private bool CheckForChangesInFooter(
ControlFlowGraphEditTransaction <TInstruction> transaction,
ControlFlowNode <TInstruction> node)
{
bool hasChanges = false;
// Most instructions will have <= 2 successors.
// - Immediate fallthrough successor or unconditional branch target.
// - A single conditional branch target.
// The only exception will be switch-like instructions.
// Therefore we start off by renting a buffer of at least two elements.
var arrayPool = ArrayPool <SuccessorInfo> .Shared;
// Verify that our buffer has enough elements.
int successorCount = SuccessorResolver.GetSuccessorsCount(node.Contents.Footer);
var successorsBuffer = arrayPool.Rent(successorCount);
try
{
// Get new successors.
var successorBufferSlice = new Span <SuccessorInfo>(successorsBuffer, 0, successorCount);
int actualSuccessorCount = SuccessorResolver.GetSuccessors(node.Contents.Footer, successorBufferSlice);
if (actualSuccessorCount > successorCount)
{
throw new InvalidOperationException();
}
// Group successors by type:
long?fallthroughSuccessor = null;
var conditionalSuccessors = new List <long>();
var abnormalSuccessors = new List <long>();
for (int i = 0; i < actualSuccessorCount; i++)
{
var successor = successorsBuffer[i];
switch (successor.EdgeType)
{
case ControlFlowEdgeType.FallThrough:
if (fallthroughSuccessor.HasValue)
{
throw new ArgumentException("Instruction has multiple fallthrough successors.");
}
else
{
fallthroughSuccessor = successor.DestinationAddress;
}
break;
case ControlFlowEdgeType.Conditional:
conditionalSuccessors.Add(successor.DestinationAddress);
break;
case ControlFlowEdgeType.Abnormal:
abnormalSuccessors.Add(successor.DestinationAddress);
break;
default:
throw new ArgumentOutOfRangeException();
}
}
// Check if there are any changes to the outgoing edges.
hasChanges |= CheckIfFallThroughChanged(transaction, node, fallthroughSuccessor);
hasChanges |= CheckIfAdjacencyListChanged(transaction, node.ConditionalEdges, conditionalSuccessors);
hasChanges |= CheckIfAdjacencyListChanged(transaction, node.AbnormalEdges, abnormalSuccessors);
}
finally
{
arrayPool.Return(successorsBuffer);
}
return(hasChanges);
}
private bool CheckForChangesInBasicBlock(ControlFlowGraphEditTransaction <TInstruction> transaction, ControlFlowNode <TInstruction> node)
{
bool hasChanges = false;
// Most instructions will have <= 2 successors.
// - Immediate fallthrough successor or unconditional branch target.
// - A single conditional branch target.
// The only exception will be switch-like instructions.
// Therefore we start off by renting a buffer of at least two elements.
var arrayPool = ArrayPool <SuccessorInfo> .Shared;
var successorsBuffer = arrayPool.Rent(2);
try
{
var architecture = ControlFlowGraph.Architecture;
// Skip last instruction (footer), since it is processed somewhere else.
for (int i = 0; i < node.Contents.Instructions.Count - 1; i++)
{
// Optimization: we assume the architecture has a faster implementation for categorizing instructions
// as instructions that influence the basic block (i.e. branches) than the successor resolver itself.
var instruction = node.Contents.Instructions[i];
var flowControl = architecture.GetFlowControl(instruction);
if (SplitsBasicBlock(flowControl))
{
long offset = architecture.GetOffset(instruction);
// Split the node after the instruction.
var splitAction = new SplitNodeAction <TInstruction>(offset + architecture.GetSize(instruction));
transaction.EnqueueAction(splitAction);
// Remove the fallthrough edge generated by ControlFlowNode<T>.SplitAtIndex.
transaction.EnqueueAction(new UpdateFallThroughAction <TInstruction>(offset, null));
// Verify that our buffer has enough elements.
int successorCount = SuccessorResolver.GetSuccessorsCount(instruction);
if (successorsBuffer.Length < successorCount)
{
arrayPool.Return(successorsBuffer);
successorsBuffer = arrayPool.Rent(successorCount);
}
// Get new successors.
var successorBufferSlice = new Span <SuccessorInfo>(successorsBuffer, 0, successorCount);
int actualSuccessorCount = SuccessorResolver.GetSuccessors(instruction, successorBufferSlice);
if (actualSuccessorCount > successorCount)
{
throw new InvalidOperationException();
}
for (int j = 0; j < actualSuccessorCount; j++)
{
var successor = successorsBuffer[j];
IControlFlowGraphEditAction <TInstruction> action;
if (successor.EdgeType == ControlFlowEdgeType.FallThrough)
{
action = new UpdateFallThroughAction <TInstruction>(
offset,
successor.DestinationAddress);
}
else
{
action = new AddEdgeAction <TInstruction>(
offset,
successor.DestinationAddress,
successor.EdgeType);
}
transaction.EnqueueAction(action);
}
hasChanges = true;
}
}
}
finally
{
arrayPool.Return(successorsBuffer);
}
return(hasChanges);
}
