Dang, we were losing the Constant bit on globals.  Fix this


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@885 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bytecode/Writer/Writer.cpp b/lib/Bytecode/Writer/Writer.cpp
index ffe67a3..87fed4d 100644
--- a/lib/Bytecode/Writer/Writer.cpp
+++ b/lib/Bytecode/Writer/Writer.cpp
@@ -123,7 +123,7 @@
 
     // Fields: bit0 = isConstant, bit1 = hasInitializer, bit2+ = slot#
     unsigned oSlot = ((unsigned)Slot << 2) | (GV->hasInitializer() << 1) | 
-                        isa<ConstPoolVal>(GV);
+                        GV->isConstant();
     output_vbr(oSlot, Out);
 
     // If we have an initializer, output it now.