X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FCodeGen%2FMachineDominators.h;h=879ae86151092ec8b13e0bfe7cc2cd1ecfd046d2;hb=49128636b627847b223fa3bcc29b85e6deb87c09;hp=9dbe03c3587e3dbee0c2d672851044f2bd7cd81b;hpb=55ba691dce40d2af5a8f01ceacbe3734d90005b3;p=oota-llvm.git diff --git a/include/llvm/CodeGen/MachineDominators.h b/include/llvm/CodeGen/MachineDominators.h index 9dbe03c3587..879ae861510 100644 --- a/include/llvm/CodeGen/MachineDominators.h +++ b/include/llvm/CodeGen/MachineDominators.h @@ -15,11 +15,12 @@ #ifndef LLVM_CODEGEN_MACHINEDOMINATORS_H #define LLVM_CODEGEN_MACHINEDOMINATORS_H -#include "llvm/Analysis/DominatorInternals.h" -#include "llvm/Analysis/Dominators.h" +#include "llvm/ADT/SmallSet.h" #include "llvm/CodeGen/MachineBasicBlock.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/Support/GenericDomTree.h" +#include "llvm/Support/GenericDomTreeConstruction.h" namespace llvm { @@ -38,6 +39,103 @@ typedef DomTreeNodeBase MachineDomTreeNode; /// compute a normal dominator tree. /// class MachineDominatorTree : public MachineFunctionPass { + /// \brief Helper structure used to hold all the basic blocks + /// involved in the split of a critical edge. + struct CriticalEdge { + MachineBasicBlock *FromBB; + MachineBasicBlock *ToBB; + MachineBasicBlock *NewBB; + CriticalEdge(MachineBasicBlock *FromBB, MachineBasicBlock *ToBB, + MachineBasicBlock *NewBB) + : FromBB(FromBB), ToBB(ToBB), NewBB(NewBB) {} + }; + + /// \brief Pile up all the critical edges to be split. + /// The splitting of a critical edge is local and thus, it is possible + /// to apply several of those changes at the same time. + mutable SmallVector CriticalEdgesToSplit; + /// \brief Remember all the basic blocks that are inserted during + /// edge splitting. + /// Invariant: NewBBs == all the basic blocks contained in the NewBB + /// field of all the elements of CriticalEdgesToSplit. + /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs + /// such as BB == elt.NewBB. + mutable SmallSet NewBBs; + + /// \brief Apply all the recorded critical edges to the DT. + /// This updates the underlying DT information in a way that uses + /// the fast query path of DT as much as possible. + /// + /// \post CriticalEdgesToSplit.empty(). + void applySplitCriticalEdges() const { + // Bail out early if there is nothing to do. + if (CriticalEdgesToSplit.empty()) + return; + + // For each element in CriticalEdgesToSplit, remember whether or + // not element is the new immediate domminator of its successor. + // The mapping is done by index, i.e., the information for the ith + // element of CriticalEdgesToSplit is the ith element of IsNewIDom. + SmallVector IsNewIDom; + IsNewIDom.resize(CriticalEdgesToSplit.size()); + size_t Idx = 0; + + // Collect all the dominance properties info, before invalidating + // the underlying DT. + for (CriticalEdge &Edge : CriticalEdgesToSplit) { + // Update dominator information. + MachineBasicBlock *Succ = Edge.ToBB; + MachineDomTreeNode *SucccDTNode = DT->getNode(Succ); + + IsNewIDom[Idx] = true; + for (MachineBasicBlock *PredBB : Succ->predecessors()) { + if (PredBB == Edge.NewBB) + continue; + // If we are in this situation: + // FromBB1 FromBB2 + // + + + // + + + + + // + + + + + // ... Split1 Split2 ... + // + + + // + + + // + + // Succ + // Instead of checking the domiance property with Split2, we + // check it with FromBB2 since Split2 is still unknown of the + // underlying DT structure. + if (NewBBs.count(PredBB)) { + assert(PredBB->pred_size() == 1 && "A basic block resulting from a " + "critical edge split has more " + "than one predecessor!"); + PredBB = *PredBB->pred_begin(); + } + if (!DT->dominates(SucccDTNode, DT->getNode(PredBB))) { + IsNewIDom[Idx] = false; + break; + } + } + ++Idx; + } + + // Now, update DT with the collected dominance properties info. + Idx = 0; + for (CriticalEdge &Edge : CriticalEdgesToSplit) { + // We know FromBB dominates NewBB. + MachineDomTreeNode *NewDTNode = DT->addNewBlock(Edge.NewBB, Edge.FromBB); + MachineDomTreeNode *SucccDTNode = DT->getNode(Edge.ToBB); + + // If all the other predecessors of "Succ" are dominated by "Succ" itself + // then the new block is the new immediate dominator of "Succ". Otherwise, + // the new block doesn't dominate anything. + if (IsNewIDom[Idx]) + DT->changeImmediateDominator(SucccDTNode, NewDTNode); + ++Idx; + } + NewBBs.clear(); + CriticalEdgesToSplit.clear(); + } + public: static char ID; // Pass ID, replacement for typeid DominatorTreeBase* DT; @@ -46,46 +144,55 @@ public: ~MachineDominatorTree(); - DominatorTreeBase& getBase() { return *DT; } + DominatorTreeBase &getBase() { + applySplitCriticalEdges(); + return *DT; + } - virtual void getAnalysisUsage(AnalysisUsage &AU) const; + void getAnalysisUsage(AnalysisUsage &AU) const override; /// getRoots - Return the root blocks of the current CFG. This may include /// multiple blocks if we are computing post dominators. For forward /// dominators, this will always be a single block (the entry node). /// inline const std::vector &getRoots() const { + applySplitCriticalEdges(); return DT->getRoots(); } inline MachineBasicBlock *getRoot() const { + applySplitCriticalEdges(); return DT->getRoot(); } inline MachineDomTreeNode *getRootNode() const { + applySplitCriticalEdges(); return DT->getRootNode(); } - virtual bool runOnMachineFunction(MachineFunction &F); + bool runOnMachineFunction(MachineFunction &F) override; inline bool dominates(const MachineDomTreeNode* A, const MachineDomTreeNode* B) const { + applySplitCriticalEdges(); return DT->dominates(A, B); } inline bool dominates(const MachineBasicBlock* A, const MachineBasicBlock* B) const { + applySplitCriticalEdges(); return DT->dominates(A, B); } // dominates - Return true if A dominates B. This performs the // special checks necessary if A and B are in the same basic block. - bool dominates(MachineInstr *A, MachineInstr *B) const { - MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent(); + bool dominates(const MachineInstr *A, const MachineInstr *B) const { + applySplitCriticalEdges(); + const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent(); if (BBA != BBB) return DT->dominates(BBA, BBB); // Loop through the basic block until we find A or B. - MachineBasicBlock::iterator I = BBA->begin(); + MachineBasicBlock::const_iterator I = BBA->begin(); for (; &*I != A && &*I != B; ++I) /*empty*/ ; @@ -100,11 +207,13 @@ public: inline bool properlyDominates(const MachineDomTreeNode* A, const MachineDomTreeNode* B) const { + applySplitCriticalEdges(); return DT->properlyDominates(A, B); } inline bool properlyDominates(const MachineBasicBlock* A, const MachineBasicBlock* B) const { + applySplitCriticalEdges(); return DT->properlyDominates(A, B); } @@ -112,10 +221,12 @@ public: /// for basic block A and B. If there is no such block then return NULL. inline MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A, MachineBasicBlock *B) { + applySplitCriticalEdges(); return DT->findNearestCommonDominator(A, B); } inline MachineDomTreeNode *operator[](MachineBasicBlock *BB) const { + applySplitCriticalEdges(); return DT->getNode(BB); } @@ -123,6 +234,7 @@ public: /// block. This is the same as using operator[] on this class. /// inline MachineDomTreeNode *getNode(MachineBasicBlock *BB) const { + applySplitCriticalEdges(); return DT->getNode(BB); } @@ -131,6 +243,7 @@ public: /// the children list of the immediate dominator. inline MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB, MachineBasicBlock *DomBB) { + applySplitCriticalEdges(); return DT->addNewBlock(BB, DomBB); } @@ -139,11 +252,13 @@ public: /// inline void changeImmediateDominator(MachineBasicBlock *N, MachineBasicBlock* NewIDom) { + applySplitCriticalEdges(); DT->changeImmediateDominator(N, NewIDom); } inline void changeImmediateDominator(MachineDomTreeNode *N, MachineDomTreeNode* NewIDom) { + applySplitCriticalEdges(); DT->changeImmediateDominator(N, NewIDom); } @@ -151,24 +266,49 @@ public: /// dominate any other blocks. Removes node from its immediate dominator's /// children list. Deletes dominator node associated with basic block BB. inline void eraseNode(MachineBasicBlock *BB) { + applySplitCriticalEdges(); DT->eraseNode(BB); } /// splitBlock - BB is split and now it has one successor. Update dominator /// tree to reflect this change. inline void splitBlock(MachineBasicBlock* NewBB) { + applySplitCriticalEdges(); DT->splitBlock(NewBB); } /// isReachableFromEntry - Return true if A is dominated by the entry /// block of the function containing it. bool isReachableFromEntry(const MachineBasicBlock *A) { + applySplitCriticalEdges(); return DT->isReachableFromEntry(A); } - virtual void releaseMemory(); + void releaseMemory() override; - virtual void print(raw_ostream &OS, const Module*) const; + void print(raw_ostream &OS, const Module*) const override; + + /// \brief Record that the critical edge (FromBB, ToBB) has been + /// split with NewBB. + /// This is best to use this method instead of directly update the + /// underlying information, because this helps mitigating the + /// number of time the DT information is invalidated. + /// + /// \note Do not use this method with regular edges. + /// + /// \note To benefit from the compile time improvement incurred by this + /// method, the users of this method have to limit the queries to the DT + /// interface between two edges splitting. In other words, they have to + /// pack the splitting of critical edges as much as possible. + void recordSplitCriticalEdge(MachineBasicBlock *FromBB, + MachineBasicBlock *ToBB, + MachineBasicBlock *NewBB) { + bool Inserted = NewBBs.insert(NewBB); + (void)Inserted; + assert(Inserted && + "A basic block inserted via edge splitting cannot appear twice"); + CriticalEdgesToSplit.push_back(CriticalEdge(FromBB, ToBB, NewBB)); + } }; //===-------------------------------------