Fix an apparent ambiguity compiling on PPC

llvm-svn: 20507
diff --git a/llvm/lib/Bytecode/Writer/Writer.cpp b/llvm/lib/Bytecode/Writer/Writer.cpp
index ad2dbd0..9862391 100644
--- a/llvm/lib/Bytecode/Writer/Writer.cpp
+++ b/llvm/lib/Bytecode/Writer/Writer.cpp
@@ -1071,7 +1071,7 @@
     if (I == End) continue;  // Don't mess with an absent type...
 
     // Write the number of values in this plane
-    output_vbr(PI->second.size());
+    output_vbr((unsigned)PI->second.size());
 
     // Write the slot number of the type for this plane
     Slot = Table.getSlot(PI->first);