private DataFlowAnalysisResult <TAnalysisResult, TAbstractAnalysisValue> Run(ControlFlowGraph cfg)
{
var resultBuilder = new DataFlowAnalysisResultBuilder <TAnalysisData>();
// Add each basic block to the result.
foreach (var block in cfg.Blocks)
{
resultBuilder.Add(block);
}
var worklist = new Queue <BasicBlock>();
var entry = GetEntry(cfg);
// Initialize the input of the initial block
// with the default abstract value of the domain.
UpdateInput(resultBuilder, entry, AnalysisDomain.Bottom);
// Add the entry block to the worklist.
worklist.Enqueue(entry);
while (worklist.Count > 0)
{
// Get the next block to process
// and its associated result.
var block = worklist.Dequeue();
// Get the outputs of all predecessor blocks of the current block.
var inputs = GetPredecessors(block).Select(b => GetOutput(resultBuilder[b]));
// Merge all the outputs to get the new input of the current block.
var input = AnalysisDomain.Merge(inputs);
// Merge might return one of the original input values if only one of them is a valid non-null value.
if (inputs.Any(i => ReferenceEquals(input, i)))
{
input = AnalysisDomain.Clone(input);
}
// Temporary workaround due to lack of *real* CFG
// TODO: Remove the below if statement once we move to compiler's CFG
// https://github.com/dotnet/roslyn-analyzers/issues/1567
if (block.Kind == BasicBlockKind.Exit &&
OperationVisitor.MergedAnalysisDataAtReturnStatements != null)
{
input = AnalysisDomain.Merge(input, OperationVisitor.MergedAnalysisDataAtReturnStatements);
}
// Compare the previous input with the new input.
var compare = AnalysisDomain.Compare(GetInput(resultBuilder[block]), input);
// The newly computed abstract values for each basic block
// must be always greater or equal than the previous value
// to ensure termination.
Debug.Assert(compare <= 0, "The newly computed abstract value must be greater or equal than the previous one.");
// Is old input value < new input value ?
if (compare < 0 || block.Kind == BasicBlockKind.Entry)
{
// The newly computed value is greater than the previous value,
// so we need to update the current block result's
// input values with the new ones.
UpdateInput(resultBuilder, block, AnalysisDomain.Clone(input));
// Flow the new input through the block to get a new output.
var output = Flow(block, input);
// Compare the previous output with the new output.
compare = AnalysisDomain.Compare(GetOutput(resultBuilder[block]), output);
// The newly computed abstract values for each basic block
// must be always greater or equal than the previous value
// to ensure termination.
Debug.Assert(compare <= 0, "The newly computed abstract value must be greater or equal than the previous one.");
// Is old output value < new output value ?
if (compare < 0 || block.Kind == BasicBlockKind.Entry)
{
// The newly computed value is greater than the previous value,
// so we need to update the current block result's
// output values with the new ones.
UpdateOutput(resultBuilder, block, output);
// Since the new output value is different than the previous one,
// we need to propagate it to all the successor blocks of the current block.
EnqueueRange(worklist, GetSuccessors(block));
}
}
}
return(resultBuilder.ToResult(ToResult, OperationVisitor.GetStateMap(),
OperationVisitor.GetPredicateValueKindMap(), OperationVisitor.GetMergedDataForUnhandledThrowOperations(),
cfg, OperationVisitor.ValueDomain.UnknownOrMayBeValue));
}