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408 lines
15 KiB
408 lines
15 KiB
// Copyright (c) 2014-2017 Daniel Grunwald |
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// |
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this |
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// software and associated documentation files (the "Software"), to deal in the Software |
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// without restriction, including without limitation the rights to use, copy, modify, merge, |
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons |
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// to whom the Software is furnished to do so, subject to the following conditions: |
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// |
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// The above copyright notice and this permission notice shall be included in all copies or |
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// substantial portions of the Software. |
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// |
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, |
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR |
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE |
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR |
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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// DEALINGS IN THE SOFTWARE. |
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using System; |
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using System.Diagnostics; |
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using System.Linq; |
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using ICSharpCode.Decompiler.TypeSystem; |
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using ICSharpCode.Decompiler.TypeSystem.Implementation; |
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namespace ICSharpCode.Decompiler.IL.Transforms |
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{ |
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/// <summary> |
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/// Collection of transforms that detect simple expression patterns |
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/// (e.g. 'cgt.un(..., ld.null)') and replace them with different instructions. |
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/// </summary> |
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/// <remarks> |
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/// Should run after inlining so that the expression patterns can be detected. |
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/// </remarks> |
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public class ExpressionTransforms : ILVisitor, IStatementTransform |
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{ |
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internal StatementTransformContext context; |
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public static void RunOnSingleStatment(ILInstruction statement, ILTransformContext context) |
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{ |
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if (statement == null) |
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throw new ArgumentNullException(nameof(statement)); |
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if (!(statement.Parent is Block parent)) |
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throw new ArgumentException("ILInstruction must be a statement, i.e., direct child of a block."); |
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new ExpressionTransforms().Run(parent, statement.ChildIndex, new StatementTransformContext(new BlockTransformContext(context))); |
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} |
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public void Run(Block block, int pos, StatementTransformContext context) |
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{ |
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this.context = context; |
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context.StepStartGroup($"ExpressionTransforms ({block.Label}:{pos})", block.Instructions[pos]); |
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block.Instructions[pos].AcceptVisitor(this); |
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context.StepEndGroup(keepIfEmpty: true); |
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} |
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protected override void Default(ILInstruction inst) |
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{ |
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foreach (var child in inst.Children) { |
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child.AcceptVisitor(this); |
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} |
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} |
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protected internal override void VisitBlock(Block block) |
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{ |
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// Don't visit child blocks; since this is a block transform |
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// we know those were already handled previously. |
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} |
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protected internal override void VisitComp(Comp inst) |
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{ |
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// "logic.not(arg)" is sugar for "comp(arg != ldc.i4 0)" |
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if (inst.MatchLogicNot(out var arg)) { |
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VisitLogicNot(inst, arg); |
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return; |
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} else if (inst.Kind == ComparisonKind.Inequality && inst.LiftingKind == ComparisonLiftingKind.None |
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&& inst.Right.MatchLdcI4(0) && (IfInstruction.IsInConditionSlot(inst) || inst.Left is Comp) |
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) { |
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// if (comp(x != 0)) ==> if (x) |
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// comp(comp(...) != 0) => comp(...) |
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context.Step("Remove redundant comp(... != 0)", inst); |
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inst.Left.AddILRange(inst.ILRange); |
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inst.ReplaceWith(inst.Left); |
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inst.Left.AcceptVisitor(this); |
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return; |
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} |
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base.VisitComp(inst); |
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if (inst.IsLifted) { |
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return; |
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} |
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if (inst.Right.MatchLdNull()) { |
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if (inst.Kind == ComparisonKind.GreaterThan) { |
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context.Step("comp(left > ldnull) => comp(left != ldnull)", inst); |
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inst.Kind = ComparisonKind.Inequality; |
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} else if (inst.Kind == ComparisonKind.LessThanOrEqual) { |
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context.Step("comp(left <= ldnull) => comp(left == ldnull)", inst); |
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inst.Kind = ComparisonKind.Equality; |
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} |
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} else if (inst.Left.MatchLdNull()) { |
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if (inst.Kind == ComparisonKind.LessThan) { |
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context.Step("comp(ldnull < right) => comp(ldnull != right)", inst); |
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inst.Kind = ComparisonKind.Inequality; |
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} else if (inst.Kind == ComparisonKind.GreaterThanOrEqual) { |
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context.Step("comp(ldnull >= right) => comp(ldnull == right)", inst); |
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inst.Kind = ComparisonKind.Equality; |
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} |
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} |
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var rightWithoutConv = inst.Right.UnwrapConv(ConversionKind.SignExtend).UnwrapConv(ConversionKind.ZeroExtend); |
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if (rightWithoutConv.MatchLdcI4(0) |
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&& inst.Sign == Sign.Unsigned |
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&& (inst.Kind == ComparisonKind.GreaterThan || inst.Kind == ComparisonKind.LessThanOrEqual)) |
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{ |
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if (inst.Kind == ComparisonKind.GreaterThan) { |
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context.Step("comp.unsigned(left > ldc.i4 0) => comp(left != ldc.i4 0)", inst); |
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inst.Kind = ComparisonKind.Inequality; |
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VisitComp(inst); |
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return; |
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} else if (inst.Kind == ComparisonKind.LessThanOrEqual) { |
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context.Step("comp.unsigned(left <= ldc.i4 0) => comp(left == ldc.i4 0)", inst); |
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inst.Kind = ComparisonKind.Equality; |
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VisitComp(inst); |
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return; |
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} |
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} else if (rightWithoutConv.MatchLdcI4(0) && inst.Kind.IsEqualityOrInequality()) { |
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if (inst.Left.MatchLdLen(StackType.I, out ILInstruction array)) { |
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// comp.unsigned(ldlen array == conv i4->i(ldc.i4 0)) |
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// => comp(ldlen.i4 array == ldc.i4 0) |
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// This is a special case where the C# compiler doesn't generate conv.i4 after ldlen. |
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context.Step("comp(ldlen.i4 array == ldc.i4 0)", inst); |
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inst.InputType = StackType.I4; |
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inst.Left.ReplaceWith(new LdLen(StackType.I4, array) { ILRange = inst.Left.ILRange }); |
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inst.Right = rightWithoutConv; |
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} |
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} |
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if (inst.Right.MatchLdNull() && inst.Left.MatchBox(out arg, out var type) && type.Kind == TypeKind.TypeParameter) { |
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if (inst.Kind == ComparisonKind.Equality) { |
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context.Step("comp(box T(..) == ldnull) -> comp(.. == ldnull)", inst); |
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inst.Left = arg; |
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} |
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if (inst.Kind == ComparisonKind.Inequality) { |
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context.Step("comp(box T(..) != ldnull) -> comp(.. != ldnull)", inst); |
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inst.Left = arg; |
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} |
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} |
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} |
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protected internal override void VisitConv(Conv inst) |
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{ |
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inst.Argument.AcceptVisitor(this); |
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if (inst.Argument.MatchLdLen(StackType.I, out ILInstruction array) && inst.TargetType.IsIntegerType() && !inst.CheckForOverflow) { |
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context.Step("conv.i4(ldlen array) => ldlen.i4(array)", inst); |
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inst.AddILRange(inst.Argument.ILRange); |
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inst.ReplaceWith(new LdLen(inst.TargetType.GetStackType(), array) { ILRange = inst.ILRange }); |
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} |
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} |
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protected internal override void VisitBox(Box inst) |
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{ |
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inst.Argument.AcceptVisitor(this); |
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if (inst.Type.IsReferenceType == true && inst.Argument.ResultType == inst.ResultType) { |
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// For reference types, box is a no-op. |
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context.Step("box ref-type(arg) => arg", inst); |
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inst.Argument.AddILRange(inst.ILRange); |
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inst.ReplaceWith(inst.Argument); |
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} |
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} |
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protected internal override void VisitLdElema(LdElema inst) |
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{ |
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base.VisitLdElema(inst); |
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CleanUpArrayIndices(inst.Indices); |
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} |
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protected internal override void VisitNewArr(NewArr inst) |
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{ |
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base.VisitNewArr(inst); |
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CleanUpArrayIndices(inst.Indices); |
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} |
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void CleanUpArrayIndices(InstructionCollection<ILInstruction> indices) |
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{ |
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foreach (ILInstruction index in indices) { |
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if (index is Conv conv && conv.ResultType == StackType.I |
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&& (conv.Kind == ConversionKind.Truncate && conv.CheckForOverflow |
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|| conv.Kind == ConversionKind.ZeroExtend || conv.Kind == ConversionKind.SignExtend) |
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) { |
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context.Step("Remove conv.i from array index", index); |
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index.ReplaceWith(conv.Argument); |
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} |
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} |
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} |
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void VisitLogicNot(Comp inst, ILInstruction arg) |
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{ |
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ILInstruction lhs, rhs; |
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if (arg is Comp comp) { |
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if ((!comp.InputType.IsFloatType() && !comp.IsLifted) || comp.Kind.IsEqualityOrInequality()) { |
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context.Step("push negation into comparison", inst); |
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comp.Kind = comp.Kind.Negate(); |
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comp.AddILRange(inst.ILRange); |
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inst.ReplaceWith(comp); |
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} |
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comp.AcceptVisitor(this); |
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} else if (arg.MatchLogicAnd(out lhs, out rhs)) { |
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// logic.not(if (lhs) rhs else ldc.i4 0) |
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// ==> if (logic.not(lhs)) ldc.i4 1 else logic.not(rhs) |
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context.Step("push negation into logic.and", inst); |
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IfInstruction ifInst = (IfInstruction)arg; |
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var ldc0 = ifInst.FalseInst; |
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Debug.Assert(ldc0.MatchLdcI4(0)); |
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ifInst.Condition = Comp.LogicNot(lhs, inst.ILRange); |
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ifInst.TrueInst = new LdcI4(1) { ILRange = ldc0.ILRange }; |
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ifInst.FalseInst = Comp.LogicNot(rhs, inst.ILRange); |
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inst.ReplaceWith(ifInst); |
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ifInst.AcceptVisitor(this); |
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} else if (arg.MatchLogicOr(out lhs, out rhs)) { |
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// logic.not(if (lhs) ldc.i4 1 else rhs) |
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// ==> if (logic.not(lhs)) logic.not(rhs) else ldc.i4 0) |
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context.Step("push negation into logic.or", inst); |
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IfInstruction ifInst = (IfInstruction)arg; |
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var ldc1 = ifInst.TrueInst; |
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Debug.Assert(ldc1.MatchLdcI4(1)); |
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ifInst.Condition = Comp.LogicNot(lhs, inst.ILRange); |
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ifInst.TrueInst = Comp.LogicNot(rhs, inst.ILRange); |
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ifInst.FalseInst = new LdcI4(0) { ILRange = ldc1.ILRange }; |
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inst.ReplaceWith(ifInst); |
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ifInst.AcceptVisitor(this); |
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} else { |
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arg.AcceptVisitor(this); |
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} |
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} |
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protected internal override void VisitCall(Call inst) |
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{ |
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var expr = EarlyExpressionTransforms.HandleCall(inst, context); |
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if (expr != null) { |
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// The resulting expression may trigger further rules, so continue visiting the replacement: |
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expr.AcceptVisitor(this); |
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} else { |
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base.VisitCall(inst); |
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TransformAssignment.HandleCallCompoundAssign(inst, context); |
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} |
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} |
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protected internal override void VisitCallVirt(CallVirt inst) |
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{ |
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base.VisitCallVirt(inst); |
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TransformAssignment.HandleCallCompoundAssign(inst, context); |
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} |
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protected internal override void VisitNewObj(NewObj inst) |
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{ |
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LdcDecimal decimalConstant; |
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if (TransformDecimalCtorToConstant(inst, out decimalConstant)) { |
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context.Step("TransformDecimalCtorToConstant", inst); |
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inst.ReplaceWith(decimalConstant); |
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return; |
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} |
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base.VisitNewObj(inst); |
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} |
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bool TransformDecimalCtorToConstant(NewObj inst, out LdcDecimal result) |
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{ |
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IType t = inst.Method.DeclaringType; |
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result = null; |
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if (!t.IsKnownType(KnownTypeCode.Decimal)) |
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return false; |
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var args = inst.Arguments; |
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if (args.Count == 1) { |
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int val; |
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if (args[0].MatchLdcI4(out val)) { |
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result = new LdcDecimal(val); |
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return true; |
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} |
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} else if (args.Count == 5) { |
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int lo, mid, hi, isNegative, scale; |
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if (args[0].MatchLdcI4(out lo) && args[1].MatchLdcI4(out mid) && |
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args[2].MatchLdcI4(out hi) && args[3].MatchLdcI4(out isNegative) && |
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args[4].MatchLdcI4(out scale)) |
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{ |
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result = new LdcDecimal(new decimal(lo, mid, hi, isNegative != 0, (byte)scale)); |
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return true; |
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} |
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} |
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return false; |
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} |
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protected internal override void VisitLdObj(LdObj inst) |
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{ |
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base.VisitLdObj(inst); |
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EarlyExpressionTransforms.LdObjToLdLoc(inst, context); |
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} |
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protected internal override void VisitStObj(StObj inst) |
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{ |
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base.VisitStObj(inst); |
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if (EarlyExpressionTransforms.StObjToStLoc(inst, context)) { |
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context.RequestRerun(); |
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return; |
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} |
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TransformAssignment.HandleStObjCompoundAssign(inst, context); |
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} |
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protected internal override void VisitIfInstruction(IfInstruction inst) |
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{ |
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inst.TrueInst.AcceptVisitor(this); |
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inst.FalseInst.AcceptVisitor(this); |
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inst = HandleConditionalOperator(inst); |
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// Bring LogicAnd/LogicOr into their canonical forms: |
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// if (cond) ldc.i4 0 else RHS --> if (!cond) RHS else ldc.i4 0 |
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// if (cond) RHS else ldc.i4 1 --> if (!cond) ldc.i4 1 else RHS |
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// Be careful: when both LHS and RHS are the constant 1, we must not |
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// swap the arguments as it would lead to an infinite transform loop. |
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if (inst.TrueInst.MatchLdcI4(0) && !inst.FalseInst.MatchLdcI4(0) |
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|| inst.FalseInst.MatchLdcI4(1) && !inst.TrueInst.MatchLdcI4(1)) |
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{ |
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context.Step("canonicalize logic and/or", inst); |
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var t = inst.TrueInst; |
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inst.TrueInst = inst.FalseInst; |
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inst.FalseInst = t; |
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inst.Condition = Comp.LogicNot(inst.Condition); |
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} |
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// Process condition after our potential modifications. |
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inst.Condition.AcceptVisitor(this); |
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if (new NullableLiftingTransform(context).Run(inst)) |
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return; |
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} |
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IfInstruction HandleConditionalOperator(IfInstruction inst) |
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{ |
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// if (cond) stloc (A, V1) else stloc (A, V2) --> stloc (A, if (cond) V1 else V2) |
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Block trueInst = inst.TrueInst as Block; |
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if (trueInst == null || trueInst.Instructions.Count != 1) |
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return inst; |
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Block falseInst = inst.FalseInst as Block; |
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if (falseInst == null || falseInst.Instructions.Count != 1) |
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return inst; |
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ILVariable v; |
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ILInstruction value1, value2; |
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if (trueInst.Instructions[0].MatchStLoc(out v, out value1) && falseInst.Instructions[0].MatchStLoc(v, out value2)) { |
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context.Step("conditional operator", inst); |
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var newIf = new IfInstruction(Comp.LogicNot(inst.Condition), value2, value1); |
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newIf.ILRange = inst.ILRange; |
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inst.ReplaceWith(new StLoc(v, newIf)); |
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context.RequestRerun(); // trigger potential inlining of the newly created StLoc |
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return newIf; |
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} |
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return inst; |
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} |
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protected internal override void VisitBinaryNumericInstruction(BinaryNumericInstruction inst) |
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{ |
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base.VisitBinaryNumericInstruction(inst); |
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switch (inst.Operator) { |
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case BinaryNumericOperator.ShiftLeft: |
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case BinaryNumericOperator.ShiftRight: |
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if (inst.Right.MatchBinaryNumericInstruction(BinaryNumericOperator.BitAnd, out var lhs, out var rhs) |
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&& rhs.MatchLdcI4(inst.ResultType == StackType.I8 ? 63 : 31)) |
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{ |
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// a << (b & 31) => a << b |
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context.Step("Combine bit.and into shift", inst); |
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inst.Right = lhs; |
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} |
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break; |
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} |
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} |
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protected internal override void VisitTryCatchHandler(TryCatchHandler inst) |
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{ |
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base.VisitTryCatchHandler(inst); |
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if (inst.Filter is BlockContainer filterContainer && filterContainer.Blocks.Count == 1) { |
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TransformCatchWhen(inst, filterContainer.EntryPoint); |
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} |
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if (inst.Body is BlockContainer catchContainer) |
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TransformCatchVariable(inst, catchContainer.EntryPoint); |
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} |
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/// <summary> |
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/// Transform local exception variable. |
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/// </summary> |
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void TransformCatchVariable(TryCatchHandler handler, Block entryPoint) |
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{ |
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if (!entryPoint.Instructions[0].MatchStLoc(out var exceptionVar, out var exceptionSlotLoad)) |
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return; |
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if (!exceptionVar.IsSingleDefinition || exceptionVar.Kind != VariableKind.Local) |
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return; |
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if (!exceptionSlotLoad.MatchLdLoc(handler.Variable) || !handler.Variable.IsSingleDefinition || handler.Variable.LoadCount != 1) |
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return; |
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handler.Variable = exceptionVar; |
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exceptionVar.Kind = VariableKind.Exception; |
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entryPoint.Instructions.RemoveAt(0); |
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} |
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/// <summary> |
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/// Inline condition from catch-when condition BlockContainer, if possible. |
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/// </summary> |
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void TransformCatchWhen(TryCatchHandler handler, Block entryPoint) |
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{ |
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TransformCatchVariable(handler, entryPoint); |
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if (entryPoint.Instructions.Count == 1 && entryPoint.Instructions[0].MatchLeave(out _, out var condition)) { |
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handler.Filter = condition; |
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} |
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} |
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} |
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}
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