com.google.javascript.jscomp

Class FlowSensitiveInlineVariables

java.lang.Object

com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback

com.google.javascript.jscomp.FlowSensitiveInlineVariables

All Implemented Interfaces:

CompilerPass, NodeTraversal.Callback, NodeTraversal.ScopedCallback

class FlowSensitiveInlineVariables
extends NodeTraversal.AbstractPostOrderCallback
implements CompilerPass, NodeTraversal.ScopedCallback

Inline variables when possible. Using the information from MaybeReachingVariableUse and MustBeReachingVariableDef, this pass attempts to inline a variable by placing the value at the definition where the variable is used. The basic requirements for inlining are the following:

• There is exactly one reaching definition at the use of that variable
• There is exactly one use for that definition of the variable

Other requirements can be found in FlowSensitiveInlineVariables.Candidate.canInline(com.google.javascript.jscomp.Scope). Currently this pass does not operate on the global scope due to compilation time.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	FlowSensitiveInlineVariables.Candidate Models the connection between a definition and a use of that definition.
private class	FlowSensitiveInlineVariables.GatherCandiates Gathers a list of possible candidates for inlining based only on information from MustBeReachingVariableDef.

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.List<FlowSensitiveInlineVariables.Candidate>	candidates
private ControlFlowGraph<Node>	cfg
private AbstractCompiler	compiler Implementation: This pass first perform a traversal to gather a list of Candidates that could be inlined using FlowSensitiveInlineVariables.GatherCandiates.
private java.util.Set<Var>	inlinedNewDependencies
private MustBeReachingVariableDef	reachingDef
private MaybeReachingVariableUse	reachingUses
private static com.google.common.base.Predicate<Node>	SIDE_EFFECT_PREDICATE

Constructor Summary

Constructors

Constructor and Description
FlowSensitiveInlineVariables(AbstractCompiler compiler)

Method Summary

Modifier and Type	Method and Description
private static boolean	checkLeftOf(Node n, Node expressionRoot, com.google.common.base.Predicate<Node> predicate) Given an expression by its root and sub-expression n, return true if there the predicate is true for some expression on the left of n.
private static boolean	checkRightOf(Node n, Node expressionRoot, com.google.common.base.Predicate<Node> predicate) Given an expression by its root and sub-expression n, return true if there the predicate is true for some expression on the right of n.
void	enterScope(NodeTraversal t) Called immediately after entering a new scope.
void	exitScope(NodeTraversal t) Called immediately before exiting a scope.
void	process(Node externs, Node root) Process the JS with root node root.
void	visit(NodeTraversal t, Node n, Node parent) Visits a node in postorder (after its children have been visited).

Methods inherited from class com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback

shouldTraverse

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.google.javascript.jscomp.NodeTraversal.Callback

shouldTraverse

Field Detail

compiler

private final AbstractCompiler compiler

Implementation: This pass first perform a traversal to gather a list of Candidates that could be inlined using FlowSensitiveInlineVariables.GatherCandiates. The second step involves verifying that each candidate is actually safe to inline with FlowSensitiveInlineVariables.Candidate.canInline(Scope) and finally perform inlining using FlowSensitiveInlineVariables.Candidate.inlineVariable(). The reason for the delayed evaluation of the candidates is because we need two separate dataflow result.

inlinedNewDependencies

private final java.util.Set<Var> inlinedNewDependencies

cfg

private ControlFlowGraph<Node> cfg

candidates

private java.util.List<FlowSensitiveInlineVariables.Candidate> candidates

reachingDef

private MustBeReachingVariableDef reachingDef

reachingUses

private MaybeReachingVariableUse reachingUses

SIDE_EFFECT_PREDICATE

private static final com.google.common.base.Predicate<Node> SIDE_EFFECT_PREDICATE

Constructor Detail

FlowSensitiveInlineVariables

public FlowSensitiveInlineVariables(AbstractCompiler compiler)

Method Detail

enterScope

public void enterScope(NodeTraversal t)

Description copied from interface: NodeTraversal.ScopedCallback

Called immediately after entering a new scope. The new scope can be accessed through t.getScope()

Specified by:

enterScope in interface NodeTraversal.ScopedCallback

exitScope

public void exitScope(NodeTraversal t)

Description copied from interface: NodeTraversal.ScopedCallback

Called immediately before exiting a scope. The ending scope can be accessed through t.getScope()

Specified by:

exitScope in interface NodeTraversal.ScopedCallback

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

visit

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

Description copied from interface: NodeTraversal.Callback

Visits a node in postorder (after its children have been visited). A node is visited only if all its parents should be traversed (NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node)).

Implementations can have side effects (e.g. modifying the parse tree).

Specified by:

visit in interface NodeTraversal.Callback

checkRightOf

private static boolean checkRightOf(Node n,
                                    Node expressionRoot,
                                    com.google.common.base.Predicate<Node> predicate)

Given an expression by its root and sub-expression n, return true if there the predicate is true for some expression on the right of n. Example: NotChecked(), NotChecked(), n, Checked(), Checked();

checkLeftOf

private static boolean checkLeftOf(Node n,
                                   Node expressionRoot,
                                   com.google.common.base.Predicate<Node> predicate)

Given an expression by its root and sub-expression n, return true if there the predicate is true for some expression on the left of n. Example: Checked(), Checked(), n, NotChecked(), NotChecked();