- Change PHINode::removeIncomingValue to delete the phi node if the last

incoming value is removed!

llvm-svn: 4078

lib/VMCore/InstrTypes.cpp

@@ -8,6 +8,7 @@
 #include "llvm/iPHINode.h"
 #include "llvm/Function.h"
 #include "llvm/SymbolTable.h"
+#include "llvm/Constant.h"
 #include "llvm/Type.h"
 #include <algorithm>  // find
 
@@ -41,11 +42,19 @@ void PHINode::addIncoming(Value *D, BasicBlock *BB) {
 
 // removeIncomingValue - Remove an incoming value.  This is useful if a
 // predecessor basic block is deleted.
-Value *PHINode::removeIncomingValue(const BasicBlock *BB) {
+Value *PHINode::removeIncomingValue(const BasicBlock *BB,
+                                    bool DeletePHIIfEmpty) {
   op_iterator Idx = find(Operands.begin(), Operands.end(), (const Value*)BB);
   assert(Idx != Operands.end() && "BB not in PHI node!");
   --Idx;  // Back up to value prior to Basic block
   Value *Removed = *Idx;
   Operands.erase(Idx, Idx+2);  // Erase Value and BasicBlock
+
+  // If the PHI node is dead, because it has zero entries, nuke it now.
+  if (getNumOperands() == 0 && DeletePHIIfEmpty) {
+    // If anyone is using this PHI, make them use a dummy value instead...
+    replaceAllUsesWith(Constant::getNullValue(getType()));
+    getParent()->getInstList().erase(this);
+  }
   return Removed;
 }