/// <summary>
/// Creates a new loop info instance from the given
/// scc while checking for unique entry and exit blocks.
/// </summary>
/// <param name="scc">The scc.</param>
/// <returns>The resolved loop info instance.</returns>
public static LoopInfo Create(SCCs.SCC scc)
{
if (!TryCreate(scc, out var loopInfo))
{
throw new InvalidKernelOperationException();
}
return(loopInfo);
}
/// <summary>
/// Tries to create a new loop info instance from the given
/// scc while checking for unique entry and exit blocks.
/// </summary>
/// <param name="scc">The scc.</param>
/// <param name="loopInfo">The resolved loop info object (if any).</param>
/// <returns>True, if the resulting loop info object could be resolved.</returns>
public static bool TryCreate(SCCs.SCC scc, out LoopInfo loopInfo)
{
loopInfo = default;
if (!TryGetEntryBlock(scc, out var entryBlock) ||
!TryGetExitBlock(scc, out var exitBlock))
{
return(false);
}
loopInfo = new LoopInfo(scc, entryBlock, exitBlock);
return(true);
}
private static bool TryGetExitBlock(
SCCs.SCC scc,
out BasicBlock exitBlock)
{
exitBlock = null;
foreach (var node in scc)
{
foreach (var succ in node.Successors)
{
BasicBlock succBlock = succ.Block;
if (!scc.Contains(succBlock))
{
if (exitBlock != null && exitBlock != succBlock)
{
return(false);
}
exitBlock = succBlock;
}
}
}
return(exitBlock != null);
}
private static bool TryGetEntryBlock(
SCCs.SCC scc,
out BasicBlock entryPoint)
{
entryPoint = null;
foreach (var node in scc)
{
foreach (var pred in node.Predecessors)
{
if (scc.Contains(pred))
{
continue;
}
// Multiple loop entry points
if (entryPoint != null & entryPoint != pred.Block)
{
return(false);
}
entryPoint = pred.Block;
}
}
return(true);
}