Introduce a new temporary MDNode concept. Temporary MDNodes are

not part of the IR, are not uniqued, and may be safely RAUW'd.
This replaces a variety of alternate mechanisms for achieving
the same effect.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111681 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/Metadata.cpp

@@ -20,6 +20,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "SymbolTableListTraitsImpl.h"
+#include "llvm/Support/LeakDetector.h"
 #include "llvm/Support/ValueHandle.h"
 using namespace llvm;
 
@@ -244,6 +245,28 @@ MDNode *MDNode::getIfExists(LLVMContext &Context, Value *const *Vals,
   return getMDNode(Context, Vals, NumVals, FL_Unknown, false);
 }
 
+MDNode *MDNode::getTemporary(LLVMContext &Context, Value *const *Vals,
+                             unsigned NumVals) {
+  MDNode *N = (MDNode *)malloc(sizeof(MDNode)+NumVals*sizeof(MDNodeOperand));
+  N = new (N) MDNode(Context, Vals, NumVals, FL_No);
+  N->setValueSubclassData(N->getSubclassDataFromValue() |
+                          NotUniquedBit);
+  LeakDetector::addGarbageObject(N);
+  return N;
+}
+
+void MDNode::deleteTemporary(MDNode *N) {
+  assert(N->use_empty() && "Temporary MDNode has uses!");
+  assert((N->getSubclassDataFromValue() & NotUniquedBit) &&
+         "Temporary MDNode does not have NotUniquedBit set!");
+  assert((N->getSubclassDataFromValue() & DestroyFlag) == 0 &&
+         "Temporary MDNode does has DestroyFlag set!");
+  N->setValueSubclassData(N->getSubclassDataFromValue() |
+                          DestroyFlag);
+  LeakDetector::removeGarbageObject(N);
+  delete N;
+}
+
 /// getOperand - Return specified operand.
 Value *MDNode::getOperand(unsigned i) const {
   return *getOperandPtr(const_cast<MDNode*>(this), i);