Disallow null as a named metadata operand.

Make MDNode::destroy private.
Fix the one thing that used MDNode::destroy, outside of MDNode itself.

One should never delete or destroy an MDNode explicitly. MDNodes
implicitly go away when there are no references to them (implementation
details aside).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109028 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.html

@@ -949,15 +949,17 @@ define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>]
 <div class="doc_text">
 
 <p>Named metadata is a collection of metadata. <a href="#metadata">Metadata
-   nodes</a> (but not metadata strings) and null are the only valid operands for
+   nodes</a> (but not metadata strings) are the only valid operands for
    a named metadata.</p>
 
 <h5>Syntax:</h5>
 <pre class="doc_code">
-; An unnamed metadata node, which is referenced by the named metadata.
+; Some unnamed metadata nodes, which are referenced by the named metadata.
+!0 = metadata !{metadata !"zero"}
 !1 = metadata !{metadata !"one"}
+!2 = metadata !{metadata !"two"}
 ; A named metadata.
-!name = !{null, !1}
+!name = !{!0, !1, !2}
 </pre>
 
 </div>

include/llvm/Analysis/DebugInfo.h

@@ -304,8 +304,7 @@ namespace llvm {
     void dump() const;
 
     /// replaceAllUsesWith - Replace all uses of debug info referenced by
-    /// this descriptor. After this completes, the current debug info value
-    /// is erased.
+    /// this descriptor.
     void replaceAllUsesWith(DIDescriptor &D);
   };
 

include/llvm/Metadata.h

@@ -149,9 +149,6 @@ public:
   // critical code because it recursively visits all the MDNode's operands.  
   const Function *getFunction() const;
 
-  // destroy - Delete this node.  Only when there are no uses.
-  void destroy();
-
   /// Profile - calculate a unique identifier for this MDNode to collapse
   /// duplicates
   void Profile(FoldingSetNodeID &ID) const;
@@ -162,6 +159,9 @@ public:
     return V->getValueID() == MDNodeVal;
   }
 private:
+  // destroy - Delete this node.  Only when there are no uses.
+  void destroy();
+
   bool isNotUniqued() const { 
     return (getSubclassDataFromValue() & NotUniquedBit) != 0;
   }

lib/Analysis/DebugInfo.cpp

@@ -233,8 +233,7 @@ unsigned DIArray::getNumElements() const {
 }
 
 /// replaceAllUsesWith - Replace all uses of debug info referenced by
-/// this descriptor. After this completes, the current debug info value
-/// is erased.
+/// this descriptor.
 void DIDerivedType::replaceAllUsesWith(DIDescriptor &D) {
   if (!DbgNode)
     return;
@@ -249,7 +248,6 @@ void DIDerivedType::replaceAllUsesWith(DIDescriptor &D) {
     const MDNode *DN = D;
     const Value *V = cast_or_null<Value>(DN);
     Node->replaceAllUsesWith(const_cast<Value*>(V));
-    Node->destroy();
   }
 }
 
@@ -1385,7 +1383,7 @@ static Value *findDbgGlobalDeclare(GlobalVariable *V) {
     return 0;
 
   for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-    DIDescriptor DIG(cast_or_null<MDNode>(NMD->getOperand(i)));
+    DIDescriptor DIG(cast<MDNode>(NMD->getOperand(i)));
     if (!DIG.isGlobalVariable())
       continue;
     if (DIGlobalVariable(DIG).getGlobal() == V)

lib/AsmParser/LLParser.cpp

@@ -546,12 +546,6 @@ bool LLParser::ParseNamedMetadata() {
   SmallVector<MDNode *, 8> Elts;
   if (Lex.getKind() != lltok::rbrace)
     do {
-      // Null is a special case since it is typeless.
-      if (EatIfPresent(lltok::kw_null)) {
-        Elts.push_back(0);
-        continue;
-      }
-
       if (ParseToken(lltok::exclaim, "Expected '!' here"))
         return true;
     

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -803,10 +803,6 @@ bool BitcodeReader::ParseMetadata() {
       unsigned Size = Record.size();
       SmallVector<MDNode *, 8> Elts;
       for (unsigned i = 0; i != Size; ++i) {
-        if (Record[i] == ~0U) {
-          Elts.push_back(NULL);
-          continue;
-        }
         MDNode *MD = dyn_cast<MDNode>(MDValueList.getValueFwdRef(Record[i]));
         if (MD == 0)
           return Error("Malformed metadata record");

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -558,12 +558,8 @@ static void WriteModuleMetadata(const ValueEnumerator &VE,
       Record.clear();
 
       // Write named metadata operands.
-      for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-        if (NMD->getOperand(i))
-          Record.push_back(VE.getValueID(NMD->getOperand(i)));
-        else
-          Record.push_back(~0U);
-      }
+      for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
+        Record.push_back(VE.getValueID(NMD->getOperand(i)));
       Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
       Record.clear();
     }

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -2319,7 +2319,7 @@ DwarfDebug::collectVariableInfo(const MachineFunction *MF,
       M->getNamedMetadata(Twine("llvm.dbg.lv.", 
                                 getRealLinkageName(F->getName())))) {
     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-      DIVariable DV(cast_or_null<MDNode>(NMD->getOperand(i)));
+      DIVariable DV(cast<MDNode>(NMD->getOperand(i)));
       if (!DV || !Processed.insert(DV))
         continue;
       DbgScope *Scope = DbgScopeMap.lookup(DV.getContext());
@@ -2783,7 +2783,7 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
             M->getNamedMetadata(Twine("llvm.dbg.lv.", 
                                       getRealLinkageName(FName)))) {
           for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-          DIVariable DV(cast_or_null<MDNode>(NMD->getOperand(i)));
+          DIVariable DV(cast<MDNode>(NMD->getOperand(i)));
           if (!DV || !ProcessedVars.insert(DV))
             continue;
           DbgScope *Scope = AbstractScopes.lookup(DV.getContext());

lib/VMCore/AsmWriter.cpp

@@ -638,10 +638,8 @@ void SlotTracker::processModule() {
          I = TheModule->named_metadata_begin(),
          E = TheModule->named_metadata_end(); I != E; ++I) {
     const NamedMDNode *NMD = I;
-    for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
-      if (MDNode *MD = NMD->getOperand(i))
-        CreateMetadataSlot(MD);
-    }
+    for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
+      CreateMetadataSlot(NMD->getOperand(i));
   }
 
   // Add all the unnamed functions to the table.
@@ -1424,10 +1422,7 @@ void AssemblyWriter::printNamedMDNode(const NamedMDNode *NMD) {
   Out << "!" << NMD->getName() << " = !{";
   for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
     if (i) Out << ", ";
-    if (MDNode *MD = NMD->getOperand(i))
-      Out << '!' << Machine.getMetadataSlot(MD);
-    else
-      Out << "null";
+    Out << '!' << Machine.getMetadataSlot(NMD->getOperand(i));
   }
   Out << "}\n";
 }

lib/VMCore/Metadata.cpp

@@ -389,7 +389,7 @@ unsigned NamedMDNode::getNumOperands() const {
 /// getOperand - Return specified operand.
 MDNode *NamedMDNode::getOperand(unsigned i) const {
   assert(i < getNumOperands() && "Invalid Operand number!");
-  return dyn_cast_or_null<MDNode>(&*getNMDOps(Operands)[i]);
+  return dyn_cast<MDNode>(&*getNMDOps(Operands)[i]);
 }
 
 /// addOperand - Add metadata Operand.

test/Feature/NamedMDNode.ll

@@ -3,7 +3,7 @@
 ;; Simple NamedMDNode
 !0 = metadata !{i32 42}
 !1 = metadata !{metadata !"foo"}
-!llvm.stuff = !{!0, !1, null}
+!llvm.stuff = !{!0, !1}
 
 !samename = !{!0, !1}
 declare void @samename()