| //===- LoopIndexSplit.cpp - Loop Index Splitting Pass ---------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements Loop Index Splitting Pass. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "loop-index-split" |
| |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Analysis/LoopPass.h" |
| #include "llvm/Analysis/ScalarEvolutionExpander.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Cloning.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/Statistic.h" |
| |
| using namespace llvm; |
| |
| STATISTIC(NumIndexSplit, "Number of loops index split"); |
| |
| namespace { |
| |
| class VISIBILITY_HIDDEN LoopIndexSplit : public LoopPass { |
| |
| public: |
| static char ID; // Pass ID, replacement for typeid |
| LoopIndexSplit() : LoopPass((intptr_t)&ID) {} |
| |
| // Index split Loop L. Return true if loop is split. |
| bool runOnLoop(Loop *L, LPPassManager &LPM); |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<ScalarEvolution>(); |
| AU.addPreserved<ScalarEvolution>(); |
| AU.addRequiredID(LCSSAID); |
| AU.addPreservedID(LCSSAID); |
| AU.addRequired<LoopInfo>(); |
| AU.addPreserved<LoopInfo>(); |
| AU.addRequiredID(LoopSimplifyID); |
| AU.addPreservedID(LoopSimplifyID); |
| AU.addRequired<DominatorTree>(); |
| AU.addRequired<DominanceFrontier>(); |
| AU.addPreserved<DominatorTree>(); |
| AU.addPreserved<DominanceFrontier>(); |
| } |
| |
| private: |
| |
| class SplitInfo { |
| public: |
| SplitInfo() : SplitValue(NULL), SplitCondition(NULL), |
| UseTrueBranchFirst(true), A_ExitValue(NULL), |
| B_StartValue(NULL) {} |
| |
| // Induction variable's range is split at this value. |
| Value *SplitValue; |
| |
| // This instruction compares IndVar against SplitValue. |
| Instruction *SplitCondition; |
| |
| // True if after loop index split, first loop will execute split condition's |
| // true branch. |
| bool UseTrueBranchFirst; |
| |
| // Exit value for first loop after loop split. |
| Value *A_ExitValue; |
| |
| // Start value for second loop after loop split. |
| Value *B_StartValue; |
| |
| // Clear split info. |
| void clear() { |
| SplitValue = NULL; |
| SplitCondition = NULL; |
| UseTrueBranchFirst = true; |
| A_ExitValue = NULL; |
| B_StartValue = NULL; |
| } |
| |
| }; |
| |
| private: |
| |
| // safeIcmpInst - CI is considered safe instruction if one of the operand |
| // is SCEVAddRecExpr based on induction variable and other operand is |
| // loop invariant. If CI is safe then populate SplitInfo object SD appropriately |
| // and return true; |
| bool safeICmpInst(ICmpInst *CI, SplitInfo &SD); |
| |
| /// Find condition inside a loop that is suitable candidate for index split. |
| void findSplitCondition(); |
| |
| /// Find loop's exit condition. |
| void findLoopConditionals(); |
| |
| /// Return induction variable associated with value V. |
| void findIndVar(Value *V, Loop *L); |
| |
| /// processOneIterationLoop - Current loop L contains compare instruction |
| /// that compares induction variable, IndVar, agains loop invariant. If |
| /// entire (i.e. meaningful) loop body is dominated by this compare |
| /// instruction then loop body is executed only for one iteration. In |
| /// such case eliminate loop structure surrounding this loop body. For |
| bool processOneIterationLoop(SplitInfo &SD); |
| |
| void updateLoopBounds(ICmpInst *CI); |
| /// updateLoopIterationSpace - Current loop body is covered by an AND |
| /// instruction whose operands compares induction variables with loop |
| /// invariants. If possible, hoist this check outside the loop by |
| /// updating appropriate start and end values for induction variable. |
| bool updateLoopIterationSpace(SplitInfo &SD); |
| |
| /// If loop header includes loop variant instruction operands then |
| /// this loop may not be eliminated. |
| bool safeHeader(SplitInfo &SD, BasicBlock *BB); |
| |
| /// If Exiting block includes loop variant instructions then this |
| /// loop may not be eliminated. |
| bool safeExitingBlock(SplitInfo &SD, BasicBlock *BB); |
| |
| /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB. |
| /// This routine is used to remove split condition's dead branch, dominated by |
| /// DeadBB. LiveBB dominates split conidition's other branch. |
| void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB); |
| |
| /// safeSplitCondition - Return true if it is possible to |
| /// split loop using given split condition. |
| bool safeSplitCondition(SplitInfo &SD); |
| |
| /// calculateLoopBounds - ALoop exit value and BLoop start values are calculated |
| /// based on split value. |
| void calculateLoopBounds(SplitInfo &SD); |
| |
| /// updatePHINodes - CFG has been changed. |
| /// Before |
| /// - ExitBB's single predecessor was Latch |
| /// - Latch's second successor was Header |
| /// Now |
| /// - ExitBB's single predecessor was Header |
| /// - Latch's one and only successor was Header |
| /// |
| /// Update ExitBB PHINodes' to reflect this change. |
| void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, |
| BasicBlock *Header, |
| PHINode *IV, Instruction *IVIncrement); |
| |
| /// moveExitCondition - Move exit condition EC into split condition block CondBB. |
| void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB, |
| BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC, |
| PHINode *IV, Instruction *IVAdd, Loop *LP); |
| |
| /// splitLoop - Split current loop L in two loops using split information |
| /// SD. Update dominator information. Maintain LCSSA form. |
| bool splitLoop(SplitInfo &SD); |
| |
| void initialize() { |
| IndVar = NULL; |
| IndVarIncrement = NULL; |
| ExitCondition = NULL; |
| StartValue = NULL; |
| ExitValueNum = 0; |
| SplitData.clear(); |
| } |
| |
| private: |
| |
| // Current Loop. |
| Loop *L; |
| LPPassManager *LPM; |
| LoopInfo *LI; |
| ScalarEvolution *SE; |
| DominatorTree *DT; |
| DominanceFrontier *DF; |
| SmallVector<SplitInfo, 4> SplitData; |
| |
| // Induction variable whose range is being split by this transformation. |
| PHINode *IndVar; |
| Instruction *IndVarIncrement; |
| |
| // Loop exit condition. |
| ICmpInst *ExitCondition; |
| |
| // Induction variable's initial value. |
| Value *StartValue; |
| |
| // Induction variable's final loop exit value operand number in exit condition.. |
| unsigned ExitValueNum; |
| }; |
| |
| char LoopIndexSplit::ID = 0; |
| RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops"); |
| } |
| |
| LoopPass *llvm::createLoopIndexSplitPass() { |
| return new LoopIndexSplit(); |
| } |
| |
| // Index split Loop L. Return true if loop is split. |
| bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) { |
| bool Changed = false; |
| L = IncomingLoop; |
| LPM = &LPM_Ref; |
| |
| // FIXME - Nested loops make dominator info updates tricky. |
| if (!L->getSubLoops().empty()) |
| return false; |
| |
| SE = &getAnalysis<ScalarEvolution>(); |
| DT = &getAnalysis<DominatorTree>(); |
| LI = &getAnalysis<LoopInfo>(); |
| DF = &getAnalysis<DominanceFrontier>(); |
| |
| initialize(); |
| |
| findLoopConditionals(); |
| |
| if (!ExitCondition) |
| return false; |
| |
| findSplitCondition(); |
| |
| if (SplitData.empty()) |
| return false; |
| |
| // First see if it is possible to eliminate loop itself or not. |
| for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(), |
| E = SplitData.end(); SI != E;) { |
| SplitInfo &SD = *SI; |
| ICmpInst *CI = dyn_cast<ICmpInst>(SD.SplitCondition); |
| if (SD.SplitCondition->getOpcode() == Instruction::And) { |
| Changed = updateLoopIterationSpace(SD); |
| if (Changed) { |
| ++NumIndexSplit; |
| // If is loop is eliminated then nothing else to do here. |
| return Changed; |
| } else { |
| SmallVector<SplitInfo, 4>::iterator Delete_SI = SI; |
| ++SI; |
| SplitData.erase(Delete_SI); |
| } |
| } |
| else if (CI && CI->getPredicate() == ICmpInst::ICMP_EQ) { |
| Changed = processOneIterationLoop(SD); |
| if (Changed) { |
| ++NumIndexSplit; |
| // If is loop is eliminated then nothing else to do here. |
| return Changed; |
| } else { |
| SmallVector<SplitInfo, 4>::iterator Delete_SI = SI; |
| ++SI; |
| SplitData.erase(Delete_SI); |
| } |
| } else |
| ++SI; |
| } |
| |
| if (SplitData.empty()) |
| return false; |
| |
| // Split most profitiable condition. |
| // FIXME : Implement cost analysis. |
| unsigned MostProfitableSDIndex = 0; |
| Changed = splitLoop(SplitData[MostProfitableSDIndex]); |
| |
| if (Changed) |
| ++NumIndexSplit; |
| |
| return Changed; |
| } |
| |
| /// Return true if V is a induction variable or induction variable's |
| /// increment for loop L. |
| void LoopIndexSplit::findIndVar(Value *V, Loop *L) { |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) |
| return; |
| |
| // Check if I is a phi node from loop header or not. |
| if (PHINode *PN = dyn_cast<PHINode>(V)) { |
| if (PN->getParent() == L->getHeader()) { |
| IndVar = PN; |
| return; |
| } |
| } |
| |
| // Check if I is a add instruction whose one operand is |
| // phi node from loop header and second operand is constant. |
| if (I->getOpcode() != Instruction::Add) |
| return; |
| |
| Value *Op0 = I->getOperand(0); |
| Value *Op1 = I->getOperand(1); |
| |
| if (PHINode *PN = dyn_cast<PHINode>(Op0)) |
| if (PN->getParent() == L->getHeader()) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) |
| if (CI->isOne()) { |
| IndVar = PN; |
| IndVarIncrement = I; |
| return; |
| } |
| |
| if (PHINode *PN = dyn_cast<PHINode>(Op1)) |
| if (PN->getParent() == L->getHeader()) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0)) |
| if (CI->isOne()) { |
| IndVar = PN; |
| IndVarIncrement = I; |
| return; |
| } |
| |
| return; |
| } |
| |
| // Find loop's exit condition and associated induction variable. |
| void LoopIndexSplit::findLoopConditionals() { |
| |
| BasicBlock *ExitingBlock = NULL; |
| |
| for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| I != E; ++I) { |
| BasicBlock *BB = *I; |
| if (!L->isLoopExit(BB)) |
| continue; |
| if (ExitingBlock) |
| return; |
| ExitingBlock = BB; |
| } |
| |
| if (!ExitingBlock) |
| return; |
| |
| // If exiting block is neither loop header nor loop latch then this loop is |
| // not suitable. |
| if (ExitingBlock != L->getHeader() && ExitingBlock != L->getLoopLatch()) |
| return; |
| |
| // If exit block's terminator is conditional branch inst then we have found |
| // exit condition. |
| BranchInst *BR = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); |
| if (!BR || BR->isUnconditional()) |
| return; |
| |
| ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition()); |
| if (!CI) |
| return; |
| |
| // FIXME |
| if (CI->getPredicate() == ICmpInst::ICMP_EQ |
| || CI->getPredicate() == ICmpInst::ICMP_NE) |
| return; |
| |
| ExitCondition = CI; |
| |
| // Exit condition's one operand is loop invariant exit value and second |
| // operand is SCEVAddRecExpr based on induction variable. |
| Value *V0 = CI->getOperand(0); |
| Value *V1 = CI->getOperand(1); |
| |
| SCEVHandle SH0 = SE->getSCEV(V0); |
| SCEVHandle SH1 = SE->getSCEV(V1); |
| |
| if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) { |
| ExitValueNum = 0; |
| findIndVar(V1, L); |
| } |
| else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) { |
| ExitValueNum = 1; |
| findIndVar(V0, L); |
| } |
| |
| if (!IndVar) |
| ExitCondition = NULL; |
| else if (IndVar) { |
| BasicBlock *Preheader = L->getLoopPreheader(); |
| StartValue = IndVar->getIncomingValueForBlock(Preheader); |
| } |
| } |
| |
| /// Find condition inside a loop that is suitable candidate for index split. |
| void LoopIndexSplit::findSplitCondition() { |
| |
| SplitInfo SD; |
| // Check all basic block's terminators. |
| for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| I != E; ++I) { |
| SD.clear(); |
| BasicBlock *BB = *I; |
| |
| // If this basic block does not terminate in a conditional branch |
| // then terminator is not a suitable split condition. |
| BranchInst *BR = dyn_cast<BranchInst>(BB->getTerminator()); |
| if (!BR) |
| continue; |
| |
| if (BR->isUnconditional()) |
| continue; |
| |
| if (Instruction *AndI = dyn_cast<Instruction>(BR->getCondition())) { |
| if (AndI->getOpcode() == Instruction::And) { |
| ICmpInst *Op0 = dyn_cast<ICmpInst>(AndI->getOperand(0)); |
| ICmpInst *Op1 = dyn_cast<ICmpInst>(AndI->getOperand(1)); |
| |
| if (!Op0 || !Op1) |
| continue; |
| |
| if (!safeICmpInst(Op0, SD)) |
| continue; |
| SD.clear(); |
| if (!safeICmpInst(Op1, SD)) |
| continue; |
| SD.clear(); |
| SD.SplitCondition = AndI; |
| SplitData.push_back(SD); |
| continue; |
| } |
| } |
| ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition()); |
| if (!CI || CI == ExitCondition) |
| continue; |
| |
| if (CI->getPredicate() == ICmpInst::ICMP_NE) |
| continue; |
| |
| // If split condition predicate is GT or GE then first execute |
| // false branch of split condition. |
| if (CI->getPredicate() == ICmpInst::ICMP_UGT |
| || CI->getPredicate() == ICmpInst::ICMP_SGT |
| || CI->getPredicate() == ICmpInst::ICMP_UGE |
| || CI->getPredicate() == ICmpInst::ICMP_SGE) |
| SD.UseTrueBranchFirst = false; |
| |
| // If one operand is loop invariant and second operand is SCEVAddRecExpr |
| // based on induction variable then CI is a candidate split condition. |
| if (safeICmpInst(CI, SD)) |
| SplitData.push_back(SD); |
| } |
| } |
| |
| // safeIcmpInst - CI is considered safe instruction if one of the operand |
| // is SCEVAddRecExpr based on induction variable and other operand is |
| // loop invariant. If CI is safe then populate SplitInfo object SD appropriately |
| // and return true; |
| bool LoopIndexSplit::safeICmpInst(ICmpInst *CI, SplitInfo &SD) { |
| |
| Value *V0 = CI->getOperand(0); |
| Value *V1 = CI->getOperand(1); |
| |
| SCEVHandle SH0 = SE->getSCEV(V0); |
| SCEVHandle SH1 = SE->getSCEV(V1); |
| |
| if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) { |
| SD.SplitValue = V0; |
| SD.SplitCondition = CI; |
| if (PHINode *PN = dyn_cast<PHINode>(V1)) { |
| if (PN == IndVar) |
| return true; |
| } |
| else if (Instruction *Insn = dyn_cast<Instruction>(V1)) { |
| if (IndVarIncrement && IndVarIncrement == Insn) |
| return true; |
| } |
| } |
| else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) { |
| SD.SplitValue = V1; |
| SD.SplitCondition = CI; |
| if (PHINode *PN = dyn_cast<PHINode>(V0)) { |
| if (PN == IndVar) |
| return true; |
| } |
| else if (Instruction *Insn = dyn_cast<Instruction>(V0)) { |
| if (IndVarIncrement && IndVarIncrement == Insn) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// processOneIterationLoop - Current loop L contains compare instruction |
| /// that compares induction variable, IndVar, against loop invariant. If |
| /// entire (i.e. meaningful) loop body is dominated by this compare |
| /// instruction then loop body is executed only once. In such case eliminate |
| /// loop structure surrounding this loop body. For example, |
| /// for (int i = start; i < end; ++i) { |
| /// if ( i == somevalue) { |
| /// loop_body |
| /// } |
| /// } |
| /// can be transformed into |
| /// if (somevalue >= start && somevalue < end) { |
| /// i = somevalue; |
| /// loop_body |
| /// } |
| bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) { |
| |
| BasicBlock *Header = L->getHeader(); |
| |
| // First of all, check if SplitCondition dominates entire loop body |
| // or not. |
| |
| // If SplitCondition is not in loop header then this loop is not suitable |
| // for this transformation. |
| if (SD.SplitCondition->getParent() != Header) |
| return false; |
| |
| // If loop header includes loop variant instruction operands then |
| // this loop may not be eliminated. |
| if (!safeHeader(SD, Header)) |
| return false; |
| |
| // If Exiting block includes loop variant instructions then this |
| // loop may not be eliminated. |
| if (!safeExitingBlock(SD, ExitCondition->getParent())) |
| return false; |
| |
| // Filter loops where split condition's false branch is not empty. |
| if (ExitCondition->getParent() != Header->getTerminator()->getSuccessor(1)) |
| return false; |
| |
| // If split condition is not safe then do not process this loop. |
| // For example, |
| // for(int i = 0; i < N; i++) { |
| // if ( i == XYZ) { |
| // A; |
| // else |
| // B; |
| // } |
| // C; |
| // D; |
| // } |
| if (!safeSplitCondition(SD)) |
| return false; |
| |
| BasicBlock *Latch = L->getLoopLatch(); |
| BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator()); |
| if (!BR) |
| return false; |
| |
| // Update CFG. |
| |
| // Replace index variable with split value in loop body. Loop body is executed |
| // only when index variable is equal to split value. |
| IndVar->replaceAllUsesWith(SD.SplitValue); |
| |
| // Remove Latch to Header edge. |
| BasicBlock *LatchSucc = NULL; |
| Header->removePredecessor(Latch); |
| for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch); |
| SI != E; ++SI) { |
| if (Header != *SI) |
| LatchSucc = *SI; |
| } |
| BR->setUnconditionalDest(LatchSucc); |
| |
| Instruction *Terminator = Header->getTerminator(); |
| Value *ExitValue = ExitCondition->getOperand(ExitValueNum); |
| |
| // Replace split condition in header. |
| // Transform |
| // SplitCondition : icmp eq i32 IndVar, SplitValue |
| // into |
| // c1 = icmp uge i32 SplitValue, StartValue |
| // c2 = icmp ult i32 SplitValue, ExitValue |
| // and i32 c1, c2 |
| bool SignedPredicate = ExitCondition->isSignedPredicate(); |
| Instruction *C1 = new ICmpInst(SignedPredicate ? |
| ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE, |
| SD.SplitValue, StartValue, "lisplit", |
| Terminator); |
| Instruction *C2 = new ICmpInst(SignedPredicate ? |
| ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| SD.SplitValue, ExitValue, "lisplit", |
| Terminator); |
| Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit", |
| Terminator); |
| SD.SplitCondition->replaceAllUsesWith(NSplitCond); |
| SD.SplitCondition->eraseFromParent(); |
| |
| // Now, clear latch block. Remove instructions that are responsible |
| // to increment induction variable. |
| Instruction *LTerminator = Latch->getTerminator(); |
| for (BasicBlock::iterator LB = Latch->begin(), LE = Latch->end(); |
| LB != LE; ) { |
| Instruction *I = LB; |
| ++LB; |
| if (isa<PHINode>(I) || I == LTerminator) |
| continue; |
| |
| if (I == IndVarIncrement) |
| I->replaceAllUsesWith(ExitValue); |
| else |
| I->replaceAllUsesWith(UndefValue::get(I->getType())); |
| I->eraseFromParent(); |
| } |
| |
| LPM->deleteLoopFromQueue(L); |
| |
| // Update Dominator Info. |
| // Only CFG change done is to remove Latch to Header edge. This |
| // does not change dominator tree because Latch did not dominate |
| // Header. |
| if (DF) { |
| DominanceFrontier::iterator HeaderDF = DF->find(Header); |
| if (HeaderDF != DF->end()) |
| DF->removeFromFrontier(HeaderDF, Header); |
| |
| DominanceFrontier::iterator LatchDF = DF->find(Latch); |
| if (LatchDF != DF->end()) |
| DF->removeFromFrontier(LatchDF, Header); |
| } |
| return true; |
| } |
| |
| // If loop header includes loop variant instruction operands then |
| // this loop can not be eliminated. This is used by processOneIterationLoop(). |
| bool LoopIndexSplit::safeHeader(SplitInfo &SD, BasicBlock *Header) { |
| |
| Instruction *Terminator = Header->getTerminator(); |
| for(BasicBlock::iterator BI = Header->begin(), BE = Header->end(); |
| BI != BE; ++BI) { |
| Instruction *I = BI; |
| |
| // PHI Nodes are OK. |
| if (isa<PHINode>(I)) |
| continue; |
| |
| // SplitCondition itself is OK. |
| if (I == SD.SplitCondition) |
| continue; |
| |
| // Induction variable is OK. |
| if (I == IndVar) |
| continue; |
| |
| // Induction variable increment is OK. |
| if (I == IndVarIncrement) |
| continue; |
| |
| // Terminator is also harmless. |
| if (I == Terminator) |
| continue; |
| |
| // Otherwise we have a instruction that may not be safe. |
| return false; |
| } |
| |
| return true; |
| } |
| |
| // If Exiting block includes loop variant instructions then this |
| // loop may not be eliminated. This is used by processOneIterationLoop(). |
| bool LoopIndexSplit::safeExitingBlock(SplitInfo &SD, |
| BasicBlock *ExitingBlock) { |
| |
| for (BasicBlock::iterator BI = ExitingBlock->begin(), |
| BE = ExitingBlock->end(); BI != BE; ++BI) { |
| Instruction *I = BI; |
| |
| // PHI Nodes are OK. |
| if (isa<PHINode>(I)) |
| continue; |
| |
| // Induction variable increment is OK. |
| if (IndVarIncrement && IndVarIncrement == I) |
| continue; |
| |
| // Check if I is induction variable increment instruction. |
| if (I->getOpcode() == Instruction::Add) { |
| |
| Value *Op0 = I->getOperand(0); |
| Value *Op1 = I->getOperand(1); |
| PHINode *PN = NULL; |
| ConstantInt *CI = NULL; |
| |
| if ((PN = dyn_cast<PHINode>(Op0))) { |
| if ((CI = dyn_cast<ConstantInt>(Op1))) |
| if (CI->isOne()) { |
| if (!IndVarIncrement && PN == IndVar) |
| IndVarIncrement = I; |
| // else this is another loop induction variable |
| continue; |
| } |
| } else |
| if ((PN = dyn_cast<PHINode>(Op1))) { |
| if ((CI = dyn_cast<ConstantInt>(Op0))) |
| if (CI->isOne()) { |
| if (!IndVarIncrement && PN == IndVar) |
| IndVarIncrement = I; |
| // else this is another loop induction variable |
| continue; |
| } |
| } |
| } |
| |
| // I is an Exit condition if next instruction is block terminator. |
| // Exit condition is OK if it compares loop invariant exit value, |
| // which is checked below. |
| else if (ICmpInst *EC = dyn_cast<ICmpInst>(I)) { |
| if (EC == ExitCondition) |
| continue; |
| } |
| |
| if (I == ExitingBlock->getTerminator()) |
| continue; |
| |
| // Otherwise we have instruction that may not be safe. |
| return false; |
| } |
| |
| // We could not find any reason to consider ExitingBlock unsafe. |
| return true; |
| } |
| |
| void LoopIndexSplit::updateLoopBounds(ICmpInst *CI) { |
| |
| Value *V0 = CI->getOperand(0); |
| Value *V1 = CI->getOperand(1); |
| Value *NV = NULL; |
| |
| SCEVHandle SH0 = SE->getSCEV(V0); |
| |
| if (SH0->isLoopInvariant(L)) |
| NV = V0; |
| else |
| NV = V1; |
| |
| if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) { |
| ExitCondition->swapOperands(); |
| if (ExitValueNum) |
| ExitValueNum = 0; |
| else |
| ExitValueNum = 1; |
| } |
| |
| Value *NUB = NULL; |
| Value *NLB = NULL; |
| Value *UB = ExitCondition->getOperand(ExitValueNum); |
| const Type *Ty = NV->getType(); |
| bool Sign = ExitCondition->isSignedPredicate(); |
| BasicBlock *Preheader = L->getLoopPreheader(); |
| Instruction *PHTerminator = Preheader->getTerminator(); |
| |
| assert (NV && "Unexpected value"); |
| |
| switch (CI->getPredicate()) { |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| // for (i = LB; i < UB; ++i) |
| // if (i <= NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NUB = min (NV+1, UB) |
| // for (i = LB; i < NUB ; ++i) |
| // LOOP_BODY |
| // |
| if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) { |
| Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| A, UB,"lsplit,c", PHTerminator); |
| NUB = new SelectInst (C, A, UB, "lsplit.nub", PHTerminator); |
| } |
| |
| // for (i = LB; i <= UB; ++i) |
| // if (i <= NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NUB = min (NV, UB) |
| // for (i = LB; i <= NUB ; ++i) |
| // LOOP_BODY |
| // |
| else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) { |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| NV, UB, "lsplit.c", PHTerminator); |
| NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator); |
| } |
| break; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| // for (i = LB; i < UB; ++i) |
| // if (i < NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NUB = min (NV, UB) |
| // for (i = LB; i < NUB ; ++i) |
| // LOOP_BODY |
| // |
| if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) { |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| NV, UB, "lsplit.c", PHTerminator); |
| NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator); |
| } |
| |
| // for (i = LB; i <= UB; ++i) |
| // if (i < NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NUB = min (NV -1 , UB) |
| // for (i = LB; i <= NUB ; ++i) |
| // LOOP_BODY |
| // |
| else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) { |
| Value *S = BinaryOperator::createSub(NV, ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| S, UB, "lsplit.c", PHTerminator); |
| NUB = new SelectInst (C, S, UB, "lsplit.nub", PHTerminator); |
| } |
| break; |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| // for (i = LB; i (< or <=) UB; ++i) |
| // if (i >= NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NLB = max (NV, LB) |
| // for (i = NLB; i (< or <=) UB ; ++i) |
| // LOOP_BODY |
| // |
| { |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| NV, StartValue, "lsplit.c", PHTerminator); |
| NLB = new SelectInst (C, StartValue, NV, "lsplit.nlb", PHTerminator); |
| } |
| break; |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| // for (i = LB; i (< or <=) UB; ++i) |
| // if (i > NV && ...) |
| // LOOP_BODY |
| // |
| // is transformed into |
| // NLB = max (NV+1, LB) |
| // for (i = NLB; i (< or <=) UB ; ++i) |
| // LOOP_BODY |
| // |
| { |
| Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| A, StartValue, "lsplit.c", PHTerminator); |
| NLB = new SelectInst (C, StartValue, A, "lsplit.nlb", PHTerminator); |
| } |
| break; |
| default: |
| assert ( 0 && "Unexpected split condition predicate"); |
| } |
| |
| if (NLB) { |
| unsigned i = IndVar->getBasicBlockIndex(Preheader); |
| IndVar->setIncomingValue(i, NLB); |
| } |
| |
| if (NUB) { |
| ExitCondition->setOperand(ExitValueNum, NUB); |
| } |
| } |
| /// updateLoopIterationSpace - Current loop body is covered by an AND |
| /// instruction whose operands compares induction variables with loop |
| /// invariants. If possible, hoist this check outside the loop by |
| /// updating appropriate start and end values for induction variable. |
| bool LoopIndexSplit::updateLoopIterationSpace(SplitInfo &SD) { |
| BasicBlock *Header = L->getHeader(); |
| BasicBlock *ExitingBlock = ExitCondition->getParent(); |
| BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
| |
| ICmpInst *Op0 = cast<ICmpInst>(SD.SplitCondition->getOperand(0)); |
| ICmpInst *Op1 = cast<ICmpInst>(SD.SplitCondition->getOperand(1)); |
| |
| if (Op0->getPredicate() == ICmpInst::ICMP_EQ |
| || Op0->getPredicate() == ICmpInst::ICMP_NE |
| || Op0->getPredicate() == ICmpInst::ICMP_EQ |
| || Op0->getPredicate() == ICmpInst::ICMP_NE) |
| return false; |
| |
| // Check if SplitCondition dominates entire loop body |
| // or not. |
| |
| // If SplitCondition is not in loop header then this loop is not suitable |
| // for this transformation. |
| if (SD.SplitCondition->getParent() != Header) |
| return false; |
| |
| // If loop header includes loop variant instruction operands then |
| // this loop may not be eliminated. |
| Instruction *Terminator = Header->getTerminator(); |
| for(BasicBlock::iterator BI = Header->begin(), BE = Header->end(); |
| BI != BE; ++BI) { |
| Instruction *I = BI; |
| |
| // PHI Nodes are OK. |
| if (isa<PHINode>(I)) |
| continue; |
| |
| // SplitCondition itself is OK. |
| if (I == SD.SplitCondition) |
| continue; |
| if (I == Op0 || I == Op1) |
| continue; |
| |
| // Induction variable is OK. |
| if (I == IndVar) |
| continue; |
| |
| // Induction variable increment is OK. |
| if (I == IndVarIncrement) |
| continue; |
| |
| // Terminator is also harmless. |
| if (I == Terminator) |
| continue; |
| |
| // Otherwise we have a instruction that may not be safe. |
| return false; |
| } |
| |
| // If Exiting block includes loop variant instructions then this |
| // loop may not be eliminated. |
| if (!safeExitingBlock(SD, ExitCondition->getParent())) |
| return false; |
| |
| // Verify that loop exiting block has only two predecessor, where one predecessor |
| // is split condition block. The other predecessor will become exiting block's |
| // dominator after CFG is updated. TODO : Handle CFG's where exiting block has |
| // more then two predecessors. This requires extra work in updating dominator |
| // information. |
| BasicBlock *ExitingBBPred = NULL; |
| for (pred_iterator PI = pred_begin(ExitingBlock), PE = pred_end(ExitingBlock); |
| PI != PE; ++PI) { |
| BasicBlock *BB = *PI; |
| if (SplitCondBlock == BB) |
| continue; |
| if (ExitingBBPred) |
| return false; |
| else |
| ExitingBBPred = BB; |
| } |
| |
| // Update loop bounds to absorb Op0 check. |
| updateLoopBounds(Op0); |
| // Update loop bounds to absorb Op1 check. |
| updateLoopBounds(Op1); |
| |
| // Update CFG |
| |
| // Unconditionally connect split block to its remaining successor. |
| BranchInst *SplitTerminator = |
| cast<BranchInst>(SplitCondBlock->getTerminator()); |
| BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
| if (Succ0 == ExitCondition->getParent()) |
| SplitTerminator->setUnconditionalDest(Succ1); |
| else |
| SplitTerminator->setUnconditionalDest(Succ0); |
| |
| // Remove split condition. |
| SD.SplitCondition->eraseFromParent(); |
| if (Op0->use_begin() == Op0->use_end()) |
| Op0->eraseFromParent(); |
| if (Op1->use_begin() == Op1->use_end()) |
| Op1->eraseFromParent(); |
| |
| BranchInst *ExitInsn = |
| dyn_cast<BranchInst>(ExitingBlock->getTerminator()); |
| assert (ExitInsn && "Unable to find suitable loop exit branch"); |
| BasicBlock *ExitBlock = ExitInsn->getSuccessor(1); |
| if (L->contains(ExitBlock)) |
| ExitBlock = ExitInsn->getSuccessor(0); |
| |
| // Update domiantor info. Now, ExitingBlock has only one predecessor, |
| // ExitingBBPred, and it is ExitingBlock's immediate domiantor. |
| DT->changeImmediateDominator(ExitingBlock, ExitingBBPred); |
| |
| // If ExitingBlock is a member of loop BB's DF list then replace it with |
| // loop header and exit block. |
| for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| I != E; ++I) { |
| BasicBlock *BB = *I; |
| if (BB == Header || BB == ExitingBlock) |
| continue; |
| DominanceFrontier::iterator BBDF = DF->find(BB); |
| DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin(); |
| DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end(); |
| while (DomSetI != DomSetE) { |
| DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI; |
| ++DomSetI; |
| BasicBlock *DFBB = *CurrentItr; |
| if (DFBB == ExitingBlock) { |
| BBDF->second.erase(DFBB); |
| BBDF->second.insert(Header); |
| if (Header != ExitingBlock) |
| BBDF->second.insert(ExitBlock); |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB. |
| /// This routine is used to remove split condition's dead branch, dominated by |
| /// DeadBB. LiveBB dominates split conidition's other branch. |
| void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP, |
| BasicBlock *LiveBB) { |
| |
| // First update DeadBB's dominance frontier. |
| SmallVector<BasicBlock *, 8> FrontierBBs; |
| DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB); |
| if (DeadBBDF != DF->end()) { |
| SmallVector<BasicBlock *, 8> PredBlocks; |
| |
| DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second; |
| for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(), |
| DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) { |
| BasicBlock *FrontierBB = *DeadBBSetI; |
| FrontierBBs.push_back(FrontierBB); |
| |
| // Rremove any PHI incoming edge from blocks dominated by DeadBB. |
| PredBlocks.clear(); |
| for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB); |
| PI != PE; ++PI) { |
| BasicBlock *P = *PI; |
| if (P == DeadBB || DT->dominates(DeadBB, P)) |
| PredBlocks.push_back(P); |
| } |
| |
| for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end(); |
| FBI != FBE; ++FBI) { |
| if (PHINode *PN = dyn_cast<PHINode>(FBI)) { |
| for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(), |
| PE = PredBlocks.end(); PI != PE; ++PI) { |
| BasicBlock *P = *PI; |
| PN->removeIncomingValue(P); |
| } |
| } |
| else |
| break; |
| } |
| } |
| } |
| |
| // Now remove DeadBB and all nodes dominated by DeadBB in df order. |
| SmallVector<BasicBlock *, 32> WorkList; |
| DomTreeNode *DN = DT->getNode(DeadBB); |
| for (df_iterator<DomTreeNode*> DI = df_begin(DN), |
| E = df_end(DN); DI != E; ++DI) { |
| BasicBlock *BB = DI->getBlock(); |
| WorkList.push_back(BB); |
| BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy)); |
| } |
| |
| while (!WorkList.empty()) { |
| BasicBlock *BB = WorkList.back(); WorkList.pop_back(); |
| for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end(); |
| BBI != BBE; ) { |
| Instruction *I = BBI; |
| ++BBI; |
| I->replaceAllUsesWith(UndefValue::get(I->getType())); |
| I->eraseFromParent(); |
| } |
| LPM->deleteSimpleAnalysisValue(BB, LP); |
| DT->eraseNode(BB); |
| DF->removeBlock(BB); |
| LI->removeBlock(BB); |
| BB->eraseFromParent(); |
| } |
| |
| // Update Frontier BBs' dominator info. |
| while (!FrontierBBs.empty()) { |
| BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back(); |
| BasicBlock *NewDominator = FBB->getSinglePredecessor(); |
| if (!NewDominator) { |
| pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB); |
| NewDominator = *PI; |
| ++PI; |
| if (NewDominator != LiveBB) { |
| for(; PI != PE; ++PI) { |
| BasicBlock *P = *PI; |
| if (P == LiveBB) { |
| NewDominator = LiveBB; |
| break; |
| } |
| NewDominator = DT->findNearestCommonDominator(NewDominator, P); |
| } |
| } |
| } |
| assert (NewDominator && "Unable to fix dominator info."); |
| DT->changeImmediateDominator(FBB, NewDominator); |
| DF->changeImmediateDominator(FBB, NewDominator, DT); |
| } |
| |
| } |
| |
| /// safeSplitCondition - Return true if it is possible to |
| /// split loop using given split condition. |
| bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) { |
| |
| BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
| BasicBlock *Latch = L->getLoopLatch(); |
| BranchInst *SplitTerminator = |
| cast<BranchInst>(SplitCondBlock->getTerminator()); |
| BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
| |
| // Finally this split condition is safe only if merge point for |
| // split condition branch is loop latch. This check along with previous |
| // check, to ensure that exit condition is in either loop latch or header, |
| // filters all loops with non-empty loop body between merge point |
| // and exit condition. |
| DominanceFrontier::iterator Succ0DF = DF->find(Succ0); |
| assert (Succ0DF != DF->end() && "Unable to find Succ0 dominance frontier"); |
| if (Succ0DF->second.count(Latch)) |
| return true; |
| |
| DominanceFrontier::iterator Succ1DF = DF->find(Succ1); |
| assert (Succ1DF != DF->end() && "Unable to find Succ1 dominance frontier"); |
| if (Succ1DF->second.count(Latch)) |
| return true; |
| |
| return false; |
| } |
| |
| /// calculateLoopBounds - ALoop exit value and BLoop start values are calculated |
| /// based on split value. |
| void LoopIndexSplit::calculateLoopBounds(SplitInfo &SD) { |
| |
| ICmpInst *SC = cast<ICmpInst>(SD.SplitCondition); |
| ICmpInst::Predicate SP = SC->getPredicate(); |
| const Type *Ty = SD.SplitValue->getType(); |
| bool Sign = ExitCondition->isSignedPredicate(); |
| BasicBlock *Preheader = L->getLoopPreheader(); |
| Instruction *PHTerminator = Preheader->getTerminator(); |
| |
| // Initially use split value as upper loop bound for first loop and lower loop |
| // bound for second loop. |
| Value *AEV = SD.SplitValue; |
| Value *BSV = SD.SplitValue; |
| |
| if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE |
| || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) |
| ExitCondition->swapOperands(); |
| |
| switch (ExitCondition->getPredicate()) { |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGE: |
| case ICmpInst::ICMP_UGE: |
| default: |
| assert (0 && "Unexpected exit condition predicate"); |
| |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_ULT: |
| { |
| switch (SP) { |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_ULT: |
| // |
| // for (i = LB; i < UB; ++i) { if (i < SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = BSV = SV |
| // for (i = LB; i < min(UB, AEV); ++i) |
| // A; |
| // for (i = max(LB, BSV); i < UB; ++i); |
| // B; |
| break; |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_ULE: |
| { |
| // |
| // for (i = LB; i < UB; ++i) { if (i <= SV) A; else B; } |
| // |
| // is transformed into |
| // |
| // AEV = SV + 1 |
| // BSV = SV + 1 |
| // for (i = LB; i < min(UB, AEV); ++i) |
| // A; |
| // for (i = max(LB, BSV); i < UB; ++i) |
| // B; |
| BSV = BinaryOperator::createAdd(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| AEV = BSV; |
| } |
| break; |
| case ICmpInst::ICMP_SGE: |
| case ICmpInst::ICMP_UGE: |
| // |
| // for (i = LB; i < UB; ++i) { if (i >= SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = BSV = SV |
| // for (i = LB; i < min(UB, AEV); ++i) |
| // B; |
| // for (i = max(BSV, LB); i < UB; ++i) |
| // A; |
| break; |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_UGT: |
| { |
| // |
| // for (i = LB; i < UB; ++i) { if (i > SV) A; else B; } |
| // |
| // is transformed into |
| // |
| // BSV = AEV = SV + 1 |
| // for (i = LB; i < min(UB, AEV); ++i) |
| // B; |
| // for (i = max(LB, BSV); i < UB; ++i) |
| // A; |
| BSV = BinaryOperator::createAdd(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| AEV = BSV; |
| } |
| break; |
| default: |
| assert (0 && "Unexpected split condition predicate"); |
| break; |
| } // end switch (SP) |
| } |
| break; |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_ULE: |
| { |
| switch (SP) { |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_ULT: |
| // |
| // for (i = LB; i <= UB; ++i) { if (i < SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = SV - 1; |
| // BSV = SV; |
| // for (i = LB; i <= min(UB, AEV); ++i) |
| // A; |
| // for (i = max(LB, BSV); i <= UB; ++i) |
| // B; |
| AEV = BinaryOperator::createSub(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.sub", PHTerminator); |
| break; |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_ULE: |
| // |
| // for (i = LB; i <= UB; ++i) { if (i <= SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = SV; |
| // BSV = SV + 1; |
| // for (i = LB; i <= min(UB, AEV); ++i) |
| // A; |
| // for (i = max(LB, BSV); i <= UB; ++i) |
| // B; |
| BSV = BinaryOperator::createAdd(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| break; |
| case ICmpInst::ICMP_SGT: |
| case ICmpInst::ICMP_UGT: |
| // |
| // for (i = LB; i <= UB; ++i) { if (i > SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = SV; |
| // BSV = SV + 1; |
| // for (i = LB; i <= min(AEV, UB); ++i) |
| // B; |
| // for (i = max(LB, BSV); i <= UB; ++i) |
| // A; |
| BSV = BinaryOperator::createAdd(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.add", PHTerminator); |
| break; |
| case ICmpInst::ICMP_SGE: |
| case ICmpInst::ICMP_UGE: |
| // ** TODO ** |
| // |
| // for (i = LB; i <= UB; ++i) { if (i >= SV) A; else B; } |
| // |
| // is transformed into |
| // AEV = SV - 1; |
| // BSV = SV; |
| // for (i = LB; i <= min(AEV, UB); ++i) |
| // B; |
| // for (i = max(LB, BSV); i <= UB; ++i) |
| // A; |
| AEV = BinaryOperator::createSub(SD.SplitValue, |
| ConstantInt::get(Ty, 1, Sign), |
| "lsplit.sub", PHTerminator); |
| break; |
| default: |
| assert (0 && "Unexpected split condition predicate"); |
| break; |
| } // end switch (SP) |
| } |
| break; |
| } |
| |
| // Calculate ALoop induction variable's new exiting value and |
| // BLoop induction variable's new starting value. Calculuate these |
| // values in original loop's preheader. |
| // A_ExitValue = min(SplitValue, OrignalLoopExitValue) |
| // B_StartValue = max(SplitValue, OriginalLoopStartValue) |
| Instruction *InsertPt = L->getHeader()->getFirstNonPHI(); |
| |
| // If ExitValue operand is also defined in Loop header then |
| // insert new ExitValue after this operand definition. |
| if (Instruction *EVN = |
| dyn_cast<Instruction>(ExitCondition->getOperand(ExitValueNum))) { |
| if (!isa<PHINode>(EVN)) |
| if (InsertPt->getParent() == EVN->getParent()) { |
| BasicBlock::iterator LHBI = L->getHeader()->begin(); |
| BasicBlock::iterator LHBE = L->getHeader()->end(); |
| for(;LHBI != LHBE; ++LHBI) { |
| Instruction *I = LHBI; |
| if (I == EVN) |
| break; |
| } |
| InsertPt = ++LHBI; |
| } |
| } |
| Value *C1 = new ICmpInst(Sign ? |
| ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| AEV, |
| ExitCondition->getOperand(ExitValueNum), |
| "lsplit.ev", InsertPt); |
| |
| SD.A_ExitValue = new SelectInst(C1, AEV, |
| ExitCondition->getOperand(ExitValueNum), |
| "lsplit.ev", InsertPt); |
| |
| Value *C2 = new ICmpInst(Sign ? |
| ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| BSV, StartValue, "lsplit.sv", |
| PHTerminator); |
| SD.B_StartValue = new SelectInst(C2, StartValue, BSV, |
| "lsplit.sv", PHTerminator); |
| } |
| |
| /// splitLoop - Split current loop L in two loops using split information |
| /// SD. Update dominator information. Maintain LCSSA form. |
| bool LoopIndexSplit::splitLoop(SplitInfo &SD) { |
| |
| if (!safeSplitCondition(SD)) |
| return false; |
| |
| BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
| |
| // Unable to handle triange loops at the moment. |
| // In triangle loop, split condition is in header and one of the |
| // the split destination is loop latch. If split condition is EQ |
| // then such loops are already handle in processOneIterationLoop(). |
| BasicBlock *Latch = L->getLoopLatch(); |
| BranchInst *SplitTerminator = |
| cast<BranchInst>(SplitCondBlock->getTerminator()); |
| BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
| if (L->getHeader() == SplitCondBlock |
| && (Latch == Succ0 || Latch == Succ1)) |
| return false; |
| |
| // If split condition branches heads do not have single predecessor, |
| // SplitCondBlock, then is not possible to remove inactive branch. |
| if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor()) |
| return false; |
| |
| // After loop is cloned there are two loops. |
| // |
| // First loop, referred as ALoop, executes first part of loop's iteration |
| // space split. Second loop, referred as BLoop, executes remaining |
| // part of loop's iteration space. |
| // |
| // ALoop's exit edge enters BLoop's header through a forwarding block which |
| // acts as a BLoop's preheader. |
| BasicBlock *Preheader = L->getLoopPreheader(); |
| |
| // Calculate ALoop induction variable's new exiting value and |
| // BLoop induction variable's new starting value. |
| calculateLoopBounds(SD); |
| |
| //[*] Clone loop. |
| DenseMap<const Value *, Value *> ValueMap; |
| Loop *BLoop = CloneLoop(L, LPM, LI, ValueMap, this); |
| Loop *ALoop = L; |
| BasicBlock *B_Header = BLoop->getHeader(); |
| |
| //[*] ALoop's exiting edge BLoop's header. |
| // ALoop's original exit block becomes BLoop's exit block. |
| PHINode *B_IndVar = cast<PHINode>(ValueMap[IndVar]); |
| BasicBlock *A_ExitingBlock = ExitCondition->getParent(); |
| BranchInst *A_ExitInsn = |
| dyn_cast<BranchInst>(A_ExitingBlock->getTerminator()); |
| assert (A_ExitInsn && "Unable to find suitable loop exit branch"); |
| BasicBlock *B_ExitBlock = A_ExitInsn->getSuccessor(1); |
| if (L->contains(B_ExitBlock)) { |
| B_ExitBlock = A_ExitInsn->getSuccessor(0); |
| A_ExitInsn->setSuccessor(0, B_Header); |
| } else |
| A_ExitInsn->setSuccessor(1, B_Header); |
| |
| //[*] Update ALoop's exit value using new exit value. |
| ExitCondition->setOperand(ExitValueNum, SD.A_ExitValue); |
| |
| // [*] Update BLoop's header phi nodes. Remove incoming PHINode's from |
| // original loop's preheader. Add incoming PHINode values from |
| // ALoop's exiting block. Update BLoop header's domiantor info. |
| |
| // Collect inverse map of Header PHINodes. |
| DenseMap<Value *, Value *> InverseMap; |
| for (BasicBlock::iterator BI = L->getHeader()->begin(), |
| BE = L->getHeader()->end(); BI != BE; ++BI) { |
| if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
| PHINode *PNClone = cast<PHINode>(ValueMap[PN]); |
| InverseMap[PNClone] = PN; |
| } else |
| break; |
| } |
| |
| for (BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end(); |
| BI != BE; ++BI) { |
| if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
| // Remove incoming value from original preheader. |
| PN->removeIncomingValue(Preheader); |
| |
| // Add incoming value from A_ExitingBlock. |
| if (PN == B_IndVar) |
| PN->addIncoming(SD.B_StartValue, A_ExitingBlock); |
| else { |
| PHINode *OrigPN = cast<PHINode>(InverseMap[PN]); |
| Value *V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock); |
| PN->addIncoming(V2, A_ExitingBlock); |
| } |
| } else |
| break; |
| } |
| DT->changeImmediateDominator(B_Header, A_ExitingBlock); |
| DF->changeImmediateDominator(B_Header, A_ExitingBlock, DT); |
| |
| // [*] Update BLoop's exit block. Its new predecessor is BLoop's exit |
| // block. Remove incoming PHINode values from ALoop's exiting block. |
| // Add new incoming values from BLoop's incoming exiting value. |
| // Update BLoop exit block's dominator info.. |
| BasicBlock *B_ExitingBlock = cast<BasicBlock>(ValueMap[A_ExitingBlock]); |
| for (BasicBlock::iterator BI = B_ExitBlock->begin(), BE = B_ExitBlock->end(); |
| BI != BE; ++BI) { |
| if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
| PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(A_ExitingBlock)], |
| B_ExitingBlock); |
| PN->removeIncomingValue(A_ExitingBlock); |
| } else |
| break; |
| } |
| |
| DT->changeImmediateDominator(B_ExitBlock, B_ExitingBlock); |
| DF->changeImmediateDominator(B_ExitBlock, B_ExitingBlock, DT); |
| |
| //[*] Split ALoop's exit edge. This creates a new block which |
| // serves two purposes. First one is to hold PHINode defnitions |
| // to ensure that ALoop's LCSSA form. Second use it to act |
| // as a preheader for BLoop. |
| BasicBlock *A_ExitBlock = SplitEdge(A_ExitingBlock, B_Header, this); |
| |
| //[*] Preserve ALoop's LCSSA form. Create new forwarding PHINodes |
| // in A_ExitBlock to redefine outgoing PHI definitions from ALoop. |
| for(BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end(); |
| BI != BE; ++BI) { |
| if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
| Value *V1 = PN->getIncomingValueForBlock(A_ExitBlock); |
| PHINode *newPHI = new PHINode(PN->getType(), PN->getName()); |
| newPHI->addIncoming(V1, A_ExitingBlock); |
| A_ExitBlock->getInstList().push_front(newPHI); |
| PN->removeIncomingValue(A_ExitBlock); |
| PN->addIncoming(newPHI, A_ExitBlock); |
| } else |
| break; |
| } |
| |
| //[*] Eliminate split condition's inactive branch from ALoop. |
| BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent(); |
| BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator()); |
| BasicBlock *A_InactiveBranch = NULL; |
| BasicBlock *A_ActiveBranch = NULL; |
| if (SD.UseTrueBranchFirst) { |
| A_ActiveBranch = A_BR->getSuccessor(0); |
| A_InactiveBranch = A_BR->getSuccessor(1); |
| } else { |
| A_ActiveBranch = A_BR->getSuccessor(1); |
| A_InactiveBranch = A_BR->getSuccessor(0); |
| } |
| A_BR->setUnconditionalDest(A_ActiveBranch); |
| removeBlocks(A_InactiveBranch, L, A_ActiveBranch); |
| |
| //[*] Eliminate split condition's inactive branch in from BLoop. |
| BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]); |
| BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator()); |
| BasicBlock *B_InactiveBranch = NULL; |
| BasicBlock *B_ActiveBranch = NULL; |
| if (SD.UseTrueBranchFirst) { |
| B_ActiveBranch = B_BR->getSuccessor(1); |
| B_InactiveBranch = B_BR->getSuccessor(0); |
| } else { |
| B_ActiveBranch = B_BR->getSuccessor(0); |
| B_InactiveBranch = B_BR->getSuccessor(1); |
| } |
| B_BR->setUnconditionalDest(B_ActiveBranch); |
| removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch); |
| |
| BasicBlock *A_Header = L->getHeader(); |
| if (A_ExitingBlock == A_Header) |
| return true; |
| |
| //[*] Move exit condition into split condition block to avoid |
| // executing dead loop iteration. |
| ICmpInst *B_ExitCondition = cast<ICmpInst>(ValueMap[ExitCondition]); |
| Instruction *B_IndVarIncrement = cast<Instruction>(ValueMap[IndVarIncrement]); |
| ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SD.SplitCondition]); |
| |
| moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition, |
| cast<ICmpInst>(SD.SplitCondition), IndVar, IndVarIncrement, |
| ALoop); |
| |
| moveExitCondition(B_SplitCondBlock, B_ActiveBranch, B_ExitBlock, B_ExitCondition, |
| B_SplitCondition, B_IndVar, B_IndVarIncrement, BLoop); |
| |
| return true; |
| } |
| |
| // moveExitCondition - Move exit condition EC into split condition block CondBB. |
| void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB, |
| BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC, |
| PHINode *IV, Instruction *IVAdd, Loop *LP) { |
| |
| BasicBlock *ExitingBB = EC->getParent(); |
| Instruction *CurrentBR = CondBB->getTerminator(); |
| |
| // Move exit condition into split condition block. |
| EC->moveBefore(CurrentBR); |
| EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV); |
| |
| // Move exiting block's branch into split condition block. Update its branch |
| // destination. |
| BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator()); |
| ExitingBR->moveBefore(CurrentBR); |
| if (ExitingBR->getSuccessor(0) == ExitBB) |
| ExitingBR->setSuccessor(1, ActiveBB); |
| else |
| ExitingBR->setSuccessor(0, ActiveBB); |
| |
| // Remove split condition and current split condition branch. |
| SC->eraseFromParent(); |
| CurrentBR->eraseFromParent(); |
| |
| // Connect exiting block to split condition block. |
| new BranchInst(CondBB, ExitingBB); |
| |
| // Update PHINodes |
| updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd); |
| |
| // Fix dominator info. |
| // ExitBB is now dominated by CondBB |
| DT->changeImmediateDominator(ExitBB, CondBB); |
| DF->changeImmediateDominator(ExitBB, CondBB, DT); |
| |
| // Basicblocks dominated by ActiveBB may have ExitingBB or |
| // a basic block outside the loop in their DF list. If so, |
| // replace it with CondBB. |
| DomTreeNode *Node = DT->getNode(ActiveBB); |
| for (df_iterator<DomTreeNode *> DI = df_begin(Node), DE = df_end(Node); |
| DI != DE; ++DI) { |
| BasicBlock *BB = DI->getBlock(); |
| DominanceFrontier::iterator BBDF = DF->find(BB); |
| DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin(); |
| DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end(); |
| while (DomSetI != DomSetE) { |
| DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI; |
| ++DomSetI; |
| BasicBlock *DFBB = *CurrentItr; |
| if (DFBB == ExitingBB || !L->contains(DFBB)) { |
| BBDF->second.erase(DFBB); |
| BBDF->second.insert(CondBB); |
| } |
| } |
| } |
| } |
| |
| /// updatePHINodes - CFG has been changed. |
| /// Before |
| /// - ExitBB's single predecessor was Latch |
| /// - Latch's second successor was Header |
| /// Now |
| /// - ExitBB's single predecessor was Header |
| /// - Latch's one and only successor was Header |
| /// |
| /// Update ExitBB PHINodes' to reflect this change. |
| void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, |
| BasicBlock *Header, |
| PHINode *IV, Instruction *IVIncrement) { |
| |
| for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end(); |
| BI != BE; ++BI) { |
| PHINode *PN = dyn_cast<PHINode>(BI); |
| if (!PN) |
| break; |
| |
| Value *V = PN->getIncomingValueForBlock(Latch); |
| if (PHINode *PHV = dyn_cast<PHINode>(V)) { |
| // PHV is in Latch. PHV has two uses, one use is in ExitBB PHINode |
| // (i.e. PN :)). |
| // The second use is in Header and it is new incoming value for PN. |
| PHINode *U1 = NULL; |
| PHINode *U2 = NULL; |
| Value *NewV = NULL; |
| for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end(); |
| UI != E; ++UI) { |
| if (!U1) |
| U1 = cast<PHINode>(*UI); |
| else if (!U2) |
| U2 = cast<PHINode>(*UI); |
| else |
| assert ( 0 && "Unexpected third use of this PHINode"); |
| } |
| assert (U1 && U2 && "Unable to find two uses"); |
| |
| if (U1->getParent() == Header) |
| NewV = U1; |
| else |
| NewV = U2; |
| PN->addIncoming(NewV, Header); |
| |
| } else if (Instruction *PHI = dyn_cast<Instruction>(V)) { |
| // If this instruction is IVIncrement then IV is new incoming value |
| // from header otherwise this instruction must be incoming value from |
| // header because loop is in LCSSA form. |
| if (PHI == IVIncrement) |
| PN->addIncoming(IV, Header); |
| else |
| PN->addIncoming(V, Header); |
| } else |
| // Otherwise this is an incoming value from header because loop is in |
| // LCSSA form. |
| PN->addIncoming(V, Header); |
| |
| // Remove incoming value from Latch. |
| PN->removeIncomingValue(Latch); |
| } |
| } |
