Destroy MDNodes gracefully while deleting llvm context.

llvm-svn: 96609

2 files changed, 18 insertions, 1 deletions

diff --git a/llvm/lib/VMCore/LLVMContextImpl.h b/llvm/lib/VMCore/LLVMContextImpl.h
index 62491d838fb..85bbe4ac9b0 100644
--- a/llvm/lib/VMCore/LLVMContextImpl.h
+++ b/llvm/lib/VMCore/LLVMContextImpl.h
@@ -229,13 +229,23 @@ public:
       if (I->second->use_empty())
         delete I->second;
     }
-    MDNodeSet.clear();
     AlwaysOpaqueTy->dropRef();
     for (OpaqueTypesTy::iterator I = OpaqueTypes.begin(), E = OpaqueTypes.end();
         I != E; ++I) {
       (*I)->AbstractTypeUsers.clear();
       delete *I;
     }
+    // Destroy MDNode operands first.
+    for (FoldingSetIterator<MDNode> I = MDNodeSet.begin(), E = MDNodeSet.end();
+         I != E;) {
+      MDNode *N = &(*I);
+      ++I;
+      N->replaceAllOperandsWithNull();
+    }
+    while (!MDNodeSet.empty()) {
+      MDNode *N = &(*MDNodeSet.begin());
+      N->destroy();
+    }
   }
 };
 
diff --git a/llvm/lib/VMCore/Metadata.cpp b/llvm/lib/VMCore/Metadata.cpp
index 07a5f3c5398..a08c45480b6 100644
--- a/llvm/lib/VMCore/Metadata.cpp
+++ b/llvm/lib/VMCore/Metadata.cpp
@@ -257,6 +257,13 @@ void MDNode::Profile(FoldingSetNodeID &ID) const {
     ID.AddPointer(getOperand(i));
 }
 
+// replaceAllOperandsWithNull - This is used while destroying llvm context to 
+// gracefully delete all nodes. This method replaces all operands with null.
+void MDNode::replaceAllOperandsWithNull() {
+  for (MDNodeOperand *Op = getOperandPtr(this, 0), *E = Op+NumOperands;
+       Op != E; ++Op)
+    replaceOperand(Op, 0);
+}
 
 // Replace value from this node's operand list.
 void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {