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

lib/Transforms/NaCl/ReplacePtrsWithInts.cpp

Index: lib/Transforms/NaCl/ReplacePtrsWithInts.cpp
diff --git a/lib/Transforms/NaCl/ReplacePtrsWithInts.cpp b/lib/Transforms/NaCl/ReplacePtrsWithInts.cpp
index 53f0d1d809e9b89f52d486c10eb67e21c5c33926..68b5fe6d3c5c30529970166ed31786a500ae99ac 100644
--- a/lib/Transforms/NaCl/ReplacePtrsWithInts.cpp
+++ b/lib/Transforms/NaCl/ReplacePtrsWithInts.cpp
@@ -286,6 +286,9 @@ void FunctionConverter::eraseReplacedInstructions() {
 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);