/// Checks whether there are checks in the preheader's predecessor that ensure
/// that "Start < End".
static bool isRangeChecked(SILValue Start, SILValue End,
SILBasicBlock *Preheader, DominanceInfo *DT) {
// Check two constants.
if (isLessThan(Start, End))
return true;
// Look for a branch on EQ around the Preheader.
auto *PreheaderPred = Preheader->getSinglePredecessor();
if (!PreheaderPred)
return false;
auto *CondBr = dyn_cast<CondBranchInst>(PreheaderPred->getTerminator());
if (!CondBr)
return false;
if (isLessThanCheck(Start, End, CondBr, Preheader))
return true;
// Walk up the dominator tree looking for a range check ("SLE Start, End").
DominanceInfoNode *CurDTNode = DT->getNode(PreheaderPred);
while (CurDTNode) {
if (isSignedLessEqual(Start, End, *CurDTNode->getBlock()))
return true;
CurDTNode = CurDTNode->getIDom();
}
return false;
}
/// Update the SSA form after all changes.
void CheckedCastBrJumpThreading::updateDominatorTree() {
// Update the dominator tree.
// If BB was IDom of something, then PredCBBI becomes the IDOM
// of this after jump-threading.
auto *BBDomNode = DT->getNode(BB);
auto &Children = BBDomNode->getChildren();
if (Children.size() > 1) {
SmallVector<DominanceInfoNode *, 16> ChildrenCopy;
std::copy(Children.begin(), Children.end(),
std::back_inserter(ChildrenCopy));
for (auto *Child : ChildrenCopy) {
DT->changeImmediateDominator(Child, Node);
}
}
DominanceInfoNode *CommonDom;
// Find a common dominator for all unknown preds.
if (!UnknownPreds.empty()) {
// Find a new IDom for FailureBB
CommonDom = findCommonDominator(FailureBB, DT);
if (CommonDom)
DT->changeImmediateDominator(FailureBB, CommonDom->getBlock());
CommonDom = findCommonDominator(UnknownPreds, DT);
// This common dominator dominates the BB now.
if (CommonDom) {
DT->changeImmediateDominator(BB, CommonDom->getBlock());
}
}
// Find a common dominator for all failure preds.
CommonDom = findCommonDominator(FailurePreds, DT);
// This common dominator dominates the TargetFailureBB now.
if (CommonDom) {
DT->addNewBlock(TargetFailureBB, CommonDom->getBlock());
// Find a new IDom for FailureBB
CommonDom = findCommonDominator(FailureBB, DT);
if (CommonDom)
DT->changeImmediateDominator(FailureBB, CommonDom->getBlock());
}
// Find a common dominator for all success preds.
CommonDom = findCommonDominator(SuccessPreds, DT);
// This common dominator of all success preds dominates the BB now.
if (CommonDom) {
if (TargetSuccessBB) {
DT->addNewBlock(TargetSuccessBB, CommonDom->getBlock());
} else {
DT->changeImmediateDominator(BB, CommonDom->getBlock());
}
CommonDom = findCommonDominator(SuccessBB, DT);
if (CommonDom)
DT->changeImmediateDominator(SuccessBB, CommonDom->getBlock());
}
// End of dominator tree update.
}
/// Find a nearest common dominator for a given set of basic blocks.
static DominanceInfoNode *findCommonDominator(ArrayRef<SILBasicBlock *> BBs,
DominanceInfo *DT) {
DominanceInfoNode *CommonDom = nullptr;
for (auto *BB : BBs) {
if (!CommonDom) {
CommonDom = DT->getNode(BB);
} else {
CommonDom = DT->getNode(
DT->findNearestCommonDominator(CommonDom->getBlock(), BB));
}
}
return CommonDom;
}
