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=3859a1aec4a745f62bc9e70a0a03e3791e53ff16;hb=ca3c5b87220b162adb684cecebd18ba5b39997a8;hpb=fdebc38523b397743973ff6a2d2e93b112dd96e5 diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp index 3859a1aec4a..602e8ba5510 100644 --- a/lib/Transforms/Utils/BasicBlockUtils.cpp +++ b/lib/Transforms/Utils/BasicBlockUtils.cpp @@ -13,20 +13,21 @@ //===----------------------------------------------------------------------===// #include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/Constant.h" -#include "llvm/Type.h" #include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Analysis/Dominators.h" +#include "llvm/Analysis/CFG.h" #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/MemoryDependenceAnalysis.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/Transforms/Scalar.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; @@ -37,12 +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(); @@ -55,7 +56,7 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) { I.replaceAllUsesWith(UndefValue::get(I.getType())); BB->getInstList().pop_back(); } - + // Zap the block! BB->eraseFromParent(); } @@ -66,25 +67,25 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) { /// when the block has exactly one predecessor. void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) { if (!isa(BB->begin())) return; - - AliasAnalysis *AA = 0; - MemoryDependenceAnalysis *MemDep = 0; + + 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(); } } @@ -94,7 +95,7 @@ void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) { /// 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. -bool 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; @@ -105,7 +106,7 @@ bool llvm::DeleteDeadPHIs(BasicBlock *BB) { bool Changed = false; for (unsigned i = 0, e = PHIs.size(); i != e; ++i) if (PHINode *PN = dyn_cast_or_null(PHIs[i].operator Value*())) - Changed |= RecursivelyDeleteDeadPHINode(PN); + Changed |= RecursivelyDeleteDeadPHINode(PN, TLI); return Changed; } @@ -115,7 +116,7 @@ bool llvm::DeleteDeadPHIs(BasicBlock *BB) { 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; @@ -124,15 +125,15 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) { 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; 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; @@ -149,43 +150,45 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) { // Begin by getting rid of unneeded PHIs. if (isa(BB->front())) FoldSingleEntryPHINodes(BB, P); - + // Delete the unconditional branch from the predecessor... PredBB->getInstList().pop_back(); - + // 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()) { - if (DomTreeNode *DTN = DT->getNode(BB)) { - DomTreeNode *PredDTN = DT->getNode(PredBB); + 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 (SmallVector::iterator DI = Children.begin(), + 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; } @@ -214,7 +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... @@ -235,27 +238,11 @@ void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); } -/// GetSuccessorNumber - Search for the specified successor of basic block BB -/// and return its position in the terminator instruction's list of -/// successors. It is an error to call this with a block that is not a -/// successor. -unsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) { - TerminatorInst *Term = BB->getTerminator(); -#ifndef NDEBUG - unsigned e = Term->getNumSuccessors(); -#endif - for (unsigned i = 0; ; ++i) { - assert(i != e && "Didn't find edge?"); - if (Term->getSuccessor(i) == Succ) - return i; - } -} - -/// 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) { unsigned SuccNum = GetSuccessorNumber(BB, Succ); - + // If this is a critical edge, let SplitCriticalEdge do it. TerminatorInst *LatchTerm = BB->getTerminator(); if (SplitCriticalEdge(LatchTerm, SuccNum, P)) @@ -263,19 +250,18 @@ BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { // 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); } - + // 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!"); + "Should have a single succ!"); return SplitBlock(BB, BB->getTerminator(), P); } @@ -296,18 +282,20 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { if (Loop *L = LI->getLoopFor(Old)) L->addBasicBlockToLoop(New, LI->getBase()); - if (DominatorTree *DT = P->getAnalysisIfAvailable()) { + 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)) { + 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); } } @@ -322,7 +310,7 @@ static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB, if (!P) return; LoopInfo *LI = P->getAnalysisIfAvailable(); - Loop *L = LI ? LI->getLoopFor(OldBB) : 0; + Loop *L = LI ? LI->getLoopFor(OldBB) : nullptr; // If we need to preserve loop analyses, collect some information about how // this split will affect loops. @@ -352,9 +340,9 @@ static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB, } // Update dominator tree if available. - DominatorTree *DT = P->getAnalysisIfAvailable(); - if (DT) - DT->splitBlock(NewBB); + if (DominatorTreeWrapperPass *DTWP = + P->getAnalysisIfAvailable()) + DTWP->getDomTree().splitBlock(NewBB); if (!L) return; @@ -363,7 +351,7 @@ static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB, // 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 = 0; + Loop *InnermostPredLoop = nullptr; for (ArrayRef::iterator i = Preds.begin(), e = Preds.end(); i != e; ++i) { BasicBlock *Pred = *i; @@ -396,47 +384,68 @@ 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() : 0; + 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 = 0; + Value *InVal = nullptr; if (!HasLoopExit) { InVal = PN->getIncomingValueForBlock(Preds[0]); - for (unsigned i = 1, e = Preds.size(); i != e; ++i) - if (InVal != PN->getIncomingValueForBlock(Preds[i])) { - InVal = 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. - for (unsigned i = 0, e = Preds.size(); i != e; ++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 = + + // 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); - - // Move all of the PHI values for 'Preds' to the new PHI. - for (unsigned i = 0, e = Preds.size(); i != e; ++i) { - Value *V = PN->removeIncomingValue(Preds[i], false); - NewPHI->addIncoming(V, Preds[i]); + 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); } - - InVal = NewPHI; } - // Add an incoming value to the PHI node in the loop for the preheader - // edge. - PN->addIncoming(InVal, NewBB); + PN->addIncoming(NewPHI, NewBB); } } @@ -451,16 +460,16 @@ static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB, /// 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, +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, e = Preds.size(); i != e; ++i) { // This is slightly more strict than necessary; the minimum requirement @@ -497,13 +506,13 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, /// 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, @@ -550,7 +559,7 @@ void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB, e = pred_end(OrigBB); } - BasicBlock *NewBB2 = 0; + BasicBlock *NewBB2 = nullptr; if (!NewBB2Preds.empty()) { // Create another basic block for the rest of OrigBB's predecessors. NewBB2 = BasicBlock::Create(OrigBB->getContext(), @@ -598,52 +607,6 @@ void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB, } } -/// 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. -/// -/// 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); - } - } while (!VisitStack.empty()); -} - /// 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 @@ -655,15 +618,31 @@ ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, // 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) - if (PHINode *PN = dyn_cast(*i)) - if (PN->getParent() == BB) - *i = PN->getIncomingValueForBlock(Pred); - + 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; + } + if (PHINode *PN = dyn_cast(V)) { + if (PN->getParent() == BB) { + if (NewBC) + NewBC->setOperand(0, PN->getIncomingValueForBlock(Pred)); + else + *i = PN->getIncomingValueForBlock(Pred); + } + } + } + // Update any PHI nodes in the returning block to realize that we no // longer branch to them. BB->removePredecessor(Pred); @@ -671,12 +650,197 @@ ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB, return cast(NewRet); } -/// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a -/// given basic block. -DebugLoc llvm::GetFirstDebugLocInBasicBlock(const BasicBlock *BB) { - if (const Instruction *I = BB->getFirstNonPHI()) - return I->getDebugLoc(); - // Scanning entire block may be too expensive, if the first instruction - // does not have valid location info. - return DebugLoc(); +/// 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 +/// +/// 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); + } + } + + 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); +} + + +/// 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. +/// +/// 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; + } + + // 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); + } + + 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(); + } + + // 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(); }