/**
* @param name The Name whose properties references should be updated.
* @param value The value to use when rewriting.
* @param depth The chain depth.
* @param newNodes Expression nodes that have been updated.
*/
private static void rewriteAliasProps(Name name, Node value, int depth, Set<AstChange> newNodes) {
if (name.props == null) {
return;
}
Preconditions.checkState(!value.matchesQualifiedName(name.getFullName()));
for (Name prop : name.props) {
rewriteAliasProps(prop, value, depth + 1, newNodes);
List<Ref> refs = new ArrayList<>(prop.getRefs());
for (Ref ref : refs) {
Node target = ref.node;
for (int i = 0; i <= depth; i++) {
if (target.isGetProp()) {
target = target.getFirstChild();
} else if (NodeUtil.isObjectLitKey(target)) {
// Object literal key definitions are a little trickier, as we
// need to find the assignment target
Node gparent = target.getParent().getParent();
if (gparent.isAssign()) {
target = gparent.getFirstChild();
} else {
Preconditions.checkState(NodeUtil.isObjectLitKey(gparent));
target = gparent;
}
} else {
throw new IllegalStateException("unexpected: " + target);
}
}
Preconditions.checkState(target.isGetProp() || target.isName());
target.getParent().replaceChild(target, value.cloneTree());
prop.removeRef(ref);
// Rescan the expression root.
newNodes.add(new AstChange(ref.module, ref.scope, ref.node));
}
}
}
/**
* For each qualified name N in the global scope, we check if: (a) No ancestor of N is ever
* aliased or assigned an unknown value type. (If N = "a.b.c", "a" and "a.b" are never aliased).
* (b) N has exactly one write, and it lives in the global scope. (c) N is aliased in a local
* scope. (d) N is aliased in global scope
*
* <p>If (a) is true, then GlobalNamespace must know all the writes to N. If (a) and (b) are true,
* then N cannot change during the execution of a local scope. If (a) and (b) and (c) are true,
* then the alias can be inlined if the alias obeys the usual rules for how we decide whether a
* variable is inlineable. If (a) and (b) and (d) are true, then inline the alias if possible (if
* it is assigned exactly once unconditionally).
*
* @see InlineVariables
*/
private void inlineAliases(GlobalNamespace namespace) {
// Invariant: All the names in the worklist meet condition (a).
Deque<Name> workList = new ArrayDeque<>(namespace.getNameForest());
while (!workList.isEmpty()) {
Name name = workList.pop();
// Don't attempt to inline a getter or setter property as a variable.
if (name.type == Name.Type.GET || name.type == Name.Type.SET) {
continue;
}
if (!name.inExterns && name.globalSets == 1 && name.localSets == 0 && name.aliasingGets > 0) {
// {@code name} meets condition (b). Find all of its local aliases
// and try to inline them.
List<Ref> refs = new ArrayList<>(name.getRefs());
for (Ref ref : refs) {
if (ref.type == Type.ALIASING_GET && ref.scope.isLocal()) {
// {@code name} meets condition (c). Try to inline it.
// TODO(johnlenz): consider picking up new aliases at the end
// of the pass instead of immediately like we do for global
// inlines.
if (inlineAliasIfPossible(name, ref, namespace)) {
name.removeRef(ref);
}
} else if (ref.type == Type.ALIASING_GET
&& ref.scope.isGlobal()
&& ref.getTwin() == null) { // ignore aliases in chained assignments
if (inlineGlobalAliasIfPossible(name, ref, namespace)) {
name.removeRef(ref);
}
}
}
}
// Check if {@code name} has any aliases left after the
// local-alias-inlining above.
if ((name.type == Name.Type.OBJECTLIT || name.type == Name.Type.FUNCTION)
&& name.aliasingGets == 0
&& name.props != null) {
// All of {@code name}'s children meet condition (a), so they can be
// added to the worklist.
workList.addAll(name.props);
}
}
}
/**
* Attempt to inline an global alias of a global name. This requires that the name is well
* defined: assigned unconditionally, assigned exactly once. It is assumed that, the name for
* which it is an alias must already meet these same requirements.
*
* @param alias The alias to inline
* @return Whether the alias was inlined.
*/
private boolean inlineGlobalAliasIfPossible(Name name, Ref alias, GlobalNamespace namespace) {
// Ensure that the alias is assigned to global name at that the
// declaration.
Node aliasParent = alias.node.getParent();
if (aliasParent.isAssign() && NodeUtil.isExecutedExactlyOnce(aliasParent)
// We special-case for constructors here, to inline constructor aliases
// more aggressively in global scope.
// We do this because constructor properties are always collapsed,
// so we want to inline the aliases also to avoid breakages.
|| aliasParent.isName() && name.isConstructor()) {
Node lvalue = aliasParent.isName() ? aliasParent : aliasParent.getFirstChild();
if (!lvalue.isQualifiedName()) {
return false;
}
name = namespace.getSlot(lvalue.getQualifiedName());
if (name != null && name.isInlinableGlobalAlias()) {
Set<AstChange> newNodes = new LinkedHashSet<>();
List<Ref> refs = new ArrayList<>(name.getRefs());
for (Ref ref : refs) {
switch (ref.type) {
case SET_FROM_GLOBAL:
continue;
case DIRECT_GET:
case ALIASING_GET:
Node newNode = alias.node.cloneTree();
Node node = ref.node;
node.getParent().replaceChild(node, newNode);
newNodes.add(new AstChange(ref.module, ref.scope, newNode));
name.removeRef(ref);
break;
default:
throw new IllegalStateException();
}
}
rewriteAliasProps(name, alias.node, 0, newNodes);
// just set the original alias to null.
aliasParent.replaceChild(alias.node, IR.nullNode());
compiler.reportCodeChange();
// Inlining the variable may have introduced new references
// to descendants of {@code name}. So those need to be collected now.
namespace.scanNewNodes(newNodes);
return true;
}
}
return false;
}
