void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
ArrayRef<BasicBlock *> Preds,
const char *Suffix1, const char *Suffix2,
SmallVectorImpl<BasicBlock *> &NewBBs,
DominatorTree *DT, LoopInfo *LI,
bool PreserveLCSSA) {
assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");
// Create a new basic block for OrigBB's predecessors listed in Preds. Insert
// it right before the original block.
BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
OrigBB->getName() + Suffix1,
OrigBB->getParent(), OrigBB);
NewBBs.push_back(NewBB1);
// The new block unconditionally branches to the old block.
BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);
BI1->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
// Move the edges from Preds to point to NewBB1 instead of OrigBB.
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
// This is slightly more strict than necessary; the minimum requirement
// is that there be no more than one indirectbr branching to BB. And
// all BlockAddress uses would need to be updated.
assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
}
bool HasLoopExit = false;
UpdateAnalysisInformation(OrigBB, NewBB1, Preds, DT, LI, PreserveLCSSA,
HasLoopExit);
// Update the PHI nodes in OrigBB with the values coming from NewBB1.
UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, HasLoopExit);
// Move the remaining edges from OrigBB to point to NewBB2.
SmallVector<BasicBlock*, 8> NewBB2Preds;
for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
i != e; ) {
BasicBlock *Pred = *i++;
if (Pred == NewBB1) continue;
assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
"Cannot split an edge from an IndirectBrInst");
NewBB2Preds.push_back(Pred);
e = pred_end(OrigBB);
}
BasicBlock *NewBB2 = nullptr;
if (!NewBB2Preds.empty()) {
// Create another basic block for the rest of OrigBB's predecessors.
NewBB2 = BasicBlock::Create(OrigBB->getContext(),
OrigBB->getName() + Suffix2,
OrigBB->getParent(), OrigBB);
NewBBs.push_back(NewBB2);
// The new block unconditionally branches to the old block.
BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);
BI2->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
// Move the remaining edges from OrigBB to point to NewBB2.
for (BasicBlock *NewBB2Pred : NewBB2Preds)
NewBB2Pred->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);
// Update DominatorTree, LoopInfo, and LCCSA analysis information.
HasLoopExit = false;
UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, DT, LI,
PreserveLCSSA, HasLoopExit);
// Update the PHI nodes in OrigBB with the values coming from NewBB2.
UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, HasLoopExit);
}
LandingPadInst *LPad = OrigBB->getLandingPadInst();
Instruction *Clone1 = LPad->clone();
Clone1->setName(Twine("lpad") + Suffix1);
NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);
if (NewBB2) {
Instruction *Clone2 = LPad->clone();
Clone2->setName(Twine("lpad") + Suffix2);
NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);
// Create a PHI node for the two cloned landingpad instructions only
// if the original landingpad instruction has some uses.
if (!LPad->use_empty()) {
assert(!LPad->getType()->isTokenTy() &&
"Split cannot be applied if LPad is token type. Otherwise an "
"invalid PHINode of token type would be created.");
PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
PN->addIncoming(Clone1, NewBB1);
PN->addIncoming(Clone2, NewBB2);
LPad->replaceAllUsesWith(PN);
}
LPad->eraseFromParent();
} else {
// There is no second clone. Just replace the landing pad with the first
// clone.
LPad->replaceAllUsesWith(Clone1);
LPad->eraseFromParent();
}
}
