Give internal classes hidden visibility.

Worth 100k on a linux/x86_64 Release+Asserts clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190534 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SpillPlacement.h b/lib/CodeGen/SpillPlacement.h
index 105516b..0a90398 100644
--- a/lib/CodeGen/SpillPlacement.h
+++ b/lib/CodeGen/SpillPlacement.h
@@ -39,7 +39,7 @@
 class MachineBasicBlock;
 class MachineLoopInfo;
 
-class SpillPlacement  : public MachineFunctionPass {
+class LLVM_LIBRARY_VISIBILITY SpillPlacement : public MachineFunctionPass {
   struct Node;
   const MachineFunction *MF;
   const EdgeBundles *bundles;