Unbreak VC++.

llvm-svn: 36831
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 0d420ff..65da264b 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -808,7 +808,7 @@
   case Instruction::Call: {
     Code = bitc::FUNC_CODE_INST_CALL;
     Vals.push_back((cast<CallInst>(I).getCallingConv() << 1) |
-                   cast<CallInst>(I).isTailCall());
+                   unsigned(cast<CallInst>(I).isTailCall()));
     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // Callee
     
     // Emit value #'s for the fixed parameters.