Esempio n. 1
0
        /// <summary>
        /// Get the first expression to be excecuted if the instruction pointer is at the start of the given node.
        /// Try blocks may not be entered in any way.  If possible, the try block is returned as the node to be executed.
        /// </summary>
        ILNode Enter(ILNode node, HashSet <ILNode> visitedNodes)
        {
            if (node == null)
            {
                throw new ArgumentNullException();
            }

            if (!visitedNodes.Add(node))
            {
                return(null);                 // Infinite loop
            }
            ILLabel label = node as ILLabel;

            if (label != null)
            {
                return(Exit(label, visitedNodes));
            }

            ILExpression expr = node as ILExpression;

            if (expr != null)
            {
                if (expr.Code == ILCode.Br || expr.Code == ILCode.Leave)
                {
                    ILLabel target = (ILLabel)expr.Operand;
                    // Early exit - same try-block
                    if (GetParents(expr).OfType <ILTryCatchBlock>().FirstOrDefault() == GetParents(target).OfType <ILTryCatchBlock>().FirstOrDefault())
                    {
                        return(Enter(target, visitedNodes));
                    }
                    // Make sure we are not entering any try-block
                    var srcTryBlocks = GetParents(expr).OfType <ILTryCatchBlock>().Reverse().ToList();
                    var dstTryBlocks = GetParents(target).OfType <ILTryCatchBlock>().Reverse().ToList();
                    // Skip blocks that we are already in
                    int i = 0;
                    while (i < srcTryBlocks.Count && i < dstTryBlocks.Count && srcTryBlocks[i] == dstTryBlocks[i])
                    {
                        i++;
                    }
                    if (i == dstTryBlocks.Count)
                    {
                        return(Enter(target, visitedNodes));
                    }
                    else
                    {
                        ILTryCatchBlock dstTryBlock = dstTryBlocks[i];
                        // Check that the goto points to the start
                        ILTryCatchBlock current = dstTryBlock;
                        while (current != null)
                        {
                            foreach (ILNode n in current.TryBlock.Body)
                            {
                                if (n is ILLabel)
                                {
                                    if (n == target)
                                    {
                                        return(dstTryBlock);
                                    }
                                }
                                else if (!n.Match(ILCode.Nop))
                                {
                                    current = n as ILTryCatchBlock;
                                    break;
                                }
                            }
                        }
                        return(null);
                    }
                }
                else if (expr.Code == ILCode.Nop)
                {
                    return(Exit(expr, visitedNodes));
                }
                else if (expr.Code == ILCode.LoopOrSwitchBreak)
                {
                    ILNode breakBlock = GetParents(expr).First(n => n is ILWhileLoop || n is ILSwitch);
                    return(Exit(breakBlock, new HashSet <ILNode>()
                    {
                        expr
                    }));
                }
                else if (expr.Code == ILCode.LoopContinue)
                {
                    ILNode continueBlock = GetParents(expr).First(n => n is ILWhileLoop);
                    return(Enter(continueBlock, new HashSet <ILNode>()
                    {
                        expr
                    }));
                }
                else
                {
                    return(expr);
                }
            }

            ILBlock block = node as ILBlock;

            if (block != null)
            {
                if (block.EntryGoto != null)
                {
                    return(Enter(block.EntryGoto, visitedNodes));
                }
                else if (block.Body.Count > 0)
                {
                    return(Enter(block.Body[0], visitedNodes));
                }
                else
                {
                    return(Exit(block, visitedNodes));
                }
            }

            ILCondition cond = node as ILCondition;

            if (cond != null)
            {
                return(cond.Condition);
            }

            ILWhileLoop loop = node as ILWhileLoop;

            if (loop != null)
            {
                if (loop.Condition != null)
                {
                    return(loop.Condition);
                }
                else
                {
                    return(Enter(loop.BodyBlock, visitedNodes));
                }
            }

            ILTryCatchBlock tryCatch = node as ILTryCatchBlock;

            if (tryCatch != null)
            {
                return(tryCatch);
            }

            ILSwitch ilSwitch = node as ILSwitch;

            if (ilSwitch != null)
            {
                return(ilSwitch.Condition);
            }

            throw new NotSupportedException(node.GetType().ToString());
        }
Esempio n. 2
0
        List <ILNode> FindLoops(HashSet <ControlFlowNode> scope, ControlFlowNode entryPoint, bool excludeEntryPoint)
        {
            List <ILNode> result = new List <ILNode>();

            // Do not modify entry data
            scope = new HashSet <ControlFlowNode>(scope);

            Queue <ControlFlowNode> agenda = new Queue <ControlFlowNode>();

            agenda.Enqueue(entryPoint);
            while (agenda.Count > 0)
            {
                ControlFlowNode node = agenda.Dequeue();

                // If the node is a loop header
                if (scope.Contains(node) &&
                    node.DominanceFrontier.Contains(node) &&
                    (node != entryPoint || !excludeEntryPoint))
                {
                    HashSet <ControlFlowNode> loopContents = FindLoopContent(scope, node);

                    // If the first expression is a loop condition
                    ILBasicBlock basicBlock = (ILBasicBlock)node.UserData;
                    ILExpression condExpr;
                    ILLabel      trueLabel;
                    ILLabel      falseLabel;
                    // It has to be just brtrue - any preceding code would introduce goto
                    if (basicBlock.MatchSingleAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel))
                    {
                        ControlFlowNode trueTarget;
                        labelToCfNode.TryGetValue(trueLabel, out trueTarget);
                        ControlFlowNode falseTarget;
                        labelToCfNode.TryGetValue(falseLabel, out falseTarget);

                        // If one point inside the loop and the other outside
                        if ((!loopContents.Contains(trueTarget) && loopContents.Contains(falseTarget)) ||
                            (loopContents.Contains(trueTarget) && !loopContents.Contains(falseTarget)))
                        {
                            loopContents.RemoveOrThrow(node);
                            scope.RemoveOrThrow(node);

                            // If false means enter the loop
                            if (loopContents.Contains(falseTarget) || falseTarget == node)
                            {
                                // Negate the condition
                                condExpr = new ILExpression(ILCode.LogicNot, null, condExpr);
                                ILLabel tmp = trueLabel;
                                trueLabel  = falseLabel;
                                falseLabel = tmp;
                            }

                            ControlFlowNode postLoopTarget;
                            labelToCfNode.TryGetValue(falseLabel, out postLoopTarget);
                            if (postLoopTarget != null)
                            {
                                // Pull more nodes into the loop
                                HashSet <ControlFlowNode> postLoopContents = FindDominatedNodes(scope, postLoopTarget);
                                var pullIn = scope.Except(postLoopContents).Where(n => node.Dominates(n));
                                loopContents.UnionWith(pullIn);
                            }

                            // Use loop to implement the brtrue
                            var         tail = basicBlock.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
                            ILWhileLoop whileLoop;
                            basicBlock.Body.Add(whileLoop = new ILWhileLoop()
                            {
                                Condition = condExpr,
                                BodyBlock = new ILBlock()
                                {
                                    EntryGoto = new ILExpression(ILCode.Br, trueLabel),
                                    Body      = FindLoops(loopContents, node, false)
                                }
                            });
                            whileLoop.ILRanges.AddRange(tail[0].ILRanges);                              // no recursive add
                            tail[1].AddSelfAndChildrenRecursiveILRanges(whileLoop.ILRanges);
                            basicBlock.Body.Add(new ILExpression(ILCode.Br, falseLabel));
                            result.Add(basicBlock);

                            scope.ExceptWith(loopContents);
                        }
                    }

                    // Fallback method: while(true)
                    if (scope.Contains(node))
                    {
                        result.Add(new ILBasicBlock()
                        {
                            Body = new List <ILNode>()
                            {
                                new ILLabel()
                                {
                                    Name = "Loop_" + (nextLabelIndex++).ToString()
                                },
                                new ILWhileLoop()
                                {
                                    BodyBlock = new ILBlock()
                                    {
                                        EntryGoto = new ILExpression(ILCode.Br, (ILLabel)basicBlock.Body.First()),
                                        Body      = FindLoops(loopContents, node, true)
                                    }
                                },
                            },
                        });

                        scope.ExceptWith(loopContents);
                    }
                }

                // Using the dominator tree should ensure we find the the widest loop first
                foreach (var child in node.DominatorTreeChildren)
                {
                    agenda.Enqueue(child);
                }
            }

            // Add whatever is left
            foreach (var node in scope)
            {
                result.Add((ILNode)node.UserData);
            }
            scope.Clear();

            return(result);
        }