void SimplifiedBackwardsTextIteratorAlgorithm<Strategy>::advance()
{
ASSERT(m_positionNode);
if (m_shouldStop)
return;
if (m_stopsOnFormControls && HTMLFormControlElement::enclosingFormControlElement(m_node)) {
m_shouldStop = true;
return;
}
m_positionNode = nullptr;
m_textLength = 0;
while (m_node && !m_havePassedStartNode) {
// Don't handle node if we start iterating at [node, 0].
if (!m_handledNode && !(m_node == m_endNode && !m_endOffset)) {
LayoutObject* layoutObject = m_node->layoutObject();
if (layoutObject && layoutObject->isText() && m_node->nodeType() == Node::TEXT_NODE) {
// FIXME: What about CDATA_SECTION_NODE?
if (layoutObject->style()->visibility() == VISIBLE && m_offset > 0)
m_handledNode = handleTextNode();
} else if (layoutObject && (layoutObject->isLayoutPart() || TextIterator::supportsAltText(m_node))) {
if (layoutObject->style()->visibility() == VISIBLE && m_offset > 0)
m_handledNode = handleReplacedElement();
} else {
m_handledNode = handleNonTextNode();
}
if (m_positionNode)
return;
}
if (!m_handledChildren && m_node->hasChildren()) {
m_node = m_node->lastChild();
m_fullyClippedStack.pushFullyClippedState(m_node);
} else {
// Exit empty containers as we pass over them or containers
// where [container, 0] is where we started iterating.
if (!m_handledNode
&& canHaveChildrenForEditing(m_node)
&& m_node->parentNode()
&& (!m_node->lastChild() || (m_node == m_endNode && !m_endOffset))) {
exitNode();
if (m_positionNode) {
m_handledNode = true;
m_handledChildren = true;
return;
}
}
// Exit all other containers.
while (!m_node->previousSibling()) {
if (!advanceRespectingRange(m_node->parentOrShadowHostNode()))
break;
m_fullyClippedStack.pop();
exitNode();
if (m_positionNode) {
m_handledNode = true;
m_handledChildren = true;
return;
}
}
m_fullyClippedStack.pop();
if (advanceRespectingRange(m_node->previousSibling()))
m_fullyClippedStack.pushFullyClippedState(m_node);
else
m_node = nullptr;
}
// For the purpose of word boundary detection,
// we should iterate all visible text and trailing (collapsed) whitespaces.
m_offset = m_node ? maxOffsetIncludingCollapsedSpaces(m_node) : 0;
m_handledNode = false;
m_handledChildren = false;
if (m_positionNode)
return;
}
}
/**
* @brief Computes the FuncInfo and returns it.
*/
ShPtr<OptimFuncInfo> OptimFuncInfoCFGTraversal::performComputation() {
// First, we pre-compute varsAlwaysModifiedBeforeRead. The reason is that
// their computation differs from the computation of the rest of the sets.
precomputeAlwaysModifiedVarsBeforeRead();
// Every function's body is of the following form:
//
// (1) definitions of local variables, including assignments of global
// variables into local variables
// (2) other statements
//
// We store which variables are read/modified in (1). Then, we start the
// traversal from (2). During the traversal, we check which variables are
// read/modified and update funcInfo accordingly. The stored information
// from (1) is used to compute the set of global variables which are read
// in the function, but not modified.
//
// To give a specific example, consider the following code:
//
// def func(mango):
// global orange
// global plum
// lychee = orange
// achira = plum
// orange = mango
// plum = rand()
// result = plum * apple + orange
// orange = lychee
// plum = achira
// return result
//
// Here, even though the global variable orange is modified, its value
// before calling func() is the same as after calling func(). Indeed, its
// value is restored before the return statement. Hence, we may put it into
// funcInfo->varsWithNeverChangedValue.
// TODO Implement a more robust analysis.
ShPtr<Statement> currStmt = traversedFunc->getBody();
while (isVarDefOrAssignStmt(currStmt)) {
updateFuncInfo(currStmt);
ShPtr<Expression> lhs(getLhs(currStmt));
ShPtr<Expression> rhs(getRhs(currStmt));
// If there is no right-hand side, it is a VarDefStmt with no
// initializer, which we may skip.
if (!rhs) {
currStmt = currStmt->getSuccessor();
continue;
}
// If there are any function calls or dereferences, we have reached
// (2).
ShPtr<ValueData> currStmtData(va->getValueData(currStmt));
if (currStmtData->hasCalls() || currStmtData->hasDerefs()) {
break;
}
// Check whether the statement is of the form localVar = globalVar.
ShPtr<Variable> localVar(cast<Variable>(lhs));
ShPtr<Variable> globalVar(cast<Variable>(rhs));
if (!localVar || !globalVar || hasItem(globalVars, localVar) ||
!hasItem(globalVars, globalVar)) {
// It is not of the abovementioned form, so skip it.
currStmt = currStmt->getSuccessor();
continue;
}
storedGlobalVars[globalVar] = localVar;
currStmt = currStmt->getSuccessor();
}
// Perform the traversal only if we haven't reached the end of the function
// yet. Since empty statements are not present in a CFG, skip them before
// the traversal.
if ((currStmt = skipEmptyStmts(currStmt))) {
performTraversal(currStmt);
}
// We use the exit node of the CFG to check that every variable from
// storedGlobalVars is retrieved its original value before every return.
ShPtr<CFG::Node> exitNode(cfg->getExitNode());
// For every predecessor of the exit node...
for (auto i = exitNode->pred_begin(), e = exitNode->pred_end(); i != e; ++i) {
bool checkingShouldContinue = checkExitNodesPredecessor((*i)->getSrc());
if (!checkingShouldContinue) {
break;
}
}
// Update funcInfo using the remaining variables in storedGlobalVars.
for (const auto &p : storedGlobalVars) {
funcInfo->varsWithNeverChangedValue.insert(p.first);
}
// Update funcInfo->never{Read,Modified}Vars by global variables which are
// untouched in this function.
for (auto i = module->global_var_begin(), e = module->global_var_end();
i != e; ++i) {
ShPtr<Variable> var((*i)->getVar());
if (!hasItem(funcInfo->mayBeReadVars, var) &&
!hasItem(funcInfo->mayBeModifiedVars, var)) {
funcInfo->neverReadVars.insert(var);
funcInfo->neverModifiedVars.insert(var);
}
}
// If the cfg contains only a single non-{entry,exit} node, every
// mayBe{Read,Modifed} variable can be turned into a always{Read,Modified}
// variable.
if (cfg->getNumberOfNodes() == 3) {
addToSet(funcInfo->mayBeReadVars, funcInfo->alwaysReadVars);
addToSet(funcInfo->mayBeModifiedVars, funcInfo->alwaysModifiedVars);
}
// Add all variables which are never read and never modified to
// varsWithNeverChangedValue.
VarSet neverReadAndModifedVars(setIntersection(funcInfo->neverReadVars,
funcInfo->neverModifiedVars));
addToSet(neverReadAndModifedVars, funcInfo->varsWithNeverChangedValue);
// Add all global variables are not read in this function into
// varsAlwaysModifiedBeforeRead.
addToSet(setDifference(globalVars, funcInfo->mayBeReadVars),
funcInfo->varsAlwaysModifiedBeforeRead);
return funcInfo;
}
