Move code to update dominator information after basic block is split

from LoopSimplify.cpp to Dominator.cpp


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37689 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/Dominators.h

@@ -302,6 +302,11 @@ public:
   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
     AU.setPreservesAll();
   }
+
+  /// splitBlock
+  /// BB is split and now it has one successor. Update dominator tree to
+  /// reflect this change.
+  void splitBlock(BasicBlock *BB);
 private:
   void calculate(Function& F);
   DomTreeNode *getNodeForBlock(BasicBlock *BB);
@@ -587,6 +592,11 @@ public:
     AU.addRequired<DominatorTree>();
   }
 
+  /// splitBlock
+  /// BB is split and now it has one successor. Update dominace frontier to
+  /// reflect this change.
+  void splitBlock(BasicBlock *BB);
+
 private:
   const DomSetType &calculate(const DominatorTree &DT,
                               const DomTreeNode *Node);

lib/Transforms/Utils/CodeExtractor.cpp

@@ -140,19 +140,8 @@ void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) {
 
   // Okay, update dominator sets. The blocks that dominate the new one are the
   // blocks that dominate TIBB plus the new block itself.
-  if (DT) {
+  if (DT)
-    DomTreeNode *OPNode = DT->getNode(OldPred);
+    DT->splitBlock(NewBB);
-    DomTreeNode *IDomNode = OPNode->getIDom();
-    BasicBlock* idom = IDomNode->getBlock();
-    DT->addNewBlock(NewBB, idom);
-
-    // Additionally, NewBB replaces OldPred as the immediate dominator of blocks
-    Function *F = Header->getParent();
-    for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
-      if (DT->getIDomBlock(I) == OldPred) {
-        DT->changeImmediateDominator(I, NewBB);
-      }
-  }
 
   // Okay, now we need to adjust the PHI nodes and any branches from within the
   // region to go to the new header block instead of the old header block.

lib/Transforms/Utils/LoopSimplify.cpp

@@ -61,7 +61,7 @@ namespace {
     // this is null.
     AliasAnalysis *AA;
     LoopInfo *LI;
-
+    DominatorTree *DT;
     virtual bool runOnFunction(Function &F);
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
@@ -85,9 +85,6 @@ namespace {
     void PlaceSplitBlockCarefully(BasicBlock *NewBB,
                                   std::vector<BasicBlock*> &SplitPreds,
                                   Loop *L);
-      
-    void UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
-                                         std::vector<BasicBlock*> &PredBlocks);
   };
 
   char LoopSimplify::ID = 0;
@@ -106,6 +103,7 @@ bool LoopSimplify::runOnFunction(Function &F) {
   bool Changed = false;
   LI = &getAnalysis<LoopInfo>();
   AA = getAnalysisToUpdate<AliasAnalysis>();
+  DT = &getAnalysis<DominatorTree>();
 
   // Check to see that no blocks (other than the header) in loops have
   // predecessors that are not in loops.  This is not valid for natural loops,
@@ -341,6 +339,7 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
       PN->addIncoming(Constant::getNullValue(PN->getType()), NewBB);
     }
   }
+
   return NewBB;
 }
 
@@ -371,8 +370,10 @@ void LoopSimplify::InsertPreheaderForLoop(Loop *L) {
   if (Loop *Parent = L->getParentLoop())
     Parent->addBasicBlockToLoop(NewBB, *LI);
 
-  UpdateDomInfoForRevectoredPreds(NewBB, OutsideBlocks);
+  DT->splitBlock(NewBB);
-  
+  if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
+    DF->splitBlock(NewBB);
+
   // Make sure that NewBB is put someplace intelligent, which doesn't mess up
   // code layout too horribly.
   PlaceSplitBlockCarefully(NewBB, OutsideBlocks, L);
@@ -401,8 +402,11 @@ BasicBlock *LoopSimplify::RewriteLoopExitBlock(Loop *L, BasicBlock *Exit) {
   if (SuccLoop)
     SuccLoop->addBasicBlockToLoop(NewBB, *LI);
 
-  // Update dominator information (set, immdom, domtree, and domfrontier)
+  // Update Dominator Information
-  UpdateDomInfoForRevectoredPreds(NewBB, LoopBlocks);
+  DT->splitBlock(NewBB);
+  if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
+    DF->splitBlock(NewBB);
+
   return NewBB;
 }
 
@@ -507,7 +511,6 @@ void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
 /// created.
 ///
 Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
-  DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
   PHINode *PN = FindPHIToPartitionLoops(L, DT, AA);
   if (PN == 0) return 0;  // No known way to partition.
 
@@ -523,8 +526,10 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
   BasicBlock *Header = L->getHeader();
   BasicBlock *NewBB = SplitBlockPredecessors(Header, ".outer", OuterLoopPreds);
 
-  // Update dominator information (set, immdom, domtree, and domfrontier)
+  // Update dominator information
-  UpdateDomInfoForRevectoredPreds(NewBB, OuterLoopPreds);
+  DT->splitBlock(NewBB);
+  if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
+    DF->splitBlock(NewBB);
 
   // Make sure that NewBB is put someplace intelligent, which doesn't mess up
   // code layout too horribly.
@@ -677,184 +682,10 @@ void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L) {
   // loop and all parent loops.
   L->addBasicBlockToLoop(BEBlock, *LI);
 
-  // Update dominator information (set, immdom, domtree, and domfrontier)
+  // Update dominator information
-  UpdateDomInfoForRevectoredPreds(BEBlock, BackedgeBlocks);
+  DT->splitBlock(BEBlock);
-}
+  if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
-
+    DF->splitBlock(BEBlock);
-// Returns true if BasicBlock A dominates at least one block in vector B
-// Helper function for UpdateDomInfoForRevectoredPreds
-static bool BlockDominatesAny(BasicBlock* A, const std::vector<BasicBlock*>& B,
-                              DominatorTree &DT) {
-  for (std::vector<BasicBlock*>::const_iterator BI = B.begin(), BE = B.end();
-       BI != BE; ++BI) {
-    if (DT.dominates(A, *BI))
-      return true;
-  }
-  return false;
-}
-
-/// UpdateDomInfoForRevectoredPreds - This method is used to update
-/// dominator trees and dominance frontiers after a new block has
-/// been added to the CFG.
-///
-/// This only supports the case when an existing block (known as "NewBBSucc"),
-/// had some of its predecessors factored into a new basic block.  This
-/// transformation inserts a new basic block ("NewBB"), with a single
-/// unconditional branch to NewBBSucc, and moves some predecessors of
-/// "NewBBSucc" to now branch to NewBB.  These predecessors are listed in
-/// PredBlocks, even though they are the same as
-/// pred_begin(NewBB)/pred_end(NewBB).
-///
-void LoopSimplify::UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
-                                         std::vector<BasicBlock*> &PredBlocks) {
-  assert(!PredBlocks.empty() && "No predblocks??");
-  assert(NewBB->getTerminator()->getNumSuccessors() == 1
-         && "NewBB should have a single successor!");
-  BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
-  DominatorTree &DT = getAnalysis<DominatorTree>();
-
-  // The newly inserted basic block will dominate existing basic blocks iff the
-  // PredBlocks dominate all of the non-pred blocks.  If all predblocks dominate
-  // the non-pred blocks, then they all must be the same block!
-  //
-  bool NewBBDominatesNewBBSucc = true;
-  {
-    BasicBlock *OnePred = PredBlocks[0];
-    unsigned i = 1, e = PredBlocks.size();
-    for (i = 1; !DT.isReachableFromEntry(OnePred); ++i) {
-      assert(i != e && "Didn't find reachable pred?");
-      OnePred = PredBlocks[i];
-    }
-    
-    for (; i != e; ++i)
-      if (PredBlocks[i] != OnePred && DT.isReachableFromEntry(OnePred)){
-        NewBBDominatesNewBBSucc = false;
-        break;
-      }
-
-    if (NewBBDominatesNewBBSucc)
-      for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
-           PI != E; ++PI)
-        if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
-          NewBBDominatesNewBBSucc = false;
-          break;
-        }
-  }
-
-  // The other scenario where the new block can dominate its successors are when
-  // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
-  // already.
-  if (!NewBBDominatesNewBBSucc) {
-    NewBBDominatesNewBBSucc = true;
-    for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
-         PI != E; ++PI)
-      if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
-        NewBBDominatesNewBBSucc = false;
-        break;
-      }
-  }
-
-
-  // Update DominatorTree information if it is active.
-
-  // Find NewBB's immediate dominator and create new dominator tree node for NewBB.
-  BasicBlock *NewBBIDom = 0;
-  unsigned i = 0;
-  for (i = 0; i < PredBlocks.size(); ++i)
-    if (DT.isReachableFromEntry(PredBlocks[i])) {
-      NewBBIDom = PredBlocks[i];
-      break;
-    }
-  assert(i != PredBlocks.size() && "No reachable preds?");
-  for (i = i + 1; i < PredBlocks.size(); ++i) {
-    if (DT.isReachableFromEntry(PredBlocks[i]))
-      NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
-  }
-  assert(NewBBIDom && "No immediate dominator found??");
-  
-  // Create the new dominator tree node... and set the idom of NewBB.
-  DomTreeNode *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
-  
-  // If NewBB strictly dominates other blocks, then it is now the immediate
-  // dominator of NewBBSucc.  Update the dominator tree as appropriate.
-  if (NewBBDominatesNewBBSucc) {
-    DomTreeNode *NewBBSuccNode = DT.getNode(NewBBSucc);
-    DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
-  }
-
-  // Update dominance frontier information...
-  if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
-    // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
-    // DF(PredBlocks[0]) without the stuff that the new block does not dominate
-    // a predecessor of.
-    if (NewBBDominatesNewBBSucc) {
-      DominanceFrontier::iterator DFI = DF->find(PredBlocks[0]);
-      if (DFI != DF->end()) {
-        DominanceFrontier::DomSetType Set = DFI->second;
-        // Filter out stuff in Set that we do not dominate a predecessor of.
-        for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
-               E = Set.end(); SetI != E;) {
-          bool DominatesPred = false;
-          for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
-               PI != E; ++PI)
-            if (DT.dominates(NewBB, *PI))
-              DominatesPred = true;
-          if (!DominatesPred)
-            Set.erase(SetI++);
-          else
-            ++SetI;
-        }
-
-        DF->addBasicBlock(NewBB, Set);
-      }
-
-    } else {
-      // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
-      // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
-      // NewBBSucc)).  NewBBSucc is the single successor of NewBB.
-      DominanceFrontier::DomSetType NewDFSet;
-      NewDFSet.insert(NewBBSucc);
-      DF->addBasicBlock(NewBB, NewDFSet);
-    }
-
-    // Now we must loop over all of the dominance frontiers in the function,
-    // replacing occurrences of NewBBSucc with NewBB in some cases.  All
-    // blocks that dominate a block in PredBlocks and contained NewBBSucc in
-    // their dominance frontier must be updated to contain NewBB instead.
-    //
-    for (Function::iterator FI = NewBB->getParent()->begin(),
-         FE = NewBB->getParent()->end(); FI != FE; ++FI) {
-      DominanceFrontier::iterator DFI = DF->find(FI);
-      if (DFI == DF->end()) continue;  // unreachable block.
-      
-      // Only consider dominators of NewBBSucc
-      if (!DFI->second.count(NewBBSucc)) continue;
-      
-      if (BlockDominatesAny(FI, PredBlocks, DT)) {
-        // If NewBBSucc should not stay in our dominator frontier, remove it.
-        // We remove it unless there is a predecessor of NewBBSucc that we
-        // dominate, but we don't strictly dominate NewBBSucc.
-        bool ShouldRemove = true;
-        if ((BasicBlock*)FI == NewBBSucc
-            || !DT.dominates(FI, NewBBSucc)) {
-          // Okay, we know that PredDom does not strictly dominate NewBBSucc.
-          // Check to see if it dominates any predecessors of NewBBSucc.
-          for (pred_iterator PI = pred_begin(NewBBSucc),
-               E = pred_end(NewBBSucc); PI != E; ++PI)
-            if (DT.dominates(FI, *PI)) {
-              ShouldRemove = false;
-              break;
-            }
-          
-          if (ShouldRemove)
-            DF->removeFromFrontier(DFI, NewBBSucc);
-          DF->addToFrontier(DFI, NewBB);
-          
-          break;
-        }
-      }
-    }
-  }
 }
 
 

lib/VMCore/Dominators.cpp

@@ -63,6 +63,89 @@ char DominatorTree::ID = 0;
 static RegisterPass<DominatorTree>
 E("domtree", "Dominator Tree Construction", true);
 
+// NewBB is split and now it has one successor. Update dominator tree to
+// reflect this change.
+void DominatorTree::splitBlock(BasicBlock *NewBB) {
+
+  assert(NewBB->getTerminator()->getNumSuccessors() == 1
+         && "NewBB should have a single successor!");
+  BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
+
+  std::vector<BasicBlock*> PredBlocks;
+  for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
+       PI != PE; ++PI)
+      PredBlocks.push_back(*PI);  
+
+  assert(!PredBlocks.empty() && "No predblocks??");
+
+  // The newly inserted basic block will dominate existing basic blocks iff the
+  // PredBlocks dominate all of the non-pred blocks.  If all predblocks dominate
+  // the non-pred blocks, then they all must be the same block!
+  //
+  bool NewBBDominatesNewBBSucc = true;
+  {
+    BasicBlock *OnePred = PredBlocks[0];
+    unsigned i = 1, e = PredBlocks.size();
+    for (i = 1; !isReachableFromEntry(OnePred); ++i) {
+      assert(i != e && "Didn't find reachable pred?");
+      OnePred = PredBlocks[i];
+    }
+    
+    for (; i != e; ++i)
+      if (PredBlocks[i] != OnePred && isReachableFromEntry(OnePred)){
+        NewBBDominatesNewBBSucc = false;
+        break;
+      }
+
+    if (NewBBDominatesNewBBSucc)
+      for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
+           PI != E; ++PI)
+        if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
+          NewBBDominatesNewBBSucc = false;
+          break;
+        }
+  }
+
+  // The other scenario where the new block can dominate its successors are when
+  // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
+  // already.
+  if (!NewBBDominatesNewBBSucc) {
+    NewBBDominatesNewBBSucc = true;
+    for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
+         PI != E; ++PI)
+      if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
+        NewBBDominatesNewBBSucc = false;
+        break;
+      }
+  }
+
+
+  // Find NewBB's immediate dominator and create new dominator tree node for NewBB.
+  BasicBlock *NewBBIDom = 0;
+  unsigned i = 0;
+  for (i = 0; i < PredBlocks.size(); ++i)
+    if (isReachableFromEntry(PredBlocks[i])) {
+      NewBBIDom = PredBlocks[i];
+      break;
+    }
+  assert(i != PredBlocks.size() && "No reachable preds?");
+  for (i = i + 1; i < PredBlocks.size(); ++i) {
+    if (isReachableFromEntry(PredBlocks[i]))
+      NewBBIDom = findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
+  }
+  assert(NewBBIDom && "No immediate dominator found??");
+  
+  // Create the new dominator tree node... and set the idom of NewBB.
+  DomTreeNode *NewBBNode = addNewBlock(NewBB, NewBBIDom);
+  
+  // If NewBB strictly dominates other blocks, then it is now the immediate
+  // dominator of NewBBSucc.  Update the dominator tree as appropriate.
+  if (NewBBDominatesNewBBSucc) {
+    DomTreeNode *NewBBSuccNode = getNode(NewBBSucc);
+    changeImmediateDominator(NewBBSuccNode, NewBBNode);
+  }
+}
+
 unsigned DominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
                                       unsigned N) {
   // This is more understandable as a recursive algorithm, but we can't use the
@@ -520,6 +603,107 @@ char DominanceFrontier::ID = 0;
 static RegisterPass<DominanceFrontier>
 G("domfrontier", "Dominance Frontier Construction", true);
 
+// NewBB is split and now it has one successor. Update dominace frontier to
+// reflect this change.
+void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
+
+  assert(NewBB->getTerminator()->getNumSuccessors() == 1
+         && "NewBB should have a single successor!");
+  BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
+
+  std::vector<BasicBlock*> PredBlocks;
+  for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
+       PI != PE; ++PI)
+      PredBlocks.push_back(*PI);  
+
+  assert(!PredBlocks.empty() && "No predblocks??");
+
+  DominatorTree &DT = getAnalysis<DominatorTree>();
+  bool NewBBDominatesNewBBSucc = true;
+  if (!DT.dominates(NewBB, NewBBSucc))
+    NewBBDominatesNewBBSucc = false;
+
+  // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
+  // DF(PredBlocks[0]) without the stuff that the new block does not dominate
+  // a predecessor of.
+  if (NewBBDominatesNewBBSucc) {
+    DominanceFrontier::iterator DFI = find(PredBlocks[0]);
+    if (DFI != end()) {
+      DominanceFrontier::DomSetType Set = DFI->second;
+      // Filter out stuff in Set that we do not dominate a predecessor of.
+      for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
+             E = Set.end(); SetI != E;) {
+        bool DominatesPred = false;
+        for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
+             PI != E; ++PI)
+          if (DT.dominates(NewBB, *PI))
+            DominatesPred = true;
+        if (!DominatesPred)
+          Set.erase(SetI++);
+        else
+          ++SetI;
+      }
+      
+      addBasicBlock(NewBB, Set);
+    }
+    
+  } else {
+    // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
+    // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
+    // NewBBSucc)).  NewBBSucc is the single successor of NewBB.
+    DominanceFrontier::DomSetType NewDFSet;
+    NewDFSet.insert(NewBBSucc);
+    addBasicBlock(NewBB, NewDFSet);
+  }
+  
+  // Now we must loop over all of the dominance frontiers in the function,
+  // replacing occurrences of NewBBSucc with NewBB in some cases.  All
+  // blocks that dominate a block in PredBlocks and contained NewBBSucc in
+  // their dominance frontier must be updated to contain NewBB instead.
+  //
+  for (Function::iterator FI = NewBB->getParent()->begin(),
+         FE = NewBB->getParent()->end(); FI != FE; ++FI) {
+    DominanceFrontier::iterator DFI = find(FI);
+    if (DFI == end()) continue;  // unreachable block.
+    
+    // Only consider dominators of NewBBSucc
+    if (!DFI->second.count(NewBBSucc)) continue;
+
+    bool BlockDominatesAny = false;
+    for (std::vector<BasicBlock*>::const_iterator BI = PredBlocks.begin(), 
+           BE = PredBlocks.end(); BI != BE; ++BI) {
+      if (DT.dominates(FI, *BI)) {
+        BlockDominatesAny = true;
+        break;
+      }
+    }
+    
+    if (BlockDominatesAny) {
+      // If NewBBSucc should not stay in our dominator frontier, remove it.
+      // We remove it unless there is a predecessor of NewBBSucc that we
+      // dominate, but we don't strictly dominate NewBBSucc.
+      bool ShouldRemove = true;
+      if ((BasicBlock*)FI == NewBBSucc
+          || !DT.dominates(FI, NewBBSucc)) {
+        // Okay, we know that PredDom does not strictly dominate NewBBSucc.
+        // Check to see if it dominates any predecessors of NewBBSucc.
+        for (pred_iterator PI = pred_begin(NewBBSucc),
+               E = pred_end(NewBBSucc); PI != E; ++PI)
+          if (DT.dominates(FI, *PI)) {
+            ShouldRemove = false;
+            break;
+          }
+        
+        if (ShouldRemove)
+          removeFromFrontier(DFI, NewBBSucc);
+        addToFrontier(DFI, NewBB);
+        
+        break;
+      }
+    }
+  }
+}
+
 namespace {
   class DFCalculateWorkObject {
   public: