/// <summary>
/// Tries to determine a unique body start block.
/// </summary>
/// <param name="loop">The parent loop.</param>
/// <param name="body">The loop body (if any).</param>
/// <param name="isDoWhileLoop">
/// True, if the body is executed in all cases.
/// </param>
/// <returns>True, if the given loop body could be resolved.</returns>
private static bool TryGetLoopBody(
Loops <TOrder, TDirection> .Node loop,
out BasicBlock body,
out bool isDoWhileLoop)
{
body = null;
isDoWhileLoop = false;
// Get the header block and check for supported loop graphs
var header = loop.Headers[0];
var successors = header.GetSuccessors <TDirection>();
if (successors.Length != 2)
{
return(false);
}
// Determine the main body block
body = loop.Exits.Contains(successors[0]) ? successors[1] : successors[0];
// Determine whether the body block will be executed in all cases
isDoWhileLoop = true;
foreach (var entry in loop.Entries)
{
isDoWhileLoop &= entry.Successors.Contains(
body,
new BasicBlock.Comparer());
}
return(true);
}
/// <summary>
/// Tries to create a new loop info instance from the given SCC while checking
/// for unique entry and exit blocks.
/// </summary>
/// <param name="loop">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(
Loops <TOrder, TDirection> .Node loop,
out LoopInfo <TOrder, TDirection> loopInfo)
{
loopInfo = default;
// Check for simple loops with manageable induction variables
if (loop.Entries.Length > 1 || loop.Exits.Length > 1 ||
loop.Headers.Length > 1 || loop.Breakers.Length > 1 ||
loop.BackEdges.Length > 1 ||
!TryGetLoopBody(loop, out var body, out bool isDoWhileLoop) ||
!TryGetPhis(
loop,
isDoWhileLoop,
out var inductionVariables,
out var phiValues))
{
return(false);
}
loopInfo = new LoopInfo <TOrder, TDirection>(
loop,
body,
isDoWhileLoop,
ref inductionVariables,
ref phiValues);
return(true);
}
/// <summary>
/// Tries to determine a unique body start block.
/// </summary>
/// <param name="loop">The parent loop.</param>
/// <param name="body">The loop body (if any).</param>
/// <returns>True, if the given loop body could be resolved.</returns>
private static bool TryGetLoopBody(
Loops <TOrder, TDirection> .Node loop,
out BasicBlock body)
{
var header = loop.Headers[0];
var successors = header.GetSuccessors <TDirection>();
body = null;
if (successors.Length != 2)
{
return(false);
}
body = loop.Exits.Contains(successors[0]) ? successors[1] : successors[0];
return(true);
}
/// <summary>
/// Tries to get all induction variables and supported phi values of the given
/// loop object.
/// </summary>
/// <param name="loop">The parent loop.</param>
/// <param name="isDoWhileLoop">
/// True, if the body is executed in all cases.
/// </param>
/// <param name="inductionVariables">The list of induction variables.</param>
/// <param name="phiValues">The list of phi values.</param>
/// <returns>True, if the given loop has supported phi values.</returns>
private static bool TryGetPhis(
Loops <TOrder, TDirection> .Node loop,
bool isDoWhileLoop,
out InlineList <InductionVariable> inductionVariables,
/// <summary>
/// Creates a new loop info instance from the given SCC while checking for
/// unique entry and exit blocks.
/// </summary>
/// <param name="loop">The SCC.</param>
/// <returns>The resolved loop info instance.</returns>
public static LoopInfo <TOrder, TDirection> Create(
Loops <TOrder, TDirection> .Node loop) =>
TryCreate(loop, out var loopInfo)
? loopInfo
: throw new InvalidKernelOperationException();