Fix SDNode::MorphNodeTo (a function used by by SelectNodeTo) to

properly track dead nodes that are on the original SDNode's operand
list but not the new one, and have no other uses.

llvm-svn: 53201

1 files changed, 50 insertions, 43 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index b9f84080ba8..3f262df713f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -486,42 +486,16 @@ void SelectionDAG::RemoveDeadNodes() {
     if (I->use_empty())
       DeadNodes.push_back(I);
 
-  // Process the worklist, deleting the nodes and adding their uses to the
-  // worklist.
-  while (!DeadNodes.empty()) {
-    SDNode *N = DeadNodes.back();
-    DeadNodes.pop_back();
-    
-    // Take the node out of the appropriate CSE map.
-    RemoveNodeFromCSEMaps(N);
-
-    // Next, brutally remove the operand list.  This is safe to do, as there are
-    // no cycles in the graph.
-    for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); I != E; ++I) {
-      SDNode *Operand = I->getVal();
-      Operand->removeUser(std::distance(N->op_begin(), I), N);
-      
-      // Now that we removed this operand, see if there are no uses of it left.
-      if (Operand->use_empty())
-        DeadNodes.push_back(Operand);
-    }
-    if (N->OperandsNeedDelete) {
-      delete[] N->OperandList;
-    }
-    N->OperandList = 0;
-    N->NumOperands = 0;
-    
-    // Finally, remove N itself.
-    AllNodes.erase(N);
-  }
+  RemoveDeadNodes(DeadNodes);
   
   // If the root changed (e.g. it was a dead load, update the root).
   setRoot(Dummy.getValue());
 }
 
-void SelectionDAG::RemoveDeadNode(SDNode *N, DAGUpdateListener *UpdateListener){
-  SmallVector<SDNode*, 16> DeadNodes;
-  DeadNodes.push_back(N);
+/// RemoveDeadNodes - This method deletes the unreachable nodes in the
+/// given list, and any nodes that become unreachable as a result.
+void SelectionDAG::RemoveDeadNodes(SmallVectorImpl<SDNode *> &DeadNodes,
+                                   DAGUpdateListener *UpdateListener) {
 
   // Process the worklist, deleting the nodes and adding their uses to the
   // worklist.
@@ -537,16 +511,13 @@ void SelectionDAG::RemoveDeadNode(SDNode *N, DAGUpdateListener *UpdateListener){
 
     // Next, brutally remove the operand list.  This is safe to do, as there are
     // no cycles in the graph.
-    unsigned op_num = 0;
     for (SDNode::op_iterator I = N->op_begin(), E = N->op_end(); I != E; ++I) {
       SDNode *Operand = I->getVal();
-      Operand->removeUser(op_num, N);
+      Operand->removeUser(std::distance(N->op_begin(), I), N);
       
       // Now that we removed this operand, see if there are no uses of it left.
       if (Operand->use_empty())
         DeadNodes.push_back(Operand);
-      
-      op_num++;
     }
     if (N->OperandsNeedDelete) {
       delete[] N->OperandList;
@@ -559,6 +530,12 @@ void SelectionDAG::RemoveDeadNode(SDNode *N, DAGUpdateListener *UpdateListener){
   }
 }
 
+void SelectionDAG::RemoveDeadNode(SDNode *N, DAGUpdateListener *UpdateListener){
+  SmallVector<SDNode*, 16> DeadNodes;
+  DeadNodes.push_back(N);
+  RemoveDeadNodes(DeadNodes, UpdateListener);
+}
+
 void SelectionDAG::DeleteNode(SDNode *N) {
   assert(N->use_empty() && "Cannot delete a node that is not dead!");
 
@@ -3681,16 +3658,22 @@ UpdateNodeOperands(SDOperand InN, const SDOperand *Ops, unsigned NumOps) {
 /// opcode, types, and operands to the specified value.  This should only be
 /// used by the SelectionDAG class.
 void SDNode::MorphNodeTo(unsigned Opc, SDVTList L,
-                         const SDOperand *Ops, unsigned NumOps) {
+                         const SDOperand *Ops, unsigned NumOps,
+                         SmallVectorImpl<SDNode *> &DeadNodes) {
   NodeType = Opc;
   ValueList = L.VTs;
   NumValues = L.NumVTs;
   
   // Clear the operands list, updating used nodes to remove this from their
-  // use list.
-  for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
-    I->getVal()->removeUser(std::distance(op_begin(), I), this);
-  
+  // use list.  Keep track of any operands that become dead as a result.
+  SmallPtrSet<SDNode*, 16> DeadNodeSet;
+  for (op_iterator I = op_begin(), E = op_end(); I != E; ++I) {
+    SDNode *N = I->getVal();
+    N->removeUser(std::distance(op_begin(), I), this);
+    if (N->use_empty())
+      DeadNodeSet.insert(N);
+  }
+
   // If NumOps is larger than the # of operands we currently have, reallocate
   // the operand list.
   if (NumOps > NumOperands) {
@@ -3710,7 +3693,29 @@ void SDNode::MorphNodeTo(unsigned Opc, SDVTList L,
     SDNode *N = OperandList[i].getVal();
     N->addUser(i, this);
     ++N->UsesSize;
+    DeadNodeSet.erase(N);
   }
+
+  // Clean up any nodes that are still dead after adding the uses for the
+  // new operands.
+  for (SmallPtrSet<SDNode *, 16>::iterator I = DeadNodeSet.begin(),
+       E = DeadNodeSet.end(); I != E; ++I)
+    DeadNodes.push_back(*I);
+}
+
+/// DropOperands - Release the operands and set this node to have
+/// zero operands.  This should only be used by HandleSDNode to clear
+/// its operand list.
+void SDNode::DropOperands() {
+  assert(NodeType == ISD::HANDLENODE &&
+         "DropOperands is for HANDLENODE only!");
+
+  // Unlike the code in MorphNodeTo that does this, we don't need to
+  // watch for dead nodes here.
+  for (op_iterator I = op_begin(), E = op_end(); I != E; ++I)
+    I->getVal()->removeUser(std::distance(op_begin(), I), this);
+
+  NumOperands = 0;
 }
 
 /// SelectNodeTo - These are used for target selectors to *mutate* the
@@ -3814,7 +3819,10 @@ SDNode *SelectionDAG::SelectNodeTo(SDNode *N, unsigned TargetOpc,
 
   RemoveNodeFromCSEMaps(N);
 
-  N->MorphNodeTo(ISD::BUILTIN_OP_END+TargetOpc, VTs, Ops, NumOps);
+  SmallVector<SDNode *, 16> DeadNodes;
+  N->MorphNodeTo(ISD::BUILTIN_OP_END+TargetOpc, VTs, Ops, NumOps, DeadNodes);
+  RemoveDeadNodes(DeadNodes);
+
   CSEMap.InsertNode(N, IP);   // Memoize the new node.
   return N;
 }
@@ -4250,8 +4258,7 @@ void StoreSDNode::ANCHOR() {}
 void AtomicSDNode::ANCHOR() {}
 
 HandleSDNode::~HandleSDNode() {
-  SDVTList VTs = { 0, 0 };
-  MorphNodeTo(ISD::HANDLENODE, VTs, 0, 0);  // Drops operand uses.
+  DropOperands();
 }
 
 GlobalAddressSDNode::GlobalAddressSDNode(bool isTarget, const GlobalValue *GA,