PNaCl: Check we don't crash in -replace-ptrs-with-ints with odd metadata operands.

lib/Transforms/NaCl/ReplacePtrsWithInts.cpp

 //===- ReplacePtrsWithInts.cpp - Convert pointer values to integer values--===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass strips out aggregate pointer types and replaces them with
@@ skipping 268 matching lines @@
   for (SmallVectorImpl<Instruction *>::iterator I = ToErase.begin(),
            E = ToErase.end();
        I != E; ++I) {
     (*I)->eraseFromParent();
   }
 }
 
 static void ConvertMetadataOperand(FunctionConverter *FC,
                                    IntrinsicInst *Call, int Index) {
   MDNode *MD = cast<MDNode>(Call->getArgOperand(Index));
+  if (!isa<MDNode>(MDVal->getMetadata())) {
+    return;
+  }

[JF, 2015/04/22 17:48:29]

MDVal isn't a valid value here.

   if (MD->getNumOperands() != 1)
     return;
   Value *MDArg = MD->getOperand(0);
   if (MDArg && (isa<Argument>(MDArg) || isa<Instruction>(MDArg))) {
     MDArg = FC->convert(MDArg, /* BypassPlaceholder= */ true);
     if (PtrToIntInst *Cast = dyn_cast<PtrToIntInst>(MDArg)) {
       // Unwrapping this is necessary for llvm.dbg.declare to work.
       MDArg = Cast->getPointerOperand();
     }
     SmallVector<Value *, 1> Args;
@@ skipping 321 matching lines @@
     // Delete the now-unused bitcast ConstantExprs that we created so
     // that they don't interfere with StripDeadPrototypes.
     Func->removeDeadConstantUsers();
   }
   return true;
 }
 
 ModulePass *llvm::createReplacePtrsWithIntsPass() {
   return new ReplacePtrsWithInts();
 }