[CodeGen] Reduce visibility of implementation details

NFC.

llvm-svn: 241164
diff --git a/llvm/lib/CodeGen/InterferenceCache.h b/llvm/lib/CodeGen/InterferenceCache.h
index 6519a80..18aa5c7 100644
--- a/llvm/lib/CodeGen/InterferenceCache.h
+++ b/llvm/lib/CodeGen/InterferenceCache.h
@@ -21,7 +21,7 @@
 
 class LiveIntervals;
 
-class InterferenceCache {
+class LLVM_LIBRARY_VISIBILITY InterferenceCache {
   const TargetRegisterInfo *TRI;
   LiveIntervalUnion *LIUArray;
   MachineFunction *MF;