+
+ // Update DominatorTree, LoopInfo, and LCCSA analysis information.
+ bool HasLoopExit = false;
+ UpdateAnalysisInformation(BB, NewBB, Preds, DT, LI, PreserveLCSSA,
+ HasLoopExit);
+
+ // Update the PHI nodes in BB with the values coming from NewBB.
+ UpdatePHINodes(BB, NewBB, Preds, BI, HasLoopExit);
+ return NewBB;
+}
+
+/// SplitLandingPadPredecessors - This method transforms the landing pad,
+/// OrigBB, by introducing two new basic blocks into the function. One of those
+/// new basic blocks gets the predecessors listed in Preds. The other basic
+/// block gets the remaining predecessors of OrigBB. The landingpad instruction
+/// OrigBB is clone into both of the new basic blocks. The new blocks are given
+/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
+///
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
+/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
+/// it does not preserve LoopSimplify (because it's complicated to handle the
+/// case where one of the edges being split is an exit of a loop with other
+/// exits).
+///
+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 (SmallVectorImpl<BasicBlock*>::iterator
+ i = NewBB2Preds.begin(), e = NewBB2Preds.end(); i != e; ++i)
+ (*i)->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();
+ }
+}
+
+/// FoldReturnIntoUncondBranch - This method duplicates the specified return
+/// instruction into a predecessor which ends in an unconditional branch. If
+/// the return instruction returns a value defined by a PHI, propagate the
+/// right value into the return. It returns the new return instruction in the
+/// predecessor.
+ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
+ BasicBlock *Pred) {
+ Instruction *UncondBranch = Pred->getTerminator();
+ // Clone the return and add it to the end of the predecessor.
+ Instruction *NewRet = RI->clone();
+ Pred->getInstList().push_back(NewRet);
+
+ // If the return instruction returns a value, and if the value was a
+ // PHI node in "BB", propagate the right value into the return.
+ for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
+ i != e; ++i) {
+ Value *V = *i;
+ Instruction *NewBC = nullptr;
+ if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
+ // Return value might be bitcasted. Clone and insert it before the
+ // return instruction.
+ V = BCI->getOperand(0);
+ NewBC = BCI->clone();
+ Pred->getInstList().insert(NewRet->getIterator(), NewBC);
+ *i = NewBC;