Add explicit keywords.

llvm-svn: 97460
diff --git a/llvm/lib/Target/SystemZ/SystemZMachineFunctionInfo.h b/llvm/lib/Target/SystemZ/SystemZMachineFunctionInfo.h
index e47d419..fd6e330 100644
--- a/llvm/lib/Target/SystemZ/SystemZMachineFunctionInfo.h
+++ b/llvm/lib/Target/SystemZ/SystemZMachineFunctionInfo.h
@@ -33,7 +33,8 @@
 public:
   SystemZMachineFunctionInfo() : CalleeSavedFrameSize(0) {}
 
-  SystemZMachineFunctionInfo(MachineFunction &MF) : CalleeSavedFrameSize(0) {}
+  explicit SystemZMachineFunctionInfo(MachineFunction &MF)
+    : CalleeSavedFrameSize(0) {}
 
   unsigned getCalleeSavedFrameSize() const { return CalleeSavedFrameSize; }
   void setCalleeSavedFrameSize(unsigned bytes) { CalleeSavedFrameSize = bytes; }