mirror of https://github.com/icsharpcode/ILSpy.git
David Srbecký
15 years ago
3 changed files with 237 additions and 224 deletions
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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
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// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
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using System; |
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using System.Collections.Generic; |
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using System.Diagnostics; |
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using System.Linq; |
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using Mono.Cecil; |
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namespace ICSharpCode.Decompiler.ILAst |
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{ |
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public class SimpleControlFlow |
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{ |
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Dictionary<ILLabel, int> labelGlobalRefCount = new Dictionary<ILLabel, int>(); |
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Dictionary<ILLabel, ILBasicBlock> labelToBasicBlock = new Dictionary<ILLabel, ILBasicBlock>(); |
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DecompilerContext context; |
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TypeSystem typeSystem; |
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public SimpleControlFlow(DecompilerContext context, ILBlock method) |
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{ |
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this.context = context; |
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this.typeSystem = context.CurrentMethod.Module.TypeSystem; |
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foreach(ILLabel target in method.GetSelfAndChildrenRecursive<ILExpression>(e => e.IsBranch()).SelectMany(e => e.GetBranchTargets())) { |
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labelGlobalRefCount[target] = labelGlobalRefCount.GetOrDefault(target) + 1; |
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} |
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foreach(ILBasicBlock bb in method.GetSelfAndChildrenRecursive<ILBasicBlock>()) { |
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foreach(ILLabel label in bb.GetChildren().OfType<ILLabel>()) { |
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labelToBasicBlock[label] = bb; |
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} |
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} |
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} |
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public bool SimplifyTernaryOperator(List<ILNode> body, ILBasicBlock head, int pos) |
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{ |
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Debug.Assert(body.Contains(head)); |
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ILExpression condExpr; |
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ILLabel trueLabel; |
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ILLabel falseLabel; |
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ILVariable trueLocVar = null; |
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ILExpression trueExpr; |
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ILLabel trueFall; |
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ILVariable falseLocVar = null; |
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ILExpression falseExpr; |
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ILLabel falseFall; |
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object unused; |
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if (head.MatchLast(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel) && |
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labelGlobalRefCount[trueLabel] == 1 && |
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labelGlobalRefCount[falseLabel] == 1 && |
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((labelToBasicBlock[trueLabel].MatchSingle(ILCode.Stloc, out trueLocVar, out trueExpr, out trueFall) && |
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labelToBasicBlock[falseLabel].MatchSingle(ILCode.Stloc, out falseLocVar, out falseExpr, out falseFall)) || |
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(labelToBasicBlock[trueLabel].MatchSingle(ILCode.Ret, out unused, out trueExpr, out trueFall) && |
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labelToBasicBlock[falseLabel].MatchSingle(ILCode.Ret, out unused, out falseExpr, out falseFall))) && |
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trueLocVar == falseLocVar && |
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trueFall == falseFall && |
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body.Contains(labelToBasicBlock[trueLabel]) && |
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body.Contains(labelToBasicBlock[falseLabel]) |
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) |
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{ |
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ILCode opCode = trueLocVar != null ? ILCode.Stloc : ILCode.Ret; |
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TypeReference retType = trueLocVar != null ? trueLocVar.Type : this.context.CurrentMethod.ReturnType; |
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int leftBoolVal; |
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int rightBoolVal; |
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ILExpression newExpr; |
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// a ? true:false is equivalent to a
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// a ? false:true is equivalent to !a
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// a ? true : b is equivalent to a || b
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// a ? b : true is equivalent to !a || b
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// a ? b : false is equivalent to a && b
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// a ? false : b is equivalent to !a && b
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if (retType == typeSystem.Boolean && |
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trueExpr.Match(ILCode.Ldc_I4, out leftBoolVal) && |
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falseExpr.Match(ILCode.Ldc_I4, out rightBoolVal) && |
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((leftBoolVal != 0 && rightBoolVal == 0) || (leftBoolVal == 0 && rightBoolVal != 0)) |
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) |
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{ |
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// It can be expressed as trivilal expression
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if (leftBoolVal != 0) { |
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newExpr = condExpr; |
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} else { |
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newExpr = new ILExpression(ILCode.LogicNot, null, condExpr); |
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} |
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} else if (retType == typeSystem.Boolean && trueExpr.Match(ILCode.Ldc_I4, out leftBoolVal)) { |
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// It can be expressed as logical expression
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if (leftBoolVal != 0) { |
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newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, condExpr, falseExpr); |
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} else { |
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newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, new ILExpression(ILCode.LogicNot, null, condExpr), falseExpr); |
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} |
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} else if (retType == typeSystem.Boolean && falseExpr.Match(ILCode.Ldc_I4, out rightBoolVal)) { |
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// It can be expressed as logical expression
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if (rightBoolVal != 0) { |
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newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, new ILExpression(ILCode.LogicNot, null, condExpr), trueExpr); |
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} else { |
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newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, condExpr, trueExpr); |
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} |
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} else { |
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// Ternary operator tends to create long complicated return statements
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if (opCode == ILCode.Ret) |
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return false; |
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// Only simplify generated variables
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if (opCode == ILCode.Stloc && !trueLocVar.IsGenerated) |
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return false; |
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// Create ternary expression
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newExpr = new ILExpression(ILCode.TernaryOp, null, condExpr, trueExpr, falseExpr); |
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} |
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head.Body[head.Body.Count - 1] = new ILExpression(opCode, trueLocVar, newExpr); |
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head.FallthoughGoto = trueFall != null ? new ILExpression(ILCode.Br, trueFall) : null; |
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// Remove the old basic blocks
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body.RemoveOrThrow(labelToBasicBlock[trueLabel]); |
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body.RemoveOrThrow(labelToBasicBlock[falseLabel]); |
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return true; |
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} |
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return false; |
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} |
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public bool SimplifyNullCoalescing(List<ILNode> body, ILBasicBlock head, int pos) |
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{ |
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// ...
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// v = ldloc(leftVar)
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// brtrue(endBBLabel, ldloc(leftVar))
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// br(rightBBLabel)
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//
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// rightBBLabel:
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// v = rightExpr
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// br(endBBLabel)
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// ...
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// =>
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// ...
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// v = NullCoalescing(ldloc(leftVar), rightExpr)
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// br(endBBLabel)
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ILVariable v, v2; |
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ILExpression leftExpr, leftExpr2; |
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ILVariable leftVar; |
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ILLabel endBBLabel, endBBLabel2; |
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ILLabel rightBBLabel; |
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ILBasicBlock rightBB; |
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ILExpression rightExpr; |
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if (head.Body.Count >= 2 && |
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head.Body[head.Body.Count - 2].Match(ILCode.Stloc, out v, out leftExpr) && |
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leftExpr.Match(ILCode.Ldloc, out leftVar) && |
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head.MatchLast(ILCode.Brtrue, out endBBLabel, out leftExpr2, out rightBBLabel) && |
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leftExpr2.Match(ILCode.Ldloc, leftVar) && |
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labelToBasicBlock.TryGetValue(rightBBLabel, out rightBB) && |
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rightBB.MatchSingle(ILCode.Stloc, out v2, out rightExpr, out endBBLabel2) && |
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v == v2 && |
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endBBLabel == endBBLabel2 && |
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labelGlobalRefCount.GetOrDefault(rightBBLabel) == 1 && |
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body.Contains(rightBB) |
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) |
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{ |
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head.Body[head.Body.Count - 2] = new ILExpression(ILCode.Stloc, v, new ILExpression(ILCode.NullCoalescing, null, leftExpr, rightExpr)); |
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head.Body.RemoveAt(head.Body.Count - 1); |
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head.FallthoughGoto = new ILExpression(ILCode.Br, endBBLabel); |
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body.RemoveOrThrow(labelToBasicBlock[rightBBLabel]); |
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return true; |
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} |
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return false; |
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} |
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public bool SimplifyShortCircuit(List<ILNode> body, ILBasicBlock head, int pos) |
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{ |
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Debug.Assert(body.Contains(head)); |
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ILExpression condExpr; |
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ILLabel trueLabel; |
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ILLabel falseLabel; |
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if(head.MatchLast(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel)) { |
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for (int pass = 0; pass < 2; pass++) { |
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// On the second pass, swap labels and negate expression of the first branch
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// It is slightly ugly, but much better then copy-pasting this whole block
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ILLabel nextLabel = (pass == 0) ? trueLabel : falseLabel; |
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ILLabel otherLablel = (pass == 0) ? falseLabel : trueLabel; |
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bool negate = (pass == 1); |
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ILBasicBlock nextBasicBlock = labelToBasicBlock[nextLabel]; |
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ILExpression nextCondExpr; |
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ILLabel nextTrueLablel; |
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ILLabel nextFalseLabel; |
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if (body.Contains(nextBasicBlock) && |
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nextBasicBlock != head && |
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labelGlobalRefCount[nextBasicBlock.EntryLabel] == 1 && |
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nextBasicBlock.MatchSingle(ILCode.Brtrue, out nextTrueLablel, out nextCondExpr, out nextFalseLabel) && |
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(otherLablel == nextFalseLabel || otherLablel == nextTrueLablel)) |
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{ |
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// Create short cicuit branch
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ILExpression logicExpr; |
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if (otherLablel == nextFalseLabel) { |
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logicExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, negate ? new ILExpression(ILCode.LogicNot, null, condExpr) : condExpr, nextCondExpr); |
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} else { |
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logicExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, negate ? condExpr : new ILExpression(ILCode.LogicNot, null, condExpr), nextCondExpr); |
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} |
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head.Body[head.Body.Count - 1] = new ILExpression(ILCode.Brtrue, nextTrueLablel, logicExpr); |
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head.FallthoughGoto = new ILExpression(ILCode.Br, nextFalseLabel); |
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// Remove the inlined branch from scope
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body.RemoveOrThrow(nextBasicBlock); |
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return true; |
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} |
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} |
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} |
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return false; |
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} |
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ILExpression MakeLeftAssociativeShortCircuit(ILCode code, ILExpression left, ILExpression right) |
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{ |
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// Assuming that the inputs are already left associative
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if (right.Match(code)) { |
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// Find the leftmost logical expression
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ILExpression current = right; |
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while(current.Arguments[0].Match(code)) |
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current = current.Arguments[0]; |
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current.Arguments[0] = new ILExpression(code, null, left, current.Arguments[0]); |
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return right; |
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} else { |
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return new ILExpression(code, null, left, right); |
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} |
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} |
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} |
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} |
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