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path: root/ICSharpCode.Decompiler/ILAst/SimpleControlFlow.cs
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-rw-r--r--ICSharpCode.Decompiler/ILAst/SimpleControlFlow.cs376
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diff --git a/ICSharpCode.Decompiler/ILAst/SimpleControlFlow.cs b/ICSharpCode.Decompiler/ILAst/SimpleControlFlow.cs
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--- a/ICSharpCode.Decompiler/ILAst/SimpleControlFlow.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.Diagnostics;
-using System.Linq;
-
-using Mono.Cecil;
-
-namespace ICSharpCode.Decompiler.ILAst
-{
- public class SimpleControlFlow
- {
- Dictionary<ILLabel, int> labelGlobalRefCount = new Dictionary<ILLabel, int>();
- Dictionary<ILLabel, ILBasicBlock> labelToBasicBlock = new Dictionary<ILLabel, ILBasicBlock>();
-
- DecompilerContext context;
- TypeSystem typeSystem;
-
- public SimpleControlFlow(DecompilerContext context, ILBlock method)
- {
- this.context = context;
- typeSystem = context.CurrentMethod.Module.TypeSystem;
-
- foreach(ILLabel target in method.GetSelfAndChildrenRecursive<ILExpression>(e => e.IsBranch()).SelectMany(e => e.GetBranchTargets())) {
- labelGlobalRefCount[target] = labelGlobalRefCount.GetOrDefault(target) + 1;
- }
- foreach(ILBasicBlock bb in method.GetSelfAndChildrenRecursive<ILBasicBlock>()) {
- foreach(ILLabel label in bb.GetChildren().OfType<ILLabel>()) {
- labelToBasicBlock[label] = bb;
- }
- }
- }
-
- public bool SimplifyTernaryOperator(List<ILNode> body, ILBasicBlock head, int pos)
- {
- Debug.Assert(body.Contains(head));
-
- ILExpression condExpr;
- ILLabel trueLabel;
- ILLabel falseLabel;
- ILVariable trueLocVar = null;
- ILExpression trueExpr;
- ILLabel trueFall;
- ILVariable falseLocVar = null;
- ILExpression falseExpr;
- ILLabel falseFall;
- object unused;
-
- if (head.MatchLastAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel) &&
- labelGlobalRefCount[trueLabel] == 1 &&
- labelGlobalRefCount[falseLabel] == 1 &&
- ((labelToBasicBlock[trueLabel].MatchSingleAndBr(ILCode.Stloc, out trueLocVar, out trueExpr, out trueFall) &&
- labelToBasicBlock[falseLabel].MatchSingleAndBr(ILCode.Stloc, out falseLocVar, out falseExpr, out falseFall) &&
- trueLocVar == falseLocVar && trueFall == falseFall) ||
- (labelToBasicBlock[trueLabel].MatchSingle(ILCode.Ret, out unused, out trueExpr) &&
- labelToBasicBlock[falseLabel].MatchSingle(ILCode.Ret, out unused, out falseExpr))) &&
- body.Contains(labelToBasicBlock[trueLabel]) &&
- body.Contains(labelToBasicBlock[falseLabel])
- )
- {
- bool isStloc = trueLocVar != null;
- ILCode opCode = isStloc ? ILCode.Stloc : ILCode.Ret;
- TypeReference retType = isStloc ? trueLocVar.Type : context.CurrentMethod.ReturnType;
- bool retTypeIsBoolean = TypeAnalysis.IsBoolean(retType);
- int leftBoolVal;
- int rightBoolVal;
- ILExpression newExpr;
- // a ? true:false is equivalent to a
- // a ? false:true is equivalent to !a
- // a ? true : b is equivalent to a || b
- // a ? b : true is equivalent to !a || b
- // a ? b : false is equivalent to a && b
- // a ? false : b is equivalent to !a && b
- if (retTypeIsBoolean &&
- trueExpr.Match(ILCode.Ldc_I4, out leftBoolVal) &&
- falseExpr.Match(ILCode.Ldc_I4, out rightBoolVal) &&
- ((leftBoolVal != 0 && rightBoolVal == 0) || (leftBoolVal == 0 && rightBoolVal != 0))
- )
- {
- // It can be expressed as trivilal expression
- if (leftBoolVal != 0) {
- newExpr = condExpr;
- } else {
- newExpr = new ILExpression(ILCode.LogicNot, null, condExpr) { InferredType = typeSystem.Boolean };
- }
- } else if ((retTypeIsBoolean || TypeAnalysis.IsBoolean(falseExpr.InferredType)) && trueExpr.Match(ILCode.Ldc_I4, out leftBoolVal) && (leftBoolVal == 0 || leftBoolVal == 1)) {
- // It can be expressed as logical expression
- if (leftBoolVal != 0) {
- newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, condExpr, falseExpr);
- } else {
- newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, new ILExpression(ILCode.LogicNot, null, condExpr), falseExpr);
- }
- } else if ((retTypeIsBoolean || TypeAnalysis.IsBoolean(trueExpr.InferredType)) && falseExpr.Match(ILCode.Ldc_I4, out rightBoolVal) && (rightBoolVal == 0 || rightBoolVal == 1)) {
- // It can be expressed as logical expression
- if (rightBoolVal != 0) {
- newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, new ILExpression(ILCode.LogicNot, null, condExpr), trueExpr);
- } else {
- newExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, condExpr, trueExpr);
- }
- } else {
- // Ternary operator tends to create long complicated return statements
- if (opCode == ILCode.Ret)
- return false;
-
- // Only simplify generated variables
- if (opCode == ILCode.Stloc && !trueLocVar.IsGenerated)
- return false;
-
- // Create ternary expression
- newExpr = new ILExpression(ILCode.TernaryOp, null, condExpr, trueExpr, falseExpr);
- }
-
- head.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
- head.Body.Add(new ILExpression(opCode, trueLocVar, newExpr));
- if (isStloc)
- head.Body.Add(new ILExpression(ILCode.Br, trueFall));
-
- // Remove the old basic blocks
- body.RemoveOrThrow(labelToBasicBlock[trueLabel]);
- body.RemoveOrThrow(labelToBasicBlock[falseLabel]);
-
- return true;
- }
- return false;
- }
-
- public bool SimplifyNullCoalescing(List<ILNode> body, ILBasicBlock head, int pos)
- {
- // ...
- // v = ldloc(leftVar)
- // brtrue(endBBLabel, ldloc(leftVar))
- // br(rightBBLabel)
- //
- // rightBBLabel:
- // v = rightExpr
- // br(endBBLabel)
- // ...
- // =>
- // ...
- // v = NullCoalescing(ldloc(leftVar), rightExpr)
- // br(endBBLabel)
-
- ILVariable v, v2;
- ILExpression leftExpr, leftExpr2;
- ILVariable leftVar;
- ILLabel endBBLabel, endBBLabel2;
- ILLabel rightBBLabel;
- ILBasicBlock rightBB;
- ILExpression rightExpr;
- if (head.Body.Count >= 3 &&
- head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out v, out leftExpr) &&
- leftExpr.Match(ILCode.Ldloc, out leftVar) &&
- head.MatchLastAndBr(ILCode.Brtrue, out endBBLabel, out leftExpr2, out rightBBLabel) &&
- leftExpr2.MatchLdloc(leftVar) &&
- labelToBasicBlock.TryGetValue(rightBBLabel, out rightBB) &&
- rightBB.MatchSingleAndBr(ILCode.Stloc, out v2, out rightExpr, out endBBLabel2) &&
- v == v2 &&
- endBBLabel == endBBLabel2 &&
- labelGlobalRefCount.GetOrDefault(rightBBLabel) == 1 &&
- body.Contains(rightBB)
- )
- {
- head.Body.RemoveTail(ILCode.Stloc, ILCode.Brtrue, ILCode.Br);
- head.Body.Add(new ILExpression(ILCode.Stloc, v, new ILExpression(ILCode.NullCoalescing, null, leftExpr, rightExpr)));
- head.Body.Add(new ILExpression(ILCode.Br, endBBLabel));
-
- body.RemoveOrThrow(labelToBasicBlock[rightBBLabel]);
- return true;
- }
- return false;
- }
-
- public bool SimplifyShortCircuit(List<ILNode> body, ILBasicBlock head, int pos)
- {
- Debug.Assert(body.Contains(head));
-
- ILExpression condExpr;
- ILLabel trueLabel;
- ILLabel falseLabel;
- if(head.MatchLastAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel)) {
- for (int pass = 0; pass < 2; pass++) {
-
- // On the second pass, swap labels and negate expression of the first branch
- // It is slightly ugly, but much better then copy-pasting this whole block
- ILLabel nextLabel = (pass == 0) ? trueLabel : falseLabel;
- ILLabel otherLablel = (pass == 0) ? falseLabel : trueLabel;
- bool negate = (pass == 1);
-
- ILBasicBlock nextBasicBlock = labelToBasicBlock[nextLabel];
- ILExpression nextCondExpr;
- ILLabel nextTrueLablel;
- ILLabel nextFalseLabel;
- if (body.Contains(nextBasicBlock) &&
- nextBasicBlock != head &&
- labelGlobalRefCount[(ILLabel)nextBasicBlock.Body.First()] == 1 &&
- nextBasicBlock.MatchSingleAndBr(ILCode.Brtrue, out nextTrueLablel, out nextCondExpr, out nextFalseLabel) &&
- (otherLablel == nextFalseLabel || otherLablel == nextTrueLablel))
- {
- // Create short cicuit branch
- ILExpression logicExpr;
- if (otherLablel == nextFalseLabel) {
- logicExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicAnd, negate ? new ILExpression(ILCode.LogicNot, null, condExpr) : condExpr, nextCondExpr);
- } else {
- logicExpr = MakeLeftAssociativeShortCircuit(ILCode.LogicOr, negate ? condExpr : new ILExpression(ILCode.LogicNot, null, condExpr), nextCondExpr);
- }
- head.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
- head.Body.Add(new ILExpression(ILCode.Brtrue, nextTrueLablel, logicExpr));
- head.Body.Add(new ILExpression(ILCode.Br, nextFalseLabel));
-
- // Remove the inlined branch from scope
- body.RemoveOrThrow(nextBasicBlock);
-
- return true;
- }
- }
- }
- return false;
- }
-
- public bool SimplifyCustomShortCircuit(List<ILNode> body, ILBasicBlock head, int pos)
- {
- Debug.Assert(body.Contains(head));
-
- // --- looking for the following pattern ---
- // stloc(targetVar, leftVar)
- // brtrue(exitLabel, call(op_False, leftVar)
- // br(followingBlock)
- //
- // FollowingBlock:
- // stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
- // br(exitLabel)
- // ---
-
- if (head.Body.Count < 3)
- return false;
-
- // looking for:
- // stloc(targetVar, leftVar)
- ILVariable targetVar;
- ILExpression targetVarInitExpr;
- if (!head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out targetVar, out targetVarInitExpr))
- return false;
-
- ILVariable leftVar;
- if (!targetVarInitExpr.Match(ILCode.Ldloc, out leftVar))
- return false;
-
- // looking for:
- // brtrue(exitLabel, call(op_False, leftVar)
- // br(followingBlock)
- ILExpression callExpr;
- ILLabel exitLabel;
- ILLabel followingBlock;
- if(!head.MatchLastAndBr(ILCode.Brtrue, out exitLabel, out callExpr, out followingBlock))
- return false;
-
- if (labelGlobalRefCount[followingBlock] > 1)
- return false;
-
- MethodReference opFalse;
- ILExpression opFalseArg;
- if (!callExpr.Match(ILCode.Call, out opFalse, out opFalseArg))
- return false;
-
- // ignore operators other than op_False and op_True
- if (opFalse.Name != "op_False" && opFalse.Name != "op_True")
- return false;
-
- if (!opFalseArg.MatchLdloc(leftVar))
- return false;
-
- ILBasicBlock followingBasicBlock = labelToBasicBlock[followingBlock];
-
- // FollowingBlock:
- // stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
- // br(exitLabel)
- ILVariable _targetVar;
- ILExpression opBitwiseCallExpr;
- ILLabel _exitLabel;
- if (!followingBasicBlock.MatchSingleAndBr(ILCode.Stloc, out _targetVar, out opBitwiseCallExpr, out _exitLabel))
- return false;
-
- if (_targetVar != targetVar || exitLabel != _exitLabel)
- return false;
-
- MethodReference opBitwise;
- ILExpression leftVarExpression;
- ILExpression rightExpression;
- if (!opBitwiseCallExpr.Match(ILCode.Call, out opBitwise, out leftVarExpression, out rightExpression))
- return false;
-
- if (!leftVarExpression.MatchLdloc(leftVar))
- return false;
-
- // ignore operators other than op_BitwiseAnd and op_BitwiseOr
- if (opBitwise.Name != "op_BitwiseAnd" && opBitwise.Name != "op_BitwiseOr")
- return false;
-
- // insert:
- // stloc(targetVar, LogicAnd(C::op_BitwiseAnd, leftVar, rightExpression)
- // br(exitLabel)
- ILCode op = opBitwise.Name == "op_BitwiseAnd" ? ILCode.LogicAnd : ILCode.LogicOr;
-
- if (op == ILCode.LogicAnd && opFalse.Name != "op_False")
- return false;
-
- if (op == ILCode.LogicOr && opFalse.Name != "op_True")
- return false;
-
- ILExpression shortCircuitExpr = MakeLeftAssociativeShortCircuit(op, opFalseArg, rightExpression);
- shortCircuitExpr.Operand = opBitwise;
-
- head.Body.RemoveTail(ILCode.Stloc, ILCode.Brtrue, ILCode.Br);
- head.Body.Add(new ILExpression(ILCode.Stloc, targetVar, shortCircuitExpr));
- head.Body.Add(new ILExpression(ILCode.Br, exitLabel));
- body.Remove(followingBasicBlock);
-
- return true;
- }
-
- ILExpression MakeLeftAssociativeShortCircuit(ILCode code, ILExpression left, ILExpression right)
- {
- // Assuming that the inputs are already left associative
- if (right.Match(code)) {
- // Find the leftmost logical expression
- ILExpression current = right;
- while(current.Arguments[0].Match(code))
- current = current.Arguments[0];
- current.Arguments[0] = new ILExpression(code, null, left, current.Arguments[0]) { InferredType = typeSystem.Boolean };
- return right;
- } else {
- return new ILExpression(code, null, left, right) { InferredType = typeSystem.Boolean };
- }
- }
-
- public bool JoinBasicBlocks(List<ILNode> body, ILBasicBlock head, int pos)
- {
- ILLabel nextLabel;
- ILBasicBlock nextBB;
- if (!head.Body.ElementAtOrDefault(head.Body.Count - 2).IsConditionalControlFlow() &&
- head.Body.Last().Match(ILCode.Br, out nextLabel) &&
- labelGlobalRefCount[nextLabel] == 1 &&
- labelToBasicBlock.TryGetValue(nextLabel, out nextBB) &&
- body.Contains(nextBB) &&
- nextBB.Body.First() == nextLabel &&
- !nextBB.Body.OfType<ILTryCatchBlock>().Any()
- )
- {
- head.Body.RemoveTail(ILCode.Br);
- nextBB.Body.RemoveAt(0); // Remove label
- head.Body.AddRange(nextBB.Body);
-
- body.RemoveOrThrow(nextBB);
- return true;
- }
- return false;
- }
- }
-}
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