001 // ILOnly
+.custom instance void [mscorlib]System.Security.UnverifiableCodeAttribute::.ctor() = (
+	01 00 00 00
+)
+
+.class public auto ansi beforefieldinit MonoFixed
+	   extends [mscorlib]System.Object
+{
+  .method public hidebysig instance void FixMultipleStrings (string text) cil managed
+	{
+		.maxstack 7
+		.locals init (
+			[0] char* pinned,
+			[1] char* pinned,
+			[2] char* pinned,
+			[3] string pinned,
+			[4] string pinned,
+			[5] string pinned
+		)
+
+		IL_0000: ldarg.1
+		IL_0001: stloc.3
+		IL_0002: ldloc.3
+		IL_0003: conv.i
+		IL_0004: call int32 [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::get_OffsetToStringData()
+		IL_0009: add
+		IL_000a: stloc.0
+		IL_000b: call string [mscorlib]System.Environment::get_UserName()
+		IL_0010: stloc.s 4
+		IL_0012: ldloc.s 4
+		IL_0014: conv.i
+		IL_0015: call int32 [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::get_OffsetToStringData()
+		IL_001a: add
+		IL_001b: stloc.1
+		IL_001c: ldarg.1
+		IL_001d: stloc.s 5
+		IL_001f: ldloc.s 5
+		IL_0021: conv.i
+		IL_0022: call int32 [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::get_OffsetToStringData()
+		IL_0027: add
+		IL_0028: stloc.2
+		IL_0029: ldloc.0
+		IL_002a: ldc.i4.s 99
+		IL_002c: stind.i2
+		IL_002d: ldloc.1
+		IL_002e: ldc.i4.s 100
+		IL_0030: stind.i2
+		IL_0031: ldloc.2
+		IL_0032: ldc.i4.s 101
+		IL_0034: stind.i2
+		IL_0035: ldnull
+		IL_0036: stloc.3
+		IL_0037: ldnull
+		IL_0038: stloc.s 4
+		IL_003a: ldnull
+		IL_003b: stloc.s 5
+		IL_003d: ret
+	}
+}

ICSharpCode.Decompiler/IL/ControlFlow/DetectPinnedRegions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) 2016 Daniel Grunwald
+// Copyright (c) 2016 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
@@ -878,28 +878,44 @@ void HandleStringToPointer(PinnedRegion pinnedRegion)
 				}
 				return;
 			}
-			if (body.EntryPoint.Instructions.Count != 3)
-			{
-				return;
-			}
-
 			if (nativeVar.Type.GetStackType() != StackType.I)
 				return;
-			if (!initInst.UnwrapConv(ConversionKind.StopGCTracking).MatchLdLoc(pinnedRegion.Variable))
-				return;
-			if (!IsBranchOnNull(body.EntryPoint.Instructions[1], nativeVar, out Block targetBlock))
-				return;
-			if (!body.EntryPoint.Instructions[2].MatchBranch(out Block adjustOffsetToStringData))
-				return;
-			if (!(adjustOffsetToStringData.Parent == body && adjustOffsetToStringData.IncomingEdgeCount == 1
-					&& IsOffsetToStringDataBlock(adjustOffsetToStringData, nativeVar, targetBlock)))
+
+			Block targetBlock;
+			Block adjustOffsetToStringData = null;
+			if (body.EntryPoint.Instructions.Count == 2)
+			{
+				if (!initInst.MatchBinaryNumericInstruction(BinaryNumericOperator.Add, out ILInstruction left, out ILInstruction right))
+					return;
+				if (!left.UnwrapConv(ConversionKind.StopGCTracking).MatchLdLoc(pinnedRegion.Variable))
+					return;
+				if (!IsOffsetToStringDataCall(right))
+					return;
+				if (!body.EntryPoint.Instructions[1].MatchBranch(out targetBlock))
+					return;
+			}
+			else if (body.EntryPoint.Instructions.Count == 3)
+			{
+				if (!initInst.UnwrapConv(ConversionKind.StopGCTracking).MatchLdLoc(pinnedRegion.Variable))
+					return;
+				if (!IsBranchOnNull(body.EntryPoint.Instructions[1], nativeVar, out targetBlock))
+					return;
+				if (!body.EntryPoint.Instructions[2].MatchBranch(out adjustOffsetToStringData))
+					return;
+				if (!(adjustOffsetToStringData.Parent == body && adjustOffsetToStringData.IncomingEdgeCount == 1
+						&& IsOffsetToStringDataBlock(adjustOffsetToStringData, nativeVar, targetBlock)))
+					return;
+			}
+			else
 				return;
+
 			context.Step("Handle pinned string (with adjustOffsetToStringData)", pinnedRegion);
 			if (targetBlock.Parent == body)
 			{
 				// remove old entry point
 				body.Blocks.RemoveAt(0);
-				body.Blocks.RemoveAt(adjustOffsetToStringData.ChildIndex);
+				if (adjustOffsetToStringData is not null)
+					body.Blocks.RemoveAt(adjustOffsetToStringData.ChildIndex);
 				// make targetBlock the new entry point
 				body.Blocks.RemoveAt(targetBlock.ChildIndex);
 				body.Blocks.Insert(0, targetBlock);