Reapply r97788 to free MDNodes when the LLVMContext is destroyed. It

bootstraps llvm-gcc this time.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97918 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 8 deletions

diff --git a/lib/VMCore/LLVMContextImpl.h b/lib/VMCore/LLVMContextImpl.h
index 9887f28821..9978f40ed0 100644
--- a/lib/VMCore/LLVMContextImpl.h
+++ b/lib/VMCore/LLVMContextImpl.h
@@ -105,6 +105,11 @@ public:
   StringMap<MDString*> MDStringCache;
   
   FoldingSet<MDNode> MDNodeSet;
+  // MDNodes may be uniqued or not uniqued.  When they're not uniqued, they
+  // aren't in the MDNodeSet, but they're still shared between objects, so no
+  // one object can destroy them.  This set allows us to at least destroy them
+  // on Context destruction.
+  SmallPtrSet<MDNode*, 1> NonUniquedMDNodes;
   
   ConstantUniqueMap<char, Type, ConstantAggregateZero> AggZeroConstants;
 
@@ -235,17 +240,21 @@ public:
       (*I)->AbstractTypeUsers.clear();
       delete *I;
     }
-    // Destroy MDNode operands first.
+    // Destroy MDNodes.  ~MDNode can move and remove nodes between the MDNodeSet
+    // and the NonUniquedMDNodes sets, so copy the values out first.
+    SmallVector<MDNode*, 8> MDNodes;
+    MDNodes.reserve(MDNodeSet.size() + NonUniquedMDNodes.size());
     for (FoldingSetIterator<MDNode> I = MDNodeSet.begin(), E = MDNodeSet.end();
-         I != E;) {
-      MDNode *N = &(*I);
-      ++I;
-      N->replaceAllOperandsWithNull();
+         I != E; ++I) {
+      MDNodes.push_back(&*I);
     }
-    while (!MDNodeSet.empty()) {
-      MDNode *N = &(*MDNodeSet.begin());
-      N->destroy();
+    MDNodes.append(NonUniquedMDNodes.begin(), NonUniquedMDNodes.end());
+    for (SmallVector<MDNode*, 8>::iterator I = MDNodes.begin(),
+           E = MDNodes.end(); I != E; ++I) {
+      (*I)->destroy();
     }
+    assert(MDNodeSet.empty() && NonUniquedMDNodes.empty() &&
+           "Destroying all MDNodes didn't empty the Context's sets.");
     // Destroy MDStrings.
     for (StringMap<MDString*>::iterator I = MDStringCache.begin(),
            E = MDStringCache.end(); I != E; ++I) {