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diff --git a/ICSharpCode.Decompiler/ILAst/LiftedOperators.cs b/ICSharpCode.Decompiler/ILAst/LiftedOperators.cs
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+// Copyright (c) 2011 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
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+using Mono.Cecil;
+
+namespace ICSharpCode.Decompiler.ILAst
+{
+ partial class ILAstOptimizer
+ {
+ bool SimplifyLiftedOperators(List<ILNode> body, ILExpression expr, int pos)
+ {
+ if (!new PatternMatcher(typeSystem).SimplifyLiftedOperators(expr)) return false;
+
+ var inlining = new ILInlining(method);
+ while (--pos >= 0 && inlining.InlineIfPossible(body, ref pos)) ;
+
+ return true;
+ }
+
+ sealed class PatternMatcher
+ {
+ readonly TypeSystem typeSystem;
+ public PatternMatcher(TypeSystem typeSystem)
+ {
+ this.typeSystem = typeSystem;
+ }
+
+ public bool SimplifyLiftedOperators(ILExpression expr)
+ {
+ if (Simplify(expr)) return true;
+
+ bool modified = false;
+ foreach (var a in expr.Arguments)
+ modified |= SimplifyLiftedOperators(a);
+ return modified;
+ }
+
+ abstract class Pattern
+ {
+ public readonly Pattern[] Arguments;
+
+ protected Pattern(Pattern[] arguments)
+ {
+ Arguments = arguments;
+ }
+
+ public virtual bool Match(PatternMatcher pm, ILExpression e)
+ {
+ if (e.Arguments.Count != Arguments.Length || e.Prefixes != null) return false;
+ for (int i = 0; i < Arguments.Length; i++)
+ if (!Arguments[i].Match(pm, e.Arguments[i])) return false;
+ return true;
+ }
+
+ public virtual ILExpression BuildNew(PatternMatcher pm)
+ {
+ throw new NotSupportedException();
+ }
+
+ public static Pattern operator &(Pattern a, Pattern b)
+ {
+ return new ILPattern(ILCode.LogicAnd, a, b);
+ }
+
+ public static Pattern operator |(Pattern a, Pattern b)
+ {
+ return new ILPattern(ILCode.LogicOr, a, b);
+ }
+
+ public static Pattern operator !(Pattern a)
+ {
+ return new ILPattern(ILCode.LogicNot, a);
+ }
+ }
+
+ sealed class ILPattern : Pattern
+ {
+ readonly ILCode code;
+
+ public ILPattern(ILCode code, params Pattern[] arguments)
+ : base(arguments)
+ {
+ this.code = code;
+ }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ return e.Code == code && base.Match(pm, e);
+ }
+
+ public override ILExpression BuildNew(PatternMatcher pm)
+ {
+ var args = new ILExpression[Arguments.Length];
+ for (int i = 0; i < args.Length; i++) args[i] = Arguments[i].BuildNew(pm);
+ TypeReference t = null;
+ switch (code) {
+ case ILCode.Ceq:
+ case ILCode.Cne:
+ t = pm.typeSystem.Boolean;
+ break;
+ case ILCode.NullCoalescing:
+ t = args[1].InferredType;
+ break;
+ }
+ return new ILExpression(code, null, args) { InferredType = t };
+ }
+ }
+
+ sealed class MethodPattern : Pattern
+ {
+ readonly ILCode code;
+ readonly string method;
+
+ public MethodPattern(ILCode code, string method, params Pattern[] arguments)
+ : base(arguments)
+ {
+ this.code = code;
+ this.method = method;
+ }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ if (e.Code != code) return false;
+ var m = (MethodReference)e.Operand;
+ return m.Name == method && TypeAnalysis.IsNullableType(m.DeclaringType) && base.Match(pm, e);
+ }
+ }
+
+ enum OperatorType
+ {
+ Equality, InEquality, Comparison, Other
+ }
+
+ sealed class OperatorPattern : Pattern
+ {
+ OperatorType type;
+ bool simple;
+
+ public OperatorPattern() : base(null) { }
+
+ public OperatorPattern(OperatorType type, bool simple)
+ : this()
+ {
+ this.type = type;
+ this.simple = simple;
+ }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ switch (e.Code) {
+ case ILCode.Ceq:
+ if (type != OperatorType.Equality) return false;
+ break;
+ case ILCode.Cne:
+ if (type != OperatorType.InEquality) return false;
+ break;
+ case ILCode.Cgt:
+ case ILCode.Cgt_Un:
+ case ILCode.Cge:
+ case ILCode.Cge_Un:
+ case ILCode.Clt:
+ case ILCode.Clt_Un:
+ case ILCode.Cle:
+ case ILCode.Cle_Un:
+ if (type != OperatorType.Comparison) return false;
+ break;
+ case ILCode.Add:
+ case ILCode.Add_Ovf:
+ case ILCode.Add_Ovf_Un:
+ case ILCode.Sub:
+ case ILCode.Sub_Ovf:
+ case ILCode.Sub_Ovf_Un:
+ case ILCode.Mul:
+ case ILCode.Mul_Ovf:
+ case ILCode.Mul_Ovf_Un:
+ case ILCode.Div:
+ case ILCode.Div_Un:
+ case ILCode.Rem:
+ case ILCode.Rem_Un:
+ case ILCode.And:
+ case ILCode.Or:
+ case ILCode.Xor:
+ case ILCode.Shl:
+ case ILCode.Shr:
+ case ILCode.Shr_Un:
+ case ILCode.Not:
+ case ILCode.Neg:
+ case ILCode.LogicNot:
+ if (type != OperatorType.Other) return false;
+ break;
+ case ILCode.Call:
+ var m = e.Operand as MethodReference;
+ if (m == null || m.HasThis || !m.HasParameters || e.Arguments.Count > 2 || !IsCustomOperator(m.Name)) return false;
+ break;
+ default: return false;
+ }
+ if (pm.Operator != null) throw new InvalidOperationException();
+ pm.Operator = e;
+
+ var a0 = e.Arguments[0];
+ if (!simple) return VariableAGetValueOrDefault.Match(pm, a0) && VariableBGetValueOrDefault.Match(pm, e.Arguments[1]);
+ if (e.Arguments.Count == 1) return VariableAGetValueOrDefault.Match(pm, a0);
+ if (VariableAGetValueOrDefault.Match(pm, a0)) {
+ pm.SimpleOperand = e.Arguments[1];
+ pm.SimpleLeftOperand = false;
+ return true;
+ }
+ if (VariableAGetValueOrDefault.Match(pm, e.Arguments[1])) {
+ pm.SimpleOperand = a0;
+ pm.SimpleLeftOperand = true;
+ return true;
+ }
+ return false;
+ }
+
+ bool IsCustomOperator(string s)
+ {
+ switch (type) {
+ case OperatorType.Equality: return s == "op_Equality";
+ case OperatorType.InEquality: return s == "op_Inequality";
+ case OperatorType.Comparison:
+ if (s.Length < 11 || !s.StartsWith("op_", StringComparison.Ordinal)) return false;
+ switch (s) {
+ case "op_GreaterThan":
+ case "op_GreaterThanOrEqual":
+ case "op_LessThan":
+ case "op_LessThanOrEqual": return true;
+ default: return false;
+ }
+ default:
+ if (s.Length < 10 || !s.StartsWith("op_", StringComparison.Ordinal)) return false;
+ switch (s) {
+ case "op_Addition":
+ case "op_Subtraction":
+ case "op_Multiply":
+ case "op_Division":
+ case "op_Modulus":
+ case "op_BitwiseAnd":
+ case "op_BitwiseOr":
+ case "op_ExclusiveOr":
+ case "op_LeftShift":
+ case "op_RightShift":
+ case "op_UnaryNegation":
+ case "op_UnaryPlus":
+ case "op_LogicalNot":
+ case "op_OnesComplement":
+ case "op_Increment":
+ case "op_Decrement": return true;
+ default: return false;
+ }
+ }
+ }
+
+ public override ILExpression BuildNew(PatternMatcher pm)
+ {
+ var res = pm.Operator;
+ res.Arguments.Clear();
+ if (pm.SimpleLeftOperand) res.Arguments.Add(pm.SimpleOperand);
+ res.Arguments.Add(VariableA.BuildNew(pm));
+ if (pm.B != null) res.Arguments.Add(VariableB.BuildNew(pm));
+ else if (pm.SimpleOperand != null && !pm.SimpleLeftOperand) res.Arguments.Add(pm.SimpleOperand);
+ return res;
+ }
+ }
+
+ sealed class AnyPattern : Pattern
+ {
+ public AnyPattern() : base(null) { }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ if (pm.SimpleOperand != null) throw new InvalidOperationException();
+ pm.SimpleOperand = e;
+ return true;
+ }
+
+ public override ILExpression BuildNew(PatternMatcher pm)
+ {
+ return pm.SimpleOperand;
+ }
+ }
+
+ sealed class VariablePattern : Pattern
+ {
+ readonly ILCode code;
+ readonly bool b;
+
+ public VariablePattern(ILCode code, bool b)
+ : base(null)
+ {
+ this.code = code;
+ this.b = b;
+ }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ if (e.Code != code) return false;
+ var v = e.Operand as ILVariable;
+ return v != null && (b ? Capture(ref pm.B, v) : Capture(ref pm.A, v));
+ }
+
+ static bool Capture(ref ILVariable pmvar, ILVariable v)
+ {
+ if (pmvar != null) return pmvar == v;
+ pmvar = v;
+ return true;
+ }
+
+ static readonly ILExpression[] EmptyArguments = new ILExpression[0];
+ public override ILExpression BuildNew(PatternMatcher pm)
+ {
+ var v = b ? pm.B : pm.A;
+ var e = new ILExpression(ILCode.Ldloc, v, EmptyArguments);
+ if (TypeAnalysis.IsNullableType(v.Type)) e = new ILExpression(ILCode.ValueOf, null, e);
+ return e;
+ }
+ }
+
+ sealed class BooleanPattern : Pattern
+ {
+ public static readonly Pattern False = new BooleanPattern(false), True = new BooleanPattern(true);
+
+ readonly object value;
+ BooleanPattern(bool value)
+ : base(null)
+ {
+ this.value = Convert.ToInt32(value);
+ }
+
+ public override bool Match(PatternMatcher pm, ILExpression e)
+ {
+ return e.Code == ILCode.Ldc_I4 && TypeAnalysis.IsBoolean(e.InferredType) && Equals(e.Operand, value);
+ }
+
+ public override ILExpression BuildNew(PatternMatcher pm)
+ {
+ // boolean constants are wrapped inside a container to disable simplyfication of equality comparisons
+ return new ILExpression(ILCode.Wrap, null, new ILExpression(ILCode.Ldc_I4, value));
+ }
+ }
+
+ static readonly Pattern VariableRefA = new VariablePattern(ILCode.Ldloca, false), VariableRefB = new VariablePattern(ILCode.Ldloca, true);
+ static readonly Pattern VariableA = new VariablePattern(ILCode.Ldloc, false), VariableB = new VariablePattern(ILCode.Ldloc, true);
+ static readonly Pattern VariableAHasValue = new MethodPattern(ILCode.CallGetter, "get_HasValue", VariableRefA);
+ static readonly Pattern VariableAGetValueOrDefault = new MethodPattern(ILCode.Call, "GetValueOrDefault", VariableRefA);
+ static readonly Pattern VariableBHasValue = new MethodPattern(ILCode.CallGetter, "get_HasValue", VariableRefB);
+ static readonly Pattern VariableBGetValueOrDefault = new MethodPattern(ILCode.Call, "GetValueOrDefault", VariableRefB);
+ static readonly Pattern CeqHasValue = new ILPattern(ILCode.Ceq, VariableAHasValue, VariableBHasValue);
+ static readonly Pattern CneHasValue = new ILPattern(ILCode.Cne, VariableAHasValue, VariableBHasValue);
+ static readonly Pattern AndHasValue = new ILPattern(ILCode.And, VariableAHasValue, VariableBHasValue);
+ static readonly Pattern Any = new AnyPattern();
+ static readonly Pattern OperatorVariableAB = new OperatorPattern();
+
+ static OperatorPattern OperatorNN(OperatorType type)
+ {
+ return new OperatorPattern(type, false);
+ }
+
+ static OperatorPattern OperatorNV(OperatorType type)
+ {
+ return new OperatorPattern(type, true);
+ }
+
+ static Pattern NewObj(Pattern p)
+ {
+ return new MethodPattern(ILCode.Newobj, ".ctor", p);
+ }
+
+ static readonly Pattern[] Comparisons = new Pattern[] {
+ /* both operands nullable */
+ // == (primitive, decimal)
+ OperatorNN(OperatorType.Equality) & CeqHasValue,
+ // == (struct)
+ CeqHasValue & (!VariableAHasValue | OperatorNN(OperatorType.Equality)),
+ // != (primitive, decimal)
+ OperatorNN(OperatorType.InEquality) | CneHasValue,
+ // != (struct)
+ CneHasValue | (VariableAHasValue & OperatorNN(OperatorType.InEquality)),
+ // > , < , >= , <= (primitive, decimal)
+ OperatorNN(OperatorType.Comparison) & AndHasValue,
+ // > , < , >= , <= (struct)
+ AndHasValue & OperatorNN(OperatorType.Comparison),
+
+ /* only one operand nullable */
+ // == (primitive, decimal)
+ OperatorNV(OperatorType.Equality) & VariableAHasValue,
+ // == (struct)
+ VariableAHasValue & OperatorNV(OperatorType.Equality),
+ // != (primitive, decimal)
+ OperatorNV(OperatorType.InEquality) | !VariableAHasValue,
+ // != (struct)
+ !VariableAHasValue | OperatorNV(OperatorType.InEquality),
+ // > , <, >= , <= (primitive, decimal)
+ OperatorNV(OperatorType.Comparison) & VariableAHasValue,
+ // > , < , >= , <= (struct)
+ VariableAHasValue & OperatorNV(OperatorType.Comparison),
+ };
+
+ static readonly Pattern[] Other = new Pattern[] {
+ /* both operands nullable */
+ // & (bool)
+ new ILPattern(ILCode.TernaryOp, VariableAGetValueOrDefault | (!VariableBGetValueOrDefault & !VariableAHasValue), VariableB, VariableA),
+ new ILPattern(ILCode.And, VariableA, VariableB),
+ // | (bool)
+ new ILPattern(ILCode.TernaryOp, VariableAGetValueOrDefault | (!VariableBGetValueOrDefault & !VariableAHasValue), VariableA, VariableB),
+ new ILPattern(ILCode.Or, VariableA, VariableB),
+ // null coalescing
+ new ILPattern(ILCode.TernaryOp, VariableAHasValue, NewObj(VariableAGetValueOrDefault), VariableB),
+ new ILPattern(ILCode.NullCoalescing, VariableA, VariableB),
+ // all other
+ new ILPattern(ILCode.TernaryOp, AndHasValue, NewObj(OperatorNN(OperatorType.Other)), new ILPattern(ILCode.DefaultValue)),
+ OperatorVariableAB,
+
+ /* only one operand nullable */
+ // & (bool)
+ new ILPattern(ILCode.TernaryOp, Any, VariableA, NewObj(BooleanPattern.False)),
+ new ILPattern(ILCode.And, VariableA, Any),
+ // | (bool)
+ new ILPattern(ILCode.TernaryOp, Any, NewObj(BooleanPattern.True), VariableA),
+ new ILPattern(ILCode.Or, VariableA, Any),
+ // == true
+ VariableAGetValueOrDefault & VariableAHasValue,
+ new ILPattern(ILCode.Ceq, VariableA, BooleanPattern.True),
+ // != true
+ !VariableAGetValueOrDefault | !VariableAHasValue,
+ new ILPattern(ILCode.Cne, VariableA, BooleanPattern.True),
+ // == false
+ !VariableAGetValueOrDefault & VariableAHasValue,
+ new ILPattern(ILCode.Ceq, VariableA, BooleanPattern.False),
+ // != false
+ VariableAGetValueOrDefault | !VariableAHasValue,
+ new ILPattern(ILCode.Cne, VariableA, BooleanPattern.False),
+ // ?? true
+ !VariableAHasValue | VariableAGetValueOrDefault,
+ new ILPattern(ILCode.NullCoalescing, VariableA, BooleanPattern.True),
+ // ?? false
+ VariableAHasValue & VariableAGetValueOrDefault,
+ new ILPattern(ILCode.NullCoalescing, VariableA, BooleanPattern.False),
+ // null coalescing
+ new ILPattern(ILCode.TernaryOp, VariableAHasValue, VariableAGetValueOrDefault, Any),
+ new ILPattern(ILCode.NullCoalescing, VariableA, Any),
+ // all other
+ new ILPattern(ILCode.TernaryOp, VariableAHasValue, NewObj(OperatorNV(OperatorType.Other)), new ILPattern(ILCode.DefaultValue)),
+ OperatorVariableAB,
+ };
+
+ ILVariable A, B;
+ ILExpression Operator, SimpleOperand;
+ bool SimpleLeftOperand;
+
+ void Reset()
+ {
+ A = null;
+ B = null;
+ Operator = null;
+ SimpleOperand = null;
+ SimpleLeftOperand = false;
+ }
+
+ bool Simplify(ILExpression expr)
+ {
+ if (expr.Code == ILCode.TernaryOp || expr.Code == ILCode.LogicAnd || expr.Code == ILCode.LogicOr) {
+ Pattern[] ps;
+ if (expr.Code != ILCode.TernaryOp) {
+ ps = Comparisons;
+ for (int i = 0; i < ps.Length; i++) {
+ Reset();
+ if (!ps[i].Match(this, expr)) continue;
+ SetResult(expr, OperatorVariableAB.BuildNew(this));
+ return true;
+ }
+ }
+ ps = Other;
+ for (int i = 0; i < ps.Length; i += 2) {
+ Reset();
+ if (!ps[i].Match(this, expr)) continue;
+ var n = ps[i + 1].BuildNew(this);
+ SetResult(expr, n);
+ if (n.Code == ILCode.NullCoalescing) {
+ // if both operands are nullable then the result is also nullable
+ if (n.Arguments[1].Code == ILCode.ValueOf) {
+ n.Arguments[0] = n.Arguments[0].Arguments[0];
+ n.Arguments[1] = n.Arguments[1].Arguments[0];
+ }
+ } else if (n.Code != ILCode.Ceq && n.Code != ILCode.Cne) {
+ expr.Code = ILCode.NullableOf;
+ expr.InferredType = expr.ExpectedType = null;
+ }
+ return true;
+ }
+ }
+ return false;
+ }
+
+ static void SetResult(ILExpression expr, ILExpression n)
+ {
+ // IL ranges from removed nodes are assigned to the new operator expression
+ var removednodes = expr.GetSelfAndChildrenRecursive<ILExpression>().Except(n.GetSelfAndChildrenRecursive<ILExpression>());
+ n.ILRanges.AddRange(removednodes.SelectMany(el => el.ILRanges));
+ // the new expression is wrapped in a container so that negations aren't pushed through lifted comparison operations
+ expr.Code = ILCode.Wrap;
+ expr.Arguments.Clear();
+ expr.Arguments.Add(n);
+ expr.ILRanges.Clear();
+ expr.InferredType = n.InferredType;
+ }
+ }
+ }
+}
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