1 //===- LoopIndexSplit.cpp - Loop Index Splitting Pass ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Devang Patel and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Loop Index Splitting Pass.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "loop-index-split"
16 #include "llvm/Transforms/Scalar.h"
17 #include "llvm/Analysis/LoopPass.h"
18 #include "llvm/Analysis/ScalarEvolutionExpander.h"
19 #include "llvm/Analysis/Dominators.h"
20 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
21 #include "llvm/Transforms/Utils/Cloning.h"
22 #include "llvm/Support/Compiler.h"
23 #include "llvm/ADT/DepthFirstIterator.h"
24 #include "llvm/ADT/Statistic.h"
28 STATISTIC(NumIndexSplit, "Number of loops index split");
32 class VISIBILITY_HIDDEN LoopIndexSplit : public LoopPass {
35 static char ID; // Pass ID, replacement for typeid
36 LoopIndexSplit() : LoopPass((intptr_t)&ID) {}
38 // Index split Loop L. Return true if loop is split.
39 bool runOnLoop(Loop *L, LPPassManager &LPM);
41 void getAnalysisUsage(AnalysisUsage &AU) const {
42 AU.addRequired<ScalarEvolution>();
43 AU.addPreserved<ScalarEvolution>();
44 AU.addRequiredID(LCSSAID);
45 AU.addPreservedID(LCSSAID);
46 AU.addRequired<LoopInfo>();
47 AU.addPreserved<LoopInfo>();
48 AU.addRequiredID(LoopSimplifyID);
49 AU.addPreservedID(LoopSimplifyID);
50 AU.addRequired<DominatorTree>();
51 AU.addRequired<DominanceFrontier>();
52 AU.addPreserved<DominatorTree>();
53 AU.addPreserved<DominanceFrontier>();
60 SplitInfo() : SplitValue(NULL), SplitCondition(NULL) {}
62 // Induction variable's range is split at this value.
65 // This compare instruction compares IndVar against SplitValue.
66 ICmpInst *SplitCondition;
71 SplitCondition = NULL;
77 /// Find condition inside a loop that is suitable candidate for index split.
78 void findSplitCondition();
80 /// Find loop's exit condition.
81 void findLoopConditionals();
83 /// Return induction variable associated with value V.
84 void findIndVar(Value *V, Loop *L);
86 /// processOneIterationLoop - Current loop L contains compare instruction
87 /// that compares induction variable, IndVar, agains loop invariant. If
88 /// entire (i.e. meaningful) loop body is dominated by this compare
89 /// instruction then loop body is executed only for one iteration. In
90 /// such case eliminate loop structure surrounding this loop body. For
91 bool processOneIterationLoop(SplitInfo &SD);
93 /// If loop header includes loop variant instruction operands then
94 /// this loop may not be eliminated.
95 bool safeHeader(SplitInfo &SD, BasicBlock *BB);
97 /// If Exit block includes loop variant instructions then this
98 /// loop may not be eliminated.
99 bool safeExitBlock(SplitInfo &SD, BasicBlock *BB);
101 /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
102 /// This routine is used to remove split condition's dead branch, dominated by
103 /// DeadBB. LiveBB dominates split conidition's other branch.
104 void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
106 /// Find cost of spliting loop L.
107 unsigned findSplitCost(Loop *L, SplitInfo &SD);
108 bool splitLoop(SplitInfo &SD);
112 IndVarIncrement = NULL;
113 ExitCondition = NULL;
127 DominanceFrontier *DF;
128 SmallVector<SplitInfo, 4> SplitData;
130 // Induction variable whose range is being split by this transformation.
132 Instruction *IndVarIncrement;
134 // Loop exit condition.
135 ICmpInst *ExitCondition;
137 // Induction variable's initial value.
140 // Induction variable's final loop exit value operand number in exit condition..
141 unsigned ExitValueNum;
144 char LoopIndexSplit::ID = 0;
145 RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops");
148 LoopPass *llvm::createLoopIndexSplitPass() {
149 return new LoopIndexSplit();
152 // Index split Loop L. Return true if loop is split.
153 bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
154 bool Changed = false;
158 // FIXME - Nested loops make dominator info updates tricky.
159 if (!L->getSubLoops().empty())
162 SE = &getAnalysis<ScalarEvolution>();
163 DT = &getAnalysis<DominatorTree>();
164 LI = &getAnalysis<LoopInfo>();
165 DF = &getAnalysis<DominanceFrontier>();
169 findLoopConditionals();
174 findSplitCondition();
176 if (SplitData.empty())
179 // First see if it is possible to eliminate loop itself or not.
180 for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
181 E = SplitData.end(); SI != E;) {
183 if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) {
184 Changed = processOneIterationLoop(SD);
187 // If is loop is eliminated then nothing else to do here.
190 SmallVector<SplitInfo, 4>::iterator Delete_SI = SI;
192 SplitData.erase(Delete_SI);
198 unsigned MaxCost = 99;
200 unsigned MostProfitableSDIndex = 0;
201 for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
202 E = SplitData.end(); SI != E; ++SI, ++Index) {
205 // ICM_EQs are already handled above.
206 assert (SD.SplitCondition->getPredicate() != ICmpInst::ICMP_EQ &&
207 "Unexpected split condition predicate");
209 unsigned Cost = findSplitCost(L, SD);
211 MostProfitableSDIndex = Index;
214 // Split most profitiable condition.
215 if (!SplitData.empty())
216 Changed = splitLoop(SplitData[MostProfitableSDIndex]);
224 /// Return true if V is a induction variable or induction variable's
225 /// increment for loop L.
226 void LoopIndexSplit::findIndVar(Value *V, Loop *L) {
228 Instruction *I = dyn_cast<Instruction>(V);
232 // Check if I is a phi node from loop header or not.
233 if (PHINode *PN = dyn_cast<PHINode>(V)) {
234 if (PN->getParent() == L->getHeader()) {
240 // Check if I is a add instruction whose one operand is
241 // phi node from loop header and second operand is constant.
242 if (I->getOpcode() != Instruction::Add)
245 Value *Op0 = I->getOperand(0);
246 Value *Op1 = I->getOperand(1);
248 if (PHINode *PN = dyn_cast<PHINode>(Op0)) {
249 if (PN->getParent() == L->getHeader()
250 && isa<ConstantInt>(Op1)) {
257 if (PHINode *PN = dyn_cast<PHINode>(Op1)) {
258 if (PN->getParent() == L->getHeader()
259 && isa<ConstantInt>(Op0)) {
269 // Find loop's exit condition and associated induction variable.
270 void LoopIndexSplit::findLoopConditionals() {
272 BasicBlock *ExitBlock = NULL;
274 for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
277 if (!L->isLoopExit(BB))
287 // If exit block's terminator is conditional branch inst then we have found
289 BranchInst *BR = dyn_cast<BranchInst>(ExitBlock->getTerminator());
290 if (!BR || BR->isUnconditional())
293 ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
299 // Exit condition's one operand is loop invariant exit value and second
300 // operand is SCEVAddRecExpr based on induction variable.
301 Value *V0 = CI->getOperand(0);
302 Value *V1 = CI->getOperand(1);
304 SCEVHandle SH0 = SE->getSCEV(V0);
305 SCEVHandle SH1 = SE->getSCEV(V1);
307 if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
311 else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
317 ExitCondition = NULL;
319 BasicBlock *Preheader = L->getLoopPreheader();
320 StartValue = IndVar->getIncomingValueForBlock(Preheader);
324 /// Find condition inside a loop that is suitable candidate for index split.
325 void LoopIndexSplit::findSplitCondition() {
328 // Check all basic block's terminators.
330 for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
334 // If this basic block does not terminate in a conditional branch
335 // then terminator is not a suitable split condition.
336 BranchInst *BR = dyn_cast<BranchInst>(BB->getTerminator());
340 if (BR->isUnconditional())
343 ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
344 if (!CI || CI == ExitCondition)
347 // If one operand is loop invariant and second operand is SCEVAddRecExpr
348 // based on induction variable then CI is a candidate split condition.
349 Value *V0 = CI->getOperand(0);
350 Value *V1 = CI->getOperand(1);
352 SCEVHandle SH0 = SE->getSCEV(V0);
353 SCEVHandle SH1 = SE->getSCEV(V1);
355 if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
357 SD.SplitCondition = CI;
358 if (PHINode *PN = dyn_cast<PHINode>(V1)) {
360 SplitData.push_back(SD);
362 else if (Instruction *Insn = dyn_cast<Instruction>(V1)) {
363 if (IndVarIncrement && IndVarIncrement == Insn)
364 SplitData.push_back(SD);
367 else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
369 SD.SplitCondition = CI;
370 if (PHINode *PN = dyn_cast<PHINode>(V0)) {
372 SplitData.push_back(SD);
374 else if (Instruction *Insn = dyn_cast<Instruction>(V0)) {
375 if (IndVarIncrement && IndVarIncrement == Insn)
376 SplitData.push_back(SD);
382 /// processOneIterationLoop - Current loop L contains compare instruction
383 /// that compares induction variable, IndVar, against loop invariant. If
384 /// entire (i.e. meaningful) loop body is dominated by this compare
385 /// instruction then loop body is executed only once. In such case eliminate
386 /// loop structure surrounding this loop body. For example,
387 /// for (int i = start; i < end; ++i) {
388 /// if ( i == somevalue) {
392 /// can be transformed into
393 /// if (somevalue >= start && somevalue < end) {
397 bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
399 BasicBlock *Header = L->getHeader();
401 // First of all, check if SplitCondition dominates entire loop body
404 // If SplitCondition is not in loop header then this loop is not suitable
405 // for this transformation.
406 if (SD.SplitCondition->getParent() != Header)
409 // If loop header includes loop variant instruction operands then
410 // this loop may not be eliminated.
411 if (!safeHeader(SD, Header))
414 // If Exit block includes loop variant instructions then this
415 // loop may not be eliminated.
416 if (!safeExitBlock(SD, ExitCondition->getParent()))
421 // As a first step to break this loop, remove Latch to Header edge.
422 BasicBlock *Latch = L->getLoopLatch();
423 BasicBlock *LatchSucc = NULL;
424 BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator());
427 Header->removePredecessor(Latch);
428 for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
433 BR->setUnconditionalDest(LatchSucc);
435 Instruction *Terminator = Header->getTerminator();
436 Value *ExitValue = ExitCondition->getOperand(ExitValueNum);
438 // Replace split condition in header.
440 // SplitCondition : icmp eq i32 IndVar, SplitValue
442 // c1 = icmp uge i32 SplitValue, StartValue
443 // c2 = icmp ult i32 vSplitValue, ExitValue
445 bool SignedPredicate = ExitCondition->isSignedPredicate();
446 Instruction *C1 = new ICmpInst(SignedPredicate ?
447 ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
448 SD.SplitValue, StartValue, "lisplit",
450 Instruction *C2 = new ICmpInst(SignedPredicate ?
451 ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
452 SD.SplitValue, ExitValue, "lisplit",
454 Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit",
456 SD.SplitCondition->replaceAllUsesWith(NSplitCond);
457 SD.SplitCondition->eraseFromParent();
459 // Now, clear latch block. Remove instructions that are responsible
460 // to increment induction variable.
461 Instruction *LTerminator = Latch->getTerminator();
462 for (BasicBlock::iterator LB = Latch->begin(), LE = Latch->end();
466 if (isa<PHINode>(I) || I == LTerminator)
469 if (I == IndVarIncrement)
470 I->replaceAllUsesWith(ExitValue);
472 I->replaceAllUsesWith(UndefValue::get(I->getType()));
473 I->eraseFromParent();
476 LPM->deleteLoopFromQueue(L);
478 // Update Dominator Info.
479 // Only CFG change done is to remove Latch to Header edge. This
480 // does not change dominator tree because Latch did not dominate
483 DominanceFrontier::iterator HeaderDF = DF->find(Header);
484 if (HeaderDF != DF->end())
485 DF->removeFromFrontier(HeaderDF, Header);
487 DominanceFrontier::iterator LatchDF = DF->find(Latch);
488 if (LatchDF != DF->end())
489 DF->removeFromFrontier(LatchDF, Header);
494 // If loop header includes loop variant instruction operands then
495 // this loop can not be eliminated. This is used by processOneIterationLoop().
496 bool LoopIndexSplit::safeHeader(SplitInfo &SD, BasicBlock *Header) {
498 Instruction *Terminator = Header->getTerminator();
499 for(BasicBlock::iterator BI = Header->begin(), BE = Header->end();
507 // SplitCondition itself is OK.
508 if (I == SD.SplitCondition)
511 // Induction variable is OK.
515 // Induction variable increment is OK.
516 if (I == IndVarIncrement)
519 // Terminator is also harmless.
523 // Otherwise we have a instruction that may not be safe.
530 // If Exit block includes loop variant instructions then this
531 // loop may not be eliminated. This is used by processOneIterationLoop().
532 bool LoopIndexSplit::safeExitBlock(SplitInfo &SD, BasicBlock *ExitBlock) {
534 for (BasicBlock::iterator BI = ExitBlock->begin(), BE = ExitBlock->end();
542 // Induction variable increment is OK.
543 if (IndVarIncrement && IndVarIncrement == I)
546 // Check if I is induction variable increment instruction.
547 if (!IndVarIncrement && I->getOpcode() == Instruction::Add) {
549 Value *Op0 = I->getOperand(0);
550 Value *Op1 = I->getOperand(1);
552 ConstantInt *CI = NULL;
554 if ((PN = dyn_cast<PHINode>(Op0))) {
555 if ((CI = dyn_cast<ConstantInt>(Op1)))
558 if ((PN = dyn_cast<PHINode>(Op1))) {
559 if ((CI = dyn_cast<ConstantInt>(Op0)))
563 if (IndVarIncrement && PN == IndVar && CI->isOne())
567 // I is an Exit condition if next instruction is block terminator.
568 // Exit condition is OK if it compares loop invariant exit value,
569 // which is checked below.
570 else if (ICmpInst *EC = dyn_cast<ICmpInst>(I)) {
571 if (EC == ExitCondition)
575 if (I == ExitBlock->getTerminator())
578 // Otherwise we have instruction that may not be safe.
582 // We could not find any reason to consider ExitBlock unsafe.
586 /// Find cost of spliting loop L. Cost is measured in terms of size growth.
587 /// Size is growth is calculated based on amount of code duplicated in second
589 unsigned LoopIndexSplit::findSplitCost(Loop *L, SplitInfo &SD) {
592 BasicBlock *SDBlock = SD.SplitCondition->getParent();
593 for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
596 // If a block is not dominated by split condition block then
597 // it must be duplicated in both loops.
598 if (!DT->dominates(SDBlock, BB))
605 /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
606 /// This routine is used to remove split condition's dead branch, dominated by
607 /// DeadBB. LiveBB dominates split conidition's other branch.
608 void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
609 BasicBlock *LiveBB) {
611 // First update DeadBB's dominance frontier.
612 SmallVector<BasicBlock *, 8> FrontierBBs;
613 DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB);
614 if (DeadBBDF != DF->end()) {
615 SmallVector<BasicBlock *, 8> PredBlocks;
617 DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second;
618 for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
619 DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) {
620 BasicBlock *FrontierBB = *DeadBBSetI;
621 FrontierBBs.push_back(FrontierBB);
623 // Rremove any PHI incoming edge from blocks dominated by DeadBB.
625 for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB);
628 if (P == DeadBB || DT->dominates(DeadBB, P))
629 PredBlocks.push_back(P);
632 BasicBlock *NewDominator = NULL;
633 for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end();
635 if (PHINode *PN = dyn_cast<PHINode>(FBI)) {
636 for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(),
637 PE = PredBlocks.end(); PI != PE; ++PI) {
639 PN->removeIncomingValue(P);
641 // If we have not identified new dominator then see if we can identify
642 // one based on remaining incoming PHINode values.
643 if (NewDominator == NULL && PN->getNumIncomingValues() == 1)
644 NewDominator = PN->getIncomingBlock(0);
652 // Now remove DeadBB and all nodes dominated by DeadBB in df order.
653 SmallVector<BasicBlock *, 32> WorkList;
654 DomTreeNode *DN = DT->getNode(DeadBB);
655 for (df_iterator<DomTreeNode*> DI = df_begin(DN),
656 E = df_end(DN); DI != E; ++DI) {
657 BasicBlock *BB = DI->getBlock();
658 WorkList.push_back(BB);
659 BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy));
662 while (!WorkList.empty()) {
663 BasicBlock *BB = WorkList.back(); WorkList.pop_back();
664 for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
666 Instruction *I = BBI;
667 I->replaceAllUsesWith(UndefValue::get(I->getType()));
668 I->eraseFromParent();
670 LPM->deleteSimpleAnalysisValue(BB, LP);
674 BB->eraseFromParent();
677 // Update Frontier BBs' dominator info.
678 while (!FrontierBBs.empty()) {
679 BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back();
680 BasicBlock *NewDominator = FBB->getSinglePredecessor();
682 pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
685 if (NewDominator != LiveBB) {
686 for(; PI != PE; ++PI) {
689 NewDominator = LiveBB;
692 NewDominator = DT->findNearestCommonDominator(NewDominator, P);
696 assert (NewDominator && "Unable to fix dominator info.");
697 DT->changeImmediateDominator(FBB, NewDominator);
698 DF->changeImmediateDominator(FBB, NewDominator, DT);
703 bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
705 BasicBlock *Preheader = L->getLoopPreheader();
706 BasicBlock *SplitBlock = SD.SplitCondition->getParent();
707 BasicBlock *Latch = L->getLoopLatch();
708 BasicBlock *Header = L->getHeader();
709 BranchInst *SplitTerminator = cast<BranchInst>(SplitBlock->getTerminator());
711 // FIXME - Unable to handle triange loops at the moment.
712 // In triangle loop, split condition is in header and one of the
713 // the split destination is loop latch. If split condition is EQ
714 // then such loops are already handle in processOneIterationLoop().
715 if (Header == SplitBlock
716 && (Latch == SplitTerminator->getSuccessor(0)
717 || Latch == SplitTerminator->getSuccessor(1)))
720 // If one of the split condition branch is post dominating other then loop
721 // index split is not appropriate.
722 BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
723 BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
724 if (DT->dominates(Succ0, Latch) || DT->dominates(Succ1, Latch))
727 // If one of the split condition branch is a predecessor of the other
728 // split condition branch head then do not split loop on this condition.
729 for(pred_iterator PI = pred_begin(Succ0), PE = pred_end(Succ0); PI != PE; ++PI)
732 for(pred_iterator PI = pred_begin(Succ1), PE = pred_end(Succ1); PI != PE; ++PI)
736 // True loop is original loop. False loop is cloned loop.
738 bool SignedPredicate = ExitCondition->isSignedPredicate();
739 //[*] Calculate True loop's new Exit Value in loop preheader.
740 // TLExitValue = min(SplitValue, ExitValue)
741 //[*] Calculate False loop's new Start Value in loop preheader.
742 // FLStartValue = min(SplitValue, TrueLoop.StartValue)
743 Value *TLExitValue = NULL;
744 Value *FLStartValue = NULL;
745 if (isa<ConstantInt>(SD.SplitValue)) {
746 TLExitValue = SD.SplitValue;
747 FLStartValue = SD.SplitValue;
750 Value *C1 = new ICmpInst(SignedPredicate ?
751 ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
753 ExitCondition->getOperand(ExitValueNum),
755 Preheader->getTerminator());
756 TLExitValue = new SelectInst(C1, SD.SplitValue,
757 ExitCondition->getOperand(ExitValueNum),
758 "lsplit.ev", Preheader->getTerminator());
760 Value *C2 = new ICmpInst(SignedPredicate ?
761 ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
762 SD.SplitValue, StartValue, "lsplit.sv",
763 Preheader->getTerminator());
764 FLStartValue = new SelectInst(C2, SD.SplitValue, StartValue,
765 "lsplit.sv", Preheader->getTerminator());
768 //[*] Clone loop. Avoid true destination of split condition and
769 // the blocks dominated by true destination.
770 DenseMap<const Value *, Value *> ValueMap;
771 Loop *FalseLoop = CloneLoop(L, LPM, LI, ValueMap, this);
772 BasicBlock *FalseHeader = FalseLoop->getHeader();
774 //[*] True loop's exit edge enters False loop.
775 PHINode *IndVarClone = cast<PHINode>(ValueMap[IndVar]);
776 BasicBlock *ExitBlock = ExitCondition->getParent();
777 BranchInst *ExitInsn = dyn_cast<BranchInst>(ExitBlock->getTerminator());
778 assert (ExitInsn && "Unable to find suitable loop exit branch");
779 BasicBlock *ExitDest = ExitInsn->getSuccessor(1);
781 if (L->contains(ExitDest)) {
782 ExitDest = ExitInsn->getSuccessor(0);
783 ExitInsn->setSuccessor(0, FalseHeader);
785 ExitInsn->setSuccessor(1, FalseHeader);
787 // Collect inverse map of Header PHINodes.
788 DenseMap<Value *, Value *> InverseMap;
789 for (BasicBlock::iterator BI = L->getHeader()->begin(),
790 BE = L->getHeader()->end(); BI != BE; ++BI) {
791 if (PHINode *PN = dyn_cast<PHINode>(BI)) {
792 PHINode *PNClone = cast<PHINode>(ValueMap[PN]);
793 InverseMap[PNClone] = PN;
798 // Update False loop's header
799 for (BasicBlock::iterator BI = FalseHeader->begin(), BE = FalseHeader->end();
801 if (PHINode *PN = dyn_cast<PHINode>(BI)) {
802 PN->removeIncomingValue(Preheader);
803 if (PN == IndVarClone)
804 PN->addIncoming(FLStartValue, ExitBlock);
806 PHINode *OrigPN = cast<PHINode>(InverseMap[PN]);
807 Value *V2 = OrigPN->getIncomingValueForBlock(ExitBlock);
808 PN->addIncoming(V2, ExitBlock);
814 // Update ExitDest. Now it's predecessor is False loop's exit block.
815 BasicBlock *ExitBlockClone = cast<BasicBlock>(ValueMap[ExitBlock]);
816 for (BasicBlock::iterator BI = ExitDest->begin(), BE = ExitDest->end();
818 if (PHINode *PN = dyn_cast<PHINode>(BI)) {
819 PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(ExitBlock)], ExitBlockClone);
820 PN->removeIncomingValue(ExitBlock);
826 DT->changeImmediateDominator(FalseHeader, ExitBlock);
827 DT->changeImmediateDominator(ExitDest, cast<BasicBlock>(ValueMap[ExitBlock]));
830 assert (!L->contains(ExitDest) && " Unable to find exit edge destination");
832 //[*] Split Exit Edge.
833 SplitEdge(ExitBlock, FalseHeader, this);
835 //[*] Eliminate split condition's false branch from True loop.
836 BranchInst *BR = cast<BranchInst>(SplitBlock->getTerminator());
837 BasicBlock *FBB = BR->getSuccessor(1);
838 BR->setUnconditionalDest(BR->getSuccessor(0));
839 removeBlocks(FBB, L, BR->getSuccessor(0));
841 //[*] Update True loop's exit value using new exit value.
842 ExitCondition->setOperand(ExitValueNum, TLExitValue);
844 //[*] Eliminate split condition's true branch in False loop CFG.
845 BasicBlock *FSplitBlock = cast<BasicBlock>(ValueMap[SplitBlock]);
846 BranchInst *FBR = cast<BranchInst>(FSplitBlock->getTerminator());
847 BasicBlock *TBB = FBR->getSuccessor(0);
848 FBR->setUnconditionalDest(FBR->getSuccessor(1));
849 removeBlocks(TBB, FalseLoop, cast<BasicBlock>(FBR->getSuccessor(0)));