com.google.javascript.jscomp

Class ControlFlowAnalysis

java.lang.Object

com.google.javascript.jscomp.ControlFlowAnalysis

All Implemented Interfaces:

CompilerPass, NodeTraversal.Callback

public final class ControlFlowAnalysis
extends java.lang.Object
implements NodeTraversal.Callback, CompilerPass

This is a compiler pass that computes a control flow graph. Note that this is only a CompilerPass because the Compiler invokes it via Compiler#process. It is never included in a PassConfig.

Method Summary

Modifier and Type	Method and Description
static ControlFlowGraph<Node>	getCfg(AbstractCompiler compiler, Node cfgRoot)
static boolean	isBreakTarget(Node target, java.lang.String label) Checks if target is actually the break target of labeled continue.
static boolean	mayThrowException(Node n) Determines if the subtree might throw an exception.
void	process(Node externs, Node root) Process the JS with root node root.
boolean	shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent) Visits a node in preorder (before its children) and decides whether its children should be traversed.
void	visit(NodeTraversal t, Node n, Node parent) Visits a node in postorder (after its children).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getCfg

public static ControlFlowGraph<Node> getCfg(AbstractCompiler compiler,
                                            Node cfgRoot)

process

public void process(Node externs,
                    Node root)

Description copied from interface: CompilerPass

Process the JS with root node root. Can modify the contents of each Node tree

Specified by:

process in interface CompilerPass

Parameters:

externs - Top of external JS tree

root - Top of JS tree

shouldTraverse

public boolean shouldTraverse(NodeTraversal nodeTraversal,
                              Node n,
                              Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in preorder (before its children) and decides whether its children should be traversed. If the children should be traversed, they will be visited by NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node) in preorder and by NodeTraversal.Callback.visit(NodeTraversal, Node, Node) in postorder.

Siblings are always visited left-to-right.

Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.

Specified by:

shouldTraverse in interface NodeTraversal.Callback

Parameters:

nodeTraversal - The current traversal.

n - The current node.

parent - The parent of the current node.

Returns:

whether the children of this node should be visited

visit

public void visit(NodeTraversal t,
                  Node n,
                  Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in postorder (after its children). A node is visited in postorder iff NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node) returned true for its parent. In particular, the root node is never visited in postorder.

Siblings are always visited left-to-right.

Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.

Specified by:

visit in interface NodeTraversal.Callback

Parameters:

t - The current traversal.

n - The current node.

parent - The parent of the current node.

isBreakTarget

public static boolean isBreakTarget(Node target,
                                    java.lang.String label)

Checks if target is actually the break target of labeled continue. The label can be null if it is an unlabeled break.

mayThrowException

public static boolean mayThrowException(Node n)

Determines if the subtree might throw an exception.