P4::Visitor::Tracker Class Reference

Assists visitors in traversing the IR. More...

Public Member Functions
bool	busy (const IR::Node *n) const
bool	done (const IR::Node *n) const
void	finish (const IR::Node *n)
void	revisit_visited ()
bool	shouldVisitOnce (const IR::Node *n) const
VisitStatus	try_start (const IR::Node *n, bool defaultVisitOnce)
void	visitAgain (const IR::Node *n)
void	visitOnce (const IR::Node *n)

Detailed Description

Assists visitors in traversing the IR.

A Tracker object assists visitors traversing the IR by tracking each node. The start method begins tracking, and finish ends it. The done method determines whether the node has been visited.

Member Function Documentation

busy()

bool P4::Visitor::Tracker::busy ( const IR::Node * n ) const

inlinenodiscard

Determine whether
is currently being visited and the visitor has not finished That is, start(@n) has been invoked, and finish(@n) has not,

Returns

true if
is being visited and has not finished

done()

bool P4::Visitor::Tracker::done ( const IR::Node * n ) const

inlinenodiscard

Determine whether
has been visited and the visitor has finished and we don't want to visit
again the next time we see it. That is, start(@n) has been invoked, followed by finish(@n), and the visitOnce field is true.

Returns

true if
has been visited and the visitor is finished and visitOnce is true

finish()

void P4::Visitor::Tracker::finish ( const IR::Node * n )

inline

Mark the process of visiting
as finished, with @final being the final state of the node, or nullptr if the node was removed from the tree. done(@n) will return true, and result(@n) will return the resulting node, if any.

If @final is a new node, that node is marked as finished as well, as if start(@final); finish(@final); were invoked.

Exceptions

Util::CompilerBug

This method fails if `start( )` has not previously been invoked.

revisit_visited()

void P4::Visitor::Tracker::revisit_visited ( )

inline

Forget nodes that have already been visited, allowing them to be visited again.

shouldVisitOnce()

bool P4::Visitor::Tracker::shouldVisitOnce ( const IR::Node * n ) const

inline

Return a visitOnce flag for node

try_start()

VisitStatus P4::Visitor::Tracker::try_start ( const IR::Node * n, bool defaultVisitOnce )

inlinenodiscard

Begin tracking
during a visiting pass. Use finish(@n) to mark
as visited once the pass completes.

Returns

Status of the node
wrt visit: whether node is currently being visited (VisitStatus::Busy), or if node was already visited (VisitStatus::Done), node was never seen before (VisitStatus::New) or seen, but should be revisited (VisitStatus::Revisit).