#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 {
/// 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<CriticalEdge, 32> 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<MachineBasicBlock *, 32> 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<bool, 32> 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<MachineBasicBlock>* DT;
~MachineDominatorTree();
- DominatorTreeBase<MachineBasicBlock>& getBase() { return *DT; }
+ DominatorTreeBase<MachineBasicBlock> &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<MachineBasicBlock*> &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*/ ;
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);
}
/// 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);
}
/// block. This is the same as using operator[] on this class.
///
inline MachineDomTreeNode *getNode(MachineBasicBlock *BB) const {
+ applySplitCriticalEdges();
return DT->getNode(BB);
}
/// the children list of the immediate dominator.
inline MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB,
MachineBasicBlock *DomBB) {
+ applySplitCriticalEdges();
return DT->addNewBlock(BB, DomBB);
}
///
inline void changeImmediateDominator(MachineBasicBlock *N,
MachineBasicBlock* NewIDom) {
+ applySplitCriticalEdges();
DT->changeImmediateDominator(N, NewIDom);
}
inline void changeImmediateDominator(MachineDomTreeNode *N,
MachineDomTreeNode* NewIDom) {
+ applySplitCriticalEdges();
DT->changeImmediateDominator(N, NewIDom);
}
/// 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));
+ }
};
//===-------------------------------------
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