ikvm-fork/runtime/CodeEmitter.cs

/*
  Copyright (C) 2002, 2004, 2005, 2006, 2008, 2009 Jeroen Frijters

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Jeroen Frijters
  jeroen@frijters.net
  
*/
using System;
using System.Collections.Generic;
#if STATIC_COMPILER
using IKVM.Reflection;
using IKVM.Reflection.Emit;
using Type = IKVM.Reflection.Type;
#else
using System.Reflection;
using System.Reflection.Emit;
#endif
using System.Runtime.InteropServices;
using System.Diagnostics.SymbolStore;
using System.Diagnostics;

namespace IKVM.Internal
{
	class CodeEmitterLabel
	{
		private Label label;
		private int offset = -1;

		internal CodeEmitterLabel(Label label)
		{
			this.label = label;
		}

		internal Label Label
		{
			get
			{
				return label;
			}
		}

		internal int Offset
		{
			get
			{
				return offset;
			}
			set
			{
				offset = value;
			}
		}
	}

	sealed class CodeEmitter
	{
		private static readonly MethodInfo objectToString = Types.Object.GetMethod("ToString", BindingFlags.Public | BindingFlags.Instance, null, Type.EmptyTypes, null);
		private static readonly MethodInfo verboseCastFailure = JVM.SafeGetEnvironmentVariable("IKVM_VERBOSE_CAST") == null ? null : ByteCodeHelperMethods.VerboseCastFailure;
		private ILGenerator ilgen_real;
#if !STATIC_COMPILER
		private int offset;
#endif
		private Stack<bool> exceptionStack = new Stack<bool>();
		private bool inFinally;
#if STATIC_COMPILER
		private IKVM.Attributes.LineNumberTableAttribute.LineNumberWriter linenums;
#endif // STATIC_COMPILER
		private Expr[] stackArray = new Expr[8];
		private int topOfStack;
		private CodeEmitterLabel lazyBranch;
		private LocalBuilder[] tempLocals = new LocalBuilder[32];
#if LABELCHECK
		private Dictionary<CodeEmitterLabel, System.Diagnostics.StackFrame> labels = new Dictionary<CodeEmitterLabel, System.Diagnostics.StackFrame>();
#endif

		internal static CodeEmitter Create(MethodBuilder mb)
		{
			return new CodeEmitter(mb.GetILGenerator());
		}

		internal static CodeEmitter Create(ConstructorBuilder cb)
		{
			return new CodeEmitter(cb.GetILGenerator());
		}

#if !STATIC_COMPILER
		internal static CodeEmitter Create(DynamicMethod dm)
		{
			return new CodeEmitter(dm.GetILGenerator());
		}
#endif

		private CodeEmitter(ILGenerator ilgen)
		{
#if STATIC_COMPILER
			ilgen.__CleverExceptionBlockAssistance();
#endif
			this.ilgen_real = ilgen;
		}

		private void PushStack(Expr expr)
		{
			Debug.Assert(expr != null);
			if (topOfStack == stackArray.Length)
			{
				Array.Resize(ref stackArray, stackArray.Length * 2);
			}
			stackArray[topOfStack++] = expr;
		}

		private void PushStackMayBeNull(Expr expr)
		{
			if (expr != null)
			{
				PushStack(expr);
			}
		}

		private Expr PopStack()
		{
			if (topOfStack == 0)
			{
				return null;
			}
			return stackArray[--topOfStack];
		}

		private Expr PeekStack()
		{
			if (topOfStack == 0)
			{
				return null;
			}
			return stackArray[topOfStack - 1];
		}

		internal LocalBuilder UnsafeAllocTempLocal(Type type)
		{
			int free = -1;
			for (int i = 0; i < tempLocals.Length; i++)
			{
				LocalBuilder lb = tempLocals[i];
				if (lb == null)
				{
					if (free == -1)
					{
						free = i;
					}
				}
				else if (lb.LocalType == type)
				{
					return lb;
				}
			}
			LocalBuilder lb1 = DeclareLocal(type);
			if (free != -1)
			{
				tempLocals[free] = lb1;
			}
			return lb1;
		}

		internal LocalBuilder AllocTempLocal(Type type)
		{
			for (int i = 0; i < tempLocals.Length; i++)
			{
				LocalBuilder lb = tempLocals[i];
				if (lb != null && lb.LocalType == type)
				{
					tempLocals[i] = null;
					return lb;
				}
			}
			return DeclareLocal(type);
		}

		internal void ReleaseTempLocal(LocalBuilder lb)
		{
			for (int i = 0; i < tempLocals.Length; i++)
			{
				if (tempLocals[i] == null)
				{
					tempLocals[i] = lb;
					break;
				}
			}
		}

		internal bool IsStackEmpty
		{
			get
			{
				return topOfStack == 0;
			}
		}

		internal int GetILOffset()
		{
			LazyGen();
#if STATIC_COMPILER
			return ilgen_real.ILOffset;
#else
			return offset;
#endif
		}

		internal void BeginCatchBlock(Type exceptionType)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += 5;
#endif
			ilgen_real.BeginCatchBlock(exceptionType);
		}

		internal Label BeginExceptionBlock()
		{
			LazyGen();
			exceptionStack.Push(inFinally);
			inFinally = false;
			return ilgen_real.BeginExceptionBlock();
		}

		internal void BeginFaultBlock()
		{
			LazyGen();
			inFinally = true;
#if !STATIC_COMPILER
			offset += 5;
#endif
			ilgen_real.BeginFaultBlock();
		}

		internal void BeginFinallyBlock()
		{
			LazyGen();
			inFinally = true;
#if !STATIC_COMPILER
			offset += 5;
#endif
			ilgen_real.BeginFinallyBlock();
		}

		internal void BeginScope()
		{
			LazyGen();
			ilgen_real.BeginScope();
		}

		internal LocalBuilder DeclareLocal(Type localType)
		{
			return ilgen_real.DeclareLocal(localType);
		}

		internal CodeEmitterLabel DefineLabel()
		{
			CodeEmitterLabel label = new CodeEmitterLabel(ilgen_real.DefineLabel());
#if LABELCHECK
			labels.Add(label, new System.Diagnostics.StackFrame(1, true));
#endif
			return label;
		}

		internal void Emit(OpCode opcode)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size;
#endif
			ilgen_real.Emit(opcode);
		}

		internal void Emit(OpCode opcode, byte arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 1;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, ConstructorInfo con)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, con);
		}

		internal void Emit(OpCode opcode, double arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 8;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, FieldInfo field)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, field);
		}

		internal void Emit(OpCode opcode, short arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 2;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, int arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, long arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 8;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, CodeEmitterLabel label)
		{
			int currOffset = GetILOffset();
			if(label.Offset == -1)
			{
				if(opcode.Value == OpCodes.Br.Value)
				{
					lazyBranch = label;
					return;
				}
			}
			else if(currOffset - label.Offset < 126)
			{
				if(opcode.Value == OpCodes.Brtrue.Value)
				{
					opcode = OpCodes.Brtrue_S;
				}
				else if(opcode.Value == OpCodes.Brfalse.Value)
				{
					opcode = OpCodes.Brfalse_S;
				}
				else if(opcode.Value == OpCodes.Br.Value)
				{
					opcode = OpCodes.Br_S;
				}
				else if(opcode.Value == OpCodes.Beq.Value)
				{
					opcode = OpCodes.Beq_S;
				}
				else if(opcode.Value == OpCodes.Bne_Un.Value)
				{
					opcode = OpCodes.Bne_Un_S;
				}
				else if(opcode.Value == OpCodes.Ble.Value)
				{
					opcode = OpCodes.Ble_S;
				}
				else if(opcode.Value == OpCodes.Blt.Value)
				{
					opcode = OpCodes.Blt_S;
				}
				else if(opcode.Value == OpCodes.Bge.Value)
				{
					opcode = OpCodes.Bge_S;
				}
				else if(opcode.Value == OpCodes.Bgt.Value)
				{
					opcode = OpCodes.Bgt_S;
				}
			}
#if !STATIC_COMPILER
			switch(opcode.OperandType)
			{
				case OperandType.InlineBrTarget:
					offset += opcode.Size + 4;
					break;
				case OperandType.ShortInlineBrTarget:
					offset += opcode.Size + 1;
					break;
				default:
					throw new NotImplementedException();
			}
#endif
			ilgen_real.Emit(opcode, label.Label);
		}

		internal void Emit(OpCode opcode, CodeEmitterLabel[] labels)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += 5 + labels.Length * 4;
#endif
			Label[] real = new Label[labels.Length];
			for(int i = 0; i < labels.Length; i++)
			{
				real[i] = labels[i].Label;
			}
			ilgen_real.Emit(opcode, real);
		}

		internal void Emit(OpCode opcode, LocalBuilder local)
		{
			LazyGen();
#if !STATIC_COMPILER
			int index = local.LocalIndex;
			if(index < 4 && opcode.Value != OpCodes.Ldloca.Value && opcode.Value != OpCodes.Ldloca_S.Value)
			{
				offset += 1;
			}
			else if(index < 256)
			{
				offset += 2;
			}
			else
			{
				offset += 4;
			}
#endif
			ilgen_real.Emit(opcode, local);
		}

		internal void Emit(OpCode opcode, MethodInfo meth)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, meth);
		}

		internal void Emit(OpCode opcode, sbyte arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 1;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, float arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, string arg)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, arg);
		}

		internal void Emit(OpCode opcode, Type cls)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += opcode.Size + 4;
#endif
			ilgen_real.Emit(opcode, cls);
		}

		internal void EmitCalli(OpCode opcode, CallingConvention unmanagedCallConv, Type returnType, Type[] parameterTypes)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += 5;
#endif
			ilgen_real.EmitCalli(opcode, unmanagedCallConv, returnType, parameterTypes);
		}

		internal void EmitWriteLine(string value)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += 10;
#endif
			ilgen_real.EmitWriteLine(value);
		}

		internal void EndExceptionBlockNoFallThrough()
		{
			EndExceptionBlock();
#if !STATIC_COMPILER
			// HACK to keep the verifier happy we need this bogus jump
			// (because of the bogus Leave that Ref.Emit ends the try block with)
			Emit(OpCodes.Br_S, (sbyte)-2);
#endif
		}

		internal void EndExceptionBlock()
		{
			LazyGen();
#if !STATIC_COMPILER
			if(inFinally)
			{
				offset += 1;
			}
			else
			{
				offset += 5;
			}
#endif
			inFinally = exceptionStack.Pop();
			ilgen_real.EndExceptionBlock();
		}

		internal void EndScope()
		{
			LazyGen();
			ilgen_real.EndScope();
		}

		internal void MarkLabel(CodeEmitterLabel loc)
		{
			if(lazyBranch == loc)
			{
				lazyBranch = null;
			}
			LazyGen();
#if LABELCHECK
			labels.Remove(loc);
#endif
			ilgen_real.MarkLabel(loc.Label);
			loc.Offset = GetILOffset();
		}

		internal void MarkSequencePoint(ISymbolDocumentWriter document, int startLine, int startColumn, int endLine, int endColumn)
		{
			LazyGen();
			ilgen_real.MarkSequencePoint(document, startLine, startColumn, endLine, endColumn);
		}

		internal void ThrowException(Type excType)
		{
			LazyGen();
#if !STATIC_COMPILER
			offset += 6;
#endif
			ilgen_real.ThrowException(excType);
		}

#if STATIC_COMPILER
		internal void SetLineNumber(ushort line)
		{
			if(linenums == null)
			{
				linenums = new IKVM.Attributes.LineNumberTableAttribute.LineNumberWriter(32);
			}
			linenums.AddMapping(GetILOffset(), line);
		}

		internal void EmitLineNumberTable(MethodBase mb)
		{
			if(linenums != null)
			{
				AttributeHelper.SetLineNumberTable(mb, linenums);
			}
		}
#endif // STATIC_COMPILER

		internal void EmitThrow(string dottedClassName)
		{
			TypeWrapper exception = ClassLoaderWrapper.GetBootstrapClassLoader().LoadClassByDottedName(dottedClassName);
			MethodWrapper mw = exception.GetMethodWrapper("<init>", "()V", false);
			mw.Link();
			mw.EmitNewobj(this);
			Emit(OpCodes.Throw);
		}

		internal void EmitThrow(string dottedClassName, string message)
		{
			TypeWrapper exception = ClassLoaderWrapper.GetBootstrapClassLoader().LoadClassByDottedName(dottedClassName);
			Emit(OpCodes.Ldstr, message);
			MethodWrapper mw = exception.GetMethodWrapper("<init>", "(Ljava.lang.String;)V", false);
			mw.Link();
			mw.EmitNewobj(this);
			Emit(OpCodes.Throw);
		}

		internal void EmitNullCheck()
		{
			// I think this is the most efficient way to generate a NullReferenceException if the reference is null
			Emit(OpCodes.Ldvirtftn, objectToString);
			Emit(OpCodes.Pop);
		}

		internal void EmitCastclass(Type type)
		{
			if (verboseCastFailure != null)
			{
				LocalBuilder lb = DeclareLocal(Types.Object);
				Emit(OpCodes.Stloc, lb);
				Emit(OpCodes.Ldloc, lb);
				Emit(OpCodes.Isinst, type);
				Emit(OpCodes.Dup);
				CodeEmitterLabel ok = DefineLabel();
				Emit(OpCodes.Brtrue_S, ok);
				Emit(OpCodes.Ldloc, lb);
				Emit(OpCodes.Brfalse_S, ok);	// handle null
				Emit(OpCodes.Ldtoken, type);
				Emit(OpCodes.Ldloc, lb);
				Emit(OpCodes.Call, verboseCastFailure);
				MarkLabel(ok);
			}
			else
			{
				Emit(OpCodes.Castclass, type);
			}
		}

		// This is basically the same as Castclass, except that it
		// throws an IncompatibleClassChangeError on failure.
		internal void EmitAssertType(Type type)
		{
			LocalBuilder lb = DeclareLocal(Types.Object);
			Emit(OpCodes.Stloc, lb);
			Emit(OpCodes.Ldloc, lb);
			Emit(OpCodes.Isinst, type);
			Emit(OpCodes.Dup);
			CodeEmitterLabel ok = DefineLabel();
			Emit(OpCodes.Brtrue_S, ok);
			Emit(OpCodes.Ldloc, lb);
			Emit(OpCodes.Brfalse_S, ok);	// handle null
			EmitThrow("java.lang.IncompatibleClassChangeError");
			MarkLabel(ok);
		}

		internal void LazyEmitPop()
		{
			Expr exp = PeekStack();
			if (exp == null || exp.HasSideEffect || exp.IsIncomplete)
			{
				Emit(OpCodes.Pop);
			}
			else
			{
				PopStack();
			}
		}

		internal void LazyEmitLoadClass(TypeWrapper type)
		{
			PushStack(new ClassLiteralExpr(type));
		}

		internal void LazyEmitBox(Type type)
		{
			PushStack(new BoxExpr(PopStack(), type));
		}

		internal void LazyEmitUnbox(Type type)
		{
			BoxExpr box = PeekStack() as BoxExpr;
			if(box != null)
			{
				PopStack();
				PushStack(new BoxUnboxExpr(box.Expr, type));
			}
			else
			{
				PushStack(new UnboxExpr(PopStack(), type));
			}
		}

		internal void LazyEmitLdobj(Type type)
		{
			BoxUnboxExpr boxunbox = PeekStack() as BoxUnboxExpr;
			if(boxunbox != null)
			{
				PopStack();
				// box/unbox+ldobj annihilate each other
				PushStackMayBeNull(boxunbox.Expr);
			}
			else
			{
				PushStack(new LdobjExpr(PopStack(), type));
			}
		}

		internal void LazyEmitUnboxSpecial(Type type)
		{
			BoxExpr box = PeekStack() as BoxExpr;
			if(box != null)
			{
				PopStack();
				// the unbox and lazy box cancel each other out
				PushStackMayBeNull(box.Expr);
			}
			else
			{
				// NOTE if the reference is null, we treat it as a default instance of the value type.
				Emit(OpCodes.Dup);
				CodeEmitterLabel label1 = DefineLabel();
				Emit(OpCodes.Brtrue_S, label1);
				Emit(OpCodes.Pop);
				Emit(OpCodes.Ldloc, DeclareLocal(type));
				CodeEmitterLabel label2 = DefineLabel();
				Emit(OpCodes.Br_S, label2);
				MarkLabel(label1);
				Emit(OpCodes.Unbox, type);
				Emit(OpCodes.Ldobj, type);
				MarkLabel(label2);
			}
		}

		internal void LazyEmitLdnull()
		{
			PushStack(new NullExpr());
		}

		internal void LazyEmitLdc_I4(int i)
		{
			PushStack(new ConstIntExpr(i));
		}

		internal void LazyEmitLdc_I8(long l)
		{
			PushStack(new ConstLongExpr(l));
		}

		internal void LazyEmitLdstr(string str)
		{
			PushStack(new ConstStringExpr(str));
		}

		internal void LazyEmit_idiv()
		{
			// we need to special case dividing by -1, because the CLR div instruction
			// throws an OverflowException when dividing Int32.MinValue by -1, and
			// Java just silently overflows
			ConstIntExpr v = PeekStack() as ConstIntExpr;
			if(v != null)
			{
				if(v.i == -1)
				{
					PopStack();
					Emit(OpCodes.Neg);
				}
				else
				{
					Emit(OpCodes.Div);
				}
			}
			else
			{
				Emit(OpCodes.Dup);
				Emit(OpCodes.Ldc_I4_M1);
				CodeEmitterLabel label = DefineLabel();
				Emit(OpCodes.Bne_Un_S, label);
				Emit(OpCodes.Pop);
				Emit(OpCodes.Neg);
				CodeEmitterLabel label2 = DefineLabel();
				Emit(OpCodes.Br_S, label2);
				MarkLabel(label);
				Emit(OpCodes.Div);
				MarkLabel(label2);
			}
		}

		internal void LazyEmit_ldiv()
		{
			// we need to special case dividing by -1, because the CLR div instruction
			// throws an OverflowException when dividing Int32.MinValue by -1, and
			// Java just silently overflows
			ConstLongExpr v = PeekStack() as ConstLongExpr;
			if(v != null)
			{
				if(v.l == -1)
				{
					PopStack();
					Emit(OpCodes.Neg);
				}
				else
				{
					Emit(OpCodes.Div);
				}
			}
			else
			{
				Emit(OpCodes.Dup);
				Emit(OpCodes.Ldc_I4_M1);
				Emit(OpCodes.Conv_I8);
				CodeEmitterLabel label = DefineLabel();
				Emit(OpCodes.Bne_Un_S, label);
				Emit(OpCodes.Pop);
				Emit(OpCodes.Neg);
				CodeEmitterLabel label2 = DefineLabel();
				Emit(OpCodes.Br_S, label2);
				MarkLabel(label);
				Emit(OpCodes.Div);
				MarkLabel(label2);
			}
		}

		internal void LazyEmit_instanceof(Type type)
		{
			PushStack(new InstanceOfExpr(type));
		}

		internal void LazyEmit_ifeq(CodeEmitterLabel label)
		{
			LazyEmit_if_ne_eq(label, false);
		}

		internal void LazyEmit_ifne(CodeEmitterLabel label)
		{
			LazyEmit_if_ne_eq(label, true);
		}

		private void LazyEmit_if_ne_eq(CodeEmitterLabel label, bool brtrue)
		{
			InstanceOfExpr instanceof = PeekStack() as InstanceOfExpr;
			if (instanceof != null)
			{
				PopStack();
				Emit(OpCodes.Isinst, instanceof.Type);
			}
			else
			{
				CmpExpr cmp = PeekStack() as CmpExpr;
				if (cmp != null)
				{
					PopStack();
					Emit(brtrue ? OpCodes.Bne_Un : OpCodes.Beq, label);
					return;
				}
			}
			Emit(brtrue ? OpCodes.Brtrue : OpCodes.Brfalse, label);
		}

		internal enum Comparison
		{
			LessOrEqual,
			LessThan,
			GreaterOrEqual,
			GreaterThan
		}

		private void EmitBcc(Comparison comp, CodeEmitterLabel label)
		{
			switch (comp)
			{
				case Comparison.LessOrEqual:
					Emit(OpCodes.Ble, label);
					break;
				case Comparison.LessThan:
					Emit(OpCodes.Blt, label);
					break;
				case Comparison.GreaterOrEqual:
					Emit(OpCodes.Bge, label);
					break;
				case Comparison.GreaterThan:
					Emit(OpCodes.Bgt, label);
					break;
			}
		}

		internal void LazyEmit_if_le_lt_ge_gt(Comparison comp, CodeEmitterLabel label)
		{
			CmpExpr cmp = PeekStack() as CmpExpr;
			if (cmp != null)
			{
				PopStack();
				cmp.EmitBcc(this, comp, label);
			}
			else
			{
				Emit(OpCodes.Ldc_I4_0);
				EmitBcc(comp, label);
			}
		}

		internal void LazyEmit_lcmp()
		{
			PushStack(new LCmpExpr());
		}

		internal void LazyEmit_fcmpl()
		{
			PushStack(new FCmplExpr());
		}

		internal void LazyEmit_fcmpg()
		{
			PushStack(new FCmpgExpr());
		}

		internal void LazyEmit_dcmpl()
		{
			PushStack(new DCmplExpr());
		}

		internal void LazyEmit_dcmpg()
		{
			PushStack(new DCmpgExpr());
		}

		internal void LazyEmitAnd_I4(int v2)
		{
			ConstIntExpr v1 = PeekStack() as ConstIntExpr;
			if (v1 != null)
			{
				PopStack();
				LazyEmitLdc_I4(v1.i & v2);
			}
			else
			{
				LazyEmitLdc_I4(v2);
				Emit(OpCodes.And);
			}
		}

		internal void LazyEmit_baload()
		{
			PushStack(new ByteArrayLoadExpr());
		}

		private bool Match<T1, T2>(out T1 t1, out T2 t2)
			where T1 : Expr
			where T2 : Expr
		{
			if (topOfStack < 2)
			{
				t1 = null;
				t2 = null;
				return false;
			}
			t1 = stackArray[topOfStack - 1] as T1;
			t2 = stackArray[topOfStack - 2] as T2;
			return t1 != null && t2 != null;
		}

		internal void LazyEmit_iand()
		{
			ConstIntExpr v1;
			ByteArrayLoadExpr v2;
			if (Match(out v1, out v2) && v1.i == 0xFF)
			{
				PopStack();
				PopStack();
				Emit(OpCodes.Ldelem_U1);
			}
			else
			{
				Emit(OpCodes.And);
			}
		}

		internal void LazyEmit_land()
		{
			ConstLongExpr v1;
			ConvertLong v2;
			if (Match(out v1, out v2) && v1.l == 0xFF && v2.Expr is ByteArrayLoadExpr)
			{
				PopStack();
				PopStack();
				Emit(OpCodes.Ldelem_U1);
				Emit(OpCodes.Conv_I8);
			}
			else
			{
				Emit(OpCodes.And);
			}
		}

		internal void LazyEmit_i2l()
		{
			PushStack(new ConvertLong(PopStack()));
		}

		internal string PopLazyLdstr()
		{
			ConstStringExpr str = PeekStack() as ConstStringExpr;
			if(str != null)
			{
				PopStack();
				return str.str;
			}
			return null;
		}

		internal TypeWrapper PeekLazyClassLiteral()
		{
			ClassLiteralExpr lit = PeekStack() as ClassLiteralExpr;
			if (lit != null)
			{
				return lit.Type;
			}
			return null;
		}

		private void LazyGen()
		{
			if(lazyBranch != null)
			{
#if !STATIC_COMPILER
				offset += OpCodes.Br.Size + 4;
#endif
				ilgen_real.Emit(OpCodes.Br, lazyBranch.Label);
				lazyBranch = null;
			}
			int len = topOfStack;
			topOfStack = 0;
			for(int i = 0; i < len; i++)
			{
				stackArray[i].Emit(this);
			}
		}

		internal void CheckLabels()
		{
#if LABELCHECK
			foreach(System.Diagnostics.StackFrame frame in labels.Values)
			{
				string name = frame.GetFileName() + ":" + frame.GetFileLineNumber();
				IKVM.Internal.JVM.CriticalFailure("Label failure: " + name, null);
			}
#endif
		}

		abstract class Expr
		{
			internal virtual bool HasSideEffect { get { return false; } }

			internal virtual bool IsIncomplete { get { return false; } }

			internal abstract void Emit(CodeEmitter ilgen);
		}

		abstract class UnaryExpr : Expr
		{
			internal readonly Expr Expr;

			protected UnaryExpr(Expr expr)
			{
				this.Expr = expr;
			}

			internal sealed override bool IsIncomplete
			{
				get { return Expr == null; }
			}

			internal override bool HasSideEffect
			{
				get { return Expr != null && Expr.HasSideEffect; }
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				if (Expr != null)
				{
					Expr.Emit(ilgen);
				}
			}
		}

		abstract class ExprWithExprAndType : UnaryExpr
		{
			internal readonly Type Type;

			protected ExprWithExprAndType(Expr expr, Type type)
				: base(expr)
			{
				this.Type = type;
			}
		}

		sealed class BoxExpr : ExprWithExprAndType
		{
			internal BoxExpr(Expr expr, Type type)
				: base(expr, type)
			{
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				base.Emit(ilgen);
				ilgen.Emit(OpCodes.Box, Type);
			}
		}

		sealed class UnboxExpr : ExprWithExprAndType
		{
			internal UnboxExpr(Expr expr, Type type)
				: base(expr, type)
			{
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				base.Emit(ilgen);
				ilgen.Emit(OpCodes.Unbox, Type);
			}
		}

		sealed class BoxUnboxExpr : ExprWithExprAndType
		{
			internal BoxUnboxExpr(Expr expr, Type type)
				: base(expr, type)
			{
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				base.Emit(ilgen);
				// unbox leaves a pointer to the value of the stack (instead of the value)
				// so we have to copy the value into a local variable and load the address
				// of the local onto the stack
				LocalBuilder local = ilgen.DeclareLocal(Type);
				ilgen.Emit(OpCodes.Stloc, local);
				ilgen.Emit(OpCodes.Ldloca, local);
			}
		}

		sealed class LdobjExpr : ExprWithExprAndType
		{
			internal LdobjExpr(Expr expr, Type type)
				: base(expr, type)
			{
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				base.Emit(ilgen);
				ilgen.Emit(OpCodes.Ldobj, Type);
			}
		}

		sealed class NullExpr : Expr
		{
			internal override void Emit(CodeEmitter ilgen)
			{
				ilgen.Emit(OpCodes.Ldnull);
			}
		}

		sealed class ConstIntExpr : Expr
		{
			internal readonly int i;

			internal ConstIntExpr(int i)
			{
				this.i = i;
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				switch(i)
				{
					case -1:
						ilgen.Emit(OpCodes.Ldc_I4_M1);
						break;
					case 0:
						ilgen.Emit(OpCodes.Ldc_I4_0);
						break;
					case 1:
						ilgen.Emit(OpCodes.Ldc_I4_1);
						break;
					case 2:
						ilgen.Emit(OpCodes.Ldc_I4_2);
						break;
					case 3:
						ilgen.Emit(OpCodes.Ldc_I4_3);
						break;
					case 4:
						ilgen.Emit(OpCodes.Ldc_I4_4);
						break;
					case 5:
						ilgen.Emit(OpCodes.Ldc_I4_5);
						break;
					case 6:
						ilgen.Emit(OpCodes.Ldc_I4_6);
						break;
					case 7:
						ilgen.Emit(OpCodes.Ldc_I4_7);
						break;
					case 8:
						ilgen.Emit(OpCodes.Ldc_I4_8);
						break;
					default:
						if(i >= -128 && i <= 127)
						{
							ilgen.Emit(OpCodes.Ldc_I4_S, (sbyte)i);
						}
						else
						{
							ilgen.Emit(OpCodes.Ldc_I4, i);
						}
						break;
				}
			}
		}

		sealed class ConstLongExpr : Expr
		{
			internal readonly long l;

			internal ConstLongExpr(long l)
			{
				this.l = l;
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				switch (l)
				{
					case -1:
						ilgen.Emit(OpCodes.Ldc_I4_M1);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 0:
						ilgen.Emit(OpCodes.Ldc_I4_0);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 1:
						ilgen.Emit(OpCodes.Ldc_I4_1);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 2:
						ilgen.Emit(OpCodes.Ldc_I4_2);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 3:
						ilgen.Emit(OpCodes.Ldc_I4_3);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 4:
						ilgen.Emit(OpCodes.Ldc_I4_4);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 5:
						ilgen.Emit(OpCodes.Ldc_I4_5);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 6:
						ilgen.Emit(OpCodes.Ldc_I4_6);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 7:
						ilgen.Emit(OpCodes.Ldc_I4_7);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					case 8:
						ilgen.Emit(OpCodes.Ldc_I4_8);
						ilgen.Emit(OpCodes.Conv_I8);
						break;
					default:
						if (l >= -2147483648L && l <= 4294967295L)
						{
							if (l >= -128 && l <= 127)
							{
								ilgen.Emit(OpCodes.Ldc_I4_S, (sbyte)l);
							}
							else
							{
								ilgen.Emit(OpCodes.Ldc_I4, (int)l);
							}
							if (l < 0)
							{
								ilgen.Emit(OpCodes.Conv_I8);
							}
							else
							{
								ilgen.Emit(OpCodes.Conv_U8);
							}
						}
						else
						{
							ilgen.Emit(OpCodes.Ldc_I8, l);
						}
						break;
				}
			}
		}

		sealed class ConstStringExpr : Expr
		{
			internal readonly string str;

			internal ConstStringExpr(string str)
			{
				this.str = str;
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				ilgen.Emit(OpCodes.Ldstr, str);
			}
		}

		sealed class InstanceOfExpr : Expr
		{
			internal readonly Type Type;

			internal InstanceOfExpr(Type type)
			{
				this.Type = type;
			}

			internal override bool IsIncomplete
			{
				get
				{
					return true;
				}
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				ilgen.Emit(OpCodes.Isinst, this.Type);
				ilgen.Emit(OpCodes.Ldnull);
				ilgen.Emit(OpCodes.Cgt_Un);
			}
		}

		abstract class CmpExpr : Expr
		{
			internal CmpExpr()
			{
			}

			internal override bool IsIncomplete
			{
				get
				{
					return true;
				}
			}

			internal abstract void EmitBcc(CodeEmitter ilgen, Comparison comp, CodeEmitterLabel label);
		}

		sealed class LCmpExpr : CmpExpr
		{
			internal LCmpExpr()
			{
			}

			internal sealed override void Emit(CodeEmitter ilgen)
			{
				LocalBuilder value1 = ilgen.AllocTempLocal(Types.Int64);
				LocalBuilder value2 = ilgen.AllocTempLocal(Types.Int64);
				ilgen.Emit(OpCodes.Stloc, value2);
				ilgen.Emit(OpCodes.Stloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Cgt);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Clt);
				ilgen.Emit(OpCodes.Sub);
				ilgen.ReleaseTempLocal(value2);
				ilgen.ReleaseTempLocal(value1);
			}

			internal sealed override void EmitBcc(CodeEmitter ilgen, Comparison comp, CodeEmitterLabel label)
			{
				ilgen.EmitBcc(comp, label);
			}
		}

		class FCmplExpr : CmpExpr
		{
			protected virtual Type FloatOrDouble()
			{
				return Types.Single;
			}

			internal sealed override void Emit(CodeEmitter ilgen)
			{
				LocalBuilder value1 = ilgen.AllocTempLocal(FloatOrDouble());
				LocalBuilder value2 = ilgen.AllocTempLocal(FloatOrDouble());
				ilgen.Emit(OpCodes.Stloc, value2);
				ilgen.Emit(OpCodes.Stloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Cgt);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Clt_Un);
				ilgen.Emit(OpCodes.Sub);
				ilgen.ReleaseTempLocal(value1);
				ilgen.ReleaseTempLocal(value2);
			}

			internal sealed override void EmitBcc(CodeEmitter ilgen, Comparison comp, CodeEmitterLabel label)
			{
				switch (comp)
				{
					case Comparison.LessOrEqual:
						ilgen.Emit(OpCodes.Ble_Un, label);
						break;
					case Comparison.LessThan:
						ilgen.Emit(OpCodes.Blt_Un, label);
						break;
					case Comparison.GreaterOrEqual:
						ilgen.Emit(OpCodes.Bge, label);
						break;
					case Comparison.GreaterThan:
						ilgen.Emit(OpCodes.Bgt, label);
						break;
				}
			}
		}

		class FCmpgExpr : CmpExpr
		{
			protected virtual Type FloatOrDouble()
			{
				return Types.Single;
			}

			internal sealed override void Emit(CodeEmitter ilgen)
			{
				LocalBuilder value1 = ilgen.AllocTempLocal(FloatOrDouble());
				LocalBuilder value2 = ilgen.AllocTempLocal(FloatOrDouble());
				ilgen.Emit(OpCodes.Stloc, value2);
				ilgen.Emit(OpCodes.Stloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Cgt_Un);
				ilgen.Emit(OpCodes.Ldloc, value1);
				ilgen.Emit(OpCodes.Ldloc, value2);
				ilgen.Emit(OpCodes.Clt);
				ilgen.Emit(OpCodes.Sub);
				ilgen.ReleaseTempLocal(value1);
				ilgen.ReleaseTempLocal(value2);
			}

			internal sealed override void EmitBcc(CodeEmitter ilgen, Comparison comp, CodeEmitterLabel label)
			{
				switch (comp)
				{
					case Comparison.LessOrEqual:
						ilgen.Emit(OpCodes.Ble, label);
						break;
					case Comparison.LessThan:
						ilgen.Emit(OpCodes.Blt, label);
						break;
					case Comparison.GreaterOrEqual:
						ilgen.Emit(OpCodes.Bge_Un, label);
						break;
					case Comparison.GreaterThan:
						ilgen.Emit(OpCodes.Bgt_Un, label);
						break;
				}
			}
		}

		sealed class DCmplExpr : FCmplExpr
		{
			protected override Type FloatOrDouble()
			{
				return Types.Double;
			}
		}

		sealed class DCmpgExpr : FCmpgExpr
		{
			protected override Type FloatOrDouble()
			{
				return Types.Double;
			}
		}

		sealed class ClassLiteralExpr : Expr
		{
			internal readonly TypeWrapper Type;

			internal ClassLiteralExpr(TypeWrapper type)
			{
				this.Type = type;
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				Type.EmitClassLiteral(ilgen);
			}
		}

		sealed class ByteArrayLoadExpr : Expr
		{
			internal override void Emit(CodeEmitter ilgen)
			{
				ilgen.Emit(OpCodes.Ldelem_I1);
			}

			internal override bool HasSideEffect
			{
				get { return true; }
			}

			internal override bool IsIncomplete
			{
				get { return true; }
			}
		}

		sealed class ConvertLong : UnaryExpr
		{
			internal ConvertLong(Expr expr)
				: base(expr)
			{
			}

			internal override void Emit(CodeEmitter ilgen)
			{
				base.Emit(ilgen);
				ilgen.Emit(OpCodes.Conv_I8);
			}
		}
	}
}