X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FUtils%2FBasicBlockUtils.cpp;h=602e8ba55107a073109533d06c3dca0223d76504;hp=c3d6194801d23426ed4555ae70204d7da301ea14;hb=ca3c5b87220b162adb684cecebd18ba5b39997a8;hpb=58cfa3b13752579c86cf85270d49f9ced0942f2f diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp index c3d6194801d..602e8ba5510 100644 --- a/lib/Transforms/Utils/BasicBlockUtils.cpp +++ b/lib/Transforms/Utils/BasicBlockUtils.cpp @@ -13,19 +13,21 @@ //===----------------------------------------------------------------------===// #include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/LLVMContext.h" -#include "llvm/Constant.h" -#include "llvm/Type.h" #include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CFG.h" #include "llvm/Analysis/LoopInfo.h" -#include "llvm/Analysis/Dominators.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Analysis/MemoryDependenceAnalysis.h" +#include "llvm/IR/Constant.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/Type.h" +#include "llvm/IR/ValueHandle.h" #include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/ValueHandle.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/Local.h" #include using namespace llvm; @@ -36,12 +38,12 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) { // Can delete self loop. BB->getSinglePredecessor() == BB) && "Block is not dead!"); TerminatorInst *BBTerm = BB->getTerminator(); - + // Loop through all of our successors and make sure they know that one // of their predecessors is going away. for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) BBTerm->getSuccessor(i)->removePredecessor(BB); - + // Zap all the instructions in the block. while (!BB->empty()) { Instruction &I = BB->back(); @@ -54,7 +56,7 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) { I.replaceAllUsesWith(UndefValue::get(I.getType())); BB->getInstList().pop_back(); } - + // Zap the block! BB->eraseFromParent(); } @@ -63,15 +65,27 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) { /// any single-entry PHI nodes in it, fold them away. This handles the case /// when all entries to the PHI nodes in a block are guaranteed equal, such as /// when the block has exactly one predecessor. -void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) { - if (!isa(BB->begin())) - return; - +void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) { + if (!isa(BB->begin())) return; + + AliasAnalysis *AA = nullptr; + MemoryDependenceAnalysis *MemDep = nullptr; + if (P) { + AA = P->getAnalysisIfAvailable(); + MemDep = P->getAnalysisIfAvailable(); + } + while (PHINode *PN = dyn_cast(BB->begin())) { if (PN->getIncomingValue(0) != PN) PN->replaceAllUsesWith(PN->getIncomingValue(0)); else PN->replaceAllUsesWith(UndefValue::get(PN->getType())); + + if (MemDep) + MemDep->removeInstruction(PN); // Memdep updates AA itself. + else if (AA && isa(PN->getType())) + AA->deleteValue(PN); + PN->eraseFromParent(); } } @@ -81,7 +95,7 @@ void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) { /// is dead. Also recursively delete any operands that become dead as /// a result. This includes tracing the def-use list from the PHI to see if /// it is ultimately unused or if it reaches an unused cycle. -void llvm::DeleteDeadPHIs(BasicBlock *BB) { +bool llvm::DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI) { // Recursively deleting a PHI may cause multiple PHIs to be deleted // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete. SmallVector PHIs; @@ -89,40 +103,37 @@ void llvm::DeleteDeadPHIs(BasicBlock *BB) { PHINode *PN = dyn_cast(I); ++I) PHIs.push_back(PN); + bool Changed = false; for (unsigned i = 0, e = PHIs.size(); i != e; ++i) if (PHINode *PN = dyn_cast_or_null(PHIs[i].operator Value*())) - RecursivelyDeleteDeadPHINode(PN); + Changed |= RecursivelyDeleteDeadPHINode(PN, TLI); + + return Changed; } /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, /// if possible. The return value indicates success or failure. -bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) { - pred_iterator PI(pred_begin(BB)), PE(pred_end(BB)); - // Can't merge the entry block. - if (pred_begin(BB) == pred_end(BB)) return false; - - BasicBlock *PredBB = *PI++; - for (; PI != PE; ++PI) // Search all predecessors, see if they are all same - if (*PI != PredBB) { - PredBB = 0; // There are multiple different predecessors... - break; - } - - // Can't merge if there are multiple predecessors. +bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) { + // Don't merge away blocks who have their address taken. + if (BB->hasAddressTaken()) return false; + + // Can't merge if there are multiple predecessors, or no predecessors. + BasicBlock *PredBB = BB->getUniquePredecessor(); if (!PredBB) return false; + // Don't break self-loops. if (PredBB == BB) return false; // Don't break invokes. if (isa(PredBB->getTerminator())) return false; - + succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB)); - BasicBlock* OnlySucc = BB; + BasicBlock *OnlySucc = BB; for (; SI != SE; ++SI) if (*SI != OnlySucc) { - OnlySucc = 0; // There are multiple distinct successors! + OnlySucc = nullptr; // There are multiple distinct successors! break; } - + // Can't merge if there are multiple successors. if (!OnlySucc) return false; @@ -137,45 +148,48 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) { } // Begin by getting rid of unneeded PHIs. - while (PHINode *PN = dyn_cast(&BB->front())) { - PN->replaceAllUsesWith(PN->getIncomingValue(0)); - BB->getInstList().pop_front(); // Delete the phi node... - } - + if (isa(BB->front())) + FoldSingleEntryPHINodes(BB, P); + // Delete the unconditional branch from the predecessor... PredBB->getInstList().pop_back(); - - // Move all definitions in the successor to the predecessor... - PredBB->getInstList().splice(PredBB->end(), BB->getInstList()); - + // Make all PHI nodes that referred to BB now refer to Pred as their // source... BB->replaceAllUsesWith(PredBB); - + + // Move all definitions in the successor to the predecessor... + PredBB->getInstList().splice(PredBB->end(), BB->getInstList()); + // Inherit predecessors name if it exists. if (!PredBB->hasName()) PredBB->takeName(BB); - + // Finally, erase the old block and update dominator info. if (P) { - if (DominatorTree* DT = P->getAnalysisIfAvailable()) { - DomTreeNode* DTN = DT->getNode(BB); - DomTreeNode* PredDTN = DT->getNode(PredBB); - - if (DTN) { - SmallPtrSet Children(DTN->begin(), DTN->end()); - for (SmallPtrSet::iterator DI = Children.begin(), + if (DominatorTreeWrapperPass *DTWP = + P->getAnalysisIfAvailable()) { + DominatorTree &DT = DTWP->getDomTree(); + if (DomTreeNode *DTN = DT.getNode(BB)) { + DomTreeNode *PredDTN = DT.getNode(PredBB); + SmallVector Children(DTN->begin(), DTN->end()); + for (SmallVectorImpl::iterator DI = Children.begin(), DE = Children.end(); DI != DE; ++DI) - DT->changeImmediateDominator(*DI, PredDTN); + DT.changeImmediateDominator(*DI, PredDTN); - DT->eraseNode(BB); + DT.eraseNode(BB); } + + if (LoopInfo *LI = P->getAnalysisIfAvailable()) + LI->removeBlock(BB); + + if (MemoryDependenceAnalysis *MD = + P->getAnalysisIfAvailable()) + MD->invalidateCachedPredecessors(); } } - + BB->eraseFromParent(); - - return true; } @@ -203,7 +217,7 @@ void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL, /// void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL, BasicBlock::iterator &BI, Instruction *I) { - assert(I->getParent() == 0 && + assert(I->getParent() == nullptr && "ReplaceInstWithInst: Instruction already inserted into basic block!"); // Insert the new instruction into the basic block... @@ -224,88 +238,31 @@ void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); } -/// RemoveSuccessor - Change the specified terminator instruction such that its -/// successor SuccNum no longer exists. Because this reduces the outgoing -/// degree of the current basic block, the actual terminator instruction itself -/// may have to be changed. In the case where the last successor of the block -/// is deleted, a return instruction is inserted in its place which can cause a -/// surprising change in program behavior if it is not expected. -/// -void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) { - assert(SuccNum < TI->getNumSuccessors() && - "Trying to remove a nonexistant successor!"); - - // If our old successor block contains any PHI nodes, remove the entry in the - // PHI nodes that comes from this branch... - // - BasicBlock *BB = TI->getParent(); - TI->getSuccessor(SuccNum)->removePredecessor(BB); - - TerminatorInst *NewTI = 0; - switch (TI->getOpcode()) { - case Instruction::Br: - // If this is a conditional branch... convert to unconditional branch. - if (TI->getNumSuccessors() == 2) { - cast(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum)); - } else { // Otherwise convert to a return instruction... - Value *RetVal = 0; - - // Create a value to return... if the function doesn't return null... - if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext())) - RetVal = Constant::getNullValue(BB->getParent()->getReturnType()); - - // Create the return... - NewTI = ReturnInst::Create(TI->getContext(), RetVal); - } - break; - - case Instruction::Invoke: // Should convert to call - case Instruction::Switch: // Should remove entry - default: - case Instruction::Ret: // Cannot happen, has no successors! - llvm_unreachable("Unhandled terminator instruction type in RemoveSuccessor!"); - } - - if (NewTI) // If it's a different instruction, replace. - ReplaceInstWithInst(TI, NewTI); -} - -/// SplitEdge - Split the edge connecting specified block. Pass P must -/// not be NULL. +/// SplitEdge - Split the edge connecting specified block. Pass P must +/// not be NULL. BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { - TerminatorInst *LatchTerm = BB->getTerminator(); - unsigned SuccNum = 0; -#ifndef NDEBUG - unsigned e = LatchTerm->getNumSuccessors(); -#endif - for (unsigned i = 0; ; ++i) { - assert(i != e && "Didn't find edge?"); - if (LatchTerm->getSuccessor(i) == Succ) { - SuccNum = i; - break; - } - } - + unsigned SuccNum = GetSuccessorNumber(BB, Succ); + // If this is a critical edge, let SplitCriticalEdge do it. - if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P)) + TerminatorInst *LatchTerm = BB->getTerminator(); + if (SplitCriticalEdge(LatchTerm, SuccNum, P)) return LatchTerm->getSuccessor(SuccNum); // If the edge isn't critical, then BB has a single successor or Succ has a // single pred. Split the block. - BasicBlock::iterator SplitPoint; if (BasicBlock *SP = Succ->getSinglePredecessor()) { // If the successor only has a single pred, split the top of the successor // block. assert(SP == BB && "CFG broken"); - SP = NULL; + SP = nullptr; return SplitBlock(Succ, Succ->begin(), P); - } else { - // Otherwise, if BB has a single successor, split it at the bottom of the - // block. - assert(BB->getTerminator()->getNumSuccessors() == 1 && - "Should have a single succ!"); - return SplitBlock(BB, BB->getTerminator(), P); } + + // Otherwise, if BB has a single successor, split it at the bottom of the + // block. + assert(BB->getTerminator()->getNumSuccessors() == 1 && + "Should have a single succ!"); + return SplitBlock(BB, BB->getTerminator(), P); } /// SplitBlock - Split the specified block at the specified instruction - every @@ -315,37 +272,182 @@ BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { /// BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { BasicBlock::iterator SplitIt = SplitPt; - while (isa(SplitIt)) + while (isa(SplitIt) || isa(SplitIt)) ++SplitIt; BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); - // The new block lives in whichever loop the old one did. - if (LoopInfo* LI = P->getAnalysisIfAvailable()) + // The new block lives in whichever loop the old one did. This preserves + // LCSSA as well, because we force the split point to be after any PHI nodes. + if (LoopInfo *LI = P->getAnalysisIfAvailable()) if (Loop *L = LI->getLoopFor(Old)) L->addBasicBlockToLoop(New, LI->getBase()); - if (DominatorTree *DT = P->getAnalysisIfAvailable()) - { - // Old dominates New. New node domiantes all other nodes dominated by Old. - DomTreeNode *OldNode = DT->getNode(Old); + if (DominatorTreeWrapperPass *DTWP = + P->getAnalysisIfAvailable()) { + DominatorTree &DT = DTWP->getDomTree(); + // Old dominates New. New node dominates all other nodes dominated by Old. + if (DomTreeNode *OldNode = DT.getNode(Old)) { std::vector Children; for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); - I != E; ++I) + I != E; ++I) Children.push_back(*I); - DomTreeNode *NewNode = DT->addNewBlock(New,Old); - + DomTreeNode *NewNode = DT.addNewBlock(New, Old); for (std::vector::iterator I = Children.begin(), - E = Children.end(); I != E; ++I) - DT->changeImmediateDominator(*I, NewNode); + E = Children.end(); I != E; ++I) + DT.changeImmediateDominator(*I, NewNode); } + } - if (DominanceFrontier *DF = P->getAnalysisIfAvailable()) - DF->splitBlock(Old); - return New; } +/// UpdateAnalysisInformation - Update DominatorTree, LoopInfo, and LCCSA +/// analysis information. +static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB, + ArrayRef Preds, + Pass *P, bool &HasLoopExit) { + if (!P) return; + + LoopInfo *LI = P->getAnalysisIfAvailable(); + Loop *L = LI ? LI->getLoopFor(OldBB) : nullptr; + + // If we need to preserve loop analyses, collect some information about how + // this split will affect loops. + bool IsLoopEntry = !!L; + bool SplitMakesNewLoopHeader = false; + if (LI) { + bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID); + for (ArrayRef::iterator + i = Preds.begin(), e = Preds.end(); i != e; ++i) { + BasicBlock *Pred = *i; + + // If we need to preserve LCSSA, determine if any of the preds is a loop + // exit. + if (PreserveLCSSA) + if (Loop *PL = LI->getLoopFor(Pred)) + if (!PL->contains(OldBB)) + HasLoopExit = true; + + // If we need to preserve LoopInfo, note whether any of the preds crosses + // an interesting loop boundary. + if (!L) continue; + if (L->contains(Pred)) + IsLoopEntry = false; + else + SplitMakesNewLoopHeader = true; + } + } + + // Update dominator tree if available. + if (DominatorTreeWrapperPass *DTWP = + P->getAnalysisIfAvailable()) + DTWP->getDomTree().splitBlock(NewBB); + + if (!L) return; + + if (IsLoopEntry) { + // Add the new block to the nearest enclosing loop (and not an adjacent + // loop). To find this, examine each of the predecessors and determine which + // loops enclose them, and select the most-nested loop which contains the + // loop containing the block being split. + Loop *InnermostPredLoop = nullptr; + for (ArrayRef::iterator + i = Preds.begin(), e = Preds.end(); i != e; ++i) { + BasicBlock *Pred = *i; + if (Loop *PredLoop = LI->getLoopFor(Pred)) { + // Seek a loop which actually contains the block being split (to avoid + // adjacent loops). + while (PredLoop && !PredLoop->contains(OldBB)) + PredLoop = PredLoop->getParentLoop(); + + // Select the most-nested of these loops which contains the block. + if (PredLoop && PredLoop->contains(OldBB) && + (!InnermostPredLoop || + InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth())) + InnermostPredLoop = PredLoop; + } + } + + if (InnermostPredLoop) + InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase()); + } else { + L->addBasicBlockToLoop(NewBB, LI->getBase()); + if (SplitMakesNewLoopHeader) + L->moveToHeader(NewBB); + } +} + +/// UpdatePHINodes - Update the PHI nodes in OrigBB to include the values coming +/// from NewBB. This also updates AliasAnalysis, if available. +static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB, + ArrayRef Preds, BranchInst *BI, + Pass *P, bool HasLoopExit) { + // Otherwise, create a new PHI node in NewBB for each PHI node in OrigBB. + AliasAnalysis *AA = P ? P->getAnalysisIfAvailable() : nullptr; + SmallPtrSet PredSet(Preds.begin(), Preds.end()); + for (BasicBlock::iterator I = OrigBB->begin(); isa(I); ) { + PHINode *PN = cast(I++); + + // Check to see if all of the values coming in are the same. If so, we + // don't need to create a new PHI node, unless it's needed for LCSSA. + Value *InVal = nullptr; + if (!HasLoopExit) { + InVal = PN->getIncomingValueForBlock(Preds[0]); + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + if (!PredSet.count(PN->getIncomingBlock(i))) + continue; + if (!InVal) + InVal = PN->getIncomingValue(i); + else if (InVal != PN->getIncomingValue(i)) { + InVal = nullptr; + break; + } + } + } + + if (InVal) { + // If all incoming values for the new PHI would be the same, just don't + // make a new PHI. Instead, just remove the incoming values from the old + // PHI. + + // NOTE! This loop walks backwards for a reason! First off, this minimizes + // the cost of removal if we end up removing a large number of values, and + // second off, this ensures that the indices for the incoming values + // aren't invalidated when we remove one. + for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i) + if (PredSet.count(PN->getIncomingBlock(i))) + PN->removeIncomingValue(i, false); + + // Add an incoming value to the PHI node in the loop for the preheader + // edge. + PN->addIncoming(InVal, NewBB); + continue; + } + + // If the values coming into the block are not the same, we need a new + // PHI. + // Create the new PHI node, insert it into NewBB at the end of the block + PHINode *NewPHI = + PHINode::Create(PN->getType(), Preds.size(), PN->getName() + ".ph", BI); + if (AA) + AA->copyValue(PN, NewPHI); + + // NOTE! This loop walks backwards for a reason! First off, this minimizes + // the cost of removal if we end up removing a large number of values, and + // second off, this ensures that the indices for the incoming values aren't + // invalidated when we remove one. + for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i) { + BasicBlock *IncomingBB = PN->getIncomingBlock(i); + if (PredSet.count(IncomingBB)) { + Value *V = PN->removeIncomingValue(i, false); + NewPHI->addIncoming(V, IncomingBB); + } + } + + PN->addIncoming(NewPHI, NewBB); + } +} /// SplitBlockPredecessors - This method transforms BB by introducing a new /// basic block into the function, and moving some of the predecessors of BB to @@ -353,275 +455,392 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { /// Preds array, which has NumPreds elements in it. The new block is given a /// suffix of 'Suffix'. /// -/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and -/// DominanceFrontier, but no other analyses. -BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, - BasicBlock *const *Preds, - unsigned NumPreds, const char *Suffix, - Pass *P) { +/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, +/// 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). +/// +BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, + ArrayRef Preds, + const char *Suffix, Pass *P) { // Create new basic block, insert right before the original block. BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix, BB->getParent(), BB); - + // The new block unconditionally branches to the old block. BranchInst *BI = BranchInst::Create(BB, NewBB); - + // Move the edges from Preds to point to NewBB instead of BB. - for (unsigned i = 0; i != NumPreds; ++i) + 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(Preds[i]->getTerminator()) && + "Cannot split an edge from an IndirectBrInst"); Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB); - - // Update dominator tree and dominator frontier if available. - DominatorTree *DT = P ? P->getAnalysisIfAvailable() : 0; - if (DT) - DT->splitBlock(NewBB); - if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable():0) - DF->splitBlock(NewBB); - AliasAnalysis *AA = P ? P->getAnalysisIfAvailable() : 0; - - + } + // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI // node becomes an incoming value for BB's phi node. However, if the Preds // list is empty, we need to insert dummy entries into the PHI nodes in BB to // account for the newly created predecessor. - if (NumPreds == 0) { + if (Preds.size() == 0) { // Insert dummy values as the incoming value. for (BasicBlock::iterator I = BB->begin(); isa(I); ++I) cast(I)->addIncoming(UndefValue::get(I->getType()), NewBB); return NewBB; } - - // Otherwise, create a new PHI node in NewBB for each PHI node in BB. - for (BasicBlock::iterator I = BB->begin(); isa(I); ) { - PHINode *PN = cast(I++); - - // Check to see if all of the values coming in are the same. If so, we - // don't need to create a new PHI node. - Value *InVal = PN->getIncomingValueForBlock(Preds[0]); - for (unsigned i = 1; i != NumPreds; ++i) - if (InVal != PN->getIncomingValueForBlock(Preds[i])) { - InVal = 0; - break; - } - - if (InVal) { - // If all incoming values for the new PHI would be the same, just don't - // make a new PHI. Instead, just remove the incoming values from the old - // PHI. - for (unsigned i = 0; i != NumPreds; ++i) - PN->removeIncomingValue(Preds[i], false); - } else { - // If the values coming into the block are not the same, we need a PHI. - // Create the new PHI node, insert it into NewBB at the end of the block - PHINode *NewPHI = - PHINode::Create(PN->getType(), PN->getName()+".ph", BI); - if (AA) AA->copyValue(PN, NewPHI); - - // Move all of the PHI values for 'Preds' to the new PHI. - for (unsigned i = 0; i != NumPreds; ++i) { - Value *V = PN->removeIncomingValue(Preds[i], false); - NewPHI->addIncoming(V, Preds[i]); - } - InVal = NewPHI; + + // Update DominatorTree, LoopInfo, and LCCSA analysis information. + bool HasLoopExit = false; + UpdateAnalysisInformation(BB, NewBB, Preds, P, HasLoopExit); + + // Update the PHI nodes in BB with the values coming from NewBB. + UpdatePHINodes(BB, NewBB, Preds, BI, P, 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 Preds, + const char *Suffix1, const char *Suffix2, + Pass *P, + SmallVectorImpl &NewBBs) { + 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); + + // 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(Preds[i]->getTerminator()) && + "Cannot split an edge from an IndirectBrInst"); + Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1); + } + + // Update DominatorTree, LoopInfo, and LCCSA analysis information. + bool HasLoopExit = false; + UpdateAnalysisInformation(OrigBB, NewBB1, Preds, P, HasLoopExit); + + // Update the PHI nodes in OrigBB with the values coming from NewBB1. + UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, P, HasLoopExit); + + // Move the remaining edges from OrigBB to point to NewBB2. + SmallVector NewBB2Preds; + for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB); + i != e; ) { + BasicBlock *Pred = *i++; + if (Pred == NewBB1) continue; + assert(!isa(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); + + // Move the remaining edges from OrigBB to point to NewBB2. + for (SmallVectorImpl::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, P, HasLoopExit); + + // Update the PHI nodes in OrigBB with the values coming from NewBB2. + UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, P, 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. + 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(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, NewBC); + *i = NewBC; } - - // Add an incoming value to the PHI node in the loop for the preheader - // edge. - PN->addIncoming(InVal, NewBB); - - // Check to see if we can eliminate this phi node. - if (Value *V = PN->hasConstantValue(DT != 0)) { - Instruction *I = dyn_cast(V); - if (!I || DT == 0 || DT->dominates(I, PN)) { - PN->replaceAllUsesWith(V); - if (AA) AA->deleteValue(PN); - PN->eraseFromParent(); + if (PHINode *PN = dyn_cast(V)) { + if (PN->getParent() == BB) { + if (NewBC) + NewBC->setOperand(0, PN->getIncomingValueForBlock(Pred)); + else + *i = PN->getIncomingValueForBlock(Pred); } } } - - return NewBB; + + // Update any PHI nodes in the returning block to realize that we no + // longer branch to them. + BB->removePredecessor(Pred); + UncondBranch->eraseFromParent(); + return cast(NewRet); } -/// FindFunctionBackedges - Analyze the specified function to find all of the -/// loop backedges in the function and return them. This is a relatively cheap -/// (compared to computing dominators and loop info) analysis. +/// SplitBlockAndInsertIfThen - Split the containing block at the +/// specified instruction - everything before and including SplitBefore stays +/// in the old basic block, and everything after SplitBefore is moved to a +/// new block. The two blocks are connected by a conditional branch +/// (with value of Cmp being the condition). +/// Before: +/// Head +/// SplitBefore +/// Tail +/// After: +/// Head +/// if (Cond) +/// ThenBlock +/// SplitBefore +/// Tail /// -/// The output is added to Result, as pairs of edge info. -void llvm::FindFunctionBackedges(const Function &F, - SmallVectorImpl > &Result) { - const BasicBlock *BB = &F.getEntryBlock(); - if (succ_begin(BB) == succ_end(BB)) - return; - - SmallPtrSet Visited; - SmallVector, 8> VisitStack; - SmallPtrSet InStack; - - Visited.insert(BB); - VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); - InStack.insert(BB); - do { - std::pair &Top = VisitStack.back(); - const BasicBlock *ParentBB = Top.first; - succ_const_iterator &I = Top.second; - - bool FoundNew = false; - while (I != succ_end(ParentBB)) { - BB = *I++; - if (Visited.insert(BB)) { - FoundNew = true; - break; - } - // Successor is in VisitStack, it's a back edge. - if (InStack.count(BB)) - Result.push_back(std::make_pair(ParentBB, BB)); - } - - if (FoundNew) { - // Go down one level if there is a unvisited successor. - InStack.insert(BB); - VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); - } else { - // Go up one level. - InStack.erase(VisitStack.pop_back_val().first); +/// If Unreachable is true, then ThenBlock ends with +/// UnreachableInst, otherwise it branches to Tail. +/// Returns the NewBasicBlock's terminator. + +TerminatorInst *llvm::SplitBlockAndInsertIfThen(Value *Cond, + Instruction *SplitBefore, + bool Unreachable, + MDNode *BranchWeights, + DominatorTree *DT) { + BasicBlock *Head = SplitBefore->getParent(); + BasicBlock *Tail = Head->splitBasicBlock(SplitBefore); + TerminatorInst *HeadOldTerm = Head->getTerminator(); + LLVMContext &C = Head->getContext(); + BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail); + TerminatorInst *CheckTerm; + if (Unreachable) + CheckTerm = new UnreachableInst(C, ThenBlock); + else + CheckTerm = BranchInst::Create(Tail, ThenBlock); + CheckTerm->setDebugLoc(SplitBefore->getDebugLoc()); + BranchInst *HeadNewTerm = + BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cond); + HeadNewTerm->setDebugLoc(SplitBefore->getDebugLoc()); + HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights); + ReplaceInstWithInst(HeadOldTerm, HeadNewTerm); + + if (DT) { + if (DomTreeNode *OldNode = DT->getNode(Head)) { + std::vector Children(OldNode->begin(), OldNode->end()); + + DomTreeNode *NewNode = DT->addNewBlock(Tail, Head); + for (auto Child : Children) + DT->changeImmediateDominator(Child, NewNode); + + // Head dominates ThenBlock. + DT->addNewBlock(ThenBlock, Head); } - } while (!VisitStack.empty()); - - + } + + return CheckTerm; } +/// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen, +/// but also creates the ElseBlock. +/// Before: +/// Head +/// SplitBefore +/// Tail +/// After: +/// Head +/// if (Cond) +/// ThenBlock +/// else +/// ElseBlock +/// SplitBefore +/// Tail +void llvm::SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore, + TerminatorInst **ThenTerm, + TerminatorInst **ElseTerm, + MDNode *BranchWeights) { + BasicBlock *Head = SplitBefore->getParent(); + BasicBlock *Tail = Head->splitBasicBlock(SplitBefore); + TerminatorInst *HeadOldTerm = Head->getTerminator(); + LLVMContext &C = Head->getContext(); + BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail); + BasicBlock *ElseBlock = BasicBlock::Create(C, "", Head->getParent(), Tail); + *ThenTerm = BranchInst::Create(Tail, ThenBlock); + (*ThenTerm)->setDebugLoc(SplitBefore->getDebugLoc()); + *ElseTerm = BranchInst::Create(Tail, ElseBlock); + (*ElseTerm)->setDebugLoc(SplitBefore->getDebugLoc()); + BranchInst *HeadNewTerm = + BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/ElseBlock, Cond); + HeadNewTerm->setDebugLoc(SplitBefore->getDebugLoc()); + HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights); + ReplaceInstWithInst(HeadOldTerm, HeadNewTerm); +} -/// AreEquivalentAddressValues - Test if A and B will obviously have the same -/// value. This includes recognizing that %t0 and %t1 will have the same -/// value in code like this: -/// %t0 = getelementptr \@a, 0, 3 -/// store i32 0, i32* %t0 -/// %t1 = getelementptr \@a, 0, 3 -/// %t2 = load i32* %t1 +/// GetIfCondition - Given a basic block (BB) with two predecessors, +/// check to see if the merge at this block is due +/// to an "if condition". If so, return the boolean condition that determines +/// which entry into BB will be taken. Also, return by references the block +/// that will be entered from if the condition is true, and the block that will +/// be entered if the condition is false. /// -static bool AreEquivalentAddressValues(const Value *A, const Value *B) { - // Test if the values are trivially equivalent. - if (A == B) return true; - - // Test if the values come from identical arithmetic instructions. - // Use isIdenticalToWhenDefined instead of isIdenticalTo because - // this function is only used when one address use dominates the - // other, which means that they'll always either have the same - // value or one of them will have an undefined value. - if (isa(A) || isa(A) || - isa(A) || isa(A)) - if (const Instruction *BI = dyn_cast(B)) - if (cast(A)->isIdenticalToWhenDefined(BI)) - return true; - - // Otherwise they may not be equivalent. - return false; -} +/// This does no checking to see if the true/false blocks have large or unsavory +/// instructions in them. +Value *llvm::GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, + BasicBlock *&IfFalse) { + PHINode *SomePHI = dyn_cast(BB->begin()); + BasicBlock *Pred1 = nullptr; + BasicBlock *Pred2 = nullptr; + + if (SomePHI) { + if (SomePHI->getNumIncomingValues() != 2) + return nullptr; + Pred1 = SomePHI->getIncomingBlock(0); + Pred2 = SomePHI->getIncomingBlock(1); + } else { + pred_iterator PI = pred_begin(BB), PE = pred_end(BB); + if (PI == PE) // No predecessor + return nullptr; + Pred1 = *PI++; + if (PI == PE) // Only one predecessor + return nullptr; + Pred2 = *PI++; + if (PI != PE) // More than two predecessors + return nullptr; + } -/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the -/// instruction before ScanFrom) checking to see if we have the value at the -/// memory address *Ptr locally available within a small number of instructions. -/// If the value is available, return it. -/// -/// If not, return the iterator for the last validated instruction that the -/// value would be live through. If we scanned the entire block and didn't find -/// something that invalidates *Ptr or provides it, ScanFrom would be left at -/// begin() and this returns null. ScanFrom could also be left -/// -/// MaxInstsToScan specifies the maximum instructions to scan in the block. If -/// it is set to 0, it will scan the whole block. You can also optionally -/// specify an alias analysis implementation, which makes this more precise. -Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, - BasicBlock::iterator &ScanFrom, - unsigned MaxInstsToScan, - AliasAnalysis *AA) { - if (MaxInstsToScan == 0) MaxInstsToScan = ~0U; - - // If we're using alias analysis to disambiguate get the size of *Ptr. - unsigned AccessSize = 0; - if (AA) { - const Type *AccessTy = cast(Ptr->getType())->getElementType(); - AccessSize = AA->getTypeStoreSize(AccessTy); + // We can only handle branches. Other control flow will be lowered to + // branches if possible anyway. + BranchInst *Pred1Br = dyn_cast(Pred1->getTerminator()); + BranchInst *Pred2Br = dyn_cast(Pred2->getTerminator()); + if (!Pred1Br || !Pred2Br) + return nullptr; + + // Eliminate code duplication by ensuring that Pred1Br is conditional if + // either are. + if (Pred2Br->isConditional()) { + // If both branches are conditional, we don't have an "if statement". In + // reality, we could transform this case, but since the condition will be + // required anyway, we stand no chance of eliminating it, so the xform is + // probably not profitable. + if (Pred1Br->isConditional()) + return nullptr; + + std::swap(Pred1, Pred2); + std::swap(Pred1Br, Pred2Br); } - - while (ScanFrom != ScanBB->begin()) { - // We must ignore debug info directives when counting (otherwise they - // would affect codegen). - Instruction *Inst = --ScanFrom; - if (isa(Inst)) - continue; - // We skip pointer-to-pointer bitcasts, which are NOPs. - // It is necessary for correctness to skip those that feed into a - // llvm.dbg.declare, as these are not present when debugging is off. - if (isa(Inst) && isa(Inst->getType())) - continue; - // Restore ScanFrom to expected value in case next test succeeds - ScanFrom++; - - // Don't scan huge blocks. - if (MaxInstsToScan-- == 0) return 0; - - --ScanFrom; - // If this is a load of Ptr, the loaded value is available. - if (LoadInst *LI = dyn_cast(Inst)) - if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) - return LI; - - if (StoreInst *SI = dyn_cast(Inst)) { - // If this is a store through Ptr, the value is available! - if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) - return SI->getOperand(0); - - // If Ptr is an alloca and this is a store to a different alloca, ignore - // the store. This is a trivial form of alias analysis that is important - // for reg2mem'd code. - if ((isa(Ptr) || isa(Ptr)) && - (isa(SI->getOperand(1)) || - isa(SI->getOperand(1)))) - continue; - - // If we have alias analysis and it says the store won't modify the loaded - // value, ignore the store. - if (AA && - (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0) - continue; - - // Otherwise the store that may or may not alias the pointer, bail out. - ++ScanFrom; - return 0; - } - - // If this is some other instruction that may clobber Ptr, bail out. - if (Inst->mayWriteToMemory()) { - // If alias analysis claims that it really won't modify the load, - // ignore it. - if (AA && - (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0) - continue; - - // May modify the pointer, bail out. - ++ScanFrom; - return 0; + if (Pred1Br->isConditional()) { + // The only thing we have to watch out for here is to make sure that Pred2 + // doesn't have incoming edges from other blocks. If it does, the condition + // doesn't dominate BB. + if (!Pred2->getSinglePredecessor()) + return nullptr; + + // If we found a conditional branch predecessor, make sure that it branches + // to BB and Pred2Br. If it doesn't, this isn't an "if statement". + if (Pred1Br->getSuccessor(0) == BB && + Pred1Br->getSuccessor(1) == Pred2) { + IfTrue = Pred1; + IfFalse = Pred2; + } else if (Pred1Br->getSuccessor(0) == Pred2 && + Pred1Br->getSuccessor(1) == BB) { + IfTrue = Pred2; + IfFalse = Pred1; + } else { + // We know that one arm of the conditional goes to BB, so the other must + // go somewhere unrelated, and this must not be an "if statement". + return nullptr; } + + return Pred1Br->getCondition(); } - - // Got to the start of the block, we didn't find it, but are done for this - // block. - return 0; -} -/// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint, -/// make a copy of the stoppoint before InsertPos (presumably before copying -/// or moving I). -void llvm::CopyPrecedingStopPoint(Instruction *I, - BasicBlock::iterator InsertPos) { - if (I != I->getParent()->begin()) { - BasicBlock::iterator BBI = I; --BBI; - if (DbgStopPointInst *DSPI = dyn_cast(BBI)) { - CallInst *newDSPI = DSPI->clone(I->getContext()); - newDSPI->insertBefore(InsertPos); - } + // Ok, if we got here, both predecessors end with an unconditional branch to + // BB. Don't panic! If both blocks only have a single (identical) + // predecessor, and THAT is a conditional branch, then we're all ok! + BasicBlock *CommonPred = Pred1->getSinglePredecessor(); + if (CommonPred == nullptr || CommonPred != Pred2->getSinglePredecessor()) + return nullptr; + + // Otherwise, if this is a conditional branch, then we can use it! + BranchInst *BI = dyn_cast(CommonPred->getTerminator()); + if (!BI) return nullptr; + + assert(BI->isConditional() && "Two successors but not conditional?"); + if (BI->getSuccessor(0) == Pred1) { + IfTrue = Pred1; + IfFalse = Pred2; + } else { + IfTrue = Pred2; + IfFalse = Pred1; } + return BI->getCondition(); }